Researchers at the University of Texas at San Antonio have identified fragments of the coronavirus in wastewater from a sewage treatment plant that serves Converse and Live Oak.

Researchers led by Vikram Kapoor, an assistant professor in UTSA’s department of civil and environmental engineering, are five months into an eight-month sampling effort of the Salitrillo Wastewater Treatment Plant operated by the San Antonio River Authority. The plant treats sewage generated by 17,000 connections in northeastern Bexar County.

In an interview Wednesday, Kapoor said researchers have received weekly samples from the raw sewage flowing into the Salatrillo plant and tested it for fragments of the virus’s RNA. They found concentrations of the virus fluctuating from 100 to 100,000 RNA copies per liter. He stressed that there’s no evidence that people can contract the virus directly via wastewater itself.

Kapoor said the wastewater showed the highest concentrations of viral RNA so far in mid- to late July, which correlated with a spike in confirmed coronavirus cases in Bexar County. On Monday, Kapoor released a graph showing concentrations of two genes specific to the coronavirus and how they fluctuated over the past several months.

A graph of two genes specific to the SARS-CoV-2 virus found in wastewater from the Salatrillo wastewater treatment plant. The concentration of virus in the wastewater roughly correlates to Bexar County coronavirus cases, as reported by the San Antonio Metropolitan Health District.
A graph of two genes specific to the SARS-CoV-2 virus found in wastewater from the Salatrillo wastewater treatment plant. The concentration of virus in the wastewater roughly correlates to Bexar County coronavirus cases, as reported by the San Antonio Metropolitan Health District. Credit: Courtesy: Vikram Kapoor, University of Texas at San Antonio

Kapoor said that while sewage sampling will never replace clinical testing, it could be a cost-effective early warning system for outbreaks in isolated communities or for sudden spikes in transmission. It can also detect viral material shed from people who don’t show symptoms.

“Obviously, clinical testing is important and that’s the first way to go about this, but this is a complementary approach, which could essentially give you information in a lesser amount of time and money,” he said.

He added that it’s not yet possible to use the virus’s concentration in wastewater to determine how many people upstream have contracted the virus.

Kapoor’s team received $160,000 in federal coronavirus relief funding for the project via the Bexar County Health Collaborative and San Antonio Metropolitan Health District.

Researchers recently began receiving samples from the River Authority’s Martinez treatment plant as well, Kapoor said. Kapoor said he also hopes to expand the research to include San Antonio Water System plants.

SAWS officials did not respond to a question about whether the utility has conducted coronavirus sampling at its facilities.

Brendan Gibbons

Brendan Gibbons

Brendan Gibbons is the San Antonio Report's environment and energy reporter.