The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions.

This report attempts to give a survey from literature on the microorganisms involved, on the factors and mechanisms potentially relevant for the susceptibility of drinking water wells to health related microbial contamination. The habitat groundwater accommodates a rich diversity of microorganisms, which has only begun to be identified since the development of molecular detection methods in addition to the conservative cultivation techniques. Characteristics of the subsurface are darkness, low spaces, low nutrient and low oxygen content. Indigenous microorganisms have adapted to these oligotrophic conditions and are able to proliferate in this environment permanently. Other incoming microorganisms generally cannot reproduce under these conditions, but have developed strategies to survive. They can grow only, when the parameters turn favourable. Pathogenic microorganisms comprise bacteria, viruses, and protozoa, which can also survive a certain time in groundwater. Most microorganisms in the subsurface are attached to surfaces and survive best within biofilm populations. Pathogenic microorganisms originate from human or animal faeces. These organisms are not easily detected. The methods are very time and labour consuming. Therefore, other microorganisms regularly present in the faeces are used for detection. Their presence indicates the possibility of a contamination with pathogens. As indicator microorganisms mostly coliform bacteria, E. coli, enterococci and clostridia are used. Contamination with pathogens is reported to derive essentially from communal sources: defects in wastewater treatment plants, sewage tanks, pipes, and waste deposits; from agricultural sources: animal wastes, liquid manure, and grazing; and from point sources like faeces from animals, birds, and humans. Entrance into the subsurface occurs via rainwater and surface waters, as well as by direct contamination of wells. The transport of the microorganisms into the subsurface is influenced by the geologic conditions of a specific site: soil and rock type, presence of fissures, heterogeneity. In sand, microbial movement is less far than e.g. in Karst regions, thus the susceptibility to contamination of groundwater and wells is lower. Pore sizes are crucial for sedimentation and filter efficiency of the soil. Also important is the extent of the unsaturated zone, the flow velocity of the groundwater, the geochemistry and mineralogy of the site. Wells receive their water from the groundwater reservoir of the surrounding soil. The quality of the well water is therefore essentially dependent on the properties of the groundwater and all the factors influencing the groundwater may also be relevant for the well water. The wells represent, in addition, a separate complex system with specific conditions and influencing parameters. This specific habitat involves additional variable adsorption surfaces, more space, higher flow velocity of the water, a mixing of waters from different groundwater layers and thus a different chemical composition. Contamination may also arise from microbial introduction at the open wellhead. Two main processes have been identified which are essentially responsible for the elimination of pathogens during their pathway from top of the soil to the extraction well: inactivation of the microorganisms and their adsorption to the soil particles in the subsurface. Both processes are influenced by a variety of factors and conditions present at a given site. To mention are here properties of (i) The soil: consistence and texture of surfaces, electric charge, hydrophobicity, degree of moisture, coating with organic material. (ii) The groundwater: temperature, pH, presence of cations and ionic strength, presence of organic substances, dissolved oxygen content, activity of indigenous microorganisms. (iii) The microorganisms: forming of flagella, fimbria, hydrophobicity of the cell surface, forming of extracellular polymeric substances, forming of cysts and spores as survival strategies. In addition to the description of the microbial diversity in the subsurface, the sources of pollution and the factors controlling the microbial pathways into groundwater and wells, main methods for the detection of a variety of contaminating microorganisms are given at the end of the report.

The Aquisafe project aims at mitigation of diffuse pollution from agricultural sources to protect surface water resources. The first project phase (2007-2009) focused on the review of available information and preliminary tests regarding (i) most relevant contaminants, (ii) system-analytical tools to assess sources and pathways of diffuse agricultural pollution, (iii) the potential of mitigation zones, such as wetlands or riparian buffers, to reduce diffuse agricultural pollution of surface waters and (iv) experimental setups to simulate mitigation zones under controlled conditions. The present report deals with (iii) and has the purpose to provide a brief overview of the current state of knowledge related to the role of riparian zones as best management practices for water quality improvement at the watershed scale. Research indicates that landscape hydrogeological characteristics such as topography and surficial geology influence both riparian zone hydrology and biogeochemistry. Topography, depth to a confining layer and soil hydraulic conductivity all affect groundwater input to riparian zones and the water table fluctuation regime throughout the year. Research also indicates that although most biologically mediated reactions in soil are redox dependant, landscape hydrogeology, by affecting riparian hydrology, affects the redox conditions in the soil profile. In turn, microbial processes and changes in element concentrations are predictable as a function of the redox state of the soil.Variations in biogeochemical conditions directly affect the fate of multiple contaminants in riparian systems. In particular, variations in soil redox potential in riparian zones can affect the evolution of numerous contaminants and solutes within riparian zones like pesticides, phosphorus, NO3-, N2O, NH4+, SO42-, CH4, Fe2+/Fe3+ or Dissolved Organic Carbon (DOC). Of all the solutes/contaminants mentioned above, nitrate is one of the most important concerning water quality in many areas of the US and Western Europe. Consequently, many studies have investigated nitrate removal in riparian systems. Depending on site conditions, nitrate retention generally varies between 60 and 90 %; however, there are situations where nitrate removal is less or even where a riparian zone becomes a source of N to the stream. Although the riparian literature is clearly dominated by nitrate removal studies, many studies also focus on phosphorus, sediments, pesticides, chloride, bromide and bacteria. Although there are situations where riparian zones have been shown to be sources of P, Atrazine, bromide, E. coli or E. streptococci bacteria, riparian zones generally contribute to the reduction of most contaminants in subsurface flow and overland flow. Nevertheless, although conditions favorable to the reduction or oxidation of a given contaminant at the microbial level are often known, more research needs to be conducted to determine the variables controlling the fate of contaminants other than nitrate in soil at the riparian zone scale.Finally, although many studies have investigated the hydrological and biogeochemical functioning of riparian zones in the past few decades, much research remains to be conducted in order to quantify and predict the impact of riparian zones on water quality at the watershed scale in a variety of climatic and hydrogeological settings. In particular, better strategies and/or tools to generalize riparian function at the watershed scale need to be developed. Particular areas where research is needed to achieve this goal include: 1) the development of strategies to quantify and model the cumulative impact of individual riparian zones on water quality at the watershed scale; 2) a better quantification of the importance of spatial and temporal variability in hydrologic and biogeochemical riparian functioning relative to annual nutrient transport; 3) a better understanding of the role of vegetation in terms of its impact on riparian biogeochemical processes and the response of these processes to manipulations of vegetative cover; 4) a better understanding of the impact of human activities and infrastructure on riparian zone function in both urban and rural landscapes; 5) a better understanding of the fate of emerging contaminants in riparian systems.

Aim of this study is to evaluate the impacts of combined sewer overflows (CSO) on the Berlin Spree focussing on the intermittent effects of oxygen depletion on the aquatic biocenosis. The investigation bases on a long series of measurements carried out by Berliner Wasserbetriebe and the Berlin Senate for Health, Environment and Consumer Protection.

In ländlichen Gegenden stellen Kleinkläranlagen eine kostengünstige Lösung für die Abwasserentsorgung dar. Nach der in Europa gültigen Definition von Kleinkläranlagen handelt es sich hierbei um Anlagen zur Behandlung von häuslichem Abwasser bis zu 50 EW. In Deutschland sind ca. 2,2 Millionen Kleinkläranlagen in Betrieb bzw. werden installiert. In Frankreich werden etwa 10 bis 12 Millionen Einwohner von dezentralen Systemen versorgt mit steigender Tendenz. Die technischen Lösungen solcher Systeme reichen von Pflanzenkläranlagen über Schilfrohrfilter bis zu Belebungsanlagen. Alle auf dem europäischen Markt verfügbaren Systeme müssen der EU-Zertifizierung EN 12566-3 entsprechen, die einen indeststandard bezüglich Betriebssicherheit und Reinigungsleistung setzt. Weiterhin müssen, je nach nationalen oder regionalen Vorgaben, zusätzliche Richtlinien beachtet werden. Es sind nur wenige Informationen verfügbar über Effizienz, Betriebszuverlässigkeit und Wartungsfreundlichkeit im realen Betrieb der unterschiedlichen am Markt verfügbaren Kleinkläranlagentypen, was aber gerade für Kunden, aber auch für Anbieter von Abwasserdienstleistungen von besonderem Interesse ist. Um diese Lücke zu schließen, wurden in vorliegender Studie über eine Dauer von 14 Monaten nebeneinander 12 unterschiedliche Systeme unter realen Betriebsbedingungen verglichen und bewertet. Die Studie liefert damit detaillierte Informationen zu den Leistungsmerkmalen unterschiedlicher Anlagentypen hinsichtlich Reinigungsleistung, Ablaufwerte, Betriebsaufwand, Schlammbehandlung und Energieverbrauch. Die Untersuchungen erfolgten an einer Auswahl von auf dem Testfeld des Bildungs- und Demonstrationszentrum für dezentrale Abwasserbehandlung e.V. (BDZ) in Leipzig zu Demonstrations-und Schulungszwecken vorinstallierten Kleinkläranlagen sowie zwei zusätzlich dort eigens für das Vorhaben eingebauten Systemen.

While climate change is an emerging hazard to water supply, literature on the vulnerability of bank filtration (BF), a proven technique of drinking water production in Central Europe and North America, is yet scarce. The Intergovernmental Panel of Climate Change (2007) has projected a global temperature increase between 1.1 and 6.4 °C by 2100. This will affect vital factors for water supply such as precipitation regime, groundwater recharge, run-off, river discharge and raw water quality. Projections on climate change and the implications are difficult because of the uncertainties associated with climate scenarios and modelling. However, in Europe and North America where BF is in operation, the projected increase in seasonal floods and droughts has already been experienced. In addition, site-specific considerations (e.g. land use, demographic trends) are to be taken into account to evaluate the potential impacts on water supply. To fill the current gap in literature, this report provides a first overview on how changing environmental conditions may affect BF operation.

During the ISM study in the year 2007 first water quality simulations of the Berlin river Spree (stretch Charlottenburg) under consideration of combined sewer overflows (CSO) from the drainage system had been carried out. The period of September 2005 was simulated. A good correlation of simulation results with water quality measurements could only be observed for those days where the model boundary conditions were clearly defined (spot samples at the inflowing streams). However, these spot samples are carried out only once a month. Given the simulation period of one month and the temporal resolution of 15 minutes this data availability for the inflowing streams is not sufficient. Even more, some parameters had to be assessed entirely since no measurements were available. The data situation was especially critical for the inflow of the Landwehrkanal into the river Spree. No continuous measurement data was available for the following parameters: water temperature, oxygen content, pH and conductivity. For these parameters hydrographs had been assumed according to those at gauge Mühlendammschleuse with an offset calculated by the difference between the spot sampling at Landwehrkanal and the continuous values at Mühlendammschleuse. Furthermore, during the simulations within the ISM study a second storm event with overflows could not be considered since the simulation of the drainage system (software INFOWORKS CS) carried out by Berliner Wasserbetriebe was not yet available. The objective of the water quality simulations carried out within SAM-CSO was to take into account the full boundary conditions for the Landwehrkanal (continuous data now available). By comparison with the former simulation results the relevance of the inflow Landwehrkanal on the processes in the river Spree is shown. A second simulation was carried out with meteorological data of high temporal resolution. Former simulations were conducted with daily averages for e.g. air temperature, wind speed, etc. The influence of the temporal resolution of the input data on the diurnal hydrographs of different water quality parameters was analysed (focus on water temperature and dissolved oxygen). Finally, for the last simulation the data for the additional CSO event on 16-17 September 2005 was used (simulated by Berliner Wasserbetriebe with INFOWORKS CS). The results show that considering meteorological data of high temporal resolution and continuous data for the boundary condition Landwehrkanal have a significant influence on the quality of the water quality simulation results for river Spree, especially for the parameters oxygen content, pH and conductivity. Now, for September 2005 simulation results are available that are based on the best set of data that is currently available for the studied river stretch.

Work package WP 5.2 “Combination of Managed Aquifer Recharge (MAR) and adjusted conventional treatment processes for an Integrated Water Resources Management“ within the European Project TECHNEAU (“Technology enabled universal access to safe water”) investigates bank filtration (BF) + post-treatment as a MAR technique to provide sustainable and safe drinking water supply to developing and newly industrialised countries. One of the tasks of WP 5.2 is to develop a Decision Support System (DSS) as a first qualitative tool to assess the feasibility of bank filtration for drinking water supply in developing countries. The Bank Filtration Simulator (BFS), which is the subject of this report, is a sub-model used within the DSS to compute steady-state solutions for a two dimensional groundwater flow field in the horizontal plane for BF settings. Input parameters are required for aquifer, bank and well characteristics to calculate the BF share analytically. In addition the minimum travel time between bank and well is computed numerically. The sensitivity analysis yielded that the analytical calculated BF share is the most reliable output parameter, since its value is grid-independent. The most sensitive input parameters for the BF share calculation are the hydraulic conductivity of the aquifer and the clogging parameter, which both are the most uncertain ones to estimate. The accuracy of the numerically computed minimum traveltime of the BFS was cross-checked against a MODFLOW model, which produced only a very small discrepancy below 5%. Due to the lacking time-dependency of the BFS model its application is only appropriate on a management horizon for which the system’s boundary conditions (e.g. baseflow, clogging parameter and pumping rates) do not change significantly over time. In a nutshell it is therefore highly recommended to use the BFS only as a qualitative assessment tool in a first planning step to evaluate the feasibility of BF systems. Nevertheless the qualitative outputs give a valuable physically based insight of the system’s behaviour for distinct operational scenarios (e.g. minimal/maximum pumping rates) in order to add transparency and reproducibility to the decision making process.