Transformation of antibacterial agent roxithromycin in sodium hypochlorite disinfection process of different water matrices

Abstract

The effects of water matrices on the reaction kinetics and transformation products of roxithromycin (ROX) with sodium hypochlorite (NaClO) were investigated. It was found that the removal efficiency of ROX was dependent on the type of disinfected water. For simulated fresh water, marine culture water and seawater, the reaction rate constant was 0.0521 min−1, 0.0757 min−1 and 0.106 min−1, respectively. The bromide ions in seawater and marine culture water not only promoted the reaction of ROX with NaClO but also caused the generation of brominated DBPs (Br-DBPs). Four DBPs including one chlorinated DBP (Cl-DBP) and three Br-DBPs were identified. The cladinose moiety and C14 atom were the main reaction centers which were easily attacked by disinfectant in fresh water. The desosamine moiety was also broken away from the parent compound ROX in the simulated marine culture water and seawater. Adsorbable organic halogen (AOX) analysis demonstrated that the Br-DBPs in water samples containing bromide ions were generally more carcinogenic than the Cl-DBPs formed in fresh water.