There are many ways to test municipal wastewater for signs of the virus that causes COVID-19, but scientists in Houston have proven it to be the best yet.
A study led by environmental engineer Lauren Stadler from Rice University’s Brown School of Engineering with support from Houston City Department of Health and Baylor College of Medicine compared five processes used by labs across the country to collect samples and detect the virus in wastewater from six Houston Plants.
The process used by Rice and now Baylor, known as “electronegative filtration with bead beating,” was the most sensitive to the signs of the virus as well as the most cost-effective. .
The study appears in the journal Elsevier Water Research.
There is no routine test, according to the study, but all processes – including electronegative filtration by elution, ultrafiltration, precipitation and direct extraction – are partially efficient.
“The virus is very thin in wastewater, so we need a targeted method,” Stadler said in explaining the Rice process. “First, we add salt to the wastewater sample to enhance the virus to the electronegative filter. After filtration, we physically beat the filter with glass beads to release the virus into lysate. Even though this process may break up the virus, we will only find tiny fragments of its RNA genome to measure it. “
Founded in the spring of 2020, the Houston consortium was at the forefront of what became a national effort to detect the SARS-CoV-2 virus in wastewater. The approach quickly enabled the anticipated outbreak of COVID-19 and allowed health officials to investigate where necessary.
When we started experimenting, Baylor used a different approach. That allowed us to do a lot of head-to-head comparisons about which method should be used. And that led us to want a more complete evaluation of several methods commonly used to collect SARS-CoV-2 in wastewater by other organizations around the world. “
Lauren Stadler, Environmental Engineer, Brown School of Engineering, Rice University
“There is no one right way, but we wanted to make sure we consider other options,” she said. “Our recommendation and choice of final method was based on striking a balance between sensitivity, throughput and cost.
“The method we originally chose turned out to have the lowest detection rate, while also being relatively high throughput and cost-effective,” Stadler said. “Baylor moved over to the same collection method as a result, which gave us confidence that we were actually generating the best possible data for the city.”
Houston researchers hope the study will guide urban areas around the world that have, or are considering, their own wastewater test plants.
“A lot of cities are already doing this, and state programs are now appearing in Michigan, Wisconsin, North Carolina and a few more,” Stadler said. She noted that Houston labs are already looking for COVID mutations. “We are conducting research on ordering wastewater samples to detect highly diffuse changes circulating in the community,” Stadler said.
An advantage is that the study even took place, considering the workload for the laboratory of Stadler’s Rice and its peers at Baylor and the Houston Department of Health. Since they went up in mid-2020, the laboratories have analyzed hundreds of samples each week from the city’s 39 wastewater treatment plants. Since then, Houston has added test points at dozens of nursing homes, schools and other emergency places.
“The city plans to expand the number of stations to receive zip code level information, and we are working with them to analyze that data,” Stadler said. “Someday, it could be a tool to view a panel of viruses, not just this one. “
LaTurner, ZW, et al. (2021) Evaluating the recovery, cost, and application of different collection methods for SARS-CoV-2 wastewater-based epidemiology. Water Research. doi.org/10.1016/j.watres.2021.117043.