Concern about PFAS in biosolids led to a ban on land application in Maine enacted in 2022. That sent municipalities and clean-water agencies scrambling to find outlets for the material.
Now a U.S. EPA Draft PFAS Sewage Sludge Risk Assessment has triggered worries about the public reaction to land-applied biosolids. As this document gains attention and moves from the draft stage toward final adoption, will the public’s concerns about health effects lead regulators and legislators to enact crippling restrictions on beneficial reuse programs?
And if that happens, what will be the fate of biosolids produced at thousands of clean-water plants across the nation? Management alternatives — incineration and landfilling — are already limited, and where available are far more expensive than application to cropland. And processes to remove PFAS are also costly and in some cases unproven.
Significantly, the EPA concluded in its draft that risk estimates “exceed the agency’s acceptable human health risk thresholds for some pasture farm, food crop farm, and reclamation scenarios when assuming that the land-applied (biosolids) contains 1 part per billion of PFOA or PFOS.”
Among entities looking at the issue is Carollo Engineers, a water engineering consulting firm based in Walnut Creek, California. The company recommends that communities and utilities start planning now to deal with the potential fallout from the risk assessment.
Rashi Gupta, wastewater practice director, observed, “The EPA’s assessment has potential to reshape how utilities approach biosolids management. Understanding these changes early will be crucial if utilities are to develop cost-effective, sustainable solutions.”
In particular, Carollo suggests utilities make plans to address and remove PFAS at the source, so that amounts of the chemicals in biosolids are reduced significantly. Gupta and Kyle Thompson, national PFAS lead, talked about the risk assessment in an interview with Treatment Plant Operator.
TPO: What was the EPA’s basic approach in preparing the risk assessment?
Thompson: The risk assessment focused specifically on PFOA and PFOS, which are the PFAS we have known about for the longest and have been the subject of the most scientific studies on their toxicity and how they move in the environment. For example, to what extent do they tend to transfer from the soil into crops. The assessment focused on biosolids land application and surface disposal, but did not look in depth at landfilling and incineration.
TPO: Does this risk assessment apply to potential PFAS exposure for the general public?
Gupta: No. The focus was on a hypothetical farm family, people who live on or near places where biosolids are land-applied. It is very specifically about the people who live on the land, apply biosolids on their farm, grows crops, feed the crops to livestock, eat the products from the livestock — the milk, meat and eggs — and drink the water from a well on the property.
TPO: What research was conducted and information gathered by EPA?
Thompson: They gathered a great deal of information. In particular, they looked at 18 pathways for exposure to PFAS through land-applied biosolids. For example, one pathway is from biosolids, to the soil, to groundwater, to drinking water. Another would be from biosolids, to the soil, to feed crops, to the cows, to the milk, to a person. They did their best to gather data from all exposure pathways but acknowledged that there is a lot they don’t know.
TPO: What basic assumptions were made in quantifying the risk? And how conservative were these assumptions?
Thompson: There is a lot of uncertainty in assessments of this kind. Assumptions were made for each exposure pathway, and people can reach different conclusions on, for example, how much PFAS-containing milk a given person is drinking. The EPA is saying that there is a range of data for any of these scenarios and that they looked at median and not, for example, the 99th percentile. However, a fair amount of conservatism is baked in by focusing on the farm family.
TPO: What specific health risks did the EPA look at related to land application of biosolids?
Thompson: They looked at non-cancer and cancer as health endpoints. For PFOA it was the risk of kidney cancer, and for PFOS it was liver cancer. For non-cancer health effects they looked at immune system impacts, reduced birth weight and elevated cholesterol for PFOA, and birth weight and high cholesterol for PFOS.
TPO: How would you quantify for the average person or clean-water operator how EPA defined acceptable risk?
Thompson: For the non-cancer risk, they used what is called a reference dose, which is the level of intake of a chemical relative to body weight below which there is definitely no health effect, and then they added multiple safety factors. For cancer, they used a one in a million increase in cases over the course of a lifetime.
Gupta: To put this in perspective, I would note that we are exposed to PFAS almost universally, in almost anything we interact with: the clothes we wear, food packaging, household dust . . . None of those exposures were considered in the EPA assessment. To understand the risks of PFAS, it’s important to add that context.
TPO: What are the practical impacts of this risk assessment on clean-water agencies that beneficially reuse biosolids?
Gupta: There are a number of potential impacts. One is the perceived risk associated with land-applied biosolids. Without full context or completing the public comment process, the EPA has essentially warned of unacceptable risk at greater that one part per billion of PFOS and PFOA. That value represents the very low end of the range of concentrations found in typical biosolids. So to the public, and possibly to legislators and regulators, there is likely to be a perception that biosolids with levels higher than that number pose an unacceptable risk.
TPO: What are the potential results of such a perception?
Gupta: Farmers who have a perception that the biosolids are unsafe would not want them to be land-applied. And landfills also may say they don’t want the material because it will lead to PFAS in their leachate, for which they fear they could be held liable. And so utilities may be left very quickly without avenues for managing their biosolids. And the biosolids will not just magically disappear.
TPO: Have we seen an example of this concern with the land application ban in Maine?
Gupta: Yes. Those utilities were left searching for ways to manage their biosolids. They were stockpiling them on site because they couldn’t send them anywhere. It was a lot of chaos. Now the material is being landfilled, but only one landfill in Maine accepts the material, and it is capacity-limited. And when that landfill is no longer an option, the utilities will be left without a good management option. This shows why it’s important to know the consequences of imposing restrictions and the potential end results.
TPO: What do you see clean-water agencies doing in response to the release of this risk assessment?
Gupta: They will probably start looking immediately to diversify their management options. If they’re land-applying on one or two farms, they may look for additional farmers to take their biosolids. If they’re land applying, they may also look for landfills willing to accept the material. They should also be strategically planning so that if a regulation comes down the pike and requires the destruction of PFAS, they know what their options are and how to get set up to exercise them. That’s not going to be easy. It takes a considerable amount of time and money to get those potential options online.
TPO: What recommendations does your company have for clients related to this assessment?
Gupta: We suggest they look at their data to understand where they are now. That will help them identify if there are industrial PFAS sources in their watershed or sewershed where they can apply source controls. In Michigan, that approach has had a dramatic impact. They had 90% reductions in PFAS when they were able to provide source control for their industries.
TPO: What is the role of communication in dealing with this risk assessment?
Gupta: We recommend that utilities stay informed and work with industry organizations like WEF and NACWA and their regional associations to get materials that help them communicate with their customers, regulators and legislators.
TPO: Should they be exploring the various emerging PFAS treatment technologies?
Gupta: We suggest that, if they are in a position to do so, they test and research the different technologies coming into the marketplace that hold some level of promise. There are still some questions related to their efficacy, cost, longevity and scalability, as well as questions about the PFAS base within the solid, gaseous and liquid products of these processes. If they’re able to do pilot testing, that be helpful to the utility and to the industry.
TPO: What are the next steps and timeline after this draft risk assessment has gone through review and a public comment period?
Thompson: The EPA didn’t outline a specific timeline, but we understand that there will be a public comment period until March 17. Then during that time or thereafter, they will review the comments and address those they find pertinent. Meanwhile they will look to incorporate risk management into the equation: what the options are for managing or mitigating the risk, as well as the cost and technical feasibility of options for doing something different with biosolids. Beyond that, there is potential for regulation, and we don’t know what form that will take.
TPO: What is the ultimate strategy for dealing with PFAS in biosolids?
Gupta: Source control is the right answer—getting non-essential uses of PFAS reduced quickly. That is the best solution from economic, environmental and public health perspectives. We need to stop using these chemicals unless they absolutely need to be in some products.
