A low concentration (0.8%) sodium hypochlorite disinfection facility, introduced to reduce the risk of chlorine gas and improve operational convenience, has become popular with small water purification plants. However, it has not been possible to apply this facility to large-scale water purification plants because disinfection by-products exceed water quality standards or excessive investment costs.
In order to solve these problems, this study designed and manufactured high concentration sodium hypochlorite generator and applied it to large-scale water treatment plants.
The membrane cell in the electrolytic module used for the production of high concentration of hypochlorite. When the temperature of the high concentration sodium hypochlorite was maintained within 25℃, the concentration could be secured up to 27 days within 10% deviation of 12%.
Analysis of disinfection by-products of hypochlorite produced in high concentration sodium hypochlorite generator showed that chlorate reduced by more than 50% compared to low concentration sodium hypochlorite, and also the amount of bromate significantly reduced by using rock salt.
As a result, it was possible to operate the disinfection process of sodium hypochlorite safe and stable in a large water purification plant. The chlorate concentration of the produced sodium hypochlorite was affected by the temperature after production. As the high concentration sodium hypochlorite was produced and stored at 18℃, the quality of the sodium chloride can be secured up to 13 days when kept at 20℃ in the storage tank.
The change of residual chlorine was less than that of using liquefied chlorine and more stable to residual chlorine equalize.
Based on the above results, the high concentration sodium hypochlorite generator can apply to large-scale water purification plants by reducing the generation of disinfection by-products as well as increasing the concentration of sodium hypochlorite.
This study will remove the risk of chlorine gas leaks that can occur due to the location of large-scale water purification plants in the city center, increase the operational convenience of water purification plant operators operating high-pressure gas, reduce the generation of disinfection by-products.