Effect of UV/Chlorine Oxidation on Disinfection By product Formation from Diverse Model Compounds

Disinfection byproduct (DBP) formation is a potential concern for the UV/chlorine advanced oxidation process (AOP) in water treatment. In this study, 11 model compounds were selected as natural organic matter (NOM) surrogates, including seven active DBP precursors and four poor precursors. The effect of UV/chlorine on their DBP formation in the UV reactor and during 24 h postchlorination was investigated in comparison to dark chlorination. DBPs evaluated included adsorbable organic halides (AOX), trihalomethanes, haloacetic acids (HAAs), haloacetaldehydes (HALs), trichloronitromethane (TCNM), and dichloroacetonitrile (DCAN). UV/chlorine AOP was conducted at a typical UV dose adopted in drinking water treatment and at both pH 6.0 and 7.8 with postchlorination pH kept at pH 7.8. For most of the active DBP precursors, UV/chlorine either decreased their AOX formation potential (FP) and DBPFP by <25% or showed an insignificant impact. Three poor DBP precursors were activated by UV/chlorine oxidation, especially at pH 6.0, with a significant increase of AOXFP and DBPFP percentage-wise, but the absolute increase was low (less than 186 mu g-Cl/mg-C and 50 mu g DBP/mg-C). UV/chlorine converted some chloroform precursors to HAA or HAL precusors. For N-containing precursors, UV/chlorine increased TCNM formation and decreased DCAN formation, especially at pH 6.