The spatial distribution of confining layers within a system of two aquifers strongly affects the hydraulics and sensitivity to pollution. The test site is located close to a well field. Wells are switched with short intervals and hydraulic heads are recorded in several observation wells. Because the absolute levels of simulated hydraulic heads do not always coincide with the measurements, the model is calibrated with short term head variations. The characteristic shape of the hydraulic heads at each observation wells contains sensitive information about the structure of the aquifer. A numerical technique is developed which enables to simulate the spatial distribution of the confining layer. The method comprises the use of pilot points and regularisation technique. Cross validation is carried out in order to show the results are physically based. The method is shown to provide significant results even under non optimal conditions.

Cylindrospermopsis raciborskii, a cyanobacterium of tropical origin, can produce the toxin cylindrospermopsin (CYN). This originally tropical cyanobacterium (bluegreen algae) has now spread to the distant waters of the Berlin area. Cylindrospermopsin has been detected in two lakes in the area, but none of the C. raciborskii strains isolated here so far were found to produce the toxin. The main objectives of the CYLIN project were therefore to analyze the distribution and regulation of C. raciborskii and cylindrospermopsin and to determine which cyanobacteria are producing this toxin in order to establish a basis with which to predict the further course of development of this species and the related health hazards for humans. The CYLIN project was implemented as a three-part program. A screening program was first conducted in 2004 to test regional water bodies for the presence of cylindrospermopsin and potential CYN-producing cyanobacteria in order to obtain an overview of their distribution in the study region. A total of 142 regional water bodies were sampled once each in this qualitative analysis cylindrospermopsin and cyanobacteria. The screening program was followed by a monitoring program designed to generate quantitative data on the concentrations of dissolved CYN, particulate CYN, cyanobacteria and target environmental parameters at 20 selected lakes, which were sampled 3 times each. Last but not least, we investigated the seasonal dynamics of these parameters at two selected lakes in 2004 and 2005. Apart from this we isolated different cyanobacterial strains and conducted chemical and molecular biological analyses of CYN and CYNcoding genes, in order to identify CYN-producing cyanobacteria. The results show that C. raciborskii and CYN are much more widespread than was previously assumed. C. raciborskii was detected in 22 % of the investigated water bodies, and cylindrospermopsin in 52 %. Additionally, two other toxic cyanobacteria of tropical origin were found for the first time in the BerlinBrandenburg region, Anabaena bergii and Aphanizomenon aphanizomenoides. The mean and maximum CYN concentrations were 1 µg L-1 and 12 µg L-1, respectively. Since the particulate CYN fraction did not exceed 0.5 µg L-1, the dissolved CYN fraction was found to be responsible for the high CYN concentrations. The proposed guideline safety value for cylindrospermopsin in drinking water (1 µg L-1) was exceeded 18 times at 8 different lakes. Although Aphanizomenon flos-aquae (Nostocales) has been unequivocally identified as a producer of cylindrospermopsin, the observed cylindrospermopsin concentrations cannot be attributed to this cyanobacterial species alone. Aphanizomenon gracile was also identified as a potential CYN-producing cyanobacterium. Based on the findings of the CYLIN project, we recommend that cylindrospermopsin be included as a risk factor in drinking and bathing water quality assessments. To identify hazard conditions associated with this cyanotoxin, further investigations are needed to identify all cyanobacteria that produce cylindrospermopsin and to elucidate the mechanisms regulating the occurrence of CYN-producing cyanobacteria, CYN synthesis by these organisms, and CYN decomposition in aquatic ecosystems. Our analysis of C. raciborskii population dynamics showed that its germination is temperature-dependent and its population growth light-dependent. Population size was determined by the time of germination, that is, the earlier the time of germination, the bigger the population. Based on these findings, it appears highly likely that the climate-related early rise in water temperatures over the course of the years has promoted the spread of this species to temperate regions. Our hypothesis for the future course of cyanobacterial and cyanotoxin development in German waters is as follows: The combination of trophic decline and global warming works to the general benefit of cyanobacteria of the order Nostocales and leads to a shift in cyanobacterial species and toxin composition. This may ultimately lead to an increase in the incidence of neurotoxins as well as cylindrospermopsin.

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.

Major reservoirs are a key element for public water supply in many countries. In Europe over 800 major reservoirs serve primarily this purpose. Eutrophication affects significant numbers of lakes and reservoirs, and is the well-known issue currently impacting drinking water supply reservoirs. In most cases, phosphorus is the principal cause of eutrophication, and therefore has been studied intensively. The presence of micro pollutants (e.g. pesticides, pharmaceutically active compounds - PhaCs) is not systematically monitored but some substances are very mobile and tend to resist degradation. Such contaminants have been detected in numerous surface water bodies (lakes, reservoirs and rivers). As agriculture is intensifying and land use is changing in many areas, the impact of diffuse pollution on water quality is expected to be more pervasive in the future. The project Aquisafe proposes to investigate the topic in a multi-step approach which will include: i) an analysis of the nature, occurrence and risk of surface water contamination, ii) a modelling approach to quantify the contaminants origin, load and repartition to assess the effects of adapted controlled measures, and iii) the development, adaptation or optimisation of the design and operation of mitigation zones (riparian corridors and small scale wetlands) to reduce downstream loads of pollutants. Thus, Aquisafe is a first step to establish the state-of-the-knowledge on current existing solutions, identify emerging issues and assess the feasibility of using models for the evaluation of mitigation zones for contaminants removal. Within the Aquisafe project it will expected: i) a recommendation on potential key substances to be targeted, also for further investigations, ii) an identification of drinking water source vulnerability to emerging contaminants using a coupled modelling approaches, and iii) an analysis of existing mitigation methods and scientific background for the construction of riparian corridors and/or constructed wetlands in order to mitigate trace contaminants entering the surface water.

The KompetenzZentrum Wasser Berlin (KWB) is a private research and development center, created in 2000, with a status of public interest, and mainly supported by Veolia Water and Berliner Wasser Betriebe. This is where I did a six month-training period as part of my studies at the French AgroParisTech ENGREF engineering school. Within the department “Point and non-point source pollution control”, the KWB initiated a program called Aquisafe. The aim is to investigate the mitigation of trace contaminants from diffuse sources in rural and semi-rural areas to improve water quality of surface water bodies. The sustainable way of addressing pollution control is that the selected mitigation metods are natural or nature-based: namely constructed wetlands and riparian1 corridors. To develop knowledge and tools about these mitigation zones, an innovative approach was chosen when conducting the project: - The first part aims at a background study about surface water and pollutions from diffuse sources, leading to a progressive focus on key pollutants for the future of the project. The second part investigates modelling tools as diagnosis tools for the repartition and load of contaminants in a watershed. The third part contains field experiments and uses results from previous parts. The final purpose is to assess the mitigation efficiency of the systems and to optimize their design in the perspective of improving surface water quality. In charge of the first part, I did set the context of the project by reviewing background information on surface waters in Europe and associated pollutions, that move to water via soil surface run-off or subsurface run-off. After using criteria related to the Aquisafe context, the main pollutant families of interest for the rest of the screening process are pesticides used in agriculture, pollutants coming from the spreading of animal waste on land, pollutants coming from the spreading of sludge from wastewater treatment plants, pollutants from natural and extensive areas, and pollutants from transportation networks. During the study it appeared that in a rural or semi-rural area, the land use of the watershed plays a key role in the selection and assessment of priority pollutants coming from diffuse sources and entering surface waters. The importance of this factor should always be kept in mind as the project goes on. The work is still in progress concerning the review of pollutant families, and will lead to the final screening at the molecule level, providing a list of key contaminants for the other parts of the Aquisafe project. Finally the results of Aquisafe will tell if such sustainable mitigation zones can be used as a real innovative management tool of diffuse pollution in a watershed.

Urban water courses are considerably degraded in terms of their hydrology, riparian and channel morphology, substrate heterogeneity and habitat features as well as water and sediment quality. In addition, the combined sewer overflows and the ecotoxicological impacts of its components lead to a change of the physical-chemical and microbial mass balance affecting the biocenoses of higher trophic levels. Combined sewer overflows are therefore an additional stress to the ecological status of the urban course of the River Spree and of its channels, which is damaged already by both preload and background load of the aquatic environment. With regard to the assessment of the ecological water status, the European Water Framework Directives gives priority to the aquatic biocenoses in their capacity as ecological quality parameters. Against this background, an immission-oriented approach for the assessment of combined sewer overflows has to describe also their impacts on the biocenoses of the macrozoobenthos, the fish fauna, the macrophytes and the phytoplancton. These biocenoses are protected against the harmful impacts resulting from CSO only if the modification of their physical and chemical environment is avoided or reduced to an ecologically tolerable level respectively. In case that unfavourable impacts cannot be completely eliminated, the degree of impairment and the number of damaging CSO discharge events, which appear to be acceptable, should be defined. The present study is based on the bibliographic study „ Impact of urban use on the mass balance and the biocoenosis of lowland rivers under special consideration of combined sewer overflows” and deals with the assessment of CSO impacts on the ecological situation of the urban Spree and the channels (Cyprinid water bodies). In general, the immissionoriented assessment of CSO impact on the biocenoses (macrozoobenthos, fish fauna) requires the observation of the intensity, duration and frequency of occurrence of the individual events based on the assumption that, due to the background pollution, top priority is currently given to the acute CSO impacts. Requirements for the protection of aquatic biocenoses are developed with regard to the target parameters oxygen and ammonium/ammoniac and ecological tolerances of the biocenotic subjects of protection, which are strongest influenced by CSO. Initially, it is discussed to what extent the already existing results from laboratory investigations can be transferred to field situations. Next to the commonly accepted threshold values for oxygen concentrations during continuous persistent loads, particular requirements for the oxygen balance in case of peak loads are formulated.

The objective of the studies performed in the scope of the Integrated Sewage Management (ISM) project on combined sewer overflows in Berlin, Germany was to develop methods that would make it possible to assess wastewater management measures performed under the city’s water management permit as well as more sophisticated strategies (e.g., global real time control) through the application of water body-related criteria. For this purpose, a preliminary study was first performed to characterize the underlying water body-specific processes and hydraulic, physical, chemical and ecological parameters relevant to the status of Berlin’s surface waters (LESZINSKI et al., 2007a). The second step involved the development of a method for water quality-oriented assessment of wastewater management measures (LESZINSKI ET AL., 2007b). In addition to the already recognized thresholds for dissolved oxygen concentration during continuous, long-term water load conditions, particular focus was placed on formulating requirements for oxygen demand under peak load conditions. Ammonia toxicity due to sewage input, another important stress factor for aquatic ecosystems, was also analyzed and threshold values for both chronic and acute peak ammonia loads were defined. The results of the third phase of this research are described in this report. Two numerical simulation models (for urban drainage networks and surface waters) were combined and the feasibility of the developed method was evaluated based on the case of a combined sewer overflow event documented by the surface water monitoring. The simulations were performed using InfoWorksTM CS hydrological/hydrodynamic urban drainage network modeling software (ISM model) and the GERRIS/HYDRAX/Qsim unsteady ecosystem modeling system. The latter model was developed by the Federal Institute of Hydrology in Koblenz and is used by the Senate Department of Health, Environment and Consumer Protection (SenGesUmV). The present report describes the theoretical principles of the utilized models, the base of data available for analysis of the selected event, and the assumptions made in cases of missing input data for hydraulic modeling as well as for the water quality simulations. The one-dimensional hydraulic modeling results for the branched surface water system of the reach Berlin-Charlottenburg demonstrated that the hydraulic conditions can be simulated with satisfactory accuracy using the current data. In the case of water temperature, it was also possible to achieve a high degree of agreement between the measured and computed values in spite of the lack of highresolution temporal input data from the tributaries (Landwehr Canal, Panke River, BerlinSpandau Ship Canal). However, this was not the case for dissolved oxygen concentration, the main parameter used for evaluation of combined water treatment. The DOC simulations computed using input data based on a monthly sampling interval did not show satisfactory agreement with the online measurements in the water system. Dry-weather biological processes, which were associated with high-level, short-term oxygen enrichment or consumption, could not be depicted in the simulations. After completion of the water quality simulations, the effect of variation of individual input parameters was assessed. This analysis showed that no significant improvement of agreement with the measured values could be achieved by adjusting the assumptions for individual parameters (chlorophyll-a and BSB5). In the case of ammonia, the second most important parameter, the available sampling data from the tributaries in the investigated water system were collected only once a month, if at all. Therefore, it cannot be expected that the temporal distribution of this parameter was correctly reflected by the model. The number of validation measurements taken within the water system was also insufficient. Summarizing the results of the study of the linked urban drainage/surface water quality model, which was tested for the first time, it can be concluded that InfoWorks CS and GERRIS/HYRDRAX/Qsim provide problem-oriented simulation tools for reaching the objective of ISM study of assessing various scenarios for reduction of impacts from combined sewer overflows. By contrast, the available data are deficient and do not allow to adjust and calibrate the models to meet the specific needs of this task, particularly in light of the fact that short-term effects of combined sewer overflows are to be analyzed.