Wastewater treatment plants from municipalities and industrial sites will sometimes spread the sludge produce onto farm fields.
It’s long been seen as a good way to dispose of the sludge while also providing fertilizer to farmers.
In 2022, approximately 56% of sewage sludge generated by these publicly owned treatment works was land applied, 24% was landfilled, 3% was disposed of in a sewage sludge monofill, 16% was incinerated, and 1% was disposed of using another method, according to the EPA.
A draft report from the EPA found that it doesn’t take much of PFAS chemicals in that sludge to have an impact on human health and the environment.
“In many people's minds, this is the confirming analysis for something that they suspected for many years,” said Jim Bauman.
Bauman spent 40 years working on water quality issues for the Wisconsin Department of Natural Resources. Even in retirement, he’s kept up to date on PFAS-related developments.
Earlier this month, the U.S. Environmental Protection Agency released a draft report on Sewage Sludge Risk Assessment for PFOA and PFOS , two of the most studied PFAS chemicals.
PFAS are a group of manmade chemicals used in a variety of products. They’ve been tied to adverse health effects.
While there’s been a lot of focus on PFAS in drinking water, this report focused on PFAS in wastewater or sewage sludge that’s spread on agricultural fields as fertilizer.
Bauman says for him the most surprising thing to come out of the report was how little of these chemicals it takes to have an impact.
“They're talking about levels just above detection levels and quite a bit lower than what states such as Wisconsin have used in their interim strategies,” said Bauman.
The Wisconsin DNR’s interim strategy requires action when there are combined PFOA and PFOS levels above 20 parts per billion, but still allows for land spreading up to 150 parts per billion.
The EPA found that there may be human health risks exceeding the EPA’s acceptable thresholds for some modeled scenarios when land-applying sewage sludge that contains 1 part per billion of PFOA or PFOS.
“We should keep in mind that what we are talking about is not the entire food system, not each and every farm. We are talking about a fraction, hopefully small fraction, of the farms in the state,” said Bauman. “But we need to identify which treatment plants have high PFAS and which farms are receiving the high PFAS, and then address those concerns.”
Bauman told WXPR there are a couple of things he’d like to see Wisconsin do in light of this EPA report.
They include:
- Review current interim strategy for biosolid spreading.
- Sample biosolids from all municipal and industrial wastewater treatment plants.
- Find sites where biosolids have been spread in the past when PFAS concentrations were higher.
- Create an education program aimed at farmers.
The last point was one of the main focuses of the EPA report. As these biosolids are spread on their land, they’re the ones to most likely have the greatest health impact.
The EPA report modeled scenarios of PFAS contamination. It found the greatest risk is to those who primarily consume product on or near property where there has been land spreading of sewage sludge containing PFAS.
It’s possible they’re ingesting PFAS through their drinking water, drinking milk from pasture-raised cows, eating fish from a lake impacted by runoff, and eating beef or eggs from majority pasture-raised hens or cattle where the pasture has received impacted sewage sludge.
The report states: “The EPA did not estimate risk associated with occasionally consuming products impacted by land application of contaminated sewage sludge nor foods that come from a variety of sources.”
If farmers are concerned about PFAS chemicals in the biosolids that have been spread on their land, the EPA recommends contacting your state environmental agency or county government.
Bauman also pointed out that the two PFAS chemicals in the study, PFOA and PFOS, have been phased out of industrial use.
“We are finding these two PFAS that are of very high concern being discharged, even though they haven't been used for 6, 8, 10, 15 years in many locations. They just stick to many things, and they release off of pipes very slowly,” said Bauman.
The Wisconsin DNR has been looking into sludge spreading as a possible cause of the PFAS contamination in private wells in the Town of Stella in Oneida County. WXPR requested an update on that situation. We did not hear back before publication.
The EPA is accepting written comments from the public on the draft risk assessment now through March 17.