Formation\nof Aromatic\nHalogenated Disinfection Byproducts\nin Swimming Pool Water during Chlorination: Organic Precursors and\nMechanisms

Disinfection byproducts (DBPs) in\nswimming pool water\nare a significant\npublic health concern. The formation of aromatic halogenated DBPs\nin swimming pool water has not been clarified previously. In this\nstudy, the occurrence of aromatic halogenated DBPs in swimming pool\nwater was examined, and it was found that halohydroxybenzoic acids\n(HBAs) and halobenzoquinones (HBQs) were the most dominant aromatic\nhalogenated DBPs in swimming pool water that were continuously formed.\nThus, the formation of HBAs and HBQs in swimming pool water from different\norganic precursors, including natural organic matter (NOM), pharmaceuticals\n and personal care products (PPCPs), during chlorination was examined.\nThe results demonstrate that the formation of HBAs and HBQs from the\nPPCPs was relatively high compared with that from NOM, suggesting\nthat the PPCPs from human inputs might be important organic precursors\nof aromatic halogenated DBPs in swimming pool water. The formation\nmechanisms of HBAs and HBQs from three typical PPCPs (benzophenone-3\n(BP-3), methyl p-hydroxybenzoate (MeP) and carbamazepine) were further\nexplored. The results show that the PPCPs containing phenolic groups\nwith higher degradation rates (BP-3 and MeP) possessed higher formation\nof HBAs and HBQs. The three organic precursors underwent a series\nof substitution, hydrolysis, oxidation, rearrangement, and intramolecular\ncyclization reactions to form HBAs and HBQs, while the phenolic groups\nand ring structures may significantly affect the reactions. The chlorine\ndose, bromide/iodide concentration, and temperature significantly\naffected the formation of HBAs and HBQs from MeP during chlorination.