Numerical kinetic models for bromide oxidation to bromine and bromate

Numerical models for bromine and bromate formation were developed by linking kinetic models for ozone consumption with bromide oxidation reactions. The first numerical model (BasicBr) predicted ozone consumption 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 (kObs) for this reaction was calculated from batch ozonation experimental data. A second numerical model (HSBBR) predicted ozone consumption and HO radical formation with a set of theoretical reactions and did not require input of a pseudo first-order rate constant. Both oxidant models were combined with a set of reactions that account for direct molecular ozone and indirect HO radical oxidation mechanisms. The HSBBR and BasicBr models simulated bromine and bromate concentrations obtained from batch experiments 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 presence of NOM during ozonation was evaluated and it was concluded that further understanding of NOM reactions with oxy-bromine species and HO radicals was necessary in order to understand and evaluate bromate formation in natural waters.