Sources, occurrence, and control of chlorine dioxide by-product residuals in drinking water

BACKGROUND For many years, chlorine dioxide (ClO2) has been used successfully as either a substitute for or an adjunct to chlorine during the treatment of drinking water. Although ClO2 is an excellent oxidant, disinfectant, and treatment for tastes and odors, its use in recent years has been restricted because potential health effects are associated with both the oxidant itself and its by-products, chlorate ion (ClO3-) and chlorite ion (ClO2-). Regulations have proposed the ClO2 maximum residual disinfectant level (MRDL) as 0.8 mg/L, and the maximum contaminant level for chlorite as 1.0 mg/L. No regulations have been proposed for chlorate.