Evaluation of chlorite and chlorate removal by activated carbon in a pilot scale drinking water treatment plant.

Chlorine dioxide (ClO2) applied in the disinfection of drinking water can produce chlorite (ClO2-) and chlorate (ClO3-). It is noted that the ClO2- and ClO3- formation is about 68% and 9% of the ClO2 consumed.1,2 The World Health Organization recommends a guideline value (GV) of 700 µg L-1 for both of these compounds in drinking water, since they can cause oxidative damage to human red blood cells.3 Specific treatment processes can be applied to control the production of ClO2-, while no treatment is known for ClO3- removal. The ClO2- can be removed by adding reduced-sulphur compounds such as sulphur dioxide and sodium sulphite, or by adding iron-based salts, such as ferrous chloride and ferrous sulphate, or applying powdered (PAC) or granular (GAC) activated carbon.