DISINFECTION OF EFFLUENTS BY COMBINATIONS OF CHLORINE DIOXIDE AND CHLORINE

The behaviour of both chlorine dioxide and chlorine, either as an indi vidual or as combined disinfectants were studied on effluents from act ivated sludge. The results of the disinfection efficiency, residual di sinfectants, and their by-products, obtained by treating the same effl uents at the same day with identical dosing Sequence of chlorine dioxi de and chlorine, alone and in a combined dosing, were compared after p eriods of the same contact. In most cases, it seems that each disinfec tant maintains its individual capabilities when used in a combined man ner. The combination produced a relatively stable high residual of bot h disinfectants. The important finding is the fact that the combinatio ns of chlorine dioxide and chlorine decreased the concentration of the undesirable chlorite ion and increased the concentration of the newly formed chlorine dioxide. A greater advantage is obtained by using chl orine dioxide prior to chlorine. Therefore, combined disinfection in t his sequence is recommended.