AWWA JAW59040

A demonstration-scale study was undertaken to evaluate pH suppression and ammonia addition to control bromate formation under disinfection conditions for Cryptosporidium. Specific research objectives included determining the effects of seasonal bromide changes on bromate formation over a range of pH values and assessing control of bromate over a variety of ammonia doses, at varying disinfection levels, and at different pH values. Tests were conducted on two sample waters with varying levels of alkalinity, bromide, and total organic carbon. Although pH control did limit bromate formation, the strategy was found to be relatively expensive because of the large chemical dosages required. As a bromate control method, ammonia proved source water-specific, with a higher rate of success in high-alkalinity waters than in those with lower alkalinity. Furthermore, ammonia addition must be carefully balanced with the need to provide secondary disinfection with chlorine or chloramines. Many water suppliers in the southwestern United States rely on the source waters tested in this work or are using water with moderate-to-high bromide levels. This research offers direction, practical guidance, and cost analyses for utilities that are considering using ozone or changing their existing ozone practice. Includes 37 references, tables, figures.