Bromate formation in bromide-containing waters irradiated by gamma rays

The formation of bromate, a classified potential carcinogen, is of great concern when disinfection processes are used for treating high-bromide drinking waters. Bromide-containing aqueous solutions with various additives were irradiated by ⁶⁰Co γ source. With a 2.0 kGy irradiation of N₂O-saturated solutions at initial bromide concentrations of 180.2 μgl^-1, 416.9 μgl^-1, 663.1γgl^-1 and 823.9 μgl^-1. 79.5%, 84.0%, 87.3% and 88.3% of bromide ions were transformed to bromate, respectively. Addomg CO₃²-/HCO₃^- or NO₃^- ions into N₂O- saturated bromide solutions, the amount of bromate ions formed decreased with increasing concentrations of the additives. On the other hand, the bromate concentration was all below the detection limit of 1 μgl^-1 when- ever N₂O was not added to quench e_aq^- and ·H. The results indicated that γ-rays irradiation could be used as a disinfection process, instead of ozonation, to comply with upcoming more stringent regulations, especially in waters containing high concentrations of bromide. (authors)