Degradation of acesulfame in UV/monochloramine process: Kinetics, transformation pathways and toxicity assessment

UV/monochloramine (UV/NH2Cl) is an emerging advanced oxidation process that can generate various reactive species like reactive chlorine species (RCS) and hydroxyl radicals for micropollutant removal. This study investigated the potential toxicity of transformation products resulting from UV/NH2Cl treatment of acesulfame (ACE), as an example of micropollutant, found in worldwide aquatic environment. Compared with UV photolysis and chloramination, the UV/NH2Cl process more effectively degraded ACE. The transformation products of ACE treated with the UV/NH2Cl process were identified and characterized with high resolution mass spectrometry. The formation of chlorinated-TPs indicated the role of RCS in UV/NH2Cl transformation even though UV photolysis was predominantly responsible for the ACE degradation. The Vibrio fischeri bioluminescence inhibition assay revealed a higher toxicity of TPs derived from UV/NH2Cl than from UV photolysis. The increased toxicity could be attributed to most of the generated chlorinated-TPs (Cl-TPs), in particular those halo-alcohols. The ECOSAR program predicts that halo-alcohol TPs are more toxic than their non-chlorinated analogues and other Cl-TPs. This study provides insight into the important role of reactive species in the micropollutants' transformation of UV/NH2Cl process. It further provides information relevant to the potential risk when applying the process for micropollutant removal in water treatment.

Automated summary

UV/NH2Cl is an emerging advanced oxidation process for micropollutant removal, generating reactive chlorine species (RCS) and hydroxyl radicals. Transformation products of ACE treated with UV/NH2Cl were found to be more toxic, attributed to the chlorinated transformation products and specifically halo-alcohols. The study provides insight into the role of reactive species and potential risks in using UV/NH2Cl for micropollutant removal in water treatment.