Effects of reductive inorganics and NOM on the formation of chlorite in the chlorine dioxide disinfection of drinking water

Chlorine dioxide (ClO 2 ) disinfection usually does not produce halogenated disinfection by-products, but the formation of the inorganic by-product chlorite (ClO 2 – ) is a serious consideration. In this study, the ClO 2 – formation rule in the ClO 2 disinfection of drinking water was investigated in the presence of three representative reductive inorganics and four natural organic matters (NOMs), respectively. Fe 2+ and S 2– mainly reduced ClO 2 to ClO 2 – at low concentrations. When ClO 2 was consumed, the ClO 2 – would be further reduced by Fe 2+ and S 2– , leading to the decrease of ClO 2 – . The reaction efficiency of Mn 2+ with ClO 2 was lower than that of Fe 2+ and S 2– . It might be the case that MnO 2 generated by the reaction between Mn 2+ and ClO 2 had adsorption and catalytic oxidation on Mn 2+ . However, Mn 2+ would not reduce ClO 2 – . Among the four NOMs, humic acid and fulvic acid reacted with ClO 2 actively, followed by bovine serum albumin, while sodium alginate had almost no reaction with ClO 2 . The maximum ClO 2 – yields of reductive inorganics (70%) was higher than that of NOM (around 60%). The lower the concentration of reductive substances, the more ClO 2 – could be produced by per unit concentration of reductive substances. The results of the actual water samples showed that both reductive inorganics and NOM played an important role in the formation of ClO 2 – in disinfection.