Bromide-mediated enhancement of far-UVC/peracetic acid process for selective micropollutant abatement

Far‑ultraviolet 222 nm (UV 222 ) effectively activates oxidants to degrade organic micropollutants (OMPs) in advanced oxidation processes (AOPs), but its synergy and ecotoxicity with bromide (Br − ) are unclear. This study investigates the synergy of peracetic acid (PAA) and Br − by UV 222 (UV 222 -PB) for OMPs degradation. The system’s fluence-based rate constant for model pollutants (0.0159 cm 2 ·mJ −1 ) is 3.01 and 15.74 times that of UV 254 -PB and UV 365 -PB. Radical and theoretical analyses show that far‑ultraviolet strengthens the interaction between PAA and Br − , prolongs radical chains, and boosts organic radicals and reactive bromine species, dominating electron‑rich OMPs oxidation. Correlations of ln( k obs ) with vertical ionization potential and highest occupied molecular orbital energy for 10 OMPs confirm selective oxidation. UV 222 -PB performs robustly in various water matrices and shows low ecotoxicity in assays such as seed germination and zebrafish embryo. Life cycle assessment confirms its sustainability. These findings offer insights and guidance for UV 222 -based AOPs in brominated water treatment.