Evaluation of chlorite and chlorate propagation in a drinking water distribution system

Disinfection is applied in drinking water treatment plants (DWTPs) to ensure water quality and to avoid bacterial contamination in drinking water distribution systems (DWDSs). However, disinfectant concentration in DWDSs decreases with time, while disinfection by-product (DBP) formation increases; this is due to chemical reactions of the disinfectant with dissolved and particulate matter in the water, biofilm and pipe wall material.1-4 If chlorine dioxide (ClO2) is used as a disinfectant, chlorite (ClO2-) and chlorate (ClO3-) can be produced as DBPs. Therefore, it is important to evaluate spatial and temporal variation in residual chlorine, ClO2- and ClO3- within the DWDS. In fact, the World Health Organization (WHO) recommends a free residual chlorine concentration of 0.2 mg L-1 in the DWDS;5 moreover, since ClO2- and ClO3- can cause oxidative damage to red blood human cells, each compound should not exceed the WHO guideline value (GV) of 700 µg L-1 in drinking water.5