Most sewer systems are still combined, collecting both wastewater and stormwater in the same pipe. Combined sewers are equipped with overflows to discharge excess water during heavy rainfall. These sewer overflows are a well-known source of surface water pollution. Reducing pollution from overflows has once again become a key focus due to new European legislation—the Urban Wastewater Treatment Directive (UWWTD). The extent of the emissions and their actual impact on the receiving surface water always depend on local conditions.

 

Through monitoring, sampling, and model simulations, we assess the emissions from overflows and their effects on surface water. We also provide advice on a wide range of measures to reduce pollution caused by sewer overflows.