Full-Scale Evaluation of the Ammonia-Chlorine Process as a Bromate Control Strategy

摘要

Ozonation of water containing moderate to high levels of bromide (0.1-0.3 mg/L), such asrnCalifornia State Project water, can form bromate at levels that exceed the maximum contaminantrnlevel of 10 μg/L. A proven technology to minimize the formation of bromate is to add acid tornreduce the pH of ozonation. However, in waters with moderate or high alkalinity, the cost ofrnacid and caustic to lower and subsequently raise the pH of the water, respectively, can be higherrnthan the cost of producing ozone. To lower costs, the Metropolitan Water District of SouthernrnCalifornia conducted a demonstration-scale evaluation of the addition of ammonia and thenrnchlorine (ammonia-chlorine process) to form chloramines prior to ozonation as an alternativernbromate control strategy that did not require operation at an acidic pH. Full-scale testing atrnMetropolitan’s Henry J. Mills Water Treatment Plant was initiated to determine if thisrntechnology would be a viable option. Results showed that the ammonia-chlorine processrnconsistently controlled bromate to 5 μg/L or less at ambient pH (7.7) with bromide as high asrn0.30 mg/L.