Study On Influential Factors And Inhibition Mechanisms Of Byproducts Formation During Ozonation Of Bromide-containing Water

As the Advanced Oxidation Process(AOP) that can improve drinking water quality, ozonation has applied in drinking water treatment all over the world. However, bromate(Br O3-), which forms during ozonation in bromide-containing water, is a potential carcinogen and nephrotoxic compound to humans. It is regarded as the 2B carcinogen by the International Agency for the Research on Cancer(IARC). Simulation experiments in deionized water were conducted to investigate the formation of ozonation by-products during nano-Ti O2/O3 and nano-Ti O2/UV/O3 processes. In the meanwhile, the effects of the main parameters on Br O3- formation in O3, nano-Ti O2/O3, and nano-Ti O2/UV/O3 processes have been observed. Finally, mechanisms for Br O3- formation in nano-Ti O2/O3 and nano-Ti O2/UV/O3 processes have been proposed. The following major conclusions were drawn from this study.The inhibition efficiency of Br O3- formation was enhanced in the presence of Cl-, SO42-and NO2- under the condition of the same ozone dosage and reaction time, but was weakened in the presence of HCO3-.Nano-Ti O2/O3 process was considerably more effective to inhibit Br O3- formation than O3 process. It was more effective to inhibit Br O3- formation after 60 min under UV irradiation. The effect of initial bromide concentration on Br O3- control had no obvious regularity. The increase of nano-Ti O2 dosage could significantly control Br O3- formation. As the concentrations of inorganic anions in water increased, the inhibition efficiency of Clincreased at first and then decreased, while the inhibition efficiencies of SO42- and NO2-decreased. The inhibition efficiency of Br O3- formation was weakened in the presence of HCO3-. Nano-Ti O2/O3 process could be less effective for the HA removal without bearing the risk of formaldehyde formation in drinking water treatment.Nano-Ti O2/UV/O3 process was considerably more effective to inhibit Br O3- formation than O3, nano-Ti O2/O3, and UV/O3 processes after 60 min. In nano-Ti O2/UV/O3 process, UV254 nm irradiation was more effective to inhibit Br O3- formation than UV185 nm irradiation. There was no Br O3- observed at lower p H after 50 min. Br O3- formation was seemingly unaffected by Cl-. High concentrations of Br O3- in finished water were observed by adding HCO3-. Br O3- concentrations in finished water were lower than 10 μg/L in water with the HA concentration of 10 mg/L. In the meantime, a nano-Ti O2/UV/O3 process could be useful for the HA removal without bearing the risk of formaldehyde formation.In nano-TiO2/UV/O3 process, the concentration of BrO3 was rapidly decreased after 5min, though Br O3- formation was enhanced within 5 min. There was no Br O3- in finishedwater after 60 min.