To meet the increasing drinking water demand under drought conditions, membrane treatment coupled with advanced oxidation processes (AOP) has been used to transform treated wastewater to high quality reclaimed water. Because on-site chloramination is usually applied to reduce the biofouling on the membranes, an array of disinfection byproducts (DBP) may be formed prior to membrane treatment through the reaction between chloramines and organic precursors within the treated wastewater. Therefore, the water quality of reclaimed water is dependent on the efficacy of DBP removal by membrane (e.g., reverse osmosis, RO) and AOP processes (e.g., UV/ H2O2). To predict the degradation of over 600 DBPs identified in drinking water by UV/ H2O2, this study aimed to develop a quantitative structure-reactivity relationship (QSAR) model. We determined the degradation rate of 36 halogenated DBPs, including chloro-, bromo-, and iodo-trihalomethanes, haloacetonitriles, haloacetamides, halonitromethanes, haloacetic acids and haloacetaldehydes, under low-pressure UV (LPUV) light. Separately, the reaction rates between hydroxyl radical and DBPs were also determined using gamma radiolysis as a source of hydroxyl radical. During direct LPUV photolysis, the quantum yields of the 36 DBPs were similar, ranging from 0.11 to 0.59; however, the fluence-based first order rate constant varied from 1.3 × 10-5 to 2.6 × 10-3 mJ/cm2 and was linearly correlated with the molar extinction coefficient of DBP (R2=0.86). The second-order rate constants between hydroxyl radical and DBPs spanned three orders of magnitude, ranging from 2 ×106 M-1s-1 for trichloroacetamide to 8.2 × 109 M-1s-1 for bromodiiodomethane. Overall, DBPs with bromo- and/or iodo- substituents are more rapidly degraded by UV/H2O2 treatment than the corresponding chloro-species. Ongoing work will pair fundamental molecular parameters with experimentally determined reaction rate constants to develop a QSAR model, providing a predictive tool for halogenated DBP removal in AOP processes to achieve high quality reclaimed water.

Development of a quantitative structure-activity relationship model to predict the degradation of halogenated disinfection byproducts by UV-hydrogen peroxide (UV/ H2O2) advanced oxidation treatment

251st National Meeting (2016)

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