Back in early April, we highlighted a paper that had been published as an Editorial Perspective in the Royal Society of Chemistry (RSC) journal “Environmental Science: Water Research & Technology”. This was “SARS-CoV-2: What is its fate in urban water cycles and how can the water research community respond?“ by Vincenzo Naddeo (University of Salerno Italy) and Haizhou Liu (University of California at Riverside, USA).
The same journal published a new Editorial Perspective this week, largely in response to that earlier perspective. The authors include many of the most established and widely recognised experts on public health management for drinking water and wastewater, particularly in the USA.
The authors respond to Naddeo & Liu’s concerns regarding potential impacts of COVID-19 and SARS-CoV-2 on purified recycled water for drinking (“potable reuse”). In doing so, they discuss the following factors that are each essential to understand the nature of any public health risks relating to emerging pathogens in drinking water sources:
- the range of concentrations of infective pathogens in the source water,
- the effectiveness of natural and engineered treatment barriers in removing or inactivating the pathogen, and
- the risk that consumption of the treated water will lead to an infection.
With regard to concentrations in source water, they state that current data show that concentrations are either consistent with or less than those of enteric viruses (e.g., enteroviruses, adenoviruses, and noroviruses), which are the traditional focus of potable reuse regulations and treatment. Furthermore, these data relate to the presence of viral RNA and do not imply that any significant portion of that RNA is associated with viable infectious viruses.
The authors highlight the generally (though not exclusively) unsuccessful attempts to recover infectious SARS-CoV-2 from stool samples, and one study demonstrating rapid inactivation of SARS-CoV-2 in the colonic (gut) fluids of the lower gastrointestinal tract. They argue that this likely explains the general lack of infectious SARS-CoV-2 in the faeces of infected individuals.
In designing treatment processes and developing operational criteria (e.g., disinfectant doses), the water industry often identifies representative pathogens with demonstrated resistance to treatment. The authors of this paper put forward an argument that the validated removal performances for treatment of these representative pathogens can be expected to at least as well achieved for SARS-CoV-2.
Based on the combination of both lower source water concentrations and higher removal through treatment, they argue that we should expect much lower exposures to SARS-CoV-2 in drinking water than the enteric viruses targeted by existing regulations and treatment.
Finally, the authors argue that it is unlikely that SARS-CoV-2 will be more infective in drinking water than other viruses, for which current regulations and risk management practices have been developed. Thus they expect existing potable reuse regulations developed in the context of a highly infectious enteric virus to be more conservative than if based on drinking water exposure to SARS-CoV-2.
In conclusion, the authors state that so far, the preliminary findings provide reassurance that SARS-CoV-2 is unlikely to be the ‘black swan’ that will reset the requirements for public health protection in the water industry. Current requirements for robust, multiple-barrier treatment systems evolved to reliably control a diversity of waterborne pathogens identified in the past. This same approach appears to be a solid foundation for the control of emerging and future pathogens as well.
Pecson B, Gerrity D, Bibby K, Drewes JE, Gerba C, Gersberg R, Gonzalez R, Haas CN, Hamilton KA, Nelson KL, Olivieri A, Rock C, Rose J and Sobsey M (2020) Editorial Perspectives: will SARS-CoV-2 reset public health requirements in the water industry? Integrating lessons of the past and emerging research. Environmental Science: Water Research & Technology.