Oxidation of microcystin-LR with chlorine and permanganate during drinking water treatment

The oxidation of microcystin-LR (MC-LR) present in natural waters with chlorine and potassium permanganate under real drinking water treatment conditions has been investigated in the present work. The natural waters were spiked with MC-LR, using the typical concentration of 5 μgL⁻¹ found in natural waters. The influence of some operational parameters such as the initial oxidant concentration, pH and temperature and of some drinking water quality parameters such as the NOM and ammonia content has been studied. The initial chlorine concentration and the temperature have a positive effect on MC-LR elimination. However, the pH exerts a negative influence on the MC-LR elimination by chlorine, which indicates that HOCl is the main active oxidant species. High concentrations of NOM and ammonia, which consume chlorine, impede the elimination of MC-LR. During the oxidation with permanganate, the initial permanganate concentration and the temperature have a positive effect on MC-LR removal, while the pH and the ammonia content do not exert any influence on its oxidation. However, high concentrations of NOM reduce the extent of oxidation of MC-LR with permanganate.