CHLORINE-OZONE INTERACTIONS - FORMATION OF CHLORATE

The chlorate ion is one of the contaminants being considered for regul ation in drinking water under the disinfection by-product rule. Ln add ition to its presence in eater as a result of chlorine dioxide use, ch lorate may be Formed during intermediate ozonation if residual chlorin e is present. The majority of chlorate forms through a free radical pa thway in natural source waters as opposed to by both molecular ozone a nd free radical pathways in low-DOG waters. The monitoring of OH radic als using p-chlorobenzoic acid indicated that the formation of chlorat e is proportional to On radical generation. The increase in pH favored chlorate formation and the presence of alkalinity enhanced chlorate f ormation due to secondary reactions between carbonate radicals and chl orine species. The addition of ammonia and peroxide before ozonation r educed chlorate formation whereas the simultaneous addition of peroxid e during ozonation enhanced chlorate formation. Copyright (C) 1996 Els evier Science Ltd