1Graduate School of Fisheries Science, Hokkaido University, Hokkaido 041-8611, 2Akkeshi Station of Japan Sea-Farming Association, Hokkaido, 088-1108 Japan
The bactericidal effect of hypochlorite produced by a continuous flow electrolyzer on hatchery waste-seawater was investigated. The number of viable bacteria in the waste-seawater was reduced more than 99% when the water was treated with hypochlorite at 0.6mg/L for 1min, and over 99.9% of bacteria was reduced when treated with 1.0mg/L for 1min. In the next experiment, one part, 2.0m3/h of hatchery waste-seawater was treated with electrolyzer and produced hypochlorite was mixed with the remaining, 16.5m3/h waste-seawater. More than 99% of viable bacterial was reduced after treatment with 0.5mg/L of total residual chlorine for 1min. The bactericidal efficacy of electrolysis was almost the same as that of ultraviolet irradiation (1.0×105μW·sec/cm2) or ozonization (TROs 0.5mg/L, 1min) of seawater. Electrolyzation is able to treat a large volume of waste seawater compared with the ultraviolet irradiation or ozonization.