Die TU-Forschungsgruppe beschäftigt sich mit dem Verhalten von DOC und organischen Einzelstoffen bei der Uferfiltration. Die Forschung soll Einblick in die Vielzahl von Einflussfaktoren geben, die das Verhalten der Organik in der Bodenpassage beeinflussen. Unterschiedliche Redoxverhältnisse, Aufenthaltszeiten und Bodenbeschaffenheiten beeinflussen den Abbau der Organik. Die Forschung im Rahmen des NASRIProjektes konzentrierte sich in der ersten Phase auf ein umfangreiches Feldmonitoring, welches im Zeitraum Mai 2002August 2005 durchgeführt wurde. Dazu wurden drei Feldstandorte in Berlin ausgewählt, an welchen ein deutlicher Einfluss von behandeltem Abwasser auf das Oberflächenwasser vorliegt. Zusätzlich wurde eine Vielzahl von Experimenten an Bodensäulenanlagen durchgeführt. Neben einem 30 mBodensäulensystem in Berlin- Marienfelde, wurden eine redoxgeregelte Bodensäulenanlage und eine temperaturgeregelte Bodensäulenanlage für die Untersuchungen aufgebaut. Die Feldund Bodensäulenproben wurden mittels DOC, SAK, LC-OCD, differenziertem AOX und Spurenstoffanalytik (HPLC-FLD und HPLC-MS/MS) untersucht. Die Ergebnisse zeigten, dass sowohl oxische als auch anoxisch/anaerobe Infiltrationsbedingungen zu einem ähnlich niedrigen DOC führen können. Unter oxischen Verhältnissen ist zur Mineralisierung des BDOC nur eine einmonatige Bodenpassage notwendig, während es unter anoxisch/anaeroben Verhältnissen aufgrund der langsameren Abbaukinetik bis zu 6 Monate dauern kann. Die Ergebnisse der DOCFraktionierung mittels LC-OCD zeigten, dass die Fraktion der Polysaccharide unter allen Bedingungen sehr schnell abgebaut wurde. Dagegen wurde für die anderen Fraktionen (Huminstoffe, Building Blocks etc.) nur eine partielle Entfernung beobachtet. Bezüglich der Spurenstoffe konnte gezeigt werden, dass das Röntgenkontrastmittel Iopromid in allen Felduntersuchungen schnell entfernt wurde. In den Bodensäulenexperimenten zeigte sich, dass die Entfernung durch Metabolisierung und nicht durch Mineralisierung zustande kam. Das Antibiotikum Sulfamethoxazole wurde unter anoxisch/anaeroben Verhältnissen effektiver entfernt (bis zu 80%), während unter oxischen Bedingungen maximal 50% der Ausgangskonzentration abgebaut wurden.

Hydrochemical conditions were evaluated at both bank filtration and artificial recharge sites in Berlin. All bank filtration sites show a strong vertical age stratification. Rather than showing a typical redox zoning with more reducing conditions in greater distance from the surface water, the redox zones are horizontally layered, with more reducing conditions in greater depth. This is believed to be an effect of the strongly alternating groundwaterlevels and by the age stratification. The redox conditions are generally more reducing at the bank filtration sites, mainly as a result of the longer travel times and operational differences. Redox conditions at all sites vary seasonally in particular at the artificial recharge site, which is mainly caused by temperature changes.

In the course of the interdisciplinary research project NASRI (natural and artificial systems for recharge and infiltration) many investigations are currently being carried out to assess the risk of break through of persistent organic substances into raw water used for drinking water supply. One part of these studies is the determination of the transport behavior of pharmaceutical residues in test sand filters, so called enclosures, equipped with sampling points at various depths. Breakthrough curves were determined for carbamazepine, primidone (both antiepileptic drugs), clofibric acid (a metabolite of blood lipid lowering agents), diclofenac, ibuprofen (both analgesic drugs) and for chloride, used as a conservative tracer. Retardation coefficients and degradation rates were obtained by using the software Visual CXTFIT. Degradation rates between 0.7 h–1 and 1 h–1 were observed for ibuprofen whereas clofibric acid, primidone, carbamazepine and diclofenac showed no or very little degradation (lambda < 0.06 h–1).

Investigations on the behaviour of different trace organic compounds at a bank filtration site at Lake Wannsee in the city of Berlin, Germany are reported. More than two years of monitoring for the bulk parameter differentiated adsorbable organic halogens (AOX) revealed a more efficient degradation of adsorbable organic iodine (AOI) and adsorbable organic bromine (AOBr) under anoxic/anaerobic conditions. 64% of AOI were removed under reducing condition, whereas under oxic conditions only ~35% were dehalogenated. One year of monitoring of the single organic pollutants Iopromide (X-ray contrast agent), Sulfamethoxazole (bacteriostatica) and naphthalenesulfonic acid (industrial chemical) showed that the redox conditions have a strong influence on the degradation behaviour of some of the monitored compounds. Iopromide was efficiently removed under oxic conditions, but no evidence for a dehalogenation under oxic conditions was found. Sulfamethoxazole showed a better removal under anoxic/anaerobic conditions (97% in 0.5 month retention time). Oxic infiltration only led to a removal of 62%, even with longer retention times of 2.8 months. The very stable 1.5-naphthalenesulfonic acid was not removed under either redox conditions.

Several physical, chemical and biological mechanisms play a role in the clogging of sediment interstices regularly observed in sand filter and infiltration basin systems. Whereas the hyporheic zone has been the focus of many investigations, little is known about the lenitic limnic zone, which is typical in lowland areas with lakes and low flow rivers. One must assume that clogging is regulated by both the build-up and the input of particulate organic matter (POM). In the present study, we collected samples from the littoral zone of Lake Tegel, Berlin, Germany, to analyze relevant carbon turnover processes. High concentrations of POM were detected in the upper sediment layer, with 3.4% ds down to 20 centimeters depth. A very high biomass of interstitial algae was found in the first 5 cm of sediment (25 µg Chl a per cm–3); this was 1000 times higher than in the lake water. The pore system of the sediment was filled to about 50% with POM, and the algae volume comprised about 25 % of POM. Only low amounts of POM were transported from the lake water downwards into the interstices, and the transport of FPOM (a few centimeters per day) was much lower than the water flow (32–260 cm d–1). The DOC concentrations in lake water (~8 mg L–1) and interstitial water (~6 mg L–1) were determined by the in situ bioactivity of interstitial organisms in addition to DOC input from lake water.

The spatial and temporal evolution of the seepage water chemistry below an artificial recharge pond was investigated to identify the impact of dynamic changes in water saturation and seasonal temperature variations. Geochemical analysis of the pond water, suction cup water and groundwater showed that during summer, nitrate and manganese reducing conditions dominate as long as saturated conditions prevail. Iron and sulphate reduction occur only locally. When the sediment below the pond becomes unsaturated, atmospheric oxygen penetrates from the pond margins leading to re-oxidation of previously formed sulphide minerals and enhanced mineralisation of sedimentary particulate organic carbon. The latter promotes the dissolution of calcite. During winter, both the saturated and the unsaturated stage were characterised by aerobic conditions. Thereby, nitrification of sedimentary bound nitrogen could now be observed because nitrate is not immediately consumed, as is the case during summer. This suggests that nitrification below the pond might be less affected by seasonal temperature changes than nitrate reduction.

The UBA’s experimental field on the outskirts of Berlin offers a unique possibility of simulating bank filtration, artificial recharge and slow sand filtration on a technical scale. The site consists of a storage reservoir (pond) with an adjacent artificial aquifer consisting of sand and gravel. Additionally the surface water can be conducted into 4 infiltration basins (two slow sand filters and two aquifer infiltration ponds). Three enclosures as well as large scale columns can be used for shorter and longer term simulation of groundwater transport. The whole site is separated from the surrounding aquifer by a layer of clay. A variety of physico-chemical parameters can be measured continuously and observed online. The travel times for the bank filtration passage determined by tracer experiments range from a few days to a maximum of 3 weeks. In the enclosures, infiltration ponds and large scale columns contact time can be varied between a few hours up to 3 months.

The paper presents the build-up of a model for the integrated simulation of the sewage system of Berlin, Germany, focusing on the catchment of the wastewater treatment plant Ruhleben. The Ruhleben catchment, draining 185 km² and a population of 1.38 million inhabitants is characterised by its high portion of combined sewerage. The model comprises the collection system, pump stations, pressurised mains and the wastewater treatment plant. Hydraulic and quality processes are taken into account. A preliminary assessment of the sewage system and the analysis of historical operational data showed a high potential concerning global real-time control of the pump stations. Three different global control scenarios have been studied on the basis of a long time simulation over 50 days and compared with a local control regime. The results show that the coordinated operation leads to a reduction of total emissions. Main improvements can be achieved concerning the discharges from combined sewer overflows. These improvements are of major significance due to the high hazard potential of combined sewer overflows.

A modelling study was carried out to provide a process-based quantitative interpretation of the biogeochemical changes that were observed during an ASR experiment in which reclaimed water was injected into a limestone aquifer at a field-site near Bolivar, South Australia. A site-specific conceptual model for the interacting hydrodynamic and biogeochemical processes that occur during reclaimed water ASR was developed and incorporated into an existing reactive multi-component transport model. The major reactive processes considered in the model were microbially mediated redox reactions, driven by the mineralisation of organic carbon, mineral precipitation/ dissolution and ion exchange. The study showed that the geochemical changes observed in the vicinity of the ASR well could only be adequately described by a model that explicitly considers microbial growth and decay processes, while an alternative, simpler model formulation based on the assumption of steady state biomass concentration failed to reproduce the observed hydrochemical changes. However, both, the simpler and the more complex model approach were able to reproduce the geochemical changes further away from the injection/extraction well. These changes were interpretated as a result of the combined effect of ion exchange, calcite dissolution and mineralisation of dissolved organic carbon.