Proportion of bromo-DBPs in total DBPs during reclaimed-water chlorination and its related influencing factors

During the chlorine disinfection of reclaimed-water, the proportion of bromo-disinfection by-products (bromo-DBPs) in total DBPs is affected by chlorine dosage, reaction time, pH, ammonia nitrogen (NH3-N) and preozonation. Results show that bromo-trihalomethanes (bromo-THMs) form more easily than bromo-haloacetic acids (bromo-HAAs) and bromine incorporation in DBPs decreases with the increase of chlorine dosage. Within 5 h, bromine incorporation in THMs (n(Br)) increases but bromine incorpo-ration in HAAs (n′(Br)) decreases with the extension of reaction time; however, n(Br) decreases and n′(Br) keeps relatively constant at a longer reaction time. Furthermore, bromine incorporation in DBPs is low under acidic and alkaline conditions. The increase of NH3-N concentration inhibits the formation of chloro-DBPs, resulting in the increase of n(Br) and n′(Br) to some extent. Preozonation enhances the formation of HOBr and the increase of bromine incorporation in DBPs; however, ozone of a high con-centration oxidizes HOBr to its salt form, leading to the decrease of bromine incorporation in DBPs.