Impact of H2O2and (bi)carbonate alkalinity on ammonia's inhibition of bromate formation

Ammonia can be used to minimize bromate concentrations by blocking two of three potential bromate formation pathways. It was theorized that (bi)carbonate alkalinity in the presence of ammonia would inhibit bromate formation since the pathway that ammonia does not block requires hydroxyl radicals (OH center dot), and (bi)carbonate alkalinity is an OH center dot scavenger. Experiments where (bi)carbonate alkalinity was increased from 50 to 119 mg/L (as CaCO3) in the presence of excess ammonia resulted in up to 50% reduction in bromate formation, providing evidence in support of the theory. While OH, is scavenged by (bi)carbonate alkalinity, it is promoted by hydrogen peroxide (H2O2). When ozone reacts with natural organic matter the H2O2 that is formed may therefore render ammonia less effective. Experiments conducted in this study demonstrated this principle. (c) 2006 Elsevier Ltd. All rights reserved.