Sci Total Environ . SARS-CoV-2 From Faeces to Wastewater Treatment: What Do We Know? A Review

[tetano]

Sci Total Environ


. 2020 Jun 24;743:140444.
doi: 10.1016/j.scitotenv.2020.140444. Online ahead of print.
SARS-CoV-2 From Faeces to Wastewater Treatment: What Do We Know? A Review


Paola Foladori ¹ , Francesca Cutrupi ² , Nicola Segata ³ , Serena Manara ³ , Federica Pinto ³ , Francesca Malpei ⁴ , Laura Bruni ⁵ , Giuseppina La Rosa ⁶



Affiliations

• PMID: 32649988
• PMCID: PMC7311891
• DOI: 10.1016/j.scitotenv.2020.140444

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.

[JJackson]

As the article points out finding bits of SARS-2 RNA by PCR is entirely different to finding live virus capable of starting a new infection. This brings us to a related problem regarding the status of SARS-2 as a BSL3 pathogen. There is a desperate need to understand routes of transmission during a pandemic's early exponential phase but while I can easily catch it at work or shopping I can not try and grow it from an environmental sample or sputum unless I have a BSL3 lab to do it in. A lack of these facilities means that obvious question like 'could sewage be a source of infection' are far more difficult to answer than they need to be. A NY ICU medic had 1700+ face to face sessions with active COVID patients in standard hospital PPE without infection. A BSL2 researcher, well trained with adequate PPE, is much safer doing sewage plaque assays at work than they would be outside the lab. This regulation needs changing urgently with only unusual strains or gain-of-function work done in BSL3, or 4, as appropriate. We could learn a lot more about this virus far more quickly.