Precursors of Dichloroacetamide, an Emerging Nitrogenous DBP Formed during Chlorination or Chloramination

Abstract

Haloacetamides (HAcAms) are an emerging class of nitrogenous disinfection byproducts (N-DBPs). However, there is a limited understanding about the precursors of HAcAms. In this study, we screened the precursors of dichloroacetamide (DCAcAm), the most commonly identified HAcAm in chlorinated or chloraminated drinking water. DCAcAm formation potential (FP) of raw water samples collected in different months from a reservoir in China was determined during chlorination, and the highest DCAcAm FP typically occurred in the summer samples. Dissolved organic matter (DOM) in a representative summer raw water sample was separated into six fractions by a series of resin elutions. Among them, hydrophilic acid (HiA) DOM showed the maximum DCAcAm FP, followed by hydrophilic bases (HiB) and, to a much lower extent, hydrophobic acids (HoA). Fluorescence excitation-emission matrix (EEM) spectra revealed that a mass of protein-like substances in the HiA fraction, made up of amino acids (AAs), were the likely DCAcAm precursors. Finally, we investigated the DCAcAm yields of 20 AAs during chlorination. Among them, seven AAs (aspartic acid, histidine, tyrosine, tryptophan, glutamine, asparagine, phenylalanine) could form DCAcAm during chlorination, with the corresponding DCAcAm yields of 0.231, 0.189, 0.153, 0.104, 0.078, 0.058, and 0.050 mmol/mol AA.

Formation of halogenated C-, N-DBPs from chlor(am)ination and UV irradiation of tyrosine in drinking water

“…chain of an amino acid (Reckhow et al,2001;Chu et al, 2010b), where -CH 2 -is an 324 electron-donating group. The chlorine substitution reaction rate in -CH 2 -of Tyr was faster 325 than many other amino acids, probably because of the R-group including an aromatic 326 ring in the side chain of Tyr, which enhanced the electron-donating ability of -CH 2 -in the 327 main chain of Tyr (Chu et al, 2010b).…”

“…The chlorine substitution reaction rate in -CH 2 -of Tyr was faster 325 than many other amino acids, probably because of the R-group including an aromatic 326 ring in the side chain of Tyr, which enhanced the electron-donating ability of -CH 2 -in the 327 main chain of Tyr (Chu et al, 2010b). The aromatic ring in the R-group was probably 328 broken by a strong oxidizer (e.g., hydroxyl radical, Table S3 of Ala (Chu et al, 2009b).…”

A predictive model for the formation potential of dichloroacetamide, a nitrogenous disinfection by-product formed during chlorination

“…The chlorine dose is almost proportional to the DOC value of water samples in DCAcAm FP test (Chu et al 2010b). All other disinfection conditions, i.e., reaction time (24 h), pH (7.5), and temperature (24°C), were kept constant in all trials.…”

Characterization of dissolved organic matter for prediction of trihalomethane formation potential in surface and sub-surface waters

“…These risks include formation of disinfection by-products (DBP), including trihalomethanes (THM), haloacetic acids, iodo-acids, halonitromethanes, nitrosamines, and dichloroacetamide that form when natural organics matter (NOM) reacts with chemical disinfectants [20,21]. Chow et al [19] reported that significant amounts of DBP precursors in sub-surface waters can be attributed to the leaching of organics from deciduous litter of surrounding vegetation, emphasizing the influence of catchment sub-surface water on reservoir water quality and consequently on DBP formation.…”

“…Chow et al [19] reported that significant amounts of DBP precursors in sub-surface waters can be attributed to the leaching of organics from deciduous litter of surrounding vegetation, emphasizing the influence of catchment sub-surface water on reservoir water quality and consequently on DBP formation. The concentration and character of DOM significantly influences raw and treated water quality and DBP formation [9,20,22].…”