Emerging investigators series: prediction of trace organic contaminant abatement with UV/H2O2: development and validation of semi-empirical models for municipal wastewater effluents

Abstract

Recent evaluations of potable reuse treatment trains suggest that the use of UV and UV/H₂O₂ may become increasingly common, particularly in systems employing ozone and/or biofiltration. This study provides a summary of photolysis rate constants and ˙OH rate constants and demonstrates the applicability of semi-empirical relationships predicting ˙OH exposure and trace organic contaminant (TOrC) abatement with UV/H₂O₂ in matrices with low UV transmittance (e.g., <80%). The data are based on bench-scale experiments with 17 target compounds in 10 laboratory-filtered secondary wastewater effluents. As an alternative to ˙OH exposure measurements with probe compounds, three different approaches for considering the impacts of matrix-specific ˙OH scavenging on TOrC abatement are proposed: (1) estimation of R_˙OH,UV (i.e., ˙OH exposure per UV dose); (2) estimation of k_UV/DOC, the pseudo first order rate constant based on the UV/DOC (dissolved organic carbon) ratio; and (3) assessment of TOrC abatement based on differential UV₂₅₄ absorbance or fluorescence. The level of laboratory investment varies with each approach, but there is a tradeoff in the accuracy of the predictions and whether they typically overestimate or underestimate actual TOrC abatement.