Suspect and Nontarget Screening of Coexisting Emerging Contaminants and Aromatic Halogenated Disinfection Byproducts in Drinking Water Distribution Systems

Emerging contaminants (ECs) are increasingly discharged into the aquatic environment and cannot be removed by conventional water treatment processes. The detection of various disinfection byproducts (DBPs) originating from ECs as possible precursors is challenging. Herein, liquid chromatography coupled with time-of-flight mass spectrometry was used for the suspect and nontarget screening of ECs and DBPs simultaneously in the effluent of drinking water treatment plants and distribution systems. Forty-one ECs and 27 DBPs were identified, corresponding to different confidence levels (1–3). Pesticides, pharmaceuticals, and personal care products accounted for approximately 63% of the ECs. Halophenols and halonitrophenols were the predominant categories of aromatic DBPs. Three EC species [4-nitrophenol, 3-methyl-4-nitrophenol, and enrofloxacin] and their confirmed DBPs [2,6-dichloro-4-nitrophenol, 2-bromo-6-chloro-4-nitrophenol, 2,6-dibromo-4-nitrophenol, 2-bromo-4-nitrophenol, and 3-chloro-5-(chloromethyl)-4-nitrophenol] were simultaneously detected in the drinking water distribution system. The intensity of aromatic DBPs initially increased and then decreased with transportation in branched drinking water distribution systems, consistent with the quantification results. Thus, the transportation process in drinking water distribution systems impacts DBP formation.