Evaluation of Water and Sediment Quality in Open Channels that Receive Effluent from Johkasou Facilities

Abstract

Treated water disposed from an alternative wastewater treatment system, named johkasou, contains several contaminants that may affect the quality of the local water environment. Thus, the evaluation of water quality, along with sediment content, may provide quantitative information about the effects of johkasou effluent in the open channels. Here, the physicochemical and microbial parameters were comprehensively examined in both the water and sediments of a johkasou drainage channel and open channels. Throughout the 3-year study period, the concentrations of physicochemical parameters were lower in the open channels compared to the johkasou drainage channel because of the high mixing ratio of the flow rate between the two channels. However, microbial parameters were consistently high in both the water and sediments of open channels. Microbial concentrations were not significantly different between upstream and downstream channels in any season, except for Escherichia coli (E. coli) in winter (the concentrations of which increased in the downstream channel that received johkasou effluent). Heterotrophic plate count bacteria and E. coli were positively correlated between water and sediments, indicating that microbial indicators may interact with the water and sediments in open channels.