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Coronaviruses and SARS-CoV-2 in sewerage and their removal: Step by step in wastewater treatment plants - PubMed

  • ️Sat Jan 01 2022

Review

Coronaviruses and SARS-CoV-2 in sewerage and their removal: Step by step in wastewater treatment plants

Paola Foladori et al. Environ Res. 2022.

Abstract

The fate of Coronaviruses (CoVs) and in particular SARS-CoV-2 in wastewater treatment plants (WWTPs) has not been completely understood yet, but an adequate knowledge on the removal performances in WWTPs could help to prevent waterborne transmission of the virus that is still under debate. CoVs and SARS-CoV-2 are discharged from faeces into the sewer network and reach WWTPs within a few hours. This review presents the fate of SARS-CoV-2 and other CoVs in the primary, secondary and tertiary treatments of WWTPs as well as in sludge treatments. The viral loads decrease progressively along with the treatments from 20 to 3.0E+06 GU/L (Genomic Units/L) in the influent wastewater to concentrations below 2.50E+05 GU/L after secondary biological treatments and finally to negative concentrations (below detection limit) in disinfected effluents. Reduction of CoVs is due to (i) natural decay under unfavourable conditions (solids, microorganisms, temperature) for relatively long hydraulic retention times and (ii) processes of sedimentation, filtration, predation, adsorption, disinfection. In primary and secondary settling, due to the hydrophobic properties, a partial accumulation of CoVs may occur in the separated sludge. In secondary treatment (i.e. activated sludge) CoVs and SARS-CoV-2 loads can be reduced only by about one logarithm (∼90%). To enhance this removal, tertiary treatment with ultrafiltration (Membrane Bioreactors) and chemical disinfection or UV light is needed. CoVs and SARS-CoV-2 in the sludge (1.2E+04-4.6E+08 GU/L) can be inactivated significantly in the thermophilic digestion (55 °C), while mesophilic temperatures (33-37 °C) are not efficient. Additional studies are required to investigate the infectivity of SARS-CoV-2 in WWTPs, especially in view of increasing interest in wastewater reclamation and reuse.

Keywords: Coronaviruses; SARS-CoV-2; Sewage; Sludge; Wastewater; Wastewater treatment plants.

Copyright © 2021 Elsevier Inc. All rights reserved.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1

Flow-sheet of various configurations of WWTPs. Secondary treatments: (A) Activated sludge with nutrient removal; (B) Sequencing Batch Reactors; (C) Membrane Bioreactors; (D) Moving Bed Biofilm Reactor; (E) UASB. Tertiary treatments: (F) Chlorine-based disinfection; (G) Ozone and AOPs-based disinfection; (H) Ultraviolet light.

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