USU Researchers Working to Reduce 'Forever Chemicals' in Wastewater Biosolids Used in Ag

They’re called “forever chemicals” — found in grease-resistant packaging like fast food wrappers and used in construction, cosmetics and clothing, as well as many other products. They’re difficult to detect, difficult to remove and persistent in the environment.

Polyfluorinated alkyl substances, or PFAS, are a growing worldwide concern, causing known negative health impacts like increased cholesterol, low infant birth weight, thyroid disease, immune response repression and cancer.

The Utah Water Research Laboratory is investigating PFAS occurrence in wastewater biosolids used in agriculture. Biosolids improve soil’s water-holding capacity and soil’s organic content, as well as providing a wide range of nutrients necessary for plant growth such as phosphorus and nitrogen.

While biosolids can be a nuisance to landfills due to the quantities generated, they become a boon in the agricultural industry when turned into compost.

But that boon comes with an unwanted PFAS passenger.

These compounds linger in the biosolids, absorb into the plants, and cycle back through the system.

“We need to break the cycle and destroy them,” said Utah Water Research Laboratory Professor Ryan Dupont.

Dupont and graduate student Chase Fry are working to reduce PFAS in biosolids through mixing different chemical compounds into a high-temperature composting process.

Dupont’s team is taking samples from wastewater treatment plants in northern Utah and central Idaho and analyzing two possible compounds. One plant uses an iron oxide in the treatment process, and the residual left after removal could potentially degrade PFAS.

“The theory is that it could help with immobilizing the PFAS through cation bridging,” Fry said.

The other compound comes from a project headed by UWRL professor Yiming Su, who is looking at zero valent iron/zinc doped biochar.

Biochar is a porous sorbent, meaning it can absorb contaminants. Su’s work focuses on the use of biochar in water, but Dupont and Chase are mixing different levels of plain or doped biochar into compost to see how the concentrations affect PFAS levels.

Overall, the composting project is examining 32 mixes of compost, all with varying levels of one or both of the iron/zinc-based chemical compounds in an attempt to adsorb and sequester or degrade PFAS in the biosolids to reduce their uptake into crops grown on biosolids.

As concerns over PFAS in biosolids grow, research into minimizing the risks is crucial so land application of biosolids can safely continue, reaping the benefits of this soil amendment without future concerns for human health.

More information can be found in the UWRL Annual Report.