SARS-CoV-2 from faeces to wastewater treatment: What do we know? A review

Paola Foladori; Francesca Cutrupi; Nicola Segata; Serena Manara; Federica Pinto; Francesca Malpei; Laura Bruni; Giuseppina La Rosa

doi:10.1016/j.scitotenv.2020.140444

SARS-CoV-2 from faeces to wastewater treatment: What do we know? A review

Sci Total Environ. 2020 Nov 15:743:140444. doi: 10.1016/j.scitotenv.2020.140444. Epub 2020 Jun 24.

Authors

Paola Foladori¹, Francesca Cutrupi², Nicola Segata³, Serena Manara³, Federica Pinto³, Francesca Malpei⁴, Laura Bruni⁵, Giuseppina La Rosa⁶

Affiliations

¹ Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77, 38123 Trento, Italy. Electronic address: paola.foladori@unitn.it.
² Department of Civil, Environmental and Mechanical Engineering, University of Trento, via Mesiano 77, 38123 Trento, Italy.
³ Department of Cellular Computational and Integrative Biology-CIBIO, Via Sommarive 9, 38123 Trento, Italy.
⁴ Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza L. da Vinci, 32, 20133 Milano, Italy.
⁵ ADEP, Agenzia per la Depurazione (Wastewater Treatment Agency), Autonomous Province of Trento, via Gilli 3, 38121 Trento, Italy.
⁶ Department of Environment and Health, National Institute of Health, Rome, Italy.

Abstract

SARS-CoV-2, the virus that causes COVID-19, has been found in the faeces of infected patients in numerous studies. Stool may remain positive for SARS-CoV-2, even when the respiratory tract becomes negative, and the interaction with the gastrointestinal tract poses a series of questions about wastewater and its treatments. This review aims to understand the viral load of SARS-CoV-2 in faeces and sewage and its fate in wastewater treatment plants (WWTPs). The viral load in the faeces of persons testing positive for SARS-CoV-2 was estimated at between 5·10³ to 10^7.6 copies/mL, depending on the infection course. In the sewerage, faeces undergo dilution and viral load decreases considerably in the wastewater entering a WWTP with a range from 2 copies/100 mL to 3·10³ copies/mL, depending on the level of the epidemic. Monitoring of SARS-CoV-2 in sewage, although no evidence of COVID-19 transmission has been found via this route, could be advantageously exploited as an early warning of outbreaks. Preliminary studies on WBE seem promising; but high uncertainty of viral loads in wastewater and faeces remains, and further research is needed. The detection of SARS-CoV-2 in sewage, based on RNA sequences and RT-PCR, requires a shared approach on sample pre-treatment and on-site collection to ensure comparable results. The finding of viral RNA in stools does not imply that the virus is viable and infectious. Viability of CoVs such as SARS-CoV-2 decreases in wastewater - due to temperature, pH, solids, micropollutants - but high inactivation in WWTPs can be obtained only by using disinfection (free chlorine, UVC light). A reduction in the quantity of disinfectants can be obtained by implementing Membrane-Bioreactors with ultrafiltration to separate SARS-CoV-2 virions with a size of 60-140 nm. In sludge treatment, thermophilic digestion is effective, based on the general consensus that CoVs are highly sensitive to increased temperatures.

Keywords: Coronavirus; Faeces; Outbreak; SARS-CoV-2; Sewage; Wastewater treatment.

Publication types

Review

MeSH terms

Betacoronavirus*
COVID-19
Coronavirus Infections*
Feces
Humans
Pandemics*
Pneumonia, Viral*
SARS-CoV-2
Wastewater*

Substances

Waste Water