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Study Abstract
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A membrane bioreactor (MBR)-based wastewater treatment plant was assessed for its efficacy to treat and remove viruses from untreated wastewater over a 9-month period. Viral diversity were detected by omics-based approaches. Adenoviruses (AdV) and enteroviruses (EV) were enumerated for their log reduction values (LRV) by digital PCR, and assessed for their infectious particles load using cell culture and immunofluorescence staining. The findings revealed that MBR treatment was successful in reducing the number of viral species throughout the treatment train. However, plant viruses like cucumber green mottle mosaic virus and melon necrotic spot virus remained abundant in the treated effluent. The presence of these plant viruses in treated effluent can undermine the use of such waters for agricultural irrigation. Human enteric viruses were present in comparatively lower abundance than the plant viruses, and were effectively removed by the MBR although at varying LRV for different enteric viruses. AdV copy numbers were reduced by 3.7-logs through the MBR. No infectious AdV particles were found in effluent. In contrast, EV were less effectively removed by the MBR process. The EV copy numbers reduced by 1.7-logs post MBR while infectious EV decreased by an average of 2.0-logs. However, infectious EV remained in the chlorinated effluent, and occasionally in concentrations that approximate to the infectious dose. Overall results showed that a MBR-based WWTP effectively reduced viral diversity, viral load and its infectious capacity. However, differences in the removal efficiencies between AdV and EV particles were observed. Coupled with the presence of infectious EV particles in the chlorinated effluent, the findings suggest a potential concern arising from EV during reuse events. In addition, assessment of treated water quality should take into consideration of both infectious viral concentrations and LRV-centric guidelines.
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