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

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 semiempirical 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 ROH,UV (i.e., OH exposure per UV dose); (2) estimation of kUV/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.