In the course of identifying areas of relevance for further research and development the members of the European Water Supply and Sanitation Technology (WssTP) identified Managed Aquifer Recharge (MAR) as an important cross-cutting topic and area relevant for further research. For this reason a Task Force on MAR was initiated with 36 representatives from European research institutes and industry partners with participation of international experts. These task force members developed the basis for a report documenting the state of the art and research needs in the field of MAR that has now been published by the WssTP.

The present study aimed at developing a universal method for the localization of critical source areas (CSAs) of diffuse nitrate (NO3-) pollution in rural catchments with low data availability. Based on existing methods, land use, soil, slope, riparian buffer strips and distance to surface waters were identified as the most relevant indicator parameters for diffuse agricultural NO3- parameters were averaged in a GIS-overlay to localize areas with low, medium and high risk of NO3- pollution. The five parameters were averaged in a GIS-overlay to localize areas with low, medium and high risk of NO3- pollution. A first application of the GIS approach to the Ic catchment in France, showed that identified CSAs were in good agreement with results from river monitoring and numerical modelling. Additionally, the GIS approach showed low sensitivity to single parameters, which makes it robust to varying data availability. As a result, the tested GIS-approach provides a promising, easy-to-use CSA identification concept, applicable for a wide range of rural catchments.

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.

Bisherige Analysen des Energieverbrauchs in der Abwasserreinigung beschränken sich oft auf die naheliegende Erfassung des Stromverbrauchs. Im Sinne einer ganzheitlichen Betrachtung sollten aber auch andere Formen der Energie erfasst werden, wie zum Beispiel für die Herstellung von benötigten Chemikalien wie Flockungs- und Flockungshilfsmittel, beim Transport des zu entsorgenden Schlamms oder für zusätzliche Brennstoffe bei der Klärschlammtrocknung. Dafür ist die Erweiterung der Grenzen des zu betrachtenden Systems auf vor- und nachgelagerte Prozesse notwendig, um alle relevanten Beiträge zum Energieverbrauch zu berücksichtigen. Zudem können so auch die verschiedenen Sekundärprodukte der Abwasserreinigung erfasst werden: die Stromproduktion aus Faulgas, die Rückführung von Nährstoffen und Wasser in die Landwirtschaft oder die Substitution von fossilen Brennstoffen in der thermischen Klärschlammentsorgung. Ein geeignetes Instrument für diese Betrachtungsweise ist die Methodik der Ökobilanz nach ISO 14040/44. Mit dieser Methodik lassen sich alle unterschiedlichen Energieformen und Sekundärfunktionen abbilden und in einheitlichen Indikatoren darstellen, ergänzt durch weitere Umweltwirkungen wie den Treibhauseffekt.

Natürliche und künstliche Systeme zur Infiltration von Wasser (im Englischen: Managed Aquifer Recharge) werden weltweit genutzt, um Grundwasserressourcen quantitativ oder qualitativ zu verbessern. Dies erfolgt beispielsweise bei der Uferfiltration oder künstlichen Grundwasseranreicherung zur Trinkwassergewinnung, bei der Klarwasserverregnung zur weiteren Abwasserreinigung und -nutzung oder bei der Injektion von Süßwasser als hydraulische Barriere in Salzwasserintrusionsgefährdete Grundwasserleiter. Dabei nutzt man nicht nur den mengenmäßigen Ausgleich von überbeanspruchten Grundwasserressourcen, sondern auch die Reinigungsleistung des Untergrundes für eine naturnahe und meist auch kostengünstige Wasseraufbereitung. In Berlin, wo seit über 150 Jahren Trinkwasser mittels Uferfiltration gewonnen wird, wurden in Zusammenarbeit mit den Berliner Universitäten in der Vergangenheit umfangreiche Untersuchungen zur Stoffelimination bei der Untergrundpassage durchgeführt. Diese zeigten, dass auch die Konzentrationen von organischen Spurenstoffen häufig bei der Infiltration oder weiteren Grundwasserleiterpassage zurückgehen. Eine statistische Auswertung von Beobachtungen an verschiedenen Standorten ergab, dass die Mehrheit der untersuchten Substanzen wie beispielsweise Clofibrinsäure, Diclofenac und Phenazon bevorzugt unter oxischen Bedingungen abgebaut werden oder generell eine gute Entfernung erfahren. Einige wie z.B. Carbamazipin oder Sulfamethoxazol werden vor allem unter anoxisch- bis anaeroben Bedingungen entfernt. Aus diesen Beobachtungen ergab sich die Frage, ob ein optimaler Redoxzustand bzw. eine optimal Redoxabfolge für Systeme wie Infiltrationsbecken definiert werden könnte. Erste theoretische Studien erfolgten auf der Basis verfügbarer Abbaukinetiken und unter Einbeziehung weiterer Redox-sensitiver Wasserinhaltsstoffe wie Nitrat und Eisen. Diese ergaben, dass eine Aufenthaltszeit von 30 Tagen im aeroben Milieu und 100 Tagen im anoxischen Milieu während der Untergrundpassage zu einer optimalen Entfernung Redox-sensitiver Problemstoffe führt. Jedoch können bereits 15 Tage aerobe und 2 Tage anoxische / anaerobe Untergrundaufenthalt zu einem deutlichen Rückgang dieser Stoffe führen. Generell sollte jedoch berücksichtigt werden, dass unter anoxischen bis anaeroben Bedingungen mit einer Mobilisierung geogener Spurenelemente wie Eisen und Mangan zu rechnen ist. Obwohl theoretisch eine Vielzahl an Möglichkeiten existiert, den Infiltrationsbereich, die hyporheische Zone und die Untergrundpassage im Hinblick auf eine optimierte Redoxzonierung zu modifizieren oder gar zu steuern, sind nur wenige technisch tatsächlich machbar. Weitere Untersuchungen sollen nun diejenigen Möglichkeiten identifizieren, die in die Praxis übertragbar sind und zu einer Optimierung der künstlichen und natürlichen Systeme zur Infiltration beitragen könnten.

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.

Recent results show that cylindrospermopsin is more frequent and widespread in surface waters than previously assumed. Studies on the fate of CYN in sediments are lacking, but this is important if these resources are used for drinking-water production via sediment passage. Therefore, the aim of our study was to determine a) CYN retention in two sandy sediments as a function of flow rate, CYN concentration, the presence of DOM and the content of fines (1% and 4%, respectively) and b) the influence of sediment preconditioning and DOM composition of the water (aquatic DOM versus DOM released from lysed cells) on CYN degradation. Retention of CYN proved negligible under the investigated conditions. Degradation in virgin sediments showed the highest lag phases (20 days). Preconditioned sediments showed no lag phase. The presence of aquatic DOM yielded highest degradation rates (k1 ¼0.46 and 0.49 day 1) without a lag phase. Readily available organic carbon sources were preferentially metabolized and hence induced a lag phase. Thus, the presence and composition of DOM in the water proved important for both CYN degradation rates in preconditioned sediments and for the lag phase. Cylindrospermopsin degradation took place solely in the sediment and not in the water body.

Some tropical cyanobacteria have spread to temperate freshwaters during the last decades. To evaluate their further development in temperate lakes, we studied the temperature- and light-dependent growth of three invasive (Cylindrospermopsis raciborskii, Anabaena bergii and Aphanizomenon aphanizomenoides) and three native (Aphanizomenon gracile, Aphanizomenon flos-aquae and Anabaena macrospora) cyanobacterial species (Nostocales) from German lakes. We also included one potentially invasive (Aphanizomenon ovalisporum) Nostocales species. We conducted semi-continuous culture experiments and a microcosm experiment along a natural light gradient. Temperature data were used to design a model to simulate the development of selected species according to three temperature scenarios (past, present and future). Native species had significantly higher growth rates than invasive species and the potential invader A. ovalisporum at low temperatures (<= 10 °C), while the opposite was true at high temperatures (>= 35 °C). Maximum growth rates of A. ovalisporum, A. aphanizomenoides and C. raciborskii were clearly higher than those of A. bergii and the native species. Regarding light-dependent growth, significant differences were found between single species but not between all native and invasive species. The model simulation demonstrates a shift in dominance from the native A. gracile in the historic scenario to C. raciborskii populations in the future scenario, in which also the potential invader A. ovalisporum is able to establish populations in temperate lakes. Our findings suggest that any further temperature increase would promote the growth and development of Nostocales species in general, and that of the invasive species in particular, and would enable a more northward expansion of A. ovalisporum.

This paper deals with the performance and the optimisation of the hydraulic operating conditions of the A3 Water Solutions flat sheet membrane technology in a MBR pilot-plant to achieve a satisfying fouling control and also a reduction in the required aeration. Two vertically stacked modules were tested at pilot-scale at Anjou Recherche under typical biological operating conditions (mixed liquor suspended solids concentration (MLSS) = 10 g/l; sludge retention time (SRT) = 28 days; food to microorganism ratio (F/M) = 0.12 kg COD/kg MLSS/d). The use of a double-deck and of specific backwashes for this membrane technology enabled to achieve satisfying membrane performances for a net flux of 25 L h-1m-2, 20°C at a low specific aeration demand per membrane surface (SADm = 0.2Nm3 h-1m-2) which corresponds to a specific aeration demand per permeate volume unit (SADp) of 8Nm3 air/m3 permeate, which is lower than reported for many commercial membrane systems. The mixed liquor characteristics (foaming, MLSS concentration) appeared to influence the fouling behaviour of the membranes but no correlation was found with the fouling rate. However, with the new operating conditions, the system is robust and can cope with fouling resulting from biological stress and daily peak flows for MLSS concentrations in the membrane tank up to 18 g/l.