WATER SUPPLY IN TANZANIA
AND PERFORMANCE OF LOCAL
PLANT MATERIALS IN
PURIFICATION OF TURBID
WATER
Nancy Jotham Mwaisumo Marobhe
June 2008
TRITA-LWR PhD Thesis 1042
ISSN 1650-8602
ISRN KTH/LWR/PHD 1042-SE
ISBN 978-91-7415-016-2
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
© Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Doctoral Thesis
Department of Land and Water Resources Engineering
Royal Institute of Technology (KTH)
SE-100 44 STOCKHOLM, Sweden
ii
Water supply in Tanzania and performance of local plant materials in purification of turbid water
DEDICATION
To Isaac, Emmanuel, Mutaju, Tusajigwe and Obed
Gen. 18:14. Is anything too hard for the Lord? Hymn 11. I need you the every hour.
Mwa. 18:14. Kuna neno gani lililo gumu la kumshinda Bwana? Tenzi 11. Nina haja nawe kila saa.
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Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
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Water supply in Tanzania and performance of local plant materials in purification of turbid water
A CKNOWLEDGEMENTS
I would like to express my sincere gratitude to Sida/SAREC for financial support, which has
made this research possible and has contributed significantly to building human and non-human
resource capacity at Ardhi University (ARU). I greatly appreciate the coordination and support of
Prof. Dick Urban Vestbro that contributed greatly to the success of PhD studies at ARU and
KTH.
I wish to extend profound gratitude to my main supervisor, Associate Professor Gunno Renman, for his scientific guidance and constructive inputs to my research. Without his tireless support and encouragement, I could not have accomplished this research. I also appreciate the
kindness and willingness of his entire family to assist, especially in times of difficulty. My special
thanks go to my co-supervisors Associate Professor Gunnar Jacks and Professor Jackson Msafiri
for their scientific guidance, valuable discussions and support.
I am deeply indebted to Dr. Gunaratna Rajarao for her close supervision in purification and
characterisation of the seed proteins and Professor Gunnel Dalhammar for her great interest in
my study subject and for providing facilities and materials used for protein and bacterial studies.
Their scientific inputs into my research activities have greatly contributed to the success of my
studies.
My gratitude also goes to EE academic staff members, Dr. Kiunsi R, Dr. Mgana S, Prof. Kassenga G.R and Prof. Kaseva M.E to mention a few, for fruitful discussions and comments during
the preparation of some manuscripts. My sincere thanks go fellow PhD candidates at the Department of LWR and Applied Environmental Microbiology at KTH for their wonderful hospitality and friendship. Special thanks to Sofia, Kay and Per for tireless assistance in the lab. The
encouragement and support of my fellow PhD students from ARU (Merdard, Charles, Felician,
Prosper, Tatu, Stanlaus and Boniface) are highly appreciated. Thank you Aira and Britt for the
wonderful assistance in administrative as well as social matters.
My special thanks go to the leadership in Singida Rural District, the local leadership and villagers
in Ilongero Division for their cooperation and assistance during my fieldwork studies in the
district. I am also indebted to the District water engineer, Eng. Luanda, J.F, Mr. Shekiondo, H.M,
and other staff members at the water department in Singida district for their support during my
fieldwork and assistance in analysis of water samples. I would be delighted to see villagers manage to transform muddy water into clear and bacteriologically safe drinking water and also manage to improve their income and hence afford to operate and maintain potable water sources.
My heartfelt thanks go to my late parents, Mzee Jotham Obed Mwaisumo and mama Andekile
Anna Ilomo, without whose wisdom and love I could not have been as I am today. The moral
and spiritual support and great love of my beloved sisters, brothers, aunts, cousins and nephews,
my sisters and brothers in law, my mother in law, Nyabhele Rukia Mutaju and other relatives are
highly appreciated. My very special thanks go to my husband and best friend, Isaac, for his
boundless enthusiasm for my studies. His great love, encouragement and spiritual support and
paving a way towards my academic achievement is highly appreciated. I sincerely appreciate the
effort, time and skills he used in taking care of family in my absence. My special thanks go to my
children, Emmanuel-Nyarugere, Mutaju-Ipyana, Tusajigwe-Gloria and Obed-Baraka, for their
understanding, patience and moral support during the whole period of my studies. My aunt Laida
Kasuga, I thank you so much for your love, caring and faithfulness to our family, may God bless
you and reward you accordingly.
Finally, above all, I thank the Lord for all he has done, is doing and will do in and through me.
Nancy Jotham Mwaisumo Marobhe
Stockholm, June 2008
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Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
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Water supply in Tanzania and performance of local plant materials in purification of turbid water
LIST OF PAPERS APPENDED
I.
II.
III.
IV.
V.
VI.
Marobhe, J.N. 2008. Critical review of water supply services in urban and rural areas of
Tanzania. Water Policy, 10(1), 57-71. doi:2166/wp.2007.029.
Marobhe, N.J., Renman, G., Gunnar, J. 2007. The study of water supply and traditional
water purification knowledge in selected rural villages in Tanzania. In: Indigenous knowledge systems and sustainable development: Relevance for Africa. Boon E. and Hens, L
(eds). Kamla-Raj Enterprises, Delhi, Indian. Tribes and Tribals, Special Volume No. 1, 111120.
Marobhe, N.J., Renman, G., Jackson, M. 2007. Investigation on the performance of local
plant materials for coagulation of turbid river water. Institution of Engineers Tanzania, 8
(3), 50-62.
IV.Marobhe, N.J., Dalhammar, G., Gunaratna, K.R. 2007. Simple and rapid method for
purification and characterization of active coagulants from the seeds of Vigna unguiculata
and Parkinsonia aculeata. Environmental Technology, 28, 671-681.
V.Marobhe, N.J., Dalhammar, G., Gunaratna, K.R., 2008. Effect of coagulant protein
from Vigna and Parkinsonia on bacteria isolated from Ruvu River in Tanzania (Submitted to
the World Journal of Microbiology and Biotechnology on 15 March 2008).
Marobhe, N.J., Renman, G., Msafiri, J., Mgana S. 2008. Purification of water from small
man-made reservoirs by coagulation using purified proteins from Vigna and Parkinsonia
seeds (Submitted to Separation and Purification Technology on 5 March 2008).
Papers are reproduced with permission of the journal concerned
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Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
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Water supply in Tanzania and performance of local plant materials in purification of turbid water
ABBREVIATIONS
CF
CM
DAWASA
DBPs
FC
FTU
GOT
GS
IEX
LBB
mg/L
µS/cm
MO
MOCP
MS
NCIB
NOM
NTU
OD
PACE
PAP
PPT
RPM
RWSSPs
SD
SDS- PAGE
THMs
URT
WHO
WEO
VEO
VUCE
VUP
UV
Citrus fruit juice
Carboxymethyle
Dar es Salaam Water Supply and Sewerage Authority
Disinfection-by Products
Fecal coliforms
Formazin turbidity units
Government of Tanzania
Grain size
Ion exchange
Buffered lauryl broth
milligram per litre
micro siemens per cm, a measure of electrical conductivity (EC)
Moringa oleifera
Moringa oleifera coagulant protein
Mass spectrometry
National Center for Biotechnology Information
Natural organic matter
Nephelometric unit
Optical density
Parkinsonia aculeata crude seed extract
Parkinsonia aculeata protein
Parts per thousand
Revolution per minute
Rural Water Supply and Sanitation Projects
Standard deviation
Sodium dodecyl sulphate-Polyacylamide gel electrophoresis
Trihalomethanes
United Republic of Tanzania
World Health Organisation
Ward Executive Officer
Village Executive Officer
Vigna unguiculata crude seed extract
Vigna unguiculata protein
Ultra violet
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Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
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Water supply in Tanzania and performance of local plant materials in purification of turbid water
TABLE OF CONTENTS
ACKNOWLEDGEMENTS ........................................................................................................................... V
LIST OF PAPERS APPENDED ................................................................................................................ VII
ABBREVIATIONS .......................................................................................................................................IX
TABLE OF CONTENTS .............................................................................................................................XI
ABSTRACT..................................................................................................................................................... 1
1 INTRODUCTION....................................................................................................................................... 1
1.1 Background ...................................................................................................................................................... 1
1.2 Motivation........................................................................................................................................................ 2
1.3 Objectives ........................................................................................................................................................ 3
1.4 Thesis outline ................................................................................................................................................... 3
2 OVERVIEW OF WATER SUPPLY IN DEVELOPING COUNTRIES .................................................... 3
2.1 Urban and rural water supply ........................................................................................................................... 3
3 REVIEW OF CONVENTIONAL SURFACE WATER TREATMENT.................................................... 4
3.1 Coagulation and flocculation............................................................................................................................ 4
3.1.1 Factors affecting coagulation-flocculation...............................................................................................................................5
3.1.2 Health risks associated with chemical coagulation and flocculation........................................................................................6
3.2 Water disinfection and associated health risks.................................................................................................. 6
4 REVIEW OF TRADITIONAL PLANT MATERIALS USED IN WATER TREATMENT ..................... 6
4.1 Traditional natural coagulants .......................................................................................................................... 6
4.1.1 Performance of natural coagulants ........................................................................................................................................7
4.4 Natural plant materials for water treatment in Tanzania .................................................................................. 8
4.4.1 Parkinsonia aculeata ...........................................................................................................................................................8
4.4.2 Vigna unguiculata...............................................................................................................................................................9
4.4.3 Voandzeia subterranea........................................................................................................................................................9
4.4.4 Citrus aurantifolia...............................................................................................................................................................9
5 MATERIALS AND METHODS ................................................................................................................. 9
5.1 Urban and rural water supply in Tanzania ........................................................................................................ 9
5.2 Coagulation experiments under varying physical parameters (Paper III)....................................................... 10
5.2.1 Source of seeds and their chemical composition ....................................................................................................................10
5.2.2 Preparation of seed powder and crude seed extracts.............................................................................................................10
5.2.3 Source of water samples......................................................................................................................................................11
5.2.4 Experimental and analytical procedures.............................................................................................................................11
5.3 Purification and characterisation of active coagulant proteins (Paper IV) ...................................................... 11
5.3.2 Characterisation and analytical procedures .........................................................................................................................11
5.3.2.1 SDS-PAGE Electrophoresis.........................................................................................................................................11
5.4 Antimicrobial effect (Paper V) ...................................................................................................................... 12
5.4.1 Bacterial isolation and identification...................................................................................................................................12
5.4.2 Flocculation and growth inhibition .....................................................................................................................................12
5.5.1 Sampling of charco dam water and coagulation experiments ...............................................................................................12
5.5.2 Analytical methods ............................................................................................................................................................13
6 RESULTS AND DISCUSSION ..................................................................................................................13
6.1 Review of urban and rural water supply services in Tanzania (Paper I).......................................................... 13
6.1.1 Urban water supply: The case of Dar es Salaam city .........................................................................................................13
6.1.2 Rural water supply: The case of Singida rural district ........................................................................................................15
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Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
6.2.1 Water supply sources..........................................................................................................................................................16
6.2.2 Traditional water coagulation: Procedures and performances...............................................................................................17
6.3 Effect of varying physical parameters on coagulation of river water with crude seed extracts (Paper III)...... 18
6.3.1 Optimum dosage and seed powder grain size effect ..............................................................................................................18
6.3.2 Effect of raw water pH.....................................................................................................................................................19
6.3.3 Mixing speed and duration ................................................................................................................................................20
6.4 Purification and characterisation of coagulant proteins (Paper IV) ................................................................ 21
6.4.1 Protein purification ............................................................................................................................................................21
6.4.2 Characterisation ................................................................................................................................................................22
6.5 Antimicrobial activity on tropical river water bacteria (Paper V).................................................................... 27
6.6 Physico-chemical quality (Paper VI)............................................................................................................... 29
7 CONCLUSIONS AND RECOMMENDATIONS.................................................................................... 30
8 AREAS FOR FURTHER RESEARCH ......................................................................................................31
9 REFERENCES.......................................................................................................................................... 32
xii
Water supply in Tanzania and performance of local plant materials in purification of turbid water
A BSTRACT
Water supply services in urban and rural areas of Tanzania were reviewed and specific studies
were carried out on water supply and on purification of turbid water sources using locally available plant materials in rural villages of Singida Rural District. The review showed that large proportions of urban and rural populations in Tanzania face acute water supply problems mainly due
to poor planning, implementation and management of water supply projects, including an inability to address social, technical, operation and maintenance and financial issues. Laboratory-scale
experiments studied the effectiveness of crude seed extracts (CSEs) and purified proteins of
Vigna unguiculata (VUP), Parkinsonia aculeata (PAP) and Voandzeia subterranea (VS) seeds, which are
used traditionally for clarification of turbid water. The VUP and PAP were purified from CSEs
using simple and straightforward two-step ion exchange chromatography. The coagulant proteins
are thermoresistant and have a wide pH range for coagulation activity. Coagulation of turbid
waters with CSEs, VUP and PAP produced low sludge volumes and removed turbidity along
with other inorganic contaminants in line with Tanzania drinking water quality standards. The
PAP also showed antimicrobial effect against river water bacteria. Citrus fruit juice (CF) enhanced the coagulation of turbid water by CSEs and inhibited bacterial growth, rendering it
useful for disinfection of water prior to drinking in rural areas. It was concluded that natural
coagulants should not be regarded as a panacea for rural water supply problems, but rather a tool
in the development of sustainable water supply services in Tanzania.
Keywords: Antibacterial effect; Coagulant proteins; Vigna unguiculata; Parkinsonia aculeata; Ion exchange; Tanzania water supply
1 INTRODUCTION
are either unimproved, such as unprotected
wells, unprotected springs and rivers, or
improved such as protected wells, boreholes
and public standpipes (WHO & UNICEF,
2000a). In most cases the improved communal sources are malfunctioning or completely broken down due to poor operation
and maintenance, financial constraints, poor
project planning and inefficient management
systems (Howard & Bartram, 2005; Mugabi
et al., 2007a). Due to chronic problems
associated with improved water supply such
as the cost (both financial and time required
to collect water), the quality and the reliability of the supply, large populations in developing countries, especially in rural areas, are
forced to use traditional sources that are
polluted.
Given the time and costs of developing or
rehabilitating improved communal water
supply sources, it can be cost-effective in
certain circumstances to rely on existing
traditional sources (Clasen & Bastable,
2003). This is possible if traditional water
sources can be treated using water purification methods, which are inexpensive and
suitable under local conditions. One method
1.1 Background
Despite widespread recognition of the
importance of improved water and sanitation and heavy investment by international
donors and governments in developing
countries in extending water supply systems,
more than half the population of rural areas
still lack access to clean drinking water
(Rondinelli, 1991). The rapid pace of urbanisation in developing countries is also increasing the demand for water in peri-urban
communities and cities. Contaminated
drinking water and inadequate supplies of
water for personal hygiene and poor sanitation are responsible for about 4 billion cases
of diarrhoea each year that cause 2.2 million
deaths, mostly among children under the age
of five (WHO, 2000a; WHO, 2003). The
deaths from water-borne and water-washed
diseases in developing countries are likely to
increase due to widespread immunocompromisation in people with HIV/AIDS,
which increases the risk of contracting
diarrhoeal disease (Kahinda et al., 2007).
In many developing countries, potable water
is collected from communal sources which
1
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Fig. 1. The water supply problems in rural areas in the drier regions of Tanzania. (a) left Animals carry water long distances; (b) center and (c) right- people fetch water from traditional wells and small dams. Photo: Nancy Marobhe 2006.
that has been practised by people in some
parts of the developing world is the use of
locally available natural coagulants to removal turbidity and bacteria in surface water
(Schulz & Okun, 1984; Madsen et al., 1987;
Ghebremichael et al., 2005). The natural
coagulation technology has the potential of
replacing or supplementing costly water
treatment chemicals in poor countries. In
addition, the natural coagulants avoid the
human and environmental problems that are
associated with the use of water treatment
chemicals (Crapper et al., 1973; Christopher
et al., 1995; Kaggwa et al., 2001). Using
natural coagulants in developing countries
could alleviate their economic situation and
allow further extension of water supply
services to rural areas (Ndabigengesere &
Narasiah, 1998).
The current research was therefore initiated
in order to assess the water supply services
in urban and rural areas of Tanzania and to
explore the motives and mechanisms behind
traditional treatment of domestic water
supply. Together, these aims formed the
basis for a detailed study on the performance of locally available natural coagulants
for production of potable water for rural
and peri-urban communities in Tanzania and
other developing countries.
were motivated by the serious water supply
problems prevailing in many rural areas and
peri-urban areas where people are obliged to
use alternative sources that are polluted,
with rampant water-borne diseases throughout the country (Fig. 1). Women in rural
villages traditionally treat water from these
sources using locally available plant seed
powder to remove suspended matter. However, it was discovered that although such
plant seeds seem to be effective water clarifiers, good coagulation results were not
always obtained due to lack of understanding on how the seed powder coagulates
turbid waters. Some plant species that produce seeds for water treatment, especially
Parkinsonia aculeata, have multiple uses and
could be cultivated intensively and help to
improve the quality of life of the rural population. It was anticipated that appraisal of
locally available coagulants in scientific
studies would not only benefit the rural
population but also the urban water utilities,
which often produce insufficiently treated
water due to inadequate resources at water
treatment plants. Thus, it was deemed important to conduct investigations on the
performance of traditional coagulants with
the aim of producing more potable water.
Although Moringa oleifera seed, one of the
most effective natural coagulants, has been
extensively studied, scientific investigations
into the coagulation potential of other locally available natural coagulants in other
parts of the developing world are lacking.
1.2 Motivation
A large proportion of the population in
urban and rural areas of Tanzania lack access
to a reliable water supply, regardless of
quality. The studies reported in this thesis
2
Water supply in Tanzania and performance of local plant materials in purification of turbid water
ered in section 5. The results and discussions
from the review of water supply situation in
Tanzania, traditional water treatment processes, performance of crude seed extracts
under varying physical factors, purification
and characterisation of coagulant seed proteins and the effect of coagulant proteins on
physico-chemical quality of treated water
including the antimicrobial effects is presented in section 6. Finally, conclusions
from the study including proposed areas for
further study are given in sections 7 and 8
respectively.
1.3 Objectives
The objectives of this study were to review
the water supply services in selected urban
and rural areas of Tanzania, to investigate
the existence of traditional water coagulation
methods and to carry out laboratory studies
on the performance of locally available
natural coagulants including Vigna unguiculata, Parkinsonia aculeata and Voandzeia subterranea seeds under varying physical operating
parameters. The effects of local coagulants
on physico-chemical quality parameters of
treated water and their antimicrobial effects
on bacteria isolated from river water were
also studied. An additional objective was to
isolate and characterise the active coagulating agent in the seeds.
The specific objectives include:
i) To assess the water supply services in
Tanzania and investigate traditional methods
and procedures for purification of turbid
water in rural areas of Tanzania
ii) To analyse the effect of varying physical
parameters on performance of crude extracts of the locally available seeds (Vigna
unguiculata, Parkinsonia aculeata and Voandzeia
subterranea seeds) during coagulation of river
water samples.
iii) To isolate and characterize an active
coagulant component in the powdered
seeds.
iv) To investigate the effects of crude extracts and purified coagulant proteins of
Vigna unguiculata and Parkinsonia aculeata
seeds on physical and chemical quality parameters of treated water.
v) To investigate the effect of purified coagulant proteins on bacteria isolated from
Ruvu River.
2 OVERVIEW OF WATER
SUPPLY IN DEVELOPING
COUNTRIES
2.1 Urban and rural water supply
Many millions of people, in particular
throughout the developing world, use unreliable water supplies of poor quality, which
are costly and are distant from their homes
(WHO & UNICEF, 2000a). In particular,
water supplied to rural communities worldwide is generally of poorer quality than that
in urban areas (Chongsuvivatwong et al.,
1994; Sugita, 2006). It is generally accepted
that the poor tend to be more vulnerable to
disease and have least access to basic services and water supply is no exception
(Pokhrel & Viraraghavan, 2004). The evidence suggests that interventions targeted at
poor populations could provide significant
health benefits and contribute to poverty
alleviation (DFID, 2001; WHO, 2002; Gundry et al., 2004).
Shortage of clean drinking water continues
to be a significant problem in many parts of
sub-Saharan Africa. The quality and coverage of services from most of the urban
water utilities south of the Sahara remain
poor. The situation is becoming worse with
high urban population growth rates of 2-6%
per year (Njiru & Sansom, 2003). For a long
time, measures taken by governments to
address gaps in service coverage have concentrated on building new infrastructure,
with little attention being given to improving
the efficiency and productivity of water
utilities (Wolff & Gleick, 2002). The situa-
1.4 Thesis outline
The water supply situation in developing
countries is presented in section 2. A review
of conventional water treatment methods
with focus on theory and practice of coagulation-flocculation, sedimentation and disinfection is presented in section 3. Application
of natural materials in water treatment is
covered in section 4. The summary of materials and methods used in the study is cov3
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
tion is aggravated by consumption of imported chemicals such as alum and chlorine
in water treatment processes, since these are
unaffordable for most poor countries. In
Africa, many obstacles, which include bureaucratic barriers between ministries, meagre funds allocated to rural areas and too
few technically qualified persons, have
retarded progress towards safe and adequate
water supplies and improved sanitation
(Muyibi, 1992; Isley, 1995).
Factors such as poor reliability of water
supply, affordability and distance between a
water source and the home have collectively
led households to depend on unsafe sources,
to reduce the volume of water used for
hygiene purposes and to reduce spending on
other essential items (Lloyd & Bartram 1991;
Cairncross & Kinnear, 1992; Howard, 2002).
The attempts to provide potable water by
application of inappropriate technologies in
urban and rural areas of developing countries have led to severe difficulties and even
failure of the projects. Mintz et al. (2001);
Banerjee et al. (2007), pointed out that as the
provision of safe water infrastructure to the
world’s poor will take decades and require
significant investment, the health of these
people could be protected in the short to
medium term by scaling up access to alternative water quality interventions that are
effective and inexpensive. The appraisal of
natural coagulation technology in the context of the present study is among such
interventions, which could help a large
proportion of the population in rural areas
obtain clean drinking water.
problems present, the desired quality of the
treated water, the costs of different treatments and the size of the water system
(Kalibbala, 2007).
However, it should be understood that the
aim in this section is not to review all of the
processes that take place in conventional
water treatment, but only those processes
that are of great significance in water treatment using traditional natural coagulants.
3.1 Coagulation and flocculation
Treatment of water to remove turbidity is
essential for large- and small-scale (e.g.
household) production of drinking water.
The removal of turbidity in water treatment
is essential because naturally suspended
particles are transport vehicles for undesirable organic and inorganic contaminants,
taste-, odour- and colour-imparting compounds and pathogenic organisms (Raghuwanshi et al., 2002). The turbidity of water
often results from the presence of colloidal
particles that have a net negative surface
charge. Thus, electrostatic forces prevent
them from agglomerating, making it impossible to remove them by sedimentation
without the aid of coagulants, which carry
counter-ions. Hydrolysing metal salts based
on aluminium or iron, also known as primary coagulants, are very widely used in
conventional water treatment processes
(Diaz et al., 1999). The high cationic charge
of these two metal salts makes them effective for destabilising colloids. They act by
neutralising the negative charges of the
stable colloidal particles (coagulation) and
are followed by the addition of organic
coagulant aids that enhance particle collision
and agglomeration of neutral particles to
form dense flocs (flocculation) that can
settle easily. Destabilisation of colloidal
particles in water is accomplished via adsorption and charge neutralisation, adsorption and interparticle bridging, enmeshment
in a precipitate and double layer compression (Amirtharajah & O´Melia, 1990; Gregory & Duan, 2001).
In addition to inorganic coagulants (aluminium and iron salts), water-soluble organic
polymers, also known as polyelectrolytes, are
3 REVIEW OF
CONVENTIONAL SURFACE
WATER TREATMENT
Water treatment usually comprises water
clarification and disinfection processes
(Suarez et al., 2002). In conventional water
treatment a series of processes including
coagulation, flocculation, sedimentation,
filtration and disinfection are often involved
(Edzwald et al., 1989; AWWA, 1990). A
combination of several processes is usually
needed to improve the quality of raw water
depending on the type of water quality
4
Water supply in Tanzania and performance of local plant materials in purification of turbid water
used in water treatment to remove turbidity.
Polyelectrolytes can be either natural or
synthetic and they can be used as both
primary coagulants and coagulant aids
(Sanky, 1978; Hashimoto et al., 1991). Polyelectrolyte primary coagulants are cationic
with high charge density and low molecular
weight, while synthetic polyelectrolyte coagulant aids have relatively high molecular
weights and facilitate flocculation through
inter-particle bridging (Gregory & Duan,
2001). Although polyelectrolytes are more
expensive than aluminium and iron salts in
terms of material cost, overall operating
costs can be lower because of reduced need
for pH adjustment, lower sludge volumes,
no increase in total dissolved solids in
treated water and shorter settling time
(Mahvi & Razavi, 2005). However, polyelectrolytes are not readily available and also
costly for most parts of the developing
world. The natural polyelectrolytes such as
water-soluble proteins released from crushed
seed kernels are potential alternatives to
synthetic polyelectrolytes. The merits of
natural polyelectrolytes (which are extracted
mainly from certain plants) over synthetic
include safety to human health, biodegradability and a wide effective range of flocculation for various colloidal suspensions
(Kawamura, 1991; Özacar & Şengil, 2003).
The performance of the hydrolysing metal
salts is significantly influenced by the pH of
solution and they have a good coagulation
effect within a certain pH range of the
water. The coagulation process in water
treatment can be modified to facilitate the
removal of dissolved organic matter (enhanced coagulation), which has been reported to occur optimally at pH 5-6 (Gregory & Duan, 2001) and at maximum rate at
pH 4 (Gregor et al., 1997). Low temperature
affects the coagulation and flocculation
process by altering the coagulant solubility,
increasing the water viscosity and retarding
the kinetics of hydrolysis reactions and
particle flocculation. Poly-aluminium coagulants are more effective in cold water than
alum, as they are pre-hydrolysed.
To achieve effective coagulation, proper
mixing is also necessary to allow active
coagulant species to be transferred onto
turbid water particles. Proper mixing after
addition of coagulants into raw water facilitates optimum removal of fine particles in
the supernatant. This is because very fine
particles become transformed to aggregates
under good mixing condition (Kan et al.,
2002).
It is commonly observed that particles are
destabilised by small amounts of hydrolysing
metal salts and that optimum destabilisation
corresponds with the neutralisation of particle charge. Larger amounts of coagulants
cause charge reversal so that the particles
become positively charged and thus restabilisation occurs, which results in elevated
turbidity levels. Thus, careful control of
coagulant dosage is needed to give optimum
destabilisation (Gregory & Duan, 2001) and
this is determined to a great extent by the
consistency of raw water quality. As the
present study investigated the performance
of natural coagulants that had not been
investigated previously, identification of
some factors that influence the coagulation
process was necessary.
3.1.1 Factors affecting coagulationflocculation
Coagulation and flocculation processes are
dependent on numerous inter-related factors, which sometimes makes optimisation
of the processes cumbersome. Such factors
include the characteristics of the water
source, raw water pH, alkalinity and temperature, the type of coagulant and coagulant aids and their order of addition, dose
rates of coagulants, the degree and time of
mixing provided for chemical dispersion and
floc formation (Rossi & Ward, 1993; Kalibbala, 2007). For water with low alkalinity
coagulant can consume virtually all of the
available alkalinity, hence lowering the pH to
a level that hinders effective treatment, while
high alkalinity waters may require additional
chemicals to lower the pH to values favourable for coagulation.
5
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
1999). Although the risks associated with
DBPs are low, associations with such diseases cannot not be ruled out unambiguously (Van Benchosten & Edzwald, 1990;
Boisvert et al., 1997; Bove et al., 2002; Woo et
al., 2002). The search for disinfectants that
are cheap, maintain acceptable microbiological quality and avoid chemical risks is one of
the biggest challenges facing the water
treatment industry.
3.1.2 Health risks associated with chemical
coagulation and flocculation
Although the water treatment chemicals are
effective and used worldwide, scientific evidence shows that exposure to chemicals
during coagulation with metal salts could be
associated with adverse health effects (Driscoll &. Letterman, 1995). Aluminum, which is
the most major component of aluminium
sulphate (alum), polyaluminium chloride
(PAC) and polyaluminium silico sulphate
(PASS), could induce Alzheimer’s disease and
other similar related problems that are associated with residual aluminium in treated water
(Miller et al., 1984; AWWA, 1990). Moreover,
monomers of some synthetic organic polymers such as acrylamide have neurotoxicity
and strong carcinogenic properties (Crapper
et al., 1973; Hashimoto et al., 1991).
4 REVIEW OF TRADITIONAL
PLANT MATERIALS USED IN
WATER TREATMENT
4.1 Traditional natural coagulants
The use of natural materials for treatment of
drinking water in some parts of the world
has been recorded throughout human history. However, the natural materials have
not been recognised or duly supported due
to lack of knowledge on their exact nature
and the mechanism by which they function.
As a consequence, the natural materials have
been unable to compete effectively with the
commonly
used
water
chemicals
(Ndabigengesere & Narasiah, 1998). In
recent years there has been a resurgence of
interest in using naturally occurring alternatives to currently used coagulants for water
treatment in developing countries (Jahn,
1981, 1988), mainly due to cost implications
that are associated with inorganic chemicals,
synthetic organic polymers and disinfectants
(Schultz & Okun, 1984, Ndabigengesere &
Narasiah, 1995). There is also an interest in
reusing some of the by-products from natural coagulants in other enterprises (Kawamura, 1991).
Traditionally, treatment of turbid surface
water sources is carried out at household
level using local materials of plant or animal
origin (Okun, 1984; Jahn, 1988, 2001) For
example, rural people in Sudan and Malawi,
who depend on muddy water from rivers or
intermittent streams, natural rain ponds and
artificial rain-water catchments for domestic
water supply, treat water fetched from such
sources using Moringa seeds and other plant
and soil materials (Jahn & Dirar, 1979; Eilert
et al., 1981). In India, crushed seeds of the
3.2 Water disinfection and associated
health risks
Disinfection of the clarified water prevents
the growth of microorganisms both in the
plant and in the distribution system, thus
protecting the public from water-borne
diseases. Like chemical coagulants, disinfectants (chlorine in particular) combine with
natural organic matter (NOM) that may be
present in water to form trihalomethanes
(THMs), which are carcinogenic and/or
mutagenic by–products (Tokmak et al.,
2004). These THM cannot be removed by
conventional treatment methods and thus
water to be chlorinated should either be free
from natural organics, or if NOM is present
an alternative disinfectant should be used.
Alternative disinfectants such as chlorine
dioxide, chloramines and ozone are also
associated with the formation of disinfection
by- products (DBPs) that are toxic compounds and impart objectionable taste and
odour (Kiely, 1997; Sadiq & Rodriguez,
2004). Irradiation with ultraviolet (UV) light
is a promising alternative method of disinfection but it is expensive and leaves no
residue and hence another disinfectant is
required to disable bacteria and viruses. In
addition, UV light can react with nitrate in
water to produce nitrite, the precursor for
methaemoglobinaemia in infants (Mole et al.,
6
Water supply in Tanzania and performance of local plant materials in purification of turbid water
nirmali tree (Strychnos potatorum) have been
used for centuries to clarify muddy water
(Tripathi et al., 1976). In Peru, villagers
clarify turbid water using cactus leaves and
‘tuna’ (e.g. Opuntia ficus indica Mill.). Traditional water treatment using crushed or
chopped Maerua pseudopetalosa (kordala) roots
is practised in some parts of Sudan. In
Northern Chad and villages around
Maiduguri in Northern Nigeria, people use
wood ash as a natural water coagulant (Jahn
& Dirar, 1979). Knowledge on natural coagulants is widespread in many parts of the
developing world and therefore there is
good potential for such knowledge to be
used efficiently provided concerted efforts
can be devoted to maximising their performance through research.
It has also been observed that the reduction
in turbidity is associated with significant
improvements in bacteriological quality
(Grabow et al., 1985; Madsen et al., 1987;
Ghebremichael et al., 2005). There are only a
few reports on the effect of natural coagulants on bacteriological quality of the treated
water, as most studies on natural coagulants
concentrate on efficacy of turbidity removal.
Tripathi et al. (1976) showed that the crude
extract of Nirmali seed reduced 50-52% of
bacteria after 30 min of settling time of
turbid water coagulated by 0.5 mg/L of seed
extract. The crude extract and purified
proteins of M. oleifera seed have been reported to possess antimicrobial properties
(Tripathi et al., 1976; Madsen et al., 1987;
Suarez et al., 2003; Ghebremichael et al.,
2005). Furthermore, Eilert et al. (1981)
identified an active antibiotic component
4(α-L-Rhamnosyloxy) benzyl isothiocyanate
in M. oleifera and M. stenopetala seeds that acts
on several bacteria and fungi.
Studies on the antimicrobial effects of Moringa seeds have shown that there are specific
mechanisms of action of antimicrobial
agents on microorganisms (Conte et al.,
2007) in addition to the removal of flocculated microorganisms by settling along with
the colloidal particles in properly coagulated
and flocculated water (Casey, 1997). The
effect of natural coagulants on turbidity
removal and the antimicrobial properties
against microorganisms may render them
applicable for simultaneous coagulation and
disinfection of water for rural and periurban people in developing countries.
4.2 Natural biocides
Recent studies have shown that acidification
of food and drinking water with acidic
consumables, notably Citrus (lime or lemon
juice), protects people against cholera
(D´Aquino & Teves, 1994; Rodrigues et al.,
1997). However, few formal evaluations of
the disinfection effects of lime and lemon
juice have been conducted and information
on their disinfection potential for naturally
contaminated water sources is scarce. Due
to the chronic water-borne diseases in most
parts of the developing countries, efforts are
being made to identify less costly, more
4.1.1 Performance of natural coagulants
Studies have been conducted to evaluate the
coagulation efficiency of many plant materials including extract of Moringa seeds
(Ndabigengesere et al., 1995; Ndabigengesere
& Narasiah, 1998; Babu & Chaudhuri, 2005;
Ghebremichael et al., 2005; Bhuptawat et al.,
2007); okra and nirmali seeds (Al-Samawi &
Shokralla, 1996); tamarind seeds (Bhole,
1995); extracts of Prosopis juliflora and Cactus
latifaria (Diaz et al., 1999); and vegetable
tannins (Özacar & Şengil, 2003). The coagulation potential of chitosan, one of the
effective natural coagulants extracted from
the organic skeletal substance in the shells of
crustacean has been studied by Huang &
Chen (1996); Huang et al. (2000); Divakaran
& Pillai (2004). The crude extract of M.
oleifera seed is the most extensively studied
natural coagulant. Jahn (1984) conducted a
preliminary study aimed at improving the
coagulation efficiency of Moringa seed based
on traditional methods used by women in
Sudan. This study revealed that scientific
advice and support are necessary to improve
the traditional water clarification methods.
Laboratory studies using natural and artificial water samples have shown that Moringa
seeds are highly effective in coagulating and
removing suspended solids from water
containing medium to high initial turbidity
(Sutherland et al., 1989).
7
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
appropriate and non-toxic biocides to be
used in communities without treated or
protected water supplies (Anderson, 1991;
D´Aquino & Teves, 1994). In this regard
lime and lemon trees, that are native in most
parts of the tropical and subtropical world,
could be among the potential sources of
natural biocides of choice, although systematic studies to evaluate their performance is
of paramount importance.
4.3 Purification of coagulating seed
proteins
The main problem with crude seed extracts
is the release of organic load into the treated
water, which encourages microbial decomposition of organic compounds that cause
colour, taste and odour problems. These
problems are amplified when the treated
water is stored for long periods
(Ndabigengesere & Narasiah, 1998; Ghebremichael et al., 2005). To overcome these
problems, researchers working with Moringa
have been trying to develop methods for
extracting the active coagulating component
from Moringa seeds and separate it from
inactive proteinous and non-proteinous
materials. Ndabigengesere et al. (1995) purified active coagulant protein from Moringa
seed by precipitation with ammonium sulphate, ultrafiltration, dialysis, ion-exchange
chromatography and lyophilisation. However, the method is complex and too costly
for use in poor countries. Ghebremichael et
al. (2005) have developed a simple method
based on ion exchange (IEX) chromatography for purification of M. oleifera coagulant
protein that is very appropriate for use in
poor countries. The leguminous seed extracts used in the present study were a heterogeneous mixture of organic and inorganic
compounds. Therefore, it was necessary to
isolate the active coagulating agent using
cheap and straightforward methods that can
be easily adopted in poor communities.
Some important characteristics of plant
species that produce the coagulant seeds are
described below.
4.4.1 Parkinsonia aculeata
P. aculeata (Jerusalem thorn), also known by
vernacular name mkeketa, is a shrubby
thorny tree (3-10 m tall) that belongs to the
family Fabaceae. It is fast growing, drought
tolerant, resistant to biotic stresses and able
to grow in different soil types. P. aculeata
seeds have a thick, hard coat that allows
them to remain viable for many years. This
species is an indigenous or planted tree and
has spread throughout the tropics for different uses including fodder, firewood, construction materials, fencing and shade (Foroughbakhch et al., 2001) and folk medicine
(Andrade-Cetto & Heinrich, 2005; Leite et
al., 2007). The large, fragrant, golden-yellow
flowers easily attract bees and may give
people the opportunity for beekeeping
activities. Like many legumes, P. aculeata
seeds are very rich in crude protein and
digestible fibre, making them a potential
source of low-cost protein. However, the
seeds are among the most under-utilised
leguminous seeds due to lack of adequate
knowledge regarding their nutritional composition. The fruit pulp (pod) can also be
eaten and has up to 60% sugar content
(Foroughbakhch et al., 2001; Prakash et al.,
2001). The pod of the seed contains 1-4
seeds but occasionally up to 11 (Fig. 2).
Mature trees typically produce about 5,000
seeds per year, but can produce in excess of
13,000. The rural populations in the central
dry areas of Tanzania are mainly crop farmers, although keeping of cattle is also practised. Besides clean water, they also need to
restore degraded land, improve the fertility
of agricultural land and need other basic
items such as firewood, building poles,
fodder and income-generating activities. The
multipurpose, fast growing and nitrogenfixing P. aculeata trees appear to be the most
promising for improvement of the quality of
life for people in semi-arid areas.
4.4 Natural plant materials for water
treatment in Tanzania
Most of the plant seeds that are used by
rural women in semi-arid parts of Tanzania
for treatment of drinking water belong to
the genus Fabaceae (legume or pea family).
8
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Lemon oil is one of the most important
food-flavouring agents and both lemon and
lime oil is also used in the production of
perfumes and cosmetics (Vekiari et al., 2002;
Gamarra et al., 2006). Traditionally, lime is
an everyday food ingredient in Tanzania and
other African countries. It is also used to
prepare beverages and possesses a variety of
medicinal applications (Al-Khayri & AlBahrany, 2001). It has been reported that the
acidic juices have a protective effect on
enteric pathogens present in food. Studies
confirming the effect of limejuice on coagulation and disinfection of drinking water for
use in many rural and peri-urban areas may
improve the health situation in rural and
urban areas of Tanzania that lack potable
source and also increase the economic value
of the lime.
Fig. 2. Part of a P. aculeata tree showing the
mature seed pods.
4.4.2 Vigna unguiculata
Vi. unguiculata or cowpea is a heat loving,
drought resistant crop and plays a role in
low input production systems, particularly
on small-scale farms (Quass, 1995; Graham
& Vance, 2003). Cowpeas are rich in protein and hence regarded as a seed vegetable
that provides an inexpensive alternative
source of protein in Africa and other parts
of the developing world (Popelka et al.,
2004). They can be grown as a multi purpose
crop for instance the green pods can be used
as a vegetable, the remaining part as livestock fodder and the dry cowpeas as the
seed food protein. Cowpeas produce 8-20
seeds per pod and weigh between 5-30 g
per100 seeds.
5 MATERIALS AND
METHODS
5.1 Urban and rural water supply in
Tanzania
The review of water supply services in
Tanzania was conducted using Singida rural
district and Dar es Salaam city as case study
areas (Paper 1). Singida rural district is located in a semi-arid area of central Tanzania
while, Dar es Salaam city is located along the
coast of the Indian Ocean on the eastern
side of Tanzania (Fig. 3). Literature studies,
field observations and discussions with
stakeholders were used to gather information about the historical development and
social, technical, management, financial and
traditional aspects of water supply in the
case study areas.
4.4.3 Voandzeia subterranea
Vo. subterranea (Bambara groundnut) is an
indigenous African legume grown primarily
by subsistence farmers (Enwere & Hung,
1996). It is tolerant to drought and resistant
to pests and disease, and yields in soils too
poor to support the growth of other legumes such as groundnuts (Brough & AzamAli, 1992). The plant is grown in many parts
of Tanzania as food and is commonly used
for traditional water treatment in villages
located in dry areas.
Specific studies on water supply problems
were conducted in four villages including,
Msange, Mipilo, Mangida and Sifunga, which
are located in Singida rural district (Paper
II). Structured questionnaires (open-ended
and closed questions), focus group discussions with key informants and participatory
methods were employed to study the existing socio-economic activities, water supply
situation and traditional water coagulation
methods. Questionnaire interviews were
conducted with between 49 and 85 houses,
4.4.4 Citrus aurantifolia
C. aurantifolia (lime) belongs to the family
Rutaceae. Lime trees are cultivated throughout the tropics and in warm subtropical
areas as a commercial crop. In addition to
juice production, essential oil is one of the
main by-products of citrus processing,
usually obtained a by distillation process.
9
Nancy Jotham Mwaisumo Marobhe
Fig. 3. Index map of
Tanzania showing the
location of the case study
areas.
TRITA LWR PhD Thesis 1042
40
35
0
0
L. Victoria
Singida Rural District
5
anyik
L. Tang
5
Singida
INDIAN OCEAN
a
Dar es Salaam
TANZANIA
L. Nya
AFRICA
0
sa
35
20
based mainly on systematic random sampling. In each village, the first nearest house
was selected for sampling, followed by the
systematic sampling of houses along the
surveydirection. In villages where some
houses were distant from each other, for
reasons of convenience the nearest houses
were selected for interview.
40
5.2.2 Preparation of seed powder and crude
seed extracts
The seed kernels were ground into fine
powder in a kitchen blender or by pestle and
mortar. Seed powders with different grain
sizes were obtained by laboratory sieving
through mesh sizes that ranged from 0.200
to 0.850 mm using Laborsrebmoschine
model EML 200-67.
Crude seed extracts (CSEs) were prepared
from the seed powder as 1-5% solution
(W/V) in distilled water. The suspensions
were stirred for 15 min at room temperature
(25 ºC ±2) and then filtered through nylon
cloth and/or Whatman No. 3 filter to obtain
the CSEs. More refined CSEs were obtained by filtering the prepared CSEs using
either fine fibre material with pore size of
about 10 µm, or fibreglass filter with pore
size of 0.45 µm, or centrifugation (3000
RPM, 2 min).
5.2 Coagulation experiments under
varying physical parameters (Paper III)
5.2.1 Source of seeds and their chemical
composition
Dry seeds of Vigna unguiculata (VU), Parkinsonia aculeata (PA) and Voandzeia subterranea
(VS) were obtained from households in
Singida rural villages or from local markets
and stored at room temperature. The chemical composition of the seed powder of VU,
PA and VS was analysed at the Government
Chemical Laboratory, Dar es Salaam.
10
Water supply in Tanzania and performance of local plant materials in purification of turbid water
5.3 Purification and characterisation of
active coagulant proteins (Paper IV)
5.2.3 Source of water samples
Water samples were collected in 20-L plastic
buckets from the Ruvu River at Mlandizi,
Tanzania, during the dry season of 2006.
Samples with different turbidities were
prepared by mixing the sampled clear and
muddy river water to produce samples with
low (50 FTU), medium (205 FTU) and high
(500 FTU) turbidity. The muddy water was
stirred and allowed to settle for 5 min before
mixing with clear water. No fixed volumes
of clear and muddy water were established
to produce a particular turbidity level.
5.3.1 Purification
Active coagulant proteins in the CSEs of
VU and PA were purified by batch IEX
chromatography and gel filtration. The IEX
chromatography was carried out using 1 mL
of CM sepharose fast-flow matrix cation
exchanger with bead size 45-165 µm (BioRad, Sweden). The matrix was equilibrated
with 10 mM ammonium acetate buffer (pH
7.2) and CSEs were added at a dosage of 25
mg/L of the matrix. The bound proteins
were eluted with 0.3 and 0.6 M NaCl in the
same buffer. Eluted proteins were desalted
through PD-10 columns pre-packed with
sephadex G-25 (Amersham Biosciences AB)
using Milli Q water.
5.2.4 Experimental and analytical procedures
The effect of varying physical parameters on
coagulation of turbid water with the CSEs
was evaluated using a jar tester (Model
Phipps and Bird-PB-700TM). Lime (Citrus
aurantifolia), prepared as 1% solution (W/V)
from crystals was used to regulate the pH of
water samples. Water samples with different
turbidities and seed powder with different
grain sizes were obtained as described in
sections 5.2.3 and 5.2.2 respectively. The
effects of slow and rapid mixing intensity
and duration on coagulation were determined and the mean velocity gradients were
calculated using equation (1). The computation of the mean velocity gradients using
relevant experimental values used in this
study is shown in Paper III.
Pn
µV
5.3.2 Characterisation and analytical procedures
5.3.2.1 SDS-PAGE Electrophoresis
The molecular masses and purity of the
purified proteins were analysed by SDSPolyacrylamide Gel Electrophoresis (SDSPAGE) on 10% acrylamide gel using a MiniPROTEN 2 apparatus (Bio-Rad) and tristricine SDS-PAGE (Hultmark et al., 1983).
Protein dye binding method (Bradford, 1976)
was used to quantify protein concentrations
in CSEs samples using bovine serum albumin
as a standard.
(1)
5.3.2.2 Coagulation activity using small
sample volume
Where:
G = velocity gradient (s-1)
P = power dissipated (W)
n
V = volume of water (m3)
µ = dynamic viscosity of water (N s m-2)
Preliminary coagulation experiments were
conducted at rapid and slow mixing speeds
of 175 RPM and 40 RPM for durations of 3
min and 40 min respectively. Coagulant
dosages were added into beakers during
rapid mixing. After settling for 30 min,
samples were drawn at 5 cm from the surface and residual turbidity were measured
using a spectrophotometer model 21 D at
wavelength 450 nm.
Raw water samples:
A stock of synthetic turbid water samples
was prepared by suspending 10 g of kaolin
clay in 1 L of tap water. The suspension was
stirred for 30 min and left to stand for 24 hr
to hydrate particles. The desired turbidity
was prepared by mixing a fraction of decanted clay suspension with tap water. The
pH of water samples was kept constant at
7.3 ±1 using 0.1 M HCl.
Preparation of Citrus juice and alum:
Citrus fruit juice (CF) was squeezed from
ripe fruits and filtered through a fine fibre
material. The filtrate was allowed to stand
for 2 hr and the supernatant was decanted
and stored. The pH of the filtrate was 2.55.
G=
11
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Aqueous aluminium sulphate (alum) was
also prepared as a 5% (W/V) solution.
Coagulation activity:
One millilitre of clay suspension was employed for measurement of coagulation
activity of CSEs, purified proteins, CF and
alum. Different dosages of coagulants were
added to the water sample to produce a final
volume of 1 mL in a semi-micro plastic
cuvette (10x4x45 mm, Sarsted Aktiengesellschaft & Co. Germany) and homogenised
instantly. The samples were allowed to settle
for 90 min or more and thereafter the absorbancies were measured at 500 nm using
UV-visible spectrophotometer (Cary 50
Bio). Coagulation activity was measured as
the difference between the absorbance at
zero time and absorbance after 90 min of
settling time.
were run against the bacteria database using
a blast search (NCBI).
5.4.2 Flocculation and growth inhibition
Isolates representative of Gram-positive and
Gram-negative bacterial spp. were cultured
in 0.2 M phosphate buffered Lauryl broth
(LBB) at 30°C with shaking overnight. The
cultures were diluted 10x with diluted LBB
to get the desired microbial density (OD620).
In cell flocculation studies, dosages of CSEs
and purified proteins were added to the
culture suspensions and then these were
incubated at 30°C for 4 hr. Cell aggregations
were observed under the microscope (Olympus BX51 with AnalySIS) and images were
captured using a Sony PC 120 camera.
For growth curve studies, overnight bacterial
cultures diluted in LLB were inoculated into
sterile 96-well microtitre plates (Greiner bioone). Ten microlitres of diluted proteins and
CF were added to wells containing 90 µL
bacterial cultures. The plates were incubated
at 30ºC in a FLUOstar* OPTIMA (LabVision, Sweden) spectrophotometer with
shaking at 5 min intervals and changes in the
OD620 values were recorded.
5.3.2.3 Effect of thermal treatment, pH
and settling time
Thermal stability of CSEs and purified
proteins was determined at 40, 80 and 95 °C
for 0.5 to 5 h in a heating block Different
dosages of the cooled protein samples were
added into the kaolin water samples to check
their coagulation activity. The pH range for
coagulation activity was 4.5 to 9.5, while
floc-settling studies were carried out from
0.5 to 5 hr.
5.4.2.1 Effect of purified proteins, crude
seed extracts and citrus juice on natural
bacteria
The antimicrobial effect of the purified
proteins, CSEs and CF was studied on
natural river water bacteria using jar tests.
Water samples were collected in sterile 1-L
plastic bottles during the dry season. After
determination of the initial pH, different
doses of purified proteins, CSEs and CF
were added, followed by rapid and slow
mixing of samples. The dose of CF ranged
from 0 to 0.9%. Faecal coliforms (FC) in the
clarified water were determined using Standard Method 9221E Faecal Coliform Membrane Filter Procedure (Standard Methods,
1998) after 30 min-24 hr of settling time.
5.5 Physico-chemical quality studies of
coagulated charco dam water (Paper VI)
5.4 Antimicrobial effect (Paper V)
5.4.1 Bacterial isolation and identification
Bacterial strains were isolated from water
samples collected from the Ruvu River. The
strains were isolated on nutrient and
McConkey agar (Oxoid) plates at an incubation temperature of 20, 30 and 37°C under
aerobic and anaerobic conditions. Pure
cultures were obtained by repeated streaking
on nutrient agar and incubation at 30°C for
24-48 hr. Bacterial isolates were identified by
cultural and morphological characteristics
(Krieg & Holt, 1984) and biochemical tests
according to Cappuccino & Sherman (1987).
Moreover, representative Gram-positive and
Gram- negative bacterial strains were identified by API tests and 16S rRNA gene analysis (as detailed in paper V). The sequences
5.5.1 Sampling of charco dam water and
coagulation experiments
Water samples were collected in 10-L buckets
from Nunguru charco dam, located at Mipilo
12
Water supply in Tanzania and performance of local plant materials in purification of turbid water
village in Singida rural district, during the dry
season of 2007. Samples were collected from
a pipe that discharges into a cattle trough.
Coagulation-flocculation experiments were
performed using jar tests at rapid and slow
mixing speeds of 150 and 40 RPM for durations of 5 and 30 min respectively. The quality parameters of water coagulated with different doses of CSEs, 0.6 M NaCl eluted
proteins (un-desalted proteins) and alum were
determined following the settling phase of 30
min.
neighbours are taken into account, they are
indicators of inadequate water supply
(Mwaiselage, 2003; Katko, 1991).
Up to 70% of government expenditure on
the water sector comes from external
sources and the rural water supply receives a
higher funding level than the urban water
sector (Table 2). However, these figures
show a high discrepancy between the funding levels for rural water supply and the
actual water supply coverage, the situation,
which indicates poor planning and management of water supply projects (URT, 2002).
The chronic water supply problems are
responsible for endemic cholera in most
regions of Tanzania (WHO, 2001), with
small outbreaks being reported every year
and much larger outbreaks occurring every
4-5 years (Fig. 4). Similarly, in Latin America
and the Caribbean, about 40% of the population consume water of substandard quality
(Pan American Health Organization, 1994),
which creates health risks.
5.5.2 Analytical methods
Turbidity, pH, TDS, sludge volume, conductivity, alkalinity, concentration of a cation
(Fe2+) and anions (NO3- and PO43-), and
COD in the treated water were analysed
according to Standard Methods (1998), as
described in Paper VI. For determination of
the settled sludge volume, the water samples
collected from the Ruvu River (205 NTU)
were first coagulated with different dosages
of 1% (W/V) CSE of VU and PA in jar test
experiments and allowed to settle for 30
min. The clarified water was decanted and
50 mL of the sludge were transferred into
settling columns. The volumes occupied by
the suspension were recorded for 60 min at
intervals of 5 min.
6.1.1 Urban water supply: The case of Dar es
Salaam city
Dar es Salaam city has a population of about
2.5 million, which is about 30% of the urban
population in Tanzania. The growth rate is
estimated at 8% per annum. About 70% of
the population live in informal settlements
with marginal infrastructure development,
water being no exception (Chaggu et al.,
2004; Kyessi, 2005). The water system in
Dar es Salaam city is managed and operated
by Dar es Salaam Water Supply and Sewerage Authority (DAWASA). Similar urban
water supply and sewerage authorities
(UWSSAs) exist in other cities. However,
since 1997 DAWASA has been privatised
but its operational achievements are yet to
be recorded (Kyessi, 2005; URT, 2006).
There is mounting opposition to privatisation of water in developing countries from
civil society and consumers that calls for
caution in the privatisation process (K’
Akumu, 2006) in order to ensure adequate
and sustainable water supply for urban
populations.
The existing water supply infrastructure for
Dar es Salaam city is old, worn-out and
6 RESULTS AND DISCUSSION
6.1 Review of urban and rural water
supply services in Tanzania (Paper I)
An overview:
A large proportion of the population in
urban and rural areas of Tanzania faces
acute water supply problems as regards both
quantity and quality aspects. The water
supply coverage in rural and urban areas is
only 42 and 80% respectively (Table 1).
These figures give the impression that a
large proportion of the urban population has
access to adequate water supply. However,
when other factors such as intermittent
supply, waiting time in queues at water
points, distance to water sources, costs of
buying water from street vendors and trucks,
and inconvenience caused to those who
have taps in their houses in assisting
13
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Table 1. Current coverage of water supply in Tanzania (in thousands)
Service
area
Population
With house
connection
With public
water point
Served
Not
served
% Pop. served
Urban
Rural
Total
11,021
22,496
33,517
1,212
172
1,384
3,932
8,552
12,484
8,817
9,448
18,265
2,204
13,048
15,252
80
42
54
Source: WHO 2000b, part II page 256.
Table 2. Sources of investment (in 1000 US$) for urban and rural water supply and sanitation
Service area
National Funds
External Funds
Total
Urban water
Rural water
Urban sanitation
Rural sanitation
Total
794
1,332
190
46
2,362
2,121
2,720
597
117
5,555
2,915
4,052
787
163
7,917
50
40
30
20
10
0
Cases
Deaths
No. of deaths
500
400
300
200
100
0
M
Da
wa r
nz
Ta a
bo
ra
Co
as
R t
Ki u kw
lim
an a
ja
ro
Ta
ng
M a
be
y
Ka a
ge
M
or r a
og
o
Si ro
ng
id
a
Iri
ng
a
Sh Lin
in d i
ya
ng
a
M
ar
M a
tw
a
Ar ra
us
Ru ha
vu
Do ma
do
m
Ki a
go
m
a
No. of cases
Source: WHO 2000b, part II page 259.
Regions
Fig. 4. Prevalence of cholera by region in Tanzania.
inadequate to meet the ever-increasing
demand for water (URT, 2002). The total
output from the water treatment plants is
270,000 m3 /day, of which only 175,500
m3/day (65%) reach the consumer. Moreover, an average of 60 % of the pumped
water is lost through worn-out distribution
system and only 40% eventually reaches the
consumers. Part of the remaining demand is
obtained privately, either from boreholes or
shallow wells, traditional wells and rivers or
streams (Chaggu et al., 2002; Mato, 2002).
Sepällä & Katko (2003); the World Bank
(2004) also reported that more than onethird of water production in Africa is lost
through physical and commercial losses, and
revenues are insufficient to cover operating
costs and expand service coverage. Similarly,
among the major issues that face the UWSSAs apart from the poor water supply ser
vices are poor billing and revenue collection
systems which is magnified by increasing
number of payment defaulters (URT, 2002;
Mwaiselage, 2003). The current average
domestic water tariff for UWSSAs is about
US$ 0.25/m3 and about 72% of the UWSSAs have an operating costs to operating
revenue ratio of 1.18 to 2.04, which contributes to the financial incapability of
DAWASA and other UWSSAs to maintain
their facilities. With the growing urban
populations in African countries, reducing
wastage and losses are predicted to become
a key strategic concern for water utilities
seeking to increase their service coverage
(Mugabi et al., 2007a,b). Hrudey et al. (2006)
14
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Table 3. Number of water supply sources in Singida Rural District
Type of water sevice/Years
Shallow wells
(0 -10 metres)
2001
2002
2003
June 2004
495
495
495
130
130
132
135
139
Medium depth boreholes
(0-60 metres)
56
56
59
59
59
Deep wells (60 metres & above)
36
36
37
39
39
Springs
22
22
22
22
22
Rainwater harvesting
16
16
16
16
16
Small dams
(charco dams)
or
reservoirs
507
September 2005
507
Large dams
15
15
16
16
16
Boreholes fitted with windmill
14
14
14
14
14
Source: Singida District Water Dept., 2006.
also pointed out that water utilities must
seek ways to maximise the availability, serviceability and life of their assets and minimise expenditure on energy, chemicals and
processes. The high cost of water treatment
chemicals hinders the use of appropriate
dosages at treatment plants, especially during
the rainy season when river water turbidity is
very high. The water scarcity in Dar es
Salaam city has created a social contrast
whereby the poor, especially those living in
squatter areas, have to pay more than the
upper class residents for the same amount of
water used (Mashauri & Katko, 1993;
Chaggu et al., 2002). Similarly, UNICEF
(1989) reported that indigent populations
often pay exorbitant prices for limited quantities of poor quality water, with costs that
can represent 20% of family budget. This
situation increases the risks of contracting
water-borne diseases and also supports
findings by the WHO & UNICEF (2000b),
which reported that the poor tend to be
more vulnerable to disease and have least
access to basic services.
has access to a reliable water supply. However, over 30% of the rural water supply
schemes installed are not functioning properly because of lack of commitment of the
beneficiaries to operation and maintenance
of the facilities, which were provided without the active participation of the beneficiaries in planning and management (URT,
2002, 2004). Currently, the government is
implementing Rural Water Supply and
Sanitation Projects (RWSSPs) with financial
assistance from the World Bank. The
RWSSPs encourage people to work together
to plan, develop and manage their own
water and sanitation facilities (MoWLD,
2003). However, the RWSSPs face different
types of problems, including financial constraints, poor operation and maintenance
and poor governance. As a result, the average rural water supply coverage is only 42%
WHO, 2002), with actual coverage ranging
between 26.9 and 65.0% (URT, 2004).
Singida Rural District is among the districts
where the RWSSPs are implemented. The
main water supply sources in Singida Rural
District are shallow wells, small man-made
reservoirs (charco dams) and medium depth
boreholes (Table 3). The ratio of population
served to water supply source is 1171:1,
which is approximately 167 households per
water source. However, about 70% of water
schemes installed (of which 67% are shallow
6.1.2 Rural water supply: The case of Singida
rural district
About 80% of Tanzania’s estimated population of 34 million live in rural areas. Despite
significant investment in the rural water
supply (RWS) since the early 1970s, at present only about 50% of the rural population
15
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Fig. 5. Location of case study villages and the main water supply sources.
wells) are impaired, leaving a large population without water supply. Effective institutional arrangements for community management and user education are crucial for
sustaining water supply systems. In addition,
project planners have an obligation to remedy the rural water supply situation by designing projects that are not only technically
feasible but that will also continue to function for a long period of time.
6.2 Rural water supply and traditional
treatment (Paper II)
non-potable, include Suke dam, charco dams
and traditional wells or water holes (Fig. 5
and also detailed in Table 3 in Paper II).
Seasonal streams and ponds supplement the
existing sources during the rainy season.
Despite the joint efforts of the government,
donor agencies and local communities in
installing new water schemes, such schemes
are poorly distributed in the area and most
of them are malfunctioning. This situation is
caused by the poor economic basis of villagers, which renders them unable to afford to
maintain the village water funds, poor operation and maintenance of water schemes due
to lack of technical skills and a free water
attitude that cause villagers to lack commitment to maintenance of the facilities. As a
consequence, more than 80% of the villagers
lack access to a reliable water supply source.
Such lack of access to water supply and
sanitation facilities constrains the opportunities of rural people to escape poverty. In
order to increase the water security of rural
households, multiple sources should be
utilised depending on the season and geographical location (Kahinda et al., 2007).
6.2.1 Water supply sources
Specific studies into water supply problems
and the use of locally available materials for
treatment of turbid waters were conducted
in the four villages in Singida rural district.
The population of Msange, Mipilo, Mangida
and Sifunga is 4728, 4442, 928 and 3314
respectively, with an average of 5 persons
per household. Most households (99%) are
occupied in cropping activities, while 22.5%
keep livestock. The main sources of potable
water supply include a windmill and a borehole while alternative sources, which are
16
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Fig. 6a. Left- Preparation of seed powder on a grinding stone. Fig. 6b. Right -Treating turbid
water with seed powder
Women have multiple preferences for water
supply sources, which are influenced by
availability of water from the sources during
different seasons, distance to the water
source and cost of buying water from potable sources. About 95-100% of the households interviewed obtain water from Suke
dam and charco dams, 20-60% fetch water
from traditional water holes and 10-22%
from the borehole located in Msange village
and windmill located in Mipilo village. Almost every day women are obliged to walk
from 2 km to more that 7 km to different
water sources (Fig. 5). The impacts of demanding household chores for women on
the socio-economic and health development
of rural communities have been reported by
Eliufoo & Marobhe (1998). Similarly, due to
acute scarcity of water supply in rural Nepal,
women are also compelled to walk with
pitchers on their backs from about 2 or 3 am
to 10 or 11 pm every day to water sources
(Kathmandu Post, 2000). The use of polluted water sources has been reported in
other rural areas such as in Trinidad and
Tobago, where households may or may not
treat such water before consumption (Welch
et al., 2000). The World Bank Water Demand Research Team (1993) mentioned
factors that influence a household’s willingness to use or pay for an improved supply,
which are also relevant to rural villages in
developing countries. These include the
socio-economic and demographic character-
istics of the household; the characteristics of
the existing or traditional source of water
versus those of the improved water supply;
households’ attitudes toward government
policy in the water supply sector and their
sense of entitlement to government services.
6.2.2 Traditional water coagulation: Procedures and performances
Women purify water fetched from charco
dams, which has average turbidities between
2250 and 5250 NTU and bacteriological
counts between 900 and 1500 faecal coliforms (FC) per 100 mL, using powdered
seeds from plants such as Vigna unguiculata
(VU), Voandzeia subterranea (VS), Arachis
hypogaea, Vicia faba, Parkinsonia aculeata (PA),
Zea mays and so on. The processes involved
in traditional water treatment (Fig. 6a and b)
are more or less similar to those performed
at conventional treatment plants and in jar
test experiments, in which rapid mixing
follows the dosing of water with the seed
powder or extract. The coagulated water is
then allowed to settle for about 25 minutes
before the clarified water is decanted and
stored cold in clay pots. The performance of
the various seeds as traditional natural coagulants including other traditional uses of
the seeds is shown in Table 4.
The coagulation efficiencies of different
seeds ranged from 83 to 89% and the
treated water was appealing for drinking by
17
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Table 4. The use pattern of seeds and water purification potential of seed powder
Traditional coagulant
Other local use apart from
treatment of drinking water
Dosage of seed
powder
(tablespoon/kg)
Residual
turbidity
(NTU)
Common
name
Field bean
Botanical
name
Vicia faba
Family
name
Fabaceae
Food stuff and cash crop
3
382 (83%)
Bambara
groundnut
Green gram or
cow peas
Voandzeia
subterranea
Vigna unguiculata
Fabaceae
Occasional food stuff
3
270 (88%)
Fabaceae
Rarely grown cash crop
4
225 (90%)
Groundnuts
Arachis
hypogaea
Fabaceae
Food seasoning; cash crop
2
247 (89%)
Jerusalem
thorn/jerry
bean/wonder
tree, mkeketa*
Wood
or
charcoal ashes
Parkinsonia
aculeata
Fabaceae
Seed husks and branches
are fuel wood; green beans
are eaten; shade tree
4
295 (87%)
Clarification of wash water
and rarely for drinking
0.5 – 1 kg
247 (89%)
Any
tree
species
-
*Vernacular name
the local people. Of the seeds used in purification of turbid water, PA seem to be a
suitable natural coagulant for appraisal
because unlike other types of seeds, it is not
a staple food for the people and it has mul
tiple beneficial uses. Diverse communities in
the world traditionally use different natural
materials extracted mainly from plant
sources as raw water additives to produce
drinking water (Suarez et al., 2005). Systematic studies have shown that among the
different plant-derived materials tested,
Moringa oleifera (MO) seeds are the most
effective natural coagulants (Jahn, 2001).
Laboratory studies have shown that MO
seeds are highly effective in coagulating and
removing suspended solids from water
containing medium to high initial turbidity
(Sutherland et al., 1989). They are also capable of aggregating bacteria (Madsen et al.,
1987; Ghebremichael et al., 2005) and therefore the flocculated microorganisms may be
removed by settling in the similar manner as
colloidal particles in properly coagulated and
flocculated water (Casey, 1997).
6.3 Effect of varying physical parameters on coagulation of river water with
crude seed extracts (Paper III)
6.3.1 Optimum dosage and seed powder
grain size effect
The optimum dosage of CSEs from seeds
for coagulation of river water with low (50
NTU), medium (205 NTU) and high (500
NTU) turbidity was 10, 30 and 60 mg/L for
VU and VS and 10, 20 and 40 mg/L for PA
(Fig. 7a and b). The CSEs demonstrated the
best performance with high turbidity water,
in which a turbidity removal efficiency of
92-98% was observed. The restabilisation of
destabilised colloidal particles, which was
associated with higher residual turbidities,
occurred at dosages above the optimal.
Similarly, Bhuptawat et al. (2007) observed
restabilization phenomenon during coagulation of synthetic turbid water using crude
extracts of MO seed as did Huang et al.
(2000) when using chitosan as a coagulant.
The dosages used traditionally by rural
women are very high, about 40-125 times
higher than the optimal dosages established
in this work. The proper application of seed
powder in purification of turbid water at
18
Water supply in Tanzania and performance of local plant materials in purification of turbid water
V.unguiculata
V.subterranea
P.aculeata
45
40
35
30
25
20
15
0
2
4
6
8
10
12
14
16
18
Dosage of coagulants (mg/L)
Residual turbidity ( FTU )
Fig. 7a. Top - Effect of seed
extract dosage on removal
of turbidity from water
with initial turbidity of 50
FTU. Fig. 7b. Bottom Effect of seed extract dosages on removal of turbidity from water with initial
turbidity values of 205 and
500 FTU.
Residual turbidity ( FTU)
50
400
350
300
250
200
150
100
50
0
V.unguiculata (205 FTU)
V.subterranea (205 FTU)
P.aculeata (205 FTU)
V.unguiculata (500 FTU)
V.subterranea (500 FTU)
P.aculeata (500 FTU)
0
10
20
30
40
50
60
70
80
Dosage of coagulants (mg/L)
household level will help villagers to save up
to 80% of the seeds per annum, and these
can be used for other purposes.
Moreover, coagulation of medium turbidity
water with CSEs of VU prepared from seed
powder with different grain sizes showed
that the finest (0.200mm<GS<0.212mm)
and
the
largest
grain
size
(0.425mm<GS<0.850mm) gave the lowest
residual turbidity of 19, and 20 NTU respectively, which comply with the Tanzania
Drinking Water Quality Standard (TDWS)
of 30 NTU. Similar trends were observed
for the finest and largest grain sizes of VS
and PA seed powder, for which the residual
turbidity was 21 and 25 NTU; and 23 and 26
NTU respectively. The best performance of
the crude extracts from the finest seed
powder could be due to its large total surface area, whereby most of the water-soluble
proteins are at the solid-liquid interface
during the extraction process (Hart, 2000).
This might have increased the concentration
of active coagulation polymer in the extract,
which improved the coagulation process.
6.3.2 Effect of raw water pH
The effect of pH on coagulation of raw
water samples with initial turbidity of 205
FTU using CSEs is shown in Figure8. It was
revealed that the performance of CSEs
improved significantly at acidic pH of raw
water samples regulated with C. aurantifolia
solution. The minimum residual turbidities
of 5 and 7 FTU were observed at pH 4.6
and 4.9 in raw water coagulated with optimal
dosages of CSEs of VU and VS respectively.
Similarly, the minimum residual turbidity of
10 FTU was seen at pH 4.6 of raw water
coagulated with CSEs of PA. Such residual
turbidities are very low compared with the
TDWS of 30 FTU. It has been observed
19
Nancy Jotham Mwaisumo Marobhe
160
Residual turbidity ( FTU )
Fig. 8. Effect of raw water
pH
regulated
by
C.aurantifolia on coagulation (dosage rates of seed
extracts shown in brackets).
TRITA LWR PhD Thesis 1042
140
120
No coagulant added
V.unguiculata (40 mg/L)
V.subterranea (30 mg/L)
P.aculeata (20 mg/L)
100
80
60
40
20
0
4
4,5
that the net surface charge of colloidal
particles is reduced at low pH and hence the
electrostatic repulsion between the colloids
and the thickness of the double layer is also
reduced (Bhuptawat et al., 1999). This suggests that efficient particle destabilization
and optimal flocculation occur at lower pH.
In contrast, Ndabigengesere & Narasiah
(1996) showed that pH did not influence
coagulation of kaolinite turbidity using MO
seed extract. Such an observation might be
due to the fact that synthetic kaolinite water
does not have other natural river pollutants
such as organic matter that influence the
coagulation process (Gregor et al., 1997). It
has been reported that the role of organic
polymers is to coagulate the organic-laden
particles in water (Bolto et al., 2001), hence
improving the floc formation process and its
settlement. Since C. aurantifolia fruit juice has
a bactericidal effect on gastrointestinal
pathogens (Dalsgaard et al., 1997), its application for treatment of drinking water by
rural households will help to minimise the
risks of contracting water-borne infections.
5
5,5
6
pH of raw water
6,5
7
7,5
did not influence the removal of turbidity.
High residual turbidities were observed
almost throughout the range of intensities
and durations of rapid and slow mixing
investigated. However, minimum residual
turbidities that ranged between 47 and 51
FTU were observed at the rapid and slow
mixing velocities of 150 RPM (G, 200 s-1)
and 40 RPM (G, 28 s-1), as well as at the
rapid and slow mixing durations of 5 min
(equivalent to the product, GT value of
7.5x104) and 30 min (GT 5x104). In conventional water treatment, rapid mixing and
slow mixing are essential to achieve complete mixing of the chemical coagulants and
to promote collisions between particles so
that flocs are formed (AWWA, 1989; Kiely,
1997). These residual turbidities were much
higher that those observed in the initial
coagulation experiments (29 FTU) when
both rapid and slow mixing speeds were
used sequentially for coagulation of raw
water with initial turbidity of 205 FTU using
VU. This suggests that both mixing conditions are essential for coagulation of turbid
water using natural coagulants. However, it
has been observed that the mixing intensity
needed for flocculation depends on the
particle concentration, which for tropical
river water has large variations. At low initial
turbidities, a higher turbulence level is required as particle spacing is relatively high.
Therefore, where large variations in the
turbidity of the water occur, adjustment to
the turbulence is necessary (McConnachie et
al., 1999).
6.3.3 Mixing speed and duration
In the studies on the effects of mixing speed
and duration on coagulation of raw water
samples with initial turbidity of 205 FTU
using CSE of VU, the intensity of rapid and
slow mixing was varied from 60 to 300 and
10 to 60 RPM while the mixing duration was
varied from 0.5 to 20 and 10 to 60 min
respectively. The results revealed that intensity and duration of rapid and slow mixing
when applied separately in water coagulation
20
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Table 5. Proximate chemical composition of the seed powder (%)
Taxon
Moisture
Fibre
Ash
Protein
Carbohydrate
Fat
Vi. unguiculata
10.8
5.1
4.0
23.7
56.4
1.4
P. aculeata
7.4
ND
4.6
39.73
ND
18.9
Vo. subterranea
9.2
4.9
2.8
16.2
60.7
4.9
ND denotes not determined.
Table 6. Purification of coagulation active components from VU and PA seeds by IEX matrix
and their coagulation activities
Coagulant name
Protein fractions
VU
Average concentration
(µg /mL )
PA
Coagulation
activity
(∆ O.D)*
Average concentration
(µg /mL )
Coagulation
activity
(∆ O.D)*
Unbound
proteins
720
0.63
960
0.58
Bound proteins
eluted by 0.3 M
NaCl
Bound proteins
eluted by 0.6 M
NaCl
840
0.91
480
0.85
420
0.79
380
0.77
*(∆ O.D)= O.D at time 0 – O.D at time 90 min.
ple using MO (Gassenschmidt et al., 1995;
Ndabigengesere & Narasiah, 1998; McConnachie et al., 1999); okra and nirmali seeds
(Al-Samawi & Shokralla, 1996) have used
water extraction methods and the CSEs
have high coagulation activities. The crude
extract of MO seed using salt solution
showed better coagulation activity at dosages
much lower than those needed for coagulation with crude water extract (Okuda et al.,
1999). However, Ghebremichael et al. (2006)
noted that crude salt extract of MO seed
significantly affected the IEX process and
very high dilution of crude salt extracts was
necessary to regulate the ionic strength to
the level of the equilibrating buffer.
Coagulation activities of protein samples
from the purification process are shown in
Table 6. The presence of coagulation activities in water samples treated with unbound
6.4 Purification and characterisation of
coagulant proteins (Paper IV)
6.4.1 Protein purification
The chemical composition of the seed
powder is presented in Table 5. The protein
contents in VU, PA and VS seeds were 23.7,
39.7 and 16.2% respectively. The presence
of such significant amounts of proteins
explains why these seeds are effective natural coagulants. The low fat content in the
seeds shows that no preliminary treatment is
required to remove oil from the seeds before
preparing the CSEs.
Coagulant proteins were purified from the
CSEs of VU (VUCE) and PA (PACE) by
simplified IEX chromatography. The crude
extraction of the coagulant agents from the
seed powder was carried out using water as a
solvent. Most coagulation studies, for exam21
Absorbance (500 nm)
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
V.unguiculata
Alum
1,6
1,4
1,2
1
0,8
0,6
0,4
0,2
0
0
2
4
6
8
10
Dosage (µg/mL)
12
14
16
VU - 0.3 M NaCl eluted
VU - 0.6 M NaCl eluted
PA - 0.3 M NaCl eluted
PA - 0.6 M NaCl eluted
Control
1,6
Absorbance (500 nm)
P.aculeata
Control
1,4
1,2
1
0,8
0,6
0,4
0,2
0
0
0,5
1
1,5
2
Dosage (µg/mL)
2,5
3
Fig. 9a – top; 9b bottom.
a. Coagulation activity of crude seed extracts and alum at different dosages.
b. Coagulation activity of purified protein samples of VU and PA at different dosages.
proteins of VU and PA shows that there are
different types of proteins or other organic
compounds in the seed that possess coagulation properties. Although the protein concentration in VU samples eluted by 0.3 and
0.6 M NaCl was higher than the similarly
eluted proteins in the PA samples, their
coagulation activities did not differ significantly. Therefore, for low-cost treatment of
drinking water for poor communities, a
single-step elution using a 0.3 M or 0.6 NaCl
could be appropriate. This simplifies the
purification procedure and avoids loss of
coagulant protein during two-step elution of
proteins. Further investigations to identify
the exact nature of VUP and PAP and the
mechanism of particle destabilisation are
necessary.
6.4.2 Characterisation
A rapid and simplified method that employed a small volume of sample was applied
for characterisation of purified proteins of
VU (VUP), PA (PAP) and CSEs in terms of
coagulation properties, thermal resistance,
floc settling rates and pH coagulation zones.
22
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Compared to the standard jar tests, this
method reduced the sample volume and
coagulant dosage and also allowed a large
number of experiments to be conducted
simultaneously, which reduced the time
needed for data acquisition.
6.4.2.1 Coagulation and floc settling
It was revealed that maximum coagulation
activities of VUP and PAP eluted by 0.3 M
and 0.6 M NaCl were achieved at the dosage
of 1 and 2 µg/mL, and 0.75 and 1.5 µg/mL
respectively. These dosages are 5 to 10 times
lower than those of the respective CSEs
(Fig. 9a and b), which suggests that the use
of pure proteins as coagulants may reduce
the costs of treating water as well as avoid
the release of organic and nutrient loads to
the treated water. The resulting coagulation
efficiencies after 90 min of settling time of
water treated with VUP and PAP were 88
and 87% respectively, compared with water
treated with CSEs, which was only 80%.
Similarly, alum demonstrated 84% coagulation efficiency at the optimum dosage of 7.5
µg/mL. The optimal dosages for coagulation of turbid water (250-300 NTU) with
MO crude extracts and MO coagulant protein (MOCP) are 15 and 5 µg/mL (Ghebremichael et al., 2004), which are quite
similar to those obtained here for purified
proteins and CSEs of VU and PA.
The floc settling studies of water coagulated
with purified proteins, CSEs and alum
showed that about 2-2.5 hr are required to
achieve 89-92% turbidity reduction of water
coagulated with VUP and PAP eluted by 0.3
and 0.6 M NaCl. Moreover, maximum
turbidity removal efficiency of 86% and 90%
was observed after 2 hr of settling time of
water treated with CSEs and alum respectively. The observed floc settling patterns of
VUP and PAP are very similar to those
reported for MOCP (Ghebremichael et al.,
2005).
The observed long settling time of water
coagulated with the seeds and alum possibly
supports our previous findings that both
rapid and slow mixing are needed for an
efficient coagulation process. In protein
characterisation studies, only rapid mixing
Fig. 10a. top, b. bottom
a. SDS–PAGE of PA seed crude extracts,
unadsorbed proteins and purified proteins. Lane 1 shows molecular weight of
marker (4-148 kDa); lane 2 MO proteins;lane 3 CSE of PA; lane 4 unadsorbed proteins of PA; lane 5 pooled
desalted fractions eluted by 0.3 M NaCl
from PA; lane 6 pooled desalted fractions
eluted by 0.6 M NaCl from PA.
b. SDS-PAGE of VU purified proteins
applied at different dosages of pooled
desalted fractions eluted by 0.3 and 0.6 M
NaCl. Lane 1 represents marker proteins;
lanes 2 and 3 show proteins eluted by 0.3
M NaCl; lanes 4, 5 and 6 show proteins
eluted by 0.6 M NaCl.
23
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
40 deg. cel. - 0.3 M eluted (VU)
80 deg. cel. - 0.3 M NaCl eluted (VU)
95 deg. cel. - 0.3 M NaCl eluted (VU)
40 deg. cel. (MO proteins)
95 deg. cel. (MO proteins)
40 deg. cel. - 0.6 M NaCl eluted (VU)
80 deg. cel. - 0.6 M NaCl eluted (VU)
95 deg. cel. - 0.6 M NaCl eluted (VU)
80 deg. cel. (MO proteins)
Coagulation activity
1,2
1
0,8
0,6
0,4
0,2
0
0
2
4
6
8
10
Dosage of proteins (µl/mL)
Coagulation activity
40 deg. cel. - 0.3 M NaCl eluted
80 deg. cel. - 0.3 M NaCl eluted
95 deg. cel - 0.3 M NaCl eluted
12
14
16
14
16
40 deg. cel - 0.6 M NaCl eluted
80 deg. cel - 0.6 M NaCl eluted
95 deg. cel. - 0.6 M NaCl eluted
1
0,8
0,6
0,4
0,2
0
0
2
4
6
8
10
Dosage of proteins (µl/mL )
12
Fig. 11a. Top - Coagulation activity of VU purified proteins heated at different temperatures: (40oC for 4 hr, 80oC for 2 hr and 95oC for 1 hr).
Fig. 11b. Bottom - Coagulation activity of PA purified proteins heated at different temperatures: (40 ºC for 4 hr, 80ºC for 2 hr and 95ºC for 1 hr.)
was employed to disperse the applied coagulants throughout the raw water to be treated.
VU and PA seeds have two or more coagulating proteins. Studies have also revealed
that more than one protein family with
coagulation activity is present in MO seeds
(Gassenschmidt et al., 1995). Current research on plant genomes show that plants
express many closely related proteins during
different developmental stages (Dong et al.,
2004. It is thus possible that VU and PA
produce variant peptides that are effective
coagulants. For treatment of water for rural
populations and other communities in developing countries, a highly pure protein is
not necessary and therefore a single-step
elution using 0.6 M NaCl would be suffi-
6.4.2.2 Electrophoretic patterns
The SDS-PAGE revealed that pure proteins
of VU and PA seeds eluted by 0.3 M and
0.6 M NaCl were eluted in an almost pure
state and gave single bands in the region
corresponding to a molecular weight of
about 6 kDa, which is closely similar to the
molecular weight of the purified MO protein
(Fig. 10a and b). From the general results of
electrophoretic mobilities and coagulation
properties of CSEs, unbound proteins and
purified proteins, it could be envisaged that
24
Water supply in Tanzania and performance of local plant materials in purification of turbid water
a. Pseudomonas spp.
(i) Control
b. Aeromonas spp.
(ii) VUP
(iii) PAP
(iv) CF
(i) Control
c. Bacillus spp.
(ii) VUP
(iii) PAP
(iv) CF
(i) Control
(ii) VUP
d. Acinetobacter spp.
(i) Control
(iii) PAP
(ii) VUP
(iii) PAP
(iv) CF
(iv) CF
Fig. 12. Flocculation of (a) Pseudomonas spp.; (b) Aeromonas spp.; (c) Bacillus
spp. and (d) Acinetobacter spp. by minimum effective dosages of 0.47 mg/mL VUP;
0.32 mg/mL PAP; and 0.5% CF.
hr, 80oC for 2 hr and 95oC for 1 hr. These
results are analogous to those of Conte et al.
(2007), which showed that the polycationic
proteins retained antibacterial activity on
several bacterial strains after autoclaving.
Therefore, it was suggested that the structure of the protein molecule rather than its
charge is important for the antimicrobial
activity and hence could be used in food
preservation. The observed heat tolerance of
our CSEs and purified proteins makes the
extraction and purification process of coagulant proteins much easier. In addition, the
storage conditions for the coagulant proteins
may be simple and convenient for rural
people in hot countries such as Tanzania,
where proper storage facilities are rare.
cient to recover almost all proteins bound to
the matrix.
6.4.2.3 Protein thermal tolerance
Extreme temperature is one of the most
important physical factors that denature
proteins. However, the CSEs of VU and PA
heated at 40oC for 5 hr retained coagulation
activities of 95% and 100% respectively.
Furthermore, heating the CSEs at 80oC for 2
hr and 95oC for 1 hr did not significantly
affect their coagulation activities. The purified proteins of VU (Fig. 11a) and PA (Fig.
11b) eluted by 0.6 M NaCl and pure protein
of MO seed retained coagulation activity of
87, 89 and 87; 94, 92 and 91; and 87, 82 and
78%, respectively after heating at 40ºC for 4
25
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
Absorbance (620 nm)
0,35
Fig. 13. Effect of pure
proteins of VU
(VUP), PA (PAP) and
Citrus fruit juice (CF)
on growth of different bacterial species:
0,3
0,25
0,2
0,15
Control
PAP (0.51 mg/L)
VUP (0.38 mg/L)
CF (0.4%)
0,1
0
50 100 150 200 250 300 350 400 450 500 550 600
Time (min)
Absorbance (620 nm)
13b - center - Aeromonas spp.
13c – bottom - Bacilllus spp. (c).
0,6
0,5
Control
VUP (0.75 mg/L)
PAP (0.88 mg/L)
CF (0.5%)
0,4
0,3
0,2
0,1
0
50
100 150 200 250 300 350 400 450 500 550 600
Time (min)
0,7
Absorbance (620 nm)
13a – top - Pseudomonas spp.
0,6
0,5
Control
VUP (0.56 mg/mL)
PAP (0.38 mg/mL)
CF (0.2%)
0,4
0,3
0,2
0,1
0
50 100 150 200 250 300 350 400 450 500 550 600
Time (min)
26
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Table 7. Counts of faecal coliforms in river water coagulated with pure proteins of PA (PAP)
and Citrus fruit juice (CF).
Time
(a) coagulation:
PAP - (3 mg/L)
[7.0]
(b) pH regulation
prior to coagulation:
PAP - (2 mg/L) +
0.3% lime juice
[6.46]
log10 FC count/100 mL
Settled and decanted water (b) [pH 6.46] + different
CF dosages
Dosage of CF added (% solution, V/V)/log10 FC
count/100 mL
0.1%
[5.90]
0.2%
[5.60]
0.3%
[5.21]
0.4%
[4.90]
0.5%
[4.79]
0.6%
[4.52]
0 min
4.9
4.9
3.39
3.39
3.39
3.39
3.39
3.39
30 min
3.9
3.39
2.23
2.23
2
1.65
1.41
0
2 hr
3.4
2.71
2.05
2
1.64
1.04
0
0
24 hr
3.5
1.83
1.72
1.49
1.23
0.78
0
0
Note: Values in square brackets are the pH levels produced after adding different dosages of
lime juice to water samples. The initial turbidity of water sample was 45-70 NTU, pH 7.25 and
alkalinity 61 mg /L as CaCO3.
Another merit of VU and PA coagulant
proteins is their wide pH range for coagulation activity. Significant coagulation activity
of VU and PA proteins occurred in the pH
range 5.5 to 8.5, compared with 6.5 to 9.5
for MO proteins.
the cells were incubated without proteins are
shown in Figure 12. Unlike the cells of the
other bacterial spp., the cells of Acinetobacter
flocculated even in the absence of the proteins. Broin et al. (2002) observed that recombinant protein from MO seeds aggregated both Gram-positive and Gramnegative bacteria. Casey (1997) reported that
in properly coagulated-flocculated water,
flocculated microorganisms may be removed
by settling in a similar manner to colloidal
particles. Therefore, the ability of bacteria to
aggregate enhances the settlement and the
clarification of turbid water treated with
coagulants (Finch & Smith, 1986). The
flocculent activity of coagulant proteins and
CF could be attributed to antimicrobial
properties of the peptides that are present in
almost all plant organs (Broekaert et al.,
1997).
The results of the growth inhibition studies
on Pseudomonas, Aeromonas and Bacillus cells
by VUP, PAP and CF are shown in Figures.
13a, b and c respectively. The minimum
dosages of 0.38 and 0.51 mg/L; 0.75 and
0.88 mg/L; and 0.56 and 0.38 mg/L inhibited the growth of Pseudomonas, Aeromonas
and Bacillus cells after 2-4 hr of incubation
6.5 Antimicrobial activity on tropical
river water bacteria (Paper V)
Water-borne diseases are widespread in
urban and rural areas of developing countries due to drinking water of inferior quality. Analysis of the 16s rRNA gene sequence
together with morphological and biochemical characterisation of 126 bacterial strains
isolated from river water showed that the
river is polluted with pathogenic and opportunistic bacteria including strains that belong
to Vibrio, Pseudomonas, Bacillus and Acinetobacter spp.
Similarly, Zamxaka et al. (2004) found that
the domestic water supplies in rural areas of
the Eastern Province, South Africa, are
polluted mainly with human intestinal pathogens. The effects of flocculation on Pseudomonas, Aeromonas, Bacillus and Acinetobacter
cells after incubation with VUP, PAP and
CF in comparison to the control in which
27
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
with VUP and PAP respectively. These
results are in agreement with Izadpanah &
Gallo (2005), who demonstrated that the
molecules with antibacterial activity are
mainly positively charged peptides. The pure
proteins used in this study were also characterised as cationic proteins. Resumption of
growth of Bacillus cells after 4 hr of incubation could be attributed to the resistance of
bacterial endospores to seed proteins. Differences in cell wall composition could be
among the reasons for the variation in antimicrobial activity of VUP and PAP on
various bacterial spp. (Ghebremichael et al.,
2005). Moreover, the growth of bacterial
cells was inhibited remarkably after incubation with CF at the minimum dosage of 0.20.5%. This could be due to the fact that
acidic consumables possess protective properties against enteric pathogens (Mujica et al.,
1994). This shows that CF could be very
useful for post-disinfection of water treated
Fig. 14a. Top - Effect
of crude extracts of VU
(VUCE) and PA (PAP)
seeds on Fe2+, NO3and PO43- concentrations in treated water.
Concentration (mg/L)
40
35
VUCE (ferrous ion)
30
VUCE (phosphate)
25
VUCE (nitrate)
20
PACE (ferrous ion)
15
PACE (phosphate)
10
PACE (nitrate)
5
0
Concentration ( mg/L)
0
20
40
60
80
Dosage of coagulants (mg/L)
100
Fig. 14b. Center Effect of proteins of
VU (VUP) and PA
(PAP) and alum on
Fe2+, NO3-and PO43concentrations in
120 treated water.
40 PAP (ferrous ion)
PAP (phosphate)
PAP (nitrate)
35
30 ALUM (ferrous ion)
ALUM (phosphate)
ALUM (nitrate)
25
20
15
10
5
0
0
2
4
6
8
10
Dosage of coagulants (mg/L)
12
28
14
16
Fig. 14c. Bottom Appearance of charco
dam water coagulated
with different dosages
of crude extract of PA
(PACE). From left to
right are raw water
samples (NTU)
treated with increasing
dosage of PACE.
Water supply in Tanzania and performance of local plant materials in purification of turbid water
Sludge volume (ml/L )
with proteins prior to drinking, especially in
poor households where drinking water is
stored under unhygienic conditions.
Moreover, it was of interest to study antimicrobial effects of PAP and CF on faecal
coliforms
(FC)
during
flocculationcoagulation of the river water. Table 7
shows the faecal coliforms counts in Ruvu
River water samples coagulated with PAP
and CF. The results showed that a marked
reduction in faecal coliform count occurred
in water samples in which the pH was lowered to less than 5.6 using CF prior to coagulation. When PAP was used as coagulant
without lowering the pH of raw water samples, it reduced faecal coliforms by 89% and
96% after 30 min and 2 hr of settling time
respectively. For the water samples in which
the pH was regulated to pH 6.46 before
coagulation with PAP, the reduction in
faecal coliforms count was 97% and 99.3%
after 30 min and 2 hr of settling time respectively. Exposure of faecal coliforms to water
samples with pH between 4.79 and 4.52 for
more than 2 hr was accompanied by complete destruction of faecal coliforms in the
treated water. The treated water samples
were all palatable and the pH levels in the
settled water remained stable throughout the
experiment. Studies by Dalsgaard et al.
(1997) showed that exposure of V. cholera
strains to 1% Citrus juice (pH 4.4 and 4.5)
for two hours caused a 5- log reduction to
less than 100 CFU/mL of tap water.
6.6 Physico-chemical quality (Paper VI)
Coagulation of charco dam water with coagulant proteins reduced most of the water
pollutants analysed to levels that complied
with Tanzanian local standards for drinking
water and in some cases the WHO standards
were achieved. The residual turbidity of water
treated with purified proteins and CSEs was
reduced from 800 NTU to the range of 3-13
and 3-19 NTU respectively. The CSEs and
purified proteins did not affect the pH of the
treated charco dam water, which was maintained within the range 6.9-7.4. This implies
that the use of natural coagulant proteins in
water treatment processes avoids the need for
extra additives to regulate the pH of the
treated water. The concentration of Fe2+,
NO3- and PO43- in water treated with CSEs
(VUCE and PACE) and purified proteins
(PAP) were reduced from an initial 21.1, 33.3
and 7.5 mg/L by 98.1%, 99.6% and 94.4%;
98.5%, 99.2% and 91.5% and 89.6, 87.7 and
45.3 % respectively (Fig. 14a and b). The
removal of iron in the treated water is very
important for the villagers because water
from most charco dams contains high concentration of Fe2+, which cause the water to
appear reddish brown (Fig. 14c). These results are analogous to those reported by
Sajidu et al. (2005), which demonstrated that
treatment of wastewater with MO seed kernel
removed up to 92.14% of Fe2+. The most
probable mechanism for removal of Fe2+ is
complete aeration of water samples during
coagulation–flocculation process, resulting in
the formation of iron precipitates that settled
along with the flocs of colloidal particles.
Unlike CSEs, the purified proteins reduced
organic load in the treated water by 71-75%,
which improved the shelf-life of the treated
water. Although the proteins eluted with 0.6
M NaCl increased the conductivity of the
treated water significantly, the water was
palatable.
6
5
4
3
2
1
0
VUCE
PACE
Coagulants
ALUM
Fig. 15. Sludge volumes produced by
VUCE, PACE in comparison to alum at
optimal dosages for coagulation of river
water (205 NTU). The optimal dosages
were 30 mg/L for VUCE; 20 mg/L for
PACE and 25 mg/L for alum. The drop
lines are SD based on three analyses.PACE and 25 mg/L for alum. The
drop lines are SD based on three analyses
29
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
However, elution of proteins with low
concentration of salt solution could be
advantageous. The use of these traditional
coagulants, especially the purified proteins,
for treatment of turbid water sources will
help to improve health and hygiene conditions of rural populations. It is estimated
that less than 2 USD would be required by
poor communities to purify 1 m3 of turbid
water using PAP.
The volumes of sludge produced from river
water samples with initial turbidity of 205
NTU coagulated with optimal dosages of
VUCE, PACE and alum are shown in Fig.
15. VUCE and PACE produced 1.6 and 2.1
ml/L of sludge respectively, while alum
produced 4.5 ml/L, which is about 2 to 3
times higher than the volume produced by
the natural coagulants. Ndabigengesere and
Narasiah (1998) also observed that the crude
extracts of MO seeds produced a sludge that
was 4-5 times lower than that produced by
conventional alum. Moreover, using natural
polyelectrolytes in the drinking water treatment process can increase the settling rate,
reduce costs for sludge handling and improve the finished water quality (Kawamura,
1991). From the rural population point of
view, the sludge could be used as a fertiliser.
Since the seeds that we used as natural
coagulants are also food materials, we assume that the sludge will be suitable for
plant growth.
polluted sources that are far from the home.
The drinking water is purified using locally
available plant seed powder. Rural women
lack knowledge for improving the performance of the seed powder and hence they
rarely obtain good clarification results.
Endemic cholera in the country is partly
attributed to consumption of water of inferior quality.
Laboratory studies on performance of crude
seed extracts (CSEs) and purified seed
proteins from Parkinsonia aculeata (PA), Vigna
unguiculata (VU) and Voandzeia subterranea
(VS) plants as natural coagulants and Citrus
fruit juice (CF) juice as either an additive or
a biocide during coagulation of water samples confirmed their effectiveness in water
clarification. The PA and VU seed proteins
were purified from CSEs using simple and
straightforward ion exchange (IEX) chromatography that could be easily scaled up using
locally available facilities. Characterisation of
purified proteins by SDS-PAGE showed
that they are small proteins with molecular
weight closely similar to that of purified
Moringa oleifera (MO) coagulant protein. In
addition, the purified proteins, CSEs and
MO proteins are thermotolerant and have a
wide pH range for coagulation, properties
that simplify the extraction and handling of
the purified proteins.
The CSEs, purified proteins, and aluminium
sulphate (alum) showed high coagulation
activity although purified proteins were
effective at much lower dosages than CSEs
and alum. The removal of turbidity by coagulant proteins was associated with a significant reduction in concentration of other
inorganic pollutants to levels in line with
Tanzania drinking water quality standards.
Unlike CSEs, the purified proteins did not
impart an organic load to the treated water
and produced less sludge than alum. The use
of coagulant proteins avoids the need of
application of other water additives to regulate pH and alkalinity, which is not the case
for alum.
The pure proteins and CSEs of VU and PA
showed antimicrobial effect against bacteria
isolated from river water. They flocculated
and inhibited the growth of both Gram-
7 CONCLUSIONS AND
RECOMMENDATIONS
Despite significant investment in water
supply projects, a large proportion of the
population in urban and rural areas of Tanzania are facing acute water supply problems. This is due inter alia to lack of coherent
action by water authorities and communities
to address social, technical, operation and
maintenance, management and financial
issues. The urban water supply is characterised by ageing and worn-out structures,
intermittent and inadequate supply, poor
water quality, low tariffs, poor customer
management and uncontrolled water leakages. The rural areas suffer most from water
supply problems and a large population use
30
Water supply in Tanzania and performance of local plant materials in purification of turbid water
8 AREAS FOR FURTHER
RESEARCH
positive and Gram-negative bacterial cells.
The CF showed high antibacterial effect and
hence could be useful for post-disinfection
of water treated with proteins prior to drinking in rural areas and urban areas where
people who do not have a safe drinking
water supply.
It is recommended that the use of natural
coagulants for water treatment should not
be taken as a panacea for water supply
problems in Tanzania, but rather as one of
several means for improving the water
supply services in Tanzania. Rural women
could improve the performance of the CSEs
by using minimum dosages, adequate mixing
and settling time of treated water for maximum turbidity removal. Lime or lemon juice
could also be used for disinfecting clarified
water prior to consumption. Furthermore,
the low cost water lifting facilities that do
not involve significant human energy and
time should be developed. To increase the
water security of rural households, multiple
water sources should be utilised depending
on the season and geographical location,
provided proper treatment is applied.
The results from this study are far from
complete. The implications of this study
could be better understood through further
research into Tanzanian natural coagulants
at a large scale for the benefit of rural households and the water industry at large. This
implies that:
- Large-scale production of coagulant proteins using the simple protein purification
method and locally available facilities is
necessary. Other simple extraction methods
for coagulant proteins also should be developed.
- Specific antimicrobial studies of VU and
PA proteins on other enteric pathogens
including the mechanism of action are an
important area for further investigations.
Further characterisation of coagulant proteins might also provide new dimensions for
understanding the nature and functions of
coagulant proteins.
- The potential for large-scale production of
the seeds and lime or lemon for domestic
use and water treatment is necessary. In
particular, the potential of Parkinsonia aculeata, as a useful multipurpose tree for dry
areas of Tanzania should be explored.
31
Nancy Jotham Mwaisumo Marobhe
TRITA LWR PhD Thesis 1042
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