Uncovering Public Health Signals Through Environmental Engineering

A typical city of about 200,000 residents generates approximately 60 million liters of wastewater every day, from kitchen sinks, toilets, laundry rooms, and showers, all flowing into wastewater treatment plants. Such daily wastewater can be a source of critical scientific information. At the Butler Research Laboratory in the University of Massachusetts Amherst, graduate researcher Raphael Chukwuka Nnachi is transforming wastewater into a powerful tool for public health surveillance.  

Nnachi investigates the dynamics of community immunity against COVID-19 by measuring key biomarkers in sewage. By linking short-term and long-term immunity trends with infection rates, and identifying the immunity shift patterns with disease spreads, his work offers a powerful early-warning tool for assessing community health. Every flush goes towards his research to uncover when a community is vulnerable to infection or re-infection, thereby helping to protect communities and prevent future pandemics. 

Originally from Nigeria, Nnachi earned an undergraduate degree in Microbiology from Alex Ekwueme Federal University, Ndufu-Alike Ikwo. His academic excellence led to a role as a teaching and research assistant in his alma-mater, where he taught several courses and mentored many undergraduate students.  

In 2019, he was awarded the prestigious Commonwealth Shared Scholarship, funded by the UK government, to pursue graduate studies at Cranfield University. There, Nnachi and his graduate study supervisor, Professor Zhugen Yang, focused on Wastewater-Based Epidemiology (WBE) and development of point-of-use sensor devices for detecting microbial contamination in drinking water.  

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Nnachi analyzing samples in the laboratory

During the peak of the COVID-19 pandemic, as scientists searched for new diagnostic tools, increased community surveillance, and ways to slow down transmission, WBE became a point of focus. Researchers discovered that wastewater from different neighborhoods can reveal emerging infection hotspots early, sometimes days before clinical testing, guiding timely public health responses. This insight sparked Nnachi’s curiosity in this field.  

Nnachi wanted to continue his research in WBE and contacted Dr. Caitlyn Butler at UMass Amherst, drawn by their shared research focus in wastewater surveillance. Nnachi gained admission to the University’s PhD program in Civil and Environmental Engineering, with a concentration in Environmental and Water Resources Engineering. In his first year of PhD, he was awarded the prestigious and competitive Riccio College of Engineering Dean’s First Year Fellowship. 

Subsequently supported by funding from the Massachusetts Department of Public Health, he collects and processes wastewater samples three times a week from Amherst town wastewater treatment plant. These findings are then reported to the Massachusetts Department of Public Health’s SARS-CoV-2 Wastewater Surveillance Program to monitor the amount of SARS-CoV-2. Although these results cannot pinpoint individual cases, they provide critical early warnings, often detecting the virus in wastewater several days before the number of clinical cases increases.  

In Butler’s lab, Nnachi uses specialized techniques to detect two types of COVID-19 antibodies: IgA, which reflects short-term immunity, and IgG, which indicates a long-term immune response. These data reveal the presence, frequency, and concentration of viral antibodies, helping to identify areas with low, moderate, or high immunity signals. 

Looking ahead, Nnachi thinks about the future of his field: “One challenge that I and the WBE research community have recognized is moving beyond just identifying communities with infections already to pinpointing communities that are vulnerable to infections. If we could detect exactly which community is vulnerable to infection, we could communicate that to the health authorities to deliver timely, targeted interventions that could save thousands of lives.” 

Now in his third year as a PhD student, Nnachi’s impact extends beyond the laboratory. In the summer of 2025, he was selected to participate in the second series of a National Science Foundation (NSF) Ethical Sewer Research Workshop, joining experts to develop research guidelines and standards for the ethical application of wastewater surveillance. During the workshop, the group focused on developing standardized methods for data collection and analysis that balances public health needs with privacy concerns. The group’s efforts will soon culminate in a living ethics module for wastewater surveillance to guide future research. 

Nnachi’s research has also been recognized by the UMass Amherst Graduate School, which awarded him a competitive Predissertation Grant to support preliminary studies on wastewater-based epidemiology. He was also selected for the Graduate School’s STEM Leadership Fellowship, funded by the NSF. He has presented his research findings at major conferences in the United States and published five highly cited articles, one of which has since become one of Clarivate’s Institute for Scientific Information (ISI) highly-cited papers in 2025.

Written by Emefa Adawudu, PhD student in Nursing, as part of the Graduate School's Public Writing Fellows Program. 

“I have received many things from people. I have taken so much, and I want to balance it. I want to also be able to give back to the society I am from.”

Nnachi aspires to become a professor in the field of Environmental Engineering and hopes to mentor the next generation of researchers. He explained, “I want to be able to mentor other people. I have received many things from people. I have taken so much, and I want to balance it. I want to also be able to give back to the society I am from.”

Written by Emefa Adawudu, PhD student in Nursing, as part of the Graduate School's Public Writing Fellows Program.