Formation of brominated halonitromethanes from threonine involving bromide ion during the UV/chlorine disinfection

Abstract

Numerous disinfection by-products (DBPs) are produced during the disinfection process of drinking water and wastewater, and brominated halonitromethanes (Br-HNMs) have aroused great concerns because of much higher cytotoxicity and genotoxicity than common regulated DBPs. Threonine was selected as the precursor for the investigation of Br-HNMs formation in the presence of bromide ion (Br−) during the UV/chlorine disinfection. The results showed the yields of four Br-HNMs were enhanced with the increase of Br− concentration from 0.12 to 0.60 mM while tribromonitromethane (TBNM) was the most predominant species in the initial 5 min, and increasing Br− concentration promoted the yields of Br-HNMs species containing more bromine atoms. Besides, the yields of Br-HNMs were promoted with the increase of free chlorine dosage from 0.2 to 1.8 mM but inhibited with the increase of pH from 6.0 to 8.0. Subsequently, the possible formation pathways of Br-HNMs from threonine were proposed in the presence of Br− under the UV/chlorine condition. Finally, it was demonstrated that the formation laws of Br-HNMs in real waters in the presence of Br− were similar to that in simulated waters, whereas different concentrations of Br-HNMs and peak times in real waters were observed. These findings are beneficial for further understanding the formation of Br-HNMs and applying effective controls of the risks of Br-HNMs during the UV/chlorine disinfection.