Decentralized Sustainable Urban Drainage Systems – Development of a Stormwater Treatment Train for Contaminants from Multiple Sources in Residential Areas

The densification of cities and an increasing amount of impervious surfaces support negative effects of global warming, such as the urban-heat-island-effect and an increase in urban runoff volume. Innovative rainwater management can decrease these effects. Large volume multi-use rainwater cisterns collect urban runoff from green-roofs, façades, and traffic surfaces within a residential area. The natural thermal energy from rainwater is fed into cold local heating networks. In combination with geothermal installations, the energy supply is high enough to meet energy demands for heating or cooling of a residential quarter throughout the year. The same runoff is used to irrigate the urban green spaces including green roofs. This supports the urban-water-cycle by on spot percolation and decreases the urban-heat-island-effect by evapotranspiration.

The urban runoff needs to be treated prior to its multi-purpose use. Therefore, the chair of Urban Water Systems Engineering (SWW) in cooperation with “FRÄNKISCHE Rohrwerke Gebr. Kirchner GmbH & Co. KG“, will develop a stormwater treatment train for simultaneous removal of contaminants from multiple sources in residential areas. Other techniques like direct infiltration into the ground (façade-runoff and some roof-runoff) or separate treatment of different runoffs require more space and multiple treatment systems for different contaminants. The aim of this project is to find a substrate mixture to treat traffic-, façade- and green-roof-runoff all at once. The focus is the simultaneous treatment of biocides, total suspended solids, heavy metals, nutrients as well as organic contaminants.

Recently biocides from facades and green roofs moved into the focus, as a potential threat for the environment. Especially, green roof related biocides are gaining interest in the scientific community, due to an increasing amount of green roofs in urban areas. The SWW In cooperation with the “Optigrün international AG” is investigating on the impact of retention time and green roof type on the leaching behavior of biocides. In a further experiment both partners will test the urban runoff treatment capabilities of different green roof systems.