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)-O-center dot rate constants and demonstrates the applicability of semi-empirical relationships predicting (OH)-O-center dot 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)-O-center dot exposure measurements with probe compounds, three different approaches for considering the impacts of matrix-specific (OH)-O-center dot scavenging on TOrC abatement are proposed: (1) estimation of R-center dot OH,(UV) (i.e., (OH)-O-center dot 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.