New insights into bromate removal by UV/sulfite process: Influencing factors, mechanism, and energy efficiency

In recent years, the UV/sulfite process has shown high superiority in removing toxic halogenated organic compounds and oxyanions. Herein, the reduction of bromate (BrO3-) in this process was reinvestigated. The reduction of BrO3- in this process was influenced by some key coexisting species. A significant inhibition on the reduction of BrO3- was observed in the presence of dissolved oxygen (DO). Nevertheless, increasing sulfite dosage could effectively mitigate the negative impact of DO on the reduction of BrO3-. Humic acid (HA) could influence the reduction of BrO3- through the enhancement of hydrated electron (e(aq)(-)) yield or the scavenging of eaq-. It should be noted that the presence of Cl- and HCO3- had an insignificant influence on the reduction of BrO3-. In this process, besides e(aq)(-), sulfite radical (SO3-) also contributed to the reduction of BrO3-, which was evidenced by scavenging experiments and fitting of a kinetic model. Moreover, the energy efficiency of this process for BrO3- removal was found to be enhanced by increasing sulfite dosage, as indicated by calculation of electrical energy per order (EE/O). Meanwhile, this process was proven to be economical for BrO3- removal. This study might provide a new outlook on the UV/sulfite process for real applications.

Automated summary

In recent years, the UV/sulfite process has shown high superiority in removing toxic halogenated organic compounds and oxyanions. This study reinvestigated the reduction of bromate (BrO3-) in this process, finding that it is influenced by key coexisting species such as dissolved oxygen (DO) and humic acid (HA). The study also revealed that besides electron reduction, sulfite radical (SO3-) also contributes to the reduction of BrO3-. Additionally, increasing sulfite dosage enhances the energy efficiency of the process for BrO3- removal.