Micropollutants in stormwater runoff – citywide loads and comparison with sewage inputs.
Beside inputs from wastewater treatment plants, untreated stormwater runoff can also be an important source of pollutants affecting urban surface waters. To evaluate the relevance of micropollutants in urban stormwater runoff for the city of Berlin, an event-based, one-year monitoring program was conducted in five homogeneous catchments of different urban structure types. Volume proportional samples were analysed for a comprehensive set of ~100 micropollutants (e.g. biocides/pesticides, plasticisers, flame retardants, PAH, heavy metals) as well as standard parameters (TSS, total P, phosphate, ammonium, COD, BOD). Micropollutant concentrations found in stormwater runoff were extrapolated to annual loads for the city of Berlin (impervious connected area of ~170 km2) based on the concentration patterns found in each of the five specific city structure types. Results show that micropollutants of several substance types can enter Berlin surface waters at loads in the order of 10-700 kg/yr via stormwater runoff. These loads are in a similar order of magnitude as micropollutants that enter Berlin surface waters via (treated) sewage, such as pharmaceutical residues carbamazepine or ibuprofen.