2018 Volume 41 Issue 6 Pages 179-191
Although many types of biological treatment processes have been introduced in Japan, it is unclear whether these processes can reduce the toxicity of municipal wastewater. In this research, an algal growth inhibition test using the green alga Pseudokirchneriella subcapitata was applied to municipal wastewater before biological treatment and to the final (or secondary) effluents obtained from four kinds of wastewater treatment plants that introduced, for example, an oxidation ditch process. As a result, it was confirmed that the growth-inhibiting effect of the wastewater was decreased through the oxidation ditch process, conventional activated sludge process, and anaerobic-oxic activated sludge process. On the contrary, the effect still remained even after the treatment by the anaerobic-aerobic filter process. It was also revealed that the ability of biological treatment processes to reduce the growth-inhibiting effect in winter became less effective than in summer. Much more information on the reduction ability of biological treatment processes are required because it has been suggested that the ability depends on the biological treatment process and the season.
