Edwardsiella tarda (E. tarda) and Vibrio harveyi (V. harveyi) are known as representative fish pathogenic bacteria that cause serious mortality among fish. In order to alleviate the damage caused by the microbial infection, it is necessary to apply a disinfection technique in the aquaculture system. Chlorination, which has been widely applied in conventional disinfection process for drinking water treatment plants, can be employed to effectively control these bacteria. Nevertheless, indiscriminate use of free chlorine might lead to the formation of harmful disinfection by-products in seawater (e.g. bromoform and brominated haloacetic acids) and can cause economic loss in the aquaculture system. Therefore, it is important to optimize the concentration of disinfectant based on inactivation kinetic information. Although a previous study has been tested a potential use of free chlorine for inactivation of E. tarda and V. harveyi, their inactivation kinetics have not been studied in seawater. This study investigates the microbial inactivation kinetics of E. tarda and V. harveyi by free chlorine. Experiments were performed by varying pH, temperature, the concentration of free chlorine, and the concentration of dissolved organic matter (DOM) in order to quantify disinfection efficacy of free chlorine in deionized water and seawater. At pH 7 deionized water, CT values (achieving 1 log inactivation) of free chlorine for E. tarda and V. harveyi inactivation were 0.0149 and 0.0150 mg min/L, respectively. However, CT values in seawater increased both nearly 3.5-folds (0.0520 and 0.0551 mg min/L, respectively), which is considered that the bromide ion in seawater affects the speciation of free chlorine and disinfection efficacy.

Inactivation of E. tarda and V. harveyi by free chlorine

2019 Fall National Meeting

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