AWWA JAW10798

The yield of chlorine dioxide (ClO2)is influenced by chemical conditions, such as initial chlorine concentration and alkalinity, and by reactor design. This article describes the design and operation of ClO2-generating systems used by the Brussels' Intercommunal Waterboard (Compagnie Intercommunale Bruxelloise des Eaux, CIBE) in Brussels, Belgium. The treatment scheme used at the Waterboard involves mixing treated surface water with groundwater. At the entrance of the transport aqueducts, chloramines generated n-site are added for disinfection. This technique consists of prechlorination for 2 to 5 minutes followed by the injection of ammonia. Additional treatment processes include a supplementary and final injection of ClO2, coagulation, flocculation, adsorption, settling and filtration, and ozonation. Improved reactor designs have increased ClO2 yields from 65 to 80 percent to greater than 95 percent of the theoretical yield. Includes 6 references, figures.