Evaluation of MC-LR Removal by Sodium Hypochlorite Disinfection as Best Available Technology (BAT) for Algal Toxin Removal

Harmful cyanobacteria produce various toxic substances, among which microcystin is the most commonly detected toxin in water resources, with microcystin-LR(MC-LR) known to be the most toxic. For the removal of microcystin, sodium hypochlorite(NaOCl) disinfection is recognized as an effective best available technology(BAT) in water treatment facilities for MC-LR removal, within limits that minimize the formation of disinfection by-products. However, chlorine disinfection of microcystin is affected by various factors, including temperature and pH, with environmental factors such as the presence of organic matter in raw water potentially influencing the efficiency of microcystin removal. In this study, raw water was collected from the Nakdong River, and Intracellular Organic Matter(IOM) was extracted from algal cells. NaOCl was then added to both the IOM raw water and DI water to assess the chlorine disinfection rate of MC-LR removal and to analyze the pseudo-first-order reaction kinetics, evaluating the impact of organic matter in raw water on MC-LR chlorination. The results showed that the MC-LR removal rate in IOM by chlorine disinfection was a maximum of 17%, while the MC-LR removal in deionized water reached up to 99%. The pseudo-first-order reaction rate constants were 3.99×10-5s-1 and 9.11×10-4s-1 for IOM and deionized water, respectively, indicating that MC-LR removal in IOM was slower and had a lower removal rate compared to that in deionized water. This study demonstrates that chlorine disinfection is suitable as the BAT for algal toxin removal and highlights the need to reduce the amount of organic matter through pre-treatment before chlorine disinfection.