Chlorite removal with granular activated carbon

Chlorite (ClO2-) is the dominant degradation by-product coming from chlorine dioxide reactions. Compliance to the maximum concentration of 200 μg/l, established by new Italian regulations for drinking water (D. Lgs. 31/2001), can be accomplished by reduction of chlorine dioxide dosage during water treatment or by chlorite removal. In this work granular activated carbon (GAC) as a technology for chlorite removal was investigated; particularly, the interference between chlorite and organic matter removal on GAC active sites and the applicability of a “chemical regeneration” process in order to improve GAC efficiency for organic matter and chlorite removal were studied. Different batch and column tests were performed, both on distilled and surface water spiked with chlorite; both on virgin, exhausted and thermally regenerated carbon; and on exhausted GAC after chemical regeneration by acid, basic and basic–acid solutions. The results demonstrate that GAC can be an efficient method for chlorite removal.