Impact of bromide ion on the formation and transformation of halonitromethanes from poly(diallyldimethylammonium chloride) during the UV/chlorine treatment

Abstract

The formation of halonitromethanes (HNMs) is one of the major concerns when considering the application of UV/chlorine in the treatment of water containing bromide (Br-). The effects of Br- on the formation and transformation of HNMs from poly(diallyldimethylammonium chloride) during the UV/chlorine treatment were investigated in this study. The results showed that the incorporation of Br- was beneficial for producing reactive bromine species resulting in the changes of yields and dominant species of HNMs. With the increase of Br- concentration, the formations of brominated-HNMs (Br-HNMs) were promoted and the predominant species of HNMs were gradually converted from chlorinated-HNMs (Cl-HNMs) to brominated (chlorinated)-HNMs (Br(Cl)-HNMs) and Br-HNMs. Besides, the formation of HNMs increased with the increase of the ratio of Cl2:Br- and decreased with increasing pH from 6.0 to 8.0. According to the findings, the possible formation and transformation pathways of HNMs in the presence of Br- were proposed during the UV/chlorine treatment. Finally, it was proved that the effects of Br– on the formation and transformation of HNMs in real water were similar to that in deionized water. This study can help to understand the formation and transformation of HNMs better and develop effective measures for the control of HNMs (especially Br-HNMs) during the UV/chlorine treatment.