2021 Volume 44 Issue 4 Pages 103-114
The effluents from wastewater treatment plants in Kyoto City are disinfected with chlorine or ozone before they are discharged. We measured the concentrations of disinfection by-products with chlorine or ozone and their formation potentials with chlorine in the effluents. Each effluent had its own characteristics on the disinfection by-product formation potential, which was considered to depend on the water quality of each sewage influent. The chloroform formation potential decreased after the disinfection of effluents with ozone. Conversely, the concentration of formaldehyde and its formation potential increased. However, the difference between formaldehyde formation potential and formaldehyde concentration decreased. We considered that the concentration of formaldehyde precursors decreased after the disinfection with ozone because the precursors were oxidized and converted to formaldehyde. Additionally, the concentration of formaldehyde in the effluent decreased downstream of the discharging point. Therefore, we concluded that the disinfection of effluents with ozone reduced the loads of formaldehyde, its precursors, and the formation potentials of some disinfection by-products on the downstream area.
