Degradation of halogenated disinfection byproducts in water distribution systems

Water distribution systems are complex environments frequently containing corroded iron pipes and biofilms. To thoroughly understand the fate of halogenated disinfection byproducts (DBPs) in these systems, two degradation processes were investigated: Abiotic degradation (i.e. hydrolysis and reductive dehalogenation) and biodegradation. DBPs were selected from 6 different compound classes representing both regulated DBPs (i.e. trihalomethanes or THMs, and haloacetic acids or HAAs) and non-regulated or "emerging" DBPs. Batch experiments were conducted to investigate the pathways and kinetics of DBP degradation. As expected, the relative importance of hydrolysis, abiotic reductive dehalogenation, and biodegradation depends on the DBP structure and on the environmental conditions (i.e. pH, temperature, dissolved oxygen, Fe minerals present, bacteria present, etc.). From our results, chloropicrin (i.e. trichloronitromethane) and most brominated DBPs are highly susceptible to abiotic reductive dehalogenation, trichloracetonitrile and trichloropropanone are the most susceptible to hydrolysis, and HAAs are readily biodegraded under aerobic conditions. Knowledge of DBP degradation mechanisms and rates in distribution systems is important for selecting DBP monitoring locations, modeling DBP fate, and for predicting exposure to these compounds. Such information could also be useful for developing treatment systems for DBP removal.