AC25 Assessment of virus removal and infectivity during municipal wastewater treatment: implications for safe reuse

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Pathogen control and monitoring in water reuse applications is critical to public health protection and gaining public trust. As more utilities and water agencies consider implementing water reuse programs, obtaining credit for log reduction values (LRV) achieved through secondary and tertiary wastewater treatment processes will be an important consideration. While many utilities exploring reuse options are currently focused on membrane processes to achieve additional virus log removal credits, questions remain regarding LRV achieved through various conventional treatment trains. In addition, while molecular assays exist for the detection of viruses, the majority of these methods provide no information on culturability or infectivity thus making extrapolation of end-user exposure risk and identification of suitable applications challenging. The objective of this study was to assess the removal of human infective viruses throughout the stages of wastewater treatment in a full-scale, tertiary municipal wastewater treatment plant in Canada. 

The plant resells 20% of its secondary effluent to an industrial partner after additional treatment by membrane filtration and chlorination. The remaining 80% of the secondary effluent undergoes UV disinfection prior to release into the environment. The partnership between the plant and the industrial partner produces 15 million liters of high-quality water for processing each day, which are used in the refinery cooling tower, boiler and hydrogen plant. Virus concentrations and infectivity were analysed using real-time quantitative PCR (qPCR) and integrated cell culture (ICC) to identify infective human viruses. Seven viruses including Norovirus (NoV), Rotavirus (RV), Sapovirus (SaV), Astrovirus (AsV), Adenovirus (AdV), Enterovirus (EV) and JC virus (JCV) were detected in 16 primary effluent samples in which infective viruses were present. Different treatment steps showed various efficiencies in infective virus removal, with membrane filtration exhibiting the highest at 4.6–7.0 log reductions. 

The overall treatment virus LRV ranged from 1.1 (RV) to 2.8 (EV) for UV-treated final effluent and from 4.6 (EV) to 7.0 (AdV) when membrane filtration and chlorination were applied. The LRV for the six viruses (except for EV) by membrane filtration were significantly greater than that obtained by UV. EV had the highest inactivation by UV but the lowest by membrane filtration.

Learning Objectives:
After the presentation, participants will be able to articulate the benefits and limitations of different viral testing methods and the potential value that coliphage testing might add.
After the presentation, particpants will be able to compare the removal of viruses after various treatment steps.
After the presentation, particpants will have more data to highlight the value and potential virus log removal credits that can be achieved by ultrafiltration (6–7 LRV)."

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