Let nothing go to waste
Houston researchers have great success tracking COVID through wastewater collection
Lauren Stadler’s environmental engineering students always pose the same question at the beginning of a semester: “What happens to water in the toilet after you flush?”
Historically, humans have worked to quickly dispose of and eradicate their own waste, which can carry diseases.
But an area’s waste creates a snapshot of who is there and what they’ve been exposed to, said Stadler, a wastewater engineer and environmental microbiologist at Rice University. She’s working with the Houston Health Department and Baylor College of Medicine’s TAILOR program to find SARS-CoV-2 in the city’s wastewater.
Stadler’s hunt has revealed variants in particular areas, heightening the city’s urgency to procure resources — COVID tests, informational meetings, advertising and now vaccine sites — in an effort to quash them before they proliferate.
“The beauty and challenge of wastewater is that it represents a pool of sample — we’ll never get an individual person’s SARS-CoV-2 strain, but a mixture of everyone in that population,” Stadler said. “We can find a population level of emergence of mutations that might be unique to Houston.”
The city of Houston began studying wastewater for viruses last spring, said Loren Hopkins, chief environmental officer at the Houston Health Department. A year in, it’s a streamlined process the local government will continue after the pandemic ends. When the virus started spreading through Houston, the health department was tasked with COVID-19 testing, and at the time, it was relying solely on test positivity rates to pinpoint where the virus was proliferating.
But the city needed more data to intervene in affected communities, Hopkins said. So it turned to scientists at Rice and Baylor’s TAILOR research program for their wastewater expertise.
“We decided we were going to try it, and if it didn’t look promising, we wouldn’t pursue it any further,” Hopkins said. “As the summer went on, we had this amazing team. It wasn’t just sampling — there’s a lot of labor that goes into it. It was amazingly helpful to us.”
Variant tracking has become an important part of the wastewater-analysis process, Stadler said.
In February, the city and its research partners began seeing a quick emergence of the B.1.1.7 variant, which is now the dominant variant in the area. According to the Centers for Disease Control and Prevention, nearly 21,000 cases of the B.1.1.7 variant have been detected nationwide.
Now that the team has gathered data and built a sustainable process, Stadler said it is using this information to forecast future pandemics. “Taking wastewater data, you can predict positivity rates and forecast infection burdens — it has this predictive power, essentially. It’ll be very important to identify areas in the city experiencing increases in infection, and we can direct resources.”
The wastewater-analysis team works with public works employees to collect weekly samples from nearly 200 sites across the city.
“I think they see this as a monitoring tool beyond the pandemic, and we see it as well,” Stadler said. “Hopefully, when SARS-CoV-2 is behind us, we will be able to
monitor for an endemic virus, like flu. We can use wastewater monitoring to look for other viruses, bacterial pathogens and other pathogens of concern.”
Pre-pandemic, Baylor’s TAILOR program’s main focus was locating phages — viruses that infect and kill bacteria — in wastewater that can later be used as a resource for doctors who have patients with antibiotic-resistant infections. The partnership among TAILOR, Rice and the health department has helped the phagegathering project move forward as well.
In one year, the city has expanded the project to 39 water-treatment facilities and 51 schools in high-positivity areas. Wastewatercollection samplers were
placed in sewers near nursing homes, jails and shelters for people experiencing homelessness. Samplers are also placed in 60 lift stations, where wastewater and sewage material is pumped closer to the surface.
Lift stations are responsible for pumping wastewater or sewage material from a lower elevation to a higher elevation. On the other hand, a pump station is designed to raise water, not sewage or wastewater, to a higher elevation.
Before this project, the three-person TAILOR team collected samples from one or two sites in the city. Using a dunk-a-bucket method, in which team members gather samples by literally dipping a bucket beneath the surface, they put a container in a wastewater-collection site and took whatever was found, and were able to test a variety of bacteria phages for analysis. Now, the TAILOR team has access to wastewater samples from all the sites, which has boosted its phage-finding efforts.
Stadler believes a silver lining to this pandemic has been the partnership between the universities and the city, as well as warpspeed advancements in wastewater research. Cities will be better prepared for future pandemics because of what they learned this first year, she said.
“Simultaneous science informs action in real time, and that advances research,” Stadler said. “This is the most fast-paced project I’ve ever worked on. And it’s the most impactful action in public health.”