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•, Br2•–, BrO•, and ClBr•– were collected and evaluated. Br• is the most reactive RBS toward 21 examined micropollutants with k values of 108–1010 M–1 s–1. Br2•–, ClBr•–, and BrO• are selective for electron-rich micropollutants with k values of 106–108 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/H2O2 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, Br2•– and ClBr•– play minor roles at 1–10 μM Br–. Water matrix components such as HCO3–, 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 (mgC/L)−1 s–1. This study sheds light on the differential roles of multiple RBS in micropollutant abatement by AOPs in Br–-containing water.