Reduction of Combined Sewer Overflow Quality by Application of the Coagulation Process

Abstract

In order to store the bulk of storm water runnoff German combined sewer systems are equipped with detention facilities. In spite of this fact, combined sewer overflow discharge contributes a considerable part to the existing river pollution. Reducing the amount of the discharged pollution load is the objective of a research project. At a large pilot plant investigations are ongoing into the effect of the coagulation process being applied at combined sewer detention tanks. In several experimental phases the influence of different variation parameters upon its efficiency is tested. First results show the general benefit of the coagulation process removing COD and total phosphorus. The attainable reduction effect depends on the constructive and hydraulic conditions within the detention tank to a high degree. Considering the now available 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.