An Integrated Methodology for the Impact Assessment of the Design and Operation of the Sewer - Waste Water Treatment Plant System on the Receiving Water Quality

The poster deals with an integrated methodology for the assessment of the impacts of alternative sewer and waste water treatment plant (WWTP) management scenario’s on the quality of the receiving waters. The input time series for the flows and concentrations at the combined sewer overflow (CSO) structures and at the treatment plant intake are obtained through a continuous sewer simulation model. The WWTP model is based on a structured dynamic model describing COD removal and final settling. Special emphasis is put on the sludge inventory of the plant since this is considered to be the main problem area under storm conditions. The impacts of the emissions at the CSO structures and from the WWTP is simulated with the help of a river quality model. The methodology is illustrated on the combined sewer network of Brussels. Scenario’s without and with CSO control measures in the sewer are considered. At the treatment plant, the simulation study evaluates the effect of potential control strategies such as ratio control of the RAS, step feed and retention of first flush in a storm tank.