Sources of PFAS in the Environment (Source: U.S. Environmental Protection Agency)
By John Henkelman
As Sanford evaluates the proposed Aries biosolids project, our community sits at the center of a national debate regarding some of the most persistent synthetic chemicals ever created. To understand the stakes, we must examine the nature of per- and polyfluoroalkyl substances (PFAS) and the evolving science of wastewater management.
What are forever chemicals?
PFAS include more than 12,000 synthetic chemicals used since the mid-1900s to make products resistant to water, heat, and stains. They are found in non-stick cookware, fast-food packaging, and specialized firefighting foams.
At a molecular level, PFAS compounds feature a “head” and a “tail.” The heads consist of polar, water-loving groups. These attach to a non-polar, water-repelling tails built on a carbon backbone. Unlike typical carbon-based molecules where carbon binds to hydrogen, PFAS binds carbon to fluorine. Fluorine is an extremely reactive element and forms one of the strongest bonds in organic chemistry with carbon. This bond makes PFAS highly resistant to natural biodegradation.
Consequently, they do not disappear; they accumulate in the environment and the human body.
The tail and head structure of PFOS and PFOA molecules (Source: ITRC)
Long-chain vs. short-chain PFAS
Scientists categorize PFAS by the length of their carbon tail:
- Long-chain PFAS contain seven or more fluorinated carbons. These are highly toxic and bioaccumulate significantly in plants and animals.
- Short-chain PFAS, often used as alternatives, contain four to six carbons. While they may stay in the body for a shorter duration, they are more mobile in water and harder to filter out using standard carbon filters.
The risks of PFAS to our health
The polar head is the part of the molecule that interacts with the environment, allowing it to bind to proteins in living organisms, travel in blood, and migrate through groundwater. Because they concentrate at the interface between different boundaries (such as water and soil), they are extremely difficult to manage in our drinking water.
Exposure to PFAS is linked to compromised immune systems, high cholesterol, and increased risks of kidney and testicular cancers. Because these chemicals are harmful even at extremely small parts-per-trillion levels (think one drop in an Olympic swimming pool), they have triggered a wave of new national regulations.
The role of wastewater and biosolids
Municipal wastewater plants do not create PFAS; they are passive receivers. These substances enter sewers through industrial discharges, household products, and landfill leachate. Because conventional treatment cannot break the carbon-fluorine bond, the chemicals either remain in the treated water or concentrate in biosolids – the nutrient-rich organic solids left over after treatment.
Historically, biosolids (sludge) were recycled as agricultural fertilizer. Maine led the nation by becoming the first state to ban the land application of biosolids to prevent PFAS from leaching into the environment and our food. While this protects public health, it leaves communities like Sanford searching for new ways to manage thousands of tons of annual waste. Currently Sanford sends its dewatered biosolids to landfills in Hartland, Maine, and Québec.
Future for PFAS removal
Current practices involve sending biosolids to specialized landfills. Waste Management is finishing a facility in Norridgewock capable of processing 200 tons of biosolids a day (83% of state generation) and is planned to open later this year.
Communities are exploring other potential technologies:
- Thermal drying and anaerobic digestion is being explored by the Portland Water District. Similar projects have seen successful implementation in several major North American cities.
- Supercritical water oxidation is being explored by York Sewer District using high pressure and heat to “burn” organic matter in water. While technologically advanced, it is currently only limited to smaller-scale pilot programs.
- The Aries proposal utilizes pyrolysis and gasification. This technology uses high temperatures in a low-oxygen environment to burn biosolids into biochar. Unlike other technologies, Aries is proposing accepting other municipalities’ biosolids from across New England.
Apart from landfilling, these are emerging technologies that have yet to be proven in Maine and must pass regulatory and community scrutiny. As Sanford leaders and citizens evaluate the Aries project, the central questions are: Is Sanford the right location for a large-scale commercial operation? Is Aries the right company for Sanford? Should we be considering smaller solutions that manage Sanford’s biosolids before we consider out-of-state processing?
Learn more about PFAS and emerging solutions: https://science.osti.gov/-/media/sbir/pdf/Application_Resources/2023/CPE-PFAS-Final-Report.pdf
John Henkelman is an adjunct professor of environmental studies at the University of New England. He has over a decade of experience as an analytical development scientist.
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