Bromate in drinking water: Occurrence and removal by ultraviolet/sulfite advanced reduction processes

Bromate, a potential carcinogen, is a major disinfection byproduct formed during the ozonation of bromidecontaining water; hence, the suppression of bromate in ozonated drinking water is imperative for protecting human health. Owing to the elevated levels of bromide ions transported to the source water through seawater intrusion and anthropogenic inputs, bromate concentration in drinking water is increasing in some regions of the world. Moreover, the excessive application of ozone for treating this water has resulted in an elevated risk of bromate in drinking water. Therefore, this review presents the current status of the occurrence of bromate in drinking water, followed by presenting the development of recent technologies for bromate reduction-specifically focusing on the effectiveness of ultraviolet (UV)/sulfite advanced reduction processes (ARPs). The application of UV/sulfite ARPs as a post-ozonation treatment is of increasing interest to researchers because these have shown superior bromate removal efficiencies as compared to previous methods. The highly reactive free radicals (e.g., hydrated electrons and sulfite radicals) obtained from UV/sulfite ARPs substantially enhanced bromate reduction efficiency to 60 %-100 %, with a reduction rate of 3.0 x 10- 2-2.5 x 10-1 min- 1. An increase in the sulfite dosage and pH showed positive effects on the performance of UV/sulfite ARPs for bromate reduction. However, other factors including dissolved oxygen, inorganic anions, and organic anions potentially impaired the performance of UV/sulfite ARPs due to their competition with bromate for reactive radicals. Finally, this review also discusses the limitations of UV/sulfite ARPs.