The value of testing waste water
April 21, 2021
Testing water on the back end is helping Virginia Tech get out in front of potential COVID-19 outbreaks.
Each hour, samples of sewage are automatically drawn from 16 manhole sites across the university’s Blacksburg campus. Twice a week, those samples are collected, tested for traces of the virus, and used to generate a weekly report for the university’s Incident Management Team.
“The wastewater team let me know every Monday night where their sampling has indicated a signal and then the university can adjust the testing based on that information,” said Michael Mulhare, Virginia Tech’s assistant vice president for emergency management. “It helps to optimize the testing program, applying available resources to manage risk. The information provided by the team informs prevalence testing providing an opportunity to focus testing to identify potential emerging areas of concern."
Led by civil and environmental engineering professors Amy Pruden and Peter Vikesland, as well as Ph.D. candidate Ayella Maile-Moskowitz, a team of researchers began fine tuning the process of testing Virginia Tech’s waste water last June. Throughout the summer, they worked with the Molecular Diagnostics Laboratory at the Fralin Biomedical Research Institute at VTC to ensure accurately testing such samples was possible.
“Sewage is a very messy kind of sample to work with so it was important to test all that out before getting it up and running on campus,” Pruden said.
In September, the group began testing samples gathered individually via “grab sampling” because of a scarcity of the equipment. An investment of $200,000 from Virginia Tech's Office of the Vice President for Research and Innovation and the Department of Civil and Environmental Engineering helped change that.
“Grab sampling isn’t that sophisticated, it’s basically a stick and a bucket and a one-time sampling point,” Pruden said. “But you might miss something important with grab sampling- that’s why it was really important to get the investment from the university for these composite samplers. They pump up a sample every hour, on the hour, so you get an integrated collection of samples over 24 hours.”
Once filtered, the samples are transported to Roanoke where Carla Finkielstein, director of the Molecular Diagnostics Laboratory and associate professor with the Fralin Biomedical Research Institute and the Department of Biological Sciences, tests them for evidence of the virus.
“The whole idea is conceptually very simple,” Finkielstein said. “The idea is to identify the virus before spreading. One of the most difficult things is identifying those cases that are pre-symptomatic and asymptomatic. By doing this kind of sewage epidemiology, you’re getting a snapshot of what is going on in the population that doesn’t show any symptoms of the disease. You can detect the virus before anybody has any symptoms.”
Pruden said the samples are then shipped back to Blacksburg where further research is being conducted in an attempt to identify specific variants of the virus and to further quantify virus numbers and relate them to measurements of other constituents in the sewage.
To better understand and further analyze the test results, the group is working with a team of public health researchers in Virginia-Maryland College of Veterinary Medicine.
“What does the number [from the results] actually mean?” said Alasdair Cohen, an assistant professor of Environment Epidemiology who is leading the efforts to refine results comparisons across sites and to link numbers of virus measured in sewage to the number of individuals shedding the virus. “What does it mean with respect to COVID cases and what does it mean for COVID cases a week from now?”
Cohen said answering those questions hinges on understanding how many people contributed to the samples and how a soon a signal shows up in relation to people subsequently testing positive for the virus. For the first issue, estimating specific building’s occupancy levels, as well as their waste water flow is key. For the second, the group is working to study older samples from buildings where positives cases are known to have later occurred.
“Working backwards, we can use that information as a proxy to help look at future samples and forecast what we might see from other buildings in the near future,” Cohen said.
The complex work involves cleaning and merging a large number of different datasets, much of which is being done by Ph.D candidate Chris Grubb. And though not completely honed in just yet, Cohen said he is happy the team’s work thus far is helping assist the IMT in their decision making.
“We’re doing great with testing, but we have a relatively limited number of testing resources, and if this can help us better understand how to best allocate them, then great,” he said.
Long term, Cohen believes the lessons and practices learned during this period could have a great impact on taking care of the Virginia Tech community in the future.
“COVID in a way has been an opportunity to set up a waste water surveillance system that we think will have a lot of benefits on the other side of COVID as well, especially in terms of emerging pathogens,” Cohen said. “There’s lots of potential to monitor the overall health of campus populations.”
Written by Travis Williams