Seasonal Variation in Ability of Wastewater Treatment for Reduction in Biological Effects Evaluated Based on Algal Growth

摘要

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.