Sampling Truckee Meadows wastewater for the SARS-CoV-2 virus found a very clear upward spike approximately seven days before the spike appeared in the community in the form of people testing positive for the virus, according to a study conducted by the University of Nevada, Reno and community partners.
“The latest data shows very low to non-detect viral levels in wastewater suggesting a consistent reduction in COVID-19 prevalence in our community,” Krishna Pagilla, an environmental engineering professor at the University and leader of the study, said.
Sampling and testing were conducted at the three water reclamation facilities and at 12 sewer sites in the region beginning in April 2020.
“The data we collected from the many sites shows that the monitoring reflects what’s happening in the community,” Pagilla said. “It clearly reflects the extent of the disease as it was determined by human testing, so it is a good leading indicator of what’s happening in the community.”
He said that by doing this type of wastewater monitoring, tracking the virus can be done without interrupting people’s lives, and it includes asymptomatic people who may not go in for testing. Coupled with the human testing, this gives health officials another tool in development of management actions to deal with the pandemic in the region
“And it’s predictive for seven days ahead, telling us the trend in new positive cases we’ll see in the community in that timeframe,” Pagilla said. “It’s predictive because people don’t get tested until they have symptoms, but our marker concentrations are real time – as soon as the virus is discharged into the wastewater.”
Virus on the increase or decrease?
The data indicates whether COVID-19 is increasing or decreasing in the community.
“Using the monitoring samples, we can’t separate out just the vaccine effect, but overall if the pandemic is decreasing and the number of cases is going down – that we are able to clearly see through wastewater-based monitoring,” Pagilla said. “So, by doing more frequent monitoring we can really see whether the pandemic is going away or if a resurgence is happening. Now we are in position to do that.”
Pagilla is also the chair of the Department of Civil and Environmental Engineering and director of the Nevada Water Innovation Institute based at the University, which includes regional agency partners. In this ongoing study, the group began monitoring the Truckee Meadows wastewater at the Truckee Meadows Water Reclamation Facility in April 2020 to determine the level of COVID-19 in the community. The Truckee Meadows Water Reclamation Facility receives and treats wastewater from the majority of the Truckee Meadows.
In addition, from August through December, the group collected samples from 12 community locations. They expanded the sampling and survey to collection systems of the region to identify hot spots in the community.
“Looking for prevalence of COVID in the wastewater system, the environmental surveillance of wastewater, was funded by the cities of Sparks and Reno and Washoe County, using CARES Act funding,” Sparks Assistant City Manager John Martini said. “It was a regional effort to get the data, and the results are remarkable. We can see the amount of genetic material in wastewater rise as we hit the spike in October, November and into January; it tracked very well with testing results on people in our communities.”
Another project goal was to determine what happened to the virus as it passed through the treatment plant.
“The majority of wastewater in the community comes through the Truckee Meadows Water Reclamation Facility,” TMWRF Manager Michael Drinkwater said. “So, testing the wastewater is a good leading indicator of what’s happening in the community.
“We looked at the entire treatment process, which included the influent and effluent. The virus was clearly detected when coming into the plant, but not detected in the outgoing, so we can say definitively that the virus does not survive the wastewater plant and the water going back to the Truckee River is free of the virus.”
About 20 people from the University worked on the monitoring. They sampled each of the 12 sites, all in one day, on a weekly basis. Pagilla said it takes many resources to conduct the sewer monitoring.
“We had students and faculty working weekends, Thanksgiving and Christmas to collect samples,” Pagilla said. “It was a complicated collection procedure, using a long telescopic handle to capture the sample. The team took multiple samples and measurements on-site before bringing them back to the lab for analysis. The samples were transported on ice within two hours of collection to the University’s biomolecular engineering laboratory.”
The University crew had tremendous support from the agencies throughout the process.
“City and county staff helped with safety and traffic control at the collection sites,” Pagilla said. “There was also a two-member crew at the sites that built a safe area around the sewer access hole and helped with proper protocols for safety.”
The University team included co-authors on the study, Lin Li, a post-doctoral scholar in Pagilla’s research group, Laura Haak, and Niloufar Gharoon, a doctoral candidate under Pagilla.
Li is an expert in biomolecular testing and has developed the method to measure the viral signatures (an inactive RNA fragment of the SARS-CoV-2 virus) of COVID-19, which allows them to determine the presence of COVID-19 in the community, using the existing qPCR system (a technology used to measure DNA) in the lab.
“Since the pandemic began, we have developed in-house capability at the University to do this study,” Pagilla said. “And not just for COVID. We are now able to apply our knowledge, experience and resources to other substances in wastewater, to do further research related to wastewater and community health.”
This field of study is known as Wastewater Based Epidemiology and is being looked into by many cities around the world to determine COVID-19 prevalence in the absence of extensive clinical testing of humans. The purpose of this future work is to develop predictive tools that can complement clinical testing and other human testing data in assessing the prevalence of COVID-19 in the community.
“Environmental observations of wastewater is not new, it’s been around for a while,” Martini said. “But what is new is that we now have the ability to do it at our university. Having this tool in the toolbox up at the University will help this community for the next pandemic, to understand it and to find more efficient and better ways to manage a future pandemic.”
Monitoring of sewage or other environmental media (air, soil and water) has been an important method to determine community prevalence of disease due to disease-causing pathogens by measuring certain molecular markers of their DNA/RNA and is known as environmental surveillance.
“While TMWRF has been treating wastewater for the community since 1966, being part of a proactive effort to improve our understanding of public health is new to us,” Drinkwater said. “We are very happy to be able to contribute to this effort in addressing the COVID-19 pandemic.”
While continuing on a limited scale, sampling duration could last throughout the COVID-19 pandemic and is likely to continue for at least one year. Sample sites at each plant will include raw sewage and the finished effluent.
The project work was supported by faculty, staff and students from multiple research groups of the University. Staff from the City of Reno, City of Sparks, Washoe County and contractors provided additional field sampling support and personal safety protective measures. Technical support was provided by Washoe County Health District (Health Statistical Data) and Truckee Meadows Regional Planning Agency (GIS Support).