The reduction of bromate by granular activated carbon

The removal of bromate, an inorganic disinfection by-product, by granular activated carbon (GAC) was investigated in this study. Bromate ion removal from water was observed in the presence of virgin and acid-washed outgassed (AWOG) GAC. In a GAC filter with distilled-deionized water, bromate breakthrough occurred slowly whereas bromate breakthrough occurred very quickly in natural water due to the presence of natural organic matter (NOM) and other anions. NOM adsorption decreased bromate reduction, presumably by blocking bromate reduction sites. The use of a biologically active carbon (BAC) filter with ozonated water, as a pretreatment step to remove NOM, only slightly improved bromate reduction in the subsequent fresh GAC filter. Kinetic studies showed that the presence of chloride, sulfate, bromide, and nitrate causes a decrease in the kinetics of bromate reduction by GAC. These anions may occupy ion exchange sites on the carbon, reducing the rate at which bromate can access the reduction sites. However, when the anions were released from the carbon, the bromate reduction rate increased.