Removal of antibiotics and antibiotic resistance genes in the synthetic oxytetracycline wastewater by UASB-A/O(MBR) process

Antibiotic wastewater contains not only conventional pollutants but also high concentrations of antibiotics and the resulting pollutants, such as antibiotic resistant microorganisms and antibiotic resistant genes (ARGs). If not properly treated, the antibiotic wastewater will further induce the spread of antibiotic resistant microorganisms and ARGs in the environment. In this study, an up-flow anaerobic sludge bed (UASB)-anoxic/aerobic (membrane bioreactor) process (A/O(MBR)) was built to treat oxytetracycline (OTC) wastewater. Results showed that the removal efficiencies of OTC decreased from 72.92% to 59.60% when the OTC concentration increased from 25 mg/L to 50 mg/L. Increasing OTC concentration from 0 to 50 mg/L, the chemical oxygen demand (COD) removal efficiencies decreased from 97.47% to 95.05%. Nevertheless, the total nitrogen removal efficiency increased from 55.53% to 85.33%. Bacteroides and Azospira dominated in UASB and A/O(MBR) respectively with the relative abundance of 20.76% and 18.51% at 50 mg/L OTC. Both ARGs in the UASB and O(MBR) increased with the rise of OTC concentration and reached 3.44 × 109 and 7.61 × 108 copies/mL respectively at 50 mg/L OTC. And the corresponding mobile gene elements (MGEs) reached 4.29 × 108 and 3.58 × 108 copies/mL. The membrane presented an effective pollutants removal efficiency with the interception efficiencies for ARGs and MGEs reaching 90.86% and 87.91%, respectively.