The formation of haloacetamides and other disinfection by-products from non-nitrogenous low-molecular weight organic acids during chloramination

Abstract

Low-molecular weight organic acids (LMWOAs) are widespread in nature, and many are recalcitrant during conventional drinking water treatment, due to their LMW and hydrophilic character. This study assessed the formation of a range of disinfection by-products (DBPs) from the chloramination of seven non-nitrogenous LMWOA precursors, with an emphasis on the contribution of N-chloramine incorporation to haloacetamide (HAcAm) formation. The other DBPs comprised chlorinated halomethanes, haloacetonitriles and haloacetic acids. Citric acid generated higher yields of trichloromethane and two chloroacetic acids than the other LMWOAs. Further, the unsaturated acids (fumaric acid and itaconic acid) formed more chloroacetic acids than saturated acids (oxalic acid, succinic acid, adipic acid). Importantly, non-nitrogenous LMWOAs formed three nitrogenous DBPs (dichloroacetamide, trichloroacetamide, and small amounts of dichloroacetonitrile) during chloramination, firstly indicating the monochloramine can supply the nitrogen in nitrogenous DBPs, and the formation of haloacetamides at least in part is independent of the hydrolysis of haloacetonitriles. To the authors' knowledge, this is the first time formation of halogenated nitrogenous DBPs (N-DBPs) has been reported from chloramination of non-nitrogenous LMWOA precursors. This indicates that concentrations of dissolved organic nitrogen compounds in drinking water are not a reliable surrogate for formation of N-DBPs during chloramination. Bromine incorporation factor increased with increasing bromide during chloramination of citric acid, and bromine was easier to incorporate into di-HAcAms than mono-and tri-HAcAms during chloramination.

The formation of disinfection by-products from the chlorination and chloramination of amides

“…Generally, in the few samples that HANs were detected (pH 8), those yields were higher following chlorination and lower in chloramination than those of total HAcAm; with the exception of acetoacetamide. This pattern was in agreement with previous precursor studies of organic acids and natural organic matter solutions, that reported favouring of HAcAm formation via chloramination in the absence of bromide (Chu et al, 2016;Huang et al, 2017). In this study, of note, amide compounds at pH 7 generated undetectable levels of HANs upon chlorination, whereas upon chloramination TCAN (0.17 %M/M) was the only species at 24 hours in the β-alaninamide samples.…”

“…2b). It is noteworthy that when bromide was spiked at pH 7, HAcAm yields increased at least two-fold from those observed at pH 8, due to the increased stability at lower pH (Chu et al, 2016). Namely, acetamide samples under the same conditions generated 0.81% and 2.2% M/M upon chlorination, whereas generated 0.40% and 0.81% M/M upon chloramination, at pH 8 and 7 respectively.…”

“…As such, hydroxybenzamide samples upon chlorination yielded 0.45 ± 0.17% M/M (pH 7) and 0.14 ± 0.04% M/M (pH 8) of HAcAms after h, which then decreased to untectectable (pH 7) and 0. (Chu et al, 2016).…”

Controlled Microwave-Assisted Synthesis of the 2D-BiOCl/2D-g-C3N4 Heterostructure for the Degradation of Amine-Based Pharmaceuticals under Solar Light Illumination

“…The research work nowadays is oriented toward treatment of wastewater and drinking water from various organic contamination, more specifically from pharmaceuticals and personal care products. − Amine-based pharmaceuticals such as nizatidine, ranitidine, doxylamine, and carbinoxamine have attracted most researchers’ attention because of the ability of these compounds to produce toxic nitrogenous disinfection by-products (NDMPs), which are formed during the disinfection step. , Unfortunately, in conventional wastewater treatment some NDMPs have been detected after applying commonly used oxidants such as chlorine, chlorine dioxide, and potassium permanganate. − However, most of the recent studies focused on the occurrence of NDMP compounds and the potential risk on the environment resulting from such compounds. − On the other hand, only few studies have been undertaken photocatalytic degradation of amine-based pharmaceuticals as an alternative way of wastewater treatment. , …”

Predominant N-Haloacetamide and Haloacetonitrile Formation in Drinking Water via the Aldehyde Reaction Pathway

“…Because of the occurrence and elevated toxicity of HANs and HAMs, there is an emphasis on research efforts to characterize their formation mechanism relevant in drinking waters. − The formation of HANs and HAMs in drinking water has been hypothesized based on the origin of nitrogen atom in their molecule. Nitrogen-containing organic matter (i.e., amino acids, algal matter) could serve as a major precursor to form N-DBPs when it reacts with chlorine or chloramine via the decarboxylation pathway. − On the other hand, the nitrogen atom of the nitrile group or the amide group of HANs or HAMs could also come from monochloramine, an inorganic source, reacting with aldehydes − or aromatic compounds. ,,, All of these formation pathways may occur simultaneously and one pathway may become dominant at certain conditions. In two previous studies using 15 N-labeled-monochloramine, one reported >70% DCAN produced contained 15 N atom while the other demonstrated >92% of DCAN produced contained 15 N atom .…”