AWWA WQTC56998

Ozone is becoming an attractive alternative chemical for drinking water disinfection due to the resistance of waterborne pathogens such as Cryptosporidium parvum oocysts to inactivation by weaker oxidants such as free and combined chlorine. However, the relatively high ozone doses required for inactivation can lead to the formation of relatively high levels of bromate, a compound of public health concern, in waters containing bromide ion. It has therefore become necessary to provide adequate pathogen inactivation while minimizing the amount of bromate formed during water treatment. This paper discusses an approach to achieve such optimization by characterizing the kinetics of bromate formation by performing a limited number of laboratory-scale experiments, and developing a mathematical tool based on this kinetic information for predicting bromate formation. Of particular interest in this study is the role of pH in bromate formation. Experiments have been performed with Ottawa River Water (ORW) (pH=6.1, TIC=2.9 mg/l, TOC=2.2x10-4 mg/l, [Br-]=20 ug/l) at different pH levels (pH 6.5, 7.5 and 8.4) after increasing the concentration of bromide ion to 600 ug/L in order to determine ozone decomposition and subsequent bromate formation profiles for this natural water. These experimental results are being used to calibrate the mechanistic model currently under development. Includes 57 references, table, figures.