Options Méditerranéennes Série B n. 56
Water Saving in Mediterranean Agriculture
&
Future Research Needs
WASAMED Project
(EU contract ICA3-CT-2002-10013)
Proceedings of the International Conference
14-17 February 2007 - Valenzano, (Italy)
Vol. II
Cover: A. Filippetti - “Il Prodigio dell’Acqua”
Opinions, data and facts exposed in this number are under the responsibility of the authors and do
not engage either CIHEAM or the Member-countries.
Les opinions, les données et les faits exposés dans ce numéro sont sous la responsabilité des auteurs
et n'engagent ni le CIHEAM, ni les pays membres.
CIHEAM
Centre International de Hautes Etudes Agronomiques Méditerranéennes
Options
méditerranéennes
Directeur de la publication: Bertrand Hervieu
Water Saving in Mediterranean Agriculture
&
Future Research Needs
WASAMED Project
(EU contract ICA3-CT-2002-10013)
Proceedings of the International Conference
14-17 February 2007 - Valenzano, (Italy)
Edited by:
N. Lamaddalena, C. Bogliotti, M. Todorovic, A. Scardigno
2007
This volume of Options Méditerranéennes Series B has been formatted and paged up by
the IAM Bari Editing Board
La maquette et la mise en page de ce volume de Options Méditerranéennes Series B
ont été réalisées à l'Atelier d'Edition de l'IAM Bari
Copy number : 250
Printed by Ideaprint - Bari, Italy
tel. +39 080 542 45 87 e-mail: [email protected]
Water Saving in Mediterranean Agriculture
&
Future Research Needs
WASAMED Project
(EU contract ICA3-CT-2002-10013)
Proceedings of the International Conference
14-17 February 2007 - Valenzano, (Italy)
Edited by:
N. Lamaddalena, C. Bogliotti, M. Todorovic, A. Scardigno
Bari : CIHEAM
(Centre International de Hautes Etudes Agronomiques Méditerranéennes)
Vol. I, p. 451; Vol. II, p. 336; Vol. III, p. 351
Options Méditerranéennes, Série B : N. 56
ISSN : 1016-1228
ISBN : 2-85352-354-3
© CIHEAM, 2007
Reproduction partielle ou totale interdite
sans l'autorisation
d'«Options Méditerranéennes»
Reproduction in whole or in part is not
permitted without the consent of
«Options Méditerranéennes»
CONTENTS
Page
VOLUME I
FOREWORD
27
INTRODUCTION
31
SESSION 1: Water Use Efficiency and Water Productivity
35
A QUANTITATIVE FRAMEWORK FOR THE SYSTEMATIC
ANALYSIS OF POTENTIAL WATER SAVINGS IN AGRICULTURE
T. C. Hsiao, P. Steduto and E. Fereres
37
ASSESSING THE SIMDualKc MODEL FOR IRRIGATION
SCHEDULING SIMULATION IN MEDITERRANEAN
ENVIRONMENTS
J. Rolim, P. Godinho, B. Sequeira, P. Paredes and L.S. Pereira
49
LEMON EVAPOTRANSPIRATION AND YIELD UNDER WATER
DEFICIT IN JORDAN VALLEY
M. Shatanawi, J. Al-Bakri and A. A. Suleiman
63
WATER REQUIREMENTS OF INDIVIDUAL OLIVE TREES IN
RELATION TO CANOPYAND ROOT DEVELOPMENT
M. M. Masmoudi, C. Masmoudi-Charfi ,
I. Mahjoub and N. Ben Mechlia
73
PERFORMANCE OF ‘GOLDEN DELICIOUS’ APPLES GROWN IN
A SEMI-ARID REGION UNDER PARTIAL ROOTZONE DRYING
J. A. Zegbe, A. Serna and Á. G. Bravo
81
MEASUREMENTS OF SAP FLOW FOR APPLE TREES IN RELATION
TO CLIMATIC AND WATERING CONDITIONS
Z. Nasr and N. Ben Mechlia
91
7
Page
REDUCING AGRICULTRUAL WATER DEMAND IN LIBYA
THROUGH THE IMPROVEMENT OF THE WATER USE
EFFICIENCY AND THE CROP WATER PRODUCTIVITY
S. A. Alghariani
99
WATER PRODUCTIVITY ANALYSIS OF SOME IRRIGATED CROPS
IN IRAN
A. Montazar, and H. Rosari
109
SPATIAL SIMULATION OF WATER USE EFFICIENCY IN A
MEDITERRANEAN ENVIRONMENT,
M. Rinaldi and R. Ubaldo
121
IMPROVING WATER USE EFFICIENCY OF FIELD CROPS
THROUGH REGULATED DEFICIT IRRIGATION
K. Karaa, F. Karam and N.R Tarabey
143
DEFICIT IRRIGATION OF SUNFLOWER UNDER
MEDITERRANEAN ENVIRONMENTAL CONDITIONS
M. Todorovic, R. Albrizio and Lj. Zivotic
153
RELATIONSHIP OF WATER USE WITH BIOPHYSICAL AND YIELD
PARAMETERS UNDER VARIOUS IRRIGATION LEVELS IN
RAPESEED CULTIVARS
B. Delkhosh
169
EFFICIENCE DE L’UTILISATION DE L’EAU CHEZ LE BLE ET L’ORGE
SOUS DIFFERENTS REGIMES HYDRIQUES ET DE FERTILISATION
AZOTEE, DANS DES CONDITIONS SUBHUMIDES DE TUNISIE
H. J. Mellouli, M. Ben Naceur, M. El Felah, M. S. El Gharbi,
M. Kaabia, H. Nahdi, G. A. Slafer and M. Karrou
179
CHART FOR MONITORING WHEAT IRRIGATION IN REAL TIME
M. Jabloun and A. Sahli
8
191
Page
PARTITIONING ENERGY FLUXES BETWEEN CANOPY AND SOIL
SURFACE UNDER SPARSE MAIZE DURING WET AND DRY
PERIODS
T.A. Zeggaf , H. Anyoji, S. Takeuchi and T. Yano
201
PLANT - SOIL WATER DYNAMICS OF ALTERNATE FURROW AND
REGULATED DEFICIT IRRIGATION FOR TWO LEGUME CROPS IN
THE FERGANA VALLEY, UZBEKISTAN
H. Webber, C. Madramootoo, M. Bourgault, M. Horst,
G. Stulina and D. Smith
213
LEGUME PRODUCTION AND IRRIGATION STRATEGIES IN THE
ARAL SEA BASIN:YIELD, YIELD COMPONENTS AND WATER
RELATIONS OF COMMON BEAN (PHASEOLUS VULGARIS) AND
GREEN GRAM (VIGNA RADIATA (L.) WILCZEK)
M. Bourgault, C. A. Madramootoo, H. A. Webber,
M. G. Horst, G. Stulina and D. L. Smith
223
IRRIGATION WATER SAVING VIA SCHEDULING IRRIGATION OF
SNAP BEAN AND DIRECTION OF SOIL WATER MOVEMENT
UNDER DRIP IRRIGATION SYSTEM,
R.W. El Gendy, A.M. Gadalla, A. Hamdy,
M. El Moniem and A. Fahmy
235
IRRIGATION SCHEDULING CALENDARS DEVELOPMENT AND
VALIDATION UNDER ACTUAL FARMERS’ CONDITIONS IN ARID
REGIONS OF TUNISIA
K. Nagaz, M. M. Masmoudi and N. Ben Mechlia
249
EFFECT OF DRIP IRRIGATION REGIMES ON YIELD AND
QUALITY OF FIELD GROWN BELL PEPPER
S. Metin Sezen, A. Yazar and S. Eker
261
DEFICIT IRRIGATION SCHEDULING IN PROCESSING TOMATO
G. Gatta, M.M. Giuliani, M. Monteleone, E. Nardella and A. De Caro
277
9
Page
SESSION 2:
Irrigation System Performance and Management
291
ASSESSING ADAPTIVE CAPACITY OF LARGE IRRIGATION
DISTRICTS TOWARDS CLIMATE CHANGE AND SOCIAL CHANGE
WITH IRRIGATION MANAGEMENT PERFORMANCE MODEL
T. Nagano, K. Hoshikawa, S. Donma, T. Kume, S. Önder,
B. Özekici, R.Kanber and T. Watanabe
293
HIDROGEST, A GIS FRAMEWORK FOR INTEGRATION OF
DECISION SUPPORT TOOLS FOR IMPROVED WATER USE AND
PARTICIPATORY MANAGEMENT IN PRESSURIZED ON-DEMAND
IRRIGATION SYSTEMS
P. Mateus, L- Correia and L. S. Pereira
303
DIAGNOSTIC ANALYSIS FOR THE REHABILITATION OF AN
IRRIGATION SYSTEM IN THE STOLAC MUNICIPALITY
(BOSNIA HERZEGOVINA)
E. Bresci and T. Letterio
319
MEASUREMENT AND EVALUATION OF PERFORMANCE OF
MANAGEMENT-OPERATION AND MAINTENANCE OF IRRIGATION
SCHEMES IN BEFORE-AND-AFTER TURNOVER: A CASE STUDY AT
GREAT MENDERES BASIN, TURKEY
C. Koç, D. Akar and K. Özdemir
329
DESIGN OF REAL-TIME CONTROL ALGORITHM FOR ON-DEMAND
OPERATION OF IRRIGATION CHANNELS
G. M. El-Kassar, Kutija and P. E. O’Connell
341
MEASUREMENT AND IMPROVEMENT OF THE ENERGY EFFICIENCY
AT PUMPING STATIONS
M.A. Moreno-Hidalgo, P.A. Carrión , P. Planells ,
J.F. Ortega and J.M. Tarjuelo
353
11
Page
ENERGY SAVING FOR A PUMPING STATION SERVING AN ONDEMAND IRRIGATION SYSTEM: A STUDY CASE,
F. Barutçu, N.Lamaddalena and U. Fratino
367
WATER SAVING SCENARIOS FOR COTTON UNDER SURFACE
IRRIGATION: ANALYSIS WITH THE DSS SADREG
H. Darouich, J. M. Gonçalves and L. S. Pereira
381
DEPIVOT, A SOFTWARE TOOL FOR IMPROVED WATER USE WITH
CENTER-PIVOT SPRINKLER SYSTEMS
M. I. Valín and L. S. Pereira
397
ANALYSIS OF THE DRY SPELL FOR OPERATION DAM IN THE
NORTH OF TUNISIA
Mathlouthi Majid and Lebdi Fethi
407
MANAGEMENT OF SUB-SURFACE DRIP IRRIGATION SYSTEM AND
WATER SAVING IN GREENHOUSE
A. A. Abou Kheira and Amr H. El-Shafie
419
EFFICIENCY OF FURROW IRRIGATION ON SANDY SOIL
AMENDED WITH BENTONITE IN ARID AND SEMI ARID REGION
M. Benkhelifa, Y. Daoud, M. Belkhodja and D. Tessier
12
439
Page
VOLUME II
SESSION 3:
Use of Non conventional Water Resources in Irrigated Agriculture
31
USE OF NON CONVENTIONAL WATER RESOURCES IN
IRRIGATED AGRICULTURE
F. El-Gamal
33
WATER SAVING POTENTIALITIES THROUGH THE USE OF SALINE
WATER AND THE APPLICATION OF DEFICIT IRRIGATION
A. Hamdy, N. Katerji, M. Mastrorilli and A. Dayyoub
45
IRRIGATION STRATEGIES FOR OPTIMAL USE OF SALINE WATER
IN MEDITERRANEAN AGRICULTURE
G. Crescimanno and P. Garofano
61
EFFECT OF SUPPLEMENTARY SALINE IRRIGATION ON YIELD AND
STOMATAL CONDUCTANCE OF WHEAT UNDER THE
MEDITERRANEAN CLIMATIC CONDITIONS
A. Yazar, A. Hamdy, B. Gencel , M. S. Sezen and M. Koç
73
USE OF SALINE IRRIGATION WATER FOR PRODUCTION OF SOME
LEGUMES AND TUBER PLANTS
A. M. Gadalla A. Hamdy and Y. G. M. Galal
85
SEA WATER STRESS AFFECTS MITOCHONDRIAL PROLINE
OXIDATION BUT NOT ALTERNATIVE OXIDASE ACTIVITY IN
DURUM WHEAT GERMINATING SEEDLINGS
M.N. Laus, Z. Flagella, D. Trono, M. Soccio, N. Di Fonzo and D. Pastore
99
SUBMERGED REVERSE OSMOSIS PLANT (SROP)
D. N. Bapat
109
13
Page
TREATED WASTEWATER SOURCES: ACTIONS TOWARDS
SUSTAINABLE AND SAFELY USE IN THE NEAR EAST AND
ACHIEVING FOOD SECURITY IN WATER-SCARCE POOR RURAL
COMMUNITIES
R. Choukr-Allah
115
PLANNING FOR WASTEWATER REUSE
F. Fresa, F. Melli, A.F. Piccinni, V. Santandrea and V. Specchio
129
THE ROLE OF SMALL SCALE WASTEWATER TREATMENT IN THE
DEVELOPMENT OF WATER RESOURCES IN WEST BANK OF
PALESATINE
M. Y. Sbeih
149
IRRIGATION OF VEGETABLES AND FLOWERS WITH TREATED
WASTEWATER
I. Papadopoulos, D. Chimonidou, P. Polycarpou and S. Savvides
163
RESPONSE OF DURUM WHEAT (Triticum durum Desf.) CULTIVAR
ACSAD 1107 TO SEWAGE SLUDGE AMENDMENT UNDER SEMI
ARID CLIMATE
L. Tamrabet, H. Bouzerzour, M. Kribaa and M. Makhlouf
173
REUSE OF MEMBRANE FILTERED MUNICIPAL WASTEWATER FOR
IRRIGATING VEGETABLE CROPS
A. Lopez, A. Pollice, G. Laera, A. Lonigro, P. Rubino and R. Passino
181
USE OF SANDS OF THE DUNES LIKE BIOFILTER IN THE
PURIFICATION OF WASTE WATER OF THE TOWN OF OUARGLA
(ALGERIA)
F. Ammour and M. Messahel
191
SALMONELLA TRANSPORT AND PERSISTENCE IN SOIL AND
PLANT IRRIGATED WITH ARTIFICIALLY INOCULATED RECLAIMED
WATER: CLIMATIC EFFECTS
MP. Palacios, P. Lupiola, F. Fernandez-Vera V. Mendoza and MT.Tejedor
14
199
Page
SESSION 4:
Innovative Approaches and Tools for Water Saving
207
A GIS-BASED WATER RESOURCES INFORMATION SYSTEM:
A REGIONAL DSS FOR IWRM
K. Abu-Zeid and O. Elbadawy
209
USE OF THE GENETIC ALGORITHM FOR THE OPTIMAL
OPERATION OF MULTI-RESERVOIRS ON DEMAND IRRIGATION
SYSTEM
O. Gharsallah, I. Nouiri, F. Lebdi and N. Lamaddalena
217
AVAILABILITY AND ACCURACY OF MEDITERRANEAN DATABASES
RELEVANT TO AGRICULTURAL WATER USES
J. Crimi, M. Khawlie, M. Awad, A. Sgobbi and C. Giupponi
229
THE NOSTRUM-DSS GUIDELINES FOR IMPROVED DEVELOPMENT
AND ADOPTION OF DECISION SUPPORT SYSTEMS IN
INTEGRATED WATER RESOURCES MANAGEMENT IN THE
MEDITERRANEAN BASIN
C. Giupponi, Y. Depietri, R. Camera, J. Crimi and A. Sgobbi
239
APPLICATION OF THE NETSYMOD APPROACH IN SUPPORT
OF DECISIONS ABOUT IRRIGATION MANAGEMENT
A. Fassio, C. Giupponi, A. Sgobbi and J. Mysiak
249
MODELS AND DECISION SUPPORT SYSTEMS FOR
PARTICIPATORY DECISION MAKING IN INTEGRATED WATER
RESOURCE MANAGEMENT
A. Sgobbi and C. Giupponi
259
AGENT-BASED MODELLING AND SIMULATION IN THE
IRRIGATION MANAGEMENT SECTOR: APPLICATIONS AND
POTENTIAL
Fani A.Tzima, Ioannis N. Athanasiadis and Pericles A. Mitkas
273
15
Page
PILOTAGE DE L’IRRIGATION PAR LA METHODE
DURAYONNEMENT GLOBAL
H. Bellouch, A. Baroud, M. Taoura et B. Sirat
287
APPORT DES TECHNIQUES GEO-SPATIALES POUR LA
CARACTÉRISATION DE LA QUALITE DES EAUX SOUS-TERRAINES
DES OASIS DE LA VALLÉE DU DRAA - CAS DE LA NAPPE DE
FEZOUATA
H.D. Cherkaoui, R. Moussadek et H. Sahbi
293
A FRAMEWORK FOR IRRIGATION MANAGEMENT DURING
DROUGHT: APPLICATION IN TWO CASE STUDIES IN THE TAGUS
BASIN, SPAIN
M. Moneo and A. Iglesias
305
WATER MANAGEMENT UNDER EXTREME WATER SCARCITY:
SCENARIO ANALYSES FOR THE JORDAN RIVER BASIN, USING
WEAP21
H. Hoff, C. Swartz, D. Yates and K. Tielborger
321
ROSE CULTIVATION IN CYPRUS UNDER TWO IRRIGATION
REGIMES USING LOCAL SUBSTRATES
D. Chimonidou, L. Vassiliou, P. Kerkides and M. Psyhoyiou
16
333
Page
VOLUME III
SESSION 5:
Integrated Water Management: Institutional, Policy, Social,
Economic and Environmental aspects
31
PROBLEMS AND SOLUTIONS FOR WATER USER ASSOCIATIONS
IN THE GEDİZ BASIN
S. Kiymaz, B. Ozekici and A. Hamdy
33
INTEGRATING STRATEGIES FOR AN EFFICIENT WATER
MANAGEMENT UNDER UNCERTAINITY: EMPIRICAL EVIDENCE IN
SPAIN
I. Blanco Gutiérrez and C. Varela Ortega
45
IRRIGATION PRICING POLICY AIMED AT THE ENHANCEMENT OF
WATER SAVING INNOVATION AT FARM LEVEL. A CASE STUDY
G. Gatta, G. Giannoccaro, M. Monteleone, M. Prosperi and G. Zanni
65
DEVELOPMENT OF AN INCOME GENERATING AGRICULTURAL
MANAGEMENT VIA IRRIGATION SYSTEM IMPROVEMENT IN
LOWER SEYHAN PLAIN
S. Donma and Z. Coşkun
83
OPTIMAL WATER PRODUCTIVITY OF IRRIGATION SYSTEMS IN A
SEMI-ARID REGION
A. Montazar, M.H. Nazari Far and E. Mardi
87
ASSESSMENT OF THE SOCIO-ECONOMIC AND AGRICULTURAL
ASPECTS IN WATER RESOURCES USING GIS, A CASE STUDY
FROM EGYPT
K. Maherzi, A. Afify, M. A. Motaleb and A. Hamdy
99
EFFICIENCY GAINS FROM POTENTIAL WATER MARKET IN IRAN:
SAVEH REGION CASE STUDY
G. H. Kiani
113
17
Page
WATER USE LICENSING VERSUS ELECTRICITY POLICY REFORM
TO STOP SEAWATER INTRUSION
S. Zekri
121
EVALUATION OF DIFFERENT TRADITIONAL WATER
MANAGEMENT SYSTEMS IN SEMI-ARID REGIONS
(CASE STUDY FROM IRAN)
M.R. Ghanbarpour, E. Ahmadi and S. Gholami
133
CONTOUR RIDGE EFFICIENCY ON LAND EROSION,
WATER-FILLING AND SILTING UP OF A HILL RESERVOIR
IN A SEMI-ARID REGION IN TUNISIA
N. Baccari, S. Nasri, Boussema M. Rached and J. M. Lamachère
141
SOIL PHYSICAL DEGRADATION OF RANGELANDS
UNDER CONTINUOUS GRAZING AT THE ZACATECAS,
MEXICO HIGHLANDS
F. G. Echavarría, A. Serna, R. Bañuelos, M. J. Flores,
R. Gutiérrez and H. Salinas
151
A METHODOLOGY TO RELATE GROUNDWATER SALINITY
TO IRRIGATION DELIVERY SCHEDULES:
A CASE STUDY IN SOUTHERN ITALY
I. Oueslati, D. Zaccaria, M. Vurro and N. Lamaddalema
163
ASSESSMENT OF VULNERABLE ZONES TO NITRATE POLLUTION:
A STUDY CASE IN THE APULIA REGION
I.Oueslati, M. Vurro, V. Uricchio and N. Lamaddalena
181
ASSESSMENT OF ON-FARM WATER MANAGEMENT FOR
SUSTAINABLE AGRICULTURAL DEVELOPMENT IN NILE DELTA
W. H. El Hassan., F. El Gamal and Y. Kitamura
197
WATER RESOURCES IN SYRIA AND THEIR DEVELOMENT
PROCEDURES
A. Kaisi, Y. Mohammad and Y. Mahrouseh
18
209
Page
AGRICULTURAL WATER SAVING IN GREECE
A. Karamanos, N. Dercas, P. Londra and S. Aggelides
225
WATER RESOURCES OF ALGERIA AVAILABILITY AND NEEDS
M. Messahel and MS. Benhafid
235
SUSTAINABILITY DIMENSIONS OF THE PRACTICAL EXPERIENCE
IN WATER SAVING FOR AGRICULTURE IN PALESTINIAN
AUTHORITY TERRITORIES
B. Dudeen
243
AN ANALYSIS OF LOSSES AND GAINS IN INDUS RIVER SYSTEM
OF PAKISTAN
F. H. Kharal and S. Ali
253
19
Page
SESSION 6 :
Euro-Mediterranean cooperation
263
IDENTIFYING RESEARCH AND DEVELOPMENT TARGETS FOR THE
MANAGEMENT OF LIMITED WATER RESOURCES IN THE
MEDITERRANEAN: BACKGROUND AND BRIEF OUTLINE OF THE
WASAMED CASE
C. Bogliotti and M. Todorovic
265
IRRIQUAL: SUSTAINABLE ORCHARD IRRIGATION FOR
IMPROVING FRUIT QUALITY AND SAFETY
J.J. Alarcón and M. Pérez de Madrid
285
WATNITMED - MANAGEMENT IMPROVEMENTS OF WUE
AND NUE OF MEDITERRANEAN STRATEGIC CROPS
(WHEAT AND BARLEY)
G. A. Slafer, M. Karrou, F. Karam, C. Thabet, H. J. Spiertz,
R. Dahan, J. Foulkes, S. Nogues, P. Peltonen-Sainio,
R. Albrizio, J. Y. Ayad and H. J. Mellouli
291
FARM LEVEL OPTIMAL WATER MANAGEMENT: ASSISTANT FOR
IRRIGATION UNDER DEFICIT (FLOW-AID)
J. Balendonck, C. Stanghellini and J. Hemming
301
AQUASTRESS: MITIGATION OF WATER STRESS THROUGH NEW
APPROACHES TO INTEGRATING MANAGEMENT, TECHNICAL,
ECONOMIC AND INSTITUTIONAL INSTRUMENTS - DEFINITION
OF THE CASE STUDIES
R. Passino, A. Battaglia, D. Assimacopoulos,
S. Apostolaki and P. Katsiardi
313
PROMOTING GENDER MAINSTREAMING IN INTEGRATED WATER
RESOURCES MANAGEMENT THROUGH INFORMATION
COLLECTION AND DISSEMINATION. THE GEWAMED PROJECT,
J. A. Sagardoy Alonso
325
21
Page
ASSESSMENT OF THE ENVIRONMENTAL SUSTAINABILITY OF
IRRIGATED AGRICULTURE IN A LARGE-SCALE SCHEME – A CASE
STUDY
D. Zaccaria, M. Inversi and N. Lamaddalena
337
DEFICIT IRRIGATION AS A MEANS OF REDUCING AGRICULTURAL
WATER USE
E. Fereres, M. Morales and M.A. Soriano
22
347
FOREWORD
In the Southern Mediterranean, as well as in many other arid and semi-arid contexts,
agriculture is one of the major economic driving forces contributing to more than 50%
of the gross income of the region. Agriculture represents the main activity for a large
part of the rural population and constitutes the tissue of social relationships.
Nevertheless, due to unfavourable climatic conditions, agriculture is widely relied on
irrigation and water withdrawal for agricultural use accounts for more than 80% of total
freshwater abstraction.
Most of the renewable water resources in water scarce regions, and particularly in
the Mediterranean, are already fully exploited (or even overexploited in certain areas)
and funds to build important infrastructures are shrinking. Past experience and initiatives
have often proved the non-sustainability of agricultural water management based only
on infrastructure-supply strategy. Hence, water demand management has been affirmed
as the most appropriate long-term vision strategy to cope with the dynamics of supplydemand imbalance. Certainly, agriculture is the main sector in which water saving
opportunities can be pursued and achieved since the agricultural water losses are
estimated at more than 50% of sectorial water withdrawal.
The contribution of agriculture to a more sustainable development is increasingly
pursued at European level (through the integration of sustainability principles of Lisbon
Process in both the EU Water Framework Directive and the Common Agricultural
Policy) as a strategy that could be wisely developed across the Euro-Mediterranean
region. In view of that, the European Commission has been very active in the promotion
of relevant research initiatives in the water sector in third countries through the
International Cooperation dimension of the RTD Framework Programme as well the
launch of the EU Water Initiative specifically addressed to meet the Millennium
Development Goals.
Since the beginning of Nineties, the Mediterranean Agronomic Institute of Bari
(IAMB), part of the International Centre for Advanced Mediterranean Agronomic Studies
(CIHEAM), has been strengthened the networking activities of the relevant
Mediterranean partners on i) Use of Non-conventional Water Resources in irrigation, ii)
Eco-physiology and modelling for Water Use Efficiency, iii) Assessment and
Improvement of Performances of Collective Irrigation Systems. In 1998, a fruitful
collaboration between CIHEAM and the European Commission (DG-RELEX) has been
intensified within the frame of the Regional Action Plan on “Regional co-operation in
agricultural sector on training, promotion of research and communication of scientific
and technical information in the context of economic transition”. This action has
enabled funding to improve and expand the networking activities more towards onground implementation of research findings in many pilot areas in the Southern
Mediterranean countries. Contemporarily, the Mediterranean Agronomic Institute of
23
Bari had carried out a 4-years long cooperation with the World Bank on the
implementation of Participatory Irrigation Management in arid and semi-arid regions of
Mediterranean and surrounding regions.
Thematic Network on “WAter SAving in MEDiterranean agriculture” (WASAMED)
represents a logical continuation of the previous initiatives and it is granted in 2003 by
the International Scientific Cooperation of the Directorate General of Research,
European Commission, within the frame of the 5th Framework Programme. WASAMED
project (ICA3-CT2002-10013; http://wasamed.iamb.it) is coordinated by CIHEAM-Bari
Institute and involves 42 partners from 16 countries including scientific institutions,
decision and policy makers, researchers, end-users, Water User Associations (WUAs)
and NGOs. The project lasts for four years seeking consensus on best options, goals and
indicators for water saving in the region mainly through the exchange of knowledge,
dissemination of information and realization of five Euro-Mediterranean Workshops and
an International Conference at the end of the programme.
This number of “Option Méditerranéennes” consists of three volumes and represents
the proceedings of the final WASAMED event, International Conference on “Water
Saving in Mediterranean Agriculture and Future Research Needs” carried out at IAMBari, in the period 14-17 February 2007. The Proceedings of this Conference intend to
present and integrate reviews, advances and experiences on the different issues and
aspects of agricultural water management and water saving while extending knowledge
exchange from the Euro-Mediterranean region to other international contexts.
In this regard, I believe the WASAMED Network has made every efforts to bring
together all relevant local, regional and international key-actors and scientists to present
and debate scientific contributions and to identify priorities in research and
recommendations for relevant Mediterranean water policies through a multi-stakeholder
discussion platform and a common vision document. Certainly, the best presumption for
a successful discussion represents a sheer number of participants, more than 85 oral
presentations, not only from the Mediterranean region but also from Central Asia Basin,
Far East, and Central and North America, and numerous outstanding speakers. In view
of that I truly deem that this meeting will contribute to the reinforcement of
collaborative and cooperative relationships among the partners from the EuroMediterranean space, CIHEAM and European Union that would generate new initiatives
to develop together in the region.
In conclusion, I would like to express my sincere appreciations and gratitude to the
European Commission INCO Program for its financial support and valuable work in
following the progress of the project. Then, I would like to thank all WASAMED partners
who have supported project coordination along the four years period and contributed
to the successful implementation of the Conference. My deepest thanks go also to all
the authors from 26 countries who have contributed to these three volumes and to the
European Commission (General Directorate Research and General Directorate
Agriculture), UN-Water, ICARDA, the Arab Water Council and the Apulia Regional
Authorities for important keynote speeches. Finally, I would like to thank my colleagues
24
and staff of CIHEAM-IAMB for their help and support during the realization of the
project and in the organisation of this event. I am sure they have made every efforts to
create a comfortable and hospitable working environment at Bari Institute. I hope you
will enjoy the Conference and your stay in Bari.
Cosimo Lacirignola
CIHEAM-IAMB Director
25
INTRODUCTION
In the last decades, an increasing demand for fresh water resources has been posing
a serious threat to environment and sustainable development in the arid and semi-arid
countries world-wide and the competition for the use of such limited resources is
growing dramatically among different sector. Water scarcity is more and more
becoming one of the main restrictive factors of economic growth and social cohesion
and a timely implementation of water policies and strategies that incorporate criteria of
sustainability has become essential. This is particularly true for many Mediterranean
areas where water shortage is among main constraints for agricultural development
either under “rainfed” or “irrigated” conditions.
Prospective of water saving in agriculture ranges from genetics to agronomic options,
from engineering to economic and institutional solutions with a particular regard to the
improvement of water use efficiency, better performance of irrigation systems,
sustainable use of non-conventional waters, strengthening of the participatory
management approach, adoption of appropriate economic tools and introduction of
regular and standardized methods for monitoring and assessment of water resources
availability, quality and consumption. The success of these options depends on the level
of integration of technical, economic, institutional, environmental and cultural
dimensions. In the Mediterranean, for example, water saving is still below expectations
due to the lack of effective regional coordination, communication and dialogue among
all the relevant stakeholders, and the difficulties to achieve a common-shared vision able
to support the formulation of adequate national and regional water saving programmes
and sustainable water policies.
Regardless the type of water saving pathway, the most recent national and regional
directives and on-field experiences have confirmed the integrated efforts in water saving,
supported by national institutions and both regional and international organizations, as
the best management strategy for sustainable development of agricultural sector. In this
regard, the European Water Framework Directive is one of the most ambitious initiatives
to achieve the sustainable use of local, regional and trans-basin waters through the
integration of institutions, citizens and stakeholders in a participatory process of water
governance. Moreover, in the last decade, the European Commission has promoted
relevant research initiatives in the water sector in the Mediterranean region through the
International Cooperation dimension of the RTD Framework Programme and, recently,
launching the EU Water Initiative.
In view of that, WASAMED project (WAter SAving in MEDiterranean agriculture) has
been conceived and implemented with the main objective of establishing a platform for
the effective Mediterranean dialogue on water saving in agriculture and contributing to
a sustainable management of limited water resources in the Mediterranean Region. The
27
WASAMED Thematic Network, coordinated by CIHEAM-Bari Institute, accounts for a
Mediterranean-wide country partnership based on 19 research institutions, 12
governmental agencies and institutions, 10 water user associations and 1 NGO from 16
countries: Algeria, Cyprus, Egypt, Germany, Greece, Italy, Jordan, Lebanon, Malta,
Morocco, Palestine, Portugal, Spain, Syria, Tunisia, Turkey.
In four years of the project, five International Workshops were carried out conveying
more than 320 participants and resulting in more than 120 oral presentations. These
Workshops have been organized respectively on: i) Participatory Water Saving
Management and Water Culture (Sanliurfa, Turkey, December 2003); ii) Irrigation
System Performance (Hammamet, Tunisia, June 2004); iii) Sustainable use of Nonconventional Water Resources (Cairo, Egypt, December 2004); iv) Water Use Efficiency
and Water Productivity (Amman, Jordan, October 2005); v) Harmonization and
Integration of water saving options (Malta, May 2006). The outputs of these events are
synthesized in five technical-scientific proceedings including more than 60 country
reviews and about 60 scientific keynote documents. Moreover, each workshop has
included several technical working groups aimed at defining common criteria, goals and
indicators of water saving in the Mediterranean agriculture. A total number of 15
working groups have been established throughout the five workshops, conveying a
whole of about 150 participants from researcher institutions and universities,
international organizations, governmental agencies and water user associations.
The Conference on “Water saving in Mediterranean agriculture and future research
needs” is the event completing the WASAMED activities.
The Conference aims to bring together all relevant local and regional key-actors and
scientists in order to discuss and identify the priorities in research to support national
and regional strategies on water saving in the Mediterranean region.
Accordingly, the Conference comprehends multi-stakeholder discussion platform as
well as individual presentations of research findings, national reports and regional
comparative studies on the following main themes:
‰
‰
28
state-of-the-art of research and on-ground implementation of water saving
strategies and practices for improvement of:
-
Water Use Efficiency and Water Productivity,
-
Irrigation Systems Performance,
-
Use of Non-conventional Water Resources and
-
Participatory Irrigation Management and Cultural Heritage;
integration and harmonization of water saving approaches at different scales, from
field to irrigation district, watershed, national and regional basin: state-of-the-art
and scaling up effects;
‰
socio-economic, environmental and institutional indicators for sustainable
development of land and water resources and water saving in the Mediterranean
region;
‰
policies and guidelines for conservation of land and water resources and
sustainable water use at national and regional level and
‰
priority actions and innovative tools for water saving in the Mediterranean
irrigated agriculture in spite of local and regional environmental conditions and
expected socio-economic development and climatic changes.
This number of “Option Méditerranéennes” consists of three volumes and includes
87 contributions presented in the Conference. These documents are grouped in six
chapters – sessions (two in each volume). The first chapter is dedicated to the Water
Use Efficiency and Water Productivity in agricultural sectors and consists of 21
contributions going from the country reviews to the results of experimental work related
mainly to deficit irrigation strategies. The second chapter is committed with the Irrigation
Systems Performance and Management and includes 12 papers related to both large
scale and small scale irrigation systems. The use of Non-conventional Water Resources
in Irrigated Agriculture is presented in the third chapter by means on both saline
irrigation practices (7 papers) and application of treated wastewater (8 papers).
Innovative approaches and tools for water saving are presented in fourth chapter by 12
papers that go from the application of recent information technologies and modelling
and decision support tools to the on-ground experiments on rose cultivation by using
local substrates in Cyprus. Fifth chapter is dedicated to Integrated Water Management
considering both institutional, policy, social, economic and environmental aspects. This
chapter consists of 19 contributions that covers a whole spectrum of themes: from
participatory irrigation management to implementation of water pricing policies and
mitigation of environmental problems. The last chapter is devoted to the EuroMediterranean cooperation and includes 8 papers, each of them representing one EU
project actually going on in the Mediterranean region.
We really hope this Conference, stimulating a constructive dialogue among scientists,
relevant stakeholders and international organisations in ad-hoc discussion platforms,
could represent a milestone in the establishment of an open and constructive dialogue
among research, decision making and policy to strengthen a common EuroMediterranean as well International vision of agricultural water management and water
saving in the region.
WASAMED Coordination Team
Nicola Lamaddalena (Project Coordinator)
Claudio Bogliotti (Project Manager)
Mladen Todorovic
Alessandra Scardigno
29
SESSION 3:
Use of Non-conventional Water Resources
in Irrigated Agriculture
USE OF NON CONVENTIONAL WATER RESOURCES
IN IRRIGATED AGRICULTURE
F. El-Gamal
Director, Water Management Research Institute (NWRC),
El-Kanater El-Khayria, Cairo, Egypt . Email : [email protected]
SUMMARY Food security coupled with water scarcity is a cause of serious concern in almost all
developing countries. The present over-use and degradation of water resources and growing
competition of non-agricultural water users are expected to influence the cost and availability of water
for food production. This situation is the root cause to spur special interest in non-conventional water
use as an additional water source, particularly in the irrigated agriculture. However, the use of nonconventional water has a multidisciplinary nature with inter-linkage with environment, health, industry,
agriculture, and water resource policy. In this regard, significant challenges still remain in the areas of
technological, managerial and policy innovation and adaptation, human resources development,
information transfer and social and environmental considerations. Sustainability and success of non
conventional water uses depends on sound implementation and management. During the planning
and management phases, the ecological, social and economic aspects should be considered in order
to assure social and economic viability of any reuse activities. Further research is necessary to
develop general guide lines, setting up a universal strategy and use systemic indicators for assessing,
monitoring and evaluating the sustainability of nonconventional water reuse in the Mediterranean
region. For sustainable and safe use of non conventional water, it is needed to provide the decision
maker and the users with a concrete and very clear answer on how agriculture can make use of non
conventional water resources in a way that is technically sound, economically viable and
environmentally non- degrading.
Key Words: Non conventional water, Drainage water , Water Scarcity , Waste water .
INTRODUCTION
Food security coupled with water security of many of the developing nations is a cause of serious
concern. The natural resources base of land and fresh water per capita has been decreasing with the
fast rate of rise of population. The increased demand of fresh water resources is a global concern, but
for the Mediterranean region and particularly the arid and semi arid region, it becomes a serious
challenge. Accelerated urbanization and industrialization in the Mediterranean are now opposing
extreme pressure on the existing limited and vulnerable water resources. Meanwhile, agriculture
activities are also geared to feed the ever-increasing population. These ambitious development
activities tend to siphon off more and more water. Thus, water demand often exceeds reliable and
exploitable water resources. Such existing imbalance between the limited water supply and the
steadily increasing demand leads to serious conflicts over water and to the degradation of water
quality in most of the countries of the region. Traditionally, the response to water shortage in the
region has been addressed through developing more supplies. However, such traditional approach
will be no longer adequate in the future.
In the developing countries of the region agriculture sector is receiving the lion share of available
water resources, about 80 percent. But the water use efficiency on the farm level is about 50 percent
with losses around 50 percent. Such situation clearly emphasizes the central importance of demand
management, particularly in the agriculture sector. Improving water use efficiency and increasing
water productivity in the irrigation field means greater potentiality for water saving, this being the
central issue to producing more food, fighting poverty, reducing competition for water and ensuring
that there is enough water for the nature. Indeed, there is a high potentiality for water saving in the
agricultural sector in the region. But, this will not be enough to overcome the prevailing water scarcity
and to provide the increasing population with their food and fibre demands.
33
In the region, it is now a must to look for additional water resources that could be sustainable used
in the agriculture sector. It is out of question that water availability for irrigation could be enhanced
through the scientifically based use of non-conventional water.
The uses of various types of non-conventional waters (urban waste waters, industrial waste
waters, brackish waters / saline waters, and drainage waters) have been intensified in most countries
in the region. However, even though its re-use and recycling can appear like a simple and appropriate
technology, in reality it is a complex one. The use of non-conventional water has a multidisciplinary
nature with inter-linkage with environment, health, industry, agriculture, and water resource policy.
To attain full utilization of this vital water source, one has to find sound solutions to several
obstacles still hampering the sustainable and safe use and recycle. In this regard, significant
challenges still remain in the areas of technological, managerial and policy innovation and adaptation,
human resources development, information transfer and social and environmental considerations.
Achieving the goals needs the using of tools available today from the scientific, technological, legal,
political and economic framework. This required concerted efforts supported by national institutions
and both regional and international organizations
TECHNICAL- TECHNOLOGICAL DEVELOPMENTS OF NON-CONVENTIONAL WATER USE
Human use of fresh water has increased more than 35 times over the past three centuries. The
st
experts predict a severe shortage of fresh water in the 21 century. More than 230 million people
living in some 26 countries, 11 of them in Africa and 9 in the near east will suffer from water scarcity
3
(less than 1000 m per person per year).
In the Mediterranean region, particularly the southern and eastern countries, it is quite apparent
that some of those countries are now already under severe water stress, and within the next twenty
years, it is expected that most of the countries of the region will be under absolute water stress. The
available water per capita per year will amount to few hundreds cubic meters (Fig. 1).
1200
Water Supply
1000
m 3/year / inh
Egypt
Morocco
800
600
Algeria
Tunisia
400
200
0
Jordan
Lybia
1985
1990
1995
2000
2005
2010
2015
2020
2025
Year
Fig. 1. Available Fresh Water Per Capita per Year for some Arab countries
For the Mediterranean countries, the non conventional water resources of varying quality including
saline water, drainage water and waste water with varying qualities could play an effective role in
mitigating water scarcity, particularly in the irrigation sectors. This is not only due to the opportunity
they could provide to increase the irrigated area and food production, but, also to the fact that they are
34
a renewable resource and are subjected to continuous increments with time, besides being present in
relatively big quantities as high as nearly 10 percent of the whole available freshwater in the region.
However, the full use of this source for irrigation requires that certain measures be carefully
considered to guarantee its save and sustainable use. The complex interaction of water, soil and crop
in relation to water quality must be well understood. The technology and concepts of using and
managing the non-conventional water in irrigation must be available and well developed for
sustainable production on permanent economic basis. It requires the development of new scientific
practices, new guidelines for use that cope with the prevailing local conditions and new strategies that
facilitate its use on a relatively large scale. Aware of these complex inter-linkages, the sustainable use
and achievements of maximum benefits of non conventional water resources, as a freshwater saving
practice still require further development including planning, investigation, monitoring and
management.
Over the last five decades and more, many research scientists, organizations, institutions and
authorities have advocated the concept of using saline water for irrigation to increase food production.
Considerable amounts of such water are available in various countries of the regions, but, they are
still marginally practiced in irrigation, although they could be successfully used to grow crops without
long term hazardous consequences to crops or soils by applying improved management practice.
Globally, there are around 43 countries, mostly from arid and semi arid regions, are using saline
water for irrigation. The southern Mediterranean countries are practicing saline water in irrigation
purely by necessity rather than by choice. There are successful examples in using non-conventional
water in Irrigation in the Mediterranean regions:
3
In Egypt, about 5 thousand millions m of saline drainage water is used for irrigating about
405,000 ha of land, Table 1. About 75 percent of the drainage water discharged into the sea has a
salinity of less than 3,000 mg/l. The policy of the Government of Egypt is to use drainage water
directly for irrigation if its salinity is less than 700 mg/l; to mix it 1:1 with Nile water (180 to 250 mg/l) if
the concentration is 700 to 1500 mg/l; or 1:2 or 1:3 with Nile water if its concentration is 1,500 to
3,000 mg/l; and to avoid reuse if the salinity of the drainage water exceeds 3,000 mg/l. The annual
3
average volume of available drainage water is about 14 thousand million m . The policy of the ministry
of water resources and irrigation is to make full use of each drop of drainage water by the year 2017,
Table 2. Some large scales projects are currently executed depending on the drainage water as the
main source for irrigation.
Table 1. Reuse of Drainage Water in the Nile Delta during 1995/2003
Year
Eastern Delta
Middle Delta
Western Delta
Total Reuse
Q
EC
Q
EC
Q
EC
Q
EC
1995_96
1745.9
1.89
1814.6
1.79
705.9
1.42
4266.3
1.77
1996_97
1843.2
1.94
1947.9
1.85
642.5
1.31
4433.6
1.81
1997_98
1736.3
1.66
1801.3
1.77
632.4
1.35
4170.1
1.66
1998_99
2126.9
1.48
2168.3
1.52
738.3
1.07
5033.5
1.43
1999_00
1661.8
1.64
1891.4
1.64
1183.6
1.97
4736.8
1.72
2000_01
1830.2
1.57
1958.8
1.76
1058.3
1.92
4847.3
1.72
2001_02
2026.5
1.74
2199.8
1.67
1062.8
1.76
5289.1
1.71
2002_03
2329.3
2.00
2082.4
1.90
875.6
1.76
5287.4
1.92
3
Q: Drainage water Discharge (million m / month)
EC: Drainage water salinity (ds / m)
35
Table 2. Maximum Possible drainage water reuse in Nile Delta (million m3)
Region
Available Drainage Water
Currently Reused
Possible to be reused
Eastern Delta
4083.65
2049.89
1519.02
Middle Delta
5849.14
2007.73
2881.06
Western Delta
3819.15
1123.56
2384.33
Total
13751.94
5181.18
6784.41
The techniques and technologies used in drainage practices are under continuous development on
a well established research base. The development and verification of design drainage criteria for
local conditions are always a concern with the progress of drainage projects to cover new areas. Pilot
areas are designed and implemented for meeting specific changes in the hydrological, soil or
cropping conditions. A dynamic monitoring programme to validate the accuracy of the used criteria is
essential. A modern computerized data base was established to store all relevant collected data and
information. The introduction of an integrated water management approach is the most reliable
procedure for water resources management. Much research work has been and still being carried out
to improve drainage implementation including testing and evaluation of new materials and machinery
and the adoption of new techniques to cope with the local conditions. Equally, emphasis is given to
determine the effects of the re-use of drainage water in irrigation on soils and their productivity for a
range of crops. The environmental impacts are carefully monitored and investigated. Health and
ecological measures are of concern. Social aspects, particularly those related to women as important
users of water are progressively coming to the centre of attention.
Egypt has a policy to use brackish and saline ground water with EC up to 4.5 ds/m and reuse of
drainage ground water with EC 6ds/m with SAR values of 10 to 15 in blending or cyclic mode with
good quality water. The reuse of treated waste water in Egypt started in 1915 in the eastern desert
north east of Cairo. An area of 2500 acres is still under irrigation with waste water, which receives
only primary treatment. With the scarcity of water resources, it is planned to irrigate 150 thousands
acres with treated waste water. All urban waste water projects include facilities for treatment up to the
tertiary level and allow reuse for irrigation. It is estimated that present amount of waste water from
3
major cities and urban area is about 5 billions m /year. Currently, detailed criteria for waste water
reuse in agriculture are under review and preparation. Several pilot programs have started and under
continuous monitoring for some refinements.
In Morocco, there are approximately 7.7 millions hectare of arable lands, of which one million
hectare is actually irrigated and the rest is under rain fed agriculture. However, poor soils physical
conditions, soil salinity, water quality and water stress are considered major limitation for agriculture
development. Rational use of irrigation water, by adopting adequate drip irrigation for high value cash
crops and the use of supplemental irrigation is widely recommended to stabilize and to improve crop
yield. However, with the scarcity of high quality water resources, the use of non- conventional water is
not only a necessity, but also an inevitable option to alleviate the water crisis. The potential of waste
water is shown in Fig.2.
900
Volume
in Mm3
900
800
666
700
600
495
370
500
400
270
300
200
100
0
48
1960
129
1970
1980
1990
2000
2010
Year
Fig. 2. The potential of waste water in Morocco
36
2020
In Agadir region, sand infiltration system is used to treat its waste water to be reused in agriculture
and landscaping. This technology generates high nitrate concentration in the effluent. To face the
salinity problem and to diminish its hazards negative effect on both soil productivity and crop
production, an ample research programme was conducted to establish an appropriate land, water and
crop management under saline irrigation practices. The contribution of the farmers in facing the
salinity problem, through improving the local technologies, cannot be denied.
The knowledge and the experience gained from the research work indicated that the cultivars, the
growing media, the climatic conditions and the salt level of irrigation all affect the final yield. The
experience of Morocco on the use of saline water as an irrigation source clearly indicates the high
potentiality in its use if proper management is developed for specific crops under specific climatic and
soil conditions.
The learned lessons of this experience is that salinity problems could be faced and sustainable
solution could be attained by improving the local technologies the farmers are using by introducing
simple techniques such as stage of planting, selection of cultivars, application of organic manure,
modified soil media. Such simple techniques can have a greater impact on the marketable yield and
quality of the product.
In Algeria, the possibilities of using drainage water with a relatively high salt concentration level
(9 ds/m), SAR value (15.7) and PH of 8 were experimented for the development of salt lands in
Biskard area, southeast of Algeria. The drainage water is an important source for the irrigation of palm
3
trees due to its presence in relatively high quantities exceeding 3 millions m / year. The experience
demonstrated the successful use of drainage water in irrigation through an appropriate irrigation and
leaching scheduling, the addition of soil amendments to avoid soil sodicity, the selection of the palm
trees varieties as well as the irrigation method. The availability of substantial quantities of drainage
water offers the best guarantee for increasing the irrigated area in south of Algeria.
3
3
In Tunisia, the water resources is about 4.5 billion m , of which 2.7 billion m of surface water and
3
1.8 billion m of ground water. It is expected that by year 2020, the domestic and industrial demand
will increase and the available water for agriculture will decrease. In order to overcome this problem
and provide the different sectors with their needs, management, conservation of existing water
resources and development of non-conventional water source have been developed in the field of
water planning and management.
Water and soil salinity is a major constraint for Tunisian agriculture development. Salinity problems
and saline irrigation practices and management have been intensively investigated since 1970. The
experience gained helped in improving the agricultural productivity under saline environment and
setting up the needed guide lines and management techniques to be practiced for save and
sustainable use of saline water in irrigation. The saline Medjerda river water (annual average EC of
3.0 ds/m) has been used to irrigate date palm, sorghum, barley, alfalfa, rye grass and artichoke. The
soils are calcareous (up to 35% CaCO3) heavy clays, which crack when dry.
Waste water reuse is now an essential component of the Tunisian national water resources
strategies and an integral part of overall environmental pollution control and water management
strategy. The waste water reuse policy was launched at the beginning of the 1980. Of the 237 million
3
3
m of waste water discharged annually, 123 million m are treated in 52 treatment plants. Within the
next ten years, this amount is expected to increase by 50%. The policy aims at extending waste water
treatment to all urban areas. The reclaimed waste water is used for irrigation, tourist areas, to irrigate
golf fields and hotel parks. Also, it is used in groundwater recharge and industry.
In Greece, water resources are limited temporally and spatially. The total water consumption, in
3
1990, was 5500 millions m / year. It increases by more than 3 % annually. The major water use is
irrigation with a percentage of 85 %, while domestic use is 11 % and industrial use is about 4 %. The
continued increase of domestic and irrigation water demand can only be met through an integrated
water management scheme that includes the use of all sources including non-conventional waters.
Imbalance of water demand and water supply is often experienced, especially in the coastal and
south eastern regions, due to temporal and spatial variations of the precipitation, the increased water
demand during the summer months, and the difficulty of transporting water due to the mountainous
terrain.
37
Today, there is 350 municipal waste treatment plants can serve about 65 % of the country
population. By reusing the effluent of the existing plants, the reused water, particularly for irrigation of
agricultural land, can be increased by 3.2% of the current total use of freshwater. Thus, the freshwater
that is currently used for irrigation can be saved. This percentage will be substantially increased as
the number of municipal waste treatment plants increase.
In Cyprus, the water scarcity together with the high cost associated with collecting and using the
limited surface rain water for irrigation, has become real constraints. Therefore, alternative water
resources, innovation approaches and new technologies are sought to help solving the problem.
Development of more efficient irrigation methods to save water by better utilization, irrigation with
saline water and reclamation and use of treated municipal waste water, are promising alternative and
innovative approaches. By irrigating with modern irrigation systems, crops are grown successfully and
higher yield is obtained with more saline waters. Experimental data and experience gained suggested
that with proper irrigation and fertilization management, some problems associated with salinity can
be alleviated and occasionally overcome by recurring to crops that are semi- tolerant or tolerant to
salinity. The municipal treated effluent is considered as integrated part of the water resources. It is
assumed that 6% of the cultivated land could be irrigated with municipal treated effluent.
In Jordan, irrigated agriculture consumes 70% of the water available, competing with the rapid
growth of urban and industrial demand. Therefore, saline water is a highly valuable source of water
for irrigation. A major challenge to agriculture is the optimal utilization of brackish water and treated
waste water without causing adverse effects to the environment and at the same time reducing the
amount of fresh water consumption for food production. It is expected that within the next twenty
years, the proportion of non- conventional water will be more than 30% of the total available water
resources. The amount of waste water reused in agriculture in the Jordan valley increased from 20
3
3
million m in 1990 to 42 million m in 2002. It was projected that the reuse of treated waste water will
3
reach 60 million m in 2002. Research findings regarding crop production indicated that for sweet
corn, irrigation with saline water of less than 3.5 ds/m has not caused significant reduction in yield.
The tolerance threshold of soil salinity for relative yield of union varies from 2.43 to 3.6 ds/m. The
drainage water is used for irrigating garlic and onion with careful management.
Brackish water with salinities ranging between 3-11 ds/m is used in the southern Jordan valley.
The experience gained indicated that yield production will differ from to another according to crop salt
tolerance degree. A limiting factor for using brackish water in irrigation is the salt accumulation in the
soil. Therefore, available fresh water for leaching is required. Another solution is the alternation
irrigation, fresh water is used during the sensitive germination and emergence stages until the crop
stand is established, then, irrigation is practiced with saline water.
In Syria, non-conventional water resources are restricted to wastewater (drainage water,
wastewater). Agricultural sector is the largest consumer of conventional and non-conventional water
3
resources. Wastewater amount is about1.2 billion m /year and drainage water is about 1.536 billion
3
m /year. About 29.2% of wastewater is treated, 34.6% is used without treatment, and 36.2% is lost by
discharge to water bodies and valleys. There is a need for establishing treatment plants at small
community level with population (5000 – 10000) to make use of water randomly lost and
contaminating the environment.
There is a lack of crucial local criteria for wastewater use in agriculture. The existing criteria are
merely indicators and preliminary guidelines that can be developed through research activities. There
is a number of environmental, health and economic problems as a result of improper and irrational
use of wastewater are already exist. The essential pre-requisites for the development of safe nonconventional water use lie in the development of institutional and legislative aspects together with
training, information and others.
There is a need to implement some pilot projects for the optimal utilization of conventional water
and giving top priority to the most critical and urgent issues. Also, Supporting scientific and research
centers and institutions for conducting integrated and applied water research and studies is required,
since these centers and institutions are an integral part of the institutional structures responsible for
water resource development and utilization. Training of technical and scientific staff and giving special
consideration to skill upgrading, performance promotion and capacity improvement.
38
In Lebanon, the total available water resources is about 2000 millions m3. The total need, in 2020,
3
is estimated as 2450 millions m . This imbalance will force the country to search for new nonconventional water resources. Waste water is the only suitable source for additional water due to
economic constraint. A master plan for secondary waste water treatment is already elaborated for all
Lebanon and Funded at 70.47 % of total Cost. Between 2005 and 2007, constructed plants are
previewed to serve, until 2015, 88% of the total Lebanese population. The possible collected waste
3
water for treatment, in 2020 is about 250 millions m .
In Turkey, The total available water resources are about 108.66 billion m3, (surface water is about
3
95 billion m and ground water potential is about 13.66 billion m3). The irrigable area is about 4.3
millions hectare (16.6 % of the total irrigable land). It is estimated that, only 8.5 millions hectare can
be irrigated with the present water resources. When all irrigable lands are opened to irrigation, roughly
200 km3 more water is going to be required. Therefore, the solution was to apply the deficit irrigation
programmes including supplemental irrigation and to manage the irrigation systems according to
deficit irrigation approach and to find the new water resources. Unconventional water such as
brackish water (treated waste water, drainage water), shallow ground water and saline water must be
used in near future.
3
The estimated waste water, urban and industrial in 2001, is about 6.7 billions m . The collected
water looks like to complete the little part of the deficiency of water resources. The diluted sea water
seems to be the only way in future. Some experiments have been carried out using saline water for
irrigation. The results from experiments showed that saline water decreases the yield and quality of all
the plants. However, the data and information regarding the use of unconventional water in irrigation,
for a lot of crops grown in the different region of Turkey, were obtained and the studies are being
continued.
SOCIOECONOMIC, ENVIRONMENTAL, INSTITUTIONAL AND POLITICAL ASPECTS FOR NONCONVENTIONAL WATER USE
In most of the Mediterranean countries, the highest portion of the water resources is allocated to
the agriculture, mainly being for irrigation. Non conventional water could relieve as a substitute for
freshwater in irrigation. However, implementation of non-conventional water in irrigation is still a big
challenge due to the complexity of the systems. Planning and management of agricultural reuse
operations need to take into account the socio-economic, institutional, organizational, legal,
regulatory, environmental and technical aspects.
Reusing agricultural drainage water implies an increase of global irrigation efficiency, but also
entails the degradation of the water quality, which affects the soil properties, reduces crop yield and
pollutes the flows returned to the hydrological ecosystem. Also, Reuse of treated and untreated waste
water in irrigation has a high positive potential to environmental relief and social and economic
development. But, reusing waste water without good planning can cause soil quality problems in the
long run, due to building up salinity and heavy metals. It also results in health risk due to the exposure
of farmers, consumers and neighbouring communities to infectious diseases. Therefore, the various
factors of risk must be converted into actions of attenuation and regulations associated to good
practices. The code of good practices of reuse, all as standards of quality, must be developed and
adapted to take into account the specific local conditions.
Agriculture use of non conventional water is more easily accepted and implemented in water-short
areas where irrigation is already practiced. However, skills development, appropriate institutions and
strong extension services are required. Participatory bottom up approach is a cornerstone issue
governing success and/or failure in any reuse irrigation project. Water user associations should be
involved and associated in the planning and management process to ensure the success of the
project. The farmers usually succeed in developing appropriate strategies to make the best use of the
available water in order to maximize the agriculture production.
Finally, sustainability and success of non conventional water uses depends on sound
implementation and management. Poor planning and management might bring high health and
environmental risks, and undesired economic and social results. During the planning and
39
management phases, the ecological, social and economic aspects should be considered in order to
assure social and economic viability of any reuse activities.
GAPS AND ACHIEVEMENTS
Non conventional water is well recognized, in the Mediterranean region, as an alternative source of
irrigation water. Many researchers and scientific institutions have intensively investigated the use of
non conventional water in irrigation and the way to practice and manage it. The information, the
experiences globally gained and the findings of research, all resulted in a notable development on the
use of non conventional water for irrigation and demonstrated its high potentiality for use.
In Italy, Bari institute and many other research institutes and universities are giving the non
conventional water resources practices and management the priority in their research programmes.
Bari institute has intensive research programme on the use of saline water for irrigation. The
experience gained demonstrates that saline water can be used effectively for the production of
selected crops under the right conditions.
In Egypt, intensive research programme together with field experiments have been carried out for
reusing agriculture drainage water. Monitoring and evaluation program are under continuous
developments on a well- established research base. Guidelines for optimal use of drainage water and
setting up strategies for reuse, under the Egyptian conditions have been delivered.
In Morocco and Tunisia, intensive research programme for the use of treated waste water in
irrigation. The finding of the program demonstrates the suitability of reuse of treated waste water in
irrigation when appropriate practices are adopted.
In fact, Important and useful research on the potentials and limitations and hazards of the use of
non conventional water in irrigation were undertaken in relative isolation and no mechanism existed
for coordinating the research work and to utilize effectively the research findings. There is no
universal approach to achieve salinity control in irrigated agriculture; it varies from country to another.
It depends on economic, climatic, social and hydro-geological conditions.
The further research will have to give more attention in the following areas:
Defining policy and strategy on the use of non conventional water in irrigation. To arrive at these
policy and strategy, monitoring programs are required on both water quantities and qualities, as well
as on soils properties;
Integrated management of water of different qualities at farm level, irrigation system and drainage
basins with the explicit goals of increasing agriculture productivity, achieving optimal efficiency of
water use, preventing on- site and off- site degradation and pollution, and sustaining long term
production potential of land and water resources;
Developing and use of mathematical models to relate crop yield to irrigation management under
saline conditions so that empirical models can be reliably applied under a wide variety of field
conditions;
The trade-off between provision of full drainage and drainage volume reduction;
The incorporation of salinity into groundwater flow models to predict the development of not only
water logging but also of soil water salinity. Regional agro-hydro-salinity models should be of
immense value in planning appropriate water management strategies;
Activating the role of policies and institutions in creating demand for technology to ensure the
sustainability of irrigated agriculture in saline environment;
Conducting a comprehensive and coordinated research on potentials and hazards of the use of
non conventional water for irrigation;
40
Establishing working relationship on national, regional and international institutions dealing with the
reuse of non conventional water through the formulation of networks;
Conducting and fostering a comprehensive multi-disciplinary basic and applied research
programme in coordinating fashion on the sustainable use of non conventional water in irrigation and
related problems and obstacles;
Providing facilities for research workers and improving the Institutional Capacity Building;
Incorporation of environmental, Institutional, political and social and economic concerns.
Further research is necessary to develop general guide lines, setting up a universal strategy and
use systemic indicators for assessing, monitoring and evaluating the sustainability of nonconventional
water reuse in the Mediterranean region.
IDENTIFIED PRIORITIES
Non conventional water is a potential source for additional water to be used in irrigation. But, in the
long run, it could seriously affect the crop production; deteriorate the soil productivity and creating
serious environmental problems and health risks. Therefore, during the reuse practices a monitoring
program has to be apply, to identify areas with environmental and health risk as a result of low water
quality. It is the first step towards identifying priority actions that will reduce the health risks. In some
areas short term action may be required to change the practices mechanism, but always the longer
term actions that will reduce the pollution and enhance the reuse potential are still required. The short
term actions can be separated into pollution control actions and protection actions. Pollution control
actions are measures to reduce the non conventional water in areas that are already polluted.
Protection measures are measures to prevent vulnerable areas to be polluted in the future.
In general, to enhance the reuse potential the various factors of risk must be converted to actions
of attention in the following fields:
Planning
•
•
Strengthen the participation of the beneficiaries
Monitoring the quality of non conventional water and reinforce existing regulation
Economic Aspects
•
•
Establish cost-beneficiate analysis
Insure that reuse policy is profitable to the farmers
Organizational Aspects
•
•
Encourage cooperation between different institutions
Establish services contacts between the manufacturing institution and local expertise
institution
Regulation Aspects
•
•
Establish norms and standards for the reuse of non conventional water
Limit the parameters to be monitored
41
Technical and agronomical Aspects
•
•
•
Encourage the drip irrigation system
Optimize the recycling of the nutrient elements included in the water
Develop a strategy for the storage of wastewater
Sanitary Aspects
•
•
•
Develop analytical methods for monitoring persistent contaminants
Improve research techniques for parasites and virus
Develop a methodology and monitoring evaluation system of the impact of the reuse on the
soil, crops and ground water.
Awareness arising
•
•
Establish awareness and education programs for farmers, engineers and technicians
Develop handouts on different aspects of the reuse of non conventional water.
RECOMMENDATIONS
The continued increase of domestic and irrigation water demand can only be met through an
integrated water management scheme that includes the use of all sources of water including nonconventional waters.
Non conventional water such as (brackish water, treated waste water, drainage water, shallow
ground water and saline water) is a potential source in several countries and there is a wide
experience in the Mediterranean region for using it in irrigation as fresh water saving practices.
The complex interaction of water, soil, plant, and climate condition, in relation to water quality
should be considered when using non conventional water in irrigation.
Water management strategies should establish when using non conventional water to minimize
the negative impact on environment and soil productivities. The management strategy should include
efficient use of water (not excessive), sustainable and save use of water, suitable irrigation system
and suitable crop (salt tolerant level matches the salinity level). Efficient water use would minimize
drainage volume and rising water tables which is an environmental problem
Monitoring and evaluation programme should be carried out for water quantities and qualities, as
well as soil’s salinity.
Socio- economic, institutional, political, ecological, health and environmental aspects are to be
taken into consideration by decision- makers when considering using non conventional water
resources for irrigation.
Cost recovery is an essential requisite to ensure the economic sustainability of the use of nonconventional resource.
Supporting scientific and research centres and institutions for conducting integrated and applied
water research and studies since these centres and institutions are an integral part of the institutional
structures responsible for water resource development and utilization
Encouraging the establishment of networks between scientific and research centres on using non
conventional water.
Farmer’s participation in the planning and management is a key for the safe use of non
conventional water in irrigation. Involvement of the farmers in the exercise will close the knowledge
gap between farmers and researchers.
42
Further research is needed on integrated water, crop and land resources management to safely
and sustainable use of non conventional water. Use of mathematical Models should be encouraged to
predict long term salinity impact on soil, plants and the environment.
REFERENCE
Abdel- Azim, R. And Allam, M.N. (2004). Agricultural drainage water reuse in Egypt: Strategic issues
and mitigation measures, Non conventional water use workshop, Cairo, Egypt.
Abu Zeid, M. A., (1997). Egypt’s Water Policy for the 21st Century, IXth World Water Congress of
IWRA – special session on water management under scarcity conditions– the Egyptian
Experience, pp. 1-7, IWRA, Montreal, Canada.
Choukr- Allah, R. (2004). Wastewater Treatment and Reuse in Morocco: Situation and Perspectives,
Non conventional water use workshop, Cairo, Egypt.
Duqqa, M., Shatanawi, M.R. and Mazahrih, N., 2004. Reclaimed Wastewater Treatment and Reuse in
Jordan: Policy and Practices, Non conventional water use workshop, Cairo, Egypt.
Gunther, D. and Ozerol, G. (2004). The Role of Socio-economic Indicators for the assessment of
Wastewater Reuse in the Mediterranean Region, Non conventional water use workshop, Cairo,
Egypt.
Hamdy, A., (2004). Evidence of the Potential Use of Saline Water in Irrigation as Fresh Water Saving
Practice. Non conventional water use workshop, Cairo, Egypt.
Hamdy, A., (2004). Non conventional water resources practices and management, Non conventional
water use workshop, Cairo, Egypt.
Hamdy, A., (2004). Saline irrigation management for a sustainable use, Non conventional water use
workshop, Cairo, Egypt.
Kaisi, M. Yasse and Y. Mahrouseh, (2004). Syrian Arab Republic Country Report, Non conventional
water use workshop, Cairo, Egypt.
Kanber, R., Unlu, M. 2004. Unconventional Irrigation Water Use in Turkey, Non conventional water
use workshop, Cairo, Egypt.
Karaa, K., Karam, F. and Tarabey, N., (2004). Wastewater Treatment and Reuse in Lebanon: Key
Policies and Future Scenarios, Non conventional water use workshop, Cairo, Egypt.
Karamanos, A., Aggelides, S. and Londra, P., (2004). Non-conventional Water use in Greece, Non
conventional water use workshop, Cairo, Egypt.
Mostafa, H., El Gamal, F. and Shalby, A. (2004). Reuse of Low Quality Water in Egypt, Non
conventional water use workshop, Cairo, Egypt.
Quarto, A. and Meroz,Y. (2004). Socio-economic Evaluation of Reuse Project and Pricing Policies for
Wastewater, Non conventional water use workshop, Cairo, Egypt.
43
WATER SAVING POTENTIALITIES THROUGH THE USE OF SALINE WATER AND THE
APPLICATION OF DEFICIT IRRIGATION
*
*
**
***
****
A. Hamdy , N. Katerji , M. Mastrorilli and A. Dayyoub
Professor Emeritus, CIHEAM-Mediterranean Agronomic Institute of Bari, Italy
E.mail: [email protected]
**
INRA, Station de Bioclimatologie, Thiverval-Grignon, France
***
Istituto Sperimentale Agronomico, Bari, Italy
****
Meditarranean Agronomic Institute of Bari, 70010 Valenzano (BA), Italy
SUMMARY- This work was conducted in the greenhouse of the Mediterranean Agronomic Institute of
Bari, aiming to have further information characterizing the response of different durum wheat varieties
to saline irrigation practices (5 and 10ds/m) using different irrigation regimes (100%, 60% and 40% of
Etc). The presented data indicate clearly that the resistance to salt stress, as well as water stress
varies greatly due to the variation in the studied wheat varieties. The findings show also that the
vegetative growth and the grain yield production can tolerate salinity up to 5ds/m, which could be
raised up to 10ds/m resulting in only 10% losses in the grain production. As a result, the apparent
losses in the yield production under deficit irrigation using the saline water is fundamentally attributed
to the water stress conditions. However, deficit irrigation with an appropriate Etc percentage and
irrigation salinity level, is a win-win game as it provides good fresh water saving, acceptable yield
production besides maintaining the soil salinity relatively low.
INTRODUCTION
In the arid and semi arid countries of the Mediterranean, the limited natural resources (land and
water) in addition to the increase of population at a relatively high rate averaging to nearly 3 to 3.5%
annually are putting immense difficulties for most of those developing countries to achieve water
security, food security and environmental sustainability.
In spite of the major effects and the intensive programs carried out in those countries to improve
the water productivity and water use efficiency in all water sectors particularly in the irrigation one,
many countries are still far a way from achieving the goal of food security and water security (Hamdy
and Katerji, 2006).
One of the approaches to be highly recommended is the use of the non-conventional water
resources (saline brackish water and treated municipal waste water) as an additional water resources
for irrigation to overcome the big gap in the cereals production (wheat, barley, maize), which are the
fundamental crops having an important role on food security, fighting the poverty and alleviating
hunger and mal nutrition.
Indeed 60% of cereals are produced under rain-fed agriculture conditions. This production is
relatively low; representing nearly 20% of the one could be produced where irrigation is practiced due
to the prevailing drought conditions at the critical growth stages (flowering and seed formation). Under
such conditions there is a high potentiality to improve cereal production through supplemental
irrigation at the critical growth stage with water having relatively high salt concentration level as most
cereals can tolerate an Eci value lying between 6 ds/m and up to 8 ds/m.
Aware of the importance of the subject for most of arid and semi arid countries in the MENA and
the Mediterranean region, an ample research program started 5 years ago between CIHEAM-IAMBari, ICARDA, INRA France and Agricultural university of Wageningen Holland where a part was
directed to leguminous crops and other to the cereal crops in order to identify and distinguish between
the different crop behaviors concerning their salt tolerance degree, in order to select the appropriate
varieties with a higher salt resistance as a recommended varieties in the region.
45
The studies included in the research program were carried out in drainable Lysimeters and under
controlled conditions in the IAM-Bari greenhouse, and covered the Leguminous crops, Beans, Check
bees, Lentils and the cereals Barely, Durum Wheat and Bread Wheat.
The work presented in this study is a continuation of the research program, but the new in this
research that it is not limited to elucidate just the impact of salinity, but also the effect of drought and
water stress on the different plant growth stages and the yield.
The work presented in this paper is a part of this ample research program which has been carried
out by the Mediterranean Agronomic Institute of Bari with INRA France and ICARDA, where, several
varieties of durum wheat supplied by ICARDA will be under investigation with the main objectives of
Investigating new ways of using the saline water for wheat production under arid and semi-arid
conditions focusing on the salt tolerance degree of the durum wheat varieties, also to elucidate the
behavior of the wheat growing parameters and the production under variable water stress and salt
stress conditions.
MATERIAL AND METHODS
The experiment was conducted in the greenhouse of the Mediterranean Agronomic Institute in
Valenzano, Bari (eastern south coast of Italy), during the year 2005-2006. The greenhouse where the
experiment was conducted is covered with fiberglass sheet and is equipped with aeration and heating
systems, thermostatically controlled to keep the temperature constantly around 20°C.
The experimental trail included two major parts:
¾
The first, where soils were kept during the whole cropping period at field capacity. At
each irrigation the volume of water applied corresponds to the depleted water due to
evapotranspiration.
¾
The second, where the plants were subjected to deficit irrigation receiving at each
irrigation a volume of water equal to 60% and 40% respectively of the water lost due to
evapotranspiration.
Following variables were studied:
•
•
•
Durum wheat: three varieties under investigation (Table 1).
Three salinity levels for irrigation water: fresh water of EC 1ds/m (control treatment) and two
salinity levels 5ds/m and 10ds/m.
Three irrigation regimes:
¾ 100% of evapotranspiration (Trial A)
¾ 60% of evapotranspiration (Trial B).
¾ 40% of evapotranspiration (Trial B).
Table 1. Agronomic characteristics of the investigated cultivars tested in the green house.
Symbol
Name
Origin
Some agronomical characters
V1
CHAM -1
CIMITICARDA
High yielding, good performance under
higher rainfall and supplementary irrigation
V2
HAURANI
Syria
Landrace
V3
HUGLA
ICARDA
Showing salt tolerance
Source: ICARDA, plant breeding sector.
46
Table 2. Chemical analysis of irrigation water
Soluble anions (meq/l)
Soluble cations (meq/l)
EC
(ds/m)
pH
F.W
7.35
3.70
1.20
6.80
7.20
2.80
1.57
0.13
0.70
5.00
7.52
3.25
21.30
15.20
7.10
11.30
21.70
1.16
6.85
10.00
7.41
3.60
46.80
27.11
7.40
22.40
45.71
2
11.84
-
HCO3
--
CL-
SO4
Ca++
Mg++
Na+
K+
SAR
The set-up consists of 162 lysimeter, made of polyvinyl chloride (PVC) with a volume of 0.07m3
(diameters of 0.40m and depth of 0.60m). The bottom of the tube was sealed with plastic tent 0.2
mesh in diameter and placed at the bottom of lysimeter 5 cm of coarse gravel for maintaining the
proper drainage. At the upper part of the lysimeter depth of about 10-cm was left empty for the
accommodation of irrigation water. Three porous cup tubes were located at different depth (15,30 and
45 cm) for soil water sampling by suction. Each lysimeter was placed inside a plastic container to
collect the drainage water. The lysimeter dimensions and its technical specification are illustrated in
Fig.1.
Porous cups
Diameter 40 cm
15cm
Length 60 cm
30cm
45cm
Reservoir
Drainage
Fig. 1. Scheme of Lysimeter with Porous cups and drainage reservoir
Surface irrigation system was used before sowing; the volume of the water needed to bring the
contained soil in the lysimeter to field capacity was calculated using the irrigation indicator lysimeter
line. After sowing each lysimeter was irrigated with a constant volume of water previously calculated.
To ensure a good germination percentage and healthy well developed seedling both stages were
performed using fresh water.
Irrigation with saline water started at the end of seedling establishment stage where seedling
thinning took place. Irrigation was practiced when 30% of the available water was depleted due to
evapotranspiration; this was calculated by the aid of a class A pan installed inside the green house.
To calculate the volume of water to be applied at each irrigation to compensate the water losses due
to the evapotranspiration, one replicate of each treatment “the irrigation guide line “at the irrigation
time was watered, and the excess drained water accumulated in the bottom the plastic container was
47
collected and measured. Differences between the applied water and that sucked from the plastic
container gave the amount of evapotranspiration corresponding to water amount to be applied at each
irrigation practice for the rest of application. Such technique was followed for both fresh water (control
treatment) and the saline irrigation treatment (5 and 10ds/m).
The volume of water calculated under each investigated salinity level was added in full to the
100% irrigation trial, where as for the deficit irrigation trials only 60% and 40% of the volume was
applied
After complete maturity of wheat the plants were harvested and divided into four main parts (roots,
shoots and grains). The plant components were oven dried at 70ºC for 48 hours and the oven dry
weight were recorded for each replicate in the investigated treatment.
Immediately after harvesting, representative soil samples were taken from the upper layer (0-15
cm), from the intermediate layer (15-30 cm) and from the bottom layer (30-45 cm). All soil samples
were analyzed for their salt content.
RESULTS AND DISCUSSION
Water saving potentiality under deficit irrigation and irrigation with saline water
One of the major constraints, most arid and semi arid countries particularly those of the
Mediterranean are now facing for achieving food security and agricultural development, is the chronic
shortage in the available water resources. The increase in population at a relatively high rate, the very
rapid urbanization on one hand, and the economical industrial development on the other hand, all are
now raising up further problems beside the complex one, already are existing.
The policies of most of those countries in achieving both water and food security in their countries
is mainly directed towards improving the management and use of water in agricultural sector which
consumes more than 80% of the available water resources, but with a relatively high water losses and
very poor water use efficiency not exceeding the 50%.
Politically and technically, it is now well recognized that the key in solving the water problems lies
in the agricultural sector through improving crop water productivity, avoiding water losses and
increasing the irrigation water use efficiency. However, this to be achieved necessitates the
implementation of effective programs for water saving in the agricultural sector. Indeed, there are
several approaches for water saving in this sector, among them the deficit irrigation practices and the
use of the non conventional water resources, the saline one as an alternative water source for
irrigation.
The question is what is the potentiality of water saving in the agricultural sector using such
approaches?
The volumes of water applied during the whole cropping period under the different irrigation
regimes using water of different salinity levels in both A and B trials are presented in Table 3.
48
49
V1
V2
V3
Avg.
V1
V2
V3
Avg.
V1
V2
V3
Avg.
FW
FW
SW
(m3/ha)
(m3/ha)
Tot.
3991.0
0.0
3991.0
4344.8
0.0
4344.8
4247.9
0.0
4247.9
4194.6
0.0
4194.6
Trial B - 60% irrigation
FW
FW
SW
(m3/ha)
(m3/ha)
Tot.
2593.2
0.0
2593.2
2868.2
0.0
2868.2
2587.0
0.0
2587.0
2682.8
0.0
2682.8
Trial B - 40% irrigation
FW
FW
SW
(m3/ha)
(m3/ha)
Tot.
2451.9
0.0
2451.9
2157.5
0.0
2157.5
2144.5
0.0
2144.5
2251.3
0.0
2251.3
ET (m3/ha)
Tot.
2288.8
2080.5
2091.6
2153.7
5 ds/m
SW
(m3/ha)
1397.9
1189.5
1200.6
1262.7
FW
(m3/ha)
891.0
891.0
891.0
891.0
FW
(m3/ha)
891.0
891.0
891.0
891.0
SW%
0.6
0.6
0.6
0.6
FW
(m3/ha)
891.0
891.0
891.0
891.0
FW
(m3/ha)
891.0
891.0
891.0
891.0
Tot.
2414.3
2793.5
2483.9
2563.9
5 ds/m
SW
(m3/ha)
1523.3
1902.5
1592.9
1672.9
FW
(m3/ha)
891.0
891.0
891.0
891.0
SW%
0.6
0.7
0.6
0.7
FW
(m3/ha)
891.0
891.0
891.0
891.0
Trial A - 100% irrigation
Irrigation salinity level
5 ds/m
SW
(m3/ha)
Tot.
SW%
2809.2
3700.2
0.8
3250.8
4141.8
0.8
3153.8
4044.8
0.8
3071.3
3962.3
0.8
10 ds/m
SW
(m3/ha)
1326.2
1119.4
1048
1164.5
10 ds/m
SW
(m3/ha)
1497.6
1692
1472.9
1554.2
10 ds/m
SW
(m3/ha)
2596.2
3143.1
2840
2859.7
Table 3. Water volumes m3/ha and saline water as percentages of total water applied during the cropping period
Tot.
2217.2
2010.4
1939.0
2055.5
Tot.
2388.6
2583.0
2363.9
2445.2
Tot.
3487.2
4034.1
3731.0
3750.7
SW%
0.6
0.6
0.5
0.6
SW%
0.6
0.7
0.6
0.6
SW%
0.7
0.8
0.8
0.8
Under the A-Trial, the 100% irrigation with fresh water showed volumes of water 6% and 11%
greater than the ones under the 5 ds/m and the 10 ds/m salinity levels respectively. Here, we would
like to keep in mind that under saline irrigation treatments of the ECi 5 and 10 ds/m in both A and B
trials, the volume of applied water is not totally saline water, as a portion of it was practiced with fresh
water during the germination and the seedling establishment to assure high germination percentage
and healthy seedlings. The volume of fresh water with respect to the total volume applied varied with
the variation of the irrigation regime and accounted to 20, 30 and 40% of the total volume under 100,
60 and 40% irrigation treatments respectively.
Regarding the deficit irrigation treatments, the data shows clearly that for the fresh water and
irrigation with only 60% of the crop evapotranspiration demands resulted in nearly 36% water saving,
whereas, under the 40% irrigation treatment, actually around 46% was the saving in the applied
water.
In this regard, the data also declares that the irrigation with the saline water instead of the fresh
one, starting from the end of the seedling stage till the full maturity, we can have enormous saving in
the fresh water amounting to nearly 80% under the 100% irrigation treatment. The deficit irrigation
and the irrigation with saline water is a win win game: such approach, besides reducing the volume of
water applied by 40 and 60% of that under 100% irrigation, which has its beneficial effect in reducing
the accumulated salts in the active root zone, and consequently diminishing the leaching
requirements. Furthermore, as it substitutes the fresh water for irrigation, it provides from 60% up to
70% saving in fresh water.
Such data evidently indicates that through deficit irrigation and irrigation with saline water, there is
a high potentiality of fresh water saving in the irrigated agriculture.
However, the crucial question: what is the impact of both approaches on the cereals production
and particularly the wheat? The answer to this question can be provided by analyzing the status of the
grains yield of the investigated varieties under both approaches previously mentioned either
individually and/or in combination (Fig.2) and (Table 4).
Water Saving & Losses in the Yield
60
fw
5 ds/m%
50
10 ds/m%
40
Water saving
Lost Yield 30
(% )
20
10
0
60%
40%
water saving
60%
40%
lost yield
Irrigation Regime
Fig. 2. Water saving and the losses in the yield related to deficit irrigation
50
51
V1
V2
V3
Avg.
V1
V2
V3
Avg.
V1
V2
V3
Avg
0.0
0.0
0.0
0.0
SW
(m3/ha)
0.0
0.0
0.0
0.0
SW (m3/ha)
2451.9
2157.5
2144.5
2251.3
FW (m3/ha)
FW
0.0
0.0
0.0
0.0
SW (m3/ha)
Trial B - 40% irrigation
2593.2
2868.2
2587.0
2682.8
FW (m3/ha)
FW
Trial B - 60% irrigation
3991.0
4344.8
4247.9
4194.6
FW
(m3/ha)
FW
Irrigation salinity level
Trial A - 100% irrigation
ET (m3/ha)
2451.9
2157.5
2144.5
2251.3
Tot.
2593.2
2868.2
2587.0
2682.8
Tot.
3991.0
4344.8
4247.9
4194.6
Tot.
3.6
2.9
3.3
3.3
Yield
(ton/ha)
Yield
(ton/ha)
4.3
3.7
4.2
4.1
5.4
5.5
6.3
5.7
Yield
(ton/ha)
891
891
891
891.0
FW
(m3/ha)
5ds/m
FW
(m3/ha)
891
891
891
891.0
5ds/m
891
891
891
891.0
FW
(m3/ha)
5ds/m
1397.8
1189.5
1200.6
1262.7
SW (m3/ha)
1523.3
1902.5
1592.9
1672.9
SW (m3/ha)
2809.2
3250.8
3153.8
3071.3
SW (m3/ha)
2288.8
2080.5
2091.6
2153.7
Tot.
2414.3
2793.5
2483.9
2563.9
Tot.
3700.2
4141.8
4044.8
3962.3
Tot.
3.7
3.2
3.7
3.6
Yield
(ton/ha)
Yield
(ton/ha)
4.3
4.0
4.5
4.2
5.1
5.7
6.3
5.7
Yield
(ton/ha)
Table 4. Water volumes m3/ha and grain yield ton/ha under investigated irrigation treatments
891
891
891
891.0
FW (m3/ha)
10ds/m
891
891
891
891.0
FW (m3/ha)
10ds/m
891
891
891
891.0
FW
(m3/ha)
10ds/m
1326.2
1119.4
1048.0
1164.5
SW (m3/ha)
1497.6
1692.0
1472.9
1554.2
SW (m3/ha)
2596.2
3143.1
2840.0
2859.7
SW (m3/ha)
2217.2
2010.4
1939.0
2055.5
Tot.
2388.6
2583.0
2363.9
2445.2
Tot.
3487.2
4034.1
3731.0
3750.7
Tot.
3.6
3.2
3.7
3.5
Yield
(ton/ha)
Yield
(ton/ha)
4.4
4.2
5.0
4.5
4.9
5.5
5.7
5.4
Yield
(ton/ha)
The presented data indicate that there is a high potentiality of using saline water for irrigation, even
with relatively high salinity level up to 10 ds/m substituting the fresh water. Under the 100% irrigation
treatment, the use of saline water leads to around 80% saving in the fresh water besides the
advantage of having a yield production even with the relatively high salinity level (10 ds/m) of an
average 5.4 tons/ha which is more or less equal to the one obtained under the fresh water irrigation
treatment with only differences 0.3 ton/ha between both irrigation with fresh water and the 100%
saline one.
However, the disadvantage could be related to the increase in the accumulated salts in the active
root zone exceeding the salinity level which the wheat could tolerate, and thereby leaching should be
practiced with fresh water to avoid the deterioration in the soil productivity. However, under such
situation, leaching is normally carried using nearly 15% leaching fraction, which indeed represents a
small portion of fresh water already saved (Van Hoorn et al., 1993; Katerji et al., 2005).
To avoid such raise up in salinity level in the active root zone, as a promising solution is to stop
irrigation with saline water, and to irrigate and leach with fresh water particularly at the sensitive
growth stages (flowering and seed filling).
As shown in Table 4, the use of the 5 ds/m saline water besides saving 80% of the fresh water
showed a grain yield identical to the one where fresh water was practiced. However, we shall be still
faced with a relatively raise up in the salinity level in the active root zone, but with relatively lower
values not exceeding the 5 ds/m and such accumulated salts to be leached will require small fresh
water volumes.
To use saline water successfully for cereals production, the case of wheat, and to avoid losses in
the yield production, it is of paramount importance having a high germination percentage and a well
developed healthy seedlings. Equally the salinity of the irrigation water should be decided in view of
the salt tolerance degree of the growing crop and particularly the sensitive growth stages, and
therefore the selection of the crop variety should be carefully considered (Hamdy, 1990a,b; Hamdy et
al.,1993 and Hamdy, 1994). ).
What we want to add here is that sustainable use of saline water for irrigation implies not only
avoiding losses in the yield production but, equally, keeping the soil at high productivity without any
deterioration, and that is the reason behind having a good quality water source, the fresh water,
beside the saline one to be used at the sensitive growth stages and to satisfy the leaching
requirements (Hamdy, 1996).
Returning again to analysis (Table 4), the data concerning the yield production under deficit
irrigation treatments using fresh water, the presented data indicates that the 60% irrigation treatment
provided 36% fresh water saving besides giving a yield corresponding to 72% of that obtained under
the 100% irrigation with an average 28% yield losses.
Following the same trend under the sever deficit irrigation the 40% irrigation treatment, the saving
3
in the fresh water amounted to 1943 m /ha which is nearly 50% the volume applied under the 100%
irrigation treatment, but, in the mean time the losses in the grain yield were substantially high, nearly
42% of that under full irrigation treatment. Such data indicates clearly that under deficit irrigation, the
lower is the volume of applied water, the greater will be the fresh water saving, and the higher will be
the losses in the yield production.
Now to decide which irrigation regime we have to follow, we have to put on balance the fresh water
saving on the right side, and the yield production on the other side.
Indeed, to take the decision is not any easy one, as it is fundamentally depending on the
availability of the fresh water resources, and the surrounding water problems, the prevailing socio
economic conditions, the water allocation policies, as well as the food security achievements. All
those factors, either separately, or combined together, play an important role on the decision to be
taken which will greatly vary from one country to the other in view of the existing conditions.
52
Some countries will favor deficit irrigation practices, but only at 60% irrigation level accepting the
30% losses in grain production, and having around 40% saving in the fresh water to be allocated to
other sectorial water uses suffering water shortages, and or to increase the irrigated area.
Other countries, those characterized with acute shortages in available water resources could
accept higher water saving and greater losses in the grain yield provided by the severe deficit
irrigation, the 40% treatment and to use such saved water in other sectors of a relatively high return
than the agriculture, like industry and tourism, and by satisfying the needs of wheat through foreign
markets.
Other countries, which have major interest in not only saving more water from the agricultural
sector, but, in the mean time to have a high level of cereals production. Such countries can implement
the deficit irrigation approach but through irrigation with 80% volumes of water which is the
intermediate level between the 100% and the 60% irrigation regimes.
Returning again to Table 3, where deficit irrigation was practiced using saline water of different
salinity levels, the presented data concerning the water saving indicates that through such approach
nearly 40% and 50% of the fresh water are saved under the 60% and 40% irrigation treatments
respectively. On the other hand, concerning the grain yield production under the 60% irrigation
treatments showed values of an average equal or slightly higher than that where 100% irrigation was
practiced. However, under this deficit irrigation level, the yield was subjected to some losses of an
average nearly 20% lower than that obtained under the 100% irrigation regime.
Taking into consideration the salinity level of the irrigation water, it could be seen clearly that: for
both ECi-values of 5 ds/m and 10 ds/m, no significant differences occurred, neither in fresh water
saving percentages, nor in the grain yield production.
Accordingly, the 60% deficit irrigation with the 5 ds/m salinity level is the one to be recommended,
as it has several advantages as compared with the other irrigation treatments in providing a high
water saving percentage in the fresh water, a convenient yield production corresponding to 80% of
that under full irrigation, beside, having an active root zone with a lower ECi-value than that expected
under the 100% irrigation treatment as well as the one with the high salinity level, the 10 ds/m.
Regarding the 40% irrigation regime with saline water (Table 3), the data shows that under both
investigated salinity levels, the 5 and the 10 ds/m, the fresh water saving as well as the yield
production were more or less having the same values. However, under deficit irrigation treatment, the
40% in spite of its advantage in providing more water saving than the 60% treatment, yet, the grain
yield was subjected to further losses nearly with values 20% lower with respect to the 60% irrigation
treatment.
The other point which should be carefully considered is the degree of salt accumulation in the
active root zone and which will require under the 40% irrigation more fresh water for leaching as it is
expected. That salts will be accumulated in excess in the active root zone with respect to the 60%
irrigation treatment, particularly when irrigation is practiced with a higher ECI-values exceeding the 5
ds/m.
Such data again gives the evidence that among the investigated irrigation treatments the 60%
irrigation with saline water of an ECi-value 5 ds/m is the one to be recommended as it satisfies our
major objective in achieving a good fresh water saving, convenient wheat production, and keeping the
soil at high productivity through appropriate leaching management using a relatively low leaching
fraction.
Average EC-values (ds/m) in the active root zoon (0-45cm) at the critical growth stages
At the critical growth stages, water samples representing the soil solution in circulation were
sucked after each irrigation from the different soil layers by the aid of a vacuum pump, through the
porous cups inserted at the depths 7.5, 22.5 and 37.5 cm. (Fig. 1). Average EC values in the different
soil layers for the A trials under the two salinity levels (5 and 10ds/m) for the investigated varieties are
given in Table 5.
53
Table 5. Salt accumulation and its distribution under 100% successive irrigation practices during the
cropping period of the investigated wheat varieties
EC ds/m
Salinity
level
FW
No. of
irrigation
Wheat growing stage
Soil layer depth
0-15
15-30
30-45
avg.
1st
Germination & seedling
0.87
0.85
0.87
0.86
2nd
Early vegetative growth
0.87
0.88
1.00
0.92
3rd
Full vegetative growth
0.84
0.74
0.73
0.77
4th
Flowering
1.20
0.93
0.93
1.02
5th
Seed filling & maturity
1.12
0.95
0.94
1.00
EC ds/m
Salinity
level
5ds/m
No. of
irrigation
Wheat growing stage
Soil layer depth
0-15
15-30
30-45
avg.
1st
Germination & seedling
0.87
0.85
0.87
0.86
2nd
Early vegetative growth
1.54
1.47
1.10
1.37
3rd
Full vegetative growth
5.55
4.76
3.49
4.60
4th
Flowering
7.57
7.57
7.81
7.65
5th
Seed filling & maturity
8.82
8.12
8.85
8.59
EC ds/m
Salinity
level
10ds/m
54
No. of
irrigation
Wheat growing stage
Soil layer depth
0-15
15-30
30-45
avg.
1st
Germination & seedling
0.87
0.85
0.87
0.86
2nd
Early vegetative growth
3.20
2.37
1.17
2.24
3rd
Full vegetative growth
10.81
9.70
6.63
9.05
4th
Flowering
13.73
13.41
14.14
13.76
5th
Seed filling & maturity
16.21
15.85
17.80
16.62
It is worthy to repeat again that both the germination and seedling establishment stages were
developed using only fresh water for irrigation. The end of the seedling stage i.e. the early vegetative
growth 36 days from sowing started the irrigation with the saline water of 5 and 10 ds/m.
Regarding the 100% fresh water irrigation treatment, it could be observed that for the investigated
varieties successive irrigation with fresh water did not result in any increase in the salinity level of the
whole soil profile as well as in the salt distribution within the different soil layers.
Under the 100% irrigation with saline water of an ECi equals to 5 ds/m (Table 5.), the represented
data indicates that there is a gradual increments in the accumulated salts in the different soil layers
with increasing the number of irrigations.
In the early vegetative growth, the EC for the whole soil profile under the investigated wheat
varieties showed an average value around 1.36 ds/m which is very near to the one where irrigation
was practiced with fresh water. However, at the end of the vegetative growth and the start of the
flowering stage where the leaf area reached its maximum value there was a notable increase in the
EC, being with an average value 4.15 ds/m, nearly three times greater than the one measured after
the previous irrigation. It is well recognized that for the cereal crops, in our case the wheat, both
flowering and seed filling stages are very sensitive ones to salinity.
Regarding the data obtained, it could be concluded that irrigation with saline water up to 5 ds/m
could be used safely, hence, the successive irrigation with such salinity level up to the flowering
stage, the most sensitive one, the accumulated salts were of an average value around 4 ds/m which
is at a level still below the one which the investigated wheat varieties could tolerate.
Concerning the soil salinity management, in view of soil salinity data obtained, the leaching of
accumulated salts frequently with each irrigation is not recommended. Leaching should be practiced
at the end of the cropping period after harvesting, hence, as shown in (Table 5.), at the wheat ripening
period, the accumulated salts were of an average value around 7.63 ds/m which is exceeding the
threshold value which the investigated wheat varieties could tolerate.
Doubling the irrigation salinity level up to 10 ds/m another picture appeared (Table 5.). As a
general trend the salts were accumulated at the different soil depths as well as within the whole soil
profile with values more or less the double of the ones recorded under the 5 ds/m irrigation treatment.
In our study, irrigation with 10 ds/m saline water, the flowering stage, accumulated salts were of an
EC-value around 9 ds/m which is relatively a high value exceeding the one that wheat could tolerate.
The presence of accumulated salts with relatively high EC–value at this sensitive stage requires
immediate leaching of the accumulated salts to avoid the negative salinity impact on the next
sensitive growth stage i.e. the seed filling stage.
Such data indicate that the degree of accumulated salts in the active root zone will differ according
to the variation in the salinity level of irrigation water. In this regard, monitoring and following up the
soil EC–values during the cropping period particularly at the critical growth stages is of paramount
importance to decide on when to leach and what should be the leaching fraction.
Soil salinity after wheat harvesting
After harvesting, the soil samples packed in the lysimeter were divided into the following soil layer
depths: (0-15 cm) the upper layer, (15-30 cm) the intermediate layer and (30-45 cm) the bottom layer.
EC of the above mentioned investigated layers was determined using the saturation paste technique
(Table 6).
55
Table 6. Electrical conductivity (ds/m) of the different soil layers measured in the soil saturation paste
after harvest
Electrical conductivity (ds/m) of different soil layers
Wheat varieties
Treatment
V1
V2
Soil layer
(ds/m)
Trial A (100% irr. treatment)
0 - 15
0.94
1.02
15 - 30
0.80
0.80
FW
30 - 45
0.90
0.71
Avg.
0.88
0.84
0 - 15
6.59
6.36
15 - 30
3.59
4.95
5 ds/m
30 - 45
3.81
4.47
Avg.
4.66
5.26
0 - 15
9.95
11.09
15 - 30
6.48
9.00
10 ds/m
30 - 45
7.17
9.55
Avg.
7.86
9.88
Trial B (60% irr. treatment)
0 - 15
1.15
1.04
15 - 30
0.90
0.74
FW
30 - 45
0.92
0.81
Avg.
0.99
0.86
0 - 15
5.58
5.34
15 - 30
3.58
4.53
5 ds/m
30 - 45
3.60
4.24
Avg.
4.25
4.70
0 - 15
7.97
10.41
15 - 30
6.34
9.61
10 ds/m
30 - 45
6.90
7.69
Avg.
7.07
9.24
Trial B (40% irr. treatment)
0 - 15
1.19
0.80
15 - 30
0.77
0.78
FW
30 - 45
0.90
0.80
Avg.
0.95
0.79
0 - 15
3.86
3.37
15 - 30
3.10
3.58
5 ds/m
30 - 45
3.39
3.44
Avg.
3.45
3.46
0 - 15
8.89
8.37
15 - 30
6.68
7.01
10 ds/m
30 - 45
6.36
7.86
Avg.
7.31
7.74
V3
Avg.
0.94
0.75
0.80
0.83
5.51
4.66
4.66
4.94
7.74
7.28
8.31
7.78
0.97
0.79
0.80
0.85
6.15
4.40
4.31
4.95
9.59
7.59
8.34
8.51
1.09
0.71
0.89
0.89
4.54
3.21
3.07
3.60
10.16
6.30
6.37
7.61
1.09
0.78
0.87
0.92
5.15
3.77
3.63
4.19
9.51
7.42
6.98
7.97
0.85
0.79
0.81
0.82
2.98
2.87
2.91
2.92
7.45
7.31
7.60
7.45
0.95
0.78
0.84
0.85
3.40
3.18
3.25
3.28
8.24
7.00
7.27
7.50
As shown in Table 6, keeping the salt concentration level of the irrigation water constant and
changing the wheat varieties, the degree of salt accumulation in the different soil layers as well as the
average salt concentration level within the whole soil profile were more or less of similar values, with
only slight difference between the investigated varieties. On the other hand, considering the degree of
salt accumulation within the whole soil profile as well as in the different soil layers, the data shows
that there was a gradual increase in the salinity concentration with the gradual increments of the ECi
values.
Considering the average electrical conductivity values within the whole soil profile, it is noticed that
under the 100% successive irrigation with saline water of 5 ds/m from seedling stage till maturity
brought the accumulated salts in the whole soil profile to an average Ec-value of 4.95 ds/m. Doubling
the Eci from 5 to 10 ds/m resulted in a 72% increase in the accumulated salts with an average value
of 8.51 ds/m.
56
Under trial A, considering the active root zone where the wheat roots penetrate is of depth lying
between 30 and 45 cm it can be observed that under successive irrigation with the low salinity level 5
ds/m, the accumulated salts in the active root zone up to 45 cm reached after harvesting an average
Ec-value around 5 ds/m which the crop wheat with its investigated varieties could tolerate
(Hamdy,1999). This clearly explains the reason behind having a grain yield production under the 5
ds/m irrigation treatment more or less equal to the one obtained under irrigation with fresh water. This
again confirm, that for the investigated wheat varieties, irrigation with saline water up to 5 ds/m can be
used safely without having any significant losses in the grain yield.
In this regard and concerning saline irrigation management, it could be wisely said that it is not
necessary to leach the accumulated salts at the previous sensitive growth stage (flowering and seed
filling), hence, the accumulated salts at both stages will be of an Ec-value substantially lower than the
ones at the harvest time and therefore, it is recommended that leaching be carried out at the end of
the cropping period after the yield harvest.
This is not the case, where irrigation was practiced with water of salinity level 10 ds/m. The
accumulated salts in the active root zone (0-45 cm) were of an average value 8.5 ds/m which is
relatively higher than the one that wheat sensitive growth stages can tolerate. To avoid the negative
impact of salts being accumulated in excess in the active root zone on the grain production, it is
advisable that leaching to be carried out before reaching such relatively high soil salinity levels
particularly at the sensitive growth stages.
Concerning the salt distribution and accumulation in the different soil layers, the presented data
(Table 6.)indicates that for the investigated Eci-values including the fresh water, there is a general
trend characterizing the salt accumulation with the different soil depths, showing the higher Eci-value
at the upper layer (0-15 cm), followed by the bottom one (30-45 cm), while the intermediate layer
(15-30 cm) was the lowest in its accumulated salts. The intermediate soil layer being with an Ecivalue lower than in the ones of both upper and bottom layer could be explained on the ground that the
intermediate layer is subjected to two processes both leading to the removal of salts from this layer:
The first, during the irrigation and the downward water movement leaching salts from this layer to the
bottom one, the second, during the drying and the upward movement of water by capillary rise
carrying with it the salts to upper surface layer.
Regarding the Trial-b (Table 6), where deficit irrigation was practiced, the presented data indicates
that under both investigated Eci, the accumulated salts as well as its distribution in the different soil
layers followed a trend identical to the one under the A-Trial. However, as presented in Fig. 3.
The distribution of salts in the soil layers
FW
9
5 ds/m
8
10 ds/m
ECi (ds/m)
7
6
5
4
3
2
1
0
100%
60%
40%
Irrigation treatments
Fig. 3. The distribution of salts in the different soil layers at the end of the cropping period
57
Under deficit irrigation (Trial-B), the accumulated salts with the whole soil profile as well as in the different
soil layers, were of lower values than the ones measured under the 100% irrigation treatments. Under the
60% irrigation treatment with the 5 ds/m saline water, the soil profile was of an Eci-value 4.19 ds/m with
nearly 15% reduction in the accumulated salts observed under the 100% irrigation treatment.
This was also the case with the relatively high salinity level 10 ds/m, where the accumulated salts were of
values nearly 10 % lower than the ones corresponding to the 100% irrigation treatment.
Under sever water stress, the 40% irrigation treatment, the accumulated salts were found with an
average values lower than the ones related to the 60% irrigation treatment and corresponded to 66% and
88% of the Eci-values obtained under the 100% irrigation for the 5 and 10 ds/m irrigation salinity level
respectively.
CONCLUSIONS
In view of the presented data and results obtained, we can come up to some important conclusions,
among them the following to be highlighted:
Irrigation with saline water up to 5 ds/m could be used safely, hence, the successive
irrigation with such salinity level up to the flowering stage, the most sensitive one, the
accumulated salts were of an average value around 4 ds/m which is at a level still below the
threshold value which the investigated wheat varieties could tolerate.
For wheat varieties under investigation, irrigation salinity level could be raised up to 10ds/m
resulting in only around 10% losses in the grain yield production.
The presented data show that the higher is the salinity level of irrigation water; the lower will
be the consumptive water use, and the greater will be the biomass and the grain water use
efficiencies. This also holds true under deficit irrigation using saline water. The smaller is the
volume of water applied and the higher is its salinity level; the better will be the improvement
in both biomass and grain water use efficiencies.
Among the investigated irrigation treatments the 60% irrigation with saline water of an ECivalue 5 ds/m is the one to be recommended as it satisfies our major objective in achieving a
good fresh water saving, convenient wheat production, as well as keeping the soil at a
relatively low salinity level could be easily leached by precipitation and or by relatively small
fresh water volumes and thereby bringing the soil again to its original productivity level.
REFERENCES
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115:73-86.
François, L.F. (1981). Alfalfa management under saline condition with zero leaching. Agronomy
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Hamdy, A. (1990a). Management practices under saline water irrigation. Symp. On Scheduling of
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application and leaching (in press).
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Hamdy, A., Abdel-Dayem, S. and Abu-Zeid, M. (1993). Saline water management for optimum crop
production. Agricultural water management 24:189-203.
Hamdy, A. (1994). Use and management of saline water for irrigation towards sustainable
development. In: Sustainability of irrigated agriculture. (eds) Pereira L.
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Hamdy, A. (1996). Saline irrigation: assessment and management techniques. In: Choukr-Allah,
R.; Malcom, L.V.; Hamdy A. (eds). Halophytes and Biosaline Agriculture. Dekker, New York,
pp. 147-181.
Hamdy, A. (1999). Saline irrigation assessment and management for a sustainable use. Proceedings:
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Hamdy, A. and Katerji, N. (2006). Water crisis in the Arab World. Analysis and Solutions.
CIHEAM/MAIB publication, pp. 60.
Van Hoorn, J.W.; Katerji, N.; Hamdy, A. and Mastrorilli, M. (1993). Effect of saline water on soil
salinity and on water stress, growth and yield of wheat and potatoes. Agr. Water Management 23,
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59
IRRIGATION STRATEGIES FOR OPTIMAL USE OF SALINE WATER
IN MEDITERRANEAN AGRICULTURE
G. Crescimanno and P. Garofalo
Università di Palermo, Dipartimento ITAF – Sezione Idraulica, Viale delle Scienze, 13
90128 Palermo, ITALY. [email protected]
SUMMARY – In this paper management strategies optimizing irrigation, and also reducing the risk of
secondary salinization, were explored for seven Sicilian soil profiles by using the SWAP model. Two
viable options addressing constraints of limited water availability were simulated for the seven soil
profiles. These options were (i) different irrigation scheduling, i.e. irrigation with a fixed amount of
water but different number of irrigations, and (ii) cyclic strategies, i.e. alternating two irrigation waters
having different salinity. Analysis of three different irrigation scheduling evidenced that making a
limited number of irrigations (two in our case), using larger application volumes, determined a lower
risk of salinization. With reference to the role of cracks in the process of salt-leaching, the simulations
performed indicated that water stored in cracks promoted leaching of the accumulated solutes, and
that neglecting the presence of cracks led to overestimating salinization. Cyclic strategy proved to be
the best management option to be suggested to reduce the risk of salinization. Findings concerning
the role of cracks in the process of salt-leaching suggested that, under field conditions, application of
a leaching solution was more efficient if the soil presented a considerable degree of cracking.
Key words: Salinization, Cracking, Irrigation, Management scenarios
RESUME – Dans ce papier on a exploré des différentes options de gestion de l'irrigation qui peuvent
aider à réduire le risque de salinisation en appliquant le model SWAP à sept profiles de sol en Sicile.
On a exploré (i) trois différentes calendrier d'irrigation et (ii) l'alternance de deux eaux d'irrigation
ayant une différente salinité. Les résultants ont démontré que la meilleure gestion se peut réaliser en
faisant deux irrigations seulement. En plus, les résultas ont démontré l'importance que les fissures du
sol peuvent avoir dans la lixiviation des sals accumulés dans le sol, en indiquant qu'il faut tenir en
compte les fissures dans la prévision de la salinisation du sol. L'alternance de deux eaux de différente
salinité se démontre être la pratique la plus efficace pour prévenir la salinisation du sol. En plus,
l'application d'une solution lixiviante se démontre plus efficace si la même est fait quand le sol
présente une considérable percentage de fissures.
Mots-clés: Salinisation, Fissures, Irrigation, scénarios de gestion
INTRODUCTION
In Mediterranean regions, irrigation with saline/sodic waters, often a consequence of intensive
agricultural systems, is one of the main causes of secondary salinization, resulting in soil degradation.
Although accurate worldwide data are not available, vast areas of irrigated land are increasingly
threatened by salinization and/or sodication.
Sustainable land management practices are urgently needed to preserve the production potential
of agricultural land while safeguarding environmental quality. According to one of the various
definitions given by FAO (1993), sustainable land management combines “ technologies, policies and
activities aimed at integrating socio-economic principles with environmental concern so as to protect
the potential of natural resources and prevent degradation of soil and water quality”.
In Sicily, the increasing scarcity of good quality waters coupled with intensive use of soil under
semi-arid to arid climatic conditions results in irrigation with saline waters. Salinization is closely
associated with the process of desertification, defined as “land degradation in arid, semi-arid and dry
61
sub-humid areas resulting from climatic variations and human activities”, with the term “land” including
soil, water resources, crops and natural vegetation (UNEP, 1991).
Without appropriate management, irrigated agriculture can be detrimental to the environment and
endanger sustainability. Therefore, the goal of modern irrigation is to develop methods allowing to
save water and to improve both the water and the salt distribution within the root zone, also
preserving maintenance of good structural conditions. According to one of the various definitions
given by FAO (1993), sustainable land management combines “technologies, policies and activities
aimed at integrating socio-economic principles with environmental concern so as to protect the
potential of natural resources and prevent degradation of soil and water quality”.
van Dam et al. (1997) developed a model describing water and solute transport in the vadose
zone, taking into account soil shrinkage and cracking. This model, named SWAP93, provides as
output the water content (and matrix potential), as well as the concentration of the soil solution, C,
from which the electrical conductivity of the saturated extract (ECsat) can be also calculated (Rhoades,
1996).
Crescimanno and Garofalo (2005) tested the applicability of SWAP for prediction of water content
(θ) and electrical conductivity of the saturated extract (ECsat) in a Sicilian clay soil having a high
shrink-swell potential and susceptibility to cracking. Using θ measurements collected from seven
profiles located in a Sicilian vineyard, they found that using the parameter estimation method based
on multi-step outflow experiments, and representing the soil hydraulic properties by the Brutsaert
retention equation, coupled with the hydraulic conductivity model proposed by Gardner (B-G model), it
was possible to obtain an accurate prediction of θ.
In this paper management strategies optimizing irrigation, and also reducing the risk of secondary
salinization, will be explored for some Sicilian soil profiles by using the SWAP model. Options
addressing constraints of limited water availability were simulated. These options were (i) different
irrigation scheduling, i.e irrigation with a fixed amount of water but different number of irrigations, and
(ii) cyclic strategies, i.e. alternating two irrigation waters having different salinity.
MATERIALS AND METHODS
Soil shrinkage and hydraulic characteristics
Data collection was carried out in a 25 by 25 m field located in Sicily (37° 40’ 55” N; 12° 38’ 50” E)
where irrigation with saline waters is performed on grapes by a sprinkler system, which allows high
application rates at the soil surface. Irrigation water is taken from the Trinità artificial reservoir. The
electrical conductivity of irrigation water, ECw, is about 2.1 dS/m. However, when rainfall is particularly
low, and water stored in this reservoir is not enough to cover irrigation needs, water from wells is used
for irrigation, with ECw values up to about 6.2 dS/m.
Seven soil profiles (Baglio1-Baglio7) were considered in this field. The soil shrinkage curve was
determined by measuring vertical and horizontal shrinkage on undisturbed soil cores (diameter d=8.5
cm, height H=11.5 cm) (Crescimanno and Provenzano, 1999). The shrinkage characteristic was
expressed by the model proposed by Kim (Crescimanno and Garofalo, 2005).Bulk density (ρb) was
determined from the shrinkage curve and used to calculate the volumetric water content, θ, which
therefore accounted for a variable soil volume. The coefficient of linear extensibility, COLE (Grossman
et al., 1968), indicating the shrink-swell potential (Parker et al., 1977), was also calculated.
Parameter estimation was carried out according to Crescimanno and Garofalo (2005),
representing the soil hydraulic functions by:
62
-
the equation proposed by Brutsaert (B) (1966), for the water retention curve:
[
θ − θr
n'
= Θ = 1 + α ′h
θs − θr
]
−1
(1)
- coupled with the model proposed by Gardner (1958) (G) for the hydraulic conductivity function k(h):
k (h ) =
k sat
1 + βh
(2)
λ
where h (cm) is the pressure head, θs is the volumetric water content at saturation, θr is the residual
water content, k is the unsaturated hydraulic conductivity (cm/h), ksat is the saturated hydraulic
conductivity (cm/h), α’, n’, β and λ are empirical parameters.
The soil physical and chemical properties, together with the soil shrink-swell potential, were
reported in Table 1. The soil hydraulic parameters were reported in Table 2.
% ____
Shrinkswell
potential §
h=-333 cm
to oven-dry
ESP #
Sand
Silt
_____
COLE ‡
ECsat ¶
cm
Clay
Depth
Classification †
Horizon
Table 1. Classification, physical and chemical properties, COLE and shrink-swell potential of the
considered soils.
dS/m
%
Baglio1
Typic Chromoxerert
Ap
0-30 35
28
37
0.052
Medium
2.38
3.5
Baglio1
Typic Chromoxerert
A1 30-60 33
23
44
0.049
Medium
3.56
5.2
Baglio2
Typic Chromoxerert
Ap
0-30 36
24
40
0.065
High
1.83
3.8
Baglio2
Typic Chromoxerert
A1 30-60 30
24
46
0.069
High
2.52
5.0
Baglio3
Typic Chromoxerert
Ap
0-30 34
27
39
0.103
Very high
1.75
3.8
Baglio3
Typic Chromoxerert
A1 30-60 34
21
45
0.083
High
2.35
4.8
Baglio4
Typic Chromoxerert
Ap
0-30 32
28
40
0.054
Medium
1.80
3.4
Baglio4
Typic Chromoxerert
A1 30-60 33
23
44
0.062
High
2.47
5.1
Baglio 5
Typic Chromoxerert
Ap
0-30 35
28
37
0.132
Very high
2.17
3.5
Baglio 5
Typic Chromoxerert
A1 30-60 21
37
42
0.122
Very high
2.06
3.8
Baglio 6
Typic Chromoxerert
Ap
0-30 42
29
29
0.113
Very high
1.93
3.4
Baglio 6 Typic Chromoxerert
A1 30-60 44
23
33
0.101
Very high
2.59
3.5
Baglio 7 Typic Chromoxerert
Ap
0-30 44
27
29
0.080
High
2.22
3.0
Baglio 7 Typic Chromoxerert
A1 30-60 43
22
35
0.077
High
2.88
3.5
† Soil Survey Staff, 1992
‡ COLE= coefficient of linear extensibility
§ Parker et al., 1977
¶ ECsat = Electrical Conductivity of saturated soil extract
# ESP = Exchangeable Sodium Percentage
63
Table 2. Hydraulic parameters determined according to the hydraulic conductivity equation proposed
by Gardner coupled with the Brutsaert retention equation (B-G model).
Hydraulic parameters
Soil
Baglio 1
Baglio 1
Baglio 2
Baglio 2
Baglio 3
Baglio 3
Baglio 4
Baglio 4
Baglio 5
Baglio 5
Baglio 6
Baglio 6
Baglio 7
Baglio 7
Horizon
Ap
A1
Ap
A1
Ap
A1
Ap
A1
Ap
A1
Ap
A1
Ap
A1
ksat †
cm/h
4,70
0,30
1,49
0,05
4,05
0,29
2,67
0,11
0,78
0,03
0,24
0,01
1,74
0,02
θs ‡
3
cm /cm
0,47
0,47
0,50
0,48
0,47
0,47
0,50
0,48
0,51
0,49
0,51
0,49
0,55
0,53
θr §
3
3
cm /cm
0,23
0,28
0,27
0,28
0,29
0,29
0,25
0,25
0,31
0,31
0,31
0,32
0,28
0,30
3
α' #
-1
cm
0,002
0,017
0,038
0,025
0,024
0,009
0,040
0,032
0,0031
0,0081
0,0012
0,0118
0,0174
0,0730
n' #
-1
cm
0,883
0,408
0,463
0,322
0,876
0,420
0,520
0,265
0,826
0,483
0,514
0,500
0,386
0,336
β#
λ' #
0,079
1,486
2,049
0,333
0,470
2,659
0,068
1,174
0,130
0,313
2,89
1,13
1,03
0,134
2,917
1,650
2,270
3,081
4,065
2,704
4,209
1,321
3,275
1,626
1,295
1,045
1,98
2,48
† ksat = saturated hydraulic conductivity of the soil matrix, fixed at measured value
‡ θs = saturated volumetric water content at saturation, fixed at measured value
§ θr = residual water content
# parameters of B-G model
Management scenarios
Climatic data (rain intensity, maximum and minimum temperature, rainfall height) recorded daily
from 08/07/1998 to 31/12/2000 by a rain gauge located in the field were used as input in SWAP.
Annual rainfall in 1998, 1999 and 2000 was 390 mm in average and the annual reference
evapotranspiration in 1998, 1999 and 2000 was 1450 mm in average. Although an annual amount of
irrigation water equal to 120 mm is supplied under normal conditions, due to the constraints of limited
water availability, the annual irrigation amount supplied from 1998 to 2000 was very low, and equal to
66 mm in 1998, to 48 mm in 1999, and to 24 mm in 2000. The irrigation season in this vineyard
usually ranges from mid June to mid September. A root distribution characterized by 60% roots in the
30-70 cm layer, and by 20% both in the 0-30 cm and in the 70-100 cm layers, was assumed
(Crescimanno and Garofalo, 2005). Simulations were performed by using a bottom boundary
condition of freely draining profile, and the B-G hydraulic parameters were used to simulate water
transport.
The following management scenarios were considered:
3
− Scenario 1 Irrigation scheduling. Irrigation with a fixed annual volume of 1120 m , and electrical
-1
conductivity of irrigation water equal to 6.2 dS m (the most critical possible salinity value), but testing
different options in terms of number of water applications, i.e.: 1a: eight water applications, which
means weekly irrigation; 1b: four water applications, which means irrigation every two weeks; 1c: two
water applications, which means a monthly water application. The 1c is the irrigation scheduling more
often used in this irrigated area.
To explore how cracks may affect the process of salt-accumulation and/or leaching, scenario 1c
was repeated under the hypothesis of no shrinkage, which means no cracking and bypass flow. This
scenario was indicated with 1c’.
3
− Scenario 2c – Cyclic strategy. Irrigation with a fixed annual volume of 1120 m , but alternating
two waters of different salinity. The saline irrigation water is the one used in Scenario1, the less saline
water, with ECw=2.1 dS m-1, which is the value measured during the winter season, is used when the
crop is more sensitive to salinity according to the crop physiology.
64
A performance indicator (Smets et al., 1997) was used to evaluate the impact of management
scenarios on salinization:
∆S = S f − S i
(3)
where Si and Sf (mg cm-2) represent the quantity of salts accumulated in the soil profile at the starting
date and to the end of simulation, respectively.
In order to compare the different scenarios in terms of crop transpiration, and of evaporation, the
following ratios were calculated:
RT=Tscen/T1c
(4)
RE=Escen/E1c
(5)
where Tscen (cm) and Escen (cm) were the actual crop transpiration and evaporation of the considered
scenario, and T1c (cm) and E1c (cm) represent transpiration and evaporation obtained by scenario 1c,
which is the commonly applied irrigation scheduling in the irrigated area.
RESULTS AND DISCUSSION
Irrigation scheduling (Scenario 1)
Amount of salts accumulated in the soil profile, ∆ S,
(mg/cm2)
Decreasing ∆S values were obtained for the seven profiles passing from scenario 1a to scenarios
1b and 1c (Fig. 1). This result can be explained by the fact that reducing the number of irrigations, and
increasing the amount of water applied, determined a higher application intensity (I). Since in all the
three scenarios irrigation was performed in summer (starting date June 15), when cracks were open
and the hydraulic conductivity (HC) of the soil matrix was low, bypass flow of water was prevalent.
According to the SWAP, at increasing I, an increasing amount of water, and of dissolved salts,
bypasses the upper layers, rapidly reaching the bottom layers. This is the reason why, when irrigation
was performed according to scenario 1c, a higher percentage of water and salts bypassed the surface
layers compared with scenarios 1b and 1c.
50
45
40
Scenario 1a
Scenario 1b
Scenario 1c
35
30
25
20
15
10
5
0
Baglio 1
Baglio 2
Baglio 3
Baglio 4
Baglio 5
Baglio 6
Baglio 7
Fig. 1. Amount of solutes accumulated, ∆S (g/cm2), in the seven soil profiles according to the three
considered irrigation scheduling (Scenario 1)
65
Concerning relative transpiration, the highest RT values were associated with scenario 1c
(Table 3). This was not only a consequence of the lower ∆S, but was also the consequence of water
content distribution in the profile after irrigation (Fig. 2, Baglio1 profile). As can be seen in the figure, θ
values higher than those obtained by the 1a and by the 1b scenarios were obtained by scenario 1c in
the 5-60 cm layer, where the maximum percentage of roots was concentrated, one day after irrigation.
This water distribution was the consequence of bypass flow, which promoted storage of water in the
deepest layers. Consistently with this water distribution, the lowest evaporation was also obtained in
scenario 1c, as demonstrated by the RE values (Table 4).
0,23
Volumetric w ater content, θ, (cm3/cm3)
0,28
0,33
0,38
0,43
0,48
0
-10
Depth (cm)
-20
-30
-40
-50
-60
-70
Scenario1a)
-80
Scenario1b)
-90
Scenario1c)
-100
Fig. 2. Water distribution along the soil profile one day after irrigation (Baglio1 profile)
Table 3. Ratio (RT) between transpiration (T) obtained by scenarios 1a, 1b, 1c and 2c, and T obtained
by scenario 1c.
Baglio 1
0,88
0,98
1,00
1,06
Actual
Transpiration
(cm)
29,43
Baglio 2
0,75
0,90
1,00
1,04
44,51
Baglio 3
0,88
0,95
1,00
1,03
43,77
Baglio 4
0,87
0,98
1,00
1,02
43,62
Baglio 5
0,81
0,92
1,00
1,02
44,58
Baglio 6
0,81
0,89
1,00
1,02
28,85
Baglio 7
0,79
0,90
1,00
1,03
35,62
Scenario 1a
66
Scenario 1b
Scenario 1c
Scenario 2c
Table 4. Ratio (RE) between evaporation (E) obtained by scenarios 1a, 1b, 1c and 2c, and E obtained
by scenario 1c.
Scenario 1a
Scenario 1b
Scenario 1c
Scenario 2c
Actual
Evaporation
(cm)
Baglio 1
1,04
1,01
1,00
1,00
86,05
Baglio 2
1,19
1,08
1,00
0,99
57,55
Baglio 3
1,11
1,06
1,00
0,99
60,32
Baglio 4
1,08
1,05
1,00
0,99
65,23
Baglio 5
1,15
1,02
1,00
1,00
61,41
Baglio 6
1,07
1,04
1,00
0,99
84,07
Baglio 7
1,10
1,05
1,00
0,99
70,24
These results showed that under our conditions, reducing the number of irrigations, and increasing
the irrigation amount at each application, proved to be the best strategy to prevent salinization, also
enhancing crop transpiration.
Cyclic strategies (Scenario 2c)
With reference to alternating two waters of different salinity, expressed as ECw, (first water with
lower salinity, then water with higher salinity) (Scenario 2c), the ∆S values obtained by Scenario 2c
(Fig. 3) were significantly lower that those provided by Scenario 1c for all seven profiles. This
indicated that, as expected, this strategy effectively prevented salinization (Rhoades, 1989;
Crescimanno et al., 2002).
Amount of salts accumulated in the soil profile, ∆S,
(mg/cm2)
45
Scenario 1c
35
Scenario 2c
25
15
5
-5
Baglio 1
Baglio 2
Baglio 3
Baglio 4
Baglio 5
Baglio 6
Baglio 7
-15
Fig. 3. Amount of solutes accumulated in the soil profiles, ∆S (g/cm2), according to scenarios 1c
and 2c.
However, considerable differences were found between the different profiles in terms of ∆S
(Fig. 3). Negative ∆S values, indicating salt-leaching, were obtained only for Baglio4 and Baglio2;
negligible ∆S values, indicating no solute accumulation, for Baglio1; and positive and increasingly
higher ∆S, indicating salt-accumulation, for Baglio7, Baglio3, Baglio5 and Baglio6 (in order of
increasing ∆S).
67
Baglio7
Baglio6
Baglio5
Baglio4
Baglio3
Baglio2
Baglio1
Solute flux through bottom profile, CWQ, (g/cm2/d)
The negative ∆S values found for Baglio4 and Baglio2 were certainly due to the highest CWQs
(Fig. 4); the difference (diff2=∆S1c - ∆S2c) between the ∆S values obtained with scenarios 1c and 2c
decreased from 30.40 mg cm-2 (Baglio4) to 26.90 mg cm-2 (Baglio 6), following the same order in
which CWQ decreased.
0
-10
-20
-30
-40
-50
-60
-70
CWQcr
-80
CWQm
-90
-100
Fig. 4. Overall flux of solutes, CWQ (g/cm2), from the soil profiles in the 2c scenario
2,5
2,0
1,5
1,0
Scenario 1c
0,5
Scenario 2c
Dec-00
Oct-00
Aug-00
Jun-00
Apr-00
Feb-00
Dec-99
Oct-99
Sep-99
Jul-99
May-99
Mar-99
Jan-99
Nov-98
Sep-98
0,0
Jul-98
Average ECsat in the soil profile (dS/m)
3,0
Fig. 5. Average electrical conductivity of the saturated extract, ECsat (dS/m), vs time (Baglio1 profile).
Higher RT values corresponded to scenario 2c compared with those obtained by scenario 1c
(Table 3). This result can be explained by the lower average values of ECsat in the soil profile (Fig. 5),
which . determined a higher root water flux, Sa. The same RE values (Table 4) were found in
scenarios 1c and 2c. The reasons for this are that RE was not influenced by salinity, and that
scenarios 1c and 2c determined the same water distribution along the profile.
68
Cracking, salinization and salt-leaching (Scenario 1c’)
To evaluate the influence of cracks on salinization, and to check the consequences of neglecting
shrinkage and cracking on selection of irrigation strategies preventing salinization, scenario 1a was
repeated with the assumption of no shrinkage and cracking, i.e. rigid soil (scenario 1c’).
Amount of salts accumulated in the soil profile, ∆ S,
(mg/cm2)
The ∆S values obtained by scenario 1c’ (Fig. 6) were always higher than those obtained by
scenario 1c, in which cracks were taken into account. Since the only difference between scenarios 1c
and 1c’ was that in this latter scenario the soil was considered as non shrinking, with no cracks, the
lower ∆S obtained by scenario 1c certainly depended on the fact that the cumulative water flow from
the cracks into the matrix, CWF (cm) (Fig. 7), was taken into account. Significantly different CWFs
were found for the different profiles, with the lowest value for Baglio3, and increasingly higher values
for Baglio1, Baglio6, Baglio5; Baglio2 and Baglio7 (in the order of increasing CWF). A significantly
higher CWF was found for Baglio4. It is interesting to notice that cracks differently affected the
difference in ∆S between scenarios 1c and 1c’. For Baglio1 and Baglio3 this difference (diff1=∆S1c∆S1c’) was negligible; for the other profiles, the effect of the cracks was more pronounced, especially
for Baglio2 (diff1= 8.0 mg cm-2), Baglio7 (diff1 = 8.2 mg cm-2) and Baglio4 (diff1=16.6 mg cm-2). The
increasing order of diff1 corresponded to a decreasing order of CWF (Fig. 7).
50
Scenario 1c
40
Scenario 1c'
30
20
10
0
Baglio 1
Baglio 2
Baglio 3
Baglio 4
Baglio 5
Baglio 6
Baglio 7
Fig. 6. Amount of solutes accumulated in the soil profiles, ∆S (g/cm2), in scenarios 1c and 1c’
Comparing results of scenarios 1c and 1c’ on the different soil profiles suggested that if cracks and
water storage in cracks were not taken into account, the risk of salinization was overestimated. The
magnitude of this overestimation depended on the soil shrinkage behaviour, being greater at
increasing shrinkage and cracking. For soils showing a considerable susceptibility to shrinkage and
cracking, management strategies optimizing irrigation should therefore be obtained by physicallybased models taking into account a variable soil volume.
69
9
8
7
6
5
4
3
2
1
Baglio7
Baglio6
Baglio5
Baglio4
Baglio3
Baglio2
0
Baglio1
Cumulative water flow form cracks into matrix, CWF,
(cm)
10
Fig. 7. Cumulative water flow from the cracks into the matrix, CWF (cm), obtained for the different
profiles
CONCLUSIONS
Analysis of three different irrigation scheduling evidenced that the best scheduling was to make a
limited number of irrigations (two in our case), using larger application volumes. This result was found
to depend on the water distribution in the soil profile, which in turn depended on bypass flow of water,
determined by the higher water application intensity involved in this scenario. As a consequence in
our case, bypass flow was a mechanism determining a favorable water distribution. However, this
result can be considered valid only for crops developing a deep root distribution. The best irrigation
scheduling is therefore a function of soil type and crop characteristics, and the best option is to be
found by simulations taking specific site conditions into account.
Cyclic strategy proved to be the best management option to be suggested to reduce the risk of
salinization (scenario 2c).With reference to the role of cracks in the process of salt-leaching (Scenario
1c’), the simulations performed indicated that water stored in cracks promoted leaching of the
accumulated solutes, and that neglecting the presence of cracks led to overestimating salinization.
This overestimation was significant for the soils having a considerable susceptibility to shrinkage and
cracking. When irrigation is performed in cracking soils, simulation models taking into account cracks
should therefore used to explore sustainable irrigation strategies.
Acknowledgments
Research supported by MURST (Rome, Italy), PRIN 2005:“Strategie e problematiche legate alla
desalinizzazione di terreni argillosi con crepacciature”.
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Rhoades, J.D. (1989). Intercepting, isolating and reusing drainage waters for irrigation to conserve
water and protect water quality. Agric. Water Manage. 6:37–52.
Shalhevet, J. (1984). Management of irrigation with brackish water. In: Soil Salinity under Irrigation. I
Shainberg and J. Shalhevet (eds.) Springer Verlag, New York. Pp. 298-318
Smets, S.M.P., M. Kuper, J.C. Van Dam and R.A. Feddes. (1997). Salinization and crop transpiration
of irrigated fields in Pakistan’s Punjab. Agricultural Water Management, 35, pp. 43-60.
Soil Survey Staff (1992). Keys to soil taxonomy 8th edition. SMSS technical monograph n.19,
Blacksburg, Virginia. Pochaontas Press Inc., 556 pp.
Szabolcs, I. (1994). Prospects of soil salinity for the 21st century. 15th International Congress of Soil
Science, Acapulco, Mexico
Tanton, TW, Rycroft, D.W. and F.M. Wilkinson, (1988). The leaching of salts from saline heavy clay
soils: factors affecting the leaching process. Soil Use and Management, Vol. 4, n. 4
UNEP, (1991). Status of desertification and implementation of the United Nations plan of action to
combat desertification. UNEP, Nairobi.
van Dam, J. C., J. Huygen, J. G. Wesseling, R. A. Feddes, P. Kabat, P. E. V. van Walsum, P.
Groenendijk and C. A. van Diepen. (1997). Theory of SWAP version 2.0. DLO Winand Staring
Centre, Wageningen, 1997.
Yaalon, D.H., Kalmar, D. (1978). Dynamics of cracking and swelling of clay soils: Displacement of
skeletal grains, optimum depth of slickensides, and rate of intra-pedonic turbation. Earth Surf.
Proc., 3: 31-42.
71
EFFECT OF SUPPLEMENTARY SALINE IRRIGATION ON YIELD AND
STOMATAL CONDUCTANCE OF WHEAT UNDER THE MEDITERRANEAN
CLIMATIC CONDITIONS
*
**
A. Yazar , A. Hamdy , B. Gencel *, M. S. Sezen *** and M. Koç ****
* Irrigation and Agricultural Structures Department, Cukurova University, 01330 Adana-Turkey;
** Mediterranean Agronomic Institute, via Ceglie 9, 70010 Valenzano, Bari, Italy
*** Soil and Water Research Institute, Water Management Research Unit,
P.O.Box 23 33400 Tarsus, Turkey
**** Field Crops Department, Cukurova University, 01330 Adana-Turkey
SUMMARY- The response of wheat (Triticum aestivum L.) to different salinity levels of irrigation water
under the Mediterranean climatic conditions was investigated in a field study at the experimental
station of Cukurova University in Adana, Turkey during the 2001-2002 growing season. Saline waters
with electrical conductivity values of 0.5 (canal water), 3.0, 6.0, 9.0, and 12.0 dS/m were used for
irrigation of wheat. The average grain yields ranged from 5940 to 6484 kg /ha in different treatments.
The effect of salinity levels of irrigation water used in the study on grain yields was not significantly
2
different (P<0.4057). Average dry-matter yields varied from 1506 to 1691 g/m from the different
treatments at harvest time. However, treatments resulted in similar biomass yields (P<0.3664). Water
3
use efficiency (WUE) values from the treatments ranged from 1.29 to 1.44 kg/m . As the salinity level
of irrigation water increased WUE values also increased slightly. Harvest index (HI) values from the
different treatments varied from 0.38 to 0.42. However, there was no significant difference among the
treatments. Generally soil salinity increased with salinity content of irrigation water used in the study.
Soil salinity decreased almost linearly with increasing depth in the profile. There was no well-defined
relationship between stomatal conductances of wheat leaves and irrigation water salinities under the
study conditions. Thus, the results obtained provide a promising option for the use of poor quality
water can be used for irrigation of wheat crop in the Mediterranean region without undue yield
reduction and soil degradation since effective winter rainfalls leach the salts out of the root zone as
long as an efficient drainage system is provided.
Key words: Saline water, wheat yield, dry matter yield, water management, water use efficiency,
stomatal conductance
RESUME- La réponse et la conductance stomatale du blé (Triticum aestivum L.) aux différents
niveaux de salinité de l’aux d’irrigation dans les conditions climatiques méditerranéennes a fait l’onjet
d’une étude menée à la expérimentale de l’Université de Cukurova à Adana, Turquie pendant la
saison 2001-2002. Des eaux salées ayant des valeurs de conductivité électrique de 0.5 (eau douce),
3.0, 6.0, 9.0, et 12.0 dS/m ont été utilisée pour l’irrigation de blé. Les rendements moyens en graines
variaient de 5940 à 6484 kg/ha dans les différents traitements. L’analyse de la variance des données
des rendements en graines a montré que l’effet des niveaux de salinité de l’eau d’irrigation utilisée
dans l’étude sue les rendements en graines n’était pas significantivement différent.Les rendements
moyens en matiére séeche variaient de 1154 à 1394 g/m2 dans les différents traitements à l’époque
de la récolte. Toutefois, les traitements montraient presque les mêmes valuers des rendements en
biomasse. Puisque le blé n’a été irrigué que deux fois pendant le cycle cultural et vu les pluies assez
importantes reçues pendant le cycle, les sels apporté au sol avec l’eau d’irrigation sont restés à des
niveaux acceptables et n’ont pas affecté le rendement en biomasses du blé. En général, la salinité du
sol a augmenté avec la teneur en sel de l’eau d’irrigation utilisée dans l’étude. Donc, l’eau d’irrigation
salée peut être utilisée pour l’irrigation de la culture de blé dans le région méditerranéennes du fait
des pluies efficaces hivernales qui lessivent les sels de la zone racinaire, tant que l’on prévoit un
système de drainage efficace.
Mots clés: blé, salinité, l’eau salée, conductance stomatale
73
INTRODUCTION
Supplies of good quality irrigation water are expected to decrease in the future because the
development of new water supplies will not keep pace with the increasing water needs of industries
and municipalities. Thus, irrigated agriculture faces the challange of using less water, in may cases of
poorer quality, to provide food and fiber for an expanding population. Some of the these future water
needs can be met by using available water supplies more efficiently, bu in may cases it will prove
necessary to make increased use municipal waste waters and irrigation drainage waters. Limited
supplies of fresh water are increasingly in demand for competing uses and create the need to use
marginal quality water in agriculture. From the viewpoint of irrigation, the use of marginal quality
waters require careful planning, more complex management practices and stringent monitoring
procedures, than when good quality water is used (Oster, 1994; Beltran, 1999; Hamdy, 2002). When
the availability of freshwater is limited, agriculture is likely to be forced to make increasing use of
nonconventional waters, either brackish water or sewage effluents (Hamdy, 1999; Dinar et al., 1986).
Saline water is a potential source for irrigation. Recent research developments on plant breeding
and selection, soil crop and water management, irrigation and drainage technologies enhanced and
facilitated the use of saline water for irrigating crops with minimum adverse effects on the soil
productivity and environment (Shalhavet, 1994; Rhoades et al, 1992; Pereira, 1994).
There is usually no single way to achieve safe use of saline water in irrigation. Many different
approaches and practices can be combined into satisfactory saline water irrigation systems; the
appropriate combination depends upon economic, climatic, social, as well as edaphic and
hydrogeologic situations (Rhoades et al., 1992; Rhoades, 1999; Oster and Grattan, 2002; Bradford
and Letey, 1993).
Salinity of irrigated agricultural soils can be managed satisfactorily for salt-tolerant and moderately
salt tolerant crops when using saline water for irrigation (Ayers and Westcot, 1985; Hamdy, 2002).
Irrigation with saline water usually causes a progressive soil salinization, which is more or less severe
according to salt supply, soil properties (whether clay or sandy), leaching caused by rainfall and
applied irrigation technique. As the soil salinity rises, the osmotic potential soil water decreases
resulting in reduced water availability and physiological diseases (Shannon et al., 1994).
A careful selection of the crop and the variety most suited to a given environment is of paramount
importance for obtaining high efficient production. In general, crops can tolerate salinity up to
threshold level above which, the yields decrease approximately linearly as salt concentrations
increase (Maas, 1986; Letey et al, 1985).
Wheat (Triticum aestivum) is one of the most important cereal crops of the world to nourish the
mankind. It is grown in wide range of climatic zone and mostly in irrigated conditions. In the arid and
semi-arid areas, saline ground water is a common feature. Irrigation with saline water throughout the
growth period of crops resulted in deterimental effect on growth and yield potential of the crops.
Therefore, it will be of vital interest for scientist to try to overcome the salinity menace to predict the
wheat crop growth development and yield potential with varying salinity of irrigation water on the basis
of long term experimentation (Chauhan and Singh, 1993).
Chauhan and Singh (1993) conducted a seven-year consecutive saline irrigation experiment in
India and conclude that in light textured soils and semi arid climatic conditions, wheat can be grown
upto ECiw-8 dS/m comparable to control (canal water). The saline irrigation at ECiw-12 and 16 dS/m
reduced wheat yield by 21 and 37 per cent over control with negative significant correlation (r = -0.42).
The reduction in yield mainly caused by poor germination and tillering, stunted growth and to some
extent by low 1000 grain weight.
Datta et al. (1998) carried out an experiment in Karnal (India) using five levels of saline irrigation
treatments (ECiw = 0.5, 6, 9, 12, 18 and 27 dS/m) along with recommended agronomic and cultural
practices. Optimum yield was obtained from the treatment irrigated with canal water as 5.9 t/ha,
followed by 6 dS/m as 5.69 t/ha, and 9 dS/m as 5.39 t/ha. The treatment irrigated with saline water of
12 dS/m resulted in yield of 5 t/ha; 18 dS/m gave 4.51 t/ha. As the salinity level of irrigation water
increased yield level decreased accordingly.
74
A research aimed at investigating the possibility of applying supplemental irrigation to wheat and
barley during their sensitive phenophases of flowering and seed formation using brackish water with
salinity levels generally considered too high for its use (EC of 3–9 dS/m) was conducted in a
greenhouse at the Mediterranean Agronomic Institute in Bari, Italy. Results showed the possibility of
securing high yields, with mean reductions of only 21% in barley and 25% in wheat compared to the
fully, fresh-water irrigated control, through the application of limited amounts of brackish water. The
sustainability of the practice is presumably high, due to the limited amounts of added salts, which can
be easily leached out even by a modest precipitation (Hamdy et al., 2005).
In the Mediterranean climate, rainfed cereal crops are planted in autumn and harvested in late
spring, relying on the rains during this period for the conclusion of their cycle; the vagaries of rains,
however, often put at risk the final harvest. Thus, supplemantal irrigation of wheat is widely practiced
in the region to avoid water shortages. Reuse of drainage water for crop production is a common
practice in downstream section of the Lower Seyhan Irrigation Project (LSP) area in the
Mediterranean region of Turkey. Therefore, effective salinity control measures must be implemented
for sustainable irrigated agriculture, which requires safe use of saline, low quality irrigation and
drainage waters for crop production. Reuse of agricultural drainage water is either being practiced to
save fresh water for other uses or as in the case of LSP, insufficient fresh water availability for the
downstream users due to over use of canal water in the upstream section. Thus, farmers in the
downstream section have no other choice but to use drainage water for irrigating their crops (Tekinel
et al., 1989).
Yazar and Yarpuzlu (1997) conducted a five-year study in the Lower Seyhan Irrigation Scheme in
Turkey from 1991 to 1995 in order to evaluate the response of cotton and wheat grown in rotation on
a clay soil to drainage water applications with four different leaching fractions (varying from 0.15 to
0.60) as well as salinity build-up in the soil profile. Effect of winter rainfall on salt balance of the soil
profile was also investigated in this study. The results revealed that using drainage water with
salinities varying from 1.26 to 6.26 dS/m for irrigation of wheat did not result in the salinity built up in
the soil profile in the Lower Seyhan Project in Turkey.
The main objectives of this study are to evaluate the yield production and yield loss in relation to
the various salt concentration levels of irrigation water; to investigate the salinity build up in the soil
profile under different irrigation programs; to determine the water use efficiency (WUE) under saline
water conditions, which is a key parameter in water saving program. In addition, to study the effect of
saline supplementary irrigation on leaf stomatal conductance of wheat in the esatern Mediterranean
region of Turkey.
MATERIALS AND METHODS
Experimental site
The field experiment was conducted at the Research Station of the Irrigation and Agricultural
Structures Department of the Cukurova University in Adana, Turkey during 2001/2002 wheat growing
season (November-June, 2002). Descriptions of some physical and chemical characteristics of the
experimental soil are given in Tables 1 and 2, respectively.
As shown in Table 1, the soil of the experimental site is classified as Mutlu soil series (Palexerollic
Chromoxeret) with clay texture throughout the soil profile. Available water holding capacity of the soil
is 256.2 mm in the 120 cm soil profile. Table 2 indicates that soil salinity at planting time is well below
the salinity threshold level for reducing wheat yields of ECe=6.0 dS/m. Wheat is classified as medium
tolerant to soil salinity (Maas, 1986).
75
Table 1. Description of the some physical characteristics of the experimental soil
Soil
Depth
cm
Particle Size
Distribution
(%)
Soil
Texture
Field
Capacity
3
3
(cm /cm )
Bulk
Density
3
(g/cm )
Wilting
Saturation
Point
3
3
(cm /cm ) (cm3/cm3)
Sand
Silt
Clay
0-5
28
21
51
C
42
23.8
51
1.19
5-15
28
21
51
C
42
23.8
51
1.19
15-30
28
21
51
C
42
23.8
51
1.19
30-60
28
19
53
C
45
23.2
54
1.16
60-90
28
18
54
C
44
21.8
55
1.15
90-120
27
19
54
C
42
18.8
50
1.25
Table 2. Description of the some chemical properties of the experimental soil
Cations (me/l)
Depth
(cm)
ECe
(dS/m)
pH
CaCO3
(%)
O.M.*
(%)
0-10
0.335
6.95
5.92
10-20
0.310
6.63
20-40
0.353
40-60
++
++
+
Anions (me/l)
+
-
-2
-
Ca
Mg
Na
K
HCO3
SO4
Cl
1.28
1.48
1.10
0.40
0.10
2.06
0.10
0.92
5.92
1.28
1.66
1.10
0.32
0.08
2.14
0.26
0.77
6.81
6.11
1.14
1.94
1.17
0.35
0.07
2.24
0.40
0.89
0.354
6.93
6.38
0.98
1.48
0.80
0.43
0.05
1.84
0.10
0.83
60-80
0.314
7.15
6.65
-
1.45
1.31
0.44
0.05
2.04
0.34
0.88
80-100
0.324
6.99
7.40
-
1.52
1.09
0.56
0.05
2.14
0.21
0.87
100-120
0.295
6.95
7.45
1.16
0.97
0.57
0.05
1.90
0.12
0.74
*OM:Organic matter
Treatments and experimental desing
Balatilla, a bread variety of wheat (Triticum aestivum L.) was planted on 24 November 2001 at a
row spacing of 12.5 cm, and after plant establishment dikes were constructed around each plot since
border irrigation was used due to close growing nature of wheat crop. Wheat grain yield was
2
determined by harvesting all plants in an area of 8 m in each plot.
Fertilizer applications were based on soil analysis recommendations. All treatment plots received
the same amount of total fertilizer. A compound fertilizer of 20-20-0 was applied at arate of 75 kg N
and 75 kg P2O5 as pure matter per ha at planting. The rest of N fertilizer was applied on February 23,
2002 in the form of ammonium nitrate (26% N) during tillering at a rate of 75 kg N per ha.
The saline water was prepared by mixing fresh water (0.5 dS/m) with sea water (54 dS/m) in order
to obtain an average salinity level of 12 dS/m in a concerete pool with dimensions of 10m x 10 m x 2.5
m at the experimental site. Five salinity levels of irrigation water with ECiw of 3.0, 6.0, 9.0, and 12.0
dS/m (being various dilutions of stock solution in the pool with irrigation canal water) along with canal
water (control) with salinity of 0.5 dS/m were tried in a completely randomised block design with three
replications. In addition, a treatment was included in the study by applying a 10% leaching fraction to
12.0 dS/m treatments after flowering. Thus, a total of 6 treatments were studied. Namely, 0.5, 3.0,
6.0, 9.0, and 12.0 dS/m; and 12.0+10% leaching after flowering stage were condidered. Each
experimental plot was 5 m long and 2.5 m wide.
76
Irrigation, soil water and salinity monitoring
Gated pipes were used for applying water to plots. For mixing saline water and fresh water at
specified salinity level, tanks were utilized at the head of each plot. Flow meters were utilized to
determine the volume of water applied to each plot. The amount of water applied to each treatment
plot was based on replenishing the soil water deficit within the 100 cm soil profile during the irrigation
interval of 14 days to field capacity (Sezen and Yazar, 1996).
Soil water in each experimental plot was measured with a neutron probe (CP Model 503DR
Hydroprobe) as well as by gravimetric sampling at 0.20 m depth increments down to 1.00 m, every
two-week and prior to each irrigation application. A calibration equation developed for the
experimental site was used to calculate the soil water in the profile prior to irrigation. At planting, and
at flowering stage all treatment plots were soil sampled at depth intervals of 0-10 cm, 10-20 cm, 20-40
cm, 40-60, 60-80, 80-100 cm using an auger. The electrical conductivity of the soil samples was
measured on saturation extracts (ECe) with an EC meter.
Water use (ET) of the wheat crop was calculated through the use of water balance equation:
ET = I + P ± ∆S − D
(1)
where ET is evapotranspiration (mm), I irrigation (mm), P precipitation (mm), D deep percolation (i.e.,
drainage, mm), ∆S is change of soil water storage in a given time period (mm), ∆t (days) within the
plant rooting zone. The amount of water above the field capacity is considered as deep percolation in
this study.
3
2
Water use efficiency (kg/m ) was computed as the ratio of grain yield (kg/m ) to water use (m).
Irrigation water use efficiency was determined as the ratio of grain yield for a particular treatment to
the applied water for that treatment. Harvest index (HI) was obtained as the ratio of grain yield (kg/m2)
2
to aboveground biomass yield (kg/m ).
Dry-matter, leaf area
The phenological growth stages were observed weekly throughout the study. For this purpose,
plants in 1.0 m long row section in each replicate for each treatment were randomly selected
representing all the characteristics of its treatment. Occurrences of different growth stages were
monitored on these plants. Plant height measurements were also carried out.
The development of the above-ground portion of the crop was monitored by destructive sampling
during the season. Plant samples consisted of all plants within 0.5 m of a row were taken at two-week
intervals. Leaf area of the samples was measured with an optical leaf area meter.
2
Wheat plants were hand harvested in all treatment plots by cutting all plants in 8 m section of
each plot on June 6, 2002. Then, using a tresher grains were separated from the strarw, and grain
yields were determined.
Stomatal conductance measurements
Stomatal conductance measurements were carried out on five main treatments during the
vegetative growth stage before and after irrigation. Diffusion porometry is based on measurement of
the rate of water vapor loss from a leaf or portion of a leaf enclosed in a porometer chamber and the
resistance is measured. Stomatal conductance is calculated as the inverse of the resistance
measured (Beadle et al., 1986). The measurement is done with an automatic porometer (Li-Cor,
Lincoln, NE, USA, Model Li-1600), that diffuses water vapor. From each treatment fully developed
upper two leaves were taken for measurement. Measurements were carried out during noon time.
The obtained values were calculated twice to reflect abaxial and adaxial leaf surfaces.
MSTATC program (Michigan State University) was used to carry out statistical analysis. Treatment
means were compared using Duncan’s Multiple Range Test (Steel and Torrie, 1980).
77
RESULTS AND DISCUSSION
Rainfall and irrigation
A total of 742 mm of rainfall received during the 2001-2002 wheat growing season was
significantly higher than the long-term average annual rainfall of 630 mm. Table 3 summarizes the
average monthly climate data compared to the long-term mean climatic data for the Lower Seyhan
Plain, where the experiment was carried out. Except the rainfall, other climatic prameters during the
growing season were typical those prevail in the Mediterranean region. Because of the above normal
rainfall in December 2001 during the wheat growing season in the experimental area, wheat was
irrigated twice. The first irrigation application was made on March 22, 2002 and 100 mm of water was
applied to treatments with different salinity levels. Treatment of 12.0 dS/m+ 10% leaching fraction (LF)
received 110 mm. The second irrigation was applied on May 7, 2002 and 80 mm of irrigation water
with different salinity contents were applied to the treatment plots. Treatment of 12.0 dS/m+ 10% LF
received 88 mm of irrigation water. Thus, a total of 180 mm of irrigation water with different salinity
levels were applied to treatments except treatment 12dS/m+10% LF, which received 198 mm of
irrigation water.
Dry matter and grain yields
The data pertaining to effect of varying saline irrigation on wheat crop growth and grain yields, dry
matter yields, water use, water use efficiency, harvest index and 1000-grain weight values obtained
from treatments irrigated with water with different salinity levels are presented in Table 4. As indicated
in Table 4, the average grain yields ranged from 5940 to 6484 kg /ha in the different treatments.
Table 3. Historical monthly mean and growing season climatic data of the experimental area
Climatic Parameters
Nov.
Dec.
Jan.
Feb.
Long-term average (1929-2000)
15.1
11.1
9.9
10.4
Average Temperature (°C)
Rainfall (mm)
67.2
118.1
111.7
92.8
Relative Humidity (%)
63
66
66
66
Wind Speed (m/s)
1.6
1.9
2.2
2.2
47.0
47.3
56.1
Evaporation, Class A Pan (mm) 66.3
2001-2002 Growing Season
13.9
10.7
7.9
12.3
Average Temperature (°C)
Rainfall (mm)
88.1
320.9
109.2
68.1
Relative Humidity (%)
67.4
78.2
66.1
64.7
Wind Speed (m/s)
1.6
1.8
2.1
2.3
36.1
58.9
64.0
Evaporation, Class A Pan (mm) 73.4
-2 -1
273.3
166.9
289.8
359.1
Solar Radiation (MJ m d )
March April
May
June
13.1
67.9
66
2.3
84.9
15.2
21.4
28.0
25.4
25.6
4.8
69
67
66
1.6
1.9
2.5
11 8.6 19 5.6 320.5
14.7
40.3
67.4
2.3
88.9
465.1
16.5
88.8
76.0
1.7
72.5
511.8
21.4
22.0
68.4
2.0
155.2
657.7
26.6
0.8
62.9
2.4
215.5
706.5
Variance analysis of the grain yield data showed that the effect of salinity levels of irrigation water
used in the study on grain yields was not significantly different (Table 4). Therefore, treatments
resulted in similar wheat grain yields in this experiment. This result is expected because wheat was
irrigated twice during the growing season due to significant amount of rainfall received in the study
area. Bernstein (1964), Bhumbla et al, (1964), Kanwar and Kanwar (1969) and Tripathi and Pal
(1980) have reported the reduction in yield of wheat with high saline irrigations. Besides, grain yield,
crop growth and yield attributes are found to vary with sensitivity for salinity. Chauhan and Singh
(1993) reported a remarkable reduction in grain yield started above ECiw 8 dS/m in India. With ECiw 12
and 16 dS/m the grain yield lowered by 21 and 37% respectively. Reduction in grain yield per unit EC
of water from 8 to 16 dS/m was about 4%.
78
Table 4. Grain and dry matter yield, water use and water use efficiency (WUE) data for the treatments
Salinity of
Irrigation
Water
(dS/m)
0.5 (FW)
3.0
6.0
9.0
12.0
12.0+(10%)
Dry
Matter
Yield
(kg/ha)
15063
15230
16210
16341
15216
16915
Grain
Yield
(kg/ha)
Harvest
Index
(HI)
6176
5940
6484
6373
6391
6427
0.41
0.39
0.40
0.39
0.42
0.38
Seasonal
Irrigation
(mm)
Water
Use
(mm)
180
180
180
180
180
198
480
461
496
462
452
445
WUE
3
(kg/m )
1.286
1.288
1.307
1.379
1.414
1.444
1000
Grain
Weight
(g)
45.2
46.1
46.4
45.1
46.2
46.8
Average dry-matter yields varied from 1506 to 1691 g/m2 from the different treatments at harvest
time. However, six different saline irrigation treatments resulted in similar biomass yields. Since wheat
was irrigated only twice during the growing season, and significant amount of rainfall received during
the wheat growing period, salts added to soil with irrigation remained at insignificant level and did not
affect the biomass yield of wheat. Chauhan and Singh, (1993) reposted that drymatter yield declined
only at ECiw12 and 16 dS/m by 18 and 33% respectively, as compared to canal water.
Seasonal water use of wheat in the different treatments ranged from 445 to 496 mm. The amount
of rainfall greater than soil water deficit in the soil profile was considered as deep percolation. Thus,
considerable amount of deep percolation occurred in this particular year, and leached out significant
amount of salts from the profile.
Water use efficiency (WUE) values from the treatments ranged from 1.29 to 1.44 kg/m3. As the
salinity level of irrigation water increased WUE values also increased slightly. However, the WUE
values were not significantly different among the treatments studied. Zwart and Bastiaansen (2004)
viewed the water use efficiency values for major crops and reported the range of WUE for wheat,
3
varying between 0.6–1.7 kg/m throughout the world.
Dry-matter yields obtained from the different treatments varied from 15063 kg/ha in treatment
irrigated with fresh water (0.5 dS/m), to 16915 kg/ha in treatment of 12.0 + (10%) dS/m. However,
there was no significant difference in the dry-matter yield among the treatments.
The evolution of leaf arae index (LAI) under different treatments with time is presented in Fig. 1. As
shown in Figure 1, irrigation water salinity resulted in gradual reduction of LAI. The negative impacts
of salinity on the LAI development started to appear after the flowering stage. The reduction in LAI
ranged from 10.8 to 12.0% lower than the fresh water treatment. However, the differences in LAI
values were not significant among the treatments.
LAI
7
0.5 dS/m
6
3.0 dS/m
5
6.0 dS/m
4
12.0 dS/m
3
12+(10%) dS/m
9.0 dS/m
2
1
0
Jan 1
Feb. 26
March 20
Apr 16
mag 02
Date of Observation
Fig. 1. Evolution of leaf area index (LAI) in different treatments
79
Harvest index (HI), defined as the ratio of grain yield to dry matter yield, values from the different
treatments are given in Table 4. It shows that the harvest index values from the different treatments
varied from 0.38 to 0.42. However, there was no significant difference among the treatments.
Average 1000-grain weight values from the different salinity treatments ranged between 45.1 and
46.8 g. However, 1000-grain weight values obtained from the treatments were not significantly
different. However, Chauhan and Singh (1993) stated that 1000 grain weight was started to decline
from ECiw 2 dS/m onwards progressively but with very low degree.
Soil salinity
Soil salinity profiles resulting from the different salinity treatments are shown in Fig. 2. Soil salinity
profiles were established at planting, at flowering, and at harvest for each treatment studied. As
shown in the Fig. 2, soil salinity at planting varied from 0.27 dS/m in surface soil layers to 0.50 dS/m
in deeper layers. However, soil salinity throughout the profile was very low in the experimental soil.
Soil salinity increased slightly in the surface layer (ECe=0.35 dS/m) in the treatment irrigated with
fresh water. Generally soil salinity increased with salinity content of irrigation water used in the study.
Highest soil salinity was observed in the 0-10 cm soil layer in treatments irrigated with ECw of 12
dS/m and 12 dS/m+10% leaching as ECe=4.3 dS/m. Then soil salinity decreased almost linearly with
increasing depth in the profile. Soil salinity in the 100-120 cm soil layer was 0.8 dS/m in these two
most saline treatment plots. There was no significant difference in soil salinities between these two
treatments. Soil salinity during the wheat growing period did not reach the threshold salinity level of
6.0 dS/m (Ayers and Westcot, 1985).
EC, dS/m
0,0
1,0
2,0
3,0
4,0
5,0
0
Soil Depth, m
20
40
Planting
Flow ering
60
0.5 dS/m
3 dS/m
80
6 dS/m
9 dS/m
100
12 dS/m
12+(10%) dS/m
120
Fig. 2. Soil salinity profiles at planting, flowering and harvest for the treatments
The treatment irrigated with saline irrigation water of 9.0 dS/m resulted in soil salinity of 3.2 dS/m
in the top layer (0-10 cm) and 2.2 dS/m in the 10-20 cm layer. Then soil salinity decreased with
increasing depth. The lowest salinity in the soil profile was observed in the 100-120 cm soil layer with
0.6 dS/m. Soil salinity prior to the flowering growth stage was very similar in all treatments and were
lower than 0.5 dS/m throughout the profile as indicated in Fig. 2. The treatment irrigated with saline
irrigation water of 6.0 dS/m resulted in soil salinity of 2.1 dS/m in the top layer (0-10 cm) and 1.4 dS/m
in the 10-20 cm layer. Then soil salinity decreased with increasing depth. The lowest salinity in the
soil profile was observed in the 100-120 cm soil layer with 0.5 dS/m. The treatment irrigated with
saline irrigation water of 3.0 dS/m resulted in soil salinity of 1.65 dS/m in the top layer (0-10 cm) and
1.1 dS/m in the 10-20 cm layer. Then soil salinity decreased with increasing depth. The lowest salinity
in the soil profile was observed in the 100-120 cm soil layer with 0.4 dS/m.
80
Rainfalls received during the growing season especially prior to flowering stage leached out the
salts from the profile in all treatments studied. Irrigation application after the flowering stage resulted
in increased soil salinities in saline irrigation water treatments since the rainfall received after
flowering stage was not sufficient to leach out salts from the profile. From the research findings, it can
be conclude that saline irrigation water can be used for irrigation of wheat crop in the Mediterranean
region since effective winter rainfalls leach the salts out of the root zone as long as an efficient
drainage system is provided.
Average pH values of the saturation extracts under different treatments at harvest remained
between 7.0 and 8.0 in all plots. There were no significant difference among the treatments with
respect to pH values of the saturation extracts. Thus, pH was not affected considerably by the saline
irrigation water applications.
Highest average sodium absoprtion ratio (SAR) value was determined in the top layer of soil as
9.74 in the treatment irrigated with water of 9.0 dS/m, followed by 12.0 dS/m treatment as 7.53 and
7.11 in the treatment irrigated with 12 dS/m +10% leaching. In general, SAR values increased with
increasing salinity of irrigation water. However, SAR values observed in all treatments did not
constitute a serious threat to wheat growth under the study conditions.
Stomatal conductance, gs
Stomata play a pivotal role in controling the balance between the water loss and carbon gain i.e.
biomass production. Measurements of the size of the stomatal opening or of the resistance to CO2
and water vapor (H2O) transfer between the atmosphere and the internal tissue of the leaf imposed by
the stomata are important in studies of biomass production. This is particularly the case in cropping
situations where it is important to maximize water use efficiency (Beadle et al., 1986).
Average stomatal conductances of wheat leaves measured in different dates under the different
treatments are given in Figure 4. As indicated in Figure 4, stomatal conductance measurements were
started on April 8 and continued until May 17, 2002. Stomatal conductance (upper+lower epidermis)
values on April 8, was highest in 3.0 dS/m treatment followed by 12 dS/m+10% leaching treatment.
-2 The lowest average stomatal conductance was observed in treatment of 9.0 dS/m as 382 mmol m s
1
. A total of 5 mm of rainfall recieved prior to measurements on the same day. On April 12, stomatal
conductances were very similar in all treatments except in 12 dS/m+10% leaching, in which highest
2
value was measured as 839 mmol/m s. Stomatal conductance values decreased in all treatments on
April 15. The highest stomatal conductance was measured in the treatment irrigated with fresh water,
and the lowest was observed in treatment of 12.0 dS/m. On May 3, a total of 2 mm of rainfall was
received before the measurements, stomatal conductances reached their highest values in most
treatments except in the treatment of 3.0 dS/m. Highest stomatal conductance was measured in
treatment irrigated with fresh water followed by 12dS/m+10% LF, and 12 dS/m treatments. On May 7,
80 mm of irrigation water of different salinity content was applied to treatment plots. Average stomatal
conductance values slightly decreased on May 10 as compared to May 3 values. A total of 2 mm of
rainfall was received on May 16. On May 17, slightly decreased on low salinity treatments, and slightly
increased on higher salinity treatments. Zang et al. (1998) evaluated the diurnal variation of stomatal
conductance in China with 600 mm annual rainfall, and stated that midday depression of gs were also
evident in field grown wheat. Xue et al. (2004) explained the gs movement of field grown wheat in the
United States as a feedforward response, which means that stomata sensed the air vapor pressure
directly. Increased water loss through the stomata caused a water potential decline of the guard cell.
In conclusion, there was no well-defined relationship between stomatal conductances and irrigation
water salinities under the study conditions.
81
Stomatal Conductance
(mmol m-2 s-1)
1200
1000
800
0,5
3
600
6
400
9
12
200
0
4-Apr
12+%10
9-Apr
14-Apr 19-Apr 24-Apr 29-Apr
4-May
9-May 14-May 19-May
Date
Fig. 3. Variation of average stomatal conductance values of wheat leaves under the different
treatments
CONCLUSIONS
In the Mediterranean climate, rainfed cereal crops are planted in autumn and harvested in late
spring, relying on the rains during this period for the conclusion of their cycle; the vagaries of rains,
however, often put at risk the final harvest. The response of wheat (Triticum aestivum L.) to different
salinity levels of irrigation water under the Mediterranean climatic conditions was investigated in a
field study at the experimental station of Cukurova University in Adana, Turkey during the 2001-2002
growing season. Saline waters with electrical conductivity values of 0.5 (fresh water), 3.0, 6.0, 9.0,
and 12.0 dS/m were used for irrigation of wheat.
The research results revealed that the effects of salinity levels of irrigation water used in the study
on grain yields as well as dry-matter yields were not significantly different. Since wheat was irrigated
only twice during the growing season, and significant amount of rainfall received during the wheat
growing period, salts added to soil with irrigation remained at a level that did not affect the biomass
yield of wheat.
Generally soil salinity increased with salinity content of irrigation water used in the study. Highest
soil salinity was observed in the 0-10 cm soil layer in treatments irrigated with ECw of 12 dS/m and 12
dS/m+10% leaching as ECe=4.3 dS/m. Then soil salinity decreased almost linearly with increasing
depth in the profile.
3
Water use efficiency (WUE) values from the treatments ranged from 1.29 to 1.44 kg/m . As the
salinity level of irrigation water increased WUE values also increased slightly. However, the WUE
values were not significantly different among the treatments studied.
There was no well-defined relationship between stomatal conductances of wheat leaves and
irrigation water salinities under the study conditions.
Thus, saline irrigation water under the semi arid climatic conditions in the Mediterranean region
can be used for irrigation of wheat crop up to ECw-12 dS/m comparable to control (canal water)
because of effective winter rainfalls leach the salts out of the root zone as long as an efficient
drainage system is provided. The sustainability of this practice is presumably high, due to the limited
amounts of added salts, which can be easily leached out even by a modest precipitation.
82
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84
USE OF SALINE IRRIGATION WATER FOR PRODUCTION
OF SOME LEGUMES AND TUBER PLANTS
**
A. Hamdy *, and Y. G. M. Galal **
* IAM-Bari, Italy
**
Atomic Energy Authority, Nuclear Research Center, Soil and Water Research Department,
Abou-Zaabl, 13759, EGYPT.
A. M. Gadalla
SUMMARY - Effect of irrigation water salinity on growth and production of some legumes, i.e. faba
bean, chickpea, and lentil as well as tuber plants like sugar beet and potatoes was investigated in
lysimeter system under green house controlled conditions using drip irrigation system. Chickpea was
frequently affected by saline water. Number of pods was decreased gradually with increasing water
salinity levels. High levels of salinity negatively affected shoot, root dry matter, seed yield and N
accumulated in shoots and roots. A slight difference in seed N was noticed between fresh water and 9
dS/m treatments. Results showed that high levels of salinity negatively affected seed yield and N
accumulated in tissue of faba bean. Similar trend was noticed with dry matter of lentil. While, shoot-N
was increased at 6 and 9 dS/m. Both leguminous crops were mainly dependent on N2 fixation as an
important source of nitrogen nutrition. Under adverse conditions of salinity, the plants gained some of
their N requirements from the other two N sources (Ndff and Ndfs). Application of the suitable
Rhizobium bacteria strains could be beneficial for both the plant growth and soil fertility via N2 fixation.
Sugar percentage in sugar beet tubers was increased with increasing saline irrigation water under
different nitrogen strategies. It was slightly increased when N applied at full dose than the splitting
one. Addition 75% of water requirements also resulted in high percentage of sugar at all levels of
saline irrigation water either N added full dose or splitting doses. Exposure of two varieties of potato to
different water salinity levels indicated that total yield, on the base of fresh weight, of Spunta or Nicola
tubers was slightly increased by increasing water salinity level up to 6 dS/m. In general, the overall
means showed the superiority of Nicola variety over Spunta variety. Also, addition of organic compost
in different rates has some significant effects on starch content in tubers. In this respect, gradual
2
increase of tuber starch with increasing salinity levels was noticed with addition of 2.6 kg/m organic
matter. In general, Spunta variety showed some superiority in tuber starch over those of Nicola variety
tuber.
Key words: Drip irrigation, Legumes, N management, Organic amendment, Saline water, Tubers,
Water regime, Yield
INTRODUCTION
Salinity is currently one of the most severe abiotic factors limiting agricultural production. In
addition, water demand was increased due to increasing the population and improvement of living
standards (Paranychianakisa and Chartzoulakis, 2004). In regions affected by water scarcity such as
the Mediterranean basin, water supplies are already degraded, or subjected to degradation
processes, which worsen the shortage of water (Chartzoulakis, et al., 2001; Attard, et al., 1996).
Therefore, attention had been paid on reusing the low quality water resources in irrigation. In this
respect, types of salinity, categories of salt-affected soils, water quality and water classification has
been excellently reviewed by Aly (2004).
At high substrate salinity, growth depression may originate from inhibited nutrient uptake, transport
and utilization in the plant (Lauchli and Epstein, 1990). Legumes have the capacity to derive a
considerable proportion of their nitrogen requirement from the atmosphere through symbiosis with
Rhizobium. The amount of N2-fixed by legumes-rhizobia symbiosis is greatly influenced by many
environmental factors such as temperature, water, soil pH, oxygen content or soil nutrient status
(Kvien and Ham, 1985). Saline habitats are N-poor, therefore the N input is very important in these
environments (Zahran, 1997). One of the sources of N input in saline soils is N2-fixation (Whitting and
Morris, 1986). Higher rates of N2-fixation in saline environment compared to non-saline and
85
agricultural soils were reported (Wollenweber and Zechmeister-Boltenstern, 1989). The low oxygen
tension in saline soils may favour the process of N2-fixation, but the diffusion of gases may be
impaired at a higher density and water regime in saline soil, an effect that might reduce N2-fixation
(Rice and Paul 1971).
Sugar beets are salt resistance owing to osmotic adjustment. Physiological adjustments enable the
plant in a saline environment to maintain the turgor potential at a similar level as under non-saline
conditions. Moisture stress reduced the rate of sucrose concentration to a greater extent in the low-N
plants than in the high-N plants (Loomis and Jr. Worker, 1963). Water stress several weeks before
harvest of fall-planted beets reduced root yields but increased sucrose percentage. Limited moisture
stress to increase sucrose concentration without reducing gross sugar yield can be a profitable
practice.
Nitrogen (N) management plays an important role in sugar beet production. However, in sugar
beets, managing N for a high-yielding and high-quality crop can be difficult. Sugar beet growers can
further improve the efficiency of N applications by applying N in multiple applications.
Potato (Solanum tuberosum L.) is one of the most important vegetable crops in Egypt, which lie on
the head of Egyptian exports menu and one of the national income resources. In the past, it was
believed that potato could only be planted in loam soil cultivated, but recent studies showed that there
is a possibility of potato production under sandy soil conditions, with high tubers quality (AbouHussein, 1995). Regarding salinity tolerance of potatoes grown in sandy soils, Gong et al. (1996)
indicated that irrigating potato plants once a day with saline water reduced plant growth as compared
with 3 or 6 irrigations a day.
This context mainly focused on the effect of irrigation water salinity on growth and nutritional
factors and physiological impacts that limiting the development of different leguminous and tuber
crops.
MATERIALS AND METHODS
Different crops either leguminous, i.e. chickpea, faba bean and lentil or tubers such as sugar beet
3
or potatoes were cultivated under greenhouse conditions. PVC Lysemeter with volume 0.103 m
(diameter 0.54 m and depth 0.45 m) was used.
A clay textured soil with pH, 8.11; EC, 0.542 dS/m; OM, 2.67%; available water 9.7%, field
capacity, 29.7% was used.
Experimental layout
Leguminous crops
Chickpea seeds (Cicer aeritinum cv. Giza 1) were planted and treatments were randomly arranged
in 16 containers, with additional batch of treatments were carried out with wheat plant (16 containers),
used as a reference crop for quantifying the potential of N2-fixation through the application of isotopic
dilution technique. Four salinity levels of irrigation water were used in the experiment namely 1.0
dS/m (freshwater as a control) and three levels of saline water 3, 6 and 9 dS/m. Peat-based inocula of
Rhizobium leguminosarum biovar vicea, ICARDA 36 was used for inoculation of the tested crop. The
9
-1
15
15
inoculum has 8x10 cells g peat. N-labelled ammonium sulfate, ( NH4) 2 SO4 5 % atom excess, as
-1
N-fertilizer was applied at rate of 20 kg N ha .
Similarly, the seeds of faba bean (Vicia faba cv. Giza 388) and Lentil (Lens culinaris cv. Giza 15)
were cultivated under the abovementioned 4 levels of saline water. 15N-labelled ammonium sulfate,
15
-1
( NH4) 2 SO4 10 % atom excess, as N-fertilizer was applied at rate of 20 kg N ha . Wheat crop
(Triticum aestivum L. Sakha 69) was used as a reference crop for quantifying N derived from air by
the two leguminous crops. This reference crop was fertilized with 100 kg N as (15NH4) 2 SO4 (1% 15N
a.e.). Peat-based inocula of Rhizobium leguminosarum biovar vicea, ARC 207 F (Faba bean) and
86
ARC 203 L (Lentil) were used for inoculation of the tested crops. The inoculum has 8 x 10-9 cells g-1
peat.
Tuber crops
•
Sugar beet
An experiment was conducted under greenhouse conditions. The set-up consists of 64 lysimeters
(4 saline irrigation water treatments, 2 water regimes, i.e. W I=100% and W II=75% from field capacity,
2 nitrogen, i.e. NI=one dose and NII= split doses, and 4 replicates).
Sugar Beet (Beta vulgaris L.), Variety GIADA, provided by the International Agronomic
Mediterranean Institute, Valenzano, Bari – Italy, from KWS Company, was used as indicator plant.
Four qualities of irrigation water were used in the experiment: 0.98 dS/m (Fresh water as a control),
15
and three saline irrigation water treatments 4, 8 and 12 dS/m. Labeled ( NH4) 2 SO4 (5 % a.e.) was
-1
added to all lysimeters of Sugar Beet crop at rate of 150 kg N ha . Nitrogen fertilizer was divided into
two treatments, the first applied as single dose, 112.5 Kg N/ha, while the second treatment is split into
two equal doses of 56.25 Kg N/ha.
• Potatoes
The set-up consists of 90 Lysemeter (3 saline irrigation water treatments, 3 organic matter, 2
varieties of potatoes (Spunta and Nicola), and 5 replicates. The saline water was prepared by mixing
fresh water (0.91dS/m) with seawater (46dS/m) at certain ratios. The electrical conductivity (EC)
values of saline water were 0.91dS/m (fresh water control), 3 and 6 dS/m.
Three rates of organic matter have been used, OM1, OM2 and OM3 with quantities of 0, 600 and
2
1200g equivalent to 0, 2.6 and 5.2 kg/m , respectively. The chemical analysis of organic matter is:
Organic C, 35%; Organic N, 1,2 %; C/N ratio, 29; HA+FA, 8%; Zinc, 80 ppm; salinity, 20 dS/m.
Potato (Solanum tuberosum), with two varieties (Spunta & Nicola), provided by the International
Agronomic Mediterranean Institute, Valenzano, Bari – Italy, from HZPC Company was cultivated. The
cultivated varieties were fertilized with nitrogen which applied at a rate of 200 kg N /ha as ordinary
urea (NH2CONH2) and labeled urea (10% a.e.).
All leguminous and tuber crops were also fertilized with the recommended doses of phosphorus
and potassium fertilizers. The standard methods were used for soil and plant analyses according to
Page et al., (1982). Isotope dilution concept was applied for quantification of different portions of
nitrogen used by plants (Hardarson et al., 1991).
Statistical analysis
All data were subjected to ANOVA analysis followed by Duncan's multiple range test (DMRT)
according to SAS software program (1987).
RESULTS AND DISCUSSION
Legume crops
Chickpea
Yield and growth components of chickpea as influenced by salt stress are listed in Table 1. It is
clear that the number of pods decreased gradually with increasing salinity of irrigation water. Raising
salinity level resulted in a relative reduction in the number of pods by 10 %, 24% and 31% for 3, 6 and
9 dS/m, respectively. Shoot and root dry matter yield showed a remarkable decrease with increasing
salinity level up to 9 dS/m as compared to the fresh water control, but it doesn’t vary so much.
Concerning the seed yield, the data show that the total seed yield sharply decreased with increasing
87
salinity levels. For instance, the relative reduction was by 67% caused by rising up to 3 dS/m. The
highest reduction was noticed with the high EC unit of 9 dS/m, where 89% of the total seed yield of
fresh water treatment was reduced. A similar trend, but to a lesser extent, was recorded with the
weight of 100-seed yield. Summation of dry weight (total seed yield + shoot + root) of chickpea plants
indicates a gradual reduction with gradual increase in water salinity, by about 36%, 45% and 56% for
3, 6 and 9 dS/m. From the above-mentioned results, we can conclude that the growth and yield
components of chickpea plants were adversely affected by salinity stress.
Table 1. Number of pods and dry weight of different parts of chickpea plants as affected by the salinity
level of irrigation water
Salinity
(EC)
No. Of pods
Dry weight (g/Li)
Shoot
Root
D.W.
Sum.
24.2 a
147.2 a
50.0 a
379.2
-
59.8 b
21.4 a
142.8 a
41.8 ab
244.4
35.5
24
35.2 c
9.8 b
136.4 a
35.6 b
207.2
45.4
212 d
31
19.2 d
5.8 c
113.3 b
35.0 b
167.5
55.8
258.5
22
74.1
15.3
135.0
40.6
249.6
45.6
Seeds
No./Li
R.D.
(%)
Total
100 seed
F.W
309 a
-
182 a
3 dS/m
277 b
10
6 dS/m
236 c
9 dS/m
Average
R.D.
(%)
Means in the same column followed by the same letter are not significantly different at P ≥ 0.05.
It is documented earlier (Singh and Saxena 1999) that salinity causes nutritional imbalances and
restricts water availability to plants and causes physiological drought, adversely affecting seed yield.
Saxena and Rewari (1992) found that the increases in salt concentration not only adversely affected
the percentage germination of seeds of chickpea cultivars but also delayed their germination at lower
levels of salinity, whereas at higher concentrations the percentage germination and radical length
were reduced. The mean tolerance index (MTI) estimated for chickpea cultivars grown under EC of 2,
4, 6 and 8 dS/m (Field study, Dua, 1992) indicates that although the germination percentage in
chickpea was not affected up to EC of 8 dS/m, sensitivity to salinity increased as the plants grew.
Other authors have also reported that chickpea was less sensitive to salinity at germination than at
later growth stages (Sharma et al., 1982). Considering seed yield, Dua (1992) verified that the
adverse effect of salinity on seed yield/plant results mainly from a reduction in the number of
pods/plant and the number of seeds/plant rather than in 100-seed weight. Thus, this indicated that
plants were more sensitive to salinity at seed setting (flowering) than at the maturity stage.
Faba bean
As presented in Table 2, the salinity levels did not affect the number of pods of faba bean
significantly. The data show a relative increase in the number of pods by 8% and 13% when saline
water of 3 dS/m and 6 dS/m, respectively, was used. This result may give evidence that faba bean is
somewhat tolerant to experimental salinity levels of water. At the higher level (EC 9 dS/m), the
number of pods tended to decrease as compared to other salinity levels, but is still identical to that of
the fresh water control. In other words, the production of pods is not affected by increasing salinity of
irrigation water. In contrast, high EC units negatively affected the total and 100-seed yield. It means
that high EC units affected faba bean. It seems also that faba bean plants is not affected by the lower
level of salinity, whereas the seed yield was identical in fresh water and 3 dS/m. A similar trend was
noticed with either shoot or root dry weight, indicating the inhibition of growth by increasing water
salinity. The overall average of relative reduction of faba bean total dry weight (seeds + shoot + root)
resulted in 15% and 22% reduction, as affected by 6 and 9 dS/m salinity, respectively.
88
Table 2. Number of pods and dry matter accumulated in different parts of faba bean plants irrigated
with saline water
No. of pods
Salinity (EC)
Dry weight (g/Li)
D.W.
Sum.
R.D.
(%)
44.2 a
317.8
-
183.5 a
38.2 a
320.6
+ 0.88
77.0
151.0 bc
31.0 a
269.2
- 15.3
79.2 a
82.2
138.4 c
30.1 a
247.7
- 22.1
90.9
83.3
162.0
35.9
288.8
- 12.2
Seeds
No./Li
R.D.
(%)
Total
100
seed
Shoot
Root
F.W
40 a
-
98.4 a
87.4
175.2 ab
3 dS/m
43 a
+8
98.9 a
86.4
6 dS/m
45 a
+ 13
87.2 a
9 dS/m
40 a
-
Average
42
7
Means in the same column followed by the same letter are not significantly different at P ≥ 0.05.
In a greenhouse experiment, faba bean was found to be sensitive to the high level of NaCl (1000
ppm) were its dry weight of shoot and root was decreased (El-Fouly et al., 2001). Hajji et al., (2001)
+
explained that growth inhibition of bean was associated with excess accumulation of Na in leaves
+
++
and attributed to depletion of K and Ca in this organ. This suggests that Cl in the medium inhibited
the adsorption of essential nutrients. Thus, it appears that these elements were limiting for growth in
+
++
the presence of NaCl because salinity probably inhibited the transport of K and Ca from roots to
+
shoots. In short, under saline conditions, growth is primarily limited by osmotic not by excessive Na
accumulation. The results obtained in our study show that despite the particular/notable increase in
the number of pods with increasing salinity level, the overall average of dry matter accumulation
tended to decrease. This finding was confirmed by the reduction in life cycle long of faba bean plants
with salinity level (Fig.1).
140
Faba bean
Plant Hieght(cm)
120
100
Chickpea
Lentil
80
60
40
20
0
20
40
60
80 100 20
40
60
80 100 20
40
60
80 100
Time period
FW
3
6
9
Fig. 1. Changes in plants height with times as affected by salinity levels of irrigation water
89
Lentil
Lentil is known to be sensitive or moderately tolerant to salt stress. The effect of EC units of irrigation
water on growth components is reported in Table 3. Dry weight of pods revealed the sensitivity of
lentil plants to salinity. The decline in pod dry weight was recorded even with the lowest salinity level
(3 dS/m). The increase in salinity was followed by decreasing dry weight of pods by 21%, 41% and
54% for 3, 6 and 9 dS/m, respectively, as compared to the fresh water treatment. A similar trend was
observed with shoot and root dry weight and seed yield of lentil plants. The summation of plant dry
weight (shoot + root + seed) indicated a sharp decrease with increasing salinity up to 9 dS/m, by 32%
from those recorded with fresh water treatment. Our results are in accordance with those reported by
Yasin and Zahid (2000) who found that lentil crop was sensitive even at low level of salinity. Similarly,
they found a linear decrease in shoot biomass, of 55% and 85%, respectively, at 4 and 8 dS/m salinity
levels. Under greenhouse conditions, lentil dry weight was higher at 3.1 dS/m than at 4.3 and 6 dS/m
salinity levels (IAEA, 1995). In a two-year field experiment conducted under Bangladesh conditions,
lake water of an EC ranging from 1.5 to 4.5 dS/m was used for irrigation of lentil crop. The yield of
lentil irrigated with lake saline water was found to be lower as compared to average national yield
recorded under Bangladesh conditions (Rahman, IAEA 1995). Result of screening experiments of
lentil conducted in greenhouse conditions showed that lentil varieties can with stand various levels of
soil and/or water salinity from 0.63 to 6.0 dS/m (IAEA, 1995).
Table 3. Effect of changes in EC units on pod weight, dry matter accumulation in different lentil parts
W. Of pods
Dry weight (g/Li)
100
seed
Shoot
Root
D.W.
Sum.
R.D.
(%)
51.5 a
3.0 a
68.0 a
26.6 b
146.1
-
-20.8
38.0 b
2.6 b
67.9 a
33.6 a
139.5
-4.5
32 c
-41.4
24.4 c
2.0 c
68.1 a
17.2 c
109.7
-24.9
9 dS/m
25 d
-54.4
15.0 d
1.6 d
68.5 a
16.0 c
99.5
-31.9
Average
39
-38.9
32.2
2.3
68.1
23.4
123.7
-20.4
Salinity (EC)
Seeds
(g/Li)
R.D.
(%)
Total
F.W
54 a
-
3 dS/m
43 b
6 dS/m
Means in the same column followed by the same letter are not significantly different at P ≥ 0.05.
Portions of Nitrogen Derived from Different N-sources
Chickpea
In this part of the present study, we aimed at applying the stable heavy isotope of nitrogen N-15 to
distinguish the different sources of nitrogen derived to the chickpea plants and to estimate exactly
how much N could be compensated by the different sources. In this respect, the portions of N derived
from air, fertilizer and soil are presented in Table 4.
15
The obtained data showed a slight variation in N atom excess of chickpea straw with salinity
15
levels. A remarkable decrease in the percent of N atom excess was noticed in the case of chickpea
15
seeds as affected by gradient/gradual increase in salinity levels. These percentages of N a.e., were
significantly lower than those recorded with wheat as a reference crop used for quantifying the
biological nitrogen fixation (BNF) when applying the isotope dilution (A-value) technique.
The calculation of the percentage and absolute values of N derived from chemical fertilizer added,
showed slight increase with 3, 6 and 9 dS/m treatments, while they were notably higher than the fresh
water control, when straw-N was considered. In contrast, seed-N derived from fertilizer tended to
decrease with increasing water salinity levels. These results indicate that most of the fertilizer N yield
was accumulated in straw of chickpea than seeds. Generally, the portion of N derived from fertilizer to
either straw or seeds doesn’t exceed 12 % of the total N uptake.
90
The opposite was observed with the fraction of N derived from fixation, whereas more than 80%
and 70% of the nitrogen accumulated by straw and seeds, respectively derived from air. Portion of
N2-fixed in straw of chick-pea decreased with the level of 3 dS/m as compared to the fresh water
control, then it tended to increase with both 6 and 9 dS/m treatments but is still lower than fresh water.
Considering the N2-fixation by seeds, the data indicate stability of % Ndfa with increasing salinity,
except the treatment of 6 dS/m where it decreased with respect to other treatments and even the
control. Absolute figures of N fixation revealed that the relationship of Rhizobium leguminosarum –
chickpea symbiosis is obviously affected by the adverse conditions of saline water used. In this
respect, Saxena and Rewari (1992) explained that symbiotic performance in saline soil depends on
the salt-tolerance of both the host and the micro-symbiont. We agree with this conclusion since our
results indicated a good performance of chickpea, Rhizobium symbiosis, under salinity conditions
given. The reduction in the quantities of N2-fixation with increasing salinity seems to be related to the
reduction in plant growth (Kumar and Promila, 1983), disturbed metabolism, and imbalanced nutrient
acquisition (Kawasaki, et al., 1983).
Soil-N came to the next as a fraction of nitrogen demand. It increased with increasing water salinity
levels. This fraction may compensate the reduced quantities of N2 derived from air under high level of
salinity. In other terms, under adverse conditions, which may reduce the potential of N2 fixation, the
plant turned to depend on other N fractions like the Ndf soil.
From the above-mentioned data, it may be concluded that chick-pea plants were dependent on the
different N sources in the following order:
Ndfa > Ndfs > Ndff
Also, it may be stated that the unsuitable abiotic conditions that inhibited Pfix could push the grown
plant to profit from other N sources to avoid N-nutrition disorders.
Table 4. Nitrogen derived from air (Ndfa), fertilizer (Ndff) and soil (Ndfs) in chickpea straw and seeds
as affected by salinity conditions
Treatment
N a.e.
Nitrogen sources
Ndfa
g/Li
%
g/Li
Straw
0.17
2.53
82.1
0.28
1.49
62.8
0.35
2.09
70.5
0.31
1.87
72.24
Seeds
0.14
1.18
71.28
0.16
1.46
71.0
0.08
0.70
67.1
0.04
0.48
72.87
Reference crop
Straw
0.82
0.52
0.86
1.09
Seeds
1.81
1.62
1.86
1.57
-
Ndff
15
%
F.W.
3 dS/m
6 dS/m
9 dS/m
0.581
0.590
0.596
0.598
5.62
11.8
11.92
11.96
F.W.
3 dS/m
6 dS/m
9 dS/m
0.431
0.402
0.386
0.310
8.62
8.04
7.72
6.20
F.W.
3 dS/m
6 dS/m
9 dS/m
0.695
0.699
0.772
0.791
69.5
69.9
77.2
79.1
F.W.
3 dS/m
6 dS/m
9 dS/m
0.682
0.657
0.605
0.597
68.2
65.7
60.5
59.7
Ndfs
%
g/Li
12.33
25.41
17.60
15.80
0.38
0.60
0.52
0.41
20.1
20.96
25.18
20.93
0.33
0.43
0.26
0.14
30.5
30.1
22.8
20.9
0.36
0.22
0.26
0.29
31.8
34.3
39.5
40.3
0.85
0.85
1.21
1.06
91
Faba bean
The data of N derived from the different sources and taken up by faba bean straw and seeds,
(Table 5) show a trend similar to that observed with chickpea plants-N derived from fertilizer was
negatively affected by increasing salinity levels. % Ndff didn’t vary so much as in straw but drastically
decreased in seeds at the highest (6 and 9 dS/m) levels of water salinity. In the same time, faba bean
plants take up a reasonable amount of nitrogen from soil. This component was higher under low
levels of salinity than under the highest ones. More Ndfs was found in seeds as compared to straw-N.
Nitrogen derived from air (Ndfa) seems to be the main source of N utilized by both straw and seed
organs. This source of N nutrition compensated about 70% and more than 80% of the N needed for
faba bean demand. Also, N2-fixation by seeds was higher, to some extent, than by straw. This fraction
reflects that faba bean was tolerant to levels of 3 and 6 dS/m when N2-fixed by seed was considered.
Table 5. Nitrogen derived from air (Ndfa), fertilizer (Ndff) and soil (Ndfs) in faba bean straw and seeds
as affected by salinity conditions
Nitrogen sources
Treatment
Ndff
15
N a.e.
%
F.W.
3 dS/m
6 dS/m
9 dS/m
0.611
0.621
0.631
0.640
12.22
12.42
12.62
12.80
F.W.
3 dS/m
6 dS/m
9 dS/m
0.605
0.501
0.298
0.210
12.1
10.02
5.96
4.20
Ndfa
g/Li
Straw
0.45
0.49
0.33
0.41
Seeds
0.61
0.50
0.25
0.11
Ndfs
%
g/Li
%
g/Li
60.97
60.84
68.74
70.29
2.22
2.39
1.83
2.27
26.81
26.74
18.64
16.91
0.98
1.05
0.49
0.55
59.69
63.82
74.52
81.62
2.99
3.21
3.10
2.00
28.21
26.16
19.52
14.18
1.41
1.31
0.81
0.35
In this respect, Cordovilla et al. (1995) stated that the host tolerance appeared to be a major
requisite for nodulation and N2 fixation of faba bean cultivars grown under salt stress. They also found
that some cultivars have the ability to sustain nitrogen fixation under saline conditions (salt tolerant
genotype). The absolute value of N2 fixed by faba bean seeds was higher than those recorded for
chickpea plant suggesting the specific Rhizobium-host relationship. In conclusion, faba bean as well
chickpea are mainly dependent on N derived from fixation for offering/meeting its nitrogen
requirements. Nitrogen derived from soil came next and followed by nitrogen derived from fertilizer.
15
Also, from the obtained data of N analysis, it is clear that N2 fixation potential should take place
(should be part of) in the program of integrated plant nutrition systems and soil fertility improvement
especially under adverse conditions of salinity stress. Similarly, may I have the chance to advise the
properly selection of both Rhizobium bacteria strains and the suitable host plant tolerant to salinity
stress.
Lentil
The data in Table 6 present the effect of salt stress on nitrogen derived from fertilizer, air and soil
and taken up by straw and seeds of lentil plants. The effect of water salinity on fertilizer-N derived to
straw was unclear. In contrast, the decrease in the amount of N derived from fertilizer and assimilated
by lentil seeds was noticeable. Our results, to some extent, are in agreement with those reported by
Rahman (1995) who found that the percentage of N derived from fertilizer to lentil seeds does not
exceed 12% under irrigation with normal water, but tended to decrease when lake saline water (10
dS/m) was applied. Soil-N derived to lentil plants ranged from 6% to 28% as affected by salinity
levels. The highest percentage of soil-N was obtained with 3 dS/m and 6 dS/m for straw and seeds,
respectively. It seems that lentil plants grown under salinity stress was more dependent on soil-N than
fertilizer-N.
92
Concerning the N2-fixation by straw and seeds of lentil, the data show a negative response to
gradient increase in water salinity, especially in seed-N. Seeds were mainly dependent on N derived
from air since it accounted for 87% and tended to decrease with increasing salinity levels. The portion
of N2 fixed obtained in the present study is in agreement with the value reported earlier by Rahman
(1995). It is clear, that the improvement of lentil growth, in general, is attributable to fixation of
atmospheric N2 by lentil due to the application of the appropriate Rhizobium strains. As mentioned
above, we also advise the application of inoculation technology to improve both the soil fertility and
plant growth especially under the adverse saline conditions.
Table 6. Nitrogen derived from air (Ndfa), fertilizer (Ndff) and soil (Ndfs) in lentil straw and seeds as
affected by salinity conditions
Treatment
Ndff
15
N a.e.
%
F.W.
3 dS/m
6 dS/m
9 dS/m
0.591
0.651
0.663
0.671
11.82
13.02
13.26
13.42
F.W.
3 dS/m
6 dS/m
9 dS/m
0.342
0.310
0.287
0.285
6.84
6.20
5.74
5.70
Nitrogen sources
Ndfa
g/Li
%
g/Li
Straw
0.16
0.16
62.24
0.17
0.17
58.4
0.22
0.22
67.16
0.20
0.20
68.85
Seeds
0.16
0.16
87.47
0.11
0.11
77.62
0.05
0.05
75.52
0.03
0.03
73.06
Ndfs
%
g/Li
25.94
28.04
19.58
17.73
0.34
0.37
0.32
0.26
5.69
16.18
18.74
21.24
0.16
0.29
0.18
0.12
Sugar beet
Sugar % and yield (kg/h)
Sugar % and yield (kg/h) as affected by different water salinity, N as added at one time or splitting
and irrigation water percent (100 or 75% of field capacity) were presented in Table 7. Generally, the
data indicate that sugar % increased with increasing salinity levels of irrigation water under both NI
and NII treatments. It seems that sugar% was higher in case of NI than NII under different salinity
levels, when W I was concerned. Opposite direction was noticed with W II water treatment.
Data recorded in Table 7 show that sugar yield (kg/ha) increased by increasing water salinity. The
increment of sugar yield was (8.3 and 7.7%) under application of N as one time and irrigation by
saline water (4 and 12 dS/m), respectively, comparing with FW, under W I treatment. While in case of
NII the rate of increase was (13.2, 11.5 and 33.1 %) for (4, 8 and 12 dS/m), respectively compared to
fresh water treatment. At the same time, irrigating sugar beet plants with 75% of water field capacity
also lead to a remarkable increase in sugar yield either under NI or NII where the increment of sugar
yield in case of NI was (24.7, 52 and 39%) for (4, 8 and 12 dS/m of water salinity), respectively
comparing to FW treatment. The same trend was noticed in case of NII but to somewhat higher extent.
Significant variation between treatments was presented in Table 8.
Our results are in harmony with those obtained by El-Hawary (1990) who found a significant
increase in sugar yield per plant due to nitrogen application. He added that, the N application at rate
of 90 kg N/feddan after 40 days from sowing date (N3-treatment) gave the highest average of sugar
yield per plant. These results might be attributed to the favorable effect of nitrogen on root volume and
fresh weight of root / plant.
Wiesler et al. (2002) reported that increasing fertilizer N rates reduce sucrose concentration and
sugar yield. Although, we did not apply different doses of N fertilizer but only split the recommended
dose, we believe that this technique has the advantage to save N-fertilizer and in the same time offers
preferable conditions, in combination with water regime, to remarkable production of sugar.
93
Table 7. Effect of salinity levels, N doses and water percent on sugar yield (% and kg/ha) of sugar
beet plants
Salinity
levels
FW
4 dS/m
8 dS/m
12 dS/m
Average
WI
(%)
kg/ha
NI
NII
5886.1
5192.2
6375.3
5878.6
5788.1
5787.9
6340.2
6912.2
6097.4
5942.7
NII
14.0
16.3
17.8
20.4
17.1
NI
16.0
17.4
19.0
21.2
18.4
W II
(%)
NI
13.7
15.3
18.8
19.6
16.9
NII
15.7
18.2
20.5
23.3
19.4
kg/ha
NI
NII
4753.4
6366.0
5928.1
6745.1
7226.0
7604.4
6607.5
7717.2
6128.7
7108.2
Table 8. Summary of ANOVA –Significance of sources of variation and variance of error of studied
characters for plant root
Sources of variation
Water treatments (W)
Water salinity level (S)
Nitrogen (N)
Interaction W * S
Interaction W * N
Interaction N * S
Interaction W * N * S
Error
D.F.
1
3
1
3
1
3
3
60
Sugar content Sugar yield
%
(t/ha)
ns
**
Ns
Ns
**
Ns
ns
0.8166
*
*
ns
*
**
*
**
0.1348
Potatoes
•
Total yield of tuber on the base of fresh weight (t/ha)
As presented in Table 9, the total yield of Spunta tubers was slightly increased by increasing water
salinity level up to 6 dS/m. Similar trend was noticed when organic addition rate concerned. Nicola
tubers showed similar trend as those of Spunta variety, but the increments affect by salinity and
decrements caused by addition of organic matter were much remarkable than in case of Spunta
variety. In general, the overall means showed the superiority of Nicola variety over Spunta variety.
Table 9. Effect of water salinity and organic matter levels on total yields tuber fresh weight (t/ha) of
Spunta and Nicola potatoes varieties.
94
Organic
Matter Level
2
(kg/m )
F.W
0
2.6
5.2
Mean
40.0
41.4
39.8
40.4
0
2.6
5.2
Mean
47.6
44.8
42.4
44.9
Water salinity level (dS/m)
3
Spunta
42.2
41.8
40.7
41.6
Nicola
50.8
45.6
44.9
47.1
6
Mean
42.9
44.2
42.7
43.3
41.7
42.5
41.1
52.4
46.3
46.1
48.2
50.3
45.6
44.4
Concerning the yield and tuber size distribution, Porter et al. (1999) reported that, the yield
increases in response to the amended treatments (green manure) may be due to increased
availability and/or changes in soil bulk density, water stable aggregates or other soil physical
properties. The soil amendment treatments increased soil nutrient concentrations and aggregation.
Also supplemental irrigation increases tuber size during the drier growing season. Maintaining soil
water after tuber initiation increased the percentage yield of tuber than 5.7cm in diameter. Soil
amendment treatments (green manure) significantly increased tuber size. These results are
sometimes on line with our results of tuber distribution.
Iqbal et al. (1999) studied the yield response of potato to planned water stress; the results
obtained showed that, the timing of water stress influenced the tuber yield. The stress imposed at
ripening stage caused the lowest reduction in yield whereas that imposed at early development
caused the greatest yield reduction followed by the tuber formation stage.
•
Starch content (g/100g FW)
Increasing water salinity level up to 3 and 6 dS/m induced relative decrease in Spunta starch
2
under 0 organic matter by about 11.5 and 14.1%, respectively (Table 10). Addition of 2.6 kg/m
2
organic matter had decreased the tuber starch, except the treatment of 5.2 kg/m organic matter
under 6 dS/m level where the starch was vigorously increased. Starch in Nicola tuber under noorganic amendment, was decreased with increasing salinity level up to 3 dS/m, and then increased
2
with increasing salinity to 6 dS/m. Similar trend was noticed with 5.2 kg/m organic matter level.
2
Gradual increase of tuber starch with increasing salinity levels was noticed with addition of 2.6 kg/m
organic matter. In general, Spunta variety showed some superiority in tuber starch over those of
Nicola variety tuber.
Our results of starch are in agreement with those obtained by Silva et al. (2001). Starch level in
two potatoes (S.tuberosum and S.curtilobum) was constant with salinity levels (0, 25, 50, 75 and 100
-1
mmoll NaCl). The starch levels in both varieties of potatoes (S.tuberosum and S.curtilobum)
remained constant under all salt levels. Also, organic solutes such as soluble carbohydrates have
+
been suggested to play an important role as osmoprotectants counteracting the toxic effects of Na
and Cl in the shoots under salt stress (Evers et al., 1997).
Table 10. Effect of water salinity and organic matter levels on starch (g/100g FW) of Spunta and
Nicola potatoes varieties
Organic Matter Level
(kg/m2)
F.W
0
2.6
5.2
Mean
17.6
15.4
14.7
15.9
0
2.6
5.2
Mean
13.8
10.7
15.4
13.3
Water salinity level (dS/m)
3
6
Mean
Spunta
14.9
14.3
15.6
15.4
13.9
14.9
13.6
16.0
14.8
14.6
14.7
Nicola
11.3
14.9
13.3
12.8
14.6
12.7
12.6
14.9
14.3
12.2
14.8
CONCLUSION
Results obtained in this study confirm the reuse of low quality irrigation water mainly saline one,
which may overcome the gab between water charge and requirements for agricultural practices. As
shown above, the use of saline water in irrigation of some salt-tolerant plants may result in
economical production of such economical legumes and/or tuber crops. The application of stable
95
isotope in such studies may help us to understand the physiological impacts of plants imposed to salt
stress and gave us a clear picture about its response to such adverse conditions.
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97
SEA WATER STRESS AFFECTS MITOCHONDRIAL PROLINE OXIDATION
BUT NOT ALTERNATIVE OXIDASE ACTIVITY
IN DURUM WHEAT GERMINATING SEEDLINGS
,
,
,
M.N. Laus*, Z. Flagella* ** , D. Trono***, M. Soccio* ***, N. Di Fonzo*** and D. Pastore* **
*Dipartimento di Scienze Agroambientali, Chimica e Difesa Vegetale, Facoltà di Agraria,
Università di Foggia, Via Napoli 25, 71100 Foggia, Italy
**Centro di Ricerca Interdipartimentale BIOAGROMED, Via Napoli 52, 71100 Foggia, Italy
***Istituto Sperimentale per la Cerealicoltura – C.R.A., SS 16 Km 675, 71100 Foggia, Italy
SUMMARY - Durum wheat (Triticum durum Desf.) is a species well adapted to the Mediterranean
environments, where it often faces salt stress due to increasing soil salinity. Recently, the central role
of mitochondria in the adaptation to environmental stresses at sub cellular level has emerged. The
mitochondrial defence mechanisms may contribute to depict a durum wheat plant ideotype showing
higher water use efficiency under water and/or salt stress and able to be irrigated with brackish water.
In particular, two important mitochondrial mechanisms involved in resistance to environmental
stresses are: (i) the inhibition of proline oxidation (that parallels accumulation of proline as an
osmoprotectant in the cell); and (ii) the control exerted by Alternative Oxidise (AOX) of harmful
reactive oxygen species generated under stress. Durum wheat mitochondria (DWM) from early
seedlings were used to study these physiological mechanisms under salt stress. Seedlings were
germinated both in distilled water and in two different diluted sea water solutions, leading to either
moderate or severe damage to growth. To assess the contribution of the osmotic component of stress
(water stress), a parallel investigation was performed by using hyperosmotic mannitol solutions.
Comparison of proline and succinate oxidation by DWM showed that early inhibition of proline
oxidation should be considered a mitochondrial adaptation to stress rather than a damage to oxidative
properties, while, under our experimental conditions, no increase in AOX activity under stress was
observed. In conclusion, early inhibition of proline oxidation may be a useful character enhancing
tolerance to salt and water stress in durum wheat.
Key words: Saline stress, water stress, durum wheat, mitochondria, proline, alternative oxidise.
RESUME - Le blé dur (Triticum durum Desf.) est une espèce bien adaptée au milieu méditerranéen
où il est souvent exposé au stress salin à cause d’une teneur en sel croissante dans le sol. Ces
dernières années, le rôle central des mitochondries dans l’adaptation au stress environnemental au
niveau subcellulaire s’est manifesté d’une manière de plus en plus évidente. Les mécanismes de
défense des mitochondries pourraient contribuer à définir un idéotype de blé dur ayant une plus haute
efficience d’utilisation de l’eau en conditions de stress hydrique et/ou saline et pouvant être irrigué à
l’eau saumâtre. En particulier, deux principaux mécanismes contribuent à la résistance au stress
environnemental: (i) l’inhibition d’oxydation de la proline (qui accompagne l’accumulation de la proline
en tant qu’osmoprotecteur chez la cellule); et (ii) le contrôle, exercé par l’Oxydase Alternative (AOX),
des espèces réactives délétères dérivées de l’oxygène qui sont engendrées en conditions de stress.
Nous avons utilisé les mitochondries du blé dur (DWM) des jeunes plantes pour étudier ces
mécanismes physiologiques en conditions de stress salin. La germination des jeunes plantes a eu
lieu tant dans l’eau distillée qu’en deux différentes solutions diluées d’eau de mer, ce qui a provoqué
un dégât de modéré à grave sur la croissance. Pour évaluer la contribution de la composante
osmotique du stress, nous avons mené une expérience parallèle en utilisant les solutions de mannitol
hyperosmotique. La comparaison de l’oxydation du succinate et de la proline par les DWM a montré
que l’inhibition de l’oxydation de la proline devrait être considérée une adaptation mitochondriale au
stress plutôt qu’un dégât aux propriétés oxydatives, tandis que dans nos conditions expérimentales
nous n'avons observé aucune augmentation de l’activité d’AOX. En conclusion, l’inhibition d’oxydation
de la proline pourrait être un caractère utile qui améliore la tolérance au stress hydrique et salin chez
le blé dur.
Mots clés: Stress salin, stress hydrique, blé dur, mitochondrie, proline, oxydase alternative.
99
INTRODUCTION
The increase in salt content due to intrusion of sea water into aquifers leads to an increase of
salinity of the agricultural soils, which reduces plant growth and crop productivity in many arid and
semi-arid regions of the word (McKersie and Leshem, 1994). Uptake and compartmentation of ions,
as well as the production of compatible solutes, i.e. osmotic adjustment, occurring under salt stress
are linked to ATP consumption. In the light of this, the effect of salt stress on ATP production is
expected to be crucial (for refs. see Flagella et al., 2006). The two sub cellular organelles devoted to
massive ATP synthesis are chloroplasts and mitochondria, but the effect of salt and water stress has
been deeply investigated only in chloroplasts; more recently, the central role of mitochondria in stress
resistance has emerged (Pastore et al., 2007).
In order to carry out a specific investigation on the effect on mitochondrial function of salt and
water stress, we have chosen durum wheat early seedlings as a suitable experimental model system.
In fact, mitochondrial ATP production plays an essential role in germinating seedlings and is very
important for the establishment of the initial plant stand. Moreover, durum wheat is a species well
adapted to the Mediterranean environments, where salt stress due to seawater intrusion into aquifers
is an increasing problem (Rana and Katerji, 2000). This crop may experience salt stress when
cultivated in rotation to a crop irrigated with salt water. In this case, the highest salinity level is faced
during germination and seedling establishment rather than in the later developmental stages, where
spring and winter rainfall prevents salt stress occurrence by leaching excess salt (Caliandro et al.,
1991); therefore, salt stress occurs during the early phase of seedling growth, when mitochondrial
ATP synthesis plays a key role.
Recently, we have shown that durum wheat mitochondria (DWM) from young seedlings are an
early target of salt stress; in particular, the inhibition of proline oxidation was found to precede
damages to mitochondrial intactness and functionality (Flagella et al., 2006). This inhibition is
consistent with proline accumulation in the cell as an osmoprotectant. Anyway, whether inhibition of
proline oxidation in DWM may be considered a very early damage or an adaptative response is still
uncertain. A second research line we developed in the recent years deals with DWM ability to
counteract oxidative damage caused by environmental stresses. DWM possess three active energy
dissipating systems, namely the plant mitochondrial potassium channel, PmitoKATP (Pastore et al.,
1999a), the plant uncoupling protein, PUCP (Pastore et al., 2000) and the Alternative Oxidase, AOX
(Pastore et al., 2001); all the three proteins are able to prevent high mitochondrial membrane potential
(∆Ψ) generation and, as a consequence, they are able to dampen the production of harmful reactive
oxygen species (ROS) by DWM. We have recently demonstrated that PmitoKATP and PUCP may
control excess ROS production when young etiolated seedlings suffer salt and water stress (Trono et
al., 2004), while, to date, no information about AOX activity under these conditions is available.
In the present paper we have reinvestigated the inhibition of proline oxidation by comparing proline
and succinate oxidation by DWM obtained from seedlings subjected to salt stress (applied using
diluted sea water solutions) and water stress (applied using hyperosmotic mannitol solutions).
Interestingly, to gain novel information, we studied both washed mitochondria (i.e. a crude
mitochondrial fraction obtained via differential centrifugation) and purified mitochondria (i.e. the
mitochondrial fraction obtained after passage of washed organelles throughout a Percoll gradient). In
fact, in our opinion, the use of both washed and purified mitochondria may be advisable to obtain a
more integrated interpretation of the inhibition of proline oxidation under stress. Furthermore, we
checked AOX activity in DWM from sea water-stressed and water-stressed young seedlings.
We suggest that the comprehension of the mechanisms acting at mitochondrial level to counteract
salt and water stress may strongly contribute to depict an advanced durum wheat plant ideotype. The
addition of novel proper metabolic and biochemical traits to classical useful morpho-physiological
traits may make the new plant able to better grow and yield in semiarid areas also under moderate
salt stress.
MATERIALS AND METHODS
All reagents were purchased from SIGMA Chemical Co. (St. Louis, MO). Synthetic seawater was
obtained by dissolving a commercial sea salt (SPERA & Co, Margherita di Savoia, Italy) in distilled
100
water to obtain a solution containing 504 mM Na+, 10 mM K+, 54 mM Mg2+, 31 mM SO42-, 540 mM Clas evaluated by DIONEX DX 600 analysis (Flagella et al., 2006). Durum wheat (Triticum durum Desf.
cv Ofanto) seeds used in this work were supplied by the Experimental Institute for Cereal Research of
Foggia.
Stress was induced by using different sea water dilutions (salt stress) or hyperosmotic mannitol
solutions (water stress): (i) solutions having osmotic potential equal to -0.62 MPa (22% sea water,
.
-1
electrical conductivity (E.C.) equal to 12 dS m , or 0.25 M mannitol), which induce moderate stress;
.
-1
(ii) solutions having osmotic potential equal to -1.04 MPa (37% sea water, E.C. equal to 20 dS m , or
0.42 M mannitol), which induce severe stress (Francois and Maas, 1994; Trono et al., 2004; Flagella
et al., 2006). Iso-osmotic concentration of salt and mannitol solutions were checked by a vapour
pressure osmometer Roebling, type 13.
Durum wheat seeds (300 g) were sown on a distilled water-saturated polyurethane foam sheet
covered with a Whatman filter paper. Seeds were dark-grown for 48 h in a Heraeus HPS 1500
incubator at 25 °C and 85% relative humidity; then early seedlings (length of shoot about 0.3 cm)
were used to obtain mitochondria. Stressed seedlings were germinated as described for control
seedlings except that water was substituted with the sea water dilutions or mannitol solutions as
above described. Stressed seedlings were harvested when they reached the same shoot length of the
control (0.3 cm), after three and four days for the moderate and severe stress intensity, respectively.
Etiolated early seedlings (about 50-60 g) were removed from seeds, then mitochondria were
isolated according to Pastore et al. (1999b) with minor modifications. The grinding buffer was 0.3 M
mannitol, 4 mM cysteine, 1 mM ethylenediaminetetraacetic acid (EDTA), 30 mM 3-(N-morpholino)
propanesulfonic acid (MOPS) (pH 7.50), 0.1% (w/v) defatted bovine serum albumin (BSA), 0.6% (w/v)
polyvinylpyrrolidone (PVP)-360; the washing buffer was 0.3 M mannitol, 1 mM EDTA, 10 mM MOPS
(pH 7.40), 0.1% (w/v) defatted BSA. The fraction of washed mitochondria was further purified by
isopycnic centrifugation in a self-generating density gradient, consisting of 0.3 M sucrose, 10 mM TrisHCl (pH 7.20) and 28% (v/v) Percoll (colloidal PVP-coated silica, Amersham Pharmacia Biotech),
combined with a linear gradient of 0% (top) to 10% (bottom) PVP-40. Mitochondrial protein content
was determined by the method of Lowry, using BSA as a standard.
Oxygen uptake rate was measured at 25 °C with a GILSON Oxygraph model 5/6-servo Channel
pH 5, equipped with a Clark-type electrode (5331 YSI, Yellow Spring, OH) in 1.5 mL of a medium
consisting of 0.3 M mannitol, 5 mM MgCl2, 10 mM KCl, 0.1% (w/v) defatted BSA, and 10 mM sodium
phosphate buffer (pH 7.20). As respiratory substrates, either 10 mM succinate or 20 mM proline were
used. In the course of substrate oxidation, successive additions of limited amount of ADP were
carried out in order to evaluate: (i) the respiratory control (RC) ratio, i.e. the ability of ADP to control
the oxygen uptake rate expressed as a ratio between the rate measured in the presence of ADP
(state 3) and the rate measured after ADP consumption (state 4); and (ii) the ADP/O ratio, i.e. the
ratio between the nmol of phosphorylated ADP and the natom of oxygen consumed (see Flagella et
al., 2006).
AOX activity in succinate oxidising DWM was evaluated at 25 °C by using the above described
oxygen uptake medium, as a ratio between cyanide insensitive (V+KCN) and cyanide sensitive (V-KCN)
oxygen uptake rate, as reported in Fig. 2.
The intactness of mitochondrial membranes was evaluated oxygraphically (outer membrane), on
the basis of cytochrome c oxidase latency, and photometrically (inner membrane), on the basis of
malate dehydrogenase latency (see Trono et al., 2004).
∆Ψ was monitored at 25 °C by measuring safranin O fluorescence changes at λex=520 nm and
λem=570 nm, as reported in Flagella et al. (2006). The reaction mixture (2 mL) contained 0.3 M
mannitol, 5 mM MgCl2, 0.1% (w/v) defatted BSA, 10 mM MOPS (pH 7.20), 2.5 µM safranin O and 0.1
-1
mg ⋅ mL DWM protein ([safranin O]/[DWM protein] ratio value of 25).
101
RESULTS AND DISCUSSION
In order to gain some insight into plant bioenergetics under salt and water stress, experiments
were carried out by using the moderate salt sensitive species durum wheat (Triticum durum Desf.).
Seedlings were germinated in two different diluted sea water solutions, 22% and 37% sea water,
leading to moderate and severe damage to seedling growth, respectively (Trono et al., 2004; Flagella
et al., 2006). In order to assess the contribution of the osmotic component of the stress resulting in a
water stress, a parallel investigation was performed on seedlings germinated in 0.25 and 0.42 M
mannitol solutions, iso-osmotic with the two seawater solutions.
As for the DWM isolation protocol, a paper concerning hyperosmotic stress-adapted potato cells
shows that the isolation protocol giving better mitochondria needs the use of media showing an
osmolarity close to the one of the cells, as evaluated by plasmolysis experiments (Fratianni et al., 2001).
Unfortunately, the determination of tissue cell osmolarity from seedlings under our conditions is not a
simple matter. Therefore, we isolated mitochondria from stressed seedlings by using the same media
suitable for the control ones. In the light of this, due to the non-isotonic isolation media used, washed
DWM from stressed seedlings may result in part artificially damaged by the isolation procedure; this
could lead to an overestimation of the mitochondrial damages due to stress. On the other hand, the
purification of these organelles leads to a selective recovery of a population of highly intact and fully
functional mitochondria; therefore, purified mitochondria represent better organelles and may give
underestimation of the stress-induced damages. To overcome these problems, here, we isolate both
washed and purified DWM and compare the effects of the stress in both DWM populations.
Intactness and functionality of DWM from stressed seedlings
DWM were isolated from control and stressed seedlings. Since intact and coupled mitochondria
are strictly required to carry out studies concerning mitochondrial metabolism, a series of experiments
was performed by using both washed and purified DWM in order to ascertain structural and functional
features, including the intactness of outer and inner membranes and ∆Ψ in the absence (state 1) and
presence (state 4) of 5 mM succinate as oxidisable substrate.
The results relative to purified DMW were already published (Trono et al., 2004), while data
relative to washed DMW are reported in Table 1.
Table 1. Intactness of membranes and ∆Ψ in washed DWM from control and stressed seedlings
Membrane intactness (%)
Control
Sea water stress
a
Water stress
Moderate
%
Severe
%
Moderate
%
Severe
%
Outer membrane
83±0.7b
68±3.3**
82
28±3.2***
34
79±1.3*
95 67±1.5***
81
Inner membrane
94±1.0
84±1.5***
89
77±1.0***
82
86±1.0**
91 83±1.5***
88
∆Ψ (mV)
Control
a
Sea water stress
Water stress
Moderate
%
Severe
%
Moderate
%
ns
Severe
%
State 4 ∆Ψ
205±3.6
194±5.2
95
187±5.2*
91
200±5.0ns
97 192±6.4ns
State 1 ∆Ψ
202±3.4
140±3.8***
69
100±3.0***
49
170±8.0*
84 136±5.0*** 67
94
% of the control
mean value ± SE (n=4)
ns = not significant
* P<0.05, ** P<0.01, *** P<0.001, P represents the probability level according to the Student’s t test relative to the comparison
between each value with the corresponding control.
b
102
A slight reduction of the membrane intactness was observed, which was more evident in sea water
stress than under water stress and under severe more than under moderate stress; on the other hand, a
remarkable stripping of outer membrane under severe sea water stress was observed. No important
variations were observed in the ∆Ψ values in mitochondria oxidising succinate in state 4 comparing
stressed and control conditions, thus confirming substantial intactness of inner membrane. Interestingly,
in this set of experiments, DWM show high state 1 ∆Ψ due to endogenous substrates (Flagella et al.,
2006); moreover, DWM from stressed seedlings showed lower ∆Ψ values in state 1 than control, thus
suggesting progressive membrane permeability causing outflow of endogenous substrates in the course
of isolation procedure as a result of increasing level of stress (Trono et al., 2004; Flagella et al., 2006).
In the whole, in washed DWM, membrane intactness and ∆Ψ decreased with increasing strength stress
and seawater caused more detrimental effects than parallel water stress. Comparison between the data
from Trono et al. (2004) and the ones from Table 1 shows similar trends in purified and washed DWM;
moreover, as expected, washed mitochondria have a lower degree of intactness than the purified ones.
In any case, washed DWM from both control and stressed seedlings were obtained with a degree of
functionality sufficient to explore their oxidative properties.
Proline and succinate oxidation by DWM from stressed seedlings
Since accumulation of free proline is known to play an important role in the cell osmotic
adjustment, the effect of seawater stress and parallel water stress on proline oxidation by DWM was
evaluated. In particular, by using both proline and succinate as respiratory substrates, comparison
was made with respect to: (i) state 3 oxygen uptake rate (i.e. oxidation rate); (ii) coupling between
oxidation and ATP synthesis (RC ratio); and (iii) phosphorylative efficiency (ADP/O ratio). Data
relative to washed DWM are summarised in Table 2. Data relative to purified DWM were recently
published (see Trono et al., 2004), but they are again reported between brackets in Table 2 to
facilitate comparison between washed and purified DWM.
Table 2. Proline- and succinate-dependent oxygen uptake rate in state 3, RC and ADP/O ratios in
washed DWM under stress. The experimental conditions were as in “Materials and
Methods”. Values concerning purified DWM from Trono et al. (2004) are reported between
brackets. For the explanation of data reported in bold
Proline-dependent O2 uptake
Control
Seawater stress
Moderate
%
a
vb
47±2.7
(180±10.6)
34±2.0**
(91±2.4***)
72
(50)
RC
1.6±0.08
(2.1±0.11)
1.2±0.01**
ns
(2.0±0.02 )
75
(95)
ADP/O
2.2±0.03
(2.5±0.04)
1.8±0.07**
(1.9±0.08***)
82
(76)
Water stress
Severe
%
Severe
%
39±1.05
(108±6.3**)
83
(60)
26±1.9***
(51±3.8***)
55
(28)
1.3±0.02*
1.0±0.03*** ndd
d
ns
(1.0±0.03***) (nd ) (2.1±0.03 )
81
(100)
1.0±0.01***
(1.0±0.01***)
–
(–)
86
(100)
nd
(nd)
–
(–)
19±1.1***
(31±1.8***)
d
nd
d
(nd )
%
40
(17)
–
(–)
Moderate
*
1.9±0.03***
(2.5±0.11ns)
Succinate-dependent O2 uptake
Control
Sea water stress
Water stress
Moderate
%
Severe
%
79
(88)
105±7.8***
(316±16.0**)
54
(62)
c
v
195±11.5
(510±30.0)
155±9.2*
(450±15.0ns)
RC
1.9±0.09
(2.3±0.10)
1.4±0.04**
ns
(2.3±0.04 )
ADP/O
1.8±0.03
(1.8±0.03)
1.6±0.04**
ns
(1.7±0.08 )
Moderate
%
ns
180±10.5
92
(540±31.6ns) (106)
Severe
%
128±7.5**
(370±21.6**)
66
(72)
d
1.6±0.05*
1.0±0.01***
74
nd
d
(100) (1.0±0.01***) (nd ) (2.3±0.04ns)
84
(100)
1.3±0.08**
(2.0±0.06*)
68
(87)
1.8±0.07ns
(1.8±0.07ns)
100
(100)
1.5±0.04***
ns
(1.8±0.05 )
83
(100)
89
(94)
d
nd
d
(nd )
–
(–)
a
% of the control
-1
-1
state 3 oxygen uptake rate expressed as natom O2 ⋅ min ⋅ mg of protein
c
mean value ± SE (n=4)
d
not determinable in mitochondria having RC ratio equal to 1, i.e. uncoupled (Trono et al., 2004; Flagella et al., 2006)
ns = not significant
*P<0.05, ** P<0.01, *** P<0.001, P represents the probability level according to the Student’s t test relative to the comparison
between each value with the corresponding control.
b
103
The results of Table 2 show that both sea water stress and water stress lead to an inhibition of
proline and succinate oxidation and a decrease of both coupling and phosphorylative efficiency.
Consistently, we have recently reported a decrease of the rate of ATP synthesis under these
conditions (Flagella et al., 2006). These results are in accordance with several literature reports
(Stewart et al., 1977; Sells and Koeppe, 1981; Schmitt and Dizengremel, 1989). These effects were
found to increase with increasing stress intensity; moreover, they were found to be more evident
under sea water stress than under water stress, so confirming that under our experimental conditions
the overall sea water damage is dependent on both a toxic and an osmotic component (Greenway
and Munns, 1980). Interestingly, as previously found in water-stressed maize seedlings (Sells and
Koeppe 1981) and other model systems (Boggess et al., 1978; Schmitt and Dizengremel, 1989), we
show that the decline in proline oxidation rate under stress conditions was even more dramatic than
for succinate. This sharp reduction leads to the hypothesis that the imposed stress conditions affect in
a specific manner mitochondrial mechanisms responsible for proline oxidation.
At this regard, by comparing washed and purified DWM with respect to the percentage values of
Table 2 of both proline and succinate oxygen uptake rate under all stress conditions, an interesting
finding is obtained: the inhibition of proline oxidation is more evident in purified than in washed DWM,
while the inhibition of succinate oxidation is more marked in DWM washed fraction. In order to
emphasise this finding, the percentage data reported in bold in the % columns of Table 2 are
processed as shown in Fig. 1.
Fig. 1. Opposite behaviour of proline and succinate oxidation by washed and purified DWM from
stressed seedlings. The % data are the ones reported in bold in Table 2.
The opposite effect of stresses on proline and succinate oxidation is well evident. This effect may
be observed irrespective to the kind and intensity of the stress imposed.
So, a more evident inhibition of succinate oxidation was observed in the washed fraction, which
contains the more damaged organelles, than in the purified one, while the inhibition of proline
oxidation is much higher in purified DWM, i.e. the highly intact and fully functional organelles. In the
light of this, it is reasonable to suppose that the alterations found in succinate oxidation represent
damages due to the stress imposed. On the contrary, the decrease in the proline oxidation rate
should be considered an active mitochondrial adaptation to stress rather than a generic early damage
104
of the oxidative properties. Consistently, we have recently showed that inhibition of proline oxidation
parallels proline accumulation in durum wheat seedlings (Flagella et al., 2006). Anyway, data reported
in literature (Boggess et al., 1976; Voetberg and Sharp, 1991) show that the increase in the proline
synthesis from glutamate rather than inhibition of oxidation represents the main factor resulting in
proline accumulation in stressed plant tissues; this point will merit further investigation in durum
wheat.
AOX activity in DWM from stressed seedlings
The AOX branches from the respiratory chain at the level of ubiquinone and it is known to be
cyanide and antimycin insensitive. Since AOX bypasses the last two sites of energy conservation
associated with the cytochrome pathway, it shows a non phophorylating and, as a consequence, an
energy dissipating character (Vanlerberghe and McIntosh, 1997). This appears to be useful to control
both ∆Ψ and mitochondrial ROS generation, which occurs at high rate when ∆Ψ is high. As a
consequence, AOX is expected to act as an antioxidant system under environmental stresses
inducing oxidative stress at cellular level (Maxwell et al., 1999; Pastore et al., 2001 and refs. therein).
Therefore, experiments were performed to evaluate its activity under our conditions of stress
imposition, that were shown to enhance mitochondrial superoxide anion generation (Trono et al.,
2004). In this case, only the purified DWM were studied.
AOX activity in succinate oxidising DWM was evaluated by means of oxygen uptake
measurements in the presence of dithiothreitol (DTT) and pyruvate, specific AOX activators (Fig. 2a)
(Millar et al., 1993; Vanlerberghe and McIntosh, 1997).
Fig. 2. AOX activity expressed as a fraction of cytochrome pathway in DWM purified from control and
stressed seedlings.
(a) Measurements of oxygen uptake by DWM purified from moderately sea water-stressed
seedlings were carried out in 1.5 mL of the medium reported in “Materials and Methods”; ATP
(200 µM) was also present in order to activate succinate dehydrogenase. The compounds
were added at the time indicated by the arrows. DTT and pyruvate are AOX activators. The
-1
-1
numbers on the traces refer to the natom of oxygen taken up ⋅ min ⋅ mg of protein. The AOX
activity was expressed as V+KCN/V-KCN, where V-KCN and V+KCN represent the rate before
cyanide addition and the residual rate in the presence of cyanide plus AOX activators,
respectively.
(b) AOX activity under control and stress conditions. Data are expressed both as mean value ±
SE (n=4) and as % of the control. ns = not significant; * P<0.05, P represents the probability
level according to the Student’s t test relative to the comparison between each value and the
control.
105
Oxygen uptake was started by adding 10 mM succinate to DWM suspended in the reaction
medium; the measured oxygen uptake rate was indicated as V-KCN. Then, 1 mM KCN was added
which completely blocked oxygen uptake, since DWM do not spontaneously show alternative
respiratory pathway (Pastore et al., 2001). The addition of 1 mM DTT and 1 mM pyruvate stimulated a
cyanide-insensitive oxygen uptake rate, indicated as V+KCN, which was completely stopped by 1 mM
salicylhydroxamic acid (SHAM), a powerful AOX inhibitor. The V+KCN/V-KCN ratio was used as an
indicator of the AOX activity, expressed as a fraction of cytochrome pathway. This assay gives useful
information about maximal activity of the AOX measured in vitro, which is a parameter related to the
AOX amount in DWM, but is unable to test AOX contribution to overall respiration in vivo. To do this,
further studies are required based on isotope fractionation technique (Ribas-Carbo et al., 2005a).
Based on measurements shown in Fig. 2a, AOX dependent oxygen uptake in control conditions
was about 35% with respect to the one dependent on cytochrome pathway. The comparison between
control and stress conditions shows that the contribution of AOX functioning with respect to the
cytochrome pathway was unchanged under moderate stresses and even little inhibited under severe
stresses (Fig. 2b). Although this result is in apparent contrast with the widely accepted role of this
enzyme as a protective system under stress conditions, it is not surprising. In fact, also Kasai et al.
(1998) reported that, though the alternative pathway plays a critical role in germinating wheat
seedlings, NaCl salinity do not affect it. Moreover, Jolivet et al. (1990) found that in barley the activity
of the alternative pathway under NaCl stress was not modified in isolated mitochondria, while it was
increased in whole leaf tissue. Finally, Lutts et al. (2004) found an increase in the relative importance
of AOX in durum wheat callus submitted to NaCl stress, but this was lower in salt resistant cultivars
than in salt sensitive ones; so, it seems that the stimulation of the alternative pathway may be not
necessarily related to stress resistance. As far as durum wheat is concerned, our previous findings
strongly suggest that AOX may act as an antioxidant defence system not in etiolated tissues, but in
green tissues, that may contain hydroxypyruvate and glyoxylate, two powerful DWM-AOX activators
(Pastore et al., 2001). Consistently, Ribas-Carbo et al. (2005b) recently reported that in soybean
leaves severe water stress caused a significant shift of electrons from the cytochrome to the
alternative pathway due to a biochemical regulation other than protein synthesis. As for etiolated
tissues, DWM display high activity of two different dissipating systems able to dampen mitochondrial
ROS production, namely the PUCP (Pastore et al., 2000) and the PmitoKATP (Pastore et al., 1999a).
Moreover, we have recently shown that PUCP and PmitoKATP are strongly activated in DWM under
salt and water stress in order to act against oxidative stress (Trono et al., 2004), thus replacing AOX
function. Our idea of a tissue specific cross-regulation between PUCP, PmitoKATP and AOX is
consistent with the finding of Sluse et al. (1998) who reported opposite regulation by free fatty acids of
PUCP and AOX, and with our observation that both PmitoKATP and PUCP are directly and very rapidly
activated by ROS (Pastore et al., 1999a; Pastore et al., 2000), while this does not occur in the case of
AOX (Pastore et al., 2001). For a very recent review about this topic see Pastore et al. (2007).
CONCLUSIONS
Durum wheat resistance to salt and water stress may be a function not only of proper morphophysiological adaptations, but also of biochemical characteristics including mitochondria metabolism.
Here, we suggest that early inhibition of proline oxidation under stress may be a useful character to
improve salt and water stress tolerance; instead, the role of AOX against these stresses is
questionable in durum wheat. New genotypes well fitted for Mediterranean environments showing
higher water use efficiency may be hypothesised by improving mitochondria properties both via
conventional and non conventional breeding.
106
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Physiol., 62: 22-25.
Boggess, S.F., Stewart, C.R., Aspinall, D. and Paleg, L.G. (1976). Effect of water stress on proline
synthesis from radioactive precursors. Plant Physiol., 58: 398-401.
Caliandro, A., Cucci, G., De Caro, A. and Cordella, S. (1991). Irrigation with brackish water: influence
of the irrigation regime on salt built-up in the soil and leaching effect of rainfall. European
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July 1991.
Flagella, Z., Trono, D., Pompa, M., Di Fonzo, N. and Pastore, D. (2006). Seawater stress applied at
germination affects mitochondrial function in durum wheat (Triticum durum) early seedlings. Funct.
Plant Biol., 33: 357-366.
Francois, L.E. and Maas, E.V. (1994). Crop response and management of salt-affected soils. In
Handbook of Plant and Crop Stress. Dekker, M. (ed). New York, USA, pp. 149-181.
Fratianni, A., Pastore, D., Pallotta, M.L., Chiatante, D. and Passarella, S. (2001). Increase of
membrane permeability of mitochondria from isolated water stress adapted potato cells. Biosci.
Rep., 21: 81-91.
Greenway, H. and Munns, R. (1980). Mechanisms of salt tolerance in nonhalophytes. Ann. Rev. Plant
Physiol., 31: 149-190.
Jolivet, Y., Pireaux, J.-C. and Dizengremel, P. (1990). Changes in properties of barley leaf
mitochondria isolated from NaCl-treated plants. Plant Physiol., 94: 641-646.
Kasai, K., Mori, N. and Nakamura, C. (1998). Changes in the respiratory pathways during germination
and early seedling growth of common wheat under normal and NaCl-stressed conditions. Cereal
Res. Commun., 26: 217-224.
Lutts, S., Almansouri, M. and Kinet, J.-M. (2004). Salinity and water stress have contrasting effects on
the relationship between growth and cell viability during and after stress exposure in durum wheat
callus. Plant Sci., 167: 9-18.
Maxwell, D.P., Wang, Y. and McIntosh, L. (1999). The alternative oxidase lowers mitochondrial
reactive oxygen production in plant cells. Proc. Natl. Acad. Sci. USA, 96: 8271-8276.
McKersie, B.D. and Leshem, Y.Y. (1994). Stress and stress coping in cultivated plants. Kluwer
Academic Publisher, Dordrecht, The Netherlands.
Millar, A.H., Wiskich, J.T., Whelan, J. and Day, D.A. (1993). Organic acid activation of the alternative
oxidase of plant mitochondria. FEBS Lett., 329: 259-262.
Pastore, D., Fratianni, A., Di Pede, S. and Passarella, S. (2000). Effects of fatty acids, nucleotides
and reactive oxygen species on durum wheat mitochondria. FEBS Lett., 470: 88-92.
+
Pastore, D., Stoppelli, M.C., Di Fonzo, N. and Passarella, S. (1999a). The existence of the K channel
in plant mitochondria. J. Biol. Chem., 274: 26683-26690.
Pastore, D., Trono, D. and Passarella, S. (1999b). Substrate oxidation and ADP/ATP exchange in
coupled durum wheat (Triticum durum Desf.) mitochondria. Plant Biosystems, 133: 219-228.
Pastore, D., Trono, D., Laus, M.N., Di Fonzo, N. and Flagella, Z. (2007). Possible plant mitochondria
involvement in cell adaptation to drought stress. A case study: durum wheat mitochondria. J. Exp.
Bot., in press.
Pastore, D., Trono, D., Laus, M.N., Di Fonzo, N. and Passarella, S. (2001). Alternative oxidase in
durum wheat mitochondria. Activation by pyruvate, hydroxypyruvate and glyoxylate and
physiological role. Plant Cell Physiol., 42: 1373-1382.
Rana, G. and Katerji, N. (2000). Measurement and estimation of actual evapotranspiration in the field
under Mediterranean climate: a review. Eur. J. Agron., 13: 125-153.
Ribas-Carbo, M., Robinson, S.A. and Giles, L. (2005a). The application of the oxygen-isotope
technique to assess respiratory pathway partitioning. Chapter 3. In Plant Respiration: From Cell to
Ecosystem, Vol. 18, Advances in Photosynthesis and Respiration Series. Lambers, H. and RibasCarbo, M. (eds). Springer, Dordrecht, The Netherlands, pp. 31–42.
Ribas-Carbo, M., Taylor, N.L., Giles, L., Busquets, S., Finnegan, P.M., Day, D.A., Lambers, H.,
Medrano, H., Berry, J.A. and Flexas, J. (2005b). Effects of water stress on respiration in soybean
leaves. Plant Physiol., 139: 466-473.
Schmitt, N. and Dizengremel, P. (1989). Effect of osmotic stress on mitochondria isolated from
etiolated mung bean and sorghum seedlings. Plant Physiol. Biochem., 27: 17-26.
Sells, G.D. and Koeppe, D.E. (1981). Oxidation of proline by mitochondria isolated from waterstressed maize shoots. Plant Physiol., 68: 1058-1063.
107
Sluse, F.E., Almeida, A.M., Jarmuszkiewicz, W. and Vercesi, A.E. (1998). Free fatty acids regulate
the uncoupling protein and alternative oxidase activities in plant mitochondria. FEBS Lett., 433:
237-240.
Stewart, C.R., Boggess, S.F., Aspinall, D. and Paleg, L.G. (1977). Inhibition of proline oxidation by
water stress. Plant Physiol., 59: 930-932.
Trono, D., Flagella, Z., Laus, M.N., Di Fonzo, N. and Pastore, D. (2004). The uncoupling protein and
the potassium channel are activated by hyperosmotic stress in mitochondria from durum wheat
seedlings. Plant Cell Environ., 27: 437-448.
Vanlerberghe, G.C. and McIntosh, L. (1997). Alternative oxidase: from gene to function. Annu. Rev.
Plant Physiol. Plant Mol. Biol. 48: 703-734.
Voetberg, G.S. and Sharp, R.E. (1991). Growth of maize primary root at low water potentials. III. Role
of increased proline deposition in osmotic adjustment. Plant Physiol., 96: 1125-1130.
108
SUBMERGED REVERSE OSMOSIS PLANT (SROP)
D. N. Bapat – 15.10.2006
The Tata Power Company Ltd
34, Sant Tukaram Road, Carnac, Mumbai 400 009, INDIA
SUMMARY – The availability of Potable water on the land is depended on the natural cycle of
evaporation, condensation and precipitation of sea water. This is dependent on various factors and in
large areas there is scarcity of potable water. In this article a Submerged Reverse Osmosis Plant is
described which has been worked out that provides a cheap source of potable water from sea water.
Due to development of Reverse Osmosis membranes that can filter out salt molecules it is possible to
have potable water from sea water. However, this process requires high pressure sea water. In this
plant the high pressure sea water is derived from deep sea that makes the potable water cheap. An
innovative mechanism is used to develop the high pressure sea water. The scaled model is under
construction and working plant is planned in near future.
Key words: Potable water, Reverse Osmosis
INTRODUCTION
The potable water availability on the land is diminishing. Efforts are made to convert abundant sea
water into potable water for drinking & industrial use. To obtain potable water from Sea water Reverse
Osmosis (RO) is one of the processes that has been used and proven to be an economical and
environmental friendly process as it consumes lower energy per cubic meter of potable water
produced as compared to other process like distillation etc.
However, in RO of Sea Water (SW) major part of the energy is consumed in following activities:
• In bringing sea water to the RO Plant on the shore by pumping: Large quantity of SW has to be
pumped from depth of sea to long distance (4-10 km) to the RO Plant on the suitable coastal
site. As the RO efficiency decreases a lot with the increase in concentration of salt in the SW,
th
only about 1/10 volume of potable water can be produced from a volume of sea water. That is
to say about 1000 liters of SW has to be used to produce 100 liters of potable water. This
requires large quantity of SW to be pumped and transported to the RO plant.
• In maintaining high pressure of SW across the RO membrane: Pumps have to run continuously
to maintain high pressure of the order of 60 to 70 bar of SW across the RO membrane. This is
a large energy consuming process involved in RO plants.
• The capital cost and running cost of RO plants is due to the following:
i)
Large length of piping and pumping system required for pumping SW to RO plant at
shore.
ii)
High pressure pump sets to maintain high pressure SW as described above.
iii) Land cost of the area occupied by RO plant.
iv) Operation and maintenance cost of RO plant as high pressures are involved.
109
In the SROP the above referred costs are eliminated/ reduced so that the cost of potable water
produced is lesser than the cost of potable water produced by conventional RO plant as explained
below:
• The SROP is submerged in the sea below a level of about 60 meters. This allows availability
of SW in abundance to the SROP eliminating the cost of transporting sea water to RO plant.
• The high pressure SW required for RO process is developed with the help of an innovative
mechanism from the pressure of the sea at the depth of sea. This eliminates high pressure
pumping system required to maintain high pressure across RO membrane.
• Only a small pump is required to fetch potable water from SROP to the shore or to the point of
use. Since, the amount of potable water is much less than the sea water used to produce it,
the piping and pump requirements are reduced to only 10%.
• The land requirement on shore is totally eliminated, since SROP does not require any land for
installation being installed submerged in sea.
• The SROP is designed to operate in fully automatic mode that eliminates operation cost to
large extent.
• The components and mechanism of SROP have been designed to be with minimum
requirements for maintenance. Also, the material of construction of the plant has been
selected to give protection from corrosion of sea water with minimum cost.
CONCEPT AND WORKING
The high pressure SW required for RO process would be at a depth of 600 to 700 meters. To
locate a sea shores near which such depths of sea is available would be difficult and limited to only
few places. Also such depths (600 to 700 m) of sea would be far away from sea shore. However, if
the RO plant is located just 60 to 70 meters below sea level the quality of SW required for RO would
be suitable and such depth of sea would be available near most of the sea shores. But at this depth
the pressure of SW will not be enough for RO process. Therefore, to enhance SW pressure to the
required level of 60 to 70 bar an innovative mechanism consisting of levers, pistons and cylinders in
used.
Please refer to the schematic of SROP attached herewith. In the pressure developing cylinder a
piston is moving which is connected to Force multiplying lever. On one side of the piston, the side
facing the cylinder atmospheric pressure is acting since a pipe above the sea level vents this side of
the cylinder. On the other side of the piston the sea water pressure of depth of 60 meters is acting.
This creates a force equal to difference of these pressures multiplied by the area of the piston and
makes it to move inside the cylinder. This force is levered 10 times to act on the high pressure
exerting piston in the pressure chamber A. which in turn acts on the sea water in the chamber. Thus
the pressure developed in the chamber would be 10 times the pressure of SW at depth of 60 meters.
The high pressure SW in the chamber A passes through RO membrane till an impasse
th
concentration is reached i.e. about 1/10 volume of Chamber A.
The passed SW through RO membrane is free of salt and other suspended particles and is
potable for use, which collects in the potable water chamber. From here it is pumped above sea level
and taken to the point of use on the shore.
th
After the high pressure exerting piston has moved by 1/10 of its stroke the outlet solenoid valve is
opened that allows the balance concentrated SW to go out to the surface of sea during the remaining
stroke of high pressure exerting piston. The concentrated SW at sea level is collected for making salt.
When the high pressure exerting cylinder makes full stroke, the outlet solenoid valve is closed and
pump for SW is started. This pumps in fresh SW in high pressure chamber A till the piston reaches
110
fully outward and the pump is stopped closing solenoid inlet valve. At this position the above cycle
repeats.
The cycle is controlled by position switches and is fully automatic.
PROBLEMS AND SOLUTIONS
The problems envisaged in SROP are as under and their solutions are also arrived at as explained
below.
i)
Filtration/ pre treatment of feed Water: At a depth in sea to provide filtration/ pre treatment of feed
water appeared to be a problem. But using the similar arrangement as described for RO the sea
water can be filtered and the filtered water is fed to inlet of pump for SW which pumps in filtered
SW into the high pressure chamber A for RO.
ii) Enhancement of SW pressure to required level for RO: the innovative piston solves this problem,
cylinder and lever mechanism described earlier.
iii) To maintain low pressure on the filtered side of RO membrane: A vent to the atmosphere is
provided from the filtered side of RO membrane by this low pressure is maintained. Also this vent
acts as air inlet when the potable water is pumped out to the sea level.
iv) Pumping of potable water above sea level: With the suitable small submersible pump of capacity
1 cu.m/hr the potable water is pumped above sea level to be collected there for transporting to the
point of use.
v) Replenishment of SW in the pressurized RO chamber is achieved by a high pressure submersible
pump that has a capacity about 1 cu.m/Min and can stand the sea water environment around at
60-70 bar pressure. This pump would be working only one minutes in every 6 minutes.
vi) Maintenance of SROP under deep sea water: The platform on which SROP is mounted is placed
on the sea bed about 60 meters below sea level. For periodic maintenance once in 6 months or as
per need it can be pulled up above sea level from floating Barges and placed on them for
maintenance and component replacement. After maintenance it can be lowered and placed back
in position.
vii) Corrosion due to SW at higher pressure: Stainless steel of suitable quality is used for structural
and load carrying members and cylinders etc. The pistons are fabricated out of non corrosive
material with piston rings made out of Teflon that gives protection against corrosive atmosphere.
The material of pressure pump is also selected that avoids its corrosion.
SCHEMATIC OF SRPO
The schematic of SRPO is enclosed as Annexure. The working of the SRPO is explained above.
The brief bill of material for SRPO is as under:
•
•
•
•
•
•
•
•
•
•
Mounting platform
Prefilter vessel
Pressure developing cylinder
Link L1
Pressure developing piston
Force multiplying lever
Pump for Potable Water
Piping for inter connection and vents etc
Limit Switches
Solenoid Valve/ NRV
•
•
•
•
•
•
•
•
•
•
•
Outlet Solenoid Valve Contactors
Cables/ bushing
Sealant
Fulcrum/ Pivot
Link L2
High Pressure Chamber A
High pressure exerting piston
RO Membrane with mounting arrangement
Potable water chamber
Pump for Sea Water
Power supply
111
PROJECT IMPLEMENTATION
The detailed design of SROP has been made. The design has been checked with calculations for
technical feasibility. Component drawings and assembly drawings have been completed. A scaled
model is under preparation. After trials on the model the drawings will be modified for production of
SROP. Few sites along the Western Coast of India where depth of sea is adequate and the quality of
water is suitable have been identified. Permissions from authorities to conduct the trials of SROP
have been initiated. Efforts are made to find the funding agency for the project and further
communication is in progress with them.
COST ESTIMATES
The cost for making model and its trials are estimated at Rs.0.5 million (US $ 11 thousand). The
estimated capital cost of SROP of 1 Cu.M /hr capacity is Rs.2.00 million (US $ 44 thousand) at
present level of prices. The cost of 1 Cu.M of potable water produced by the plant works out to be
Rs.27 (US $ 0.6) The cost estimates are being revised on receiving the quotations for components
and material which are being obtained at present.
PLAN
To complete the model its trials, manufacturing SROP and its commissioning, it is estimated to
take two years. Low cost funding is sought from World Bank and other eco friendly institutes, which
will speed up the activities and make it economical. There are some innovative processes in SROP
for which actions for IPR have been initiated. The plan for commercialization of SROP has been
made. The commercial version of SRPO will be a boon for settlements, installation, projects on sea
shore and in the sea where potable water is needed by the mankind.
112
113
TREATED WASTEWATER SOURCES: ACTIONS TOWARDS SUSTAINABLE
AND SAFELY USE IN THE NEAR EAST AND ACHIEVING FOOD SECURITY
IN WATER-SCARCE POOR RURAL COMMUNITIES
R. Choukr-Allah
Head of the salinity and plant nutrition laboratory I.A.V Hassan II Agadir, Morocco BP 773
E-mail: [email protected] or [email protected]
SUMMARY- Near East and North Africa countries (NENA) are characterized by severe water
imbalance uneven rainfall, and at the same time, are unable to meet their food requirements using the
available water resources. Treated and re-used sewage water is becoming a common source for
additional water. Some of these countries have included wastewater re-use in their water planning.
This will narrow the gap between freshwater supply and demand in different water-use sector.
Wastewater recycling and reuse have become increasingly important for two reasons in the NENA
region. Firstly, properly treated municipal wastewater often is a significant water resource rich in
nutrients for crop production. Secondly, discharge of sewage effluent into surface effluent into surface
water is becoming increasingly difficult and expensive as treatment requirements become more
stringent to protect receiving waters such as rivers, estuaries, and beaches.
In small communities, the quality of the effluent from wastewater treatment plants (WWTP) is limited
by the low feasibility of investment in construction of small-scale WWT facilities and in their operation.
Using the treated effluent for irrigation purposes adds an economical driving force for investments in
WWT. Another economic advantage of choosing agricultural irrigation, as a final disposal solution for
the treated effluent is that it permits low quality demands, especially in regard to nutrients removal.
Final disposal by irrigation is usually combined with non-compromising hygienic demands. Controlled
utilization of the treated effluent reduces the environmental risks of polluting lakes, rivers and/or other
land and water resources, which might be caused by other alternatives of effluent disposal.
Governments in NENA should assess the reuse of treated wastewater with an integrated approach
taking into account not only the monetary cost and benefits in terms of ecological, social and
economic concerns, but more to consider a systemic perspective of the sustainability impacts.
Moreover such a systemic perspective should be developed in a participatory process with a specific
focus on the local or regional conditions. Furthermore the acceptance for the reuse and the costs of
treating the wastewater and transporting it to the reuse location should be taken into account and
handled appropriately.
This paper will address the integrated approach for reclamation and reuse of treated wastewater? The
criteria and standard that should be applied for wastewater reuse in agriculture? What are the
appropriate treatment technologies to be used for poor rural areas? What are the viable options for
reuse of waste water, what are the most salient constraints (both technically, institutionally and
financially), and how can we move forward with the use of treated waste water for agriculture within
the parameters of rural development in the NENA region, including sustainability issues?
INTRODUCTION
Near East and North Africa countries (NENA) are characterized by severe water imbalance
uneven rainfall, and at the same time, increased demands for irrigation and domestic water supply
have been occurred in recent last two decades as a result of expending urban population and tourist
industry. . This region is the driest on earth, containing only 1% of the world’s freshwater resources
and will become water-stressed because of increased water scarcity (Seckler et al., 1998; FAO, 2003)
(Table 1). Although water is recycled in the global hydrologic cycle for millenniums; much smallerscale planned local water recycling and reuse have become increasingly important for two reasons in
the NENA regions.
115
Evaluating the challenges and opportunities for using marginal-quality waters will help in guiding
investment and management decisions pertaining to land and water management in agriculture.
Considering the growing water shortage in the Near East and North Africa countries and history of
water use, it is expected that the use of marginal-quality waters for various purposes will be more
common in the foreseeable future. Key decisions are needed in the short and long terms in relation to
the use of such water resources to support achievements of the United Nations’ Millennium
Development Goals to enhance food security and environmental quality during the next 50 years. In
addition, there is a need to address the current situations where marginal- quality waters are already
used for food production especially in resource-poor environments, where regulations need to be
realistic and feasible
Agriculture reuse of treated wastewater should be integrated into comprehensive land and water
management strategy taking into count water supply, type of treatment technology, final reuse, social
and economic context. The reuse of treated waste water enhance agriculture productivity in several
NENA countries, however it will require public health protection, appropriate treatment technology,
public acceptance and participation. This paper assesses the current situation regarding the use and
significance of wastewaters in agriculture and also provides insight into the technological, institutional,
and policy options that might help in increasing its advantages and opportunities while reducing
possible negative impacts on people and the environment.
Table 1. Estimates of populations and natural renewable water resources (NRWR) per capita in
selected NENA countries during the year 2002 and projections for the year 2025.
Country
Kuwait
United Arab Emirates
Qatar
Libya
Saudi Arabia
Jordan
Bahrain
Yemen
Israel
Oman
Algeria
Tunisia
Egypt
Morocco
Lebanon
Syria
3
Population (× 10 )
NRWR (m3 capita–1 yr–1)b
2002
2025c
2002
2025d
2023
2701
584
5529
21701
5196
663
19912
6303
2709
31403
9670
70278
30988
3614
17040
3219
3468
754
7972
40473
8666
887
48206
8486
5411
42738
12343
94777
42002
4581
27410
10
56
91
109
111
169
175
206
265
364
460
577
830
936
1220
1541
6
43
70
75
59
102
131
85
197
182
338
452
615
691
962
958
Source: Qadir and al 2006. (based on databases of the AQUASTAT Information System of Food and
Agriculture Organization of the United Nations, the World Bank, and the World Resources Institute;
a
modified from World Resources Institute, 2003)
a
Selected countries from West Asia and North Africa and Sub Saharan Africa.
NRWR include Internal Renewable Water Resources plus or minus the flows of surface and groundwater
entering or leaving the country, respectively.
c
UN medium variant population projections for the year 2025.
d
Based on the assumption that the NRWR in the countries in 2025 will remain the same as in 2002.
b
POTENTIAL OF TREATED WASTEWATERS
The volume of wastewater increases with increasing population, urbanization, and improved living
conditions (Raschid-Sally et al., 2005). Considering 20% as the depleted fraction from urban water
use and anticipating growth in urban water supply coverage as a proxy for amounts of wastewater
generated, it is revealed that in spite of reliance on onsite sanitation, wastewater from Near East and
116
North Africa cities will pollute large volumes of water for the downstream agriculture (Scott et al,
2004). In most developing countries, urban drainage and disposal systems are such that wastewater
generated by different activities gets mixed and the resulting effluent may be disposed of in a
wastewater treatment plant, in another water body, or diverted to farmers’ fields in treated, partly
treated, diluted and/or untreated form (Qadir et al.2006).
Table 2. Volume of wastewater generated annually in some NENA countries
___________________________________________________________________________
6
3
–1
Country
Reporting year
Wastewater volume (× 10 m yr )
___________________________________________________________________________
Algeria
2004
600
Bahrain
1990
45
Egypt
1998
10012
Jordan
2004
76
Kuwait
1994
119
Lebanon
1990
165
Libya
1999
546
Morocco
2002
650
Oman
2000
78
Saudi Arabia
2000
730
Syria
2002
825
Tunisia
2001
240
Turkey
1995
2400
United Arab Emirates
2000
881
Yemen
2000
74
___________________________________________________________________________
Source: (Aquastat, FAO, 1997, Qadir and al. 2006)
WASTEWATER AS ADDITIONAL WATER RESOURCE
There are several benefits of treated wastewater reuse. First, it preserves the high quality,
expensive fresh water for the highest value purposes–primarily for drinking. The cost of secondarylevel treatment for domestic wastewater in NENA, an average of $US 0.2 to 0.5/m3, is the cheaper,
in most cases much cheaper, than developing new supplies in the region (WB, 2000). Second,
collecting and treating wastewater protects existing sources of valuable fresh water, the environment
in general, and public health. In fact, wastewater treatment and reuse (WWTR), not only protects
valuable fresh water resources, but it can supplement them, through aquifer recharge. If the true,
enormous, benefits of environmental and public health protection were correctly factored into
economic analyses, wastewater collection, treatment and reuse would be one of the highest priorities
for scarce public and development funds. Third, if managed properly, treated wastewater can
sometimes be a superior source for agriculture, than some fresh water sources. It is a constant water
source, and nitrogen and phosphorus in the wastewater may result in higher yields than freshwater
irrigation, without additional fertilizer application (Papadopoulos, 2000). Research projects in Tunisia
have demonstrated that treated effluent had superior non-microbiological chemical characteristics
than groundwater, for irrigation. Mainly, the treated wastewater has lower salinity levels (WB, 2000,
pg.8).
Estimates of the extent to which wastewater is used for agriculture worldwide reveal that at least
6
2 × 10 ha are irrigated with treated, diluted, partly treated or untreated wastewater (Jimenez and
Asano, 2004). The use of untreated wastewater is intense in areas where there is no or little access to
other sources of irrigation water and is being practiced in several North African countries.
117
Table 3. Annual domestic and industrial water use and potential treated wastewater for reuse in some
NENA countries.
Total Potential
Irrigation
Savings
M m3/year
Domestic
Savings
Potential
industrial/Commerci
al Savings Potential
M m3/year
M m3/year
Treated
Wastewater
Potential for
use
M m3/year
Water Savings
l Potential
M m3/year
Syria
1,360.0
174.1
3.5
135.9
1,673.5
Lebanon
95.0
99.7
1.9
286.3
482.9
Jordan
73.8
71.0
0.4
89.7
234.9
Egypt
4,773.0
1,079.4
55.5
5,108.1
11,016.0
Libya
400.2
161.9
1.2
248.0
811.2
Tunisia
270.6
91..5
1.2
201.1
564.3
Algeria
270.0
368.3
8.4
1,138.6
1,785.4
Morocco
1,016.1
186.5
4.1
553.9
1,760.6
Turkey
2591.5
1,818.8
48.8
6,173.9
10,633.0
Total
16,976
10,250
781
65,968
93,974
WASTEWATER REUSE IN THE NEAR EAST AND NORTH AFRICAN COUNTRY
Countries in the region which practice wastewater treatment and reuse include Jordan; Lebanon,
Tunisia, Israel, Kuwait, Emirates, Saudi Arabia, and Egypt (Choukr-Allah and Hamdy 2004). However,
only Tunisia, and to a certain extent, Jordan, already practice wastewater treatment and reuse as an
integral component of their water management and environmental protection strategies.
In Tunisia, treated effluent with a total flow 250 m3/day is used to irrigate about 4500 ha of
orchards (citrus, grapes, olives, peaches, pears, apples, and pomegranate), fodder, cotton, cereals,
golf courses and lawns (Abu-Zeid, 1998). The agricultural sector is the main user of treated
wastewater. Mobilisation of treated wastewater, and transfer or discharge is an integral part of the
national hydraulic equipment program and is the responsibility of the State, like all related projects.
The advantage of this water resource is that it is always available and can meet pressing needs for
irrigation water. Indeed use of wastewater saved citrus fruit when the resources dried up (overexploited groundwater) in the regions of Soukra (600 inhabitants) and Oued Souhil (360 inhabitants)
since 1960 and contributed among other things to the improvement of strategic crop production
(fodder and cereals) in new areas.
Technical and economic criteria enabled the irrigation of more than 6600 ha mobilising 30% of
discharged effluent. The average effective utilisation rate of treated wastewater is 20%. The volume
consumed differs greatly from one area to another, according to climatic conditions (11 to 21 Million
3
m per year.) At present, treated wastewater is an available source of water for farmers, but on the
one hand, it is not suitable for crops that are economically profitable, and on the other hand it poses
some health risks. The best levels of utilisation are found in fruit crops areas, in areas with a tradition
of irrigation and in semi arid areas.
3
With a projected volume of 215 million m by the year 2006, the utilisation potential of this water
will be about 20,000 hectares, which is 5% of the areas that can be irrigated, if we assume intensive
inter-seasonal storage and a massive introduction of water saving systems that would increase the
mobilisation rate to 45%. It is expected that additional treatment of treated wastewater will improve
the rate of use in irrigated areas (ONAS 2001).
118
Agricultural reuse however will not see marked improvement, unless restrictions are lifted on pilot
wastewater treatment plants with complementary treatment processes. This can only be decided
when the stations are functioning with acceptable reliability. This will take a few years of experience.
Nonetheless, in all cases, and regardless of the treatment method, technical and organizational
measures should be introduced in order to systematically warn those managing the reuse of any
breakdowns that may occur in the wastewater treatment plants and to avoid the flow of treated
wastewater into the distribution network.
In Jordan, Treated wastewater generated at nineteen existing wastewater treatment plants is an
important water resources component. About 72 MCM per year (2000) of treated wastewater are
effectively discharged into the watercourses or used for irrigation, 76% is generated from the biggest
waste stabilization pond Al-Samra treatment plant serving a population of 2 million (approximately
70% the total served population) in 2000. By the year 2020, when the population is projected to be
about 9.9 million, about 240 MCM per year of wastewater are expected to be generated. All of the
treated wastewater collected from the As-Samra wastewater treated plant is blended with fresh water
from the King Talal reservoir and used for unrestricted irrigation downstream in the Jordan Valley.
In Kuwait, the Government strategy for implementation of the Effluent Utilization Project was to
give the highest priority to development of irrigated agriculture by intensive cultivation in enclosed
farm complexes, together with environmental forestry in large areas of low-density, low water-demand
tree plantations. , the Ministry of Public Works initiated the preparation of a Master Plan for effective
use of all treated effluent in Kuwait, covering the period up to the year 2010 (Cobham and Johnson
1988). The overall plan recommendations for the western and northern sites (Jahra and Ardiyah
effluents, respectively) it was suggested that the first priority should be devoted to developing an
integrated system of forage (used in a high concentrate ration dairy enterprise) and extensive
vegetable production on the UAPC (the United Agricultural Production Company) farm, so that full
utilization would be made of existing and potential facilities as soon as possible. The ultimate project
design provides for the development of 2700 ha of intensive agriculture and 9000 ha of environmental
forestry (Agriculture Affairs and Fish Resources Authority, Kuwait 1988).
Saudi Arabia is currently reusing about 20 percent of its treated wastewater in refineries, for
flushing the toilets and for irrigating forage and landscape crops.
In Morocco, the reuse of raw wastewaters has become a current and old practice. They are reused
in agriculture in several parts the country. These practices are mainly localized to the periphery of
some big continental cities where agricultural lands are located in the downstream of effluent
discharge, and also in small parts around the wastes of the treatment networks. The climatic
constraints had pushed farmers to irrigate their crops with raw wastewater when water resources are
not available.
During the last years, the reuse of wastewaters has also developed around some suburbs recently
provided with a treatment network. A total of 7000 ha is directly irrigated with raw wastewaters
3
discharged by towns, i.e. about 70 million m of wastewater is used every year in agriculture with no
application of the sanitary precaution (HWO standards for example). This second use concerns a
diversity of cultivation types (fodder, cereals, fruit threes…).
The irrigation of vegetable crops with raw wastewaters is forbidden in Morocco, but this banning is
not respected, which makes the consumer of agricultural products and the farmer face risks of
bacteria or parasite contaminations. In general, the volume of wastewaters that have been recycled
does not represent more than 0.5% of the water used in Agriculture.
This situation tends to be generalized in all the suburbs that are provided with a treatment system
where wastewaters are discharged. Following an investigation carried out within the framework of
NSLC (1998), a total of 70 areas using wastewaters are spread out in the territory. This practice is not
free of dangerous consequences on human health and on environment. For example:
1- Spread of water diseases (more than 4000 cases of Typhoid and more than 200 case of malaria
have been noted in 1994, some cholera sources in the Sebou basin).
2- Difficulty and high cost in processing potable water.
119
3- Many section of water courses in the country present a largely weak quantity of dissolved oxygen,
and even a deficit in oxygen when these discharges are important, which causes massive fish
mortality, and;
4- Many dam volumes present marks of eutrophication, as a consequence of the important phosphor
and nitrogen wastes.
Since early nineties, many multidisciplinary projects concerning the treatment and reuse of
wastewater in irrigation have been launched in Morocco. The aim was to answer the major
agronomic, health, and environmental concerns. The results of these researches have made the local
collectivities and the regional agriculture services benefit from reliable data necessary to conceive and
to size the treatment plants of wastewaters adapted to the local contexts and to disseminate the best
practices for reusing treated wastewaters in agriculture.
In Egypt an ambitious programme is running for municipal wastewater treatment that will provide
3
by the year 2010 nearly 3 billions m /yr of treated wastewater as an additional water source to be
used in agriculture (Abu-Zeid, 1992).
WASTEWATER TREATEMENT TECHNOLOGY
The rural sector the entire Near East and North Africa has suffered from much neglect as far as its
sewage, wastewater treatment and wastewater reuse. The problem has become more acute in recent
years due to the sharp increase in the domestic water demand, due to the continued water shortage
and due to the strive to raise standard of living.
Falling behind in the wastewater management and reuse caused raw sewage to flow in the public
roads, thus causing contamination of ground water, local wells and drinking waters, creation of
nuisances and danger of public health with frequent outbreaks of water-borne diseases. Unauthorized
irrigation was the main source of cholera outbreaks in NENA countries with many hospitalized people
and many fatalities. Such outbreaks also caused a severe reduction in the tourism to some countries
and may have affected the tourist industry in these countries for several years.
Rural area communities in Near-East and North African countries have several features in
common that guide the design and operation of wastewater treatment plants, as follows:
1. Need for wastewater reuse for irrigation during the long dry summer months and the need for
seasonal storage of wastewater from winter to summer.
2. Usually enough inexpensive land area around and adjacent to the community is available.
3. Sunlight is usually abundant in these regions, giving advantage to photosynthetic and other solarenergy-dependent processes.
4. Relatively concentrated wastewater due to limited per-capita water consumption rate.
5. Relatively high pathogenicity of the wastewater due to endemicity of certain diseases and high
proportions of carriers.
6. Shortage of capital investment.
7. Absence, shortage or unreliability of electrical power.
8. Need for minimal, simple and inexpensive operation and maintenance of facilities.
Using the treated effluent for agricultural irrigation can increase the motivation for investments in
wastewater treatment plants. This will add an economical value force both for increasing capital
investments and the expenses needed for proper operation and maintenance of the wastewater
treatment facilities. Effluent quality aspects are also influenced by the decision to use the effluent for
irrigation, since the demand for high removal efficiency of pollutants like nitrogen and phosphorous
does not exist, while the treatment technology should be directed for high hygienic demands. By using
the effluent for controlled irrigation much of the environmental risks caused by other effluent disposal
alternatives (e.g. disposal to rivers, lakes, sea etc.) are prevented, so it is obvious that both the
farmers and the environment can be benefited from effluent reuse in small communities.
The selection of technologies should be environmentally sustainable, appropriate to the local
conditions, acceptable to the users, and affordable to those who have to pay for them. In developing
countries, western technology can be a more expensive and less reliable way to control pollution from
120
human domestic and industrial wastes. Simple solutions that are easily replicated, that allow further
up-grading with subsequent development and that can be operated and maintained by the local
community are often considered the most appropriate and cost effective. The choice of a technology
will depend to the type of reuse. The selection of reuse option should be made on a rational basis.
Reclaimed water is a valuable but a limited water resource; so investment costs should be
proportional to the value of the resource. Also, reuse site must be located as close as possible to the
wastewater treatment and storage facilities.
Indeed, the selection of the best available technology is not an easy process: it requires
comparative technical assessment of the different treatment processes, which have been recently and
successfully applied for prolonged periods of time, at full scale. However, this is not sufficient, the
selection should be carried out in view of well-established criteria comprising: average, or typical
efficiency and performance of the technology; reliability of the technology; institutional manageability,
financial sustainability; application in re-use scheme and regulation determinants. Furthermore, for
technology selection, other parameters have to be carefully considered: wastewater characteristics,
the treatment objectives as translated into desired effluent quality which is mainly related to the
expected use of the receiving water-bodies.
Presently there are a limited number of appropriate treatment processes for small communities,
which should be considered. These include stabilization ponds or lagoons, slow sand filters, land
treatment systems, and constructed wetlands. All of these fit the operability criteria discussed above,
and to varying degrees, are affordable to build and reliable in their treatment performance. In order to
illustrate the viability of these systems, the following example is provided. In this example, a small
sewered community collects its wastewater at the treatment site, and the effluent will be required to
meet WHO standards for unrestricted agricultural irrigation.
If a pond system were chosen, WHO offers a waiver from the criteria. However, many researchers
have found a high variability in their capability to consistently meet WHO microbiological criteria.
Therefore, the designer may wish to supplement the ponds with a tertiary system to meet the criteria
consistently. Appropriate stabilization pond upgrading methods to meet WHO reuse standards include
free-water-surface (FWS) constructed wetlands, which can provide both the detention time of required
maturation ponds of the same size and removal of algae from the pond effluent which can clog some
irrigation systems; intermittent sand filters, which remove the parasite eggs and faecal coliforms, and
slow-rate infiltration (SRI) and rapid infiltration (RI) systems. The latter two systems, however,
transport their purified effluent to the groundwater, where it normally must be pumped back to the
surface for irrigation use. A stabilization pond system can also be upgraded by a floating aquatic
plant system in the same manner as the FWS constructed wetland. Such a system will, however,
significantly increase operational requirements.
Intermittent sand filters (ISF) are capable of meeting the parasite and faecal coliforms criteria, but
the recirculating sand filters (RSF) have not yet been shown to do so. The latter are more compact
and capable of significant nitrogen removal, but require mechanical equipment in the form of pumps.
Subsurface soil infiltration (SWIS), slow rate infiltration (SRI) and rapid infiltration (RI) systems can
also meet the criteria, but will require pumping energy, since all three transport their effluents to the
groundwater. A listing of potential cost effective alternatives which accomplish the example treatment
task by providing reusable water at the surface without the need for electrical equipment are:
1. Stabilization ponds + FWS constructed wetland
2. Anaerobic (high rate) ponds + ISF
3. Imhoff tanks + ISF
Analysis of the above appropriate treatment technology systems in greater depth can assist future
designers of small community wastewater systems to understand some of the tradeoffs and areas of
uncertainty. Among the issues, which may sway the choice of treatment systems are performance,
reliability, area requirements, capital and construction costs, and socio-economic issues.
Area requirements for these systems to treat 100 m3/d of wastewater are estimated and reported
in Table 4.
121
Table 4. Area required for the three systems.
System
Stabilization ponds + FWS constructed wetland
Anaerobic (high rate) ponds + ISF
Imhoff tanks + ISF
2
Area Required (m )
13,300
1,950
1,850
Both filter based systems require only a small fraction (about 15%) of the area required for the
pond/constructed wetland system. Even if one were to accept the conclusion that a series of ponds
can meet unrestricted irrigation standards, the area requirement is still about 7-times that required by
the ISF systems.
In terms of performance or removal of pollutants the two options can only be compared when the
ultimate use of the effluent is known, thus providing a specific need. In the case of irrigation reuse
this involves the crop(s) to be irrigated, the aquifer characteristics below the crop, the soil, the method
of irrigation and the irrigation water demand pattern. Each type of crop has different tolerances for
certain pollutants, specific patterns for nutrient demand and limitations, and different patterns of
demand for irrigation water. Unconfined aquifers of limited capacity will be much more sensitive to
irrigation water constituents which escape the root zone and are flushed to the aquifer surface, than
would be a confined aquifer or one of greater volume. Similarly, certain soils are more capable of
removing dissolved constituents than others due to their physical and chemical characteristics and
prior history of use. Also, the microbiological requirements for subsurface drip irrigation are far less
severe than surface distribution methods.
Traditional criteria used for pond design are not normally of great importance in water-short areas
like North Africa, since ponds are designed for BOD removal, not faecal coliforms or parasitic egg
removal, the removals of faecal coliforms and nematode eggs control the design. Only when a
wastewater with a very high BOD (800 mg/l or more) should BOD removal model be considered.
Since the removal of pathogens is a time-related relationship, substitution of a FWS constructed
wetland for some of the maturation-pond time required in the lagoon system should be feasible,
however no studies have yet determined exactly what the equivalency ratio is.
To meet WHO standards the total required retention times for a typical stabilization pond-treated
influent to meet WHO standards, and for different parameters at 20°C are reported in Table 5.
Table 5. Required retention times for different parameters regarding WHO standards
Parameter
BOD, mg/l
Fecal Coli, per 100 ml
Nematode Eggs, per liter
Days
5
16
18
Reference
Reed and Middle brooks. 1995
Marais, GVR. 1970
Ayres, and al. 1992
In summarizing the options for a small community the choice of treatment for ultimate reuse will
hinge on the following:
- Reuse Requirements - If the reused wastewater is to be used for vegetables, citrus or other crops
to be eaten raw, the options employing stabilization ponds and intermittent filters can be used, or a
recirculating filter may be substituted with subsurface drip irrigation only. This last restriction may be
lifted if it can be proven that the RSF effluent is free of nematode eggs, or if disinfection of the effluent
is employed.
- Land Availability - If sufficient land is available the other limitations stated above and below will
control the options evaluated. If land availability is limited by economics or terrain or surrounding
development, one of the filter options should be chosen.
- Operational Capability - If a sufficiently skilled management program with electricity is available,
all options are possible. If, as is often the case, only unskilled labour is locally available, only the
pond-wetland or anaerobic lagoon-intermittent filter options are viable.
122
Table 6. Comparison of the two passive alternative technologies
Lagoon-Wetland
Land requirement, m2
Energy KWH/d
Capital cost, US$
O&M cost, US$/yr.
Effluent Quality
BOD5 (in=200), mg/l
TSS (in=100), mg/l
TN (in=50), mg/l
TP (in=10), mg/l
FC (in=106), per 100 ml
Virus (in=103), per L
Parasite Ova (in=103), per L
13,000
0
200,000
250,000
5,000-7,000
10
10
10-35
7-8
102-103
101-102
0-10
Anaerobic Lagoon-ISF
2,000
0
150,000
200,000
7,000-10,000
5
5
35-40
7-9
101-102
0-10
0
Finally, when the viable options which pass the above tests are evaluated against each other,
experience in the Morocco has shown that they are very similar in present worth cost, so local
availability or cost of components, climatic and social conditions, and support infrastructure may be
the deciding factor between them. For example, the lack of suitable sand or substitute media locally
will significantly increase the cost of the filter options. Very close proximity of housing to the treatment
site may make odour concerns a key issue, and add costs to certain options to control odours.
Therefore, engineering decisions of which method of treatment or sitting of the facility may be skewed
to suit local needs. However, in all cases the appropriate technology options presented herein are
significantly more sustainable than the use of sophisticated urban wastewater treatment technologies
such as activated sludge with tertiary treatment for small communities of NENA region.
CONSTRAINTS OF THE REUSE
Bearing in mind that treated wastewater could be used for agricultural purposes, it is important to
realize that such wastewater must be adequately treated and used appropriately. The main
constraints of using treated wastewaters are related to health issues, the absence of effective
wastewater standards, the of law enforcement, lack of awareness and scarcity of funds.
Wastewater quality and health issues
Irrigating with untreated wastewater poses serious public health risks, as sewage is a major source
of excreted pathogens - the bacteria, viruses, protozoa- and the helminths (worms) that cause gastrointestinal infections in human beings (Blumentha and al 2000).
Unregulated and continuous irrigation with sewage water may also lead to problems such as soil
structure deterioration (soil clogging), salinization and phytotoxicity.
The ideal solution is to ensure full treatment of the wastewater to meet WHO guidelines prior to
use, even though the appropriateness of these guidelines are still under discussion. However, in
practice most rural villages in NENA countries are not able to treat their wastewater, due to low
financial, technical and/or managerial capacity. In many rural areas a large part of the wastewater is
disposed of untreated to rivers and cesspools, with all related environmental consequences and
health risks. The perspectives regarding treatment of their wastewater are bleak. It may safely be
assumed that the farmers increasingly will use wastewater for irrigation, irrespective of the national
regulations and quality standards for irrigation water.
In any case, usually, sewage treatment plants rarely operate satisfactorily and, in most cases,
wastewater discharges exceed legal and/or hygienically acceptable maxima. This does not
necessarily lie in the treatment plants themselves, but in the frequent lack of adequately trained
technicians capable of technically operating such treatment plants.
123
The discharge of untreated wastewater and/or minimally treated in water sources has resulted in a
substantial economic damage and has posed serious health hazards to the inhabitants, particularly in
the low income NENA countries.
This is now the case in many mega-cities where the drinking water supplies from rivers or local
groundwater sources are no longer sufficient, mostly because of their poor quality.
The lack of sanitation facilities and the too often associated unsafe drinking waters remain among
the principal causes of disease and death, especially in rural areas. Specific measures to counteract
water-related threats are often needed, but, lack of investments and inadequate local management
often lower their effectiveness.
Institutional manageability
The scope and success of any effluent use scheme will depend to large extent on the
administration skills applied. Wastewater reuse is characterised by the involvement of several
departments and agencies, either governmental or private or both. In the NENA countries, few
governmental agencies are adequately equipped for wastewater management. In order to plan,
design, construct, operate and maintain treatment plants, appropriate technical and managerial
expertise must be present. This could require the availability of a substantial number of engineers,
access to a local network of research for scientific support and problem solving, access to good
quality laboratories and monitoring system and experience in management and cost recovery. In
addition, all technologies, included the simple ones, require devoted and experienced operators and
technicians who must be generated through extensive education and training.
For adequate operation and minimization of administrative conflicts, a tight coordination should be
well defined among the Ministries involved such as those of Agriculture, Health, Water Resources,
Finance, Economy, Planning, Environmental Protection and Rural Development. The basic
responsibilities of such inter-ministerial committees could be outlined in:
• Developing a coherent national policy for wastewater use and monitoring of its implementation;
• Defining the division of responsibilities between the respective Ministries and agencies
involved and the arrangements for collaboration between them;
• Appraising proposed re-use schemes, particularly from the point of view of public health and
environmental protection;
• Overseeing the promotion and enforcement of national legislation and codes of practice;
• Developing a national staff development policy for the sector;
Financial considerations
The lower the financial cost, the more attractive is the technology. However, even a low cost option
may not be financially sustainable because this is determined by the true availability of funds provided
by the polluter. In the case of domestic sanitation, the people must be willing and able to cover at
least the operation and maintenance cost of the total expenses. The ultimate goal should be full cost
recovery although, initially, this may need special financing schemes, such as cross subsidization,
revolving funds and phased investment programmes.
In this regard, adopting an adequate policy for the pricing of water is of fundamental importance in
the sustainability of wastewater re-use systems. Subsidizing re-use system may be necessary at the
early stages of system implementation, particularly when the associated costs are very large. This
would avoid any discouragement to users arising from the permitted use of the treated wastewater.
However, setting an appropriate mechanism for wastewater tariff is a very complex issue. Direct
benefits of wastewater use are relatively easy to evaluate, whereas, the indirect effects are “non
monetary issues” and, unfortunately, they are not taken into account when performing economic
appraisals of projects involving wastewater use. However, the environmental enhancement provided
by wastewater use, particularly in terms of preservation of water resources, improvement of the health
status of poor populations in rural areas, the possibilities of providing a substitute for freshwater in
124
water scarce areas, and the incentives provided for the construction of sewerage networks, are
extremely relevant. They are also sufficiently important to make the cost benefit analysis purely
subsidiary when taking a decision on the implementation of wastewater re-use systems, particularly in
poor and rapidly growing rural villages.
Monitoring and Evaluation
Monitoring and evaluation of wastewater use programmes and projects is a very critical issue,
hence, both are the fundamental bases for setting the proper wastewater use and management
strategies. Ignoring monitoring evaluation parameters and/or performing monitoring not regularly and
correctly could result in serious negative impacts on health, water quality and environmental and
ecological sustainability.
Unfortunately, in many MENA countries that are already using or start using treated wastewater as
an additional water source, the monitoring and evaluation programme aspects are not well developed,
are loose and irregular. This is mainly due to the weak institutions, the shortage of trained personnel
capable of carrying the job, lack of monitoring equipment and the relatively high cost required for
monitoring processes.
Public awareness and participation
This is the bottleneck governing the wastewater use and its perspective progress. To achieve
general acceptance of re-use schemes, it is of fundamental importance to have active public
involvement from the planning phase through the full implementation process.
Farmers will need to be convinced that treated wastewater can provide an attractive resource and
they can save money through reducing the fertilizer application.
Some observations regarding social acceptance are pertinent. For instance, there may be deeprooted socio-cultural barriers to wastewater re-use. However, to overcome such an obstacle, major
efforts are to be carried out by the responsible agencies.
Responsible agencies have an important role to play in providing the concerned public with a clear
understanding of the quality of the treated wastewater and how it is to be used; confidence in the local
management of the public utilities and in the application of locally accepted technology, assurance
that the re-use application being considered will involve minimal health risks and minimal detrimental
effects on the environment.
In this regard, the continuous exchange of information between authorities and public
representatives ensures that the adoption of specific water re-use programme will fulfill real user
needs and generally recognized community goals for health, safety, ecological concerns programme,
cost, etc.
In this way, initial reservations are likely to be overcome over a short period. Simultaneously, some
progressive users could be persuaded to re-use wastewater as supplementary source for irrigation.
Their success would go a long way in persuading the initial doubters to re-use the wastewater
available.
Realistic Standards and Regulations
An important element in the sustainable use of wastewater is the formulation of realistic standards
and regulations. However, the standards must be achievable and the regulations enforceable.
Unrealistic standards and non-enforceable regulations may do more harm than having no
standards and regulations because they create an attitude of indifference towards rules and
regulations in general, both among polluters and administrators. As the WHO microbiological
guidelines expect certain levels of wastewater treatment, their enforcement in situations without any
realistic option for treatment would stop hundreds or thousands of farmers from irrigating along
125
increasingly polluted streams, and put their livelihoods at risk, but would also affect food traders and
general market supply.
Without question, the enforcement of microbiological guidelines or crop restrictions remains
important, but a better balance between safeguarding consumers’ (and farmers’) health and
safeguarding farmers’ livelihoods should be made, especially in situations where the required water
treatment or agronomic changes are unrealistic. However, further research is needed into hygienic
food marketing as well as the safe food preparation at home as important options to tackle the
wastewater problem in low-income countries.
Most often, WHO guidelines have often been used, or cited in isolation from the other protective
measures. If water quality, however, cannot be guaranteed, agricultural engineers should investigate
possibilities of alternative irrigation technologies and irrigation methods reducing farmer’s exposure.
Also, in certain case additional treatment (up to tertiary level) to remove crop restrictions will help
change farmers attitude, as this will allow them to grow cash crops (vegetables).
STRATEGIES FOR SUSTAINABLE REUSE IN RURAL AREAS
In order to achieve safe and successful wastewater reuse schemes for irrigation purposes, WHO
health guidelines should be integrated with FAO for water quality guidelines for irrigation purposes.
Accordingly there are common multi strategies ultimately combined the optimisation of crop
production and protecting the human heath. These are related to wastewater treatment level,
restriction of the crop to be grown, irrigation techniques and scheduling, as well as to control of soil
salt accumulation, ground water nitrogen pollution.
Adequate treatment technology
The implementation of low cost treatment is recommended. Properly designed, adequately
implemented wastewater reuse is an environmental protection measure that is superior to discharge
treated wastewater to its end use of the reclaimed effluent need to meet the guidelines, taking into
consideration the economic constrains. Usually the wastewater of rural population does not contain
heavy metal, which means that the main concern of treatment will focus on the pathogens removal.
Several technologies have been described in this paper to be adapted on the socio-economic
conditions of the local population.
Crop selection
Based on the WHO guidelines, crops to be used grouped in three categories (A, B, and C)
depending on the degree to which health protection measures are required. Secondary effluent allow
the cultivation of green fodder, olives, citrus, bananas, almonds, and even to be used as supplement
irrigation for cereal crops. However, crop selection should be subject to their tolerance to salinity, soil
characteristics, and the risks of ground water pollution.
Irrigation techniques and scheduling
The selection of irrigation techniques mainly depends on the quality of the effluent, the crop
patterns, and the potential health risks. Irrigation techniques, which wet only the roots and not the
leafy part of vegetables, were suggested as good practice for minimizing risk of contamination. Bed
and furrow irrigation, drip systems and any other technique applying water close to the root systems
was suggested. There is a further advantage in that there will be less infiltration of nitrogen into
groundwater (Mojtahid and al 2001). Rotating wastewater application over fields if this is possible is
another means to limit over-fertilisation and pollution of groundwater. Avoiding irrigation with
wastewater in the two weeks before harvest can minimize the risk from pathogen contamination of
leafy vegetables, but this necessitates a fresh water source accessible to farmers, which is rarely
possible in these rural situations.
126
Control of nitrogen pollution and salt accumulation
Farmers should calculate the amount of nitrogen needed taking into account the amount of
nitrogen supplied by the treated wastewater. Some crops are highly effective in removing nitrogen
from soil, which may contaminate underground water. Sudan grass, Rhodes grass, maize, sorghum
remove nitrogen efficiently from the soil.
High sodium levels in treated wastewater can reduce water infiltration in heavy clay soil, and
could not be tolerated by salt sensitive crops. Gypsum and organic amendment will reduce the
negative effect of the sodium on the soil structure and improve crop productivity under these
conditions. Also the use of more tolerant species, associated with some good practices (irrigation
techniques, leaching ….) will reduce the salt effect on the crop yield.
CONCLUSION AND RECOMMENDATIONS
Domestic WWTR is one tool to address the food and water insecurity facing many countries in the
Near East and North Africa. In coming years, in most NENA countries, valuable fresh water will have
to be preserved solely for drinking, very high value industrial purposes, and for high value fresh
vegetables crops consumed raw. Where feasible, most crops in arid countries will have to be grown
increasingly, and eventually solely, with treated wastewater. The economic, social and environmental
benefits of such an approach are clear. To help the gradual and coherent introduction of such a
policy, which protects the environment and public health, governments shall have to adapt an
Integrated Water Management approach, facilitate public participation, disseminate existing
knowledge, and generate new knowledge, and monitor and enforce standards.
Awareness and information efforts targeted at farming communities, including in particular at
women, improved specialized extension services and assistance in marketing crops grown under safe
planned reuse schemes be useful steps in improving reuse.
To ensure the sustainability of the system, a cost recovery analysis should not be neglected. The
low income of most farmers, it is not realistic to expect farmers to pay any portion of the treatment
cost, but tariffs should cover the cost of transferring and distribution of the reclaimed water.
On the technology side, small-scale decentralized sanitation technology, such as lagoons, sand
filters, constructed wetland, and even septic tanks combined with small-bore sewers, offer great
potential in small rural areas. As far as irrigation technologies are concerned, bubbler irrigation may
be considered the preferred method of application particularly for tree crops. It provides some water
savings, and also provides some degree of protection against clogging and contamination exposure.
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128
PLANNING FOR WASTEWATER REUSE
F. Fresa *, F. Melli **, A.F. Piccinni *, V. Santandrea *** and V. Specchio *
* Polytechnic of Bari, via E. Orabona 4 70126 Bari – [email protected]
** SOGESID s.p.a.,
*** IPRES Istituto Pugliese di Ricerche Economiche e Sociali
SUMMARY- This paper presents the results of a research work aimed at defining useful criteria for
planning treated wastewater reuse. All the possible forms of reuse are preliminarily analysed,
supplementary treatments required for different uses are identified according to reclaimed water
characteristics, and the additional costs required to adjust the treatment plants to the reuse purposes
are estimated; the implications related both to the organizational and management problems of the
treatment-reclamation system and to the methodological and technical aspects relative to waterpricing policies are also analysed.
INTRODUCTION
Faced with worsening environmental problems, planning and management strategies of
wastewater reuse both as an additional resource to keep up with increasing demand and as
environmental protection tool to turn wastes into resources are a must.
Correct knowledge of the dynamics related to water reuse and the resulting possible scenarios are
a prerequisite for correct planning of actions on the territory; local as well as regional and national
planning has necessarily to consider problems related to the definition of wastewater quality
standards and optimal treatments to make waters adequate for different uses, to the definition of the
environmental benefits and risks related to reuse policies and, in cost-benefit terms, to the
identification of an economic return threshold for the required reuse works to be implemented.
In that sense, the main obstacle to treated wastewater reuse is the treated wastewater cost to be
charged to users, since distribution costs add up to treatment costs. On the contrary, if we consider
reuse as a wastewater disposal tool, or better to say a “non-disposal” tool, in that it is by itself an
environmental benefit, it can be assumed that part of treatment costs should be borne by the
community, that being the primary beneficiary of pollution abatement. Such an assumption is in line
with the Directive 2000/60/EEC (that establishes a framework for the community action in the matter
of waters and that follows on the directive 91/271/EEC) where art. 9 (Recovery of costs for water
services) states in paragraph 1: “Member states shall take account of the principle of recovery of the
costs of water services, including environmental costs …, and in accordance in particular with the
polluter pays principle”
Such preliminary remarks that anticipate some of the conclusions of this paper, are needed to
justify the spirit and approach of this work that moves through broad though not fully and explicitly
reported evaluations to recognize wastewater reuse an environmental rather than an economicproduction value. In agriculture, for instance, wastewater reuse will be a small amount of the resource
globally necessary but it will be strategic for some areas with severe water scarcity. The strategic
value of such a resource is related to its being a substitute for the water currently used, thereby
contributing to reduce indiscriminate abstraction. Of course, in areas subject to significant
groundwater withdrawal, the use of wastewater has to be accompanied by a plan to prevent on-going
abstraction.
SECTORS OF POSSIBLE REUSE
The possible sectors of wastewater reuse mainly fall into four categories: agricultural, industrial,
urban and environmental-recreational. Table 1 shows the main uses within each of these categories
each of them having specific and different characteristics both in terms of water quality and
distribution modes, with inevitable effects on the technologies to be adopted (starting from advanced
treatments downstream the standard treatment).
129
In any case, implementing wastewater reuse requires defining quality criteria to comply with two
fundamental conditions:
−
−
To make water suitable for the specified reuse;
To protect in any case the involved population and workers from direct or indirect sanitary risks
related to reuse as well as, more generally, to protect the environment from contamination
risks.
Table 1. Reuse categories – major risks and constraints
AGRICULTURAL
CATEGORIES OF REUSE
Wood production
Fodder production
Fruit production
Production of processed and cooked food
Production of food to be eaten fresh
LANDSCAPE
Irrigation of public and private green areas
Municipal uses (water closet effluents)
Wash of roads, buildings, vehicles
INDUSTRIAL
ENVIRONMENTAL
Air conditioning
Groundwater recharge
Control of salt water intrusion
Control of subsidence phenomena
Artificial wetland or supply in wetland
Impoundments and ponds for recreational purposes
(fishing, bathing…)
Cooling water
Boiler feed water
Process water
MAJOR RISKS AND CONSTRAINTS
TO DEFINE EFFLUENT QUALITY
REQUIREMENTS AND MODES OF
USE
Possible health-sanitary risks due to
the presence of pathogens (viruses,
bacteria and parasites); possible soil
and groundwater pollution (persistent
organic compounds, nitrates, metals,
dissolved solids); product acceptability
on the market
Possible health/sanitary risks due to
the presence of pathogens; corrosion
effects, dirtying and plugging of
delivery systems; possible
interconnection with drinking water
waterworks with possible resulting
health/sanitary risks
Possible health/sanitary risks due to
the presence of pathogens; possible
groundwater pollution.
Possible eutrophication; toxicity to
aquatic life
Possible health/sanitary risks for the
production of aerosols in cooling
towers; effects of corrosion, dirtying
and plugging; interference in the
process.
In the economic analysis we considered the types of reuse more easily feasible, among the
reported ones, and for which the economic factor plays a fundamental role, that is agricultural and
industrial reuse.
In the case of reuse for industrial purposes, the operation cycle of facilities can be planned on
yearly basis, whereas reuse for agricultural purposes concentrates the regime operation cycle of
facilities in the irrigation season that generally extends from April to October, each month having
different climatic patterns and precipitation regimes. In the framework of optimal management of
reused water for irrigation purposes, reuse could serve to meet the basic demand and water from
other sources could supplement the water resource in peak periods: we refer to such practice as
“supplemented irrigation”; as explained later, it allows reusing greater amounts as compared to the
assumption of meeting the irrigation demand through wastewater only.
The following tables gives the monthly consumption coefficients used in the three assumptions of
use and the resulting reuse potential. Of course, the reuse potential with respect to the discharge
potential is minimum in the case of reuse for irrigation, and maximum in the case of reuse for industry.
130
Table 2. Consumption coefficients per type of use
Months
Irrigation (%) (1)
Supplemented
irrigation (%)
Industrial
April
May
June
July
August
September
October
0.22
0.61
0.96
1.00
0.96
0.48
0.13
0.36
1.00
1.00
1.00
1.00
0.80
0.20
300 days/year
(1) Viparelli’s assumption, 1981
Based on these assumptions, the reuse potential is lower than the discharge potential in a
percentage that differs depending on the type of use (Table 3).
Table 3. Reuse potential with respect to the discharge of facilities
Type of use
% rate of use
Industrial
82.1
Supplemented irrigation
44.2
Irrigation
34.0
POTENTIALS OF REUSE FACILITIES
The economic evaluation of the cost of reuse, both in terms of investment and of management
costs, was performed on the basis of the type of reuse (irrigation and industry) as well as of the plant
potentials, of the pre-existing treatment chain, of the possible supplemental treatment technologies
depending on the quality of discharge (into the soil or receiving water) and of operational
environmental conditions.
Facilities were subdivided into two macro-categories, depending on the effluent quality threshold
levels and thus of the treatment components required to achieve them:
−
−
Type A facilities: those for which effluents are discharged into large receiving water or into the
sea and where the effluent denitrification and tertiary treatment unit is not present;
Type B facilities: those for which effluents are discharged into the soil, and where effluent
denitrification and tertiary treatment are present (filtration).
Then, wastewater treatment facilities were subdivided into potential classes, determined according
to the number of inhabitants served and of three assumptions of water discharge, defined on the
basis of the assigned water supply value, “low”, DI1, “medium”, DI2, and “high”, DI3 (Table 4).
Table 4. Values of water supply assumed in the computation example. Values are expressed in
litre/inhabitant*day.
Population
class
Number of inhabitants
Computation assumption
DI1
DI2
DI3
1
Smaller than or equal to 10,000
250
300
350
2
Greater than 10,000 and smaller than or equal
to 100,000
350
400
450
3
Greater than 100,000
450
500
550
131
Actions to adapt the effluent treatment lines for reuse were defined by taking as a “basic” facility a
scheme that ensures biological removal of biodegradable organic matter, diversified by the presence
or absence of primary sedimentation and of the tertiary treatment stage related to the quality of
discharge.
Based on the pollutant concentration limits established under the European regulation in force and
taking into account “conventional” technologies and treatment processes, the following supplementary
treatment stages were considered:
−
−
Biological stage to remove nitrogen;
Chemico-physical stage to remove fine solids and pathogenic micro-organisms.
The first treatment is assumed to be implemented by integrating an active sludge scheme with a
pre-denitrification stage; the second treatment is assumed to be accomplished through “direct”
filtration on granular beds, with in line coagulation, followed by a disinfection stage.
In particular, for the filtration stage, economic comparisons led to choose pressure filters for class
1 and class 2 facilities, and gravity filters for higher potential facilities, i.e. class 3.
As for disinfection, two different treatment lines were analysed: the first one included only one
chlorination stage, whereas the second one included two stages in series: a stage with ultraviolet
radiations followed by a stage with the addition of peracetic acid as safety disinfectant.
We didn’t consider the adaptation interventions relative to the processing units that do not require
substantial additional building or operational works, like the primary and secondary sedimentation
stages and the whole sludge treatment line. In this respect, we should consider that for the
considered facility schemes, the increase in sludge production, attributable to greater efficiency in the
removal of suspended solids, is substantially compensated by lesser production of biological sludge
as a result of older sludge adopted in nitrification-denitrification processes.
Finally, assuming reuse for irrigation purposes, the nitrification-denitrification process was
designed for an average temperature of 20°C (reuse in the spring-summer period), whereas in the
case of industrial reuse (all year around) the design temperature was assumed to be 13-15°C in the
winter period and constantly 20°C under summer operation conditions. This differentiation resulted in
a considerable increase of the denitrification volume since these processes highly depend on
temperature.
In the Table 5, the supplementary actions to comply with the limits for reuse established under the
Italian regulation are reported according to the effluent quality of the existing treatment facility.
Table 5. Conventional treatments required for adapting treatment facilities depending on the
discharge quality for reuse purposes.
Treatment stages required for
complying with the effluent quality
limits for reuse
Biological
treatments
Chemicophysical
treatments
132
Nitrogen
removal
Quality of treated discharge
Type A
Type B
Nitrification
REQUIRED
NOT REQUIRED
Denitrification
REQUIRED
NOT REQUIRED
REQUIRED
NOT REQUIRED
REQUIRED
POSSIBLE ADAPTATION
Defosfatation
Removal of
Filtration
suspended
Coagulation
solids
Disinfection
REQUIRED
ADAPTATION
TECHNICAL-ECONOMIC ANALYSIS
The technical-economic analysis was performed referring to the cost indexes of 2004 and thus, the
corresponding costs were assessed as to that date; the use of the data referred to different time
horizons have to be discounted through adjustment indexes. However, this is a marginal aspect since
the aim of this research is to define planning criteria for wastewater reuse, and comparing scenarios
is thus more important than considering the absolute value of each single cost unit. The analysis of
wastewater treatment facilities concerned:
a)
b)
The identification and estimate of the additional costs required to adapt treatment facilities,
depending on the effluent quality (Type A/Type B), to the parameters imposed for reuse;
Aspects related both to the organization and management problems of the treatment-reclamation
system and to the methodological and technical aspects relative to water-pricing policies.
Such a distinction is important in that, for the time being and in theory, it is possible to have three
different management bodies for the reuse cycle: one for the treatment facilities, another for the reuse
facilities and another one for the facilities of use. Of course, such a structure should not affect the
fixation of cost regimes and, consequently, of water-pricing.
Cost analysis was based on the assumption of considering not the capital and management costs
of a completely new reclamation facility, but the additional capital and management costs to reach,
from standard quality parameters effluent, the reference parameters for reuse. Cost analysis has
taken into consideration the “additional” treatment for reuse (Table 6), subdivided into two major
items:
−
−
Investment/capital costs, estimated as a function of public funding or through borrowing
from the financial market;
Operational costs
and further broken down into:
−
−
Fixed costs, i.e. the costs independent of the type of reuse: the costs falling within this
category are those that do not vary in size with the variation of the amount of reuse of
treated effluents;
Variable costs, i.e. the costs dependent on the kind of final use: the costs that fall within this
category are those that vary in size with the variation of the amount of reuse of treated
effluents.
Table 6. Breakdown of additional costs
FIXED COSTS
•
•
Capital costs/ Financial costs
Building works
Electromechanical supplies
•
•
Operational costs
Personnel
Maintenance and replacement of parts
VARIABLE COSTS
•
•
Operational costs
Energy costs
Reactants
Table 7 shows the different additional cost items of treatment stations.
133
BUILDING WORKS
ADAPTATION OF
FACILITIES
CONSUMPTION OF
CHEMICAL
REACTANTS
POWER
CONSUMPTION
---
MIXING OF
BIOLOGICAL SLUDGE
---
ADDITIONAL
AERATION
RECIRCULATION OF MIXED LIQUOR AND
SLUDGE
SUBMERGED MIXERS
INCREASED
AERATION
(COMPRESSORS
AND
DIFFUSERS)
PRECIPITATION
OF
PHOSPHORUS
DOSAGE AND
MIXING OF
REACTANTS
DOSAGE OF
REACTANTS
ACCUMULATION
OF REACTANTS
COAGULATION
AGENT
DOSAGE AND
MIXING OF
REACTANTS
METER PUMP
OF REACTANTS
AND RAPID
MIXER
TANK OF RAPID
MIXTURE OF
REACTANTS
---
---
BACKWASHING
OF FILTERS
LIFTING FOR
PRESSURIZED
SUPPLY
BACKWASHING
UNIT
FEED PUMPS
PRESSURIZED
RESERVOIRS
BACKWASHING
TANKS
---
INCREASE IN
VOLUME OF THE
OXIDATION
REACTOR
---
BACKWASING
OF FILTERS
BACKWASHING
FACILITIES
FILTRATION
TANKS AND
FITTINGS
GRAVITY
FILTERS
PRESSURE
FILTERS
COAGULATION
CHEMICAL
PRECIPITATION
NITRIFICATION
RECIRCULATION OF MIXED LIQUOUR
AND INCREASE IN SLUDGE RECYCLE
REACTOR
PRE-DENITRIFICATION
SUSPENDED SOLIDS REMOVAL
CHEMICO-PHYSICAL TREATMENTS
WATER TREATMENT PROCESSE S
REMOVAL OF
PHOSPHORUS
REMOVAL OF ORGANIC MATTER AND
NITROGEN
BIOLOGICAL TREATMENT
Table 7. Cost items of treatment stations
COSTS
INVESTMENT COSTS
OPERATION COSTS
ELECTROMECHANICAL
SUPPLIES
134
INCREASE IN
RADIATION
PRODUCTION
---
INCREASE IN THE
DISINFECTANT
AGENT AND
REACTANTS
DECHLORINATION
INGCREASING
RADIANT
LAMPS
INCREASING
CONTACT
TANKS
ULTRAVIOLET
RADIATION
----
----
INCREASING
CONTACT TANK
CHLORINE
COMPOUNDS
ADDITION
DISINFECTION
Analysis of capital costs
Capital costs analysis has taken into consideration the building works and electromechanical
supplies. The costs of building works are evaluated net of possible costs for expropriating new areas.
The considered works are illustrated in the following box:
Table 8. Schematic capital costs* analysis
Types of costs
Building works
Excavation / backfills, impoundments, flooring
asphalt, fencing
Pressure filters
Gravity filters
Electromechanical supplies
blowers
mixers
mixed liquor pumps
pressurized filtration:
− filters
- lifting plant for filtration
− lifting plant for backwashing
− blowers
gravity filtration:
− nozzles
− hydraulic valves
− electrical facilities
− lifting plant for filters
− lifting plant for backwashing
− filter blowers
− miscellaneous
UV lamps
Electromechanical supplies relative to reactants:
Meter pump
Measurement
Unit
Unit cost
€
€/m3
150
€/m3
€/m3
150
400
€/Nm3/g
€/N
€/KWh
min 0.21-max 2.81
min 5.08–max 16.67
min 5.05-max 16.66
€/m2
€/kWh
€/kWh
Nm3/g
min 8,560-max 10,700
min 648-max 1,500
min 648-max 1,500
min 0.21-max 2.81
units
€/filter
€/filter
€/kWh
€/kWh
nm3g
€/m3
units
0.70
15,000
1,500
min 648-max 1,500
min 648-max 1,500
min 0.21-max 2.81
4,80
min 2,500-max 11,750
units
900
/
N.B. for type B facilities the additional costs concern UV lamps and dosage unit
Table 9. Adaptation costs of type A facilities
Facility
potential (AE)
Building works
[€]
Electromechanical
supplies
[€]
Total
[€]
2,000
33,835
114,862
148,697
5,000
84,588
172,223
256,811
10,000
169,176
210,153
379,329
20,000
330,496
438,532
769,028
30,000
495,744
615,104
1,110,847
40,000
633,792
779,777
1,413,568
50,000
792,240
955,307
1,747,547
70,000
1,109,135
1,301,753
2,410,888
100,000
1,584,479
1,722,855
3,307,334
250,000
6,089,005
1,645,931
7,734,936
500,000
11,430,915
2,010,982
13,441,897
135
The minimum and maximum values indicated in the table basically depend on the potential of
facilities.
Based on such assumptions, the costs of investments were determined separately for the building
works and for electromechanical supplies depending on the size of facilities per IE. Table 9 gives, for
instance, the results obtained in the case of adaptation of type A facilities and assuming a more
onerous operation of the existing facility, that is in the presence of primary treatment, at a
temperature of 15°C, assuming to adopt the UV + peracetic acid scheme for disinfection.
Based on the previous results, the cost of investments per IE was determined, again assuming
type A facilities.
Table 10. Unit adaptation costs of type A facilities - €/IE
Type of biological treatment / IE
2,000
50,000
500,000
15°
20°
15°
20°
15°
20°
With primary treatment
74.35
65.85
34.95
26.97
26.88
20.01
Without primary treatment
78.57
66.93
38.43
28.82
31.61
19.80
These results point to:
1. a considerable difference in the cost per inhabitant equivalent depending on the size of
facilities (difference of about 50 euros between small and bigger size facilities);
2. the cost difference (€/IE), depending on the presence or absence of primary sedimentation,
ranges between 12.9% and 34.4% at 15°, between 17,4% and 59.6% at 20°.
Similarly for type B facilities, considering the costs given in table 4.3, the investments costs briefly
illustrated in table 4.6 are obtained.
Table 11. Additional costs for the adaptation of type B facility
Facility potential (IE)
Electromechanical supplies [€]
2,000
48,724
50,000
252,136
500,000
512,847
The comparison between Tables 8 and 9 shows considerable reductions with respect to the
previous assumptions - they are significant in absolute values – since we move from about 100,000 €
for facilities of 2,000 IE to about 13,000,000 € for facilities of 500,000 IE for the overall investment
costs.
Analysis of operational/management costs
The analysis of operational costs considered the following items:
− Personnel costs;
− Cost for dosage of reactants;
− Power consumption;
− Costs for maintenance and replacement of parts;
− Financial costs.
In the global calculation, the economic return of investments was not taken into account, since
increases in return are fixed as objectives of the Institutional Bodies in charge of determining both the
water price and its variation.
136
The gain in productivity objectives were not taken into account, since they are fixed by the
Institutional Bodies in charge.
For the purposes of the global impact on water price, the two above-mentioned components
produce opposite effects: economic return produces an increase in the total cost per m3, whereas
gain in productivity produces a reduction; therefore, the global effects depend on how big or how
small such values are.
From the performed analysis, it came out that depending if adaptation works refer to type A or type
B facilities, and thus depending on the importance of adaptation interventions for reuse purposes,
substantial changes are observed for these items of costs.
In the case of additional interventions on type B facilities, the following cost items considerably
decrease:
−
−
−
The costs for the personnel, in that it necessitates a minimum amount of working hours for
chemical control; nevertheless, it is more profitable to have management performed by the
managing body of the treatment facility rather than using external entities.
The costs for power consumption, since they concern the consumption relative to UV lamps
and the operation of dosage facilities;
Financial costs, so much so to make the difference between public and no public funding not
significant; this occurs because investment costs are almost non-existent.
No significant variations are observed for the costs of reactants used in the two assumptions.
Analysis of personnel costs
The analysis of the cost of the personnel was based on two assumptions:
1.
Management of works, of reclamation facilities and the corresponding control performed by
the managing body of the treatment facilities;
2.
Management of works, of reclamation facilities and corresponding control performed by a
body other than the managing body of the treatment facilities.
This double assumption is based on the consideration that some saving could be possible in the
use of the existing personnel of the treatment facility managing body, as compared to the second
assumption.
In the first assumption, an additional activity was assumed only for the head of the facility since the
other professional profiles (chemists, facility maintenance personnel) can be suitably employed
without additional costs.
In the second assumption, i.e. entrusting this task to an external management body, it requires a
dedicated organization that inevitably leads to higher costs per facility. The comparison between the
first and the second hypothesis highlights possible saving in the use of existing personnel in favour of
the manager of the treatment facilities.
Analysis of reactant costs
The analysis of additional costs of reactants has taken into account three types of reactants
needed to adapt the existing facilities to reuse parameters:
−
−
−
Aluminium polychloride at 15% for coagulation in line;
Sodium hypochlorite at 12% of Cl2 for disinfection; or alternatively
Peracetic acid in solution at 15%, with bacterio-static function to be combined with UV rays
treatment.
Costs of power consumption
The costs of power consumption were calculated as a function of the potentials of facilities and of
reference temperatures for nitrification and denitrification (15° and 20°C), attributing a unit cost of 0.1
137
€/KWh, on the basis of the subscribed demand and the corresponding power consumption for each of
the electromechanical supplies.
Power consumption and corresponding costs were estimated for the following machinery: blowers,
mixers, return pumps, UV rays, pressure filters (filters, lifting plant for filters, lifting plant for
backwashing, blowers), gravity filters (electrical equipment, lifting plant for filters, lifting plant for
backwashing, blowers), machinery relative to additional reactants (dosage plant).
Maintenance costs and replacement of parts
Maintenance costs of building works and electromechanical supplies were estimated on the basis
of the following assumptions:
−
−
building works: a life cycle of the investment equal to about 25 years was assumed, with a
maintenance cost equal to an average yearly rate of 1% on the amount of the whole cost of
specific investment;
electromechanical supplies, in view of both increased wear and tear in operation and of the
need of replacing mechanical parts, an average life cycle of 8 years was assumed, with a
yearly maintenance rate of 5% out of the amount of the whole specific investment cost.
Table 12. Maintenance and replacement of parts
Yearly
maintenance rate
Type of works
Life cycle
Building works
25 years
1%
Electromechanical machinery
8 years
5%
Financial costs
Capital costs fall within the operational/management costs in the form of financial and depreciation
costs in relation to the type of funding of building works and electromechanical supplies. Therefore,
these costs were estimated on the basis of the following assumptions:
−
−
with public funding of the investment, in this case financial costs concerned only linear
technical depreciation with the assumption of building up the invested public capital;
without public funding of the investment, in this case the financial costs concerned, on one
hand, the share in the capital and, on the other hand, the share of interests, with the
assumption of having recourse to funding through loan.
A further and more complex hypothesis, i.e. having recourse to external funding with venture
capital, was not considered since it also requires assumptions on the type of legal structure of the
managing body and the subdivision of risk for the determination of risk rates to be included in the
financial costs.
The assumptions for the two considered hypotheses are shown in Table 13.
Table 13. Hypothesis of financial cost of investments
138
Type of works
Life cycle
Yearly rate of
interest 7% (a)
Linear depreciation
rate (b)
Building works
25 years
Financial rate
0.0858
Depreciation rate 4%
Electromechanical machinery
8 years
Financial rate
0.1674
Depreciation rate 12.5%
A significant cost incidence difference is evident between the two hypotheses:
•
•
building works – difference of 115% per year
electromechanical supplies – difference of 34% per year.
GLOBAL RESULTS OF ANALYSES
Based on the assumptions and hypotheses illustrated in the previous chapters, a general picture of
the economic analysis is outlined. The final results are presented, first for the hypothesis of type A
facilities and then for type B facilities, assuming the presence of primary treatment, temperature of
15°, dosage of reactants combined with UV. The last hypothesis is more onerous than the others.
First of all, the results of the annual costs in absolute values and in m3 for the three types of small
(2,000 IE), medium (50,000 IE) and big size (500,000 IE) are given.
The analyses were performed assuming three types of possible uses (industrial, irrigation and
supplemented irrigation) to which correspond - the facility being equal - different values of reclaimed
water volumes with respect to which the unit cost is evaluated.
Table 14. Total yearly cost for the adaptation and management of type A facilities – Primary
treatment – 15° - Without public funding – Internal Management – Hypothesis of UV
reactants – Values in €
OPERATIONAL COSTS /IE
A. Fixed costs
A.1 Operational costs
Personnel
Maintenance and replacement of parts
A.2 Financial costs (1)
Building works
Electromechanical supplies
TOTAL (A1+A2)
2,000
50,000
500,000
36,801
30,720
6,081
22,131
2,903
19,228
58,932
78,728
23,040
55,688
227,893
67,974
159,918
306,620
230,218
15,360
214,858
1,317,411
980,773
336,638
1,547,629
B. Variable costs for industry
Electrical power
Reactants
C. Variable costs for supplemented
irrigation
Electrical power
Reactants
D. Variable costs for irrigation
Electrical power
Reactants
12,771
4,926
7,845
384,095
122,606
261,490
3,817,732
549,112
3,268,620
6,845
2,640
4,205
5,568
2,148
3,420
205,875
65,717
140,158
167,466
53,456
114,009
2,046,304
294,324
1,751,980
1,664,531
239,413
1,425,118
TOTAL (A+B) INDUSTRY
TOTAL (A+C) SUPPLEMENTED IRRIGATION
TOTAL (A+D) IRRIGATION
71,703
65,777
64,500
690,716
512,495
474,086
5,365,361
3,593,933
3,212,160
C/m3 industry
C/m3 supplemented irrigation
C/m3 irrigation
0.55
0.95
1.14
0.16
0.22
0.27
0.10
0.12
0.14
139
From Table 14, in the case of type A facilities, the following is found:
−
A sharp reduction in the cost per m3 per year moving from small to large size facilities;
−
A significant difference in cost between the different types of uses. This difference decreases
both in absolute terms and as percentage, depending on the size of the potentials of
facilities. The difference is about 0.6 euros per m3 between industrial and irrigation use for
small size facilities (2,000 IE) and about 0.04 euro per m3 for large size facilities (500,000 IE)
−
Among variable costs, a significant increase in the cost of reactants.
Table 15. Incidence of costs out of the total for type A facilities - % values.
OPERATIONAL COSTS / IE
2,000
50,000
500,000
82.2
44.4
28.8
Industry
10.9
37.9
60.9
Supplemented irrigation
6.4
27.3
48.7
Irrigation
5.3
24.0
44.4
A. Fixed costs
B. Variable costs of reactants
The first effect is to be attributed to scale economy; the second one to higher consumption of
reactants related to a higher use of treated wastewater, for larger size facilities.
Secondly, minimum economic return thresholds for further interventions are possible for facilities
greater than 50,000 IE.
Quite significant results are obtained for facilities greater than 100,000 IE.
In the following graphs the additional costs for the three types of reuse assuming adaptation of
type A facilities without funding are given together with the possible saving per m3 of reuse treated
water when adaptation works are made through public funding.
Industry
Suppl. Irrig.
Irrigat.
1.30
1.20
1.10
1.00
0.90
0.80
€/m3
0.70
0.60
0.50
0.40
0.30
0.20
0.10
AE
2 000
5 000
10 000
20 000
30 000
40 000
50 000
70 000
100 000
250 000
500 000
Fig. 1. Adaptation costs for reuse and management of type A facilities – Hypothesis without public
funding.
140
Supplemented
irrigation
Industry
Irrigation
1.30
1.20
1.10
€/m3
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
2 000
5 000
10 000
20 000
30 000
40 000
50 000
70 000
100 000
IE
250 000 500 000
Fig. 2. Adaptation costs for reuse and management of type A facilities – Hypothesis with public
funding
Similarly, as for the adaptation costs of type B facilities, Table 16 illustrates the results of annual
costs in absolute values and per m3 for three types of small-size (2,000 IE), medium-size (50,000 IE)
and large-size facilities (500,000 IE).
In this respect, the following is observed:
– The sharp reduction in the cost per m3 per year from small-size to large-size facilities;
– The significant cost difference between the three types of uses; this difference decreases with size.
This effect, also in this case, is basically due to the scale economy of facilities.
141
Table 16. Total annual cost for adaptation and management of type B facilities – Hypothesis of
reactants combined with UV – Values in €
OPERATIONAL COSTS /AE
A. Fixed costs
A.1 Operational costs
Personnel
Maintenance and replacement of parts
A.2 Financial costs (1)
Building works
Electromechanical supplies
TOTAL (A1+A2)
2,000
50,000
6,276
3,840
2,436
8,156
16,449
3,840
12,609
42,208
-
-
500,000
29,512
3,840
25,672
85,851
-
8,156
14,433
42,208
58,657
85,851
115,363
B. Variable costs for industry
Electrical power
Reactants
8,745
900
7,845
276,190
14,700
261,490
3,452,520
183,900
3,268,620
C. Variable costs for supplemented irrigation
Electrical power
Reactants
4,687
482
4,205
148,037
7,879
140,158
1,850,550
98,570
1,751,980
D. Variable costs for irrigation
Electrical power
Reactants
3,812
392
3,420
120,418
6,409
114,009
1,505,298
80,180
1,425,118
23,177
19,120
18,245
334,846
206,694
179,075
3,567,883
1,965,914
1,620,662
TOTAL (A+B) INDUSTRY
TOTAL (A+B) SUPPLEMENTED IRRIGATION
TOTAL (A+B) IRRIGATION
C/m3 industry
C/m3 integrated irrigation
C/m3 irrigation
0.179
0.275
0.323
0.078
0.089
0.100
0.066
0.068
0.072
As shows the Fig. 3, economic return is already evident for the small-size facilities (20,000 IE for
the two types of irrigation service; 10,000 IE for industry).
Industry
Suppl. Irrig.
Irrig.
0.350
0.300
€/m3
0.250
0.200
0.150
0.100
0.050
-
2 000
5 000
10 000
20 000
30 000
40 000
50 000
70 000
100 000
250 000
AE
500000
Fig. 3. Adaptation costs for reuse and management of Type B facilities – Hypothesis without public
funding
142
Since the capital costs have considerably reduced, in this case the double hypothesis of public
funding/no public funding is negligible, as shown in the next figure.
Industry
€/m3
Supplem.
Irrigation
Irrig.
0.350
0.300
0.250
0.200
0.150
0.100
0.050
2 000
5 000
10 000
20 000
30 000
40 000
50 000
70 000
AE
100 000
250 000
500 000
Fig. 4. Adaptation costs for reuse and management of type B facilities – Hypothesis with public funding
COMPARATIVE ANALYSIS BETWEEN THE TWO TYPES OF INTERVENTION
Based on the results of the analyses, a comparison was made of the cost estimates of adaptation
of facilities and their management according to the effluent quality, i.e. of type A or type B.
The following came out:
− the presence of possible significant differences in additional costs for the two different effluent
qualities analysed;
− the presence of possible economic return thresholds and/or the indifference between both.
Table 17.Additional costs* for the adaptation of facilities – UV combined reactants – 15°C Costs €/m3
Type of use / IE
2,000
Industry
Supplemented irrigation
Irrigation
0.55
0.95
1.14
Industry
Supplemented irrigation
Irrigation
0.18
0.28
0.32
50,000
Type A facility
0.16
0.22
0.27
Type B facility
0.08
0.09
0.10
500,000
0.10
0.12
0.14
0.07
0.07
0.07
*hypothesis without public funding, with primary treatment
143
Firstly, the comparative analysis shows that for small-size facilities adaptation and management
costs of type A facilities are more than 3 times greater than the corresponding costs of type B
facilities; for larger size facilities, a greater value – from 30% to 50% - was achieved depending on the
type of use.
Secondly, a great difference in cost is observed between the two uses, in particular between
industrial and irrigation use. The differences in cost are equal to 0.37 €/m3 for industrial use, to 0.82
€/m3 for irrigation use for facilities of 2,000 IE; respectively of 0.03 €/ and 0.07€/m3 for larger size
facilities (500,000 IE).
Depending on the size of facilities, these differences tend to be smaller in absolute terms, but not
in relative terms.
Moreover, such differences are expectedly smaller in absolute terms when considering the
hypothesis of public funding of investments.
Therefore, scale economy of facilities, when assuming to use reclaimed wastewater, results in a
considerable reduction in additional cost differential in absolute terms but not in percentage terms.
This is quite evident from Fig. 5 In other terms, beyond 100,000 IE facilities, the difference in cost
for adaptation and management of facilities with respect to the two discharge hypotheses is
considerably reduced.
Industry
€/m3
Suppl. Irrig.
Irrig.
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
2 000
5 000
10 000
20 000
30 000
40 000
50 000
70 000
100 000
250 000
500 000
Fig. 5. Cost difference per m3 assuming no public funding for type A and type B facilities.
Secondly, the differences in cost between public funding and no public funding are significant:
−
−
−
For industrial uses for facilities up to 20,000-30,000 IE;
For supplemented irrigation uses for facilities up to 50,000-60,000 IE;
For irrigation purposes for facilities up to 60,000 IE.
Beyond such thresholds, additional cost differentials, though existing, are not significant.
In conclusion, the economic analysis highlights the following:
144
AE
In terms of investments:
a) There is a significant difference in capital cost per IE to adapt type A facilities to reuse
parameters. As observed, these costs vary from a peak of about 79€ per IE for facilities of
2,000 IE to a minimum of about 20€ per IE for facilities of 500,000 IE. Capital costs are present
in the operational/management costs function through the financial costs of the invested
capital. In this case, the capital costs accounted for about 80% of total costs for large size
facilities (500,000 IE);
b) Capital costs to adapt type B facilities to reuse parameters are not significant, since they are
almost completely negligible with respect to operational costs.
In terms of operational/management costs:
c) There are significant differences in additional cost per treated m3 for type A facilities smaller
than 50,000 IE. Such cost differentials are greater for irrigation use as compared to industrial
use.
Such differences in cost are not significant for facility threshold greater than 50,000 – 60,000 IE
and concern the three analysed uses.
Moreover, significant cost differentials are observed between investment funding through public
resource and bank loans for facilities up to about 50,000 IE; beyond this threshold no significant
absolute differences are evident.
d) Adaptation costs of type A facilities are considerably greater than the adaptation costs of type
B facilities. However, if measured in absolute terms, cost differentials of adaptation of the two
types of facilities are significantly higher for facilities around 50,000 IE. For larger size facilities,
economies of scale have significant effects, with the fundamental and crucial assumption of
effective use of treated wastewater.
MANAGEMENT ASPECTS
Finally, the management model and the procedures for water-pricing regimes were examined. The
wastewater reclamation process for reuse is one step of the Integrated Water Service.
Based on this assumption, the IWS would consist of four components: waterworks, sewage,
treatment, and additional advanced treatment for reuse. Based on such considerations, the following
situations might exist, with reference to the management model and the fixation of the corresponding
tariffs to cover capital and management costs:
The holder of the
treatment facility is the same
as for the reclamation facility
The holder of the
treatment facility is different
from the holder of the
reclamation facility
Water price fixed by the holder of the treatment facility; in this
case, the price to recover additional costs are intended to be
charged to the integrated water service, or to the community;
therefore, treatment price fixation includes the additional cost for
reclamation;
Water price to cover the additional installation and management
costs of reclamation, fixed by the holder of the latter;
Price charged to the holder of the treatment facility, or to the
community.
According to this scheme, in the first case where the holder of treatment facilities is the same as
for reclamation facilities, the additional price to cover the reclamation costs for reuse can be:
−
Charged to the integrated water service (positive increase in price);
−
Paid through increasing productivity (no effect on the cost recovery);
145
−
Charged to the State or the Regions that cover additional reclamation costs
through public contribution (no effect on the value and variations of prices).
In the second case, where the holder of the treatment facility is not the same as for reclamation
facility, the additional water price to cover reclamation costs for reuse can be:
−
−
Charged to the holder of the treatment facility (effect to be analysed on the
values and the variations of global water price, depending on the gain in
productivity objectives of the integrated water system, on the implementation of
possible scale economies of the facilities, etc.);
Charged to the State or the Regions that cover the additional costs of
reclamation through public contribution (no effect on the values and variations of
global water price).
The performed analysis highlighted that there is an economic-management return in the case of a
single holder of the IWS whose competence is also extended to wastewater reclamation.
First of all, the reclamation process has an additional impact in terms of physical investment, of
chemical treatments and type of management with respect to the on-going treatment process, so that
scale economies can be adopted especially for some fixed installation and management costs and
depending on their size.
Secondly, with a single holder of the IWS extended to the reclamation stage, the process of
covering additional costs for reclamation would be more properly solved. In fact, from the economic
viewpoint, assuming that investment costs in fixed capitals are public, a double question is raised:
1. “who pays for the additional reclamation costs” of reclaimed waters;
2. additional costs for reclamation, as shown by the economic analysis, cannot be “transferred”
downstream to the end user, as it is the case under the present regulation of some countries
including Italy, and they have thus to be covered “upstream the process”.
In the case of a single holder, the reclamation cost should be part of the methodology to define the
model for price fixation of the IWS and, subsequently, of the determination of the price cap procedure
for the price variation depending on the different objectives (productivity, quality, social sustainability,
etc.).
CONCLUSIONS
All the above can hardly lead to some conclusions since, in any case, planning of investments on
reuse cannot be solely based on technical-economic considerations. “Choosing reuse” cannot leave
aside some contingent aspects related, for instance, to irrigation suitability and environmental
condition of the territory where actions are taken; therefore, attention is drawn on some indications
that could orient planning in order to make choices and fix priorities.
− Priority should be given to the areas subject to groundwater impoverishment: supplying a
−
−
−
−
146
substitute, economically competitive resource is the first step towards reclamation.
In the cases where reuse is to the benefit of existing irrigation areas, a double benefit would be
obtained: a reduction in the cost of intervention and immediate use of the resource since the
irrigation practice will be consolidated.
Investment economies will be possible in the facilities for which reuse treatment units are
already present but where the facilities for use have not been identified yet.
Planning should also take into account the huge irrigation demand of some highly suitable
agricultural areas that, due to their geographic location and bad groundwater conditions, have
no other resource available.
Works in need of structural integrations need to be completed to be operational: in order not to
make the performed investments fruitless and to prevent rapid degradation of the implemented
works, such interventions are a priority.
− In the case of small potential facilities, combining the effluents of several facilities is desirable
to get a quantitatively significant reuse resource.
− The “non disposal” benefit for the areas highly suitable for tourism should be taken into
account.
This list of considerations is not ranked in a priority order deliberately. Planning of interventions for
reuse has to start always and in any case from a cost-benefit analysis that should also include the
environmental benefits that are not always quantifiable.
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Roma, 29 marzo.
Colombo M.G., (1997). La struttura tariffaria dei servizi di acquedotto, fognatura e depurazione,
PROAQUA Paper n. 97/09.
Commissione CE COM 477/2000 del 26.07.2000
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del Tesoro e nelle deliberazioni CIPE, in Economia e Politica Industriale, n. 118.
Hamdy A. Irrigation with Wastewater. In Atti del Corso Avanzato su “Riutilizzo delle Acque Reflue in
Agricoltura”, Bari, 8-10 Giugno, 1992;
Istituto Pugliese di Ricerche economiche e Sociali. Fabbisogni e disponibilità idriche per uso
industriale in Puglia, Bacini Idrici, Regione Puglia, Aprile, 1999;
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Pubblica, anno XXX.
Percolo M. (2003). cL’efficienza tecnica nel settore dei servizi idrici, in Economia Pubblica, anno
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147
THE ROLE OF SMALL SCALE WASTEWATER TREATMENT IN THE
DEVELOPMENT OF WATER RESOURCES IN WEST BANK OF PALESTINE
M. Y. Sbeih
Engineer in the Associate researcher ARIJ, P.O. Box 860
Beithlehem, West Bank
Email: [email protected]
[email protected]
SUMMARY -There has been substantial developments in wastewater management and treatment
technology worldwide during the past decades. Approximately 95% of the generated wastewater in
the world as well as 93% in the West Bank is released to the environment without treatment.
Wastewater has been identified as the main land based point source pollutant causing contamination
of the marine environment. The increase in population and therefore in sewage production imposes a
great challenge to develop and introduce sustainable sewage collection and treatment .The efforts in
providing these essential services especially for poor regions of the world are hindered by the
shortcomings of the current concept of water management and financial limitations. In Palestine, the
only substantial water resources available are ground water. Presently the application of wastewater
treatment is limited because of high cost and technology complexity of conventional systems.
Seepage from domestic wastewater on-site cesspits, as well as inadequately performing off-site
sewage treatment plants, demands that proper treatment should be applied at the household level to
conserve the environment. Small-scale treatment plants can be effective in treating wastewater.
Palestine is suffering from severe shortages of fresh water caused by Israel’s exploitation of
Palestinian water resources. Predicted population growth and rise in living standards could further
threaten water supplies. In light of this, wastewater is an invaluable resource that may successfully be
used for irrigation upon treatment. At present, rural Palestinian areas dispose of the wastewater using
cesspits, most of which have no cement base or liner allowing sewage to infiltrate into the earth,
potentially polluting the ground water. Owners often avoid using the expensive services of the vacuum
tankers to empty them. 12 % of Palestinian communities have wastewater collection systems while
43% of the population is connected to wastewater networks. These systems do not, however, exist in
rural areas. Only one wastewater treatment plant is operating well. The uncontrolled flow of sewage
causes many environmental problems and health hazards.
Collection of waste water and constructing large treatment plants might be difficult in Palestine due to
the great capital needed as well as the need of large areas to locate treatment plants. In addition,
constructing large treatment plants requires a large area located in the same region to be irrigated by
the treated wastewater. Small-scale reuse of treated wastewater for agriculture would play a major
role in increasing agricultural area in Palestine as well as help to conserve the environment.
PROBLEM DESCRIPTION
The rural population in the West Bank, constituting around 35% of its total population, lives in more
than 450 villages. There are 53 localities that have wastewater collection in the West Bank, while the
rest depend on cesspits and open channels. Most of Palestinian rural population depends on
agriculture to make their living and is therefore in a good position to use treated wastewater. The
wastewater collection component of this system accounts for 80 to 90% of the capital cost which
makes it economically unfeasible for the dispersed pattern of houses in rural areas. As a response to
such a situation, ‘Small- Scale Wastewater Technology’ could be the most appropriate solution to
replace current cesspit systems in rural areas of the West Bank.
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SMALL SCALE WASTEWATER TREATMENT PLANTS IN RURAL AREAS
Strategic planning and appropriate policy for wastewater management in rural areas does not exist
despite the high population in these areas and lack of adequate sanitation. Recently, in 2003 the
Palestinian Water Authority started to collect information on the type of the plants used in order to
prepare strategy for small-scale plants. About 73% of West Bank houses have cesspit sanitation and
approximately 3%, mainly in rural areas, lack any sanitation facilities. Several small-scale wastewater
treatment plants have been constructed in the unsewerd rural areas of the West Bank. In addition,
some applied research studies of biological treatment systems for small rural communities were
recently installed and studied. Most of the recently installed rural sanitation facilities entail trickling
filters and natural treatment systems preceded by septic tanks.
The need for small wastewater treatment and reuse
Centralized sewerage systems, the preferred choice of planners and decision makers, are
inadequately provided to individual communities. In some instances wastewater is transported from
several scattered communities to centralized facilities. The high cost of conventional sewers is
regarded as one of the major constraints to expanding wastewater services to small communities. A
world Bank review of sewerage investments in eight capital cities in developing countries found costs
range between us$600-4000 per capita (1980 prices) with total household annual cost of us$15650.The conventional sewerage systems are more costly in small communities, because of their size
and layout.). As example, the capital cost of construction wastewater treatment plant for ALBeireh
city, with a population of 30,000, exceeds 15million USD
Treating wastewater at the house level will be cheaper and easier than at the municipal level.
Municipal wastewater is more than twice as concentrated as wastewater generated by individual
house systems and, in addition, contains industrial wastewater, which has adverse affect on treatment
hence its reuse for irrigation. Most wastewater from centralized treatment plants cannot be reused
due to the invariability of land in that region that can accommodate that wastewater.
In addition to the pollution of residential areas, the use of cesspits enhances pollution of
groundwater. Agricultural reuse of wastewater at the household level will not require outside labor as
any member of the family can work in the field any time (e.g. a student could easily manage the work
after the school).
In terms of marketing agricultural products, the problem will be much easier since the landlord has
to market small agricultural product and he can sell them in the same village easily.
On the other hand, treating wastewater at house level or even serving one small community will
have the following advantages:
1. Easy to build, the owner of the house can build it (can be purchased as package i.e. just to install).
2. Cheaper, since the owner of the house can build it from his own resources while big treatment plant
needs huge funding.
3. No need for external technical support.
4. Job creation for the family member.
5. Operation and maintenance since the family will cover all the operation cost, as well the cost is
much less than the conventional plants which includes pumping cost, maintenance of the
wastewater treatment plant and wastewater network.
6. It will act to increase public awareness, as all family members will be involved in the process.
Different types of small plants have been installed in the West Bank, including:
1. UASB (Up flow And Anaerobic Sludge Blanket)
2. Sequencing Batch Reactors
3. Contact Stabilization
4. Septic Tank-Anaerobic Filter
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Table 1. Data Related to Existing Wastewater Treatment Plants in the West Bank
West Bank
Treatment
Plant
Ramallah
Al-Bireh
Area served
60% of
domestic
wastewater/
Industrial in
Ramallah city
Al-Bireh city, AlAm’ari Camp,
Madura CAAP/
Al-Vire
Industrial Soné
Population
currently
Served
39,950
Capacity
(CM/day)
1,276
41,347
17,765
Hebron
Tulare city,
Tulare Camp,
Nor Shams
camp, ‘Anabta,
western outlet
of Nablus
system
East of Hebron
City
115,443
0
Deir Samit
3600
1000
Disposal of
effluent
2 Aeration
lagoons
Badly
managed and
operated
(5%)
Overflow pipeline
discharged to
Wadi Beituniya
Running well
(95%)
Discharged to
open Wades
Stabilisation
pond
Not currently
functioning
(0%)
Overloaded
(15%)
Effluent carried
across Green Line
into Israel where it
flows to treatment
plant
Two
sedimentatio
n ponds
Not currently
functioning
(0%)
Two
sedimentatio
n ponds Four
reservoirs
containing
stones
Operating
well (83%)
Subsurface
constructed
wetland
Not yet in
service
6742
35
Nablus District
916
Sludge
stabilization
Three
aeration
lagoons
Three ponds
- Primary
Treatment
(sedimentatio
n and
flocculation)
5000
Hebron District
500
Sarra
Status
(efficiency)
Extended
aeration
Junín
Tulare
Treatment
type
50
Effluent from
reservoirs
discharged to
Wade Deir Samit
Effluent form
sedimentation
ponds –
3
collected in 50m
storage tank
Planned
Possible non-conventional water resources in Palestine:
Ground water is the only source for fresh water in Palestine. This water is extracted through wells
and springs. Regarding non-conventional water there are two main possible resources:
1. Saline water: This can be either from springs and seawater
2. Treated wastewater.
Utilizing saline water for irrigation is unlikely due to the high cost of desalinization .In the case of
wastewater it is easier and cheaper to reuse treated wastewater for irrigation: treated wastewater is
potentially available in every district and major city. The total treated amount of wastewater available
for reuse in Palestine (based on 2005 figures) is 109MCM compared to 137 MCM water consumed for
domestic purposes (Table 2).
At present Palestine cannot utilize all of this potential wastewater due to the following constraints:
a- The occupation: constructing wastewater treatment plants requires approval from Israel;
it is very difficult to get this approval
b- Capital needed: this is far beyond the capacity of Palestine. 93% of wastewater
generated in the West Bank is untreated - there is only one functioning West Bank treatment
plant (at Al Beirh). The cost of constructing a treatment plant for a city with a population of
40.000 will be in the range of 6-10million USD.
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c- Technical problem. Due to the shortage of land and the absence of flat land it is very
difficult to adopt waste stabilization ponds that capital and operation cost is kept to a minimum. If
a sophisticated plant is to be constructed capital outlay including operation cost will be high
which raises questions about the sustainability of plants.
Due to the factors mentioned above only 53 of 450 communities in the West Bank are served by
wastewater collection: the majority of these communities are only partially connected. As for
treatment, there is only one city that is served by an efficient treatment plant at Al Beirh. Other cities
either lack such facilities or have completely non efficient treatment plant: these are in most cases
only a series of unlined ponds. This implies it will be very difficult to implement wastewater collection
for villages or remote dwellings: small treatment plants that can serve one house or group of houses,
even a small village, will play a major role in treating wastewater and reducing environmental
pollution, as well as increasing the amount of water for agriculture.
Table 2. Annual Wastewater Generation in the West Bank and Gaza Strip Districts
District
Nablus
Ram Allah
Jericho
Jerusalem
Bethlehem
Jenin
Tubas
Tulkarm
Qalqiliya
Sal fit
Hebron
West Bank
Dear AlBalah
Gaza
Khan
Yunis
North
Gaza
Rafah
Gaza Strip
Population
(2005)
326,873
280,805
43,620
149,150
174,654
254,218
46,664
167,873
94,210
62,125
524,510
2,124,702
201,112
487,904
269,601
265,932
165,240
1,389,789
Annual Wastewater Generation / Locality Type
(MCM)
Rural
Refugee
Total
Urban
Areas
Camps
Areas
1.509808
2.153584
0.168608
3.832
0.20904
0.340704
0.074256
0.624
2.46636
2.195856
0.641784
5.304
3.61088
4.15772
0.9114
8.68
2.1852
1.4148
0
3.6
0.424128
1.079872
0
1.504
1.007136
0.73168
0.413184
2.152
3.189032
5.56444
0.598528
9.352
2.2368
3.025272
0.329928
5.592
2.498816
4.184064
0.58112
7.264
8.11504
3.657824
0.339136
12.112
3.841024
28.02747
28.1475
60.016
0.142
3.017
1.439
4.6
0.5
4.81
22.76
28.01
0.75
1.18
4.78
6.72
0.26
2.45
4.58
7.3
0.30
1.62
1.366
3.3
1.952
13.077
34.925
49.9
(Source: Arij 2006)
Role of the Palestinian Water Authority:
The PWA needs to announce policies as regards its regulation of work and should seek
understand how it can benefit from each cubic meter of treated wastewater. The PWA is in the
progress of preparing policies in this field, where cooperation between parties such as Ministry of
Agriculture and Environment Authority is necessary.
152
Technical management for safe reuse of treated waster
Wastewater is considered as an important potential water resource in Palestine. Hence, all efforts
should be put into projects associated with the reuse of wastewater for agriculture.
According to the 2002 law No.3 the PWA is responsible for wastewater treatment and reuse. The
main aim of the PWA is to set policies for solving the problems caused by wastewater and to make
use of the resultant potential sources through proper planning, design, implementation, and
management of the sector, stressing the interdependence of water supply and sanitation services.
PWA has developed policies and Strategies for wastewater treatment and reuse
Waste water treatment policy:
1. Treatment plants must be signed to solve identified and potential environmental and health
problems from existing and future wastewater production.
2. Industrial connections must not create environmental problems or cause problems with water
treatment at plants.
3. All wastewater treatment plants must operate in accordance with permits from secured.
4. Wastewater treatment plants must be designed according to PWA regulations or document that
demands will be fulfilled.
5. Treatment plants designed for less than 50 persons must be of a kind accepted by PWA and
operated according to regulations
6. The potential energy in wastewater and sludge must be utilized whenever appropriate
7. Farmers should be involved in small wastewater energy recovering projects
Wastewater reuse policy
1.
2.
3.
4.
Treated wastewater is a valuable resource that must be utilized in an optimal way
Agriculture is given priority in wastewater reuse
Reuse of treated wastewater is to be performed in an environmentally and healthy way
Use of treated wastewater should be co-ordinated on a national level and carried out at the
appropriate local level
5. Public participation in wastewater reuse should be encouraged
6. Use of raw wastewater is considered as pollution
7. Cost/beneficial options should be considered for the optimal use of the treated effluent
Waste water reuses strategy:
1.
2.
3.
4.
Establish planning tools for reuse and recharge
For every reuse project beneficiaries (farmers) must be involved in all project phases
Reuse projects must undergo an environmental impact assessment
Use of treated wastewater should be coordinated on national level and carried out on the
appropriate local level
5. Public
Wastewater reuse action plan:
1.
2.
3.
4.
5.
6.
7.
8.
make technical guidelines for reuse for different purposes
make standards for monitoring and documentation of reuse
make overall plans for reuse in different sectors
Planning Guidelines for reuse (public involvement, cost/benefit calculations, post treatment, etc)
Make a checklist for the content of the EIA-reuse element
Make an overall plan for education and training of staff and management for reuse
Arrange training programmed and campaigns
Create incentives to avoid pollution
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9. Implementation of the control and fine systems
10. The reuse plans must include how to utilize treated wastewater in wintry seasons and if the
effluent quantity drops below demand
11. Co-ordiate the reuse policy with the agriculture policy
MEASURES TO BE TAKEN IN ORDER TO MINIMIZE HEALTH RISK
Wastewater should be used for irrigation safely and economically. National regulations for the use
of treated wastewater stipulate that it is forbidden to grow crops that are to be eaten raw on treated
wastewater. In the case of small plants it is very difficult to monitor these individual projects, in this
case strict laws should be issued in order to insure safe reuse and minimize the risk of contamination.
Monitoring these projects should be coordinated between the ministry of local government and the
local council.
Public awareness programmers should be adopted in order to reduce the associated health risks.
Stakeholder participation should be insured in the planning and implementation of the projects.
For these projects to be sustainable and safe, the following guidelines should b adopted:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
It is forbidden to irrigate any crop that can be eaten raw.
Drip irrigation or subsurface irrigation should be used to prevent spray contamination
All crops to be eaten should be those which grow away from the ground (eg cabbage) Crops with
extensive ground cover should be avoided.
Priorities should be given to trees especially olive, citrus, jojoba, nut tress, flowers, producing of
seedlings etc.
Sprinkler and surface irrigation shouldn’t be used
Vaccination: all whom will work in the project should be vaccinated
Fodder crops should be encouraged.
The treatment plant should be efficient if monitored regularly.
Public awareness and training of farmers as well as educational leaflet distribution to promote
safety measures e.g. wearing boots and gloves, no smoking or eating during working with
wastewater, washing hands and face with soap and water after work, cover all exposed wounds
with a sterile dressing…..etc
Monitoring from local authorities (village council as example) should be implemented. Inspectors
from local council can inspect farms easily by just looking at fields. Monitoring the irrigated crops
should be at the field level since it is very difficult to monitor the products beyond the farm.
Fine systems to be applied and the village council have the right to destroy the entire field that
didn’t follow these regulations on the account of the farmers.
Industrial crops, table grape as well as fodder crops to be grown
Incentives should be given to the active farmers in order to encourage the others using treated
wastewater safely for irrigation and reserve fresh water for domestic use.
Farmers should contact their doctor in case of:
A-persistent stomach aches, diarrhea and bad digestion
B-symptoms of worm infection such as itching skin around the bottom or worm traces in excreta.
C-chest problem, especially if they come with asthma or lung inflammation
D- Regular checkup at least once yearly
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Table 3. Recommended guidelines by the Palestinian standards Institute (www.psi.gov.ps)
Effluent
parameter
(mg/l)
BOD5
COD
DO
TDS
TSS
PH
NO3-N
Fodder irrigation
Dry
wet
Gardens
playgrounds
Industrial
crops
Groundwater
rechargeable
Landscapes
60
200
> 0.5
1500
50
6-9
50
45
150
> 0.5
1500
40
6-9
50
40
150
> 0.5
1200
30
6-9
50
60
200
> 0.5
1500
50
6-9
50
40
150
> 1.0
1500
50
6-9
15
60
200
>0.5
50
50
6-9
50
Contamination of Water Resources
Contamination of groundwater aquifers and springs as a result of wastewater percolation is a
serious problem in several areas of the West Bank. Pollution of springs has been identified in all
district (Table4).
Table 4. some major cases of spring pollution by wastewater in the West Bank
District
Villages where contamination of springs occurred
Ram Allah
Bethlehem
Hebron
Jenin
Beittin, Al-Janiya, Silwad, Yabroud, Deir Jarir and Abu Shkheidem.Sinjel
Aortas, Wade Foqin, Nahhalin and Battir.
Beit Ummar, Halhul, Nuba, Kharas, Sa’ir, Kharsa
Nothing specific was mentioned.
Tulkarm
Jaiyus, A’zoun, and all villages who receives water from A’zoun well
Nablus
Burin, Ijnesiniya, Yatma, Jit, Abalone, Es Sawyer and Odla.Jourish
Jericho
Aluja,AlQilt
Source: ARIJ survey, 2006.
The groundwater in the West Bank is vulnerable to pollution from sewage streams and from
wastewater disposed of through cesspits. Indicators of pollution appear as nitrate concentration
increases in groundwater. Testing of groundwater samples conducted by ARIJ has shown levels of
nitrates in some areas of the West Bank to exceed the permissible level (45 mg/l). This increase in
nitrate concentration could be as a result of wastewater percolation into the ground or due to the
extensive usage of fertilizers.
Another problem associated with the percolation of wastewater into the ground is the pollution of
rainwater collection cisterns. This source of water is the main source of drinking water in many
Palestinian villages. Pollution may occur especially when cisterns are located a few meters from
cesspits and in a location below cesspit level.
One of the main concerns of the Palestinian municipalities is to limit the pollution of the
underground aquifer, the only source of drinking water. Groundwater pollution has been found in Ish
Al-Ghorab well in Beit Sahour. Accordingly, the WSSA, in order to protect the groundwater, has
ratified a law to connect homes with the new sewage network instead of using cesspits. They have
also suggested the introduction of septic tanks to replace cesspits in areas where there is no plan to
extend the sewage network.
The locally small scale wastewater treatment technology can be successfully used at the
household level for wastewater disposal and treatment. The implementation of such units have many
positive impacts on the natural environment by 1) improving the management of wastewater
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treatment and reuse at the household level, 2) protection of surface and groundwater from potential
contamination, 3) increase the agricultural area by utilizing the reused water in irrigation of gardens,
4) limit health hazards as a result of illegal discharges of raw sewage.
Table 5. Water Consumed and wastewater generation in the West Bank Districts Only from the
localities that have water network (2003)
Governorate
Nablus
Ram Allah
Jericho
Jerusalem
Bethlehem
Jenin
Tubas
Tulkarem
Qalqilia
Salfit
Hebron
West Bank Total
Water
Consumed
8683827.4
8949008
2305506.8
6209705
5213582
3557146
657914
5051148
288252
1480331.6
8384567
50280988
Wastewater
Generated
4385597
4213317
1131864
2863506
2504936
1764525
325759
2507316
1386579
715790
4108955
25908144
No. of Communities Served By
Sewage network
10
8
1
7
8
3
1
5
3
1
6
53
Source: (PWA 2003, Arij 2006)
Only 7% of the wastewater in the West Bank is treated, despite the fact that approximately 36.39%
of the West Bank population is served by sewage networks (PCBS 2002, Arij 2006). This implies that
93% of the generated wastewater in the West Bank is disposed to the natural environment without
treatment. When this wastewater is disposed of without treatment, the ground water and aquifers are
polluted. Clear examples of that are: Irtas spring in The Bethlehem district, Sinjel spring in Ramallah
district, as well as Alzbeidat ground water well in Jericho district. In addition, flowing raw wastewater
is considered a potential source of water born disease. At Al-Aroub refugee camp wastewater is
flowing in open channels crossing through Shuyokh Alaroub dawn to the wadi.
Health Pressure
Since most wastewater is either collected in cesspits problems arise in the wet season when these
as well as open channels overflow into the streets. Due to these problems it is worried that conditions
at, for example, Al-'Aroub refugee camp and Shyokh Al-'Aroub village, are a source of spreading
diseases and insects.
With respect to public health, there are frequent outbreaks of diarrhoea in the West Bank. Data
indicates that 600 of 2,721 water samples failed to meet WHO bacteriological guidelines for drinking
water (Ministry of Health, 2001). Only three of all the samples tested showed no signs of coliform
bacteria, and 50 % should not be used for household purposes without treatment.
In January 2003, in North Gaza alone, 182 new cases of airborne diseases and 231 of diarrhoea in
children under 3 years age were reported–little additional data on diseases exists for Gaza.
Nitrate concentrations have been shown to exceed WHO guidelines in 50 % of samples collected
from domestic municipal wells (Rishmawi,2004) – causing “blue baby syndrome”. Parasites and
helminthes transmitted by mosquitoes as well as skin infections and allergies are also common.
The 2002 study by Arabtech Jardanah (consulting firm located in Ramallah) indicated that
UNRWA clinic in the Al-'Alaroub refugee camp treats about 10 cases per day related to untreated
sewage, with diarrhoea representing 5% of the daily cases treated by the clinic. One of the other
major diseases in the study area was Leishmanias; this as a result of insects able to multiply rapidly in
156
stagnant sewage. At Shyoukh Al-'Arroub and Irqantrad those seeking medical assistance often used
different private or public sector health centers increasing the difficulty of effective data collection,
hence a complete record of the types of diseases is not available.
Another example is Alzbeidat village in the Jordan valley (Jericho District), where the people used
to depend on a polluted well for their domestic needs. The well was polluted as a result of
wastewater seepage from cesspits, the water of which has been the cause of skin rashes among the
residents until they stopped using it for drinking purposes. Water is now imported from a nearby
settlement which implies additional cost for the villagers.
It is also important to mention that the Betir Village, (Bethlehem District) also faces the danger of
diseases associated with untreated sewage. The rocky nature of the village’s land rendered the
population living at the bottom of the village exposed to sewage contaminated rock surfaces as a
direct consequence of sewage seeping from cesspits located at a higher level.
Flooding of Wastewater into the Ground Surface
Frequent flooding of wastewater from cesspits and open channels, especially during the winter
season, is a major environmental and health threat. The accumulation of wastewater in open areas
potentially leads to the transmission of infectious disease and the release of foul odor. This scenario
is repeated in most Palestinian villages and refugee camps in the West Bank. Flooding of cesspits
and open channels is common too, and in some cases one locality may affect another locality as is
the case of Al-Jalazone refugee camp and Jifna village in the Ramallah district where Jifna village has
been suffering from wastewater overflow from Al-Calzone refugee camp, creating wastewater ponds,
and damaging crops and agricultural lands. Due to lack of proper infrastructure, incomplete
regulations, standards, and enforcement all types of wastes are released untreated into the
environment.
As is important to mention, flooding of wastewater from cesspits and open channels is not the only
source of pollution to the ground surface. The irresponsible behavior of some citizens, disposing of
their sewage by installing a submersible pump in their septic tanks and disposing its effluent freely to
the surroundings is another source of pollution to the ground surface.
Fig. 1. Betir infected rocky surfaces due to sewage that seeps from cesspits located at higher levels
(Source: Arij, 2005)
157
Ground Water Pressure
Ground water in wells, springs and volumes of retained water in aquifers, has represented the
main source if not the only source of drinking water in the West Bank. The followings are some
examples of the ground water pollution due to disposing of wastewater untreated to the natural
environment:
• Sinjel spring in Ramallah district where the spring is completely polluted with wastewater seeping
from the cesspits of the village.
• Irtas Spring in Bethlehem district. Where the spring has been polluted by sewage seeping from
nearby cesspits.
• Alba than (Nablus district) springs and wells; these springs and wells are polluted from Nablus
sewage that flows to the east of the town toward Alba than and wadi Alfaro.
• Ein Al-Qalt and Aluja spring in the Jordan Valley (Jericho District); these springs have been
polluted from sewage that seeps from the neighboring mountainous areas.
• Ein Areek Eltahta spring in Ramallah district is another example.
Treated Waste Water to be used as Supplementary Irrigation to Enhance Sustainability of
Agriculture
Treated wastewater can be used for irrigation in west –bank by the followings methods:
1. Reusing of the treated wastewater for irrigation as the only source of irrigation water. This can be
in small-scale village scale or region (waster water is collected from several communities) and
reused for irrigation
2. Supplementary Irrigation: here in this case treated wastewater can be applied as supplementary
irrigation where plants are already planted in the area.
3. Treated wastewater can be reused in small scale systems at the household level (home garden)
especially in villages, towns and remote houses. Treated wastewater can be used alone as the
only water source, or rainwater can be collected and used either separately or mixed with treated
wastewater.
4. Gray wastewater can be treated and recycled for use in toilet flush in order to conserve using fresh
water for this purpose
Table 6. Al Bireh Pilot Plant (Using Treated Waste Water for Irrigation)
Kind of
Treatment
Irrigation
with
Fertilizer
Irrigation
without fertilizer
Rain fed
with
Fertilizer
Rain fed
without
Fertilizer
Irrigation
with
Fertilizer
Irrigation
without
Fertilizer
Rain fed
with
Fertilizer
Rain fed
without
Fertilizer
Source: ANERA files
158
Crop Type
Wheat 870
Production kg / dunum
Seeds
Straw
687
1375
656
1332
Wheat 870
537
1187
Wheat 870
500
1031
Wheat Amber
864
1656
Wheat Amber
824
1212
Wheat Amber
600
1000
Wheat Amber
236
336
Home gardens and reusing treated wastewater for irrigation as a mean of enhancing sustainable
agriculture.
Nowadays there is a move toward small-scale wastewater treatment systems, where small
treatment plants conserve one or a group of houses. This plant can treat either black wastewater or
gray wastewater. In the case of gray wastewater, the treatment needed is much less than black
wastewater and different crops can be irrigated easily and safe. Treating the gray water will be
cheaper and securing effluents that meet safe standards will be easier.
In Palestine, especially the rural areas, the wastewater from each house or group of houses can
be treated, and can be stored and reused in the garden in order to provide food for the people as well
as create jobs.
Another additional benefit of treating wastewater and its reuse is the reduction in cost with loss of
the need to empty them. A reduction in cesspit/septic tank seepage pollution is another benefit. In
addition more fresh water will be available for domestic purposes.
In this case, the combination of rainwater harvesting from the roof of the house with the treated
wastewater and use it for irrigation will play a major role in providing the following:
1. Provide rainwater for irrigation i.e., water free from salts and organic matter.
2. Reduction of wastewater impact on the crop, soil and human being i.e., leaching the salts.
3. Expand the potential for crop selection where in this case most of the crops can be irrigated.
Another advantage of home garden (small scale treatment plant) that planting can be practiced in
the entire West Bank region (Jordan valley, mountains), as well during the entire year (summer and
winter).
Table 7. Average production of agricultural crops from the year 1988-1994 according to the statistics
of ministry of irrigation
Production
Planted area
Production
Consumption
Crop
1000 dunam
ton/year
ton/year
%
Wheat
170
23,800
300 000
7,9
Barley
140
21000
108 000
19,9
Pease
29
2320
11885
19,5
Alfalfa animal feed
26
15600
1110 000
14
Strategic Options According to the Palestinian Environmental Strategy
Wastewater management has been identified as the most urgent element in the Palestinian
Environmental Strategy (PES). The strategy calls for establishing an effective wastewater
management system that considers the following measures: (Ministry of Environmental Affairs, 2000)
•
•
•
•
•
•
•
•
Rehabilitation of existing wastewater treatment plants and/or construction of new plants based
on maximization of capacities in order to minimize the number of plants required
Maximizing coverage of households’ connections to the sewer system;
Considering alternative collection and disposal measures for areas where the construction of
sewage networks is unfeasible
Developing regulations for treatment or disposal of sludge that is generated by wastewater
treatment plants
Enabling an acceptable quality range of influent wastewater, so that treatment plants will be
able to treat wastewater effectively
Industries have to undertake on-site pre-treatment measures to comply with the treatment
plants specifications
Developing guidelines and specifications for the wastewater treatment technologies and
locations
Establishing a cost recovery system.
159
ARIJ EXPERIENCE IN SMALL SCALE PLANTS
ARIJ has engaged in implementing 3 units of small scale plants to test their efficiency and
performance. It was found that their performance was acceptable as seen below. Furthermore the
operation cost is also acceptable
Quality of the treated effluent
Selected parameters were analyzed to study the efficiency of the small scale wastewater treatment
system, and whether if this effluent is suitable for irrigation purposes. These parameters are the
Biological Oxygen Demand (BOD5), the Chemical Oxygen Demand (COD), the Total Suspended
Solids (TSS), the Ammonium Nitrogen (N-NH4), and the Total Phosphorus (TP). These analyses were
carried out in the Biological and Chemical Analysis Center of Al-Quds University. The quality
parameters of the effluent are given in Table 8.
Table 8. Effluent quality of locally small scale wastewater treatment system
Effluent parameters
BOD5
COD
TS
TSS
PH
N-NH4
TP
Concentration (mg/l)
Sample1
Sample2
15
15
27
17
653
651
173
171
7.1
7.1
4.6
4.1
5.08
5.23
According to the Palestinian Standards Institution for treated wastewater characteristics (shown in
Table 3), the results of effluent parameters show the quality of treated wastewater from a small-scale
wastewater treatment unit to be acceptable for garden irrigation purposes with no hazardous impact.
However, the TSS concentrations are generally high according by Palestinian standards.
Furthermore, by WHO standards, the effluent quality is acceptable for irrigation purposes, except for
the TSS which is high, particularly when drip irrigation is used.
RESULTS of ARIJ SMALL SCALE PLANTS
The results of the small-scale plant installed by ARIJ are encouraging where effluent BOD5 didn’t
exceed 23mg/l during the first year of operation. At $0.3usdollar/cubic meter operation costs are
reasonable and should be accepted by house owners.
CONCLUSION AND RECOMANDATION
1. Current available water is not enough to meet the demand for both domestic and agricultural
purposes.
2. Wastewater collection by networks from individual houses and treatment is highly needed in
covered by wastewater collection. So small treatment plants can play a major role in covering
this gap and preserve the environment
3. Proper planning of wastewater collection and treatment should be done to achieve sustainable
wastewater treatment plants.
4. Planning for centralized treatment plants should take into consideration the topography of the
area in order to avoid unnecessary pumping. All of the West Bank should be treated as one
unit without separation between the districts.
160
5. It seems that implementing waste water collection and treatment for all of the communities is
very difficult, furthermore covering the rural areas seems to be impossible due to the huge
capital needed as well as due to the permits needed from Israel.
6. Collecting wastewater and treating it at the household level or even at that of the small
community will be efficient for its reuse in irrigation
7. Reusing the treated wastewater in the home garden will be economical and highly feasible as
a source of water for irrigation. Even on the village scale, waste water can be collected, treated
and reused for irrigation
8. Reusing of treated wastewater on a large scale can also be used for irrigation if treatment can
be secured.
9. The Palestinian Water Authority as well as ministry of agriculture should plan for using treated
wastewater for agricultural purposes at all levels. All of the parties should cooperate in order to
make wastewater treatment a success, since any deviation is likely to result in further
environmental and heath problems.
10. Palestinian authorities should implant public awareness programs for residents as well as for
the local authorities
11. The Palestinian Water Authority should prepare plans to utilize all of the treated waste water
for irrigation either on a small or large scale according to the prevailing conditions, e.g. taking
into consideration the economic issue, and the suitabliity of the land to be irrigated with treated
water.
12. Reusing treated wastewater at the household level will be cheaper since there will be no need
for collection and pumping. As well as this treated wastewater will be reused for irrigation at
house level
REFERENCES
Al Beireh Municipality, (1993), Al Beireh, Palestine, Waste Water Treatment Plant Feasibility Study.
American near East Refugee Aid, ANERA, Files, Jerusalem, Palestine.
Haddad.M.2004 Integrated water and waste management in rural areas in Palestine submitted to
international demand water management conference held on the Dead Sea Amman –Jordan. May
30-June 4 2004
F.A.O. (1992) Wastewater Treatment and use in Agriculture, Publication no. 47, Rome – Italy
FAO.2002.The Uses of Treated Waste Water in the Forest Plantations in the Near East Region
Palestinian Ministry of Agriculture Statistics, 1997. Ramallah – Palestine.
Palestinian Water Authority. Palestinian water Law, Ramallah, Palestine.
Shuval H., Lambert Y. and Fatal B. (1997). Development of a Risk Assessment Approach for
Evaluating Wastewater Reuse Strategy for Agriculture, Water Science Technology Vol. 35, No. 1
Salfeet Municipalities, (1995), Palestine Waste Water Treatment Plant Feasibility Study.
Sbeih M. Reuse of Treated Waste Water, Pilot Plants in Al Beireh, 1995, Palestine.
W.H.O. (1989) Health Guidelines for the use of wastewater on Agriculture and Aquaculture Technical
Report No. 778. W.H.O. Geneva. W.H.O. Geneva.
Applied Research Institute, Status of the environment 2006.Beithlehem, Palestine
GTZ. (2005). Guidelines of reusing treated waste water in the Jordan Valley. Amman. Jordan
W.H.O. (2006) Health Guidelines for the use of wastewater on Agriculture and Aquaculture .W.H.O.
Geneva
ANERA (2005). American Near East Refugee AID .Jerusalem. Palestine
161
IRRIGATION OF VEGETABLES AND FLOWERS WITH TREATED
WASTEWATER
*
**
**
I. Papadopoulos , D. Chimonidou , P. Polycarpou and S. Savvides
Agricultural Research Institute, 1516 Nicosia, Cyprus
*
Director of Agricultural Research Institute, [email protected]
**
Agricultural Research Officers A´, [email protected] /
[email protected]
***
Agricultural Research Officer, [email protected]
***
SUMMARY - Application of recycled water to agricultural land for irrigation could be an alternative
water resource for Mediterranean countries facing severe water shortage. Rational use of the
nutrients in recycled water could increase crop production and reduce environmental pollution. At the
Agricultural Research Institute different studies were conducted to investigate the effect of treated
wastewater and N applied on the yield of three field crops and three cut flowers.
The first study, included three field experiments with green pepper, eggplants and sudax, irrigated
with borehole water or with secondary treated municipal wastewater. Both waters were supplemented
3
3
3
with N applied continuously with the irrigation water at four levels 0 g/m , 50 g/m , 100 g/m and 150
3
g/m . Yield results indicate the superiority of the treated wastewater and its ability to produce high
yields with less N fertilizers.
The second study included the irrigation with treated wastewater of a) Gerbera jasmesonii and b) for
hydroponic culture of Limonium perezii and Antirrhinum. Gerbera jasmesonii was irrigated with
secondary treated wastewater, borehole water and fresh water with or without additional fertilization.
Results on flower production per plant shown that freshwater produced significantly more flowers per
plant than the other water qualities and fertilization had a significant effect on flower production for
freshwater irrigated plants but no significant effect on wastewater irrigated plants. Results on
Limonium perezii and Antirrhinum in hydroponics, show that both plants irrigated with secondary
treated wastewater and treated wastewater from the epuvalisation system were less vigorous and
produced significantly less flowers of lower quality than flowers produced from plants irrigated with
freshwater with the addition of fertilizer. Results on the effects of fertilizer and water quality on flower
weight of gerbera plants indicate that high salt concentration in wastewater can be a limiting factor for
the production of sensitive plants such as Gerbera jasmesonii. Mixing of wastewater with freshwater
could give good results by lowering the salt concentration of the water and also providing some
nutrients to the plants.
Key words: Wastewater, irrigation, water reuse, green pepper, eggplants, sudax, nitrogen, Gerbera
jasmesonii, Limonium perezii, Antirrhinum.
INTRODUCTION
In Cyprus and in most Mediterranean countries, the scarcity of water together with the high cost
associated with collecting and using the limited surface rainwater for irrigation, have become real
constrains for our irrigated agriculture. Because of this, particular emphasis is placed on the water
use efficiency and the cultivation of crops with high return per square meter and volume of water i.e.
flowers and vegetables (Chimonidou, 2002 and 2003).
The irrigated agriculture in semi arid countries like Cyprus demands large amounts of water and
faces the serious challenge to increase or at least sustain agricultural production while coping with
less and/or lower quality water. Over the years, the severe shortage of water, primarily in the arid and
semi-arid regions, has promoted the search for extra sources currently not intensively exploited.
Treated wastewater is now being considered and used in many countries throughout the world, as a
new additional, renewable and reliable source of water, which can be used for agricultural production.
By releasing freshwater sources of potable water supply and other priority uses, treated wastewater
reuse makes a contribution to water conservation and expansion of irrigated agriculture, taking on an
163
economic dimension. It also solves disposal problems aimed at protecting the environment and
public health and prevents surface water pollution by the direct discharge of pollutants into inland and
coastal waters (Papadopoulos and Savvides, 2002, Papadopoulos et.al. 2005).
The benefits, potential health risks and environmental impacts resulting from wastewater use for
irrigation and the management measures aimed at using wastewater within acceptable levels of risk
to the public health and the environment are well documented (WHO, 1973 and 1989, Hespanhol,
1990; Hespanhol and Prost, 1994; FAO, 1992, Jenkins et al., 1994, Asano and Levine,1995,
Angelakis et al.,1997). Properly planned use of wastewater can reduce environmental and health
related hazards, which have been observed with traditional wastewater disposal.
Statistical analysis of rainfall in Cyprus reveals a decreasing trend of rainfall amounts in the last
3
decades. The wastewater generated by the main cities, about 25Mm /year, is collected and used for
3
irrigation after tertiary treatment. About 10 Mm /year is conservatively estimated to be available for
agricultural irrigation in the near future allowing irrigated agriculture to be expanded by 8-10% while
conserving an equivalent amount of water for other sectors (Papadopoulos 1995).
In addition to water benefit to the irrigated land, treated municipal wastewater can provide
significant amounts of plant nutrients, especially nitrogen and phosphorous, which can improve the
fertility of soils, benefit plant growth, improve crop production and reduce the total requirements of
commercial fertilizers needed to be applied, increasing the total economic return to the farmers.
However with the treated effluent as an irrigation source, the additional fertilizer N may create
conditions of NO3 percolation and pollute groundwater (Papadopoulos and Stylianou, 1987, 1988a,b).
The aim of the first study is to present yield results obtained from sudax, eggplant and sweet
pepper, irrigated with wastewater and freshwater with the addition of N fertilizer and of the second
study, is the effect of water quality and fertilization on flower production of Gerbera jasmesonii (in
soil) and Limonium perezii and Antirrhinum (in Hydroponic culture).
MATERIALS AND METHODS
Experiments of Sudax, Eggplant and Sweet pepper
Three separate experiments were carried out from 1998-2001, on sudax (hybrid “Trudan”),
eggplants (Solanum melongena) of the variety “Bonica“, and sweet pepper (Capsicum annuum) of
the variety “Gedeon“.
The treatments included two sources of irrigation water, (borehole and secondary treated
wastewater) with four levels of nitrogen, 0, 50, 100 and 150ppm. The field experimental layout for all
three experimental plots was a split plot design with four replications with the two sources of water
assigned to the main plots and N levels to the subplots.
In the sudax experiment each plot consisted of 3 rows 30 m long, spaced 60cm apart and irrigated
with 10L drippers spaced 30cm apart on the irrigation line. In the sweet pepper experiment, each plot
consisted of three rows 1m apart with 42 plants in each row, having each plant planted 60 cm apart
whereas in the eggplant experiment the rows were 80cm apart. Plants of eggplant and sweet pepper
were watered by drip irrigation using 10L drippers and in all experiments the amount of water applied
was based on Epan evaporation.
The field studies were conducted on a calcaric cambisol soil with 20% CaCO3. The secondary
treated wastewater used in this experiment is a product of an activated sludge treatment plant from a
residential community with no industrial inputs. The quality of the treated wastewater was monitored
every week during the investigation period. The analysis included electrical conductivity (ECw), pH,
Ca, Mg, Na, K, HCO3, Cl, SO4, NO3-N and B. Nitrate-N was determined by using a specific NO3-N
electrode (Kent, EIL model 8006.2). All other analyses were performed according to standard
procedures. The average chemical composition of the treated wastewater and borehole freshwater
during the irrigation season is given in Table 1. The mean biological oxygen demand (BOD5), the
chemical oxygen demand (COD) and the suspended solids (SS) of the treated wastewater were
during the irrigation season 76, 45 and 38 mg/lt respectively.
164
Table 1. Chemical composition (ppm) of freshwater and wastewater used for irrigation.
ECw
pH
Ca
Mg
Na
K
HCO3
SO4
NO3
Borehole
2.9 mmhos/cm
7.5
36
71
570
9
415
387
Wastewater
3.0 mmhos/cm
7.3
60
52
540
31
482
375
Cl
B
75
629
1.2
10
560
0.8
Experiment of Gerbera jasmesonii on soil
The experiment on the cultivation of Gerbera jasmesonii was carried out in 2001-2002 using
Gerbera of the red variety “testarosa” as the experimental plant, in order to evaluate the effect of four
different sources of water with (treatments F1-F5) and without fertilization (treatments W1-W5) on
flower production and quality. The sources of water were: a) Secondary treated wastewater, b)
Treated wastewater from the epuvalisation system c) Borehole water and d) Fresh water. Analysis of
the sources is given in Table 2.
Fertilization (treatments F1-F5) consisted of 150ppm N (Ammonium Nitrate), 40ppm P (Urea
Phosphate) and 180ppm K (Potassium Nitrate). Once a month 5gr/plant of Fe chelate was applied to
all treatments as Gerbera plants are sensitive to iron deficiencies.
The plants were grown under 70% shading on ridges 30 cm wide and 40 cm high. The
experimental plots were irrigated by drip irrigation using 10L drippers. Water was pumped from the
storage tanks near the epuvalisation system with ½ hp electric pumps generated by an electric
generator.
The experimental design was factorial with six replications. Each replication consisted of 10
randomized plots, each plot being a 6m long row (ridge) with 13 plants 50cm apart. The distance
between rows was 120 cm with a central 120 cm wide corridor separating the three replications.
Table 2. Chemical analysis of the four sources of water used in the experiment.
FRESH
WATER
pH
Conductivity
Boron
Calcium
Magnesium
Sodium
Potassium
Bicarbonate
Sulphate
Chloride
Nitrate
SS
COD
BOD5
7.38
0.92
mmhos/cm
0.37 ppm
50 ppm
52 ppm
103 ppm
2.6 ppm
275 ppm
160 ppm
124 ppm
10 ppm
BOREHOLE
WATER
7.53
3.03
mmhos/cm
1.15 ppm
36 ppm
71 ppm
570 ppm
9 ppm
415 ppm
387 ppm
629 ppm
10 ppm
EPUVALISATION
SYSTEM (CHANNEL A)
8.0
2.8
mmhos/cm
0.8 ppm
60 ppm
52 ppm
540 ppm
31 ppm
482 ppm
375 ppm
560 ppm
90 ppm
27 mg/lt
45 mg/lt
80 mg/lt
SECODARY
TREATED
WASTEWATER
8,2
2,6
mmhos/cm
0.8 ppm
60 ppm
52 ppm
540 ppm
31 ppm
482 ppm
375 ppm
560 ppm
100 ppm
31 mg/lt
45 mg/lt
85 mg/lt
Greenhouse experiment with flower plants using hydroponics
Two flower plants Limonium perezii and Antirrhinum were planted in a new hydroponic system
made from Polygal´s plant beds. The plant beds are manufactured from double walled polypropylene
sheets and have a drainage system at the base of the channel, which provide better drainage and
165
aeration. Perlite was used as a substrate in the plant beds and plants were irrigated using 4L
drippers. The experimental design was factorial with six replications and each replication consisted of
four plant beds 2.4m long placed 60cm apart in two rows. In each plant bed six plants from each
variety were planted.
Both plants were irrigated with: a) untreated secondary treated wastewater, b) treated wastewater
from the epualization system c) fresh water with additional fertilizer of 60 ppm N and d) fresh water
with additional fertilizer of 120 ppm N.
The aim of the experiment was to investigate whether untreated and treated wastewater could be
used in hydroponics for flower production without the addition of extra nutrients.
RESULTS AND DISCUSSION
From the results of yield of eggplant and sweet pepper (Figs 1 and 2) it is demonstrated that
wastewater gave better yield and fruit number than freshwater at all nitrogen concentrations and
without N application. Without application of N in water, yield increased by 99% in the case of sudax,
65% and 82% in the case of eggplant and sweet pepper irrigated with wastewater compared with
treatments irrigated with borehole water. In all cases, application of N in wastewater had no
significant effect on yield, and fruit number at all concentrations.
a)
600
380
575
360
550
340
525
320
300
500
475
Yield (t/ha)
Yield (t/ha)
b)
450
425
400
280
260
240
220
200
375
180
350
160
WASTEWATER
325
WASTEW ATER
140
FRESHW ATER
300
FRESHWATER
120
0
50
100
150
0
50
YIELD (t/ha)
N applied (ppm)
800
780
760
740
720
700
680
660
640
620
600
580
560
540
520
500
480
460
440
420
400
380
360
340
320
300
100
150
N applie d (ppm)
c)
W ASTEWATER
FRESHWATER
0
50
100
150
N applie d (ppm)
Fig. 1. Average yield of a) eggplant, b) sweet pepper and c) sudax as influenced by N applied and
water quality.
166
a)
32 00
31 00
30 00
Fruit number ('000 fruits/ha)
29 00
28 00
27 00
26 00
25 00
24 00
23 00
22 00
21 00
W A S TE W A T ER
20 00
FR ES H W A TE R
19 00
18 00
17 00
16 00
0
50
10 0
1 50
N ap p lie d (p p m )
6 600
b)
6 400
6 200
Fruit number ('000 fruits/ha)
6 000
5 800
5 600
5 400
5 200
5 000
4 800
4 600
4 400
4 200
4 000
W A S T EW A T E R
3 800
F R ES H W A T ER
3 600
3 400
3 200
3 000
0
50
100
15 0
N a p p lie d (p p m )
Fig. 2. Average fruit number of a) eggplant and b) sweet pepper as affected by N applied and water
quality.
The increase of average yield of sweet pepper from the wastewater-irrigated plots was by 63 %
higher compared to the borehole water, 29% for eggplant and by 30% in the case of sudax.
In the case of irrigation with borehole water there was no significant difference in yield at N
applications above 50ppm in the case of sudax and above 100ppm in the case of sweet pepper.
With all crops, higher yield was obtained with the treated wastewater than with the borehole water
indicating the superiority of the treated wastewater and the possibility of producing high yields without
additional N fertilizers (Papadopoulos and Stylianou, 1987,1988a, 1988b, 1991). It is therefore,
imperative that recommendations to the farmers concerning fertilisation should be different for the
effluent and fresh water, in order to improve the efficient use of water and of nutrients present in
wastewater. This will also minimise the risk of pollution, especially in cases where water table is
shallow and pollution by nitrate-N could easily happen (Papadopoulos and Stylianou, 1987, 1988a,b).
Properly planned use of wastewater can be of economic importance to crop production as it could
substitute for fertilizer application and, therefore, reduce cost of production, which can be an
important factor to the agricultural economy of developing countries where fertilizer cost is a major
constrain to improve production.
On the contrary, results of the productivity of Gerbera jasmesonii (flower production per plant)
showed that freshwater produced significantly more flowers per plant than the other water qualities.
167
During the course of the experiment mentha in the epuvalisation system was not fully established
from the beginning of the experiment and as it is shown in Table2, of the average water analysis of
the four sources of water used in the experiment, there was no significant differences between the
secondary treated wastewater and the treated wastewater from the epuvalisation channel A.
Therefore there was no significant difference in the flower production and quality between the two
treatments (Figs 3 and 4).
Fertilization had a significant effect on flower production in the case of freshwater irrigated plants,
but no significant effect on wastewater irrigated plants. Plants irrigated with borehole water had a
reduction on flower production especially with the addition of fertilizer, when compared with plants
irrigated with wastewater. Reduced flower production and quality could be due to the high electrical
conductivity and chloride concentration of the borehole water and wastewater as Gerbera plants are
sensitive to high salt concentrations (Table2).
Results on the effects of fertilizer and water quality on flower weight of gerbera plants indicate that
high salt concentration in wastewater can be a limiting factor for the production of sensitive plants
such as Gerbera jasmesonii probably due to the slower uptake of water and fertilizer by the plant.
Mixing of wastewater with freshwater could give good results by lowering the salt concentration of the
water and also providing some nutrients to the plants.
8
FlowerNumber / plant
7
WITH FERTILISER
WITHOUT FERTILISER
6
5
4
3
2
1
BOREHOLE WATER
FRESH WATER
WASTEWATER
EPUVAL. WATER
Water Treatments
18
17
Fig. 3. Effect of water
quality and fertilizer on
flower production of
Gerbera plants
WITH FERTILISER
WITHOUT FERTILISER
Flower Weight / gr.
16
15
14
13
12
11
10
9
Fig. 4. Effect of water
quality and fertilizer on
stem weight of Gerbera
plants
168
8
BOREHOLE WATER FRESH WATER
WASTEWATER
Water Treatments
EPUVAL. WATER
Results of the effect of fertilizer and water quality on flower production of Limonium perezii and
Antirrhinum plants showed that both plants irrigated with secondary treated wastewater and treated
wastewater from the epuvalisation system were less vigorous and produced significantly less flowers
of lower quality than flowers produced from plants irrigated with freshwater with the addition of
fertilizer (Figs 5 and 6).
Limonium perezii produced significantly higher number of flowers when irrigated with fresh water
with the addition of 120 ppm N than when irrigated with fresh water with the addition of 60ppm N,
wastewater or treated wastewater from the epuvalisation channel. Antirrhinum on the other hand,
produced significantly more flowers when irrigated with fresh water with the addition of 120 or 60 ppm
N, than when irrigated with wastewater or treated wastewater from the epuvalisation system (Fig. 5).
The quality of the produced flowers in both plants (most pronounced effect on Antirrhinum)
followed the same trend with significantly higher stem weight (fresh weight) in the cases of fresh
water with the lower level of fertilization 60ppm N (Fig. 6).
Plants irrigated with wastewater and treated wastewater from the epuvalisation system showed
nitrogen deficiency symptoms indicating that the low flower production was most probably due to the
low nitrogen levels in the wastewater during that period (35ppm N in wastewater and 23 ppm N in
wastewater treated in the epuvalisation system). Addition of N fertiliser in treated wastewater might
be essential when used for irrigation depending on the plant used and level of treatment of effluent.
6
Limonium perezzi
5.5
Number of Flowers / Plant
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
FRESH 120ppm N
FRESH 60ppm N
WASTEWATER
EPUVALISATION
Flower Weight / gr.
Water Treatments
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Antirrhinum
FRESH 120ppm N
FRESH 60ppm N
WASTEWATER
EPUVALISATION
Water Treatments
Fig. 5. Effect of water quality and fertilizer in flower production and stem weight of Limonium perezii
and Antirrhinum plants.
169
Flower Weight / gr.
70
68
66
64
62
60
58
56
54
52
50
48
46
44
42
40
38
36
34
32
30
28
26
24
22
20
Antirrhinum
F R E S H 1 20p pm N
F R E SH 60ppm N
W ASTE W AT ER
E P U V A L I S A T IO N
W a t e r T r e a t m e n ts
3
2 .8
Number of Flowers / Plant
2 .6
2 .4
2 .2
2 .0
1 .8
1 .6
1 .4
1 .2
1 .0
0 .8
0 .6
0 .4
0 .2
0
F R E SH 120p pm N
F R E SH 60p pm
N
W A S T EW A T E R
E P U V A L ISA TIO N
W ater T reatm ents
Fig. 6. Effect of water quality and fertilizer in flower production and stem weight of Limonium perezii
and Antirrhinum plants.
CONCLUSION
The yield results of eggplant, sweet pepper and sudax, indicate the superiority of the treated
wastewater and the possibility of producing high yields without additional N fertilizers. In this case
yield might not be the highest but with no additional N, pollution problems are minimized. The plant
nutrients load in the wastewater can be an important factor in saving costs of fertilizers needed for
crop production. It is therefore advisable that recommendations to the farmers concerning fertilization
be different for the effluent and freshwater. On the contrary, Gerbera plants irrigated with wastewater
and borehole water, produced less flowers compared to the freshwater irrigated plants probably due
to the high electrical conductivity and chloride concentration of both waters, as Gerbera plants are
sensitive to high salt concentrations.
Plants of Limonium perezii and Antirrhinum irrigated with secondary treated wastewater and
treated wastewater from the epuvalisation system, were less vigorous and produced significantly less
flowers of lower quality than flowers produced from plants irrigated with freshwater with the addition
of fertilizer. However, addition of fertilizer above 60ppm N had a negative effect on flower
production. Plants irrigated with wastewater and treated wastewater from the epuvalisation system
showed nitrogen deficiency symptoms indicating that the low flower production was most probably
due to the low nitrogen levels in the wastewater during that period. Addition of N fertilizer in treated
wastewater might be essential when used for irrigation depending on the plant used and level of
treatment of effluent.
170
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of European guidelines for reclaimed wastewater in the Mediterranean region. Wat. Sci. Tech., 33
(10-11), 303-316.
Asano, T. and Levine, A.D. (1996). Wastewater reclamation, recycling and reuse: past, present and
future. Wat. Sci. Tech., 33(10-11),1-14.
Chimonidou Dora, (2002). Country report of Cyprus. In Proceedings of the Regional Experts Meeting on
Flowers for the Future. Ismir-Turkey, 8-10 Oct, 2002, p.15-30.
Chimonidou Dora (2003). Flowers under protected cultivation with special emphasis on roses and
new cut flowers. FAO/AUB First National Conference on Integrated Production and Prodection
Management of Greenhouse Crops, p.105-114.
FAO, (1992). Wastewater as a source for crop nutrients. Extension publication. Rome, Italy.
Hespanhol, I. And A.M.E. Prost. (1994) WHO guidelines and national standards for reuse and water
quality. Wat. Res. Vol. 28: 119-124.
Hespanhol, I., (1990). Guidelines and integrated measures for public health protection in agricultural
reuse systems. J. Wat. SRT-Aqua 39: 227.249.
Jenkins, C.R., I. Papadopouloos and Y. Stylianou. (1994). Pathogens and wastewater use for
irrigation in Cyprus. In Proceedings “Land and water resources management in the Mediterranean
region”. Bari, Italy, 4-8 sept., 1994.
Papadopoulos I. and Savvides S., (2002). Optimisation of the use of nitrogen in the treated
wastewater reused for irrigation. In proceedings of IWA Regional Symposium on Water Recycling
in Mediterranean Region. Iraclio, Greece, 26-29 September 2002.
Papadopoulos I., (1995). Present and perspective use of wastewater for irrigation in the
nd
Mediterranean basin. 2 Intern. Symposium on Wastewater Reclamation and Reuse (A.N.
Angelakis et al., Eds.), IAWQ, Iraklio, Greece, October, Vol.2: 735-746.
Papadopoulos, I and Y. Stylianou. (1987). Secondary treated urban effluent as a source of N for
th
trickle-irrigated cotton, sunflower and sudax. In Proceedings of 4 International CIEC Symposium,
Braunscheweig, 11-14 May, 1987.
Papadopoulos, I and Y. Stylianou. (1988a). Trickle irrigation of cotton with sewage treated effluent. J.
Environ. Qual. Vol.17:574-580.
Papadopoulos, I and Y. Stylianou. (1988b). Treated effluent as a source of N for trickle irrigated
sudax. Plant and Soil 110: 145-148.
Papadopoulos, I and Y. Stylianou. (1991). Trickle irrigation of sunflower with municipal wastewater.
Agri. Water Manag. 19: 67-75.
I. Papadopoulos, Dora Chimonidou, S. Savides and P. Polycarpou , (2005). Optimization of
irrigation with treated wastewater on flower cultivations. Proceedings of the ICID Conference 7-11
December 2004, Cairo, Egypt. Options Mediterraneenes, Series B, No. 53 p.227-235.
WHO, (1973). Reuse of effluents: Methods of wastewater treatment and health safeguards. A report
of WHO Meeting of Experts. Technical Report No. 517. Geneva Switzerland.
WHO, (1989). Health guidelines for the use of wastewater in agriculture and aquaculture. Report of a
Scientific Group. Technical Report No. 778.
171
RESPONSE OF DURUM WHEAT (Triticum durum Desf.) CULTIVAR ACSAD
1107 TO SEWAGE SLUDGE AMENDMENT UNDER SEMI ARID CLIMATE
L. Tamrabet *, H Bouzerzour ** M. Kribaa * and M. Makhlouf ***
RNAMS Laboratory, Larbi Ben Mhidi University, Oum El Bouaghi (04000), Algeria
**
Biology Dept, Faculty of Sciences, Ferhat Abbas University, Setif (19000), Algeria
***
Experimental Farm, Field Crop Institute, Setif (19000), Algeria
*
SUMMARY - The use of sewage sludge on a large scale and at relatively low rates can contribute to
the husbandry of urban wastes. This is interesting since this utilization in agriculture appeared to
increase crop production. The results of the present investigation, whose objective was to study the
response of a rainfed cereal crop to organic amendment with sewage sludge showed an increase in
grain yield and yield component, mainly spike fertility and straw production. 30t/ha of sewage sludge
dry matter were as efficient as 66 kg /ha of mineral nitrogen.
Key words: Sewage sludge, durum wheat, grain yield, organic mater, mineral fertilization.
RESUME - L’utilisation des boues résiduaires sur de grandes étendues à des doses relativement
faibles permet d’apporter une solution à terme pour la gestion des déchets urbains. Cette solution est
d’autant plus intéressante que les boues utilisées dans le domaine agricole se révèlent bénéfiques en
terme d’augmentation de la production. Les résultats de la présente contribution dont l’objectif était
d’étudier la réponse d’une culture de céréale conduite en pluviale aux amendements organiques à
base de boues résiduaires indique une augmentation du rendement en grains et des composantes du
rendement notamment la fertilité de l’épi ainsi que la production de paille. Les apports de boue, pour
une moyenne de 30 t de ms/ha, s’avèrent aussi efficace que 66 kg d’azote minéral.
Mots clés: Boue résiduaire, blé dur, rendement, matière organique, fertilisation minérale.
INTRODUCTION
Expansion of urban populations and increased coverage of domestic water supply and sewerage
give rise to greater quantities of municipal wastewater. With the current emphasis on environmental
health and water pollution issues, there is an increasing awareness of the need to dispose of these
wastewaters safely and beneficially. Properly planned use of municipal sewage alleviates surface
water pollution problems and also takes advantage of its nutrients contain to grow crops.
Sewage sludge can be used to increase crop production, in those situations where the growth
conditions due to the unfavorable climate associated to the high production costs don't permit the
utilization of chemical fertilizers to overcome cultivated soil fertility problems (Chatha et al., 2002;
Pescod, 1992; Ripert et al., 1990).
In fact, soils treated with sewage sludge keep longer their relative humidity and their vegetation
develops a deeper rooting system as compared to non treated soils (Tester et al., 1982). Sewage
sludge liberates progressively nutritive elements they contain and made them available to the plant
along the crop cycle. Nitrogen availability is function of the prevailing climatic growth conditions; the
amount of applied sludge and the C/N ration (Pescod, 1992; Barbartik, 1985).
Soils treated with sewage sludge tended to have a neutral pH and a high phosphorus and organic
matter content (Mohammad et al., 2004; Gomez et al., 1984). However sewage sludge are often a
source of ground water pollution when their content in high in nitrate (Xanthoulis et al., 1998). They
are a source of sol salinity (Tasdilas, 1997), heavy metals pollution (Mohammad et al, 2004; Bozkurt
et al., 2003; Aboudrare et al., 1998) and odors nuisance (Sachon, 1995).
173
The present study investigates the response of durum wheat (Triticum durum Desf.) variety Acsad
1107 to the application of sewage sludge under semi arid climate.
MATERIALS ET METHODS
The experiment was conducted on the experimental site of the Agricultural Farm of the Field Crop
Institute of Setif in the Northeastern part of Algeria (5° 24’ 51’’ E longitude and 36° 11’ 21’’ N latitude,
and 1000 m altitude) during the 2002/03 crop season. Climate is Mediterranean, characterized by
mild rainy winter and dry hot summer with average temperature in summer 24.1°C and 7°C in winter
and average annual precipitation of 397.0 mm (AFFCI, 2003). Total amount and distribution of rainfall
for the period of the study are presented in (Table 1). The soil is loamy clay and its chemical
characteristics are presented in (Table 2).
The trial was laid out in a randomized complete blocks design with three replications. Five
treatments were compared: a check without application of sludge nor nitrogen fertilization, a treatment
without sludge but fertilized with 33 units ha-1 of urea, applied during the tillering stage, and three
treatments with respectively 20, 30 et 40 tons dry sludge ha-1. The characteristics of the dry sludge
used are reported in (Table 3).
The different physico-chemical analyses of the soil and the sludge were carried out at the
beginning of the experiment on dry and fine samples (< 2 mm). The determination of the pH and the
electrical conductivity were done by Consort C535 Multiparameter on 1:2.5 and 1:5 soil/distilled water
respectively, the soil texture by the hydrometer method and the others by standards methods
(Chapman and Pratt, 1982).
Acsad 1107, a durum (Triticum durum Desf.) genotype, was sown on December 20th 2002 at a 300
seeds m-2 rate on plots whose dimensions were 6 rows x 5 m long x 0.20 m space between rows.
Emergence was noted on December 28th 2002. Dry sludge was passed through 10x10 mm mech,
and applied onto the experiment at the tillering stage. Heading was noted on May 5th 2003 and the
crop was harvested on June 16th 2003.
Plant height (PHT) was measured at crop maturity; the number of spikes (SN) and total dry matter
(BIOM) produced per m2 of soil were estimated from vegetative samples harvest from
Table 1. Precipitations and temperatures at the experimental site of the Agricultural Farm of the Field
Crop Institute (Setif, Algeria) during the period of the study 2002/03
Rainfall (mm)
September02
October
02
November02
December
02
January
03
February
03
March
03
April 03
May 03
June 03
D1
1.20
6.40
D2
0.30
6.60
D3
2.80
2.90
Total
4.30
15.90
Min
14.67
11.40
Max
26.49
20.63
Mean
20.68
16.01
59.60
52.50
11.80
11.90
29.80
3.00
101.20
67.40
6.29
3.65
12.91
12.18
9.25
7.91
16.40
28.80
71.80
117.00
0.98
6.22
3.80
19.20
15.00
4.20
38.40
3.58
11.63
4.49
0.60
5.80
31.20
37.60
4.84
14.66
9.92
20.02
18.00
38.40
14.80
2.40
20.40
3.40
13.40
0.60
38.22
43.80
59.40
8.30
11.22
17.95
16.96
22.63
30.32
12.63
19.93
24.14
D1, D2, D3 : Decades 1, 2 et 3 of the month.
174
Temperature (°C)
Table 2. Characteristics of the soil (0-20cm) used in the experiment at the experimental site of the
Agricultural Farm of the Field Crop Institute (Setif, Algeria)
Parameters
pHH2O
EC
OM
TC
Db
Hs
Hfc
Hwp
Units
-
(mS/m)
(%)
(%)
(g/cm3)
(%)
(%)
(%)
Mean values
8.1
0.23
1.7
19.45
1.33
51.5
36.5
16.5
Texture
Loamy
clay
EC: Electrical conductivity, OM : Organic Matter, TC : Total Carbone, Db : Bulk density,
Hs : Humidity at saturation, Hfc : Humidity at field capacity, Hwp : Humidity at wilting point.
Table 3. Characteristics of the sewage sludge originating from the effluents treatment plant of Ain
Sfiha (Setif, Algeria).
Parameters
Units
Mean
values
Humidity
pH(H2O)
EC
TN
C
TP
K
C/N
%
-
(mS/cm)
%
%
%
%
-
80
7.3
2.61
3.30
33.5
5.7
0.5
10.15
EC : Electrical Conductivity , TN : Total Nitrogen, C : Carbone, TP : Total Phosphorus, K : Potassium
1 row x 1m long area. Grain yield (GY) was measured from the combine harvested trial. Thousand
kernel-weight (TKW) was estimated from the count and weight of 250 kernels per replicate. The
variables number of kernels produced per m2 ( KNM2) , per spike (KS), aerial biomass accumulated at
heading (BIOH), vegetative growth rate (VGR), kernel filling rate (KFR), harvest index (HI) and
amount of straw produced (STR), have been deduced by calculus using the following formulas:
KNM2 = 1000(GY/TKW)
(1)
Where:
GY: grain yield (g m-2)
TKW: thousand kernels weigh (g)
KS: KNM2 /SN, with
KS: Number of kernels per spike
SN: Spike number. m-2
BIOH = BIOM- GY
(2)
Where:
BIOM: above ground biomass measured at maturity (g m-2)
VGR = BIOH/DHE
(3)
Where:
VGR: Vegetative growth rate (g m-2 day-1)
BIOH: above ground biomass accumulated at heading stage (g m-2),
DHE: number of calendars days from emergence to heading stage (days).
KFR = GY/KFP
(4)
Where:
KFR: rate of filling of the number of kernels produced per m2 (g m-2 days-1),
KFP: number of calendar days in the kernel filling period (days).
HI = 100 (GY/BIOM)
(5)
175
The collected data were subjected to an analysis of variance. Contrast was employed to test the
significance of the following treatments effects (1) Check vs N + Sludge, (2) N vs sludge, (3) sludge
linear and (4) sludge quadratic (Steel and Torrie, 1980). The relative comparisons between
treatments were done according to the following formulas:
Amendment effect N + Sludge (%) = 100 [ (XN+S - Xc)/Xc]
(6)
Where:
XN+s: mean of N+ sludge treatments
Xx: check mean
Sewage sludge effect (%) = 100 [ (XS-XC)/(XN-XT)]
(7)
Where:
XS: mean of sludge treatment
XN: mean of N treatment
Xc: check mean.
RESULTS AND DISCUSSION
The analysis of variance showed a significant treatment effect for the whole variables measured
but not for the number of spikes (Table 4). The non significant treatment effect for the number of
spikes could explained by the fact the amendment (sludge and N) was applied later on, at the tillering
stage, when this yield component was partially expressed.
The amount of sludge applied remains below the nutriments requirement of the plant since the
quadratic effect was not significant for the measured traits. The linear effect of the applied sludge was
not significant for the thousand kernel weight, the number of kernels per spike and the harvest index
(Table 4). The comparison between the check and amendment (N+S) means indicated that mineral
as well as organic fertilization were beneficial to the expression of the measured variables of the crop
except the number of spikes produced per unit square of land (Table 5).
Table 4. Means squares of the analysis of variance of the measured variables
Source
dll
GY
SN
KNM2
TKW
KS
BIOH
VGR
KFR
BIOM
HI
STR
PHT
Treatment
4
20939.4**
1067.2ns
3201164**
20.35*
76.55**
66006.7**
4.22**
21.7**
45893.0**
85.46**
61169**
406.9**
S+N vs C
1
62489.5**
411.2ns
1848504**
72.6**
225.2**
177055**
11.33**
64.79**
449916**
293.7**
196459**
1316.1**
S vs N
1
17398.1**
458.8ns
9054255**
4.84ns
78.8**
39190.7**
2.51**
18.04**
108812**
8.06ns
27749**
164.7**
S lin
1
3310.7**
3398.6*
792289**
3.23ns
1.25ns
43146.3**
2.76**
3.43*
70360**
0.43ns
19728**
140.2**
S qua
1
559.5ns
0.00ns
11198ns
0.72ns
1.01ns
4634.8ns
0.30ns
0.58ns
1973.9ns
39.6ns
738.3ns
6.72ns
error
8
301.2
389.1
156915.8
2.92
1.96
1967.6
0.13
0.31
833.9
8.01
763.6
4.9
C= Check, N = nitrogen, S= Sludge, GY = grain yield (g m-2), SN= number of spikes/m2, KNM2 = number of
kernels /m2, TKW = 1000 kernel weight (g), KS= number of kernels/spike, BIOH= above ground biomass
-2
-2
-1
-2
accumulated at heading stage (gm ), VGR = vegetative growth rate (g m day ), GFR = filling rate of the KNM
-2
-1
-2
(g m day ), BIOM = above ground biomass measured at maturity (g m ), HI = harvest index (%), STR = straw
-2
yield (g m ), PHT = plant height (cm); ns,*,** = effect non significant and significant at 5 and 1% probability level
respectively.
176
Under the growth conditions of the present experiment, the relative contribution of the amendment
(N + S) to the increase in the means of the measured variables ranged from 12% for the thousand
kernel weight to 168% for straw yield. The amendment effect was negative for the harvest index
which is reduced by 20.0% relatively to the mean expressed by the check treatment. This could be
explained by the fact that the nitrogen or the sludge applied had a more pronounced effect on the
accumulated above ground biomass than on gain yield (Table 4, Fig. 1).
180
160
140
120
100
% 80
60
40
20
0
-20
GY
KNM2
TKW
KS
BIOH
VGR
KFR
BIOM
HI
STR
PHT
Fig. 1. Contribution of the applied amendment (N+ S) to the increase in the mean values of the
measured traits relatively to the mean values of the check.
Table 5. Mean values of the different treatments
SN
GY
KNM2
TKW
KS
BIOH
VGR
KFR
BIOM
HI
STR
PHT
C
318.9
147.5
3159.2
46.53
9.9
223.3
1.79
4.75
370.8
54.2
169.5
58.7
N+S
305.8
308.9
5933.7
52.03
19.6
494.9
3.96
9.95
803.7
43.2
455.6
82.1
N
316.5
242.9
4769.1
50.93
15.1
395.9
3.17
7.82
638.8
41.7
372.3
75.6
S
302.3
330.9
6321.9
52.40
21.0
527.9
4.22
10.65
858.7
43.6
483.4
84.2
20
278.5
301.8
5879.6
51.5
21.3
459.1
3.67
9.72
760.9
44.9
419.6
80.0
30
302.3
342.0
6479.6
52.8
21.5
495.8
3.97
11.01
837.8
40.6
496.2
83.0
40
326.1
348.7
6606.4
52.9
20.4
628.7
5.03
11.23
977.5
45.4
534.3
89.7
C= Check, N = nitrogen, S= Sludge, GY = grain yield (g m-2), SN= number of spikes/m2, KNM2 = number of
2
kernels /m , TKW = 1000 kernel weight (g), KS= number of kernels/spike, BIOH= above ground biomass
accumulated at heading stage (gm-2), VGR = vegetative growth rate (g m-2 day -1), GFR = filling rate of the KNM-2
-2
-1
-2
(g m day ), BIOM = above ground biomass measured at maturity (g m ), HI = harvest index(%), STR = straw
yield (g m-2), PHT = plant height (cm).
177
The relative increase in the mean values of the yield component was smaller compared to the
increase noted in grain yield. Grain yield increase resulted from the multiplicative effects of the
increase obtained in the yield components. The thousand kernel weight was the yield component
which was the less sensitive to the amendment effect; because this trait is formed when climatic
growth conditions become less favorable.
The increase noted in the mean value of straw after application of sludge or mineral nitrogen
indicated that organic or mineral amendment induced a better expression of the above ground
biomass compared to the grain yield, which had a negative effect on harvest index as explained
above.
The comparison between organic amendment and mineral fertilization treatments showed that the
mean values of these treatments did not differed significantly for the number of spikes, thousand
kernel weight and harvest index (Tables 4 and 5). For these traits the effect of sewage sludge
application was similar to the effect of nitrogen mineral fertilization. Organic amendment induced a
relative increase of 128.1% for plant height and 213.5% for the number of kernels per spike. Grain
yield showed a 192.7% increase relatively to the check mean yield (Table 5, Fig. 2).
On average application of sewage sludge appeared to be more beneficial for the crop than mineral
nitrogen fertilization. The effect of the applied sewage sludge was significant and more apparent on
spike fertility, above ground biomass accumulated at heading and maturity, on vegetative growth rate
and grain filling rate.
These results indicated that applying sewage sludge to cultivated soils induced an increase in crop
grain yield and contributed to disposal of and recycling of this waste material (Ripert et al., 1990). The
increases noted in grain yield and in the yield associated variables are due to the high concentrations
of nitrogen, phosphorus and organic matter of the sewage sludge applied.
Bouzerzour et al. (2002) reported that the application of sewage sludge increased leaves
dimensions, leaf area index, accumulated above ground dry matter, tillering capacity and plant height
of barley (Hordeum vulgare L.) and oat (Avena sativa L.) genotypes, evaluated in pots experiment.
They noted also that the response of the measured variables to the applied sewage sludge was linear
which corroborated the results of the present study. The maximum amount of 40 t ha-1 of applied
sewage sludge did not show any harmful effect on the expression the measured parameters.
220
210
200
190
%
180
170
160
150
140
130
120
GY
KNM2
KS
BIOH
VGR
GFR
BIOM
STR
PHT
Fig. 2. Relative increase in the mean values of the measured traits due to the effect of applied
sewage sludge as % of the mineral nitrogen fertilization effect
178
In the present study yield increase originated from the increase noted in the number of kernels
produced per unit square of soil (r GY/KNM-2= 0.98*) and to the number of kernels per spike (rGY/KS =
0.92*) but not from the fertile tillering ability of the crop (r GY/SN =0.21ns). During the course of the
experiment the check treatment was somewhat earlier and senesce more rapidly than the amended
treatments. Application of sewage sludge acted as a seal, it reduced from the soil evaporation, and
helped to keep soil more moist because of its high organic matter content.
Sewage sludge is considered as a substrate which is susceptible to contribute to maintain soil
organic matter and to improve soil structural stability, cationic exchange and water retention
capacities (Gomez et al., 1984). Barbartik et al. (1985) noted that application of sewage sludge
during 4 consecutive cropping seasons increased the upper the organic matter content of the upper
15 cm soil horizon from 1.2 to 2.4%.
Tester et al. (1982) studied the response of tall fescue (Festuca arundinacea L) to sewage sludge;
they observed that soil amendment with sewage sludge improve tall fescue nitrogen nutrition,
stimulated root growth and increase forage production comparatively to the non amended check. With
ray grass (Lolium perenne L), Guiraud et al. (1977) observed an improvement of nitrogen
concentration of tissue of plants grown in sewage sludge amended soils. Cherak (1999) noted an
improvement of the tillering capacity of oat (Avena sativa L.) grown under sewage sludge amended
soil.
According to Sachon (1995) incubated sewage sludge develops aerobic and anaerobic chemical
reactions which, in 6 to 7 weeks, reduced the organic matter to the form of compost which is similar to
the humus. The mineralization of organic nitrogen is dependent on the C/N ratio, higher this ratio is
the lower the mineralization will be (Barbartik et al., 1985; Sachon, 1995).
CONCLUSION
Use of wastewater in agriculture could be an important consideration when its disposal is being
planned in arid and semi-arid regions. Treated sludge can be applied to growing cereal crops without
constraint. Land application of raw or treated sewage sludge can reduce significantly the sludge
disposal cost component of sewage treatment as well as providing a large part of the nitrogen and
phosphorus requirements of many crops. The organic matter in sludge can improve the water
retaining capacity and structure of soils, especially when applied in the form of dewatered sludge
cake. Sludge application resulted in significantly increased crop yields, attributed to the beneficial
effects on soil structure and to the nutrients contain.
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wastewater. Faculty of agronomic sciences, Gembloux. 10 pp.
180
REUSE OF MEMBRANE FILTERED MUNICIPAL WASTEWATER FOR
IRRIGATING VEGETABLE CROPS
A. Lopez *, A. Pollice *, G. Laera *, A. Lonigro **, P. Rubino ** and R. Passino *
* CNR, Istituto di Ricerca Sulle Acque, Viale F. De Blasio 5, 70123 Bari, Italy
** Università di Bari, Dip. Scienza delle Produzioni Vegetali, Via Amendola, 70123 Bari, Italy
SUMMARY - In the framework of a nationally relevant project named AQUATEC carried out in the
period 2002-2006 and focused on innovative tools for mitigating the water-stress and/or scarcity in
southern Italy, a technical scale investigation was performed to test the suitability of membrane
filtration for agricultural reuse of municipal wastewater. Membrane filtration was tested at Cerignola
(FG) where a test field was also operated and three different crops (processing tomato, fennel and
lettuce) were grown in rotation. The experimental period considered in this paper spans between
summer 2003 and spring 2005. Technological, water-quality and agronomic aspects were carefully
investigated. Throughout the whole investigation the quality of treated wastewater was monitored
(chemically and microbiologically) and compared with conventional water pumped from a local freatic
well. Both water sources were used in parallel for irrigating two separate plots of the test field. Except
for higher Cl-, Na+ and B concentrations, the average chemical quality of tertiary filtered municipal
wastewater was comparable with that of conventional well-water. Irrigation with treated wastewater
caused an increase of Na+, Ca++ and EC values in the soil during summer periods that, however, were
recovered during the following rainy seasons. From the microbial standpoint, unexpectedly, the plot
irrigated with well-water resulted more contaminated than that irrigated with treated wastewater. The
measured content of heavy metals in vegetables was independent of the water used for irrigation.
Crops productivity did not show significant differences between the plot irrigated with treated
wastewater and the one watered with well-water.
Keywords - Wastewater reuse, membrane filtration, alternative water resources, water scarcity
management.
RESUME - Dans la structure d'un projet nationalement pertinent, nommé AQUATEC, fait dans la
période 2002-2006 et s'est concentré sur les outils innovateurs pour atténuer la stress d'eau et/ou la
pénurie en Italie du sud, une enquête a été exécutée à l'échelle technique pour tester la convenance
de filtration de la membrane pour la réutilisation agricole d'eau usée. La filtration de la membrane a
été testée à Cerignola (FG) où une zone d'essai a aussi été opérée et trois récoltes différentes
(tomate traité, fenouil et laitue) ont été grandi en rotation. La période expérimentale considérée dans
ce papier a été déroulée entre été 2003 et printemps 2005. La qualité d’eau technologique et les
aspects agronomiques ont été enquêtés avec soin. Partout dans l'enquête entière la qualité d'eau de
rebut soignée a été dirigée (chimiquement et microbiologiquement) et bien comparé avec les eaux
conventionnelles pompées d'un phréatique local. Les deux sources de l'eau ont été utilisées en
parallèle pour irriguer deux intrigues séparées de la zone d'essai. À l'exception de la plus haute
concentration en Cl-, Na+ et B, la qualité chimique moyenne de l’eau usée de filtration tertiaire était
bien comparée avec celle conventionnel. L'irrigation avec eau usée traitée a causé une augmentation
de la valeur de Na+, Ca++ et EC dans le sol pendant les périodes estivales qui, cependant, s'est été
remises pendant les saisons pluvieuses suivantes. Du point de vue microbien et de façon inattendue,
l'intrigue irriguée avec les eaux de puits est plus contaminé que celui irrigué avec les eaux usées
traitées. Le contenu mesuré de métaux lourds dans les légumes était indépendant de l'eau utilisée
pour l’irrigation. La productivité des récoltes n'a pas montré de différences considérables entre
l'intrigue irriguée avec les eaux usées traitées et celui arrosé avec les eaux des puits.
Mots-clé - réutilisation de l'Eau usée, filtration de la membrane, ressources de l'eau alternatives,
gestion de la pénurie de l'eau.
181
INTRODUCTION
In Italy, an overall annual water inflow around 155 billions m3 yields only 52 billions m3 of
resources actually utilizable. However, because of the geographically uneven rainfalls distribution, in
southern regions such figures drastically decrease as rainfalls are much lower (even 30 % less) than
the national average (980 mm/y) (IRSA-CNR, 1999). Furthermore, in such areas, very often, only part
(15-20%) of the already scarce water resources is actually available because of the out-of-date local
water distribution systems. Accordingly, most of such regions have to face major problems related to
water shortage for agriculture and, in some cases, even for drinking purposes.
With the aim to tone down water stress in these areas, a national relevant and strategic R&D and
Training project whose acronym is AQUATEC has been carried out in five Regions (Campania,
Apulia, Sicily, Calabria and Basilicata) in the period 2002-2006. The project was mainly focused on
developing and/or testing innovative tools for contributing to mitigate the chronic water-stress and/or
scarcity peculiar of these areas.
Referring to Apulia, it is a southern east region extended for about 20,000 km2 with 800 km of
coasts and about 4,500,000 inhabitants. At national level, it is the region with the lowest rainfall
average value (i.e. about 660 mm) and, because of its orography and its hydro-geological subsoil
features, its average runoff coefficient value (0.23) is also the lowest (IRSA-CNR, 1999).
Nevertheless, the economy of the region, mainly based on two water demanding activities, agriculture
and tourism, is ranked as one of the best in the south of the Country. This is possible thanks to the
Apulian water aqueduct (AQP), the largest in Europe, which imports water from three bordering
regions: Campania, Lucania and Molise. AQP is a complex multi-purposes and multi-reservoirs
system with 19,635 km of distribution networks; it serves 4,623,349 inhab. and distributes, net of
leakages, 309,416,113 m3 of drinking water (http://www.aqp.it/home.htm).
As for the Apulian agricultural sector, it must be pointed out that in spite of the scarce regional
rainfalls, most (78.8%) of the Apulian land is used for agricultural purposes (i.e., 15,239 km2 over a
total area of 19,332 km2). However, only 23.8 % (i.e., 3,653 km2) of the cultivated area is irrigated.
Although such a small portion of irrigated land, in order to satisfy the agricultural water demand, in
addition to the resources provided by large irrigation-water distribution consortia, in the region
relevant amounts of water are withdrawn from local aquifers as a negative gap of about 700 Mm3
exists (Portoghese et al., 2005). In practice, to fill this gap, it has been estimated that regional farmers
have drilled, more or less legally, about 140,000 wells and because of such an extensive groundwater
over-exploitation, particularly in coastal areas, a sharp salinity increase, with peaks such high as
20,000 µs/cm, has taken place due to sea water intrusion phenomena (Maggiore et al., 2001).
Taking into account that agricultural reuse of municipal wastewater is an appropriate tool for
mitigating local scarcity of water resources (Lazarova, 2003) and that in the whole Apulian region
about 250 Mm3/y of treated wastewater could be reused for partially filling the above gap, within the
AQUATEC project a specific activity has been planned and carried out in Apulia testing the suitability
of membrane filtration technology for agricultural reuse of municipal wastewater. At a test field located
in the Municipality of Cerignola (FG), three different crops (processing tomato, fennel and lettuce)
were grown in rotation. Membrane filtration was chosen as viable technology due to its claimed
efficiency for treating wastewaters with variable characteristics and removing pathogenic
microrganisms. The main beneficial features of such a technology are the possibility of avoiding
chemical disinfection and its toxic by-products as well as maintaining fertilizing species such as
ammonia and phosphate ions in treated effluents.
This paper just reports the main results recorded during the investigation carried out in Apulia
within the AQUATEC project.
MATERIALS AND METHODS
Membrane filtration pilot plant
Wastewater tertiary treatment by membrane filtration was carried out at the pilot scale by a hollow
fiber submerged system (Zenon Environmental Inc., Canada). The membrane fibers were assembled
182
in a module (ZeeWeed®) having a total membrane surface of 23.5 m2. The module was plunged into a
1.5 m3 steel tank fed with municipal secondary effluent and was operated out-in, i.e. the permeate
was extracted from the internal surface of the fibers by imposing a negative pressure (never
exceeding 0.7 bar) to both ends of the module, where the extremities of all fibers were connected.
Hollow fibers have an external diameter of about 1.9 mm, internal diameter around 1.0 mm, and
nominal (average) pore size of 0.03 µm. Operational cycles included extraction of the permeate (300
sec), and backwash (60 sec). The latter step was carried out by pumping, under positive pressure, a
fraction of the permeate inside the fibers to unclog their pores. Coarse bubble aeration was also
provided in the filtration tank to increase the shear stress and limit biofilm formation on the external
surface of the hollow fibers. Operational parameters such as transmembrane pressure (TMP) and
permeate flux (J) were regularly recorded. The pilot plant had a maximum productivity of about 0.7
m3/h and was installed at the municipal wastewater treatment plant of Cerignola, a town of 50,000 PE
in South-Eastern Italy. A fraction of the secondary effluent of the full scale plant was sent to the pilot
for tertiary filtration, and the permeate was stored into six tanks (5 m3 each). Although each irrigation
required about 15 m3 of water, a total stored volume of 30 m3 was always available in order to match
the continuous production with the discontinuous demand for irrigation. The test-field was located
about 100 m away from the pilot plant and was connected to the storage tanks through a pipeline
(Pollice et al., 2004).
Experimental field
Two-year studies (2003-2004) were carried out to compare the effects on soil and crops of two
types of water, tertiary filtered municipal wastewater (“Treated Wastewater”, TW) and conventional
water (control) pumped from a freatic well (“Conventional Source”, CS), on three crops in succession.
The three crops chosen for the investigation were processing tomato, fennel and lettuce.
Processing tomato (Lycopersicon esculentum Mill.) was transplanted in June 2003 in double rows
160 cm apart from each other, realizing a theoretical plant density of 3.1 plants/m2, and was
harvested in September 2003. Fennel (Foeniculum vulgare Mill.) was transplanted in October 2003 in
single rows, 0.3 m apart from each other, realizing a theoretical plant density of 11.1 plants/m2, and
was harvested in April 2004. Lettuce (Lactuca sativa L.) was transplanted in April in single rows, 0.4
m apart from each other, realizing a theoretical plant density of 6.25 plants/m2, and was harvested in
July 2004. For all crops, drip irrigation was used by placing the dripping lines between each couple of
tomato rows and every other row of fennel and lettuce.
The three crops were irrigated when the soil water deficit (SWD) in the root zone was equal to 35%
of the total available water (TAW). Irrigation was scheduled based on the evapotranspiration criterion,
providing water to the crops when the following conditions were met:
n
1Σ
(Etc - Re) = 30 mm for tomato, and 25 mm for fennel and lettuce
where:
n = number of days required to reach soil water deficit limits starting from the last watering;
Etc = crop evapotranspiration (mm);
Re = rainfall (mm).
Evapotranspiration was expressed as follows:
Etc = E*Kp*Kc
with
E = “class A” pan evaporation (mm);
Kc = crop coefficient;
Kp = pan coefficient (0.8).
The experimental field was cultivated according to the methods commonly adopted by the local
farmers.
183
Analyses
Tertiary filtered wastewater and conventional water samples were collected on every watering and
analysed according to standard methods (Eaton et al., 1995). The measured parameters were TSS,
COD, N-NH4+, NO3-, P-PO43-, electrical conductivity (ECw), total and faecal coliforms, Escherichia coli
and Salmonella. Moreover, metals such as Ca, Mg, Na, K, B, Fe, Mn were monitored in both the
filtered effluent and the conventional well water.
Soil samples were taken from each plot after every crop cycle, at depths decreasing from 0 to 0.8
m, every 0.2 m. They were analyzed for N, P2O5, K, organic matter (O.M.), pH, electrical conductivity
on saturated paste extract (ECe), SAR, alcalinity (as CaCO3), and exchangeable sodium percentage
(ESP) according to standard procedures (Sparks, 1996).
Microbiological analyses (total and faecal coliforms, Escherichia coli, and Salmonella) were also
carried out on soil samples at depths of 0-0.1 m and on tomato fruits, fennel heads and lettuce leaves,
according to standard methods (Scharf, 1966; Woomer, 1994).
Finally, crops productions were compared and dried samples of the crops were extracted and
analysed for their content of heavy metals in order to evaluate the differences due to irrigation with the
two water sources.
RESULTS AND DISCUSSION
Pilot plant performance
The operational parameters of the membrane filtration pilot plant are summarized in Table 1.
Table 1. Operating parameters of the membrane filtration pilot plant.
Parameter
Unit
Operational value
Production (suction) time
sec
300
Backwash time
sec
60
Feed flowrate
L/h
2000
Production (suction) flowrate
L/h
300
Backwash flowrate
L/h
450
Frequency of chemical cleanings
For suction pressure > than 0.6 bar
During the considered experimental period, the pilot plant operated discontinuously according to
the water demand for irrigation and to the management needs of the filtration system. In particular,
the operating pressure of the system tended to increase over time due to the variable quality of the
secondary wastewater. This pressure increase reflected the tendency of the membrane surface to
foul, and was counteracted by periodical chemical cleaning of the module. This was done every time
the operating negative pressure reached 0.6 bar, and consisted in sinking the module in a 200 mg /L
NaClO solution for 4-6 hours. The solution was removed from the tank and the module rinsed before
re-starting the plant’s operation. Figure 1 shows the net flux of the filtration system (i.e. the net
productivity of tertiary filtered wastewater) and the operating pressure over time. In the period
between June and November 2003 the plant was operated by imposing higher permeate fluxes, and
this resulted in more rapid decrease of membrane permeability (i.e. pressure increase). Chemical
cleaning was required more often during this period than in the following ones when lower fluxes (and
better influent quality) caused slower increase of the suction pressure (Fig. 1).
350 m3 of the tertiary filtered wastewater produced by the pilot plant were used for irrigation of the
first experimental crop (tomato) that was transplanted in June and removed in September 2003. The
following experimental period spanned from February to April 2004, when the plant produced about
184
1000 m3 of treated effluent, of which 150 m3 were used for the irrigation of fennel. The last period
started in June and ended in July 2004, and 100 m3 of reclaimed wastewater allowed the
experimental cultivation of lettuce.
The average quality of the tertiary filtered municipal wastewater was comparable with the well
water conventionally used for irrigation (Table 2). Chemical, physical and microbial characteristics of
the tertiary filtered municipal wastewater and the conventional well water showed similar
concentrations except for Cl-, Na+ and B that were higher in the treated wastewater. On the contrary,
the microbial pollution resulted higher in the well water. However, both chemical and microbiological
parameters of the two water sources were below the regional limits for unrestricted irrigation except
for the SAR. The higher salinity in the reclaimed wastewater was attributed to the presence of local
preserved food industries, whose effluents partly reached the municipal sewer system.
The test field and the crops
Irrigation seasonal time-spans of tomato, fennel, and lettuce crops were of 57, 106, and 12 days
respectively. The three crops were provided with 11, 4, and 3 waterings respectively (seasonal
irrigation volumes 3300, 1000, and 750 m3 ha-1 respectively).
Irrigation with tertiary filtered wastewater caused an increase of Na+, Ca++, SAR and EC along the
soil profile (0-0.8 m) during summer 2003, when a higher number of waterings was provided.
However, lower values were recovered in the soil during the following rainy season (Fig. 2).
Soil microbial contamination results show that the plots irrigated with the conventional well water
were more polluted than those irrigated with the treated municipal effluent (Fig. 3). Salmonella was
never found in either plots. Microbiological analyses performed on crop samples showed that total
coliforms were the only indicator found on tomato fruits, fennel heads, and lettuce leaves (Fig. 4).
Irrigation with treated wastewater did not affect the productivity of the different crops, although the
occasional presence of significant chlorine concentrations caused some effects on the plants. The
unexpected occurrence of chlorine in the secondary effluent before chlorination was attributed to
occasional management practices at the full scale plant.
12
1,2
net flux
pressure
1,0
8
0,8
6
0,6
4
0,4
2
0,2
0
Jun-03
Aug-03
Oct-03
Dec-03
Feb-04
Apr-04
Jun-04
pressure (bar)
net flux (L m-2 h-1)
10
0,0
Aug-04
time (days)
Fig. 1. Behaviour of the membrane filtration pilot plant over the investigated period in terms of
productivity (net flux) and energy/maintenance requirements (trans-membrane pressure).
185
Table 2. Average values of the main physical, chemical and microbial parameters measured, over the
research period, in the two types of compared water.
Treated
Regional
Conventional
Wastewater
Source
limits (*)
TSS
mg/L
< d.l.
< d.l.
10
COD
mgO2/L
43
32
50
mg/L
1.0
0.3
2
N-NH4+
mg/L
9.5
5.8
NO3mg/L
2.3
2.3
10
P-PO4mg/L
329
124
Na+
mg/L
45
44
Ca++
Mg++
mg/L
27
51
mg/L
460
256
500
Clmg/L
30
18
K+
B
mg/L
1.0
0.1
2.0
Fe
mg/L
0.0
0.0
2.0
Mn
mg/L
0.0
0.0
0.2
ECw
dS/m
2.4
1.5
3.0
S.A.R.
13
4
10
Total coliforms
Cfu/100mL
146
293
Faecal coliforms
Cfu/100mL
38
73
Escherichia Coli
Cfu/100mL
11
9
10
Salmonellae
Cfu/100mL
0
0
0
(*) Limits established by Apulia Region for unrestricted reuse of municipal wastewater in agriculture.
Parameter
Unit
2,5
140
TW
2,0
ECe (dS/m)
100
1,5
80
60
CS
1,0
40
Rainfall (mm)
120
20
0,5
04/03/03
8
04/29/04
ju
l
ja
n
fe
b
m
ar
ap
r
m
aj
ju
n
oc
t
no
v
de
c
10/03/03
07/12/04
TW
140
S.A.R.
7
120
6
100
5
80
60
4
CS
3
40
Rainfall (mm)
0,0
ju
l
au
g
se
p
ap
r
m
ay
ju
n
0
20
2
0
04/03/03
10/03/03
04/29/04
ju
l
fe
b
m
ar
ap
r
m
aj
ju
n
ja
n
oc
t
no
v
de
c
ju
l
au
g
se
p
ap
r
m
ay
ju
n
0
1
07/12/04
Fig. 2. Average values of soil Electrical Conductivity (ECe) and SAR versus time recorded over the
research period and compared with rainfall in plots watered with conventional source (CS) and
treated wastewater (TW). Histograms represent the rainfall.
186
10000
MPN/g of dry soil
1000
Tomato
Tomato
Treated Wastewater
Conventional Source
Tomato
100
Fennel
Lettuce
10
Lettuce
1
Fennel
Fennel
Faecal Coliform
Total Coliform
Lettuce
Tomato
Fennel Lettuce
Salmonella
Escherichia coli
Fig. 3. Average values of total and faecal coliforms, Escherichia coli and Salmonella (as MPN/g of dry
soil) measured at harvesting time in soil samples from plots watered with conventional source
(CS) and treated wastewater (TW).
10000
Treated Wastewater
Conventional Source
Lettuce
MPN/g of marketable yield
1000
Tomato
Tomato
Tomato
100
Lettuce
10
Fennel
Lettuce
1
Total Coliform
Fennel
Fennel
Faecal Coliform
Escherichia coli
Tomato Fennel
Lettuce
Salmonella
Fig. 4. Average values of total and faecal coliforms, Escherichia coli and Salmonella (as MPN/g of
marketable parts of vegetables) measured at harvesting time on tomato fruits, fennel heads
and lettuce in plots watered with conventional source (CS) and treated wastewater (TW).
187
The content of heavy metals in the vegetables was observed to be independent of the water
source used for irrigation. Higher levels of some specific metals were occasionally measured in the
crops irrigated with treated wastewater, but these concentrations were below those considered to
cause acute toxicity (Table 3).
Table 3. Heavy metals average concentrations in crops irrigated with well water (CS) and treated
wastewater (TW).
Tomato fruits
Fennel heads
Lettuce leaves
CS
CS
TW
5
10
Metal
Unit
CS
TW
Fe
mg/kg
12
13
Al
mg/kg
4.0
1.2
Cu
mg/kg
0
0
Zn
mg/kg
0.4
2.0
9
Pb
mg/kg
0
0
Mn
mg/kg
0
0
TW
Common
Toxic
range
range
30-300
7-75
75
3
4
3-20
25-40
10
6
6
15-150
500-1500
0
0
0
0
2-5
400-200
92
101
90
48
15-150
CONCLUSIONS
The main results obtained during a two-year field investigation aimed at evaluating the feasibility of
using membrane filtered secondary effluents for irrigating vegetable crops (tomato, fennel, lettuce),
were the following:
• Except for higher Cl-, Na+ and B concentrations, the tertiary filtered municipal wastewater was
comparable with the well water conventionally used for irrigation in terms of average quality.
Chemical and microbiological parameters of both water sources were below the local limits fixed
for unrestricted irrigation, except for SAR. Wastewater salinity was due to uncontrolled effluent
dumping into the sewer from local industries.
• Irrigation with tertiary filtered wastewater caused an increase of Na+, Ca++, SAR and EC values
along the soil profile when higher volumes of water were provided (in summer), but these values
returned to the background level during the rainy season.
• From the microbial contamination standpoint, unexpectedly, the plots irrigated with well water
resulted more polluted than those irrigated with treated municipal effluent, possibly due to
untreated wastewater discharge into the water table that caused groundwater faecal
contamination. Also, the only indicator found on the irrigated crops were total coliforms.
• The content of heavy metals in the vegetables was independent of the water source.
• Irrigation with treated wastewater did not affect crops productivity except when unscheduled spikes
of relevant amount of chlorine occurred in the secondary effluent due to operational practices at
the full scale plant.
REFERENCES
Eaton, A.D., Clesceri, L.S. and Greenberg, A.E. (Eds.) (1995). Standard Methods for the Examination
of Water and Wastewater. 19th edn, American Public Health Association/American Water Works
Association/Water Environment Federation, Washington DC.
IRSA-CNR (1999). Un futuro per l’acqua in Italia. Istituto di Ricerca Sulle Acque del Consiglio
Nazionale delle Ricerche, Quaderni, n. 109, (in Italian).
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Lazarova, V. (2003). Drivers and constraints for water reuse development in Europe. In: Proc. of
Seminar and Symposium: Wastewater Reclamation and Reuse, LIFE 99/ENG/GR/000590,
Thessaloniki (Greece), 13-14 February 2003, 65-78.
Maggiore, M., Raspa, G., Sabatelli, L., Santoro, D., Santoro, O. and Vurro, M. (2001). Monitoring of
seawater intrusion in a karst aquifer (Apulia - southern Italy). In: Proc. of the 1st Int. Conf. on
Saltwater Intrusion and Coastal Aquifers - Monitoring, Modeling, and Management. Essaouira
(Morocco), 23–25 April 2001.
Pollice, A., Lopez, A., Laera, G., Rubino, P. and Lonigro, A. (2004). Tertiary filtered municipal
wastewater as alternative water source in agriculture: A field investigation in Southern Italy. Sci
Tot. Env., 324, 201-210.
Portoghese, I., Uricchio, V. and Vurro, M. (2005). A GIS tool for hydrogeological water balance
evaluation on a regional scale in semi-arid environments. Computers & Geosciences, 31, 1, 15-27.
Scharf, J.M. (Ed.) (1966). Recommended methods for the microbiological examination of foods.
APHA, 2nd Edition, New York.
Sparks, D.L. (Ed.) (1996). Methods of soil analysis. Part 3: Chemical Methods. Soil Science Society of
America Inc., Madison WI.
Woomer, P.L. (1994). Microbiological and biochemical properties. In: Methods of soil analysis. Part 2.
R.W. Weaver et al., (Eds.), Soil Science Society of America Inc., Madison WI.
189
USE OF SANDS OF THE DUNES LIKE BIOFILTER IN
THE PURIFICATION OF WASTE WATER OF THE TOWN OF OUARGLA
(ALGERIA)
F. Ammour * and M. Messahel**
* Chargée de Cours à l’Ecole Nationale Supérieure de l'Hydraulique (ENSH)
tel / fax : 00 213 25399446 Email: [email protected]
** Professor Ecole Nationale Supérieure de l'Hydraulique (ENSH), Member of the Board of World
Water Council, Member of French Water Academy
Tel : 00 213 63051329 / fax : 00 213 25399446 Email: [email protected]
SUMMARY - In Algeria, on the 50 stations of purification carried out, nearly two third are out of order
and the 15 stations, which are operational, encounter problems. Their operation is seldom in
conformity with the posted performances. This established fact shows the gravity of the situation
when it is known that more than 700 HM3 of wastewater are evacuated annually.
Like the other towns of the country, the town of Ouargla (southern Algerian) knows serious problems
of cleansing in particular since that the station of purification is out of order in 1980.
The alarming situation of the network of cleansing of the Ouargla town put in the obligation the
authorities to create several outlets around the city. However, the rejection of urban effluents without
any preliminary treatment it accentuated the enhancement and the contamination of the water table
on one hand and on the other hand it generated the degradation of the closer palm plantations. This
Oasis knows today a catastrophic ecological situation, which could be the origin of many epidemics.
Facing to cleansing and management of purification stations problems, it’s recommended to involve
other techniques of purification less expensive and simpler to manage in order to protect the public
health and to safeguard the receiving backgrounds. The use of a local material, such as the sand of
the dunes, as biological filter is a promising technique for the purification of the water used in the
Algerian south.
Among many parameters, which condition the purification capacity of those natural techniques it’s
included: their physicochemical characteristics, the quality of water to be treated and the speed of
filtration.
This study made it possible on one hand to determine of the physicochemical characteristics of sand’s
dunes (structure, texture and chemical composition) and to put forward their filtering capacity and on
another hand to evaluate the purification performances of the designed prototype.
Key words: wastewater, Ouargla in Algeria, treatment and techniques of purification, biological filter
INTRODUCTION
In the town of Ouargla, the discharges of wastewater in an anarchistic way and without treatment,
contribute considerably to the contamination of the ground water and the increase in its ascent. In
addition, the state of degradation and out datedness of the station of purification is such as any
rehabilitation is not economically possible. Thus the recourse to other techniques such as biological
filtration, by using a local material, offers a very promising alternative for the cleansing in the area.
SAND FILTERS
The sand filters are natural environments, which can be used as mass filter in the purification of
wastewater, by ensuring a double role: retention of MES and fixing of the biomass, which develops
around the grains.
191
The choice of a filter support rests on the following criteria:
- Important specific Surface, favorable to the bacterial development.
- The granular support must be siliceous, and stable, at weak soluble matter rate.
- The granulometry must be selected in order to provide a sufficient surface to the development of
the bio-film and to avoid the too fast filling of the filter.
BIOFILTRATION
The biological filtration of the wastewater, on granular support and at low speed became a
particularly gravitational process of purification. In addition to the mechanical retention of MES, this
technique allows the biological breakdown of organic, phosphorated and nitrogenized pollution.
On the microbiological level slow filtration constitutes a stage of disinfections, which moreover has
the advantage of retaining well the protozoa and the flagellate unicellular, which can resist
disinfections by chemical agents. In this process, one attends the development of a biological
membrane around the sand grains, in which microscopic algae, bacteria and zooplankton are lodged.
They are extra cellular polymers, synthesized by the micro-organisms, which play the part of
coagulant.
MATERIAL AND METHODS
Choice of the filter background
On the basis of a preliminary study, carried out on several grounds of the area it arises that:
1. The grounds of the palm plantation have a muddy sandy texture. These grounds have a good
permeability and are slightly alkaline. As for salinity, it is very variable in space and the electric
conductivity of the extract of the paste of ground varies between 0,60 and 15,43 mS/cm. Let us
note that salinity is lower than the average for the majority of the intake points, however, 12% of
the analyzed samples have a relatively strong salinity, this is due primarily to the bad drainage,
leading to stagnations of water in the low areas, which receive the excess of irrigation water from
high zones.
2. For sands of dune and rude sands, we can say that they are grounds with fine sand textures and
rude sands, alkaline with a very low salinity and a soluble matter rate which is also weak; these two
grounds which are primarily made up by quartz have a rate exceeding 87% of their composition.
Sand of dunes and rude sands show favorable characteristics as filtering backgrounds. The results
of the qualitative analysis of these two supports are consigned in tables 1 and 2 and fig.1.
Table 1. Physical analysis of the soil
point of
sample
Permeability K
(cm/h)
Density in
(kg/l)
The
coefficient of
uniformity
The
representative
diameter
Mekhadma
15.29 – 42.89
1.57 – 1.60
1.70 – 1.74
-
Ksar
3.52 – 30.80
1.40 – 1.70
1.68 – 1.72
-
Ain Beida
7.16 – 81.13
1.31 – 1.60
2.22 – 2.40
-
Rouissat
6.28 – 18.49
1.45 – 1.60
1.80 – 1.88
-
Sand dune
Ain Beida
7.2 – 12.8
1.56 – 1.60
1.69
0.18
Rude sand
Ain Beida
78.0
1.60 – 1.62
2.40
0.25
Ground
Ground
of Palm
plantation
192
Table 2.Chemical analysis of the soil
Sampling
point
pH
EC (mS/cm)
Insoluble
(%)
CaCO3(%)
Mekhadma
8,16 – 6,23
1,45 – 6,00
86,2 – 84,0
0.03 – 0.16
Ksar
7,53 – 6,27
2,12 –15,43
85,2 – 80,25
0.03 – 0.18
Ain Beida
7,96 – 6,12
0,60 – 5,92
83,2 – 78,9
0.13 – 0.46
Rouissat
7,77 – 6.25
2,59 –11,12
80,2 – 79,0
0.13 – 0.24
Sand dune
Ain Beida
8,53
0,52
87,94
0.87
Coarse sand
Ain Beida
7,80
0,82
94,65
0.87
Ground
Ground of
Palm plantation
The curves of the granulometric analysis, corresponding to the three types of grounds (sand of the
palm plantation, sands dunes and rude sands), are represented in fig. 1.
%
100
90
80
Sable
grossier
70
60
Sable de
dune
Sable de la
palmerie
50
40
30
20
10
0
10
10
1
5
2
0 .1
1
,4 0
0 .01
0,2
0,1 0,08
Fig. 1. Granulometric analysis of soils of the area of Ouargla
For our study we chose the sand of the dunes, which in addition to its availability, presents very
favorable characteristics for its use as filters: its permeability is 7.2 to 12 cm/H, its salinity is very low
(electric conductivity is 0.52 mS/cm), the rate of the insoluble matters is approximately 87% (quartz
compound primarily) and its organic matter is very low (less than 1%). The granulometric analysis
show that it is about a very uniform ground (the dimension of the aggregates varies between 0.3 and
2 mm).
Experimental device
With an aim of studying the performances of sands of the dunes in purification of pre-treated
wastewater, we set up an experimental device consisting of:
1. A water container and flow regulator having a volume of 250 ml.
2. A Plexiglas septic tank, which ensures the anaerobic pre-treatment with the following dimensions:
L1 = 250 mm, L2 = 125 mm H = 165 mm h1=79 mm and H2 =40 mm (Fig. 2).
193
3. A column of PVC filtration of 90 cm height and 24.2 cm in diameter filled from bottom upwards by a
gravel layer of 10 cm and a dune sand layer of 70 cm height. It is posed on an elevated steel
support of 25 cm to allow the recovery of filtered water.
4. A water supply system made up of four pipes in the form of a cross provided with nine small slits
(ф=1.4mm) in order to allow the water supply of the filter in a homogeneous way. The rate of water
supply of the filter is 2.6 l/day.
During this study (138 days), we followed the purification performances of each work and
determined the total output.
CROSS
SIGHT IN PLAN
H2
h1
H
L1
L2
Fig. 2. Dimensions of a septic tank
RESULTS AND DISCUSSION
After four days of operation (lasted of maturation of the filter) we carried out analyses of raw water,
pretreated water (entry of the filter) and water filtered (exit of the filter) at various periods. The results
obtained are gathered in Tables 3, 4 and 5.
We note an increase in salinity at the exit of the septic tank, which could be attributed to the
phenomena of re-releasing.
On the outlet side of the filter, the increase in salinity is very important during the first five days,
which could be explained by the scrubbing of the salts contained in sand. This increase is stabilized
and become less important for the other sampling campaigns.
The evolution of the pH on the outlet side of the filter shows a light fall during the first 4 samples
then increases for all the other samples. This is explained by a more intense algal development,
therefore a strong consumption of CO2, which results in a rise in the pH.
The degradation of the organic matter was illustrated by the decrease rates of the DBO5 and the
DOC in septic tank. The sand filter and all the installation allowed us to release the following
observations:
• The reduction in the DBO5 was remarkable; it reaches a best performance in the septic tank after
38 days.
• The output knew stabilization with a value exceeding 50 %. The temperature of the study area and
the quality of wastewater justifies this increase in the output.
• After filtration the rate of abatement varies from 47 to 88.5 % and reached its maximum after 65
days.
• The purification performances of the installation exceeds 62%, with a maximum of 97%, at the end
of 65 days of operation.
The abatements obtained on the DOC were also very interesting: with a range varying from 24.3%
to 75.6%, for the septic tank, 55.8% to 89.3% for the filter and 69.6% to 96.2% for all the installation.
194
The outputs obtained are very encouraging and seem justified by the temperature of the area and
the quality of wastewater.
Table 3. Physicochemical parameters’ analysis
Number
of days T °C
N°
Dates
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
10.08.99
17.08.99
29.08.99
05.09.99
12.09.99
19.09.99
26.09.99
09.10.99
17.10.99
30.10.99
13.11.99
20.11.99
29.11.99
04.12.99
12.12.99
21.12.99
5
12
24
31
38
45
52
65
72
86
100
107
116
121
129
138
30
33
32
30
30
29
27
26
28
26
25
23
19
18
20
16
pH
Raw
water
7.48
7.11
7.37
7.43
6.31
7.42
7.44
6.93
7.23
7.11
6.44
6.81
7.22
6.88
7.38
6.72
EC (mS/cm)
Raw
Pretreated Filtered
water
water
water
7.80
7.50
7.77
7.93
7.72
7.91
8.00
7.80
7.50
7.40
6.71
7.31
7.43
6.99
7.30
7.38
8.07
7.42
7.65
7.44
7.76
8.10
7.98
8.10
8.21
8.10
8.14
8.16
8.31
8.36
8.34
8.30
2.60
2.80
2.70
2.80
2.70
2.70
2.80
2.70
2.70
2.60
2.50
2.70
2.30
2.80
2.60
2.50
Pretreated Filtered
water
water
5.40
4.30
3.00
3.10
3.10
2.80
2.90
2.70
2.70
2.70
2.80
2.80
2.30
2.60
2.70
2.60
13.40
5.20
4.20
3.90
4.00
3.80
3.80
3.60
3.40
3.30
3.30
3.60
3.20
3.30
3.40
3.10
Table 4. Results of analysis of the DBO5
N°
Number
of days
1
2
3
4
5
6
7
8
9
10
11
12
13
14
5
12
24
31
38
45
52
65
86
100
116
121
129
138
Raw
water
430.00
450.00
410.00
330.00
580.00
460.00
260.00
500.00
580.00
580.00
480.00
260.00
400.00
300.00
DBO5 Mg/L
Pretreated
water
360.00
320.00
240.00
180.00
160.00
140.00
70.00
130.00
260.00
270.00
220.00
110.00
180.00
140.00
Filtered
water
160.00
170.00
120.00
80.00
40.00
30.00
15.00
15.00
50.00
65.00
60.00
30.00
55.00
45.00
Septic tank
Output
16.28
28.89
41.46
45.45
72.41
69.57
73.08
74.00
55.17
53.45
54.17
57.69
55.00
53.33
Output %
Filtration
Output
55.56
46.88
50.00
55.56
75.00
78.57
78.57
88.46
80.77
75.93
72.73
72.73
69.44
67.86
Total output
62.79
62.22
70.73
75.76
93.10
93.48
94.23
97.00
91.38
88.79
87.50
88.46
86.25
85.00
195
Table 5.Results of analysis of the DCO
Number
of days
1
2
3
4
5
6
7
9
10
11
12
13
14
15
16
17
5
12
24
31
38
45
52
65
72
86
100
107
116
121
129
138
Rendement
N°
Rough
water
826.00
1200.00
1104.00
768.00
998.00
1286.00
739.00
989.00
952.00
749.00
768.00
624.00
1536.00
634.00
1498.00
1382.00
DCO Mg/L
Pretreated
water
538.00
826.00
836.00
442.00
394.00
538.00
259.00
355.00
307.00
346.00
365.00
260.00
614.40
211.00
365.00
461.00
Filtered
water
230.00
365.00
288.00
154.00
67.00
86.00
29.00
38.00
58.00
86.00
106.00
77.00
192.00
76.80
144.00
154.00
Septic tank
Output
34.87
31.17
24.28
42.45
60.52
58.16
64.95
64.11
67.75
53.81
52.47
58.33
60.00
66.72
75.63
66.64
Outputs %
Filtration
Output
57.25
55.81
65.55
65.16
82.99
84.01
88.80
89.30
81.11
75.14
70.96
70.38
68.75
63.60
60.55
66.59
Total output
72.15
69.58
73.91
79.95
93.29
93.31
96.08
96.16
93.91
88.52
86.20
87.66
87.50
87.89
90.39
88.86
1 2 0 ,0 0
1 0 0 ,0 0
8 0 ,0 0
6 0 ,0 0
4 0 ,0 0
2 0 ,0 0
0 ,0 0
0
50
100
150
Jo u rs
Rendement
F o s s e S é p t iq u e
Rendement
f ilt r a t io n
Rendement
g lo b a le
Fig. 3. Evolution of the abatement of the DBO5 according to the time at the exit of each work.
196
Rendement
1 2 0,0 0
1 0 0,0 0
8 0,0 0
6 0,0 0
4 0,0 0
2 0,0 0
Re n d e me n t
Fo s s e S é p tiq u e
0,0 0
0
50
100
1 50
Re n d e me n t
Filtr a tio n
Jo u r s
Re n d e me n t
g lo b a l
Fig. 4. Evolution of the abatement of the DOC according to the time at the exit of each work.
CONCLUSION
It comes out from this study that the use of sands of dune makes it possible to solve the problem
of the water used without recourse to very expensive techniques, which require very important means
of management.
The physicochemical and granulometric characterization showed that they are very uniform
grounds, with sandy texture, primarily of quartz; they are not very saline and at weak rate of limestone
and organic matter.
Results obtained on the abatement of the DBO5 and DOC show the effectiveness of this technique
in the degradation of the organic matter. However, to justify the choice of this technique, it is
necessary to carry out an experimental site to reduce the errors of scale and to take into account the
other parameters of pollution that was not studied in this work (MES, nitrogenized, phosphorated
Pollution and bacteriological quality).
REFERENCES
Adoun, M.S. (1988). Les procédés d’alimentation en eau et d’assainissement urbain. Maison Errate
universitaire, Caire, Egypte (en Arabe).
CNERIB, (1993). Centre national d’étude et de recherche intégrées du bâtiment. Assainissement
autonome et semi collectif.
Edile inf, (1996). Bulletin international de l’eau et de l’environnement N°11.
Gougoussi, C. (1979). Assainissement individuel et aptitude du sol à l’élimination et à l’épuration des
effluents domestiques. Thèse 3éme cycle, Institut National Polytechnique de Lorraine ;
Hadjar, S. (1994). Traitement des eaux potables Haleb SERIE (en Arabe).
Memonto technique de l’eau ; Degrement ; 1989
Normalisation française. Mise en œuvre des dispositifs d’assainissement autonome ; AFNOR ; 1992.
OMS (1984). Guide pratique pour l’eau et l’assainissement rurale et suburbain, Copenhague
197
SALMONELLA TRANSPORT AND PERSISTENCE IN SOIL AND PLANT
IRRIGATED WITH ARTIFICIALLY INOCULATED RECLAIMED WATER:
CLIMATIC EFFECTS
M.P. Palacios *, P. Lupiola ** F. Fernandez-Vera ***, V. Mendoza * and M.T. Tejedor **
*Agronomía Fac Veterinaria. Universidad de Las Palmas de Gran Canaria [email protected]
**Microbiología. Fac Veterinaria. ULPGC. 35416 Autovia Las Palmas Arucas km 6.5
***Granja Agrícola Experimental Cabildo de Gran Canaria 35416 Autovia Las Palmas Arucas km 6.5
SUMMARY - The acceptability of reclaimed water to replace other resources for irrigation is
dependent on whether the health risk and environmental impacts entailed are acceptable or not.
Secondary effluent chlorination is extended but there are incidences in which Salmonella survive
contaminating reclaimed water ponds. Specific site conditions influence pathogens existence and
persistence. The aim of the experiments was to increase the scientific information on the climatic and
soil effects on pathogens transport and survive under agricultural conditions.
Results from three experiments are presented here. Five pots were irrigated using a secondary
effluent artificially inoculated with Salmonella. To study the effect of competence with soil bacteria,
plates with sterilized soil were also tested. Radiation effect was also studied by blocking UV light.
Stems and leaves, three different soil depths (surface, 0.15 and 0.45 m) and plates were sampled. As
result of the radiation effect, less bacterial counts on plant were obtained during the day. But during
the night Salmonella was able to re-grow, depending on the nocturnal temperatures. After 3 weeks in
the field, Salmonella was still detected in plant samples. Radiation caused Salmonella death in soil
samples in spring while natural soil bacteria competence was the main factor affecting in autumn. Soil
was able to filtrate Salmonella, but preferential flux transported bacteria to 0.45m depth, surviving 3
weeks. Soil physical properties, irrigation system and water management will have an effect on the
sanitary risk associated to reclaimed water irrigation. In this sense, SDI must be considered as the
safest irrigation method.
Key word: Salmonella, survival, radiation, reclaimed water, soil
RESUME - L’acceptabilité des eaux dépurées sur d’autres sources d’eau pour l’irrigation dépend de
l’impact sur l’environnement et des risques sanitaires. En ce qui concerne ces derniers, les conditions
spécifiques du site de réutilisation influence l’existence et persistance des pathogènes, l’information
de la littérature scientifique à ce sujet étant contradictoire. La chloration lors du traitement de l’eau est
très étendue mais il y a des évidences sur la survivance de Salmonella. L’objectif de ce travail est de
contribuer à la connaissance de l’effet du climat et des sols sur la transport et la survivance de
Salmonella dans des conditions de terrain en culture. On présente les résultats de trois expériences.
Cinq pots semés de Medicago sativa furent irrigués avec un effluent secondaire inoculé de
Salmonella. Les paramètres climatiques furent registrés avec une station climatique automatique. Les
tiges et les feuilles, ainsi que les sols à trois profondeurs (surface, 0.15 et 0.45 m) furent
échantillonnés. Comme résultat de la radiation, le nombre de bactéries décru pendant le jour, tandis
que pendant la nuit une re-croissance se produit, spécialement dans l’expérience du printemps.
Après trois semaines sur le terrain, on pouvait détecter la Salmonella dans les échantillons végétaux.
La radiation semble être la cause de la mort de Salmonella dans les sols au printemps tandis que la
compétence biotique pourrait être le facteur principal en automne. Le sol est capable de filtrer la
Salmonella, mais à travers le flux préférentiel, elle peut atteindre le sous-sol (0.45 m de profondeur)
où elle peut survivre au moins trois semaines.
Mots Clés: Salmonella, survivance, radiation, eau dépurée, sol
199
INTRODUCTION
Municipal reclaimed water, as a non-conventional resource, can increase the sustainability of
agricultural production mainly in arid and semiarid countries. Specific site conditions influence
pathogens existence and persistence in agricultural lands (Guan and Holley, 2003). Water and soil
characteristics, irrigation systems and water management (Sivapalasingam, 2003), crops, animal and
human exposure affect so much the risk associated with water reuse that no quality standards are
universally accepted (WHO, 1989 and 2000, Pescod, 1992, Westcot, 1997, Blumenthal et al., 2000,
ANZECC, 2000, Carr et al., 2004, USEPA, 2004) and sometimes contradictory information in the
scientific literature is found based on the proposed criteria: risk assessment or sustainability criteria
(Jensen et al., 2001). Finally, the climatic effect on pathogen persistence or attenuation must be also
considered. Thus, acceptability of reclaimed water to replace other water resources for irrigation is
highly dependent on whether the health risk and environmental impacts entailed (Pedersen et al.,
2005) are acceptable or not (Angelakis et al., 1999). There is a lack of regulatory standards in Europe
regarding reclaimed or “regenerated” water reuse. In fact, nowadays in Spain there is not reuse
regulations at all.
Total count and species of microorganisms founded in wastewater widely varies due to climate
conditions, season, population sanitary habits and diseases incidence. The use of many bacteria
indicators is extended, but only limited species of them are pathogens. Salmonella is one of the
pathogenic bacteria most frequently associated with water caused illness (Fernández-Crehuet y
Espigares, 1995; Fett and Cooke, 2003; Brooks et al., 2003; Estrada-Garcia et al., 2004). Although
chlorination is widely extended, there are situations in which coli forms, Salmonella and other
heterotrophic bacteria are able to survive (Al-Nakshabandi et al., 1997; Snelling et al., 2006)
especially in rural communities with low cost water treatment plants (Hernandez Moreno and
Palacios, 2006). In this sense, Tejedor et al. (1998) detected the rare presence of Salmonella in
chlorinated reclaimed water in agricultural field lands. That presence coincided with seldom high
DBO5 values of the secondary effluent measured in the reclaimed water treatment plant. Salmonella
lives in gastrointestinal habitat. Thus, it is widely accepted that it has a limited survival period in
environmental conditions. Despite of this, high nutrient contents of agricultural soils (especially when
irrigated using reclaimed water) and favourable temperature and humidity conditions (frequent in
irrigated lands from semiarid countries) have been mentioned as a suitable environment for
pathogenic bacteria (Byappanahalli and Fujioka, 1998). In this sense, pathogenic bacteria have been
previously cited as able to persist in water, soils and on crops (Batarsseh, et al. 1989a,b, Hassen et
al., 1996), agreeing with our results showing that Salmonella is able to survive in reclaimed water
ponds for periods longer than one month (Tejedor-Junco et al., 2005) in subtropical climates.
The establishment of Macaronesian quality guidelines for reclaimed water (RW) reuse envisages:
(i) Developing a single set of guidelines and criteria that are appropriate for Macaronesia and that are
based on a consensus of Macaronesia expert and other role players in water quality, and (ii) Adapting
national/international guidelines in the light of local research and experience (Palacios and
Hernandez- Moreno, 2005). Thus, the aim of this experiment was to increase the scientific information
on the climatic and soil effects on pathogen transport and survive under agricultural field conditions, in
order to improve local knowledge and to establish the best reclaimed water management practices
from health, environmental and economical point of view.
MATERIALS AND METHODS
Analysing the results of two previous assays that were carried out during autumn and spring
(Palacios et al., 2001) we decided to conduct a third experiment. In this experiment we increased the
frequency of sampling to demonstrate our hypothesis. Thus, the results from this third experiment
carried out during the following autumn are presented here. Detailed material and methods are
presented in mentioned paper. Five pots (0.8 m height and 0.9 m in diameter) were placed in the
experimental field, filled with local soil 9 months before the first experiment and seeded with Medicago
sativa. Two pots were irrigated using a secondary effluent in each experiment: one artificially
inoculated and the second one without Salmonella (control). One control pot from the first experiment
was reused for the third. Main soil characteristics were: clay soil (47% of expansive clay), 1.1% of
organic matter, 1.8 dS/m of electrical conductivity, 38 and 83 mg/kg of nitrates and Olsen
phosphorous and 4.36 me/100 g of potassium. An Automatic Weather Station recorded climatic
200
parameters. The reclaimed water were artificially inoculated with a known Salmonella biotype and
serotype with (124±8)·103 (first experiment) (565±85)·103 (second) and (412±73)·103 (third) cfu·mL-1.
Reclaimed water samples were collected in sterilized bottles before inoculation and were analysed for
Salmonella presence. Soil and plant samples were also analysed before each experiment.
Composite plot soil samples were taken from soil surface, 0.15m and 0.45m depth, after different
periods in each experiment: 2, 7 and 12 days after irrigation (first experiment); 22, 46, 166, 310 and
358 hours after irrigation (second experiment) and every two hours from sunrise to sundown during 3
days, 10 and 20 days after irrigation from the soil surface. For 0.15 and 0.45m soil a sample was
taken 1, 2, 3, 10 and 20 days before irrigation (third experiment). Open plates (filled with sterilized
soil) and ultra violet radiation isolated plates (filled with non sterilized soil) were sited on the two plots
surface in the second and third experiments. Every plate was irrigated using the same quality of water
than used to irrigate each plot using higher counts ((5±1.5)·106.cfu·mL-1) for the third experiment.
Composite plant samples were collected in each plot: 0, 1 and 2 days after irrigation during the first
experiment, 0, 3.5, 11, 22, 46, 166 and 214 hours after irrigation (second one) and using the same
frequency for sampling as described by the surface of the soil (third one).
Salmonella count was determined using Brillant Green and Rapport Agar plates incubated at
43 ºC. Plant and soil samples (25g) were diluted in 225mL peptone buffered water with increasing
dilution values. Thus, the results are presented in cfu·mL-1. Presence test were also made in all the
samples for the second and third experiments. More detailed procedures, which were already
described for second experiment, are presented in Palacios et al., 2001.
RESULTS AND DISCUSSION
Salmonella ausence was found in all the water, soil and plant samples before the experiments.
Likewise, Salmonella ausence and non detectable counts were found in every soil and plant samples
irrigated with non inoculated water (control) during the experiments.
Results of Salmonella counts for the third experiment in plots irrigated with inoculated reclaimed
water are shown in Fig. 1. Plant data from the first and the second experiment are also represented.
10000000
1000000
cfu/mL
100000
10000
1000
100
10
time
1
12:00
a.m.
6:00 a.m.
12:00
p.m.
6:00 p.m.
12:00
a.m.
6:00 a.m.
12:00
p.m.
6:00 p.m.
12:00
a.m.
6:00 a.m.
12:00
p.m.
6:00 p.m.
plant (3rd exp)
soil:surface (3rd exp)
soil:0.15m (3rd exp)
soil:0.45m (3rd exp)
plant (1st exp)
plant (2nd exp)
12:00
a.m.
Fig. 1. Results of Salmonella counts obtained during the third experiment (November), in cfu·mL-1
(Artificially inoculated reclaimed water: (565±85)·103 cfu·mL-1 (second experiment) and
(412±73)·103 cfu·mL-1 (third one) for soil and plant samples).
As result of the solar radiation effect, less bacteria counts were progressively obtained on plant
(continuous line with lozenges in Fig. 1) over time during the day. In fact, since the first day following
irrigation, some no detectable counts were obtained due to the presence of many environmental
bacteria growing in the laboratory plates that difficult the detection of Salmonella, although presence
201
test detected it. These results were also obtained by the second experiment and are coincident with
obtained by other authors (Turpin et al, 1993). In order to represent these detectable but not
countable results, it was decided to assign them the value three.
During the night, Salmonella was able to grow although for 5 and 4 log(10) cfu·mL declines in the
population organisms in plant samples from initially inoculated and from the first night population at
field conditions respectively. These results were consistent for at least three days and for the three
experiments demonstrating the solar radiation effect in bacterial death growing on the plant surfaces.
Higher recovering was obtained during the spring nights of the 2nd experiment, probably due to the
higher nocturnal temperatures (also affected by soil heat emission), from this season. Salmonella was
detected for the 10 and 20 days before irrigation (3 and (9·103) cfu·mL-1, respectively). This result
coincides with obtained by Ronconi et al., (2002) who demonstrated the persistence of E Coli in
lettuces. Similarly, Guo et al., (2001) detected persistence of Salmonella in tomato plants and fruits
over a longer period of time following inoculation at field conditions.
Comparing plant and soil results we noticed that bacteria survival was higher on the soil surface
than on the plant samples. Although as occurred in plant samples an initial declination in bacterial
populations was obtained from the sunrise to the noon, bacteria mortality was low and it was able to
recover high populations even during the day. It is probably due to the solar radiation attenuation
caused by plant and soil particles shading. Results obtained in subsoil samples (at 0.15 and 0.45m
triangles and stripes in fig 1) are coincident with obtained in plant samples. Soil was able to effectively
filtrate Salmonella, decreasing its population in 2 log (10) cfu·mL for the second day, but preferential
flux may let the bacteria to reach subsoil at 0.45 depths. As obtained for the second experiment
Salmonella seemed to need one day after irrigation to reach this depth. But, once in subsoil, it was
able to survive at least 3 weeks in subtropical climates. This result is consistent which obtained by
other authors (Ibenyassine et al., 2006).
Fig. 2 represents the results for the comparative study from the effect of Salmonella competence
with soil bacteria to radiation. Filled lozenges and discontinuous line represent sterilized soil plates
results with lozenges for the 2nd and 3rd experiments respectively, while ultra violet radiation blocked
plates (filled with non sterilized soil) are represented by addition signs and continuous line with
asterisks (2nd and 3rd experiments respectively). Radiation seems to be the main cause of Salmonella
death in soil samples during the spring season (2nd experiment, with spring longer day duration) while
natural soil bacteria competence could be the main factor affecting in autumn (3rd experiment),
coinciding with Turpin et al. (1993). Hence, the season effect could explain contradictory results
obtained by many authors. As latitude condition day duration too, the conclusions obtained with local
survival studies have not to forget this factor. You et al. (2006) also founded higher Salmonella
persistence when manure is applied to sterilized soil comparing to no sterilized one.
100000000
10000000
cfu/mL
1000000
100000
10000
1000
100
10
time
1
12:00 AM
6:00 AM
12:00 PM
soil:surface (3rd exp)
sterilized soil plates
uv blocked plates (2nd exp)
6:00 PM
12:00 AM
6:00 AM
12:00 PM
soil:0.15m (3rd exp)
uv blocked plates
6:00 PM
12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
soil:0.45m (3rd exp)
sterilized soil plates 2nd exp)
Fig. 2. Results of Salmonella counts obtained during the second (spring) and the third (autumn)
experiments, in cfu·mL-1 (Artificially inoculated reclaimed water: (412±73)·103 cfu·mL-1 for soil
samples and (565±85)·103) cfu·mL-1 for plates.
202
In the 3rd experiment, and when soil bacteria competence was eliminated, even an increase of 1
log (10) cfu·mL was measured during the first two days after irrigation. This result coincided with
obtained by You et al. (2006) who founded a Salmonella concentrations increase by up to 400% in
the first 1 to 3 days after inoculation following by a steady decline. Once again, the solar radiation
attenuation caused by plant and soil particles shading, joined to competence elimination could explain
this increment in Salmonella populations. Comparing the results obtained by surface soil and plates
with subsurface soil (triangles and stripes, fig 2), and considering results obtained by Al-Nakshabandi
et al. (1997) and Batarsseh, et al. (1989a,b) we concluded that soil bacteria “filtration” was the main
factor to decrease pathogen risk associated with reclaimed water irrigation. Complex transport
behavior other than advection-dispersion, simple retardation and first order removal has been
observed in many biocolloid transport experiments in porous media (Cortis, et al., 2006). Colloid
transport in subsurface environments is critical to solving problems related to groundwater pollution by
microbial pathogens (Saiers and Ryan, 2006). In this sense, subsurface drip irrigation systems (SDI)
must be considered as the safer way to reuse reclaimed water. Contradictory results were obtained
by Assadian et al., (2005) who concluded that preferential flow of irrigation water to the surface of
clayey soil columns promoted virus movement to the soil surface when using SDI. In spite of this,
many authors mentioned that associated with increasing irrigation frequency (comparing drip and
furrow irrigation) less vertical cracking clay was observed (Hodgson et al., 2005). This second
experiment was carried out at field conditions, while Assadian et al. worked in soil columns.
CONCLUSION
High Salmonella levels artificially inoculated, higher than may be expected in any reclaimed water
used for irrigation, were used in these studies. Analysing the results obtained by this 3rd experiment
we are now able to demonstrate our previous hypothesis: Salmonella was able to survive at least 3
weeks on plant, surface and subsurface soil samples at field conditions in subtropical climates. Soil
was able to effectively filtrate Salmonella, but preferential flux may let the bacteria reach subsoil at
0.45m depth. Due to this fact, soil physical properties, irrigation system and water management will
have an effect on the sanitary risk associated to reclaimed water irrigation. In this sense, SDI must be
considered as the safest irrigation method. The solar radiation declined pathogen’s populations from
initially inoculated on plant and soil surface during the day. In spite of this, during the night Salmonella
was able to re-grow, basically depending on the nocturnal temperatures, also affected by the soil heat
emission. Radiation was the main cause of Salmonella death in soil samples in spring while natural
soil bacteria competence was the main factor affecting in autumn, when the solar radiation
attenuation caused by plant and soil particles shading seemed to be a critical factor.
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