Utility officials in Maine and elsewhere around the country are developing first-of-their-kind plans to eliminate toxic PFAS “forever chemicals” from sewage sludge spread as fertilizer on farmland.
Success would address a growing agricultural crisis and reshape how the nation handles its waste – the dangerous chemicals are thought to be contaminating all sludge at high levels, and poisoning food and water on around 20m acres (8m hectares) of farmland across the US.
But the technology that destroys PFAS remains unproven, especially in sludge, officials with the Portland Water District (PWD) of Maine acknowledge, and the utility is taking other steps to more efficiently dispose of the substance in the meantime.
“The safe disposal of [sewage sludge] is critical to safeguarding the environment and protecting public health,” said the PWD director of wastewater services, Scott Firmin. “We are leaving no stone unturned as we seek innovative and economical solutions to tackling the nationwide threat of PFAS.”
Public health advocates say they are skeptical the technology will be ready to scale to industrial use anytime soon, and point to what they characterize as less costly and more environmentally friendly alternatives.
“We would need assurance that it is destroying all PFAS,” said Sarah Woodbury, director of advocacy for Defend Our Health Maine, an environmental non-profit. “If it works – great, we’re 100% on board, but we’re just not convinced that this is a solution.”
PFAS are a class of about 15,000 chemicals often used to make products resistant to water, stains and heat. The compounds are linked at low levels of exposure to cancer, thyroid disease, kidney dysfunction, birth defects, autoimmune disease and other serious health problems. They are called “forever chemicals” because they do not naturally degrade and are virtually indestructible.
Sewage sludge is a byproduct of the water treatment process that’s left over when water is separated from human and industrial waste discharged into the nation’s sewer systems. Sludge used to be dumped in the ocean before that created vast dead zones, so the EPA about 30 years ago approved it for use as a fertilizer because it contains high levels of nutrients that help plants grow. Industry calls sludge that has been lightly treated to eliminate pathogens “biosolids”.
But sludge also contains every chemical flushed into sewer systems by residential plumbing or industry. Because PFAS are so widely used in industrial processes and added to thousands of consumer products, they are found in the sewage system at high levels. The Sierra Club has characterized sludge as “the most pollutant-rich manmade substance on Earth”.
The biosolid treatment process does not remove PFAS or other chemicals, and regulators in Michigan and Maine have found widespread contamination in the soil of every field they have checked where sludge was spread. The chemicals have also been found in crops, beef, water and farmers’ blood, and both states have ordered tainted farms to close.
Maine last year became the first state to ban the practice as the scale of the problem became clear. But the ban created a new challenge – disposal. One state-owned landfill can accept the substance, and the company that manages the facility, Casella, says sludge must be mixed with bulking material in a five-to-one ratio to stabilize it. That presents logistical challenges and some Maine sludge is now sent out of state at an added cost to ratepayers.
The PWD, New Hampshire department of environmental services and others are considering destroying PFAS and using charred sludge as a fertilizer or for some other use. The plan comes as urgency over dealing with highly persistent chemicals that remain in the environment, like PFAS or dioxin grows, but no techniques have been effectively scaled up.
Portland is developing a facility that could eventually use technology such as pyrolysis and gasification to “safely and economically reduce or eliminate PFAS from biosolids”, which is typically done at high heats.
First, however, the PWD plans to de-water its sludge and treat it with drying technology that is available and proven, and would reduce the number of truckloads the utility sends to the landfill each week from 16 to five.
“That’s a significant amount of material to handle, and in the near term that will help landfills,” Firmin said.
The remaining dried sludge could eventually be treated with gasification or pyrolysis to destroy its PFAS.
But the definition of how technologies “destroy” PFAS is essential to determining whether it is safe, said Laura Orlando, a sewage system engineer with Boston University who has worked on sludge disposal and PFAS issues for several decades.
Some studies that claim PFAS can be destroyed only address PFOS or PFOA, which are two of the most commonly found PFAS, but represent only two out of 15,000 compounds.
Others claim to have destroyed PFAS compounds but have only broken a compound into chemicals. A hypothetical PFOS compound that is broken into multiple pieces is still dangerous because it remains toxic, persistent and bioaccumulative, public health advocates say.
While studies have found the PFAS can be eliminated in laboratory settings, real world success is in question, and Orlando and Scott both noted pyrolysis facilities that have failed to provide satisfactory results.
The high heat processes utilized to destroy PFAS in sludge also create a “chemistry set” in which other dangerous substances, such as perchlorate or chromium hexavalent, are developed, Orlando said.
“It’s a nightmare and that’s why you don’t see these facilities all over the place,” she added.
Moreover, it’s unclear if the residue that would remain after the process would be safe to apply to land, and Orlando raised questions about the process creating air pollution that is largely not regulated in the US.
However, the PWD plans to remain involved with the development of the technology and regulations so the utility can be at the cutting edge if the processes can be scaled up to industrial use, Firmin said.
“We’re trying to move in a direction that ultimately gets us to the best solution, but we’re recognizing that it might not … all happen at once,” he said.
