Communities and federal agencies are waking up to the dangers of “forever chemicals” in wastewater treatment sludge, which is often sprayed on farm fields as fertilizer. In mid-January, the federal Environmental Protection Agency warned that this practice endangers human health. A month later, Johnson County in northeast Texas declared a state of emergency over the contamination of farm fields with per- and polyfluoroalkyl substances, or PFAS, from sewage sludge. John Scott, a research scientist at the Illinois Sustainable Technology Center who studies PFAS in wastewater treatment facilities and landfills, spoke with News Bureau life sciences editor Diana Yates about the problem.
You recently published a study of PFAS in wastewater treatment facilities and landfills. What did you find?
In our study, we measured the concentrations of PFAS in two key inputs to wastewater treatment facilities: wastewater influent, which comes from storm and sanitary sewage systems, and landfill leachate. We found that landfill leachate contained significantly higher levels of PFAS than wastewater influent — measured in parts-per-billion versus parts-per-trillion, respectively.
However, it’s important to note that while landfill leachate has higher PFAS concentrations, wastewater treatment plants receive much larger volumes of influent. This means wastewater influent is the largest source of PFAS into these systems.
We also examined the two primary outputs of wastewater treatment: effluent, the liquids; and biosolids, the solid waste byproduct of the treatment process. Our findings indicate that while wastewater treatment facilities are effective at removing PFAS from the incoming materials, these forever chemicals tend to concentrate in the biosolids.
How long have we known about the problem of PFAS in sewage sludge?
The presence of PFAS in biosolids has been known for quite some time, and I recall several papers published around 2008 that indicated these compounds were present in sewage sludge. While the presence of PFAS in biosolids has been recognized, it didn’t receive much attention initially, likely because the concentrations were relatively low — typically in the parts-per-billion range. However, with the increasing body of research linking PFAS to potentially adverse human health effects, more focus is now being placed on these materials. The key question that needs to be addressed is: “Do the concentrations of PFAS observed in biosolids pose a risk to ecosystems and human health?”
How widespread is the practice of spraying sewage sludge on farm fields?
The use of biosolids in land application is widespread, though it varies by region and the specific characteristics of the biosolids. In the Midwest, for example, approximately half of the biosolids produced are applied to agricultural land. There are established regulations governing the use of these materials, particularly concerning pathogen reduction and limits on metals such as arsenic, cadmium and mercury.
However, in 2021, Maine implemented a ban on the land application of biosolids due to growing concerns about contamination, particularly from PFAS. Regulating PFAS in biosolids or potentially banning their land application altogether will present significant challenges to the wastewater industry.
The issue lies in the persistence of PFAS in the environment, making their removal or reduction difficult, which could have wide-ranging implications for wastewater treatment practices and biosolid disposal strategies.
Why are we still spreading this pollution across the agricultural landscape?
Wastewater treatment facilities have limited options when it comes to managing biosolids. They can landfill or incinerate these materials, but both options come with significant costs and environmental impacts. Given that biosolids contain valuable nutrients like nitrogen and phosphorus, land application is often the preferred method. However, this approach carries risks, especially since biosolids can contain a wide range of other chemicals and materials.
It would be nearly impossible to thoroughly vet every chemical and its degradation products that could end up in these materials. And that’s just considering the chemicals we are aware of today. What about the thousands of new chemicals introduced to the market each year? The growing complexity of chemical contamination only increases the challenges of safely managing biosolids.
Is there a solution to the problem of PFAS accumulation in wastewater treatment plants?
For starters, the public needs to move away from consuming products that contain PFAS. If we can phase out the production of PFAS, we can reduce — and hopefully eliminate — the presence of these compounds in our solid and liquid wastes.
It’s important to note that wastewater treatment facilities did not create the PFAS issue; rather, they are managing the PFAS that have been introduced by industries and the public.
However, it’s essential for the public to not only be made aware of the PFAS problem but also to have a way of determining whether the products they consume contain these chemicals. I believe requiring companies to label products containing PFAS would be a significant step forward in raising awareness.
Additionally, we need to invest in cost-effective and practical technologies to address PFAS in landfill leachate. Even if we find better alternatives to PFAS or manage to remove them entirely, we must remember that we are still dealing with decades of legacy PFAS contamination. This will require ongoing efforts to address and manage these compounds for generations to come.
What else can be done to minimize the risks?
Addressing environmental issues at the source is always the most cost-effective and efficient method of pollution prevention. However, there is ongoing research aimed at treating biosolids for contaminants like pathogens and PFAS while still retaining their fertilizing properties. For instance, my colleague ISTC research scientist Wei Zheng is developing specialized additives and thermal treatment technologies for biosolids. His strategy is to either destroy the problematic components of biosolids or to immobilize them within the material, preventing them from being taken up by plants or becoming fugitive in the environment. While he has made great strides in this area, his current challenges include scaling up the process to meet the demand for biosolid treatment and ensuring cost-effectiveness.
