Reduction of bromate in a BAC filter

Abstract

Water treatment plants already using ozone and GAC filters can readily implement this method of removing bromate.Bromate removal was observed during biologically active carbon (BAC) filtration. Microorganisms in the BAC reduced bromate to bromide, although the formation of other intermediate species is possible. The effects of dissolved oxygen (DO) concentration, nitrate concentration, and empty bed contact time (EBCT) on microbial bromate reduction were examined. Oxygen and nitrate, common microbial electron acceptors, hindered bromate reduction. For example, at an influent DO concentration of 2 mg/L in a BAC filter with a 25‐min EBCT, bromate was reduced by 86 percent at an influent nitrate concentration of 0.2 mg/L, whereas it was reduced by 76 percent at an influent nitrate concentration of 5.1 mg/L. In general, lengthening the EBCT increased bromate removal. Biological bromate removal in a conventional ozone–granular activated carbon plant was deemed possible if the DO concentration in the BAC filter is controlled.