Several kinds of managed aquifer recharge techniques provide very good purification of surface water since more than 100 years. In order to maintain a reliable supply of clean water, they are becoming increasingly popular all over the world. Especially bank filtration methods require low technical effort. Exemplarily, at a test site at Lake Tegel, Berlin, Germany, the hydraulic processes of infiltration are modelled. By means of 3D long term regional and transient hydraulic modelling it was detected that the existing approaches for determining the leakance induce large errors in the water balance and describe the infiltration zone insufficiently. The leakance could be identified to be triggered by the groundwater table, causing air exchange and intrusion of atmospheric oxygen, which reduces clogging by altered redox conditions by at least one order of magnitude. This causes that changes of the groundwater table are mitigated much more than previously assumed. Taking these findings into account, a transient water balance is determined and bank filtration ratios are quantified.

The spatial distribution of confining layers within a system of two aquifers strongly affects the hydraulics and sensitivity to pollution. The test site is located close to a well field. Wells are switched with short intervals and hydraulic heads are recorded in several observation wells. Because the absolute levels of simulated hydraulic heads do not always coincide with the measurements, the model is calibrated with short term head variations. The characteristic shape of the hydraulic heads at each observation wells contains sensitive information about the structure of the aquifer. A numerical technique is developed which enables to simulate the spatial distribution of the confining layer. The method comprises the use of pilot points and regularisation technique. Cross validation is carried out in order to show the results are physically based. The method is shown to provide significant results even under non optimal conditions.

Within the scope of the interdisciplinary NASRI research project (Natural and Artificial Systems for Recharge and Infiltration) dealing with river bank filtration processes at Berlin water works, a semi-technical column experiment is ongoing since January 2003 to simulate river bank filtration. Here a 30 m long ensemble of 6 soil columns is operated by surface water sampled from Lake Tegel (Berlin, Germany). In April 2004, oxic conditions in the column ensemble were forced to change in anoxic by gassing the flushing solution supply with nitrogen gas. The objective of reactive transport modelling was to (i) identify the main biogeochemical processes and the governing redox conditions within the soil column system during flushing as a conceptual model for river bank filtration and to (ii) verify the observed hydrochemistry of the pore water.

In several slow-sand-filter experiments the behaviour of phages during the subsurface passage was measured and modelled. Here the focus is on the effect of the velocity. The observed data show a strong effect of decreasing filter efficiency with increasing velocity. Using a modelling approach, which is based on the transport differential equation, the theoretical influence of velocity on filter efficiency is examined. Finally an extrapolation of the results to large scale filtration units or bank filtration processes is attempted.

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.

In several slow-sand-filter experiments the behaviour of phages during the subsurface passage was measured and modelled. Here the focus is on the effect of the velocity. The observed data show a strong effect of decreasing filter efficiency with increasing velocity. Using a modelling approach, which is based on the transport differential equation, the theoretical influence of velocity on filter efficiency is examined. Finally an extrapolation of the results to large scale filtration units or bank filtration processes is attempted.

Reactive multicomponent transport modeling was used to investigate and quantify the factors that affect redox zonation and the fate of the pharmaceutical residue phenazone during artificial recharge of groundwater at an infiltration site in Berlin, Germany. The calibrated model and the corresponding sensitivity analysis demonstrated that temporal and spatial redox zonation at the study site was driven by seasonally changing, temperature-dependent organic matter degradation rates. Breakthrough of phenazone at monitoring wells occurred primarily during the warmer summer months, when anaerobic conditions developed. Assuming a redoxsensitive phenazone degradation behavior the model results provided an excellent agreement between simulated and measured phenazone concentrations. Therefore, the fate of phenazone was shown to be indirectly controlled by the infiltration water temperature through its effect on the aquifer’s redox conditions. Other factors such as variable residence times appeared to be of less importance.