Elimination of antibiotics in seawater aquaculture effluent by peracetic acid: Reaction kinetics, pathways, and treatment efficiency

Abstract

Antibiotics are occasionally used in aquaculture industry for preventing fish mortality. There has been increasing concern on the occurrence and dissemination of antibiotic resistance in aquaculture a 8 with different levels of halides (i.e., chloride, bromide, and iodide) and real aquaculture effluent. The results were discussed based on 1) the formation of halogen oxidants from the reaction of PAA with halides, 2) the reaction of the halogen oxidants with PG and AMX, and 3) the reaction of the halogen oxidants with H2O2 forming halide and O2. Here, the latter two reactions can affect the process efficiency as the competing reactions for the halogen oxidants. Second-order rate constants for the reaction of PAA with PG and AMX at pH 8 were determined to be 10.6(±1.1) M-1s-1 and 31.9(±4.8) M-1s-1, respectively, which could be assigned to the reaction of PAA at the thioether moiety of the antibiotics. The degradation rate of PG decreased in the presence of halides for all cases. Thus, the halogen oxidants are expected to be rapidly consumed by their reaction with H2O2 before reacting with PG. In contrast, the degradation rate of AMX increased in the presence of chloride and bromide, indicating the contribution of the reactions of AMX with in-situ produced chlorine and bromine, which react very rapidly with the phenolic and amine moieties of AMX. The presence of iodide slightly decreased the degradation rate of AMX, indicating relative lower reactivity of iodine to AMX. Similar degradation kinetic behaviors of PG and AMX were observed in the real seawater aquaculture effluents but the degradation rates were generally lower than those in the synthetic buffer matrices. This could be due to the scavenging of the halogen oxidants by dissolved organic matter and ammonia present in the real aquaculture effluents. Overall, the kinetic information obtained from this study can be useful for designing the PAA-based treatment process of aquaculture effluent for antibiotic elimination.