The fate of SARS-COV-2 in WWTPS points out the sludge line as a suitable spot for detection of COVID-19

https://doi.org/10.1016/j.scitotenv.2021.145268Get rights and content
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Highlights

  • Enveloped viruses in water, as SARS-CoV-2, have bigger affinity to biosolids.

  • The sludge line retains most SARS-CoV-2 particles.

  • Thickened sludge is a suitable spot for Covid-19 incidence monitoring.

  • SARS-CoV-2 rests were found in 6 wastewater and 15 sludge samples across the WWTP.

  • No SARS-CoV-2 RNA was detected in the effluent or in treated sludge.

Abstract

SARS-CoV-2 genetic material is detectable in the faeces of a considerable part of COVID-19 cases and hence, in municipal wastewater. This fact was confirmed early during the spread of the COVID-19 pandemic and prompted several studies that proposed monitoring its incidence by wastewater. This paper studies the fate of SARS-CoV-2 genetic material in wastewater treatment plants using RT-qPCR with a two-fold goal: i) to check its presence in the water effluent and in the produced sludge and ii) based on the understanding of the virus particles fate, to identify the most suitable spots for detecting the incidence of COVID-19 and monitor its evolution. On the grounds of the affinity of enveloped virus towards biosolids, we hypothesized that the sludge line acts as a concentrator of SARS-CoV-2 genetic material. Sampling several spots in primary, secondary and sludge treatment at the Ourense (Spain) WWTP in 5 different days showed that, in effect, most of SARS-CoV-2 particles cannot be detected in the water effluent as they are retained by the sludge line. We identified the sludge thickener as a suitable spot for detecting SARS-CoV-2 particles thanks to its higher solids concentration (more virus particles) and longer residence time (less sensitive to dilution caused by precipitation). These findings could be useful to develop a suitable strategy for early warning of COVID-19 incidence based on WWTP monitoring.

Keywords

SARS-CoV-2
Covid-19
Wastewater
Wastewater treatment plant
Incidence monitoring
Sludge

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