Formation of nitrogen-containing disinfection by-products during the chloramination treatment of an emerging pollutant

Chloramination was commonly used as disinfectant for killing pathogens in water. However, in this process, nitrogen-containing disinfection by-products (N-DBPs) would accidently form and subsequently rise toxicity. Here, we investigated acute toxicity variation and by-products formation during chloramination treatment on UV filter 2-hydroxy-4-methoxy-5-sulfonic acid benzophenone (BP-4). Under alkaline conditions, the acute toxicity of this system had significant increase. A total of 17 transformation products were tentatively identified, and for them, plausible transformation pathways were proposed. Noticeably, numerous aniline and nitrosobenzene analogs were detected, and the dramatic increase of acute toxicity in this system might be primarily attributed to the formation of benzoquinone and aniline analogs. Besides, bromophenol, iodophenol and iodobenzoquinone analogs exhibiting high toxicity were generated in the presence of bromine and iodide ions. This study indicates that chloramination treatment may significantly increase potential health risk, further management on disinfection system is reasonable. [Display omitted] •Acute toxicity increased during BP-4 chloramination process.•A total of 17 transformation products were tentatively identified.•A total of 14 nitrogen-containing products were tentatively identified.•Numerous aniline and nitrosobenzene analogs were detected.•Nucleophilic substitution was the main pathway for introducing nitrogen atom.