PFAS do not travel through wastewater treatment plants as a single, uniform group. Sarah Ortbal, a researcher at The University of Alabama and winner of the 2026 Metrohm Young Chemist Award, found that chain length and chemistry influence where these compounds end up during treatment. “Many of the smaller PFAS analytes, typically C5 or less, stayed in the aqueous phase,” notes Ortbal. In practical terms, that means shorter-chain compounds tended to remain with the water and leave through aqueous effluent.
Longer-chain compounds followed a different path. Ortbal reports that longer-chain PFAS, including compounds such as PFOA and PFOS, along with phosphate esters and 5:3 FTCA, were more likely to accumulate in biosolids or continue cycling through the biological basin. That split between water-phase and solids-phase behavior matters because it shows that wastewater treatment does not simply remove PFAS. It redistributes them across the treatment train.
Recirculation Changes How We Think About PFAS Removal
That redistribution becomes even more important when PFAS recirculate through activated sludge and biological treatment stages. Ortbal points out that this stage-by-stage view revealed behavior that would be easy to miss in a simple influent-versus-effluent comparison. “This was one of the first times anyone had looked individually at all the different stages of a treatment plant,” she explains. Her findings push the conversation beyond whether PFAS concentrations drop at the end of the process and toward where those compounds go instead.
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That shift has major implications for removal strategies. If PFAS move into biosolids, treatment plants face a disposal problem as much as a water-treatment problem. Ortbal warns that tighter regulation of PFAS in solids could prevent many biosolids from being land applied, or even going to normal landfills, adding that this could force facilities to rely on hazardous waste landfills at much higher cost. She argues that the field now needs to prepare for potential state and federal regulations, and may need to shift biosolid management approaches to safely landfill or land-apply biosolids.
Statewide Monitoring Helped Separate Wastewater Impacts From Other Sources
Ortbal’s statewide monitoring work added a broader environmental layer to the treatment picture. Her team sampled across all 67 Alabama counties and 169 locations, covering large streams, small streams, urban areas, and rural sites. That wide net made it possible to compare upstream and downstream locations near wastewater treatment plants and test whether those facilities were driving PFAS contamination in receiving waters. The answer, in Alabama at least, was strikingly clear.
“We found no real difference between upstream and downstream sites near wastewater treatment plants,” Ortbal recalls. She links that result to hydrology rather than the absence of contamination, because wastewater plant discharge accounted for a very small share of streamflow, averaging less than 2%. That broader survey helped redirect attention toward industrial hotspots and larger direct inputs to rivers, rather than assuming treatment plants were the dominant source everywhere.
Treatment Technologies Show Promise, but Destruction Remains Unresolved
Ortbal’s findings also reinforce a key distinction in PFAS treatment: removal is not the same as destruction. She notes that granular activated carbon, reverse osmosis, and ion exchange remain the leading technologies for PFAS removal, but these approaches mainly transfer PFAS into another medium rather than eliminate them. “Those methods remove PFAS, but they do not destroy them,” she emphasizes. That limitation helps explain why wastewater plants can reduce water-phase concentrations while still leaving a difficult waste-management problem behind.
Her own work explored activated carbon and heat-activated peroxydisulfate as bench-scale treatment approaches. The results were encouraging, but she is careful not to overstate them. “The results were promising, but they are still at the bench scale,” Ortbal stresses, adding that scalability and feasibility still need much more study. That balance between promise and limitation runs through the broader PFAS treatment landscape: methods can move the problem, and some may begin to break it down, but full-scale solutions remain a work in progress.
