Livestock manure improved antibiotic resistance gene removal during co-treatment of domestic wastewater in an anaerobic membrane bioreactor

Anaerobic membrane bioreactors (AnMBRs) can manage complex combined waste streams, recover energy, and produce nutrient-rich effluents for irrigation. To advance AnMBRs for water reuse, the removal of antibiotic resistance genes (ARGs) during co-treatment of waste streams requires further attention. Here, an AnMBR was fed domestic wastewater with increasing amounts of cattle manure. The removal of target genes including nine ARGs and two mobile genetic elements (MGEs) was assessed. Manure addition was found to significantly improve the removal of target genes, with a removal efficiency of 99.95% during the stage with the greatest addition of manure. Further, the effluent contained more cell-free ARGs (cfARGs) than cell-associated ARGs (caARGs) when manure loading was greatest. This study is the first to evaluate ARG and MGE removal during co-treatment of domestic wastewater and livestock manure using AnMBRs, and also the first to differentially characterize the cfARGs/caARGs in an AnMBR effluent treating complex waste streams.