25 巻 (2015) 1 号 p. 19-26
The environmental effects of five industrial effluents collected from Toyama Prefecture were assessed using three short-term chronic toxicity tests using freshwater organisms. All effluents were found to be toxic. Among the three tests, the crustacean and algal tests with maximum chronic toxicity unit (TUc) values more than 320 and 10, respectively, were more sensitive than the fish test. In two samples, toxicity characterization tests indicated that the adverse effects were due to the presence of heavy metals and ammonia. Furthermore, a field and on-site survey was conducted for one discharger, the effluent from which had been found to contain toxic levels of Ni. Two in-stream samples collected downstream from the discharge point showed chronic toxicity in algal and crustacean tests, although the samples collected upstream from the discharge point did not show any adverse effects. The heavy metal removal efficiency of on-site treatment facilities was assessed to examine the possibility of reducing the effluent toxicity. Among the four on-site treatment facilities that processed the effluents comprising the total discharge, one showed relatively lower Ni removal efficiency compared with the other facilities. These results suggest that improvement in the heavy metal removal efficiency of this facility is crucial for reducing the toxic effect of the effluents.