REDUCTION OF COMBINED SEWER OVERFLOW QUALITY BY APPLICATION OF THE COAGULATION PROCESS

In order to store the bulk of storm water runnoff German combined sewe r systems are equipped with detention facilities. In spite of this fac t, combined sewer overflow discharge contributes a considerable part t o the existing river pollution. Reducing the amount of the discharged pollution load is the objective of a research project. At a large pilo t plant investigations are ongoing into the effect of the coagulation process being applied at combined sewer detention tanks. In several ex perimental phases the influence of different variation parameters upon its efficiency is tested. First results show the general benefit of t he coagulation process removing COD and total phosphorus. The attainab le reduction effect depends on die constructive and hydraulic conditio ns within the detention tank to a high degree. Considering the now ava ilable results it is expected that the application of the coagulation process within combined sewer detention tanks will be profitable when high standards for the quality of receiving waters are claimed.