A noble chemical treatment called Advanced Reduction Processes (ARP) has been proposed to remove persistent oxidized contaminants from water and wastewater. ARP was developed by combining ultraviolet irradiation with reducing reagent, which produces reactive reducing free radicals that degrade inorganic and organic contaminants such as perchlorate, nitrate, nitrite, perfluorooctanoic acid, 2,3-dichlorophenol, 1,2-dichloroethane, and vinyl chloride. In this study, the effectiveness of ARP for removing bromate, one of by-products of disinfection process, was investigated and also the effects of experimental parameters including initial bromate concentration, reducing agent (sulfite) doses, and pH on the bromate removal kinetics were evaluated. Sulfite activated by ultraviolet light produced by a medium-pressure mercury vapor lamp (UV-M) and a low-pressure mercury vapor lamp (UV-L) showed a complete bromate removal and almost total conversion of bromate ions into bromide ions. All degradation reactions were found to follow a pseudo-first-order rate model and the rate constants (kobs) were characterized. When initial bromate concentration was 500 ppb and the pH was at neutral the kobs by direct photolysis using UV-M and UV-L irradiation was 0.051 (1/min) and 0.017 (1/min), respectively. Increasing sulfite dose increased the bromate removal rate with UV-L irradiation, and it was more remarkable than that by UV-M irradiation. The kobs by UV-L/sulfite ARP was increased over the pH ranged from 4 to 11, whereas kobs by UV-M/sulfite ARP showed the maximum at pH 9. The pH effect on UV-L ARP or UV-M ARP was explained by the effect of pH on the distribution of sulfite species between sulfite and bisulfite or the hydrated electrons concentrations. The optimum conditions of process variables will support development of the process as a practical water treatment method.

Effect of medium-pressure and low-pressure UV irradiation on bromate removal in an Advanced Reduction Process (ARP)

248th National Meeting (2014)

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