Comprehensive Assessment of Reactive Bromine Species in Advanced Oxidation Processes: Differential Roles in Micropollutant Abatement in Bromide-Containing Water.

Reactive bromine species (RBS) are gaining increasing attention in natural and engineered aqueous systems containing bromide ions (Br - ). However, their roles in the degradation of structurally diverse micropollutants by advanced oxidation processes (AOPs) were not differentiated. In this study, the second-order rate constants ( k ) of Br • , Br 2 •- , BrO • , and ClBr •- were collected and evaluated. Br • is the most reactive RBS toward 21 examined micropollutants with k values of 10 8 -10 10 M -1 s -1 . Br 2 •- , ClBr •- , and BrO • are selective for electron-rich micropollutants with k values of 10 6 -10 8 M -1 s -1 . The specific roles of RBS in aqueous micropollutant degradation in AOPs were revealed by using simplified models via sensitivity analysis. Generally, RBS play minimal roles in the UV/H 2 O 2 process but are significant in the UV/peroxydisulfate (PDS) and UV/chlorine processes in the presence of trace Br - . In UV/PDS with ≥1 μM Br - , Br • emerges as the major RBS for removing electron-rich micropollutants. In UV/chlorine, BrO • contributes to the degradation of specific electron-rich micropollutants with removal percentages of ≥20% at 1 μM Br - , while the contributions of BrO • and Br • are comparable to those of reactive chlorine species as Br - concentration increases to several μM. In all AOPs, Br 2 •- and ClBr •- play minor roles at 1-10 μM Br - . Water matrix components such as HCO 3 - , Cl - , and natural organic matter (NOM) significantly inhibit Br • , while BrO • is less affected, only slightly scavenged by NOM with a k value of 2.1 (mg C /L) -1 s -1 . This study sheds light on the differential roles of multiple RBS in micropollutant abatement by AOPs in Br - -containing water.