Reduction in toxicity of organic priority pollutants by pilot-scale conventional wastewater treatment process

Static acute toxicity tests with fathead minnows,Daphnia magna, and rainbow trout were used to demonstrate the effectiveness of a pilot-scale conventional wastewater treatment system in detoxifying a raw municipal wastewater that continuously received a mixture of 22 organic priority pollutants. Wastewater from the City of Cincinnati (Ohio) was added to two parallel pilot-scale (control and experimental) conventional activated-sludge wastewater treatment systems. The effect of chlorination on the acute toxicity of effluent from the experimental system was also investigated. The system typically reduced the organic priority pollutants by 89 to >99%, and both systems provided excellent treatment of conventional pollutants. Even though toxicity reduction as high as 90% was achieved, significant toxicity was present in the experimental effluent. The study clearly supports the premise that organism responses should be considered, in addition to chemical and conventional pollutant characterization, to determine the quality of a wastewater discharge.