Amino acids (AAs) have been identified as precursors to disinfection by‐products—some more cytotoxic than the currently regulated disinfection by‐products. This study measured occurrences and removals of AAs, amino sugars, and bulk organic matter surrogates (dissolved organic carbon [DOC], dissolved organic nitrogen [DON]) in raw water and filter effluents of 16 full‐scale water treatment plants influenced by algal activity or wastewater discharge. In raw waters, the average concentration of free AAs—those not bound in larger molecules—was very low, 0.69 μg/L N (< 0.5% of the DON). The average concentration of total AAs—those bound and unbound—was 41.1 μg/L N (15% of the DON). The most dominant (on a molar basis) AA species detected were serine, alanine, and glycine. Water treatment removed, on average, 30, 30, 25, and 65% of DOC, DON, free AAs, and total AAs, respectively. This study was the first large‐scale occurrence survey of free and total AAs in United States drinking waters.

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The application of UV disinfection in water treatment is increasing due to both its effectiveness against protozoan pathogens, and the perception that its lack of chemical inputs would minimize disinfection byproduct formation. However, previous research has indicated that treatment of nitrate-containing drinking waters with polychromatic medium pressure (MP), but not monochromatic (254 nm) low pressure (LP), UV lamps followed by chlorination could promote chloropicrin formation. To better understand this phenomenon, conditions promoting the formation of the full suite of chlorinated halonitromethanes and haloacetonitriles were studied. MP UV/postchlorination of authentic filter effluent waters increased chloropicrin formation up to an order of magnitude above the 0.19 μg/L median level in the U.S. EPA's Information Collection Rule database, even at disinfection-level fluences (<300 mJ/cm(2)) and nitrate/nitrite concentrations (1.0 mg/L-N) relevant to drinking waters. Formation was up to 2.5 times higher for postchlorination than for postchloramination. Experiments indicated that the nitrating agent, NO(2)(•), generated during nitrate photolysis, was primarily responsible for halonitromethane promotion. LP UV treatment up to 1500 mJ/cm(2) did not enhance halonitromethane formation. Although MP UV/postchloramination enhanced dichloroacetonitrile formation with Sigma-Aldrich humic acid, formation was not significant in field waters. Prechlorination/MP UV nearly doubled chloropicrin formation compared to MP UV/postchlorination, but effects on haloacetonitrile formation were not significant.

Increased contributions from wastewater discharges and algal activity in drinking water supplies can lead to elevated levels of dissolved organic nitrogen (DON), which can increase the likelihood for the formation of emerging nitrogenous disinfection by-products (N-DBPs) of health concern. Dissolved organic matter (DOM) isolated from five waters, using a newly developed DOM isolation method specific to DON fractionation, produced thirty-four isolates of suitable mass. Each isolate was treated with free chlorine or chloramines under formation potential conditions. The DBP yields were determined for three halogenated DBPs (trichloromethane, dichloroacetonitrile, and trichloronitromethane) and one non-halogenated DBP (N-nitrosodimethylamine [NDMA]). Halogenated DBP yields were greater during the application of free chlorine, however chloramination produced significant levels of halogenated N-DBPs for some isolates. NDMA was only observed to form from selected nitrogen-enriched isolates (DOC/DON ratio < 20 mg/mg), especially those isolated from treated wastewater. Other results indicated that nitrogen-enriched DOM resulted in increased yields of the other N-DBPs studied.

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