Reducing human exposure to per- and polyfluoroalkyl substances (PFAS), also known as “forever chemicals,” is a significant societal challenge. In the search for possible solutions, a group of researchers in WPI’s Department of Chemical Engineering has developed a process for wastewater treatment plants that not only shows promise in removing PFAS from sewage but also may ultimately generate renewable fuel while potentially reducing the amount of carbon emissions produced by these plants.
Demonstrating WPI’s commitment to developing impactful innovations, the researchers are collaborating with academic, industry, and government partners in hopes of bringing their technological approach from the lab into communities facing the daunting challenge of remediating PFAS contamination.
“PFAS are insidious. They can slowly accumulate and contribute to health risks. We’re trying to reduce those risk factors,” said Michael Timko, professor in the Department of Chemical Engineering.
PFAS often show up in wastewater, and, if they are not broken down, they can re-enter the environment through emissions as both runoff water and solid waste
The timing of WPI’s work is important: Government, health, and community leaders are increasingly pushing for reductions in PFAS in the environment. PFAS are human-made chemicals that have been used for decades in the production of goods such as nonstick cookware, water-resistant clothes, and firefighting foam used at airports and military bases. Once in the environment, they are hard to break down and the widespread use of products with PFAS has resulted in the chemicals being found in soil, water, crops, livestock, and the human food chain.
When someone drinks water or eats food with PFAS in it, the chemicals can build up inside the body. According to the federal government’s Agency for Toxic Substances and Disease Registry, evidence suggests associations between increased exposure to specific PFAS and health effects including certain cancers, higher cholesterol, and higher levels of enzymes that can signal liver damage.
PFAS often show up in wastewater, and, if they are not broken down, they can re-enter the environment through emissions as both runoff water and solid waste. But, it can be challenging, costly, and energy-intensive for municipalities and water systems to remove PFAS from wastewater and its associated by-products. That’s where the team from WPI comes in.
“As we aim to reduce the presence of PFAS and people’s exposure to health risks, we also want to reduce the carbon footprint of wastewater treatment,” said Timko. “There’s enough energy in the incoming waste stream to power wastewater treatment facilities, and we believe these plants can be carbon-neutral or even energy-producing.”
The team, which is led by Timko, built upon a core advanced technology known as hydrothermal liquefaction (HTL) to create a process called radical initiated hydrothermal liquefaction (RI-HTL). The process works by heating up wastewater treatment–generated sewage sludge in a reactor that serves as a pressure cooker. A “radical,” hydrogen peroxide, is put into the mixture to help speed up the reactions that break down the bonds holding PFAS together. Ultimately, RI-HTL generates solid waste, processed water, gas, and biocrude oil.
Initial tests found that heating sludge for 10 minutes at roughly 570 degrees Fahrenheit in the WPI-developed process removed 99 percent of PFAS from the processed water, 98 percent from solid waste, and 89 percent from the oil. Techniques for further processing the oil can remove additional PFAS and upgrade it into transportation fuel, such as diesel or aviation fuel.
The testing also found RI-HTL increases the amount of biocrude generated, offering a 60 percent yield, compared to a 40 percent yield from HTL. Additionally, because WPI’s RI-HTL works with sewage sludge in a “wet” state, it bypasses the energy-intensive steps of drying and incinerating sludge used by some treatment facilities.
Hoping to bring this technology to the market, Timko and his team worked with WPI’s Office of Technology Innovation and Entrepreneurship to seek a patent on the technology and license it to River Otter Renewables. Timko co-founded the Massachusetts-based company in 2023 with CEO Amelia Thomas.
“River Otter hopes to use this technology to save wastewater treatment facilities money by reducing solid waste heading to incinerators or landfills and by reducing their use of natural gas, electricity, and chemical additives for other methods of sludge disposal,” said Thomas.
The Environmental Protection Agency helped advance the research in 2023 when it awarded Small Business Innovation Research funding to River Otter Renewables for testing and design work. Timko and Thomas hope to build a larger pilot-scale reactor, test more sludge samples, conduct analysis on the gas generated through RI-HTL for PFAS and hydrocarbons, and investigate other potential radical initiators or catalysts.
“There isn't going to be a one-shot solution to the PFAS problem. There will be many different solutions in different areas,” said Timko. “We think we have a sweet spot with a technology that could benefit wastewater treatment. It has very complex and rich chemical engineering science behind it that I hope to further understand through testing so we can help reverse some of the damage PFAS have been silently causing for decades.”
