Comparison of UV/chloramine disinfection of methylamine water in the absence and presence of bromide: Halonitromethanes formation, toxicity alteration, and reaction mechanisms

Abstract

UV/chloramine is considered a new potential disinfection process to substitute traditional disinfection methods, and the participation of bromide (Br−) significantly influences halonitromethanes (HNMs) formation during UV/chloramine disinfection. Herein, the formation laws of HNMs from methylamine were explored and compared during UV/chloramine disinfection with and without the existence of Br−. The results indicated that there were similar formation laws of HNMs between the disinfection processes with and without the existence of Br− but different species and productions of HNMs were observed. Furthermore, both the total HNMs productions during UV/chloramine disinfection with and without the existence of Br− were markedly enhanced when increasing chloramine dosage while those were significantly reduced when increasing solution pH from 6.0 to 8.0. Also, it was pointed out that Br− dramatically strengthened the toxicity of HNMs, and the toxicity alteration of HNMs was consistent with the changes in the yields of total HNMs with reaction time. Meanwhile, the reaction mechanisms of HNMs formed from methylamine were speculated during UV/chloramine disinfection with and without the existence of Br−, and Br− presented a non-negligible impact on the formation mechanisms. Finally, the formation laws of HNMs in two real water samples were found to be similar to that in simulated water samples during UV/chloramine disinfection, while different species and yields of HNMs were simultaneously observed. This work illustrated HNMs formation from methylamine and the significant impacts of Br− on HNMs generation during UV/chloramine disinfection.