Membrane bioreactors (MBR) have better removal of emerging organic contaminants such as antibiotics, antibiotic resistance genes (ARG) and microbial contaminants compared to activated sludge processes. In addition, anaerobic membrane bioreactors (AnMBR) have advantages over aerobic configuration as it produces methane as an energy source and have a lower sludge production rate.However, full scale AnMBR have not been implemented as widely as aerobic MBR (AeMBR) and the removal of microbial contaminants for AnMBR when treating real wastewater has not been well studied. It is necessary to evaluate the microbial risks and performance of these systems to facilitate implementation of AnMBRs.
We assessed a pilot AnMBR (36 L operating volume) in terms of microbial contaminants removal as it relates to operational parameters. The performance of the AnMBR was compared with a full-scale aerobic MBR receiving the same influent. Operational parameters e.g. hydraulic retention time (HRT), transmembrane pressure (TMP), organic loading rate (OLR) as well as water quality indicators were measured. Flow cytometry was used to measure the log reduction value (LRV) of total cells. Community analysis by 16S rRNA gene-based amplicon sequencing was performed to evaluate if there is a selective removal of certain bacterial groups by the AnMBR. An average LRV of 2 was achieved by the AnMBR, and this LRV was consistent and comparable to the full-scale aerobic MBR. LRV has moderate correlation with nitrate and nitrate content of the influent and COD removal. There are differences in the removal of bacterial populations achieved by AnMBR and AeMBR.These results provide guidance about the microbial risks and the relation between the AnMBR operational parameters and microbial contaminants removal.
