Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes have been detected in wastewater worldwide. However, the assessment of SARS-CoV-2 infectivity in wastewater has been limited due to the stringent requirements of biosafety level 3. The main objective of this study is to investigate the applicability of capsid integrity RT-qPCR for the selective detection of intact SARS-CoV-2 in wastewater. Three capsid integrity reagents, namely ethidium monoazide (EMA, 0.1–100 μM), propidium monoazide (PMA, 0.1–100 μM), and cis-dichlorodiammineplatinum (CDDP, 0.1–1000 μM), were tested for their effects on different forms (including free genomes, intact and heat-inactivated) of murine hepatitis virus (MHV), which was used as a surrogate for SARS-CoV-2. CDDP at a concentration of 100 μM was identified as the most efficient reagent for the selective detection of infectious MHV by RT-qPCR (CDDP-RT-qPCR). Next, two common virus concentration methods including ultrafiltration (UF) and polyethylene glycol (PEG) precipitation were investigated for their compatibility with capsid integrity RT-qPCR. The UF method was more suitable than the PEG method since it recovered intact MHV (mean ± SD, 38% ± 29%) in wastewater much better than the PEG method did (0.013% ± 0.015%). Finally, CDDP-RT-qPCR was compared with RT-qPCR alone for the detection of SARS-CoV-2 in 16 raw wastewater samples collected in the Greater Tokyo Area. Five samples were positive for SARS-CoV-2 when evaluated by RT-qPCR alone. However, intact SARS-CoV-2 was detected in only three positive samples when determined by CDDP-RT-qPCR. Although CDDP-RT-qPCR was unable to determine the infectivity of SARS-CoV-2 in wastewater, this method could improve the interpretation of positive results of SARS-CoV-2 obtained by RT-qPCR.

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Ultraviolet (UV) light-emitting diode (UV-LED), a disinfection technology, efficiently inactivates pathogens in water. However, the assessment of UV-LED treatment and the mechanisms of UV inactivation on viruses (especially enveloped viruses)...

Microfiltration (MF) has been widely adopted as an advanced treatment process to reduce suspended solids and turbidity in treated wastewater effluents designated for potable reuse. Although microfilter pores are much larger than viruses, the addition of a coagulant upstream of a microfilter system can achieve stable virus removal. Ceramic membranes have a narrow pore size distribution to achieve the high removal of contaminants. This study aims to evaluate virus log reduction using bench-scale coagulation and ceramic membrane MF. To investigate the effects of differences in net surface hydrophobicity, 18 sewage-derived F-specific RNA phages (FRNAPHs) were used for batch hydrophobicity and coagulation–MF tests. The capability of bench-scale coagulation and ceramic membrane MF under continuous automated long-term operation was tested to remove the lab reference strain MS2 and three selected FRNAPH isolates which varied by surface property. Median virus log reduction values (LRVs) exceeding 6.2 were obtained for all three isolates and MS2. Although coagulation and hydrophobicity were positively correlated, the virus isolate demonstrating the lowest level of hydrophobicity and coagulation (genogroup I) still exhibited a high LRV. Thus, coagulation and ceramic membrane MF systems may serve as viable options for virus removal during water reclamation and advanced treatment.

The implementation of precoagulation prior to the physical removal process is expected to attain a high virus removal rate. However, a risk exists for viruses to form small flocs and subsequently escape into the effluent of physical removal processes. This study evaluated how the virus in the microflocs could be quantified by conventional virus quantification methods (Plaque assay and quantitative PCR (qPCR) assay). In this study, the microflocs dissolution phenomenon in a phosphate buffer solution was employed as a floc dissolving test and virus concentrations before and after floc dissolving were quantified. The findings revealed an increase in virus concentrations by > 1.0 − >3.9 log pfu/ml by the Plaque assay and by 1.7 − >4.0 log copies/ml by the qPCR assay, following the dissolution of microflocs prepared in the humic acid test water. In the case of treated wastewater, the concentration increases were confirmed in all samples by the Plaque assay and in 7 out of 8 samples by the qPCR assay. Fewer viruses were detected in the microflocs that remained undissolved by either Plaque assay or qPCR assay.