Membrane biological reactor (MBR) can achieve a complete retention of antibiotic resistance bacteria, thus can serve as a sharp edge for the reduction of intracellular antibiotic resistance genes (ARGs) in activated sludge. However, little is known about the fate of extracellular ARGs (eARGs) in MBR. Here we performed real-time quantitative PCR to evaluate the prevalence of eight eARGs and one mobile gentic element (MGE) in two different forms,including ARGs adsorbed on activated sludge or membrane module and ARGs free in wastewater in five full-scale MBRs. Results show high abundance of adsorbed eARGs were detected in all MBRs, with the values of 5.4×103 – 1.5×107 copies eARGs/mg volatile suspended solids (VSS) in activated sludge and 1.8×102 – 1.7×106 copies eARGs/cm2 in membrane module. Relative high level of MGE, i.e., intI1, and its significant correlations (p &lt; 0.05) with eARGs on membrane module, indicating that intI1 may be involved in widespread of ARGs in MBRs. Only three free eARGs, i.e., sulI, sulII and tetM, were found in wastewater samples, and the removal rates of above three eARGs were ranging from 14% to 94% after MBRs treatment. Notably, different levels of eARGs were still detected or even enriched in all MBR effluents. The findings elucidate extracellular DNA in MBR is a potential ARGs reservoir, and additional optimization of operating condition and parameter is needed for effective elimination of this emerging contaminant.

Prevalence and elimination of extracellular antibiotic resistance genes in five full-scale membrane reactors

253rd National Meeting (2017)

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