Degradation of the veterinary antibiotics in swine manure via anaerobic digestion

Abstract

Antimicrobial resistance is becoming an imminent danger for human health, in part because of excessive consumption of antibiotics in the animal industry. Laboratory-scale anaerobic digesters (ADs) were utilized to investigate the potential removal of veterinary antibiotics (VA) in swine manure. Nine laboratory ADs were kept at 39 [plus-minus] 2 [degrees] C in incubators and were loaded every two days. The digesters had a working volume of 1.38 L (in a 1.89-L glass jar), with a hydraulic retention time (HRT) of 21 days and a loading rate of 1.0 g-VS/L-day. Carbon dioxide concentration of the biogas and pH values of the digestate verifying digester performance were measured every four days and every week, respectively. The AD process allowed 2 HRT to stabilize before the addition of the VAs, of Chlortetracycline (CTC), Tylosin, and Sulfamethazine (SMZ). Tests were conducted to compare the effects of VAs on manure nutrients, volatile solid destruction, and biogas production. Concentrations of VA added to the manure samples were 263 to 298 mg/L of CTC, 88 to 263 mg/L of Tylosin, and 1042 to 1339 mg/L of SMZ, respectively. Analysis of VA concentrations before and after the AD process was conducted to determine the VA degradation. The process of measuring the relatively low VA concentrations involves using solid-phase extraction and LC-MS-MS methodology. Further tests were performed in water under room temperature and digester temperature to approve the degradation of VAs. Amplicon sequencing analysis performed on each group using the 50 most frequent amplicon sequence variants (ASVs) showed significant discriminations between groups. A hierarchical method (UPGMA) was applied to obtain the major alteration in bacterial dynamics between treatments. The biomarkers' abundance can be employed to distinguish different antibiotics contamination.