The redox conditions below an artificial recharge pond in Berlin were largely dependent on seasonal temperature changes of 0-24 °C in the infiltrate. Aerobic conditions prevailed in winter, when temperatures were low, while anaerobic conditions were reached below the pond when temperatures exceeded 14 °C. In contrast to temperature changes, cyclic changes between saturated or unsaturated conditions below the pond had only a minor effect on the redox conditions. However, the intrusion of gaseous oxygen during unsaturated conditions caused a temporary reinforced increase in oxidation of particulate organic matter. The effect of variable redox conditions on the behaviour of a number of pharmaceutically active compounds, namely carbamazepine, phenazone and several phenazone-type PhACs, was investigated. Phenazone is redox sensitive and was generally fully degraded before reaching the first groundwater well, as long as oxygen was present. When conditions turned anaerobic, phenazone was not fully eliminated. 1-Acetyl-1-methyl-2-dimethyl-oxymoyl-2-phenylhydrazide (AMDOPH) and carbamazepine are very persistent drug residues. However, results suggest that AMDOPH may be slightly degradable under aerobic conditions too, but further studies will be needed to verify this statement.

The interest in natural surface-water treatment techniques such as bank filtration and artificial ground water replenishment has increased with the growing worldwide need for clean drinking water. After detecting a number of pharmaceutical residues in groundwater samples from a bank filtration site in Berlin, Germany, the research on these compounds has focused on investigating their transport behavior during the infiltration process. In the studies presented in this paper, the fate of six pharmaceutical residues detected at concentrations up to the µg/L-level in Berlin’s surface waters was investigated. During bank filtration, the analgesic drugs diclofenac and propyphenazone, the antiepileptic drugs carbamazepine and primidone and the drug metabolites clofibric acid and 1-acetyl-1-methyl-2-dimethyl-oxamoyl-2-phenylhydrazide (AMDOPH) were found to leach from the surface water into the groundwater aquifers. They also occur at low ng/Lconcentrations in the receiving water-supply wells. Other compounds namely the antiphlogistic drug indometacine and the blood regulating drug bezafibrate which are also detected at concentrations up 100 ng/L in the surface water are efficiently removed by bank filtration. Thus, they have not been detected downstream of the first two monitoring wells. In conclusion, bank filtration was found to decrease the concentrations of some drug residues (e.g. of diclofenac, carbamazepine) or even to remove selected compounds (e.g. bezafibrate, indometacine). However, a complete removal of all potential pharmaceutical residues by bank filtration cannot be guaranteed.

Successful predictions of the fate and transport of solutes during bank filtration and artificial groundwater recharge depends on the availability of accurate transport parameters. We expand the CXTFIT code (Toride et al., 1995) in order to improve the handling by pre- and post processing modules under Microsoft EXCEL. Inverse modelling results of column experiments with tracers, pharmaceutical residuals and algae toxins demonstrate the applicability of the advanced simulation tool.

A hydraulic and physically based transport model for the catchment of a well field was set up. With the study area situated in a region strongly influenced by surrounding well galleries the boundary conditions had to be worked out during modelling and partially had to be transient. Two important processes were clarified: Bank filtrate extracted at the investigated transect is composed of 3 water qualities from horizontal layers, each with a different age and infiltration area. Sampled wells containing the different water types were identified, providing information for correct chemical interpretation. Secondly, the lake sediments show a pronounced seasonal fluctuation in their leakage coefficient, with its winter values doubling in summer, and lagging 2–4 months behind water temperature.

After installation of phosphorus elimination plants at the inflows of the eutrophic Lake Tegel and Schlachtensee, phosphorus (P) loading declined by a factor of 40 and 100, respectively. This resulted in a pronounced reduction of phosphorus concentrations in the lake water, followed by a decline of chlorophyll-a concentrations. However, for many years P release from sediments due to mineralization and desorption of sedimentary P continued. In Schlachtensee, the presence of nitrate above the sediment suppresses P release, because the Fe/P ratio is sufficient to provide enough aerobic sorption capacity. In Lake Tegel, some P release occurs even under aerobic conditions because of the low aerobic P sorption capacity of the sediments. There, nitrate could moderate the P release peaks which occur when the Fe-P cycle at the sediment water interface is disturbed by precipitation of iron sulfide after reduction of sulfate during times of high mineralization intensity. The potentially mobile P pool in the sediments of both lakes is rather small, indicating that the P release could subside after sufficient reduction of the external P load in Lake Tegel and the disruption of the internal P cycle in Schlachtensee.

The use of numerical models has become state of the art in planning, designing and analysing the urban sewage system. To evaluate the functioning of a complete system and to study the interaction of its subsystems integrated models can be used, incorporating catchment area, collection system, wastewater treatment plant and also receiving water and groundwater body. The paper introduces a structured, problem-oriented methodology for the setup of integrated models. Considering the case study of Berlin the introduced approach is illustrated. An emphasis is placed on the necessity for the selection of adequate model components. In Berlin this aspect is of particular importance for the modelling of wastewater transport through pressure mains that is governed predominantly by pump stations. Finally, the use of the Berlin model for the evaluation of a global pump station control concept is presented. It can be shown that besides the possibility of total system analysis and evaluation a major benefit from integrated modelling is the consideration of the interaction of the system’s subcomponents.