Quality and importance of municipal stormwater runoff from separate system

For the determination of the quality and flow rate of stormwater from the separate system in Berlin flow measurements were carried out and flow-proportional samples were taken in the storm sewer of a 32.39 ha large drainage area which is used for residential and commercial purposes in the years 1989 and 1990. The concentration of several parameters in the stormwater is higher than in the treated wastewater of the well running sewage plant Ruhleben and partially exceed the minimum requirements concerning wastewater discharge into the receiving waters. In comparison to wastewater both in the investigated drainage area and for the estimation in the western part of Berlin, the annual load of several parameters is equal in the stormwater. Hence, zinc, lead, copper, iron, aluminium, phosphorus, filterable solids and organic compounds in the stormwater of the separate system are an important pollution factor for the receiving waters in Berlin. With the upgrading of the wastewater treatment plants in Berlin, the significance of the stormwater as a factor for the load of receiving waters increases. Thus, it is necessary to ensure a good treatment of the stormwater in the storm sewer before it will be discharged into the lakes and rivers. (orig.)