Drinking-water production in urban environments bank filtration in Berlin

Berlin relies on induced bank filtration from a broad-scale, lake-type surface water system. Because the hydraulic conductivity of the lake sediments is low, infiltration only occurs close to the more permeable shore zones. Using multiple environmental tracer methods, a strong vertical age stratification of the bank filtrate could be shown. Travel times are generally long and vary throughout the upper aquifers from a few months near the ground surface to several decades in greater depth. Infiltration is mostly anoxic and redox zones were found to be vertically stratified too, becoming more reducing with depth. Because Berlin's watercourses contain a proportion of treated municipal sewage a number of wastewater residues, e.g. pharmaceutical residues, were detected in surface water and groundwater. While the majority of the pharmaceutical residues studied were efficiently removed during underground passage, some substances (AMDOPH, primidone and carbamazepine) were found to be very persistent.