evaluation of pH and ammonia for controlling bromate during Cryptosporidium disinfection

This research evaluated pH suppression and/or ammonia addition for controlling bromate formation under disinfection conditions for Cryptosporidium. Lowering pH before ozonation substantially reduced bromate formation over a range of inactivation levels and bromide concentrations in two different source waters. Although pH suppression was an effective bromate control strategy, the cost of adjusting pH-in moderate- and high-alkalinity waters and for high inactivation levels-may be from two to nine times greater than the cost of generating the ozone. The efficacy of ammonia was highly dependent on the source water. Adding ammonia was an effective bromate control strategy for one of the source waters tested; however, adding aqueous ammonia increased pH and exerted an additional ozone demand, thus lowering the disinfection credit.