Removal of Cyanotoxins in Drinking Water Using Advanced Oxidation Processes

The efficiency of ozone treatment on the removal of three cyanotoxins in simulated Qatar tap water was evaluated. The reactivity of cyanotoxins with ozone followed the order as microcystin-LR (MLR) > cylindrospermopsin (CYN) > anatoxin-a (ANA). Approximately 70% of MLR, CYN and ANA were oxidized with an applied ozone dosage of 0.04 mg/L, 0.085 mg/L and 0.26 mg/L, respectively. Increased ozone dose greatly improved the oxidation efficiency, and a complete removal was achieved for all cyanotoxins. The level of pH affected the removal differently; highest removal rates were obtained at pH 5, pH 10 and pH 7.2 for MLR, ANA and CYN, respectively. There was no obvious effect of hydrogen peroxide addition on ozone treatment efficiency. Based on the calculated pseudo first order rate constants, the estimated ozone doses required for the 99.5% removal of 0.2 mg/L MLR, CYN and ANA were 0.12 mg/L, 0.22 mg/L and 1.3 mg/L, respectively.