Bank filtration, i.e. the abstraction of groundwater from wells along a river or lake, thus inducing infiltration has a long history as (pre-) treatment step for drinking water production in Europe. The goal of this study is to assess whether groundwater waterworks using BF have a cost advantage compared to SWTPs if both, water abstraction and treatment processes are considered.

The herbicide Glyphosate was detected in River Havel (Berlin, Germany) in concentrations between 0.1 and 2 µg/L (single maximum outlier: 5 µg/L). As the river indirectly acts as drinking water source for the city's 3.4 Mio inhabitants potential risks for drinking water production needed to be assessed. For this reason laboratory (sorption and degradation studies) and technical scale investigations (bank filtration and slow sand filter experiments) were carried out. Batch adsorption experiments with Glyphosate yielded a low KF of 1.89 (1/n = 0.48) for concentrations between 0.1 and 100 mg/L. Degradation experiments at 8 °C with oxygen limitation resulted in a decrease of Glyphosate concentrations in the liquid phase probably due to slow adsorption (half life: 30 days).During technical scale slow sand filter (SSF) experiments Glyphosate attenuation was 70-80% for constant inlet concentrations of 0.7, 3.5 and 11.6 µg/L, respectively. Relevant retardation of Glyphosate breakthrough was observed despite the low adsorption potential of the sandy filter substrate and the relatively high flow velocity. The VisualCXTFit model was applied with data from typical Berlin bank filtration sites to extrapolate the results to a realistic field setting and yielded sufficient attenuation within a few days of travel time. Experiments on an SSF planted with Phragmites australis and an unplanted SSF with mainly vertical flow conditions to which Glyphosate was continuously dosed showed that in the planted SSF Glyphosate retardation exceeds 54% compared to 14% retardation in the unplanted SSF. The results show that saturated subsurface passage has the potential to efficiently attenuate glyphosate, favorably with aerobic conditions, long travel times and the presence of planted riparian boundary buffer strips.

Subsurface passage as utilized during bank filtration and artificial groundwater recharge has shown to be an effective barrier for multiple substances present in surface waters during drinking water production. Additionally it is widely used as polishing step after wastewater treatment. However, there are limitations concerning the removal of DOC and specific trace organics. The project ”OXIRED“ aims at assessing possibilities to overcome these limitations by combining subsurface passage with oxidation by ozone. Results from the first phase of the project have demonstrated that oxidation with ozone is a suitable method to reduce the concentrations of several relevant trace organic compounds (e.g. carbamazepine, sulfamethoxazole) and to significantly enhance biodegradation of DOC during subsequent soil passage. For efficient removal of DOC in the soil columns, specific ozone consumptions of 0.6 to 0.7 mgO3/DOC0 were sufficient. Project objectives in OXIRED-2 were to i) verify results from laboratory scale experiments at a larger scale with longer retention times, ii) study feasibility under field conditions with seasonal variations by operating a pilot unit, iii) evaluate the formation of oxidation by-products and their persistence during subsurface passage and iv) propose a standardized test protocol to analyse benefits of ozonation and artificial groundwater recharge at different sites. To investigate effects of ozonation on groundwater recharge with longer retention times, a technical scale column system with a length of 30 m and a hydraulic retention time of approximately six weeks was operated at the UBA’s experimental site in Berlin Marienfelde. Pilot studies were conducted at Lake Tegel using an ozone unit from ITT-Wedeco with a 4 g/h generator and subsequent slow sand filtration. Reduction of bromate was assessed in laboratory scale soil columns under different redox conditions. In addition, anoxic reduction of bromate was evaluated in a diploma thesis at TU Berlin. To analyse effects of DOC removal after ozonation, a standardized test protocol using recirculating columns was proposed and tested. Results from the different experiments confirmed the conclusions of the first phase of the project. Removal of surface water DOC during infiltration significantly increased with preozonation. In pilot studies, effluent DOC of approximately 4.7 mg/L after 1 d of retention time was measured, which is comparable to residual DOC from artificial groundwater recharge in Berlin Tegel after 30 days retention time [1]. In addition, strong effects of temperature on DOC removal were observed. During experiments with ozonation, overall DOC reduction decreased from approximately 40% in October to about 30% in the end of November. Biological testing of slow sand filter effluent revealed no genotoxic or cytotoxic effects in the water prior to further infiltration into the aquifer. Many persistent trace compounds were efficiently transformed during ozonation with specific ozone doses of 0.8 mg O3/mg DOC0. For example, realistic surface water concentrations of carbamazepine, sulfamethoxazole, phenazone and bentazone were reduced below the limits of quantification (LOQ). Primidone was only partly transformed during ozonation (70%). Since primidone is persistent during infiltration, a breakthrough in combined ozonation and artificial recharge can be expected. Also the substances MTBE and ETBE, the pesticide atrazine and some metabolites detected in Lake Tegel persist partially during treatment with ozone and subsequent groundwater recharge. For efficient transformation of these substances, higher ozone doses or an optimisation of the oxidation process, for example as advanced oxidation process (AOP), should be considered. Efficient reduction of the concentration of adsorbable organic iodine (AOI), an indicator for x-ray contrast media, during ozonation or infiltration was not observed. In contrast, adsorbable organic bromine decreased by 70 - 80 % during ozonation. Formation of the oxidation by-product bromate during ozonation of Lake Tegel water with a specific ozone consumption of up to 1.0 mg O3/mg DOC0 was below the limit of the German drinking water directive. Removal during subsurface passage was observed under anoxic conditions in presence of biodegradable organic carbon. Since artificial recharge after ozonation is likely aerobic, no significant reduction of bromate can be expected. Thus, formation of bromate needs to be controlled during surface water ozonation. Formation of nitrosamines was monitored in batch experiments with a specific ozone consumption of up to 1.15 mg O3/mg DOC0. No formation of nitrosamines including NDMA (LOQ: 5 ng/L) was observed. Operating a preceding bank filtration step will reduce ozone demand for efficient DOC removal. In addition, problems with particles from source water can be minimised. However, additional energy consumption for operation of extraction wells has to be taken into account. Overall, the presented results confirm that the objectives of enhanced removal of trace organics and DOC by combining ozonation and subsurface passage are well met. Further investigations need to focus on seasonal variations in long-term pilot studies and the formation, retention and toxicity of transformation products.

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.

Rural watersheds often face diffuse pollution problems due to agricultural activities. In the Ic watershed in Brittany (France), nitrate concentrations in rivers frequently exceed the EUthreshold of 50 mg-NO3 L-1, despite various actions to reduce the impact from agriculture. As a result, other solutions are considered, such as mitigation systems that can prevent transfer of agricultural pollutants from cropland to the streams. Constructed wetlands have been shown to fit this aim, because they can reach significant N removal for water residence times above ~12 hours, can be implemented decentrally within rural watersheds, while meeting cost and policy requirements. However, constructed wetlands require space, which is particularly scarce and costly in intensively used agricultural watersheds. As a consequence, it was decided to test a more area-effective solution in three pilot systems. On the one hand land-use itself was optimized (i) at site 1 by placing two wetlands with same inflow and dimension on an area of minor agricultural value adjacent to a stream (one surface and one subsurface-flow, both 20 x 10 meters) and (ii) at site 2 by building an elongated infiltration wetland (45 x 2 meters) directly in an existing drainage ditch, thus preventing any use of agricultural surface. In both cases farmers agreed to the placement of the wetlands free of charge. On the other hand it was attempted to raise the areal removal efficiency, with a focus on denitrification, since nitrate is of most concern with inflow concentrations to the sites ranging between 30 and 66 mg-NO3 L-1. This increase in denitrification is attempted (a) by increasing the range of anoxic zones within the wetlands and (b) by adding carbon sources. For (a) one wetland at each site is filled with gravel with bottom outlets to enforce underground passage. Moreover saturation level within the infiltration wetlands and thus hydraulic retention time, can be controlled at drain outlets. For (b) organically rich soil is added to both wetlands at site 1 and carbon sources are mixed with the gravel at site 2. The three wetlands have been constructed in 2010 and are currently monitored for flow and water quality at inlets, as well as at surface and subsurface outlets. The monitoring will allow the calculation of substance mass balances for the entire rain season, expected from December 2010 to May 2011.

During its passage through the City of Berlin (Germany), the quality of the River Spree is strongly influenced by combined sewer overflows (CSO), which lead to critical oxygen concentrations (DO) every year and to occasional larger fish kills. A continuous integrated monitoring concept, using state-of-the-art online sensors, was planned and started in spring 2010. It combines (i) continuous measurements of the quality and flow rates of CSO at one main CSO outlet downstream of the overflow structure and (ii) continuous measurements of water quality parameters at five sites within the urban stretch of the receiving River Spree. The first monitoring results show that continuous water quality measurements in CSO outlets and at downstream river stations are possible at high accuracy, even for comparably complex parameters such as chemical oygen demand (COD). Analysis of measured data confirms the significance of CSO discharges on receiving waters and underlines the value of continuous measurements in describing the local dynamics of the CSO and their impacts on water bodies.

During periods of heavy rainfall storm sewage volumes can exceed the capacity of combined sewer systems and overflow to surface water bodies. Combined sewer overflows (CSO) cause significant impacts on the water quality and their identification is crucial to plan CSO control programs or to fulfil legal requirements. This paper proposes and demonstrates six different methods to identify the occurrence of CSO based on information on the sewer system alone (methods 1 and 2), in combination with rain data (methods 3 and 4) or in combination with water quality data of the receiving surface water (methods 5 and 6). The methods provide different information on CSO, from occurrence to pollution load and impacts in receiving surface water. The methods introduced have all been applied to the Berlin urban water system. Based on these experiences they are compared considering the effort needed for their application, the required data and the obtained output. It is concluded that certainty of CSO identification can be increased by combining some of the presented methods.

Vier verschieden-konfigurierte Multigas-Sensorsysteme (Elektronische Nasen) sind Gegenstand von Versuchen an einer Kanalforschungsanlage der Berliner Wasserbetriebe. Die Systeme werden 6 Monate verschiedenen realitätsnahen Prozessbedingungen ausgesetzt, um im Anschluss eine Aussage zur Einsetzbarkeit der Systeme auf derzeitigem Stand der Technik im Geruchsmanagement von Abwasserkanalisationen machen zu können. Momentan ist kein Standard zum Test und zur Bewertung von solchen technischen Messsystemen unter Praxisbedingungen verfügbar. Daher wurde eine Methode entwickelt, die eine anwendungs- und innovationsorientierte Bewertung zulässt. Bewertungskriterien werden aufgestellt, orientiert an Verfahrenskenngrößen laut DIN EN ISO 9169 [3]. Die Kriterien werden an das Messkonzept der Elektronischen Nasen, sowie an die Versuchsbedingungen angepasst und erweitert. Das Versuchsprogramm ist so konzipiert, dass verschiedene Zielanwendungsfälle (wie z. B. die Planung einer Dosierstrategie mit geruchsreduzierenden Additiven) abgedeckt sind. Das Vorhaben wird zusammen mit den Berliner Wasserbetrieben und Veolia Wasser sowie in Kooperation mit evado-engineering durchgeführt.

Combined sewer overflows can lead to acute, critical conditions for aquatic organisms in receiving surface waters (Borchardt et al. 2007; FWR 1998; Harremoes et al. 1996; Krejci et al. 2004; Lammersen 1997). Based on the river type of the River Spree, CSO impacts of possible concern were identified to be high ammonia (NH3) and low dissolved oxygen concentrations (DO) (Senatsverwaltung für Stadtentwicklung 2001; Leszinski et al. 2007). For DO, existing continuous measurements from the River Spree from 2000 to 2007 were assessed in detail in the KWB report by Riechel (2009). However, Riechel (2009) neglected NH3 toxicity assessment, since no continuous NH3 measurements were available. The present report aims at filling this gap by estimating the potential for toxic NH3 concentrations in the River Spree with recent data. Based on stormwater impact guidelines for ammonia, critical total ammonium concentrations ([NH4,tot] = [NH4+] + [NH3]) were calculated and compared to continuous NH4,tot measurements in the Berlin River Spree. NH4,tot was measured i) at a heavily CSO impacted river stretch (year 2011) and ii) at a monitoring station several kilometres downstream of the combined sewer area (years 2010 and 2011). The analysis led to the following results: (i) Two years of continuous NH4,tot measurements showed clear increases in NH4,tot due to CSO but no occurrence of critical toxicity levels for cyprinid fish, according to Lammersen (1997) (ii) Maximal observed concentration of ~1.3 mg-N-NH4,tot l-1 was ~5 times smaller than the lowest existing threshold, which would need to be exceeded for 24 h to be considered as critical. The observed maximal concentration peak had a duration of only 3 h. The threshold, corresponding to the 3 h-duration would be even ~8 times higher than the observed ~1.3 mg-N-NH4,tot l-1. (iii) Ammonia toxicity would only be possible if maximal NH4,tot occurred during highest sensitivity of the river due to very high pH > 9. However, it was observed that pH drops significantly during CSO impacts due to low pH in rain water, which makes pH > 9 during CSO very unlikely. Given the results, the risk for ammonia toxicity due to CSO is judged as very low, particularly in comparison with regular problematic DO conditions after CSO events in summer.