Tracking COVID in wastewater

Now that pandemic-focused attention has turned to preventive measures such as the recently approved Pfizer and BioNTech vaccines, much of the public discussion has been centered on who can get the vaccine and when. But as pharmaceutical companies are toiling away developing and distributing vaccines, another group of scientists has been tracking COVID-19 without needing to test a single patient. A coalition of North Carolina university researchers, led by Principal Investigator Rachel Noble, is monitoring COVID-19 viral shedding in wastewater to better understand which communities have been affected by the virus.

Noble’s team consists of members from the University of North Carolina (UNC) System campuses, including UNC Chapel Hill, UNC Wilmington, UNC Charlotte, East Carolina University, and North Carolina State University. Their work is funded by a $1.8 million grant from the North Carolina Policy Collaboratory, funded through Federal CARES Act funding.

Similar university, government, and privately funded studies of viral shedding in wastewater are being conducted in multiple jurisdictions throughout the United States and in many countries worldwide.

Virus shed in wastewater

When people have a viral respiratory infection, they often (but not always) shed a significant portion of viruses in their fecal material. When infected individuals in a community contribute their fecal material to the community wastewater system, viral pathogens that end up in the raw wastewater stream are then transmitted from homes and businesses to wastewater treatment facilities.

Those viral pathogens in the incoming material can be quantified using advanced analytical methods. After wastewater treatment and disinfection by chlorination or UV light, the viruses are eliminated before the waste is discharged into the environment.

Noble and her team wanted to know whether SARS-CoV-2 virus shed could be quantified in wastewater and what trends might emerge after monitoring several wastewater treatment facilities over time.

Study methodology

First, the team needed to secure the participation of the wastewater treatment plants. After reaching out to multiple facilities across the state of North Carolina, they formed partnerships with local governments and utility operators in large and small communities in both rural and metropolitan areas. Ultimately 20 wastewater treatment plants were selected to be monitored.

Next, the team needed to define the study area. Specifically, they needed to identify the geographic limits each plant serves.

This is where WithersRavenel enters the picture.

Before he became the Chief Experience and Innovation Officer at WithersRavenel, Eddie Staley was a Professional Land Surveyor and Geographic Information Systems Professional. In 1997, Eddie was hired as the Project Manager for the development of NC OneMap. NC OneMap is a public collection of North Carolina maps, images, and geographic data, including water and sewer utility data.

“OneMap was a huge undertaking back in 1997, stretching the limits of GIS and the very young Internet,” Eddie recalls. “This was a time of dial-up modems, AutoCAD release 14, and websites were a novelty only around 300,000 in early 1997.”

At the time, not one utility in the more than 60 counties Eddie developed data for had any type of digital information for water or sewer. The project was a paper-to-digital transformation exercise on a scale that has not been repeated at the state level since, although the site did receive an update in 2004.

The original intent of the site was to support economic development, regionalization of utilities, and asset management funding gap analysis. NC OneMap data has been used for a multitude of statewide projects since its launch. For example, many of the utility funding projects WithersRavenel prepares grant applications for today including CDBG-I, SRF, and AIA use this data to verify age of infrastructure.

Noble’s team wanted to use NC OneMap for their study, and they reached out to Eddie for help in understanding how to leverage that resource. Eddie showed the team how to access the sewershed data for Raleigh and Cary, which was already available online.

Some of the other collaborating facilities the team had partnered with were not currently represented in NC OneMap, but they were able to provide key figures like sewer volumes and flow rates. Eddie and the WithersRavenel GIS Team were able to put these numbers into context by outlining their sewershed boundaries as well.

Once the team had a clear understanding of the study area, they could begin collecting wastewater samples, sending them to the university laboratories for quantitative analysis and sharing the data with epidemiologists who are tasked with tracking and interpreting their findings in relation to clinical data.

Study findings and the benefits of examining COVID-19 in wastewater

Similar to work conducted by her close collaborators, Noble’s team quickly confirmed that it was possible to detect and quantify SARS-CoV-2 virus shed in wastewater. At the same time, they and other researchers put quality assurance protocols in place to ensure that the viruses detected in the wastewater were not transmissible to the technicians analyzing the samples.

A principal benefit of examining wastewater is to provide a snapshot of the aggregate signal of COVID-19 in a community, rather than focusing on sampling individuals as clinical tests do. Wastewater-based analyses do not depend on the availability or accuracy of patient testing, and it is not skewed by which infected individuals choose to get tested. If the infected individual contributes their waste to a community system that is being analyzed, they will be evaluated as a contributor to the overall signal.

Because viral shedding can begin before an infected individual develops symptoms, and may occur in asymptomatic individuals, monitoring wastewater allows public works and public health officials to work hand-in-hand to identify potential virus hotspots, increase health surveillance, and ultimately increase public health service response.

Concerns about data security

Given the potential benefits of wastewater monitoring and the low risk of infection from taking samples, it is easy to wonder why the practice has not become more widespread, if not universal. The chief reason is data security.

In order for researchers to work backwards from a sample taken at a plant to the place and time an infection started, they need to know how long it takes for waste to travel from a given source to the plant. This calculation can be accomplished through a hydraulic model, which simulates the flow of waste through the sewer system.

Many local governments are reluctant to release information related to their sewer’s hydraulic model, however, because access to that information would open up the possibility of bad actors interfering with the system.

Noble’s team has worked with all of the plant operators and local governments in the study to protect the integrity of their hydraulic modeling data, including preventing it from being shared with anyone not directly involved in the project.

The team also understands that public perceptions of privacy are an important part of the discussion. They pointed out that it is not possible to link any of the samples to individuals or households.

Next steps for tracking COVID-19 in wastewater

At this time, the project is transitioning from the study phase to the results and action phase. The team is developing a communication process to share their findings.

The Centers for Disease Control and Prevention have provided funding to the State of North Carolina and 7 other states to do a pilot project of a more widespread sampling effort as part of a National Wastewater Surveillance System. In response, the team is developing more concrete and timely methodologies for taking, analyzing, interpreting, and reporting on samples in the upcoming pilot project.

The success of this project not only has implications for the continued fight against the COVID-19 pandemic, but also for other present and future epidemics. Others have used similar wastewater-based epidemiological approaches but for different reasons, such as to track prevalence of other epidemics (e.g., polio) and opioid use.

If these projects move forward, there may be interest in updating the maps available via NC OneMap throughout the state. If that is the case, WithersRavenel is ready to become a partner in the ongoing effort to find and fight the coronavirus as well as future epidemics.

This post was originally published on January 29, 2021, and was updated on March 15, 2021.