Trihalomethane yields from twelve aromatic halogenated disinfection byproducts during chlor(am)ination

As the first identified category of disinfection byproducts (DBPs), trihalomethanes (THMs) have received continuous attention. Previous studies have demonstrated that the transformation of aromatic halogenated DBPs during chlor (am)ination resulted in the formation of THMs, which may occur in both water treatment plants and drinking water distribution systems. In this study, THM yields from aromatic chlorinated/brominated DBPs during chlorination and aromatic iodinated DBPs during chloramination were investigated. The trichloromethane (TCM) yields from 3,5-dichloro-4-hydroxybenzaldehyde, 3,5-dichlorosalicylic acid, 2,6-dichloro-4-nitrophenol, and 2,4,6-trichlorophenol were in the range of 0-11.4%, 0-8.4%, 0-6.4%, and 0-17.8%, respectively. The THM₄ (TCM, bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM)) yields from 3,5-dibromo-4-hydroxybenzaldehyde, 3,5-dibromosalicylic acid, 2,6-dibromo-4-nitrophenol, and 2,4,6-tribromophenol were in the range of 0-12.9%, 0-27.0%, 0-8.6%, and 0-29.4%, respectively. The TCM and triiodomethane (TIM) yields from 3,5-diiodo-4-hydroxybenzaldehyde, 3,5-diiodosalicylic acid, 2,6-diiodo-4-nitrophenol, and 2,4,6-triiodophenol were in the range of 0-5.2%, 0-7.0%, 0-2.2%, and 0-10.6%, respectively. After 72 h, TCM yields from aromatic chlorinated DBPs were generally higher than that from their brominated analogues; TBM yields from aromatic brominated DBPs were significantly lower than TCM yields, BDCM yields, and DBCM yields; and among aromatic halogenated DBPs, 2,4,6-trihalophenol had the highest THM yields while 2,6-dihalo-4-nitrophenol had the lowest THM yields. Moreover, the results revealed that alkaline conditions and higher temperatures favored the THM yields from the twelve aromatic halogenated DBPs during chlor (am)ination, and chlorine/monochloramine dose affected the yields and speciation of THMs from the aromatic halogenated DBPs.