In this study, livestock wastewater treatment plants in South Korea were monitored to determine the characteristics of influent and effluent wastewater, containing four types of veterinary antibiotics (sulfamethazine, sulfathiazole, chlortetracycline, oxytetracycline), and the removal efficiencies of different treatment processes. Chlortetracycline had the highest average influent concentration (483.7 μg/L), followed by sulfamethazine (251.2 μg/L), sulfathiazole (230.8 μg/L) and oxytetracycline (25.7 μg/L), at five livestock wastewater treatment plants. Sulfathiazole had the highest average effluent concentration (28.2 μg/L), followed by sulfamethazine (20.8 μg/L) and chlortetracycline (11.5 μg/L), while no oxytetracycline was detected. For veterinary antibiotics in the wastewater, a removal efficiency of at least 90% was observed with five types of treatment processes, including a bio-ceramic sequencing batch reactor, liquid-phase flotation, membrane bioreactor, bioreactor plus ultrafiltration (BIOSUF) and bio best bacillus systems. Moreover, this study evaluated the removal efficiency via laboratory-scale experiments on the conventional contaminants, such as organic matter, nitrogen, phosphorus and veterinary antibiotics. This was done using the hydraulic retention time (HRT), under three temporal conditions (14 h, 18 h, 27 h), using the anaerobic–anoxic–oxic (A2O) process, in an attempt to assess the combined livestock wastewater treatment process where the livestock wastewater is treated until certain levels of water quality are achieved, and then the effluent is discharged to nearby sewage treatment plants for further treatment. The removal efficiencies of veterinary antibiotics, especially oxytetracycline and chlortetracycline, were 86.5–88.8% and 87.9–90.8%, respectively, exhibiting no significant differences under various HRT conditions. The removal efficiency of sulfamethazine was at least 20% higher at HRT = 27 h than at HRT = 14 h, indicating that sulfamethazine was efficiently removed in the A2O process with increased HRT. This study is expected to promote a comprehensive understanding of the behavior and removal of veterinary antibiotics in the livestock wastewater treatment plants of South Korea.
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