RSF_Sim – A simulation tool to support the design of constructed wetlands for combined sewer overflow treatment

Treatment of combined sewer overflow (CSO) in constructed wetlands (CWs) has proven to be highly efficient in reducing negative impacts on receiving water bodies. In Germany retention soil filters (RSFs) were developed for this purpose. RSFs are basically vertical subsurface flow constructed wetlands combined with retention basins. So far dimensioning of RSF is based only on long term rainfall-runoff simulations. Effluent quality is not considered. This paper presents a simple phenomenological model for RSF. In combination with sewer quality models it can predict the long term emissions from a particular RSF. The model will support the design of filters to meet specific emission requirements. First results of calibrating and validating simulation outputs on measurement data show, that simple mass and volume balances with only few input parameters can be sufficient for the given purpose.