title: The role of aromatic precursors in the formation of haloacetamides by chloramination of dissolved organic matter.
abstract: Water treatment utilities are diversifying their water sources and often rely on waters enriched in nitrogen-containing compounds (e.g., ammonia, organic nitrogen such as amino acids). The disinfection of waters exhibiting high levels of nitrogen has been associated with the formation of nitrogenous disinfection byproducts (N-DBPs) such as haloacetonitriles (HANs) and haloacetamides (HAcAms). While the potential precursors of HANs have been extensively studied, only few investigations are available regarding the nature of HAcAm precursors. Previous research has suggested that HAcAms are hydrolysis products of HANs. Nevertheless, it has been recently suggested that HAcAms can be formed independently, especially during chloramination of humic substances. When used as a disinfectant, monochloramine can also be a source of nitrogen for N-DBPs. This study investigated the role of aromatic organic matter in the formation of N-DBPs (HAcAms and HANs) upon chloramination. Formation kinetics were performed from various fractions of organic matter isolated from surface waters or treated wastewater effluents. Experiments were conducted with (15)N-labeled monochloramine ((15)NH2Cl) to trace the origin of nitrogen. N-DBP formation showed a two-step profile: (1) a rapid formation following second-order reaction kinetics and incorporating nitrogen atom originating from the organic matrix (e.g., amine groups); and (2) a slower and linear increase correlated with exposure to chloramines, incorporating inorganic nitrogen ((15)N) from (15)NH2Cl into aromatic moieties. Organic matter isolates showing high aromatic character (i.e., high SUVA) exhibited high reactivity characterized by a major incorporation of (15)N in N-DBPs. A significantly lower incorporation was observed for low-aromatic-content organic matter. (15)N-DCAcAm and (15)N-DCAN formations exhibited a linear correlation, suggesting a similar behavior of (15)N incorporation as SUVA increases. Chloramination of aromatic model compounds (i.e., phenol and resorcinol) showed higher HAcAm and HAN formation potentials than nitrogenous precursors (i.e., amino acids) usually considered as main precursors of these N-DBPs. These results demonstrate the importance of aromatic organic compounds in the formation of N-DBPs, which is of significant importance for water treatment facilities using chloramines as final disinfectant.
authors.affiliation: Water Desalination and Reuse Center, 4700 KAUST, Thuwal 23955-6900, Saudi Arabia; LEESU (UMR MA 102), Université Paris-Est - AgroParisTech, 61 avenue du Général de Gaulle, 94010 Créteil cedex, France. Electronic address: julien.le-roux@u-pec.fr.
authors.forename: Julien
authors.initials: J
authors.lastname: Le Roux
authors.affiliation: Water Desalination and Reuse Center, 4700 KAUST, Thuwal 23955-6900, Saudi Arabia; Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. Electronic address: maolida.nihemaiti@postgrad.curtin.edu.au.
authors.forename: Maolida
authors.initials: M
authors.lastname: Nihemaiti
authors.affiliation: Water Desalination and Reuse Center, 4700 KAUST, Thuwal 23955-6900, Saudi Arabia; Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. Electronic address: jean-philippe.croue@curtin.edu.au.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Croué
mesh_terms: D000081:Acetamides / Q000737:chemistry; D002700:Chloramines / Q000737:chemistry*; D004202:Disinfectants / Q000737:chemistry; D005618:Fresh Water / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000737:chemistry; D007700:Kinetics; D009584:Nitrogen / Q000737:chemistry; D017672:Nitrogen Compounds / Q000737:chemistry; D062065:Wastewater / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D000081:Acetamides; D002700:Chloramines; D004202:Disinfectants; D006841:Hydrocarbons, Aromatic; D009584:Nitrogen; D017672:Nitrogen Compounds; D062065:Wastewater; C030816:chloramine
keywords: Aromatic compounds; Chloramination; Disinfection byproducts; Dissolved organic matter; Haloacetamides