Control of disinfection byproducts in drinking water treatment plants: Insight into activated carbon filter.

The removal efficiencies of disinfection byproducts formation potentials (DBPFPs) and generated DBPs under pre-chlorination condition (pre-generated DBPs) during different drinking water treatment trains in eight full-scale drinking water treatment plants (WTPs) were investigated through field and laboratory studies. Haloacetic acids (HAAs) and haloacetonitriles (HANs) were identified to be two representative DBPs based on cytotoxicity and genotoxicity assessments. The performances of advanced treatment train for HAAs and HANs were better than that of conventional treatment train. However, the efficacy of ozone - biological activated carbon (O-BAC) was affected by its service time and position in the water treatment process. In addition, the consumption of free chlorine by activated carbon in old granular activated carbon (GAC) filter was higher than that in new one under pre-chlorination condition, resulting in the increase of HAAs and HANs in the GAC filter effluent. This demonstrated that the organic matter adsorbed on older activated carbon generated more HAAs and HANs during pre-chlorination, which inhibited the adsorption of pre-generated DBPs. The ability of GAC/O-BAC to remove HAAs and HANs was consistent with that of protein-like and low molecular weight organic substances, which could predict the performance of GAC and O-BAC in treating DBPs.