Hi all…an interesting SARS-CoV-2 study was recently published in the journal Water Research. While most research has focused on wastewater and typically monitoring for SARS-CoV-2 RNA, this study examined virus viability and compared raw domestic wastewater with river water. While there are a number of interesting observations, the one that caught my eye, at least from a drinking water perspective, was the finding that “Remarkable increases in SARS-CoV-2 persistence were observed in assays at 4°C, which showed T90 values of 7.7 and 5.5 days, and T99 values of 18.7 and 17.5 days for RW and WW, respectively.”
For the most part, the virus is pretty well removed during wastewater treatment, and should be well removed during treatment in surface water treatment plants (and any systems that at least chlorinate continuously and efficiently). Perhaps this has implications for groundwater or infiltration wells (cottages, very small systems, etc.) when there are discharges to the environment other than from wastewater treatment plants?
Bill
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Viability of SARS-CoV-2 in river water and wastewater at different temperatures and solids content
Leonardo Camilo de Oliveira, Andrés Felipe Torres-Franco, Bruna Coelho Lopes, Beatriz Senra Álvares da Silva Santos, Erica Azevedo Costa, Michelle S. Costa, Marcus Tulius P. Reis, Marília C. Melo, Rodrigo Bicalho Polizzi, Mauro Martins Teixeira, César Rossas Mota
Water Research Volume 195, 1 May 2021, 117002
Abstract
“COVID-19 patients can excrete viable SARS-CoV-2 virus via urine and faeces, which has raised concerns over the possibility of COVID-19 transmission via aerosolized contaminated water or via the faecal-oral route. These concerns are especially exacerbated in many low- and middle-income countries, where untreated sewage is frequently discharged to surface waters. SARS-CoV-2 RNA has been detected in river water (RW) and raw wastewater (WW) samples. However, little is known about SARS-CoV-2 viability in these environmental matrices. Determining the persistence of SARS-CoV-2 in water under different environmental conditions is of great importance for basic assumptions in quantitative microbial risk assessment (QMRA). In this study, the persistence of SARS-CoV-2 was assessed using plaque assays following spiking of RW and WW samples with infectious SARS-CoV-2 that was previously isolated from a COVID-19 patient. These assays were carried out on autoclaved RW and WW samples, filtered (0.22 µm) and unfiltered, at 4°C and 24°C. Linear and nonlinear regression models were adjusted to the data. The Weibull regression model achieved the lowest root mean square error (RMSE) and was hence chosen to estimate T90 and T99 (time required for 1 log and 2 log reductions, respectively). SARS-CoV-2 remained viable longer in filtered compared with unfiltered samples. RW and WW showed T90 values of 1.9 and 1.2 day and T99 values of 6.4 and 4.0 days, respectively. When samples were filtered through 0.22 µm pore size membranes, T90 values increased to 3.3 and 1.5 days, and T99 increased to 8.5 and 4.5 days, for RW and WW samples, respectively. Remarkable increases in SARS-CoV-2 persistence were observed in assays at 4°C, which showed T90 values of 7.7 and 5.5 days, and T99 values of 18.7 and 17.5 days for RW and WW, respectively. These results highlight the variability of SARS-CoV-2 persistence in water and wastewater matrices and can be highly relevant to efforts aimed at quantifying water-related risks, which could be valuable for understanding and controlling the pandemic.”
