Utilities frequently employ a combination of reverse osmosis and advanced oxidation as broad physical and chemical barriers to the passage of contaminants during the potable reuse of municipal wastewater effluents. Disinfection byproducts, formed during the application of disinfectants to control biofouling on the membranes, can pass through reverse osmosis membranes because many are uncharged and have a low molecular weight. While the UV/H2O2 Advanced oxidation process effectively degrades N-nitrosodimethylamine, the destruction of halogenated disinfection byproducts is relatively poor. We determined parameters needed to model the degradation of &gt;20 halogenated DBPs by UV direct photolysis (molar extinction coefficients and quantum yields) and degradation by hydroxyl radical (second order reaction rate constants). The disinfection byproduct classes included trihalomethanes (including iodinated species), haloacetic acids, haloacetonitriles, haloacetamides, haloacetaldehydes, and chloropicin. While these are the most frequently studied of the emerging disinfection byproducts, they represent a minority of total organic halogens. To enable prediction of removal rates when new species are identified, we developed a quantitative structure-activity relationship (QSAR). We validated the model against an additional set of halogenated disinfection byproducts and some halogenated industrial solvents, another class of compounds poorly removed during potable reuse. Application of the combined model predicted that brominated byproducts would be better removed via UV photolysis at typical UV fluence applied at these facilities, but that most species would exhibit &lt;50% removal at these doses. Because recent work suggests that some of the emerging halogenated byproducts may be greater drivers for the toxicity of potable reuse waters than N-nitrosodimethylamine, alternative treatments to the UV/H2O2 advanced oxidation process should be evaluated.

Disinfection byproducts as challenge targets for AOP treatment during potable reuse

253rd National Meeting (2017)

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