Nonhalogenated Aromatic DBPs in Drinking Water Chlorination: A Gap between NOM and Halogenated Aromatic DBPs

Abstract

Halogenated disinfection byproducts (DBPs) are generated via reactions with natural organic matter (NOM) in chlorine disinfection of drinking water. How large NOM molecules are converted to halogenated aliphatic DBPs during chlorination remains a fascinating yet largely unresolved issue. Recently, many relatively toxic halogenated aromatic DBPs have been identified in chlorinated drinking waters, and they behave as intermediate DBPs to decompose to halogenated aliphatic DBPs. There is still one gap between NOM and halogenated aromatic DBPs. In this study, nine nonhalogenated aromatic compounds were identified as new intermediate DBPs in chlorination, including 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, 3-formyl-4-hydroxybenzoic acid, salicylic acid, 5-formyl-2-hydroxybenzoic acid, 4-hydroxyphthalic acid, 4′hydroxyacetophenone, 4-methylbenzoic acid, and 4-hydroxy-3-methylbenzaldehyde. These nonhalogenated aromatic DBPs formed quickly and reached the maximum levels at relatively low chlorine doses within a short contact time, and their formation pathways were proposed. The formation kinetics of three nonhalogenated aromatic DBPs and their corresponding monochloro-/dichlorosubstitutes during chlorination were then modeled. The nonhalogenated aromatic DBPs contributed up to 84% of the formed monochloro-substitutes and 22% of the formed dichloro-substitutes, demonstrating that they somewhat acted as intermediates between NOM and halogenated aromatic DBPs. Furthermore, the formed nonhalogenated aromatic DBPs were found to be removed by >50% by granular activated carbon adsorption.

The competitive effect of Electro-chlorination over chlorination for controlling disinfection by-product formation in phenol and aniline enriched groundwater

“…The very low removal efficiency of total phenol was achieved due to the formation of several phenol-based chlorination by-products such as 2-Oxo-4-phenyl-6-(4chlorophenyl)-1,2-dihydropyrimidine, 5-chloro-4,6-diphenyl-, 2,3,4,6-tetrachlorophenyl ester, etc. The formation of chloro-phenols due to the chlorination of phenols present in the water was also reported by Jiang et al, (2020). While, in the case of electro-chlorination, removal efficiencies of 99.47% and 98.48% were achieved for aniline and phenol concentrations, respectively, because of their oxidation into simpler forms.…”

Development and Application of High-Precision Algorithm for Non-Target Identification of Organohalogens Based on Ultrahigh-Resolution Mass Spectrometry

“…Totally, 102 and 243 newly formed and chlorination-derived putative non-halogenated byproducts were identified in this study (Table S5), including two reported nonhalogenated byproducts decomposed from X-DBPs, C8H6O4 and C8H6O5, 44 . The newly formed C8H6O5 was absent in non-chlorinated SRNOM.…”

“…4 and S9). Although precursor inspection is a useful filter rule for the accurate detection of X-DBPs in disinfected waters, it should be noted that precursors for the "secondary X-DBPs" (formed by the decomposition of precursor via multiple degradation pathways) 43,44 were difficult to be validated in the halogenated samples due primary to their multiple formation mechanisms. It has been reported that the major of carbonyl DBPs contains ketoacid structure, which are generated most likely due to the phenyl ring-cleavage of halogenated macromolecular phenols, such as lignin-derived moieties in SRNOM 45 .…”

“…Non-halogenated byproducts are often formed during the disinfection treatment, revealing the mechanism of X-DBPs formation 44,53,54 . In addition to non-halogenated byproducts with low molecular weights detected with conventional chromatographic and mass techniques, the NOMDBP Code is capable of simultaneously assigning formulae to non-halogenated byproducts with larger molecular weights in the FT-ICR-MS spectra.…”

Tetracycline antibiotics as precursors of dichloroacetamide and other disinfection byproducts during chlorination and chloramination

“…Thus, the identification of HAcAm precursors has attracted much attention ( Chen and Westerhoff, 2010 ). Aromatic molecules are found to be converted into halogenated aliphatic DBPs during chlorination ( Jiang et al., 2020 ). An amide side chain in a tetracycline antibiotic consisting of four aromatic rings may be easily attacked by oxidants to form DCAcAm, which is the most abundant HAcAm species formed in water ( Bond et al., 2011 ).…”