Induced by well abstraction, surface water infiltrates into Berlin aquifers and is used for drinking water production. The advantage of bank filtration is the capability of the subsurface to remove contaminants. Because a large proportion of the surface water in Berlin originates from treated effluents, the system is a semi-closed water cycle relying partly on indirect wastewater reuse.
Processes accompanying bank filtration and artificial recharge are currently studied in Berlin within a multidisciplinary project initiated by the KWB (Kompetenzzentrum Wasser Berlin) as a cooperation of the Berlin Water Works (BWB), the Technical and the Free University of Berlin, the German Environmental Protection Agency (UBA) and the Institute of Ecohydrology and Inland Fisheries (IGB) named Nasri (Natural and Artificial Systems for Recharge and Infiltration). It focuses on the behaviour and removal of, for example, pathogens, microsystens, organic pollutants as well as pharmaceutically active compounds during underground passage.
Within NASRI, the Free University evaluates the hydrogeology, hydraulics, geochemistry and hydrochemistry of the field sites. Wastewater indicators (e.g. Cl-, B, EDTA, Gd-EDPA), stable isotopes (18O, 2H) and Tritium/Helium age dating are used to calculate travel times to drinking water wells and proportions of bank filtrate in individual wells. The tracer results serve as a basis for the interpretation of the fate and behaviour of potential contaminants (e.g. drug residues or organic pollutants) analysed by project partners.