Effects of influent municipal wastewater microbial community and antibiotic resistance gene profiles on the anaerobic membrane bioreactor effluent

Municipal wastewater management is an important target area for reducing the spread of antibiotic resistance, especially given the parallel increasing need for water reuse. Anaerobic membrane bioreactors (AnMBRs) have the potential to play a key role in safely expanding non-potable wastewater reuse practices. In the present study, the effect of the commencing treatment of municipal wastewater by an AnMBR was evaluated after an extended startup phase using only synthetic wastewater. Antibiotic resistance genes (ARGs) associated with sulfonamides, tetracyclines, and β-lactams were quantified, and effluent microbial community progression was analyzed. Results indicated that the AnMBR effluent inherently harbored all targeted ARGs prior to the introduction of real wastewater (104–109 copies/100 mL effluent). sul1, sul2, and intI1 genes were notably higher initially than other genes and markedly increased after the system was transitioned to municipal wastewater. Although potentially pathogenic bacteria made up over 20% relative abundance of the influent, AnMBR effluents showed a marginalization of these groups as their microbial communities more closely resembled the tightly bound layer of membrane biofilms. This work highlights the need for emerging treatment systems to be evaluated on a basis that incorporates the differentiation of system-associated ARGs and assesses their environmental transmission potential within the effluent communities.