Fundamental Research on Effect of Sewage Treatment Process on Biological Impacts against Aquatic Organisms by Sewage Water

Abstract

The purpose of this study is to evaluate a biological effect of influent, secondary and final effluent obtained by conventional activated sludge process on aquatic organisms. Biological tests were conducted using 3 kinds of aquatic organisms （Pseudokirchneriella subcapitata, Daphnia magna and Danio rerio） referring to the draft Japanese Whole Effluent Toxicity test guidelines. These tests were repeated twice for D. magna, three times for P. subcapitata and D. rerio. As a result, some influents had some effects on all of the organisms, but secondary and final effluents had no effect. These results suggested that biological impacts by sewage water were improved by the process, and that chlorination in this study （maximum total chloride concentration: 0.87mg/l for P. subcapitata, 0.37mg/l for D. magna and 0.55mg/l for D. rerio） had no harmful effect on the organisms.