2017 Volume 15 Issue 3 Pages 96-105
In Japan, there is little knowledge about the reduction in biological effects of wastewater on aquatic organisms by wastewater treatment, and a toxicant(s) contained in wastewater. The purpose of this study was to examine seasonal variation in the biological effect of the influent and final effluent obtained from a wastewater treatment plant, and to characterize the toxicant(s) in the wastewater using an algal growth test. The influents in every season tested had a growth-inhibiting effect on Pseudokirchneriella subcapitata. The final effluent in winter also had the same effect, but the final effluents in other seasons did not. The growth-inhibiting effects of the effluent in winter might be due to a reduction in the biological treatment ability caused by a decrease in water temperature, which may have led to the presence of residue of some toxicants in the effluent. A Toxicity Identification Evaluation (TIE) test suggested that the potential toxicants in the influent were non-polar organic toxicants and surfactants, among others, and that the toxicants in the final effluent were oxidants and pH-dependent toxicants. These potential toxicants appeared to be similar to chemicals suggested by the Pollutant Release and Transfer Register (PRTR) information, implying that this information is useful for identifying toxicants.