Anaerobic membrane bioreactor for real antibiotic pharmaceutical wastewater treatment: Positive effect of fouling layer on antibiotics and antibiotic resistance genes removals

Anaerobic membrane bioreactor (AnMBR) is a potential candidate for high-strength pharmaceutical wastewater treatment. However, its contribution to reduce the antibiotic and antibiotic resistance genes (ARGs) is still largely unclear. Herein, this study investigated the antibiotics and ARGs removal in AnMBR for real high-strength antibiotic (levofloxacin (LEV)) pharmaceutical wastewater treatment, focusing on the positive effect of membrane fouling layers (biofilms). Results indicated that membrane biofilm has a positive effect on AnMBR treatment with improved COD and LEV removal efficiency by 12% and 10%, respectively. This might be ascribed to the enhanced biodegradation ability of the organic matter by the biofilm due to the enrichment of fermentation bacteria (Anaerobium), hydrogen-producing bacteria (Clostridium_sensu_stricto_1) and hydrogenotrophic methanogenic archaea (Methanobacterium and Methanobrevibacter). Importantly, the membrane biofilm can also effectively mitigate the ARGs (qnrS, qnrA) and class 1 integrator (intI1) dissemination and the absolute abundance of ARGs in the medium fouling (MF) biofilm effluent was 0.27 orders of magnitude lower than that of low fouling (LF) biofilm effluent. This can be explained by the variation of membrane surface becoming more hydrophobic in MF than LF biofilm with increased contact angle and more negative surface zeta potential, suggesting higher adsorption and adhesion properties. The strong correlation between extracellular polymer substance (EPS) and soluble microbial product (SMP) contents and qnrA, qnrS and intI1 further indicated the important role of EPS and SMP in membrane biofilm on ARGs reduction. Furthermore, the entrapment of ARGs potential hosts bacteria of Comamonas and Enterococcus with high biofilm formation potential also attributed to the improved ARGs removal with the increase of membrane fouling degree. Our findings suggest that AnMBR is effective for antibiotic pharmaceutical wastewater treatment and membrane biofilm has a positive effect on antibiotic and ARGs removal, which promotes the AnMBR application in the pharmaceutical industry.

Automated summary

This study investigated the removal of antibiotics and antibiotic resistance genes (ARGs) in an anaerobic membrane bioreactor (AnMBR) for high-strength antibiotic pharmaceutical wastewater. The results showed that the membrane biofilm had a positive effect on AnMBR treatment, improving the removal efficiency of chemical oxygen demand (COD) and levofloxacin (LEV) by 12% and 10%, respectively. The membrane biofilm also effectively reduced the dissemination of ARGs and class 1 integrator (intI1), with the ARGs abundance in the effluent of the medium fouling (MF) biofilm being significantly lower. The study indicated that AnMBR is effective for antibiotic wastewater treatment, with the membrane biofilm playing a crucial role in the removal of antibiotics and ARGs.