Characteristics of Degradation Tetracyclines and Sulfonamides During Wastewater Treating Processes in an Intensive Swine Farm

Antibiotics and their metabolites are emerging contaminants posing a potential worldwide human health risk. Intensive animal husbandry is believed to be a major contributor to the increasing environmental burden of antibiotics. As to the antibiotics in animal manure in China, little information is available regarding characteristics of the degradation of antibiotics during wastewater treating processes in intensive animal husbandry. The aim of this study was to investigate concentrations of tetracyclines (TCs) and sulfonamides (SAs) types of antibiotics in wastewater and to explore their degradation characteristics during the processes of treating the wastewater in an intensive swine farm typical of the region of South Jiangsu in winter and summer. Results show that in wastewater treatment using the prevailing biogas digesters, as the incoming wastewater was high in pollutant concentration,and its hydraulic retention time was short, the treatment was only able to remove 12.9%-69.3%, 20.4%-60.9%, 25.3%-55.0%, 13.8%-18.2%, 46.8%-61.8% and 18.1%-48.7%, of the oxytetracycline (OTC), chlorotetracycline (CTC), doxycycline (DOX), sulfadiazine (SD), sulfadimidine (SM) and sulfachlorpyridazine (SCP) in the wastewater, respectively. Besides, residual concentrations of TCs and SAs in the treated wastewater were much higher in winter than in summer, especially that of CTC, SD and SCP being 0.887, 0.492 and 10.160 μg·L^-1, respectively, on average. Direct discharge of such wastewater from digesters into farm fields would pose high risks to biological safety. Post-treatment of the biogas slurry through a sedimentation tank and/or a pond with hydrophyte pond, had some positive effects on removals of TCs an SAs, especially in summer, when the residual removal rate could reach up to over 90%. So it is a critical measure to dehazardize biogas slurry for its safe use in farmlands. All the findings in this study demonstrate that the technology combining anaerobic and aerobic bio-treatment processes in removing antibiotics, SAs in particular, in wastewater from animal farms is a major and effective one.