Anaerobic membrane bioreactors (AnMBRs)
are an emerging technology
with potential to improve energy efficiency and effluent reuse in
mainstream wastewater treatment. However, their contribution to the
proliferation of contaminants of emerging concern, such as antibiotic
resistance genes (ARGs), remains largely unknown. The purpose of this
study was to determine the effect of select influent antibiotics at
varying concentrations on the presence and abundance of ARGs in an
AnMBR system and its effluent. Quantification of targeted ARGs revealed
distinct profiles in biomass and effluent, with genes conferring resistance
to different antibiotic classes dominating in biomass (macrolides)
and effluent (sulfonamides). Effluent sul1 gene abundance
was strongly correlated with abundance of intl1,
signifying the potential importance of mobile genetic elements in
ARG release from AnMBR systems. The addition of specific antibiotics
also affected normalized abundances of their related ARGs, exemplifying
the potential impact of selective pressures at both low (10 μg/L)
and high (250 μg/L) influent antibiotic concentrations.
A bench-scale AnMBR was operated for the treatment of domestic wastewater containing antibiotics and evaluated microbial community structure and antibiotic resistance gene dynamics in both the biomass and effluent.
The growing need for potable reuse of wastewater has led to significant development and implementation of advanced treatment processes. However, the emergence of new safety concerns (e.g., antibiotic resistance) necessitates an ongoing evaluation of current and future reuse schemes to demonstrate both water security and public safety. This study elucidates the microbial community and antibiotic resistance gene (ARG) profiles of a 100 million gallon per day (MGD) advanced water treatment facility (AWTF). A concurrent evaluation of the groundwater aquifer that is recharged with AWTF product water was also performed to determine the fate of specific microbial targets in the downstream environment. Results indicated that the AWTF reduced nearly all targeted ARGs to below detection limits (<50 copies/L). In groundwater samples, however, a ubiquitous presence of ARGs conferring resistance to sulfonamides (sul1 and sul2) and β-lactams (oxa-1) was observed (10 4 −10 6 copies/ L) in both AWTF-recharged locations and control locations. Microbial community analysis via 16S rRNA gene sequencing further showed that the AWTF treatment train effectively excluded any upstream wastewater microbial community characteristics from the product water. Groundwater receiving AWTF recharge through percolation basins was greatly influenced by its proximity to a river that is known to receive conventional wastewater treatment plant effluents.
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