Toxity Identification Evaluation for the Effluent of the Selected Sewage Treatment Plants Focused on Residual Chlorine

Abstract

 Japan Ministry of Environment started discussion on the management of industrial and municipal effluent using the bio-assays, and the test manual was publicized in March, 2013 as well as continuous discussion on the system installation. In the present study, short-term chronic toxicity tests were conducted for the effluents collected in Tokushima using the publicized method mainly referred to the USEPA's Whole Effluent Toxicity Test Methods, and the toxicants for three aquatic organisms, fish, daphnia, and algae, were characterized using the technique listed as Phase 1 in Toxicity Identification Evaluation (TIE) manual. As results, adverse effects were found for all three organisms for Plant A while relatively strong toxicity was found for algae and daphnia for Plant C effluent. The major toxicant for algae in both effluents was found to be residual chlorine confirmed by the significant toxicity reduction by the pretreatment using sodium thiosulfate and toxicity test for sodium hypochlorite.