Insights into the formation of halonitromethanes from dimethylamine involving bromide ion during UV/chloramine disinfection

Abstract

Aliphatic amines are vital precursors of halonitromethane (HNMs), which pose a potential hazard to water safety. Bromide ions (Br−) have been reported to exert a significant effect on HNMs formation. However, the formation of HNMs from secondary aliphatic amine during UV/chloramine disinfection in the presence of Br− has rarely been studied. Hence, this work selected dimethylamine (DMA) as the model precursor and focused on the mechanism and impact factors of HNMs formation involving Br− during UV/chloramine disinfection. The results indicated that after adding 2 mg/L Br−, the total concentration of HNMs at 4 min increased up to 1.86-fold compared with adding 0.3 mg/L Br−. Moreover, brominated (chlorinated)-HNMs (Br(Cl)-HNMs) were gradually transformed into brominated-HNMs (Br-HNMs) with increased Br− concentration. While Br-HNMs would be transformed into Br(Cl)-HNMs with the increase of monochloramine concentration. The peak values of HNMs were promoted with the increase of DMA concentration but inhibited with the increase of pH. Notably, tribromonitromethane was the dominant species of HNMs involving Br− during UV/chloramine disinfection. The possible formation pathways of HNMs from DMA involving Br− during UV/chloramine disinfection were deduced. Finally, it was discovered that the formation of HNMs in real water was basically consistent with that in simulated water. The findings of this research are beneficial for comprehending the formation mechanism of HNMs from aliphatic amines and provide scientific measures to minimize the HNMs production during UV/chloramine disinfection.