This paper presents a study in the survival of two representative coronaviruses (feline infectious peritonitis virus, and human coronavirus 229E) in filtered and unfiltered tap water (4 and 23°C) and wastewater (23°C). The survival of these coronaviruses was compared to poliovirus 1 under the same test conditions.
Inactivation of coronaviruses in the test water was highly dependent on temperature, level of organic matter, and presence of antagonistic bacteria.
The most critical influence on virus survival is temperature. The time required to achieve 3 log10-reduction (99.9% removal) revealed that in tap water, these particular coronaviruses were inactivated faster in water at 23°C (10 days) than in water at 4°C (>100 days).
The authors reported that “the presence of organic matter and suspended solids in water can provide protection for viruses that adsorb to these particles but at the same time can be a mechanism for removal of viruses if the solids settle out”. The found that coronavirus inactivation was greater in filtered tap water than unfiltered tap water. Furthermore, HCoV survived longer in unfiltered primary effluent over the filtered effluent. This suggests that higher solids do provide protection for coronaviruses in water.
An interesting observation was that there was a substantial decrease in surviving coronaviruses immediately upon addition to wastewater. Coronaviruses decreased immediately by 99.9%. This is compared to (non-enveloped) poliovirus 1, which decreased only 10%. The authors propose that this decrease may be due to the presence of solvents and detergents in wastewater that would compromise the viral envelope and ultimately inactivate the virus. Alternatively, it may indicate that coronaviruses adsorb more readily to solids in the wastewater: “The hydrophobicity of the viral envelope makes coronaviruses less soluble in water and could therefore increase the tendency of these viruses to adhere to the solids. Wastewater samples had to be filtered to prevent bacterial contamination of the cell monolayer, which would remove solids and any solids-associated viruses as well”.
The authors reported that coronaviruses die off rapidly in wastewater, with 99.9% removal observed after 2-4 days. This study demonstrates that the transmission of coronaviruses would be less than enteroviruses in the aqueous environment due to the fact that coronaviruses are more rapidly inactivated in water and wastewater at ambient temperatures.
REFERENCE
Gundy, P. M., Gerba, C. P. and Pepper, I. L. (2008) Survival of Coronaviruses in Water and Wastewater. Food and Environmental Virology, 1(1), 10.
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