Evaluation of Algal Growth Inhibition of Effluents for Treated Water from Tandoku-syori and Gappei-syori Johkasou Using the WET Method

Abstract

In Japan, the WET method for assessing the ecological effects of wastewater in a short-term chronic toxicity test employing aquatic creatures is now being explored for development. On the other hand, there is a johkasou, which is an individual decentralized wastewater treatment facility in Japan. However, the ecological impact of this johkasou treated water, has yet to be determined. Therefore, in this study, the tandoku-syori and gappei-syori johkasou treated water and greywater were collected from 120 sites in Saitama, and the algae growth inhibition effect of the johkasou treated water was evaluated in the algae growth inhibition test. As a result, tandoku-syori johkasou treated water had a stronger growth-inhibiting effect than gappei-syori johkasou treated water on algae. It was also confirmed that the effects of algae growth inhibition on greywater vary greatly from site to site. Differences were observed in water quality of the treated water between winter and summer, but no significant difference was observed in the inhibition of algae growth. The correlation between each sample’s water quality concentration and the inhibition of algae development in the sample water was confirmed to be low.

Keywords

• whole effluent toxicity
• drainage management
• raphidocelis subcapitata
• johkasou