ABSTRACT
The environmental effects of sewage effluent and combined sewer overflows (CSOs) in Toyama, Japan were evaluated using toxicity tests and chemical analyses. Chronic and sub-chronic tests with three freshwater organisms (Danio rerio, Ceriodaphnia dubia, and Raphidocelis subcapitata) were applied to samples. Seven effluent samples, five samples from CSOs including the first flush and the following overflows of CSOs, and two samples from river water (upstream and downstream) were collected. Of the seven effluent samples tested, four demonstrated toxicities to aquatic organisms. Water analyses suggest that residual chlorine is responsible for toxicity to algae, while linear alkyl benzene sulfonates do not contribute to toxicity. The chronic toxicity unit (TUc), total organic carbon (TOC), and coliform count were higher in the first flush than in the other CSOs samples. This section also evaluated the ecological impacts of sewage effluent using PRTR data and compared the results from the two approaches. The PRTR data tended to overestimate toxicity in comparison to the observed toxicity. Except effluent samples, the toxic influence was the strongest on crustaceans among three freshwater organisms. Thus, toxicity identification evaluation (TIE) procedures using daphnia were applied to the three samples.
