Organic Contaminant Abatement in Reclaimed Water by UV/H_2O_2 and a Combined Process Consisting of O_3/H_2O_2 Followed by UV/H_2O_2: Prediction of Abatement Efficiency, Energy Consumption, and Byproduct Formation

摘要

UV/H_2O_2 processes can be applied to improve the quality of effluents from municipal wastewater treatment plants by attenuating trace organic contaminants (micropollutants). This study presents a kinetic model based on UV photolysis parameters, including UV absorption rate and quantum yield, and hydroxyl radical (·OH) oxidation parameters, including second-order rate constants for ·OH reactions and steady-state ·OH concentrations, that can be used to predict micropollutant abatement in wastewater. The UV/H_2O_2 kinetic model successfully predicted the abatement efficiencies of 16 target micropollutants in bench-scale UV and UV/H_2O_2 experiments in 10 secondary wastewater effluents. The model was then used to calculate the electric energies required to achieve specific levels of micropollutant abatement in several advanced wastewater treatment scenarios using various combinations of ozone, UV, and H_2O_2. UV/H_2O_2 is more energy-intensive than ozonation for abatement of most micropollutants. Nevertheless, UV/H_2O_2 is not limited by the formation of N-nitrosodimethylamine (NDMA) and bromate whereas ozonation may produce significant concentrations of these oxidation byproducts, as observed in some of the tested wastewater effluents. The combined process of O_3/H_2O_2 followed by UV/H_2O_2, which may be warranted in some potable reuse applications, can achieve superior micropollutant abatement with reduced energy consumption compared to UV/H_2O_2 and reduced oxidation byproduct formation (i.e., NDMA and/or bromate) compared to conventional ozonation.