Abstract
The ecotoxicological potential of 18 industrial effluents and 2 sewage effluents in Toyama Prefecture was assessed by using 5 small-scale bioassays (Microtox test, Daphnia magna immobilization test, freshwater crustacean immobilization test Thmnotoxkitf, Hydra attenuata acute test and Selenastrum capricornutum growth inhibition test). Algal assay and hydra acute sublethal assay had the most sensitive detection capacity and showed positive results out of 80% and 60% effluents tested, respectively. The comparison of 6 metal bioassay results and measured concentrations in effluents suggested the significant contribution of two metals (Zn2+, Cu2+) to the toxicity of effluent from surface processing factory. This suggestion was supported by the results of detoxification experiments with chelating agent. Other factors contributing effluent toxicity were found to be pH and volatile matters. By integrating the results of 5 bioassay in each effluents, the relative ecotoxicological potencies were compared. Finally, the comparison of toxic loading (potency×flow) showed the relatively high contributions from several large dischargers to the aquatic environment.
