Antibiotics removal from piggery wastewater by a novel aerobic-microaerobic system: Efficiency and mechanism

Abstract

Extensive use of antibiotics in pig farms presents chronic toxicity and induces antibiotic resistant genes in the natural environment. Tetracyclines (TCs), fluoroquinolones (FQs), and sulfonamides (SAs) are the widely detected antibiotics in manure-free piggery wastewater (MFPW) with the concentration of 4.92–164.60 μg/L. A novel combined sequencing batch reactor (SBR)-upflow microaerobic sludge reactor (UMSR) process has been demonstrated efficient in removing conventional pollutants from the MFPW. It is here shown that the SBR-UMSR process effectively removed 92.68 % of SAs and 82.23 % of TCs. The removal rate of FQs in the SBR-UMSR process was only 39.65 % due to the refractory properties. As a consequence, the total removal of antibiotics was 50.1 ± 32.5 % in the combined SBR-UMSR process, with the removal of 18.9 ± 36.6 % and 31.1 ± 24.3 % from the front-end SBR and back-end UMSR, respectively. Mass balance analysis proved that 54.18 % of antibiotics in the combined process were removed via biodegradation/biotransformation, and 12.75 % removal was achieved by sludge adsorption. Partial least-squares path model analysis and network analysis revealed that the biodegradation of antibiotics was mainly achieved by the metabolism of microorganisms with co-metabolism as a complement. The outcomes of this study provide valuable insights into the mechanism of antibiotic removal in biological processes.