Wastewater Testing as a COVID‐19 Early Warning System

Wastewater Testing as a COVID‐19 Early Warning System

Trussell Technologies staff conducting wastewater sampling as part of a WRF research project.

Today, everyone knows that individuals can be tested for current COVID‐19 infections or for the presence of antibodies that suggest a past infection. What fewer people may realize is that wastewater can be tested for residual genetic material that signals that SARS- CoV-2, commonly known as the coronavirus that causes COVID‐19, is present within a community. This broad snapshot of coronavirus presence within a community can provide an invaluable early warning of an outbreak to public health officials. One institution that is helping to advance research into this method of detection is The Water Research Foundation (WRF). In addition to funding research itself, it has helped to facilitate information interchange among the many global utilities and research groups that are implementing and improving this method of testing. In this interview, WRF CEO Peter Grevatt tells Municipal Water Leader about how this method of testing works and its advantages.

Municipal Water Leader: Please tell us about your background and how you came to be at your current position at WRF.

Peter Grevatt: Prior to joining WRF as CEO, I had a 30‐year career with the U.S. Environmental Protection Agency (EPA). I served in a variety of roles at the EPA, and during my last 6 years there, I was the director of the National Drinking Water Program. In that position, I had a lot of experience working with municipal water leaders of all types as a regulator. In terms of my academic background, I have a doctorate in environmental health from the basic medical sciences program at New York University Medical Center. That gives me a grounding in the public-health aspects of the services that the water sector provides. Protecting public health and the environment is fundamentally what water utilities are there to do.

Municipal Water Leader: Would you introduce WRF?

Peter Grevatt: WRF is the world’s leading research collaborative supporting the water sector. We do research on a broad range of topics, focused on helping the water sector to do its work to protect public health and the environment most efficiently and effectively.

Most of our research is funded by our subscribers. We work with our subscribers to identify their most important research priorities, oversee the carrying out of that research, and provide the results back to our subscribers. We have over 1,200 subscribers across six continents, more than 1,000 of which are water utilities, some of them public and municipal, others private and investor owned. We also have subscribers that work in environmental consulting and manufacturing.

We also receive some support from state governments, the federal government, and private grant-making foundations. For example, we have received two grants from the State of California to support its work on direct potable reuse as well as grants from the U.S. Department of Energy, the National Science Foundation (NSF), and the EPA. We have also received grants from private foundations, such as the Bill & Melinda Gates Foundation.

Municipal Water Leader: WRF has recently supported research into testing wastewater for traces of the coronavirus that causes COVID‐19. Would you describe this method of detection and when it was discovered that it might be appropriate for the coronavirus?

Peter Grevatt: Wastewater can tell an important story about the health of a community. To start at the beginning, every living organism has a blueprint—a set of instructions that dictate how the various proteins and other compounds that make it up are to be constructed. In humans, that is DNA. For the coronavirus, that genetic material is RNA. The genetic material is present in every individual virus, and it often remains long after the virus is no longer capable of infecting a host and causing disease. That means that even noninfectious viral particles—dead viruses, so to speak— may still contain this RNA genetic blueprint. There are highly sensitive techniques that can detect small amounts of this RNA even in a complex matrix like wastewater, which contains many different compounds. These techniques can establish that the coronavirus was present in the community from which the wastewater has been collected. That’s the basic idea of environmental surveillance: Looking not for live virus, but for the genetic material that proves that the virus was present in a community.

This has all been unfolding at an incredibly rapid pace. None of us even knew about COVID‐19 until the beginning of this year, but we already have some sensitive methods to detect the presence of the coronavirus by doing wastewater surveillance. Because there’s a long history of using these sorts of tools to detect other pathogenic organisms—poliovirus is one of the best examples—a number of research groups across the globe quickly decided to try to tailor these tools to detect SARS‐CoV‐2 as well.

Municipal Water Leader: The genetic material you’re talking about no longer poses a health threat or health risk, correct?

Peter Grevatt: That’s right. Only a live virus can infect a host and cause disease. However, even after the viral particles break apart, at which point the viruses are no longer viable, the genetic material can remain present in wastewater. While the genetic material has been identified in wastewater in many different communities, I’m not currently aware of any community where live virus has been identified in wastewater. That is an important distinction. We’re not talking about a material that presents a health risk; we’re just talking about material that can serve as a signal of the presence of COVID‐19 in a community.

Municipal Water Leader: What are some of the different testing methods that are used to detect the presence of that material?

Peter Grevatt: Most of them use an analytical technique called polymerase chain reaction, which can identify small amounts of genetic material in the wastewater. It’s almost like a microscopic photocopying machine: There may be only a small number of copies of the genetic material from the coronavirus present in the wastewater, but the polymerase chain reaction replicates them again and again until you can begin to detect them. It amplifies the signal and allows you to see it. That’s the core technique that’s being used, and there are a variety of approaches to applying it. One of the important research projects that WRF currently has underway is comparing those various methods to determine which are most reproducible and provide the most reliable results.

Municipal Water Leader: What are some of the advantages of testing wastewater for the presence of the coronavirus, as opposed to other testing methods, like testing individual people?

Peter Grevatt: One of the biggest advantages of testing wastewater is that it’s cost effective. That is because it is so sensitive. A number of research groups have demonstrated that this tool can detect the presence of as few as 1–3 cases in a population of 100,000. If you are working with a community that has either not yet had a high level of cases or has overcome its first wave, this tool can serve as an early warning system. A number of groups have found that they were able to see a change in the trend line of COVID‐19 cases through wastewater surveillance nearly a week before clinical cases were identified in the community. This has been demonstrated both in Europe and in the United States and both in large cities and small towns. It is both an efficient and an effective tool and supplements the other tools that are available for tracking COVID‐19 trends.

Wastewater surveillance is certainly not a substitute for clinical testing, which remains tremendously important in terms of addressing COVID‐19, but it is a great way to supplement the information provided by clinical testing.

Because wastewater surveillance looks for the presence of COVID‐19 across the entire community that is served by a wastewater treatment plant, it is not biased in terms of the demographic background of the individuals being tested— race, economic background, employment status, national background, etc. It captures information from everyone. That broad snapshot is tremendously valuable.

Municipal Water Leader: Please tell us about WRF’s recent symposium, the International Water Research Summit on Environmental Surveillance of COVID-19 Indicators in Sewersheds.

Peter Grevatt: WRF is a global organization that operates on six continents, and in early spring of this year, we saw that many different research groups and utilities across the globe were simultaneously embarking on projects to see if they could use the environmental surveillance of wastewater as a way to track trends of COVID‐19 in communities. We thought we could surely accelerate progress if we brought all these groups together to share information about the approaches they were using, and that it would also help identify areas where there were significant gaps in understanding that could be filled through near-term research. That’s exactly what we did. We brought together groups from over 10 countries. We found that the research groups and utility participants were incredibly generous in their willingness to share their information openly. We asked them to identify what they currently understood as the best practices for environmental surveillance for COVID‐19 in wastewater. We also asked them to identify near-term research priorities. We took that information and published a summary of recommended best practices and the near-term research priorities that we have used to guide our own efforts to accelerate the progress of this work. It was tremendously successful, in large part because we had the right people there and because people are so generous in sharing their information.

Municipal Water Leader: Would you tell us about the findings of the research and the new avenues for research that you’ve identified?

Peter Grevatt: First, we heard that several groups have now demonstrated the viability of these tools for detecting SARS‐CoV‐2. That was important. Secondly, our participants talked about what they referred to as potential use cases for this information. For example, one use case is to use the information to track trends of COVID‐19 infections in the community. Another potential use case would be using this information to estimate the number of cases in the community. There are other potential use cases, like using this information to better understand the genetic variants of the virus present in individual communities. Some people have been working to understand whether the virus in Europe is different from the virus in Asia or the United States, and if so, how it affects the infectivity of the virus or the health outcomes of people who become infected.

The participants agreed that the most immediately relevant use case is the tracking of trends. As I mentioned, wastewater monitoring has been able to successfully detect the arrival of SARS‐CoV‐2 in communities nearly a week before the first clinical cases were identified. For example, Erica Gaddis, who is on the advisory committee for one of our research projects, has been overseeing an effort in Utah to track the presence of the coronavirus in a number of different communities in the state. In Cache County, she was able to see the signal appear almost a week before the first cases were found. Ultimately, two meatpacking facilities in Cache County experienced outbreaks, with hundreds of cases. It’s a powerful tool because it alerts public health officials that something is going on in a community and allows them to focus on it. It may help them target the application of clinical testing.

As for near-term research priorities, our participants said that we’ve got to get our arms around the variety of methods being used and make sure we understand which ones are most replicable and reliable in terms of the results they generate. They also said it was important for us to get a better understanding of how the genetic signal changes over time as it passes through the wastewater collection and treatment system. One potential application of this work is to begin testing specific areas of the community rather than just collecting wastewater samples at a central treatment plant. For example, you might want to understand the contribution of cases from a hospital, university, prison, or meatpacking facility to the overall signal detected at the wastewater treatment plant. You can target those areas for the collection of samples. However, in order to take that kind of approach, you really need to understand how the genetic material changes as it travels through the system—how much of it is breaking down or being bound up with other materials as it travels through the sewer system. We have another research project focused on that question, which is looking at how to develop appropriate sampling plans.

A third area of research that our participants identified relates to the preservation of the samples that are collected. Many communities are now collecting and archiving samples, recognizing that they may want to go back and analyze those samples in the future. With that in mind, we would like to know more about the effects on the genetic signal of freezing and thawing a sample. How long can a sample be preserved in a refrigerator or a freezer without a significant change in the signal strength?

We’re currently pursuing research in all three of those areas that were identified during the summit. Not only has WRF been interested in this, but the NSF and the Bill & Melinda Gates Foundation are partnering in our efforts as well.

Peter Grevatt is the CEO of the Water Research Foundation. He can be contacted at pgrevatt@waterrf.org.