Stormwater runoff is the largest untreated source of potentially high loads of trace organic substances discharged to urban surface waters. Each year about 74% or 44 million m3 of the stormwater runoff are discharged mostly untreated into Berlin’s surface waters. This corresponds to approx. 5% of the annual outlet of the urban course of the Spree River to River Havel. Initial studies from Switzerland covering selected trace organic contaminants (e.g. biocides, plastic ingredients, combustion products) occurring in rainwater runoff and surface waters demonstrate high concentrations of these substances with possible relevance to aquatic organisms or human uses.
Following the update of the list of priority substances under the EU Water Framework Directive which already contains a provision regarding polycyclic aromatic hydrocarbons (PAHs), other stormwater-borne trace organic contaminants (e.g. terbutryn) are likely to be considered for regulation.
The current strategy aims to reduce the micropollutant level in urban surface waters through the implementation of advanced treatment steps in sewage works. However, these achievements might be diminished by the high loads in the untreated storm water runoff discharged into surface waters. Should the overall analysis of the Berlin situation reveal that the city’s stormwater runoff is a significant source of trace organic contaminants, the current prevention strategies would have to be adjusted or upgraded.
The project OgRe aims to support Berlin’s strategy related to the reduction of trace organic contaminants by (i) describing a first set of locally important substances occurring in stormwater runoff, (ii) estimating the annual loads of trace substances which are discharged via stormwater runoff into the receiving waters and (iii) comparing them with relevant pollution loads originating from other entry paths.
Paper (open access) in the journal Water: Micropollutants in urban stormwater runoff of different land uses
Data sets with measurement results: concentrations in storm sewer and concentrations in urban stream
More project publications produced in the OgRe project are available here.