Comparison between OCl^--injection and in situ electrochlorination in the formation of chlorate and perchlorate in seawater

To prevent biofouling from occurring in the cooling systems of coastal power plants, chlorine is often added to the cooling water. In this study, we have evaluated the fate of the total residual oxidants and the formation of inorganic chlorination byproducts including ClO₃ ^- and ClO₄ ^- during in situ electrochlorination with seawater. Then, the results were compared with those during direct OCl^--injection to seawater. The in situ electrochlorination method based on Ti/RuO2 electrodes produced much less ClO₃ ^-, while a similar level of total residual oxidants could be achieved with a reaction time of 5 min. Moreover, no ClO₄ ^- was observed, while the direct OCl^--injection system could still result in the production of ClO₄ ^-. The less or no production of ClO₃ ^- or ClO₄ ^- by the electrochlorination of seawater was mainly attributed to two reasons. First, during the electrolysis, the less amount of OCl^- is available for ClO₃ ^- formation. Secondly, the formation of ClO₃ ^- or ClO₄ ^- is affected by the electrode material. In other words, if the electrode material is carefully chosen, the production of harmful reaction byproducts can be prevented or minimized. In short, based on the results from our study, electrochlorination technology proves to be a marine environmentally friendly method for controlling biofouling in the pipes of the cooling system in a coastal power plant.