Kinetic modelling assisted balancing of organic pollutant removal and bromate formation during peroxone treatment of bromide-containing waters.

The peroxone process (O/HO) is reported to be a more effective process than the ozonation process due to an increased rate of generation of hydroxyl radicals (OH) and inhibition of bromate (BrO) formation which is otherwise formed on ozonation of bromide containing waters. However, the trade-off between the HO dosage required for minimization of BrO formation and effective pollutant removal has not been clearly delineated. In this study, employing experimental investigations as well as chemical modelling, we show that the concentration of HO required to achieve maximum pollutant removal may not be the same as that required for minimization of BrO formation. At the HO dosage required to minimize BrO formation (<10 µg/L), only pollutants with high to moderate reactivity towards O and OH are effectively removed. For pollutants with low reactivity towards O/OH, high O (O:DOC>>1 g/g) and high HO dosages (O:HO ∼1 (g/g)) are required for minimizing BrO formation along with effective pollutant removal which may result in a very high residual of HO in the effluent, causing secondary pollution. On balance, we conclude that the peroxone process is not effective for the removal of low reactivity micropollutants if minimization of BrO formation is also required.