Interface behavior and removal mechanisms of human pathogenic viruses in anaerobic membrane bioreactor (AnMBR)

Effective removal of human pathogenic viruses is an indispensable yet rarely studied aspect for sustainable treatment of domestic wastewater by anaerobic membrane bioreactor (AnMBR). In this study, the interface behaviors and removal mechanisms of norovirus genogroup I (GI), genogroup II (GII), and rotavirus A from domestic wastewater was systematically investigated in a one-stage AnMBR. On average, norovirus GI, GII and rotavirus were reduced by 4.64, 5.00, and 2.31 logs, respectively. Viruses tended to be transferred to larger-sized suspended solids from sewage influent to the mixed liquor, and the weight-specific concentration of the virus in >100 μm particles of the mixed liquor was significantly higher than that of sewage, indicating a particle scale-dependent affinity with the virus. In-series membrane filtration test showed the main contribution of the membrane retention, which was dominated by the bio-cake layer and the pristine membrane, while the membrane and associated pore foulants can retain viruses in a filtration resistance-efficient way. An unsteady-state mass balance model revealed that free viruses in the bulk liquid of AnMBR were minimally attached to the cake layer but mainly retained by the membrane and pore foulants (>99%). In addition, despite the small virus decay rates in the mixed liquor, the associated contribution increased with run time due to the prolonged sludge retention time. These insights into virus behaviors and removal mechanisms may provide novel regulation strategies for enhanced virus removal by AnMBR.