AWWA ACE93129

A pilot-scale study of the ozonation of surface waters containing moderate levels of bromide (Br-) was conducted in order to collect kinetic parameters suitable for modeling the production of bromate. Operating in a pre-ozonation mode, the two surface waters were dosed under conditions designed to theoretically provide greater than 0.5 log 10 inactivation levels for Giardia. Key results from the experimental study and kinetic analysis of bromate formation in these two waters are: bromate production results from rapid free radical processes. The slower, recursive reactions involving the direct oxidation of bromide and hypobromite by ozone are significant; ozone residual is the controlling factor in the rate and extent of bromate formation; hypobromite and hypobromous acid are formed primarily as minor byproducts of oxybromine radical decay, and do not play a significant role as precursors at pHs less than 9.0; naturally occurring organic matter plays a complex role in production and consumption of both oxygen radicals and possibly oxybromine radicals; and gas-liquid contactor hydrodynamics play a critical role in bromate formation, influencing mass transfer rates, peak ozone residuals, spatial-temporal concentration gradients, and liquid backmixing phenomena.