Influence of pre-ozonation of DOM on micropollutant abatement by UV-based advanced oxidation processes

Dissolved organic matter (DOM), ubiquitously co-present in micropollutant-impaired water, significantly decreases micropollutant removal in UV-based AOPs through consuming radicals and filtering UV light. In this study, pre-ozonation was proposed to alleviate the negative effects of DOM on UV-based AOPs. After ozone treatment of DOM-containing water at ozone dosages of 0.1-1 mg O₃/mg DOC, the degradation rate of benzoic acid (BA) in UV/H₂O₂ process increased by 7-34% mainly due to the enhanced transmission of UV light. The degradation rate of BA in UV/S₂O₈^2- process varied from -11% to 25% at ozone dosages of 0.1-1 mg O₃/mg DOC because of the increased photolysis rate of S₂O₈^2- and the altered reactivity of DOM towards SO₄^-. Pre-ozonation of DOM at ozone dosage of 1 mg O₃/mg DOC enhanced the oxidation rate of BA in UV/chlorine process by 35% due to the increased rate of chlorine photolysis and the decreased reactivity of DOM towards Cl. The influence of pre-ozonation on the formation potential of disinfection by-products (DBPs) depends on the kind of AOPs and the species of DBPs. The energy cost analysis suggests that pre-ozonation of DOM is an economic process for enhancing pollutant abatement by UV-based AOPs.