KompetenzZentrum Wasser Berlin
The Research Project “Natural and Artificial Systems for Recharge
and Infiltration (NASRI)”, its Relation to the Specific Water
Management Challenges of Berlin and the International Relevance
Martin Jekel*, Bernd Heinzmann**
*Technische Universität Berlin, FG Wasserreinhaltung, Strasse des 17. Juni 135, D-10623 Berlin
(e-mail: [email protected])
**Berliner Wasserbetriebe, Cicerostraße 24, D-10709 Berlin
(e-mail: [email protected])
Abstract
Bank filtration and groundwater recharge are in use for drinking water preparation for
more than hundred years, mostly in Central Europe. The underlying philosophy is
based on the experiences and rules, that well-protected groundwaters out of the
natural water cycle are the best available resources for a water supply, with little or
no treatment required. This principle can be maintained if surface waters of variable
and poor quality are needed to provide sufficient drinking water in densely populated
areas, like in urban regions and if the natural purification processes of soil and water
are used intentionally.
Berlin is a good example of this principle and its history, as about 70 % of the
pumped groundwater originates from surface waters, either by bank filtration or
artificial recharge. The surface waters are impounded river lakes or lakes with quality
problems due to eutrophication and the discharge of well-treated domestic
wastewaters. In the latter case, an indirect and partial water reuse cycle is
established.
The large research program NASRI was developed to study in detail all relevant
processes in bank filtration and groundwater recharge concerning the
hydrogeological conditions and the chemical and microbiological quality. The
outcomes will be a sound basis for optimized operation of existing sites and for the
integrated design of new field sites all over the world. The inclusion of these natural
treatment steps in surface water supply systems and for indirect portable reuse has
great potentials in locations with feasible hydrogeological conditions, avoiding or
reducing the need for advanced technical treatment.
I.
Introduction
Bank filtration, that is the abstraction of superficial groundwater in the proximity of
and originating from a nearby surface water, has long been used for drinking water
preparation. Namely in Germany this technique is being used widely and it provides
about 16% of the raw waters used for drinking water preparation [Kühn and Müller,
2000]. In particular, river bank filtration has a long tradition along the river Rhine
[Sontheimer, 1980] and the river Elbe [Grischek et al., 2001]. Very recently, bank
filtration meets growing interest worldwide as a (pre-)treatment technology in drinking
water preparation that may be equally sustainable and cost effective, for example in
the United States [Tufenkji et al., 2002]. Its importance on a global scale is expected
to grow in as much, as groundwater resources decline and water demand continues
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to increase. Similar arguments are applicable for artificial groundwater recharge by
either surface percolation or aquifer injection.
The quality of raw water obtained by bank filtration or artificial recharge depends
strongly upon the quality of surface waters, the hydrological and (hydro-)geochemical
conditions of the subsurface the residence time and the travel distance of the
infiltrated waters. Moreover, the river sediment or aquifer material may significantly
influence the groundwater quality [Doussan et al., 1997]. Physical processes
(filtration, mixing. dilution), physico-chemical and chemical processes (dissolution
and precipitation, ion-exchange, adsorption, hydrolysis, surface reactions) and
biological processes (transformation, oxidation and mineralization, reduction) alter
the quality of the former surface water during passage of the subsurface [Kühn and
Müller, 2000]. Moreover, bank filtration may act as a barrier against shock loads of
contaminants, e.g. from accidental spills of chemicals into river waters [Malle 1994;
Kühn and Müller, 2000].
Several beneficial effects of bank filtration and groundwater recharge have been
reported, among them reductions in COD, BOD, DOC and AOC [Kühn and Müller,
2000], a reduction of the content and an improved treatability of humic matter
[Gerlach and Gimbel, 1999], reduction of microbes [Miettinen et al., 1997], removal of
viruses [Havelaar et al., 1995], and removal of trace organics (AOX), [Kühn and
Müller, 2000], EDTA, certain naphthalene sulfonates, some pharmaceutically active
substances (PhACs) [Sacher et al., 2001], fragrances and aromatic hydrocarbons
[Juttner , 1999]. However, removal of trace organics may be not complete or absent
[Kühn and Müller, 2000] and infiltration of water via a river bank or recharge system
may become a source of groundwater contamination with trace organics [Mathys,
1994].
Despite considerable experiences with the use of (river) bank filtration and artificial
recharge in Germany [Jülich and Schubert, 2001] and the Netherlands [Hiemstra et
al., 2001], present knowledge upon the processes occurring during bank filtration and
recharge and their effects on water quality is incomplete, site-specific and
characterized by a 'black box'-approach. This limited understanding hampers:
the assessment of raw water quality obtainable as function of system
parameters at these sites,
the optimization of existing bank filtration and recharge processes,
identification of surface water quality problems that cannot be eliminated by
bank filtration and recharge,
forecasts of the future development of bank filtration and recharge, namely
under changing environmental and operational conditions,
assessment of the role of bank filtration and soil-aquifer-treatment in partially
closed water cycles,
the identification of potential new sites suited for bank filtration and recharge.
Thus, a concerted research action such as NASRI will improve the understanding of
bank filtration and artificial recharge as a prerequisite for the future development of
these natural and multi-barrier technologies.
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II. The Berlin Situation
Bank filtration and recharge have always been important factors in the public water
supply of the City of Berlin, which started in the second half of the 19th century with
water works close to the River Spree, Lake Tegel and Lake Müggel. Until today, bank
filtration and groundwater recharge are unevitable components of the water supply,
as all drinking water originates from local sources. About 70 % of the 220 million m3
per year of drinking water originate from bank filtration and water infiltration. All raw
waters, taken from the aquifers, are aerated and passed through rapid sand filtration
for removal of iron and manganese. There is no further treatment, neither for the
removal of organic matter nor for disinfection prior to the distribution of the drinking
water. Thus, a proper functioning of the natural filtration steps is essential to maintain
the high drinking water quality in Berlin.
Water bodies and their use particularly for water supply
Approximately 6 % of the surface area of Berlin consists of freshwater (see figure 1):
lakes (e.g. Schlachtensee), river lakes (e.g. Tegeler See, Müggelsee, Wannsee),
rivers (e.g. Panke, Wuhle, Erpe), regulated rivers (e.g. Spree, Havel and Dahme) and
canals (e.g. Landwehrkanal, Teltowkanal). The flow rates through Berlin are low and
unsteady and for the river Spree decreasing, caused by the closure of upstream
lignite mines, which pumped until 1990 approximately 1 billion m3/year of water into
this river. This leads to high proportions of treated wastewater in the receiving water,
longer detention times of the surface water in our regulated rivers and increasing
problems with the water quality.
The water bodies are intensively used for different purposes. For the population of
the region the water bodies have a high recreational value. They are used
economically for inland fishery and as waterways and are very important for the water
supply – providing the resource for drinking water from bank filtrate and for the
recharge of groundwater. In addition, the water bodies are recipients for treated
sewage and storm water from separate systems and for overflows of the combined
sewer system.
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Figure 1: Map of water bodies, water works and treatment plants in the Berlin region
Conditions and principles of water supply in Berlin
The sandy soil and underground of the region provides favourable hydro-geological
conditions for water supply. Bacteria, viruses and other pathogens are eliminated
during the subsoil passage. As a consequence the western part of Berlin has been
able to sustain its own water supply for several decades based on these following
principles of water supply:
•
•
•
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The resources consist exclusively of groundwater, including natural and
artificial recharge and bank filtered water. The quantity of bank filtered water
alone is about 56 %. The fresh water aquifer in Berlin is quite shallow.
Beneath an impermeable till layer a huge salty groundwater reservoir is found.
In several parts of the city the aquitard between the fresh water and the saltwater aquifer has holes were salt water is upcoming. The water works have to
balance very carefully their pumping regime in order to avoid salt-water
intrusion into the fresh water aquifer. No surface water is used directly.
Artificial groundwater recharge is an important part of water resources
management in the Berlin region. With an average precipitation of 600 mm/a,
the natural groundwater recharge rate of up to 200 mm/a is not enough to
maintain the groundwater level in all parts of the city.
The water supply system incorporates a simple drinking water treatment:
water intake - aeration - manganese and iron removal - filtration.
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•
•
•
•
A close-to-natural water treatment process without chemicals can be
maintained.
No disinfection of the drinking water is required, but provisions of a careful
maintenance of the water-pipe network is necessary.
The water supply is provided from the regions own resources, including the
rivers in the city area.
In order to meet quality standards stringent precautionary measures for the
water resource management (groundwater and surface water) are
implemented.
Water pollution by discharged wastewater, storm water and combined sewer
overflow
Approximately 668,800 m3 per day of treated municipal wastewater
into the water bodies of the Berlin region in 2001. As a result of
treated wastewater the water bodies are loaded with the nutrients
nitrogen, bacteria and pathogens, residual organic compounds,
biodegradable trace substances plus dissolved salts.
were discharged
the discharge of
phosphorus and
particularly non-
The concentrations and the load of several constituents of urban storm water from
the separate sewer system can be quite high [Heinzmann, 1994]. The quantity of
annual storm water discharge into the water bodies of Berlin is estimated to be at
about 60 million m3 for a mean annual quantity of precipitation of approximately
600 mm.
The quantity of combined sewer overflows at pumping stations is approximately 1
million m3 per year and of storm water tanks approximately 3 million m3 per year. The
total quantity of combined sewer overflow is estimated at approximately 7 million m3
per year.
The pollution of the rivers from their catchment’s areas and of the discharges of
treated wastewater and storm water from the combined and separate sewer system
of the Berlin region have overall a negative impact on the water bodies in view of
water supply and drinking water quality:
• Eutrophication is the main problem: algae growth especially cyanobacteria
species with associated high concentrations of algae toxins.
• Stable organic trace substances are present in treated wastewaters and in
receiving surface waters, entering locally into a partially closed water cycle.
III. Aims, Tasks and Projects of the Research Program NASRI
As outlined above, there is a clear need to understand and quantify the purification
processes in bank filtration and groundwater recharge for those anthropogenic
pollutants, which are difficult to avoid at the source and which pass through the
wastewater treatment plants. Previous limited field and laboratory studies were not
sufficient to draw the necessary conclusions for the suitable design and optimal
operation of both important treatment and storage processes, using natural
mechanisms and long retention times to a wide extent.
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This research program covers traditional as well as novel requirements of drinking
water preparation, that evolve from microbiological as well as chemical loads of
surface waters and which are to some extent, caused by the considerable portion of
municipal wastewater in the surface waters of Berlin.
-
The provision with hygienically safe drinking water, that is free from pathogens
was one of the driving forces of public water supply and drinking water
preparation. Recent reports outlined, that the removal efficiency for bacteria
and viruses previously attributed to a soil or underground passage is not
provided in all cases. The reasons for that are, however, yet unknown. As the
surface water used for bank filtration is always more or less faecally
contaminated, water hygiene remains an issue of investigation.
The growth of cyanobacteria in eutrophic surface waters and the release of
cyanobacterial toxins (i.e. ‘cyanotoxins’) is usually seen as a problem of
bathing water quality. However, the indirect use of surface water for drinking
water preparation calls for a complete removal of cyanotoxins in bank filtration
and recharge, of which the microcystins have been shown to be the most
relevant group for Berlin
In recent years, polar and poorly degradable organic pollutants are gaining
increasing attention as a factor of water quality. Industrial chemicals as well as
household products, certain pesticides and their polar metabolites and
pharmaceutically active compounds are among these polar pollutants.
These compounds are not necessarily removed in wastewater treatment and
in drinking water preparation processes.
Dissolved organic matter levels may also increase in partly closed water
cycles as effluent organic matter and algal products add to the relatively high
natural (groundwater) background. DOC removal in bank filtration is of
particular importance when drinking water disinfection has to be performed
and biological stable water is distributed without disinfection.
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The hydrogeological and hydrodynamic conditions are only partly
investigated, especially close to the infiltration zones and clogging layers.
Those will be of decisive importance for the permeability, the establishment of
redox potentials and the removal of substances and microorganisms. An
integrated modelling for bank filtration and recharge sites is essential to
predict future changes of water quantity and quality.
This interdisciplinary project “NASRI” is carried out from the Centre of Competence
for Water Berlin (KWB gGmbH) together with a consortium, which consists of seven
groups from five institutions residing in Berlin. Vivendi Water and the Berlin Water
Company (BWB) are sponsoring this three-year research program until 2005.
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Projects and Teams:
Name of the Research Project
Responsible research team
Retention and elimination of cyanobacterial
toxins (microcystins) through bank filtration
Dr. I. Chorus, Dr. H. Bartel
Umweltbundesamt (UBA), Section water
Treatment
Dr. Th. Heberer, Technical University of
Berlin, Institute of Food Chemistry
Occurrence and fate of drug residues and
related polar contaminants during bank
filtration
Organic substances in bank filtration and
groundwater recharge - process studies
Using bacteriophages, indicator bacteria,
and viral pathogens for assessing the
health risk of drinking water obtained by
bank filtration
Intergraded modelling concepts for bank
filtration processes: coupled groundwater
transport and biochemical reactions
Hydrogeological-hydrogeochemical
processes during bank filtration and
groundwater recharge using a multi- tracer
approach
Data management, chemical analysis and
application of models
Prof. Dr. Jekel, Technical University of
Berlin, Department of Water Quality
Control,
Dr. J. Lopez-Pila, Dr. R. Szewzyk,
Umweltbundesamt (UBA), Section water
hygiene
Prof. Dr. G. Nützmann, Institute of
Freshwater Ecology and Inland Fisheries
and Humboldt-University of Berlin (IGB)
Prof. A. Pekdeger, Free University of
Berlin, Institute of Geochemisty,
Hydrogeology and Mineralogy
E. Wittstock, H. Dlubek, Dr. Uwe
Dünnbier, Andreas Deffke Berliner
Wasserbetriebe (BWB)
The partners come from academia (Technical Unversity of Berlin, Free University of
Berlin), from governmental institutions (Federal Environmental Agency) and a publicly
funded research institute (Leibniz-Institute of Freshwater Ecology and Inland
Fisheries). The Free University is supported by two public research institutes, the
Alfred-Wegener Institute and the Geoforschungszentrum (both at Potsdam). The
Berlin Water Works (Berliner Wasserbetriebe) complete this consortium. All partners
have previously been involved in research related to bank filtration or groundwater
recharge in the Berlin area and they have gathered expertise in all fields required for
a comprehensive investigation and understanding of bank filtration.
The general aims of the NASRI-Program are:
• to ensure the long term sustainability of the groundwater resource in Berlin
and drinking water quality through the bankfiltration and recharge processes.
• to expand the Know-How and quantify the relevant processes.
• to obtain quantitative and qualitative guidelines for the proper design and the
optimised operation of existing bankfiltration schemes and transferability of
these guidelines ( use of “models”, etc)
• generalisation of these models by integration of local compartment models to
regional groundwater quality and flow models. Implementation in Berlin area,
at first.
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Detailed research aims are as follows:
•
a better understanding of the physical, chemical and biological processes
occurring in the clogging zone.
•
a better understanding of the transport processes (degradation, transformation
and transport) especially of:
à organic compounds and trace organics
à pharmaceutical residues
à microbiological parameters (ie.viruses, bacteria)
à algae toxins
•
•
•
•
•
•
a statement on the long term sustainability of bankfiltration and the resulting
consequences and measures to be taken at the source (identification of critical
contaminants in the groundwater cycle in order to prioritise an upstream
removal policy).
Modeling of transport processes (water/soil exchange models and kinetics)
Definition of water managing scenarios (ie. increase in sulfate concentrations
in the surface water)
Guidelines for the optimised operation of existing bank filtration and
groundwater recharge schemes and their specific advantages and
disadvantages
Transferability and application of results worldwide (model development)
Integration and evaluation of previous studies and results
IV. Research Facilities and Field Sites
The facilities and field sites available in Berlin are ideally suited to study the complex
interactions of hydrogeology, geochemistry, aquatic biology and chemistry in different
scales of bank filtration and recharge, from laboratory level via pilot-plant units to
semi-technical facilities and up to the chosen field locations at the lakes of Tegel and
Wannsee.
Lake Tegel is a mesotrophic surface water with considerable influence from treated
domestic wastewater, with a special treatment plant for the influent water to the lake
to remove phosphorus. Lake Wannsee is more eutrophic with more intensive algae
blooms, but receives also treated domestic wastewater. Both lakes can be compared
with the Lake Müggel (and its operating bank filtration) with no influence of domestic
wastewater, however with eutrophic conditions. This latter lake is not investigated in
NASRI.
Field sites:
• Transects on Lake Tegel (eastern bank) to the productions wells of the water
treatment plant tegel.
• A groundwater recharge site at Lake Tegel, replenishing groundwater nearby.
• Two transects at Lake Wannsee (eastern bank) for bank filtration
These locations were equipped with up to 60 monitoring wells in total, with the major
portion in the regular sampling schedule.
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Semi-technical facilities:
These are located at the research station of UBA, a partner in NASRI and include
infiltration basins with enclosures, a artificial lake bank filtration and large soil
columns for aquifer simulations. The plant sizes allow for spiking of raw waters with
microorganisms and organic substances for stationary concentrations in realistic
water matrices.
Laboratory and Pilot-size systems:
These are established in the institutions of the NASRI-consortium and include small
and short soil columns for studies on redox potentials and other influential
parameters with spiked raw waters or any quality.
V. International Relevance
The increasing world-wide interest in bank filtration and artificial recharge is related to
subsequent developments and aspects in water resource management and water
supply:
Water treatment of surface waters:
The presence of various biological and chemical constituents of concern in surface
waters and the need for more advanced water treatment processes (activated
carbon, ozone, membranes) to produce a safe drinking water provide strong
arguments for alternative approaches with options for lower costs and a better, more
reliable treatment performance. Namely, two fields of concern are discussed: the
troubles with parasites (Giardia, Cryptosposidium) even in relatively clean surface
waters and the formation of halogenated and other disinfection byproducts in the
finished drinking water out of organic precursor material. Bankfiltration and
groundwater recharge offer here promising chances to avoid the microbiological
problems and to limit (or even avoid) the disinfection byproducts.
The existing and long-term field experiences in Central Europe, including the case of
Berlin, indicate strongly, that either way of underground treatment, if designed and
operated properly, offers great potentials for the future in integrated water resource
management, provided that suitable hydrogeological conditions are present in the
vicinity of the water use area.
Indirect Water Reuse:
In arid and semi-arid regions with stressed water resources, water reuse including
the use of underground aquifers is a viable and proven option for indirect subpotable
and potable water reuse to augment public or private water supplies. Full-scale
examples operating for decades are found in Israel and the South-West of the United
States, where treated domestic wastewater is either recharged by open percolation
basins (soil-aquifer-treatment, SAT) or treated by advanced techniques and injected
directly into confined aquifers. Recent extensive studies in the USA and Australia
indicate the reliable and sustainable treatment efficiencies for important quality
parameters. However, some organic trace pollutants, a part of the natural organic
matter (NOM) and dissolved salts remain present in the recharged water even after
years of residence time, while the microbiological quality is improved greatly, up to
the level and naturally formed groundwater.
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The ongoing discussions on this mode of indirect reuse are concerned with the level
of pretreatment before recharge, the minimum residence time in the aquifer, the
maximum mixing ratio reclaimed water in the pumped groundwater, the necessity of
post-treatment before potable supply and with the associated health risks.
References:
[1]
Changes in water chemistry with emphasis on nitrogen species. J. Contam. Hydrol. 25, 129 - 156.
[2]
Gerlach M and Gimbel R. (1999) Influence of humic substance alteration during soil passage on
their treatment behaviour. Water Sci. Technol. 40 (9), 231 - 239.
[3]
Grischek T., Worch E. and Nestler W. (2001) Is bank filtration under anoxic conditions feasible?
In: Proceedings of the International River Bank Filtration Conference (Jülich W. and Schubert J.,
Eds.), IAWR Rheinthemen 4, 57 - 65.
[4]
Havelaar A.H., Vanolphen M. and Schijven J.F. (1995) Removal and inactivation of viruses by
drinking water treatment processes under full-scale conditions. Water Sci. Technol. 31 (5-6), 55 62.
[5]
Heinzmann, B. (1994) Beschaffenheit und Bedeutung städtischer Regenabflüsse im
Trennsystem. gwf-Wasser/Abwasser 135, Nr. 7, S. 381 - 390.
[6]
Hiemstra P., Kolpa R.J., van Eekhout J.M.J.M., van Kessel T.A.L., Adamse E.D. and van
Paassen J.A.M. (2001) Natural recharge of groundwater: bank filtration in the Netherlands. In:
Proceedings of the International River Bank Filtration Conference (Jülich W. and Schubert J.,
Eds.), IAWR Rheinthemen 4, 67 - 79.
[7]
Jülich W. and Schubert J., Eds. (2001) Proceedings of the International River Bank Filtration
Conference, IAWR Rheinthemen 4, 309 p.
[8]
Juttner F. (1999) Efficiacy of river bank filtration for the removal of fragrance compounds and
aromatic hydrocarbons. Water Sci. Technol. 40 (6), 123 - 128.
[9]
Kühn W. and Müller U. (2000) Riverbank filtration - an overview. Journal AWWA 92, 60 - 69.
[10] Malle K.G. (1994) Accidential spills - frequency, improtance, control and coutermeasures. Water
Sci. Technol. 29 (3), 149 - 163.
[11] Mathys W. (1994) Pesticide pollution of ground and public drinking waters caused by articial
groundwater recharge or bank filtration. Zentralbl. Hyg. Umweltmed. 196, 338 - 359.
[12] Miettinen I.T., Vartiainen T. and Martikainen P.J. (1997) Changes in water microbial quality during
bank filtration of lake water. Can. J. Microbiol. 43, 1126 - 1132.
[13] Sacher F., Brauch H.-J. and Kühn W. (2001) Fate studies of hydrophilic organic micro-pollutants
in riverbank filtration. In: Proceedings of the International River Bank Filtration Conference (Jülich
W. and Schubert J., Eds.), IAWR Rheinthemen 4, 139 - 148.
[14] Sontheimer H. (1980) Experience with river bank filtration along the river Rhine. Journal AWWA
72, 386.
[15] Tufenkji N., Ryan J. N. and Elimelech M. (2002) Journal AWWA 94, 423 A – 428 A.
Contact:
Prof. Dr. –Ing. Martin Jekel
Dept. of Water Quality Control
Technical University Berlin
Sekr. KF 4
Strasse des 17. Juni 135
D-10623 Berlin
Email: [email protected]
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Dr.-Ing. Bernd Heinzmann
Head of R & D Department
Berliner Wasserbetriebe
Cicerostraße 24
D-10709 Berlin
Email: [email protected]
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