NUMERICAL KINETIC-MODELS FOR BROMIDE OXIDATION TO BROMINE AND BROMATE

Numerical models for bromine and bromate formation were developed by l inking kinetic models for ozone consumption with bromide oxidation rea ctions. The first numerical model (BasicBr) predicted ozone consumptio n and hydroxyl (HO) radical formation with pseudo first-order reaction assuming an HO radical yield of 0.5 mol HO radicals formed per mol of ozone consumed. A pseudo first-order rate constant (k(Obs)) for this reaction was calculated from batch ozonation experimental data. A seco nd numerical model (HSBBR) predicted ozone consumption and HO radical formation with a set of theoretical reactions and did not require inpu t of a pseudo first-order rate constant. Both oxidant models were comb ined with a set of reactions that account for direct molecular ozone a nd indirect HO radical oxidation mechanisms. The HSBBR and BasicBr mod els simulated bromine and bromate concentrations obtained from batch e xperiments in natural organic matter free (NOM-free) waters containing bromide. Analysis with the HSBBR model concluded that the BrO radical would be an important intermediate specie in bromate formation. The p resence of NOM during ozonation was evaluated and it was concluded tha t further understanding of NOM reactions with oxy-bromine species and HO radicals was necessary in order to understand and evaluate bromate Formation ic natural waters. (C) 1998 Elsevier Science Ltd. All rights reserved.