Removal of veterinary antibiotics from anaerobically digested swine wastewater using an intermittently aerated sequencing batch reactor

In this study a lab-scale intermittently aerated sequencing batch reactor (IASBR) was applied to treat anaerobically digested swine wastewater (ADSW) to explore the removal characteristics of 11 veterinary antibiotics (including tetracyclines, sulfonamides, quinolones and macrolides). Both sludge sorption and biodegradation were found to be the major contributors to the removal of veterinary antibiotics. Mass balance analysis revealed that greater than 60% of antibiotics in the influent were biodegraded in the IASBR, whereas averagely 24% were adsorbed by sludge under the condition that sludge sorption gradually reached its equilibrium. Results showed that the removal of antibiotics was greatly influenced by chemical organic demand (COD) volumetric loading, which could achieve up to 85.1% ± 1.4% at 0.17 ± 0.041 kg COD/(m³·day), while dropped to 75.9% ± 1.3% and 49.3% ± 12.1% when COD volumetric loading increased to 0.65 ± 0.032 and 1.07 ± 0.073 kg COD/(m³·day), respectively. Tetracyclines, the dominant antibiotics in ADSW, were removed by 87.9% in total at the lowest COD loading, of which 30.4% were contributed by sludge sorption and 57.5% by biodegradation, respectively. In contrast, sulfonamides were removed about 96.2%, almost by biodegradation. Long solid retention time (SRT) seemed to have little obvious impact on antibiotics removal, while a shorter SRT of 30–40 days could reduce the accumulated amount of antibiotics. The ratio of COD to total nitrogen (TN) in the influent was regarded as an unimportant impact factor for the removal of veterinary antibiotics in this work. More safe and strict management of the treated ADSW and the antibiotic-contaminated sludge should be investigated and applied in practice.