For UMass Amherst environmental engineer Caitlyn Butler, research is most rewarding when she’s investigating an intriguing question that intersects with an important real-world need.
Over much of her career, she has applied her interest in microbial ecology and, in particular, biofilm systems—naturally forming collections of microorganisms, like the slimy film that grows on river rocks—to developing energy-efficient strategies for wastewater treatment. Shortly after the COVID-19 pandemic began in 2020, though, she pivoted to studying wastewater for epidemiological purposes. Over the past several years, her research group’s effort to track SARS-CoV-2 in wastewater has become an important tool in the university’s COVID-19 response protocol to keep the campus community safe and informed.
Butler first became interested in wastewater as an undergraduate at Smith College, where she devoted her senior project to the topic. Growing up in Northampton, Mass., she never envisioned attending a women’s college in her hometown, but Smith had a brand new engineering program—the first ever at a women’s college. Butler graduated in Smith’s first class of engineering majors and went on to earn a PhD in environmental engineering from the University of Notre Dame, where she delved deeper into topics in wastewater engineering. After a stint on the faculty at Arizona State University, she joined UMass Amherst’s College of Engineering in the Department of Civil and Environmental Engineering.
At UMass Amherst, Butler’s research group has explored how the natural behaviors of microbes in biofilms can be used to improve wastewater treatment systems. “While biofilms can be a nuisance when they grow on things like medical equipment or water filters, in wastewater treatment they can actually be exploited in interesting ways to maximize efficiency, recover energy, and reduce the environmental impact of treating wastewater,” she explained.
And then, in early spring 2020, the COVID-19 pandemic began and the world—including UMass research labs—shut down. Butler began hearing in the environmental engineering community about labs studying COVID-19 in wastewater, and realized she had the skills, knowledge, and equipment to help her community in this way.
“Being in these uncertain times, I thought about how I could use my skillset to help,” she recalled.
With seed grants from the UMass Amherst Institute for Applied Life Sciences, Butler’s research group began by establishing a protocol to accurately assess the presence of SARS-CoV-2 in wastewater from the UMass campus. Amherst’s wastewater system is ideally set up for this kind of research, as the campus’s wastewater comes to the plant in its own designated stream. After an initial validation phase to ensure the wastewater-based data correlated with clinical data, Butler’s research team scaled up its operation. It began capturing samples from over 35 catchment sites on campus three times a week using a composite sample strategy representing a 24-hour window within the sewer. The samples are tested at an on-campus lab, and the results reported to the university’s COVID Response Team.
“The university uses this as one dimension of data—along with clinical data and other information—in its decision making and communications to the campus community,” said Butler. The data is published on the university’s online COVID-19 dashboard to assist individuals in making informed decisions about their own behavior, and is also shared with the Town of Amherst.
I think there’s a lot to be learned from sewers in terms of disease dynamics.
Nearly two years on, these efforts continue on the UMass campus, and Butler’s group, in partnership with IALS Clinical Testing Center, also coordinates the collection of samples on other public campuses in the Commonwealth through a contract with the Massachusetts Department of Public Health. Undergraduate and graduate students make up a core part of her research team, assisting with everything from pulling sewer samples to separating viral fragments from wastewater in the lab to developing new protocols. “They’re the backbone of this operation,” she said.
Wastewater epidemiology is most valuable in indicating trends—that is, whether cases are on the rise, declining, or flat. As an emerging tool, there are still many open questions about its use. Butler pointed to one example of an important contribution her research team made to the literature: “We published a paper showing shedding rates per person per day, based on a study of an isolation residence in which all occupants were COVID positive. We found that there can be a huge individual variation in the amount of virus shed, such that one COVID-positive person may appear like 10 or even 100 in samples from small wastewater catchment areas,” said Butler. "Longer term, we hope to explore more questions around how to connect caseloads with concentrations observed in a sewer given the complex dynamics that can happen in a sewer shed.”
Butler has also been involved in developing innovative methods for wastewater sampling. She explained that wastewater-based epidemiology is meant to be an accessible, lower cost option for communities compared to clinical testing, yet the “autosampler” equipment traditionally used to collect samples is quite expensive. Through its research, Butler’s group determined tampons to be a less expensive, and even more sensitive, alternative for collecting wastewater samples to test.
Butler has received many prestigious honors, awards, and fellowships in recognition of her exceptional research and teaching. These include a highly competitive and prestigious National Science Foundation (NSF) CAREER Award; a Fulbright Scholar Fellowship at the University of Sheffield in England; Gates Foundation support to develop a unique “Green Latrine” for use in developing countries; and the Outstanding Teaching in Environmental Engineering and Science Award from the Association of Environmental Engineering and Science Professors (AEESP).
In the future, Butler hopes to apply what she’s learned about wastewater-based epidemiology to other disease targets, such as influenza or respiratory syncytial virus (RSV).
“I think there’s a lot to be learned from sewers in terms of disease dynamics,” she said.