Do current water treatment methods eliminate SARS-CoV-19?

Environmental engineers have called for more research to determine if current water treatment methods effectively kill coronaviruses, including the SARS-CoV-19 virus responsible for the COVID-19 pandemic.

Coronaviruses can remain infectious for days, or even longer, in sewage and drinking water. Most drinking and wastewater treatment routines are thought to kill or remove coronaviruses effectively via oxidation with hypochlorous acid or peracetic acid, inactivation by ultraviolet irradiation, and chlorine. In wastewater treatment plants that use membrane bioreactors, the synergistic effects of beneficial microorganisms and the physical separation of suspended solids filter out viruses concentrated in the sewage sludge.

Two researchers — Associate Professor Haizhou Liu from the University of California, Riverside and Professor Vincenzo Naddeo, Sanitary Environmental Engineering Division Director at the University of Salerno — caution that most of these methods have not been studied for effectiveness specifically on SARS-CoV-19 and other coronaviruses, calling for additional research.

In an editorial for Environmental Science: Water Research & Technology, a leading environmental journal of the Royal Society of Chemistry in the United Kingdom, Haizhou and Naddeo reported that SARS-CoV-19 can be transported in microscopic water droplets or aerosols, which enter the air through evaporation or spray.

“The ongoing COVID-19 pandemic highlights the urgent need for a careful evaluation of the fate and control of this contagious virus in the environment,” Liu said. “Environmental engineers like us are well positioned to apply our expertise to address these needs with international collaborations to protect public health.”

During a 2003 SARS outbreak in Hong Kong, a sewage leak caused a cluster of cases via aerosolisation. Though no known cases of COVID-19 have been caused by sewage leaks, the novel coronavirus is closely related to the one that causes SARS, and infection via this route could be possible.

The novel coronavirus could also colonise biofilms that line drinking water systems, making showerheads a possible source of aerosolised transmission. This transmission pathway is thought to be a major source of exposure to the bacteria that causes Legionnaires’ disease, for example.

The environmental engineers suggest that existing water and wastewater treatment infrastructure should be upgraded in outbreak hotspots that are possibly exposed to coronavirus from places such as hospitals, community clinics and nursing homes. For example, energy-efficient, light-emitting, diode-based, ultraviolet point-of-use systems could disinfect water before it enters the public treatment system.

Potable water re-use systems, which purify wastewater back into tap water, also need thorough investigation for coronavirus removal and possibly new regulatory standards for disinfection, the researchers wrote.

The extent to which viruses can colonise biofilms also remains to be thoroughly investigated. Biofilms are thin, slimy bacterial growths that line the pipes of many ageing drinking water systems. Better monitoring of coronaviruses in biofilms might be necessary to prevent outbreaks.

The surge in household use of bactericides, virucides and disinfectants will probably cause an increase of antibiotic-resistant bacteria in the environment. Treated wastewater discharged into natural waterways demands careful monitoring through the entire water cycle. Liu and Naddeo call on chemists, environmental engineers, microbiologists and public health specialists to develop multidisciplinary and practical solutions for safe drinking water and healthy aquatic environments.

Additional concerns focus on rural and impoverished communities and developing countries, which lack the basic infrastructure to remove common contaminants and may be unable to remove SARS-CoV-19 from the water cycle. These places might experience frequent COVID-19 outbreaks that spread easily through globalised trade and travel. The researchers suggested that the governments of developed countries must support and finance water and sanitation systems wherever they are needed.

“It is now clear to all that globalisation also introduces new health risks. Where water and sanitation systems are not adequate, the risk of finding novel viruses is very high,” Naddeo said.

“In a responsible and ideal scenario, the governments of developed countries must support and finance water and sanitation systems in developing countries, in order to also protect the citizens of their own countries.”

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