The occurrence of the cyanobacterial toxins anatoxin-a (ATX) and cylindrospermopsin (CYN) in surface waters has been reported throughout the world. Beside degradation, sorption is an important pathway for toxin elimination if these resources are used for drinking water production via sediment passage. However, to date studies that systematically investigated sorption of these toxins onto sediments are lacking. Therefore, the aim of our work was (i) to determine the adsorption coefficients of ATX and CYN according to the Freundlich and Langmuir model for sediments of various textures and (ii) to derive sorptionrelevant sediment characteristics. We determined sorption parameters in air-dried samples of eight differently textured sediments using batch experiments. Results for both toxins showed best fits with the Langmuir model. Organic C proved to be the main sediment parameter determining CYN sorption. There was no or little CYN sorption on sandy and silty sediments (0e39 mg kg-1), respectively, presumably due to charge repulsion from the negatively charged surfaces. Sorption of ATX (max. sorbent loading ranging from 47 to 656 mg kg-1) was much stronger than that of CYN (max. sorbent loading ranging from 0 to 361 mg kg-1) and predominantly controlled by clay and to a minor degree also by organic C and silt. While ATX sorption to most sediments occurred mainly through cation exchange this mechanism played only a minor role in CYN sorption to organic C. Hence, high mobility for CYN and moderate mobility for ATX during sediment passage has to be expected.

The aim of the present study was to estimate the performance of slow sand filtration (SSF) facilities, including the time needed for reaching stabilization (maturation), operated with surface water bearing high fecal contamination, representing realistic conditions of rivers in many emerging countries. Surface water spiked with wastewater was infiltrated at different pore water velocities (PWV) and samples were collected at different migration distances. The samples were analyzed for phages and to a lesser extent for fecal bacteria and enteric adenoviruses. At the PWV of 50 cm/d, at which somatic phages showed highest removal, their mean log10 removal after 90 cm migration was 3.2. No substantial differences of removal rates were observed at PWVs between 100 and 900 cm/d (2.3 log10 mean removal). The log10 mean removal of somatic phages was less than the observed for fecal bacteria and tended more towards that of enteric adenoviruses This makes somatic phages a potentially better process indicator than Escherichia coli for the removal of viruses in SSF. We conclude that SSF, and by inference in larger scale river bank filtration (RBF), is an excellent option as a component in multi-barrier systems for drinking water treatment also in areas where the sources of raw water are considerably fecally polluted, as often found in many emerging countries.

The effect of combined sewer overflow (CSO) control measures should be validated during operation based on monitoring of CSO activity and subsequent comparison with (legal) requirements. However, most CSO monitoring programs have been started only recently and therefore no long-term data is available for reliable efficiency control. A method is proposed that focuses on rainfall data for evaluating the effectiveness of CSO control measures. It is applicable if a sufficient time-series of rainfall data and a limited set of data on CSO discharges are available. The method is demonstrated for four catchments of the Berlin combined sewer system. The analysis of the 2000–2007 data shows the effect of CSO control measures, such as activation of in-pipe storage capacities within the Berlin system. The catchment, where measures are fully implemented shows less than 40% of the CSO activity of those catchments, where measures have not yet or not yet completely been realised.

Artificial Recharge (AR) is a method to replenish groundwater in case of insufficient water availability or poor quality. For drinking water production, AR is often used as water purification step to avoid direct surface water abstraction. Besides physical filtration, purification is achieved through chemical processes like precipitation, sorption and (bio-) degradation. These are usually closely linked to redox conditions. It is the activity of micro-organisms and related chemical reactions that change the redox conditions, which in turn control the presence of substances and therefore the water quality. Typical pollutants in surface water that need to be addressed are organic compounds (e.g. pharmaceutical residues or pesticides), pathogens and heavy metals. The purpose of this report is to introduce the theoretical background on redox zoning in infiltration ponds and to review publications in the search for applicable methods capable of controlling redox conditions. This shall serve as basis for further laboratory and technical scale experiments in the course of the OXIRED project. The “optimal redox zonation” for maximum removal of redox-dependent substances is a concept with the aim of defining optimum residence times based on the degradation kinetics of contaminants in the source water: If substances or substance groups that show enhanced removal under anoxic to anaerobic conditions are not present in the source water at drinking water relevant concentrations, anoxic to anaerobic conditions should be avoided in order not to mobilize iron and other inorganic trace elements. Maximum benefit for aerobic subsurface passage is reached after 30 d, for anoxic / anaerobic subsurface passage after 100 d. However, already 15 d of aerobic and 2 d of anoxic / anaerobic passage lead to substantial removal or redox-sensitive substances or substance groups. The main drivers for redox zonation in AR systems are the availability of oxidizing agents (oxygen, nitrate), of reducing agents (organic matter, reduced mineral phases), of nutrients, the biological activity (in infiltration pond and subsurface), and the residence time. These drivers are in turn controlled by many natural, site-specific (exogenous) and design & operation-related (decision) variables. Exogenous variables are e.g. aquifer geochemistry, temperature or natural groundwater recharge whereas the decision variables comprise factors such as pond geometry, distance between pond and well, well depth, pumping rate etc. Theoretically, a wide range of possibilities could be applied to adjust the infiltration pond, the hyporheic zone and the subsurface passage, but only few seem technically feasible. These are e.g. the control of sunlight and temperature in the infiltration pond and upper sediment, the control of water movement in the pond to avoid excessive algal growth while enriching the water with oxygen. For the same reason nutrients could be added or avoided, influencing biomass production. Specific filter material could be used with defined content and characteristic of organic carbon to serve as electron acceptors. Infiltration rates could be controlled by adjusting the hydraulic head in order to enhance the formation of an unsaturated zone. Further downstream the application of redox controlling substances via injection wells could be possible, as well as controlling the residence times by adjusting pumping rates or creating hydraulic barrier wells at different distances from infiltration pond. For newly constructed AR systems the well field design (pond geometry, distance between pond and well, well depth) could be optimized with respect to redox zonation, as long as the other requirements (mainly sufficient production rates) are met. No examples for redox control in infiltration ponds were identified. Therefore, two examples of redox control measures are described: the first serves an artificial reoxidation of a polluted aquifer “BIOXWAND®” and the second provides injection of treated water to influence the redox conditions in the aquifer “Vyridox” and “Nitridox”.

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 within the project is the development of a Decision Support System (DSS) to assess the feasibility of BF systems under varying boundary conditions such as: (i) quality of surface and ambient groundwater, (ii) local hydrological and hydrogeological properties (e.g. clogging layer) and (iii) well field design (distance to bank) and operation (pumping rates). Since the successful, cost-effective implementation of BF systems requires the optimization of different objectives such as (i) optimizing the BF share in order to maintain a predefined raw water quality or (ii) maintaining a predefined minimum travel time between bank and production well, both aspects are addressed within the DSS. As an example for a practical application the DSS is tested with data from the Palla well field in Delhi/India. As a result optimal shares of bank filtrate were calculated for the monsoon and non-monsoon season. By simulating different pumping and clogging scenarios with the BF Simulator optimal pumping rates were derived. The DSS proved to be a good qualitative tool to identify and learn about the trade-offs a decision maker has to make due to the (i) inherently competing nature of different objectives (e.g. high BF share and minimum travel time > 50 d) and the (ii) inherent uncertainty due to the large natural variability of boundary conditions (e.g. clogging layer). Since both characteristics can be addressed within the DSS it helps to add transparency and reproducibility to the decision making process. An additional advantage is that its application requires only low effort concerning time, money, and manpower. Thus the application of the DSS is recommended to accompany decision making processes especially in developing and newly industrialised countries where data availability and low financial budgets are usually the major burden for the application of more complex, data-demanding decision support tools. However, it needs to be considered that in practice additional parameters like water availability, energy efficiency and cost-benefit need to be taken into account.

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. One of the tasks within the project is the testing of a data-driven approach for the identification (pattern recognition) and quantification of the key processes that drive the groundwater (GW) dynamics in observation wells (OW) near well fields of a BF waterworks. For this BUSSE (2010) used a multivariate statistical method (principal component analysis - PCA) with daily GW level time series of 41 OWs and was able to identify four processes that explained 95% of the total variance in the data set. On the one hand GW recharge (58.9%) and its temporal delay (3.3%) explain 62% of the GW level fluctuations within the study period. On the other hand any discernible impact of waterworks abstractions is limited to one of the three well fields with the highest production rate (29.8% of explained variance). In addition the infiltration of a marshy ditch into the GW accounts for another 2.9% of the GW level fluctuations. Regarding the ability to identify driving forces for GW level fluctuations the main advantage for using PCA compared to process-driven GW flow modelling is that the driving forces for GW level fluctuations can be identified and quantified without requiring exact knowledge about the structural properties of the subsurface (e.g. aquifer transmissivities) and its input parameters (e.g. GW recharge, production rates). Note that the latter do not enter the PCA directly but are used for spatiotemporal interpretation of the results, which also requires some expertise. In addition, it is recommended to perform a sensitivity analysis of the PCA results in a next step, so that it can be tested whether the processes identified above are robust in case of changing input parameters such as: - Reduced spatiotemporal resolution - Study period with different boundary conditions (e.g. pumping regime). The contents of this report were presented to the involved experts from the Berliner Wasserbetriebe (BWB). In agreement with their recommendations it was decided to focus further research within follow-up projects on the (i) sensitivity analysis of the PCA results and (ii) to apply nonlinear approaches for identification and quantification of processes that drive GW quality dynamics within the study area.

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 within this work package is to assess the costefficiency of BF systems. For this a comparative cost analysis (CCA) between groundwater waterworks using BF as natural pre-treatment step and surface water treatment plants (SWTPs) is performed. The CCA yielded that, under the assumption of equally low surface water quality, BF systems are more cost-efficient than SWTPs. This result is in line with the general water source priority of water suppliers, which prefer resources with the best water quality and security under the constraint of guaranteeing sufficient water availability. Furthermore the sensitivity analysis confirmed that the natural boundary condition 'pumping rate per production well' has a major impact on the specific total costs of BF systems. Lower pumping rates lead to increasing capital costs for the additional production wells, which are not fully compensated through pumping cost savings and thus lead to increasing total costs. In addition the result of the monitoring scenario clearly confirmed that for this aspect groundwater waterworks have a structural disadvantage compared to surface waterworks. Subsequently, if monitoring costs are taken into account, a higher critical pumping rate per production well is required to exceed the break-even-point. In a nutshell the CCA shall support water supply managers in the complex process of making rational investment decisions. However, since within this analysis only water abstraction and treatment process costs are considered, the CCA does not cover the total cost structure of a waterworks (e.g. costs of building sites). Thus the application of the CCA is only valid if both (i) neglected costs and (ii) benefits are in the same order of magnitude for all alternatives (exception: most cost-efficient alternative provides excess benefits). In case that the above stated prerequisites are not fulfilled, the CCA is only a first step in the economic assessment and more powerful evaluation methods (e.g. cost-benefit analysis) are needed.

Brunnen werden seit Jahrtausenden zur Wassergewinnung genutzt. Doch erst seit wenigen Jahren spielt neben der Ergiebigkeit auch die Nachhaltigkeit von Brunnen eine Rolle, da Neubaugenehmigungen immer schwieriger und langwieriger zu erhalten sind. Durch optimale Auslegung des Brunnens und die Wahl des richtigen Standorts wird versucht, eine möglichst lange Betriebszeit zu erreichen. Trotz bester Voraussetzungen nimmt die Förderleistung von Brunnen im Laufe ihres Betriebes ab, das als Brunnenalterung bezeichnet wird. Die Alterungsrate ist abhängig von den geologischen und hydrochemischen Bedingungen, dem Brunnenausbau und dem Betrieb. Mithilfe vorbeugender oder reaktiver Instandhaltungsmaßnahmen wird versucht, die Leistung eines Brunnens möglichst lange zu erhalten oder wiederherzustellen. Die Wirtschaftlichkeit von Instandhaltungsmaßnahmen lässt zum „Lebensende“ eines Brunnens jedoch nach. Dann sollte der Ersatz des Brunnens geplant werden. Die vorliegende Arbeit ist Teil des durch das vom Kompetenzzentrum Wasser Berlin (KWB) durchgeführten Forschungsprojektes WELLMA, welches sich mit dem Betrieb und der Pflege von Trinkwasserbrunnen zur Optimierung der Leistung und der Wasserqualität beschäftigt. Hierfür sollte eine Methode getestet werden, die die Wirtschaftlichkeit von Regenerierungen eines Trinkwasserbrunnens mittels eines Vergleiches der Steigung der alterungsbedingten Betriebskosten und der Umlage des Gebrauchswertes bewertet. Ist die Steigung der Gebrauchswertumlage größer als die der alterungsbedingten Betriebskosten, lohnt sich eine weitere Regenerierung. Im gegenteiligen Fall wäre es wirtschaftlicher, den betroffenen Brunnen neu zu bauen. Außerdem sollte das wirtschaftliche Minimum der alterungsbedingten Betriebskosten prognostiziert werden, um daraus die Dauer der anstehenden Betriebsperiode ableiten zu können. Die Berechnung des methodischen Ansatzes erfolgte am Beispiel vier ausgewählter Brunnen der Berliner Wasserbetriebe. Zwei der vier Referenzbrunnen wurden aufgrund ihrer regelmäßigen präventiven Instandhaltung mit Wasserstoffperoxid (H2O2) ausgewählt, um zusätzlich deren Auswirkung auf die Wirtschaftlichkeit von Regeneriermaßnahmen beurteilen zu können. Die Berechnung der Referenzbrunnen bestätigte die Praxistauglichkeit des gewählten Verfahrens. Ausschlaggebende Parameter für die Kalkulation sind u.a. die spezifische Ergiebigkeit, die Anzahl der Betriebsstunden sowie die jährliche Abnahme der Fördermenge. Zudem bestätigte sich, dass durch den Einsatz von H2O2 eine Steigerung der spezifischen Ergiebigkeit erzielt wurde, in dessen Folge die Wahrscheinlichkeit auf eine weitere wirtschaftliche Regenerierung erhöht wird.

Berlin’s drinking water is produced from groundwater replenished by up to 60 % of surface water from the city’s abundant rivers or lakes using bank filtration or artificial groundwater recharge. Currently 700 production wells, located along the banks produce more than 200 Mio m³/a of drinking water, which is treated only for iron and manganese removal before distribution. This is due to the fact that different natural treatment processes (e.g. straining of particles, adsorption or biodegradation) occur during subsurface passage so that post-treatment effort is reduced. Compared to other bank filtration sites world wide, the situation in Berlin is characterized by low hydraulic conductivities but nevertheless high capacities. Interdisciplinary research projects have shown that travel times and redox conditions during subsurface passage are highly transient due to seasonal effects and discontinuous pump operation. Trace organics like pharmaceuticals and x-ray contrast media that occur in Berlin’s surface waters due to relevant shares of treated waste water are attenuated during subsurface passage to varying degree. Substances that were found to be poorly attenuated under oxic conditions or even persistent include carbamazipine, primidone, sulfamethoxazole, 1,5 NDSA, MTBE and EDTA. Under anoxic to anaerobic conditions others like phenazone and diclofenac show little removal. However, none of these substances occur at relevant concentrations in the finished drinking water due to low initial concentrations or additional removal during post-treatment. Research is currently focussing on hybrid systems combining subsurface passage with advanced drinking water treatment in order to be prepared in case higher source concentrations occur.