Cyanobacteria proliferation and the potential health risk related with the release of the associated toxins have lead the local association EDEN to initiate a comprehensive study on cyanobacteria in the river Erdre. Within the consortium in charge of the project, the Berlin Centre of Competence for Water (KWB) realised lab-scale research in cooperation with the German Federal Environmental Agency (UBA), on the species Planktothrix agardhii which predominates in the river Erdre, and the associated toxin microcystin. The objective was to determine the influence of key factors such as nutrients (nitrogen, phosphorus), light, flow velocity and sediments on cyanobacteria growth and competition as well as microcystin release from the Planktothrix population in the river Erdre. Results from the lab-scale cultures proved that nutrient-limited conditions lead to a decrease of cyanobacteria biomass and may favour some genotypes with reduced needs among the Planktothrix population. Given the current state of scientific knowledge, no differences in competition between toxic and non-toxic Planktothrix strains can be established. Nutrient limitation favours microcystin release from cells, however the global decrease of cyanobacteria biomass induces a decrease of the total quantity of released toxin. These results can be applied in a water body where nutrients concentrations are very low (below 50 µg/L for total phosphorus). In the river Erdre, as long as external nutrients inputs remain considerable, light is the limiting factor. Internal nutrient recycling from the sediments is globally negligible in comparison with external inputs. Culture experiments in a flow simulation flume proved that flow velocity had substantial impact neither on Planktothrix growth nor on microcystin release. Only a short transition phase with negative effects was observed. Overwintering of Planktothrix in Erdre-sediments could be proved by the detection of a substantial population using fluorescence analysis. This inoculum should be large enough for initiation of Planktothrix development in the next vegetation period. However, the high adsorption capacities of the analysed sediments from the river Erdre allow to put aside a potential risk of microcystin release from sludge. While providing innovative results on the species Planktothrix agardhii, this project contributes to the comprehensive study initiated by the EDEN association in order to preserve the values associated with environment, health and tourism in the river Erdre.

The effect of oscillating pumping regimes at the bank filtration site in Berlin Tegel is examined via a scenario based modelling study. Several scenarios for the pumping regimes are calculated, some adopted from the operation of the plant by the Berlin Water Works (BWB), some hypothetical with a regular oscillating regime. Two of these are presented here. A horizontal 2D model of the lower aquifer is set-up, in which the third type boundary condition is used to mimic the influence of an irregularly shaped till layer, overlying the main aquifer. Model results in form of flowpaths are presented for several pumping scenarios. They reveal that there is a substantial influence of the pumping regime on the flowpaths in the vicinity of the well gallery, while in the far field, including the bank of the surface water body (here: Lake Tegel) the oscillating effect is rather small. It depends very much on the infiltration position on the bank, whether traveltime through the aquifer changes as effect of oscillating pumping regime.

The Berlin Centre of Competence for Water (Kompetenzzentrum Wasser Berlin) together with its partners Berliner Wasserbetriebe and Veolia Water has started a pilot project about new sanitation concepts. In order to define the experiments for testing new, sustainable sanitation concepts a pre-study has been performed. This study included a cost comparison between two new sanitation concepts with gravity and vacuum separation toilets and the conventional system. It could be demonstrated that the new sanitation concepts may have cost advantages depending on the situation. This was a further motivation starting a pilot project near Berlin testing the above mentioned toilet systems under realistic conditions. The operation of the gravity separation toilets concept started in October 2003.

Bank fillration provides an important drinking water source to the city of Berlin. 56% of the drinking water is derived from bank filtration (the remainder is 14% replenished groundwater and 30% natural groundwater) [1]. At most bank filtration sites, the surface water contains portions of sewage treatment plant effluent (Lake Tegel 10-30%, [2]). Due to water recycling, the introduction of effluent organic matter (EfON) and persistent trace pollutants in the drinking water may be a concern. The project "Organic Substances in Bank filtration and Groundwater Recharge Process Studies" at the Department for Water Quality Control (DWQC) at the Technical University of Berlin is part of the "Natural and Artificial Systems for Recharge and lnfiltration (NASRI)' - project of the Berlin Centre of Competence for Water [3]. The research objectives of this part of the project are to study the removal of bulk organics (dissolved organic carbon (DOC) and EfOM) and trace organics at three field sites with different characteristics. Since the processes during bank filtration are very complex, it is difficult to predict bulk organic composition in the bank filtrale or to estimate important factors of influence for the degradation of trace compounds. For instance, it was shown in previous studies, that iodinated x-ray contrast medias are deiodinated under teductive conditions. Therefore, a bank filtration under anoxic or even anaerobic conditions would provide the removal of these trace pollutants. In addition to lhe redox state, factors such as retention time, initial degradable carbon . concentration, soil properties and hydrogeologlcal conditions may affect the final concentration. In order to be able to prevent the intrusion of persistent pollutants into the drinking water, lhe factors of influence are studied for a few model compounds that represent groups of trace pollutants. This will provide a tool that can be merged with hydrogeological models and soil properties to predict the removal efficiency of a given field site. To fulfill these objectives this research is presently investating: (i) the differences in bulk organic composition and trace organic concentration related to bank filtration conditions at three different field sites in Berlin, (ii) the simulation of a bank filtration site with a 30m soil column (elimination of hydrogeological variables).

Bank filtration and artificial recharge provides an important drinking water source to the city of Berlin. Due to water recycling, the introduction of persistent trace pollutants (e.g. pharmaceuticals) in the drinking water may be a concern. The project “Organic Substances in Bank filtration and Groundwater Recharge - Process Studies” at the Technical University of Berlin is part of the “Natural and Artificial Systems for Recharge and Infiltration (NASRI)”-project of the Berlin Centre of Competence for Water. The research objectives of this part of the project are to study the removal of bulk and trace organics at different field sites with different characteristics in Berlin. In Berlin’s public drinking water supply nearly 70% of the 220 Mio m3 per year originate from bank filtration and groundwater recharge (~56% from bank filtration and ~14% from groundwater recharge (BWB 2003)). Since the 19th century Berlin has relied on bank filtration with retention times of several months to produce “new” ground water. A semi-closed urban water cycle has been created with the growth of the city. At some bank filtration sites the surface water is strongly influenced by highly treated domestic waste water effluent (e.g. 15-30% in Lake Tegel) (Ziegler et al. 2002). Despite this indirect potable reuse, the bank filtration system continues to provide high quality water which is distributed without chlorination. This unique situation in Berlin was an interesting field site for a research project of the Berlin Center of Competence for Water. Recently, the break through of organic trace pollutants in bank filtration systems has been studied in various research projects. Especially, since improved analytical methods can detect in ranges below 1µg/l. Since the processes during bank filtration are very complex, it is difficult to predict the fate of trace organics during bank filtration or to estimate important factors of influence for their degradation. In addition to redox state, factors such as retention time, initial degradable carbon concentration, soil properties and hydrogeological conditions may affect the final concentration. Many studies revealed positive findings of pharmaceuticals, pesticides or industrial chemicals (Hiemstra et al. 2003, Heberer et al. 2001, Verstraeten et al. 2002) in bank filtrate. Compounds like carbamazepine and clofibric acid were reported to be partly recalcitrant during underground transport (Stan and Linkerhäger 1994, Ternes et al. 2002). Furthermore, Ternes and Hirsch (2000) reported the occurrence of x-ray contrast media in surface waters and in surface water influenced groundwaters, where they constitute a major fraction of the adsorbable organic iodine (AOI). The contrast media were found to be very polar, persistent and difficult to remove in wastewater treatment (Jekel and Wischnack 2000). Hartig (2000) reported the break through of antibiotic sulfonamides from surface water to monitoring wells more than 50 m off the lake front (residence time~3 months). But in most of the reported cases the concentration in the bank filtrate is much lower than in the surface water. Since this concentration decline is not only due to dilution, long term bank filtration appears to have the capability to reduce trace organic pollutant concentrations. It would be of great practical value to classify the important trace organic pollutants by degradability during bank filtration and to evaluate the conditions that are favorable for the removal of certain compounds. This study begins to clarify these issues for a few trace organic pollutants. The factors of influence for degradation are studied for model compounds that represent groups of trace pollutants. Additionally, the infiltration process is characterized by several bulk-organic parameters. The goal of the study is to provide a tool that can be merged with hydrogeological models and soil properties to predict the removal efficiency of a given field site.

In Berlin, 70 % of the drinkinq water is derived from bank filtrate or artificially recharged water. Because the surface water system contains elevated proportions of secondary treated municipal sewage, a number of sewage indicators from various sources can be detected in the bank filtrate. An artificial recharge site and a bank filtration site in Berlin Tegel are introduced and compared in terms of their hydrogeological and hydrochemical properties. Because of a permanent clogging layer and the geological properties, travel times are slower at the BF site and the hydrochemical conditions are more reducing. First estimates for the reaction rate constants of oxygen and nitrate are obtained with exponential data fitting. Some of the effects of the different redox conditions on minor substances such as drug residues are highlighted.

Induced by well abstraction, surface water infiltrates into Berlin aquifers and is used for drinking water production. A major advantage of bank filtration is the capability of the subsurface to remove contaminants and save natural groundwater resources. Since a large proportion of the surface water in Berlin originates from treated effluents released by wastewater treatment plants, certain wastewater residues can be traced into the groundwater. A powerful tool to characterise bank filtration systems is the use of wastewater indicators and additional environmental tracers to estimate flow velocities and proportions of bank filtrate in the abstraction wells prior to reactive transport evaluations. Examples for tracer applications at the Berlin system are introduced in this paper. In addition, an overview on results of various studies conducted on contaminant transport and removal during underground passage of the bank filtrate in Berlin is given.

With the application of advanced treated wastewater to the ancient wastewater irrigation field Karolinenhöhe, the Berlin Water Company (Berliner Wasserbetriebe) started in 1990 an ecological passable and water economical reasonable cultivation of an old wastewater irrigation field. After a period of 10 years of operation the functional capability and the efficiency is assed. In the first aquifer a hydrodynamic impact by the trickled water could be proved in the measuring facilities and certified by modelling. Altogether the application of the advanced treated wastewater stabilized the water balance and therefore the basis flow of the river Havel. Especially admissions during the low water periods (summer and autumn) counteract the low water level in the surface water by a raised basis discharge. Since 1990 the ecological status of the first aquifer of the wastewater irrigation field is clearly improved. The concentration of the relevant parameters of eutrophication NO3, NH4 und PO4 regressed significantly. In the second aquifer the parameter boron and phosphate improved from 1990 to April 2002. For the other parameters a diffuse basis load remained. The admission of the advanced treated water has a positive effect to the quality of the groundwater compared to the initial situation. The concentration of most of the parameters regressed. Just the concentration of potassium (in the first and second aquifer) and of AOX (in the first aquifer) stayed almost constant because of the input. There are no risks by continuing applications. There is a degradation of the nitrogen compounds due of the soil passage of the water and a dilution by the natural groundwater recharge. Therefore the receiving water bodies are less polluted compared to a direct discharge (exception potassium). A clear improvement is reached for the river Havel. The retention time of the water in the underground passage is very long because of the great depth of the groundwater level. Therefore a degradation of germs is assured. More detailed studies and analyses must follow this primal estimation.

Since the 1970s we know about the idea of real-time control of urban drainage systems. Anyway, global real-time control strategies still show a lack of implementation for large drainage systems of high complexity. In Berlin, Germany, a city of 3.5 million inhabitants covering an area of around 900 km², the demand for enhanced protection of the environment and the growing economic pressure have led to an increasing application of control assets and concepts within the sewage system. In the framework of the project “Integrated Sewage Management” the possibilities of a global and integrated control strategy for the Berlin system are examined. The paper is focused on the historical concept and design of the sewerage and the further improvement towards an environment-oriented system that builds the basis for today’s considerations. The operational method and functionality of local regulators that have already been implemented are described. Further more the model-based methodology for the analysis of the system and the development of global control concepts as well as results of system analysis are stated. On the basis of model simulations it is shown that a global coordination of pump stations can lead to a reduction of sewer overflows and consequently to an enhanced water protection.