The project OXIRED was initiated to assess the potential of a combination of natural systems such as bank filtration (BF) and artificial recharge (AR) and oxidation processes in order to improve the degradability of DOC and the removal of trace organics during water treatment. In this literature study, treatment schemes, which combine subsurface passage with oxidation processes, were evaluated with regard to the potential removal of DOC and trace organics, by theoretical considerations and case study analyses. The objectives were i) to estimate the degradation of bulk organic matter and trace organics in such combined systems, ii) to assess the potential for toxic by-products and iii) to describe different possible schemes combining natural systems (BF & AR) and oxidation processes. Available data generally shows good removal of the substances identified as persistent during BF & AR by oxidation processes. Carbamazepine, for example, is poorly degradable during bank filtration, but ozonation leads to a transformation of more than 97%. If ozonation alone does not suffice, advanced oxidation processes may enhance the transformation. E.g. literature gives a values of < 50% removal of Iopamidol by ozonation. However, transformation increases up to 88% using advanced oxidation processes, such as O3/H2O2 and O3/UV. Investigations on the formation of possible toxic by-products have shown the general possibilities to control the formation of bromate by decreasing the pH, avoiding free dissolved ozone in the reactor and/or by adding H2O2. Only a low risk of exposure of the potentially forming nitrosamines in drinking water after artificial recharge could be identified. Especially the cancerogenic metabolite NDMA is degraded during subsurface passage. Three reference treatment schemes were identified: (A): surface water is treated via oxidation before infiltration into artificial recharge ponds.(B): a river bank filtration with short retention times (<5 days) is used as a pretreatment step before the successive oxidation and artificial recharge (AR). (C1/C2): oxidation is applied subsequent to subsurface passage after bank filtration and artificial recharge. Due to the possible formation of toxic by-products and the increased assimilable DOC in scheme C (Examples for C1 Mülheim Styrum-East and Le Pecq Croissy & C2 Prairie Waters Project and the Bi´eau Process) a post-treatment including disinfection after oxidation is necessary. Additional post-treatment in schemes A (implemented at Mülheim Dohne) and B depends on the redox conditions and the travel times during the subsurface passage. However, although there is a lack of practical data, the enhancement of BDOC via oxidation prior to the underground passage seems theoretically more promising than the reverse configuration. It is therefore recommended that any further experimental program in OXIRED should focus on the schemes A and B and include a cost-benefit analysis of the additional first BF step.

Over the past decade, membrane bioreactors have been increasingly implemented to purify municipal wastewater. However, even with submerged modules which offer the lowest costs, the membrane bioreactor (MBR) technology remains in most cases more expensive than conventional activated sludge processes. In addition, the European municipal MBR market is to date a duopoly of two non-European producers, despite many initiatives to develop local MBR filtration systems. In 2005, the European Commission decided to finance four projects dedicated to further technological development of MBR process: the four projects AMEDEUS, EUROMBRA, MBR-TRAIN and PURATREAT were implemented from October 2005 up to December 2009 and joined their efforts within the coalition “MBR-Network” (www.mbr-network.eu). The present report synthesises the major outcomes of the project AMEDEUS, conducted from October 2005 up to May 2009. The AMEDEUS research project aimed at tackling both issues of accelerating the development of competitive European MBR filtration technologies, as well as increasing acceptance of the MBR process through decreased capital and operation costs. The project targets the two market segments for MBR technology in Europe: the construction of small plants (semi-central, 50 to 2,000 population equivalent or p.e., standardized and autonomous), and the medium-size plants (central, up to 100.000 p.e.) for plant upgrade.

The project Aquisafe assesses the potential of selected near-natural mitigation systems, such as constructed wetlands or infiltration zones, to reduce diffuse pollution from agricultural sources and consequently protect surface water resources. A particular aim is the attenuation of nutrients and pesticides. Based on the review of available information and preliminary tests within Aquisafe 1 (2007-2009), the second project phase Aquisafe 2 (2009-2012) is structured along the following main components: (i) Development and evaluation of GIS-based methods for the identification of diffuse pollution hotspots, as well as model-based tools for the simulation of nutrient reduction from mitigation zones (ii) Assessment of nutrient retention capacity of different types of mitigation zones in international case studies in the Ic watershed in France and the Upper White River watershed in the USA under natural conditions, such as variable flow. (iii) Identification of efficient mitigation zone designs for the retention of relevant pesticides in laboratory and technical scale experiments at UBA in Berlin. The present report provides a review of the properties and existing mitigation experience of the two herbicides Atrazine and Bentazone, which will be examined exemplarily in (iii). Whereas Atrazine is clearly the pesticide of greatest concern in the USA, Bentazone is mainly an issue in Europe with an increasing tendency. The sorption of Atrazine and Bentazone on soils is moderate. Moderate sorption in combination with medium to high persistency makes these compounds relatively mobile; therefore they can usually be observed in surface waters in general and in ground waters near places of their application. First experiences show that mitigation systems can be effective measures to decrease their concentrations by supporting biotic and abiotic dissipation processes, mainly at high residence times. Adding organic matter can improve adsorption of Atrazine and Bentazone, an important dissipation process in these systems. Degradation rates for Atrazine and for Bentazone can be increased by implementing highly microbiologically active conditions which can usually be accomplished in the presence of external carbon sources. While mineralization of both herbicides is favoured in aerobic -environments significant degradation of Atrazine was also observed under anaerobic conditions. A great number of open questions remain on how to design a mitigation system which is adequate to reduce herbicides in drainage water. For instance, there is no specific information on the degradation of diluted and adsorbed forms of the herbicides, very little information about necessary residence times, adsorption constants, half lives and leaching behaviour in specific substrates or comparable designs. Moreover, the influence of nitrogen, which is present in drainage water at high concentrations, on degradation of Atrazine and Bentazone remains uncertain. Finally, the behaviour of Atrazine and Bentazone (contained in agricultural drainage water) in mitigation systems in general and in bioretention swales in particular is poorly studied. Realistically, mitigation systems would only be implemented if they also allow significant reduction of nitrates. Given the existing knowledge, systems with both aerobic and anoxic zones are likely to bring most successful results regarding both herbicides and nitrates; though they may be difficult to implement. Both for nitrates and pesticides, the presence of external organic carbon sources (with a combination of fast accessible and sustainable substrate partitions) seems to be a good basis for dissipation processes and effective reduction.

Managed aquifer recharge provides efficient removal for many organic water constituents but it is a difficult task to quantify removal under field conditions: Observed concentrations often scatter and may be biased by subsurface mixing of different waters. Removal efficiency is affected by different environmental parameters, such as redox potential, travel times, threshold values, and also field site specifics. In addition, it is crucial to know the corresponding surface water concentration for all samples. We developed a method, which overcomes these difficulties, quantifies the efficiency and removal kinetics and is applicable to extensive databases. It combines both, statistical and graphical evaluation which allows the determination of precise values and also interpretation based on expert knowledge. The database of this study was collected within the NASRI project between 2002 and 2005 at two bank filtration sites (Tegel BF, Wannsee BF) and one basin aquifer recharge site (Tegel AR) in Berlin. In total, 38 organic constituents were analysed (Table 1).

The study aims at assessing in long-term trials a gravity-driven ultrafiltration pilot plant designed for a capacity of 5 m3/d. The unit was operated in South Africa with Ogunjini surface water and was run with restricted chemical intervention or maintenance (no backflush, no aeration, no crossflow and no chemical). Under South African environmental conditions and with direct filtration of the river water and only one manual drainage of the membrane reactor every weekday, the unit could fulfil the design specification in terms of water production (5 m3/d) as long as the turbidity of the raw water remained in a reasonable level (up to 160 NTU), with a filtration flux typically 4 to 6 L/h.m² (corrected at 20°C). This value was in the same range as the lab results and was consistent with the first phase results (around 5-7 L/h.m² after biosand filtration). However, the flux dropped significantly to a range of 2 to 4 L/h.m² after a rain event resulting in a turbidity peak over several days up to > 600 NTU. This demonstrated that for variable raw water types with expected turbidity peaks above 100 NTU, a pre-treatment would be required for the system (biosand filter or other). The performance of microbiological tests confirmed the integrity of the membrane and the ability of the system to achieve complete disinfection.

In the densely populated semi-arid territory around Delhi, the water demand is rising continuously, while the surface- and groundwater resources are threatened by contamination and overexploitation. This is a typical scenario in many newly industrialising and developing countries, where new approaches for a responsible resources management have to be found. Bank filtration holds a great potential, thus being a low tech method and benefiting from the storage and contaminant attenuation capacity of the natural soil/rock. For this study, three field sites have been constructed to investigate bank filtration in different environments in and around the megacity with a main focus on inorganic contaminants. Hydraulic heads, temperature gradients and hydrochemistry of surface water and groundwater were analysed in three different seasons. Depending on sitespecific conditions, distinct hydrogeological conditions were observed and both positive and negative effects on water quality were identified. Most concerning issues are the impact of anthropogenic ammonia, the mixing with ambient saline groundwater and the mobilisation of arsenic during the reductive dissolution of manganese- and iron(hydr)oxides. Positive aspects are the dilution of contaminants during the mixing of waters from different sources, the sorption of arsenic, denitrification, and the precipitation of fluoride under favourable conditions.

The quality of the River Spree during its passage through the city of Berlin is mainly influenced by the discharge of treated effluent from waste water treatment plants and by combined sewer overflows (CSO). CSO are discharged diffusely and during short periods of time leading to acute impacts like oxygen depletion and locally increased ammonia concentration in the river. They are dominant stress factors to Berlin’s lowland River Spree and its biocenosis. In order to improve the water quality of the River Spree, measures limiting the emissions of CSO are envisaged such as utilization of in-pipe storage capacities, implementation of weirs for real-time control, construction of additional stormwater tanks. In order to build an efficient and immission oriented strategy with the different available solutions and to be able to cope with future challenges the Berlin Centre of Competence for Water (KWB), Berliner Wasserbetriebe, Veolia Water and the Berlin Senate of Environment are conducting two projects, the EU project PREPARED and the MIA-CSO project. An impact-based CSO management instrument is being developed with the aim to evaluate measures of CSO control. It consists in (i) a river water quality/ecosystem model that will be used to simulate water quality processes in the receiving water and (ii) a methodology to identify critical water quality situations occurring in the Spree River. For model adaptation, calibration and validation an integrated monitoring is conducted. The monitoring consists in (i) continuously measuring the quality and flow of CSO discharges at one representative network location and (ii) in parallel, continuously monitoring water quality parameters at 5 sites within the impacted stretch of the Spree River. The concept of the integrated monitoring, i.e. definition of monitoring sites as well as monitoring strategy and design will be presented during the M3 Workshop.

To gain better understanding of the impact of combined sewer overflows (CSO) on the chemical and ecological status of lowland rivers and to evaluate the effect of CSO control measures a planning instrument for impact-based CSO management is being developed in Berlin, Germany. After completion the model-based planning instrument will be used by the Berlin water and wastewater utility and the water authority for scenario analysis of CSO management strategies. To adapt the planning instrument to their respective needs and to guarantee an efficient transfer of the results a specific project structure was established. Through direct participation in project management, technical and scientific work as well as demonstration the end-users can influence the development and provide technical input on local issues. First project results show the relevance of CSO impacts compared to the background condition of the Berlin river system and the need for additional measurements to provide data for model adaptation, calibration and validation.

Stormwater impact guidelines for dissolved oxygen (DO) were applied to the Berlin River Spree, which (a) receives the effluents of more than 100 combined sewer discharge points and (b) is subject to significant anthropogenic background pollution. Discrimination of DO depressions, which are the direct result of combined sewer overflows (CSO) from DO depressions which are not related to CSO was achieved by combining stormwater impact guidelines with the analysis of data for: (i) rain events before critical DO depressions, (ii) water temperature (T) and conductivity as indicators for CSO impact in the river and (iii) T and DO before critical DO depressions to assess the effect of background pollution. Results indicate that the River Spree is in a critical state regarding DO for two main reasons: (a) upstream of the stretch with CSO discharge points because of background pollution and (b) downstream of the stretch because of CSO. Highly critical situations with DO < 2 mg L-1 only occurred under CSO influence. Nevertheless, the analysis underlines the importance of measures to reduce both CSO and background pollution in urban rivers.