Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are an emerging concern in wastewater treatment plants, particularly when effluents are reused in agricultural or other applications where they could pose human health risks. As an alternative mainline wastewater treatment technology, anaerobic membrane bioreactors (AnMBRs) are becoming increasingly known for their association with both energy recovery and effluent reuse. AnMBRs feature significantly lower biomass yields, an anaerobic biochemical environment, and membrane separation that could ultimately mitigate the spread of antibiotic resistance to the environment during wastewater reuse. The purpose of this study was to determine the presence and abundance of ARB and ARGs in AnMBR systems and their effluents, and evaluate potential correlation between influent antibiotics and ARB/ARG profiles. To achieve this, a 5 L bench-scale AnMBR was operated using 3 separate submerged flat-sheet silicon carbide (ceramic) microfiltration membranes with 0.2 mm pore size. AnMBR performance was monitored by measuring water quality parameters and biogas characteristics. Biomass and effluent samples were also taken weekly for ARB quantification and ARG analysis using quantitative PCR (qPCR). High-throughput sequencing was used to evaluate microbial community structure. After an initial stabilization period, chemical oxygen demand (COD) of the effluent dropped to 29 ± 15 mg/L, resulting in a removal rate of 94 ± 3%. Results of ARG quantification showed that an erythromycin resistance gene (ermF) was the most abundant gene in suspended biomass, with an average copy number of 0.17 ± 0.05 ermF/16S rRNA gene. ermF abundance in biofilm biomass was significantly lower at 0.04 ± 0.01 ermF/16S rRNA gene. Conversely, a tetracycline-associated resistance gene (tetW) was found to be significantly more abundant in membrane biofilm biomass as compared to suspended biomass at 0.004 ± 0.0003 and 0.001 ± 0.0003 tetW/16S rRNA gene, respectively. Our findings suggest that membrane biofilms may play an important role in ARG attenuation and perhaps removal. Ongoing work is characterizing ARB/ARG effluent response to increasing concentrations of sulfamethoxazole and other antibiotics supplemented to the influent.

Investigation of anaerobic membrane bioreactor (AnMBR) potential to reduce antibiotic resistance proliferation and promote wastewater reuse

256th National Meeting (2018)

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