Researchers Test Two Methods to Destroy PFAS in Water

Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany are testing two technologies designed to destroy per- and polyfluoroalkyl substances (PFAS) in water rather than merely relocating them. Preliminary results showed that hydrodynamic cavitation degraded about 37% of perfluorooctane sulfonate (PFOS) in tap water, while cold atmospheric plasma achieved near-complete breakdown of both long-chain and short-chain PFAS.

Why PFAS Are So Hard to Remove

PFAS contain carbon-fluorine bonds, among the strongest in organic chemistry, which makes them resistant to natural breakdown. More than 10,000 compounds are classified as PFAS, and some are suspected of damaging genetic material and increasing cancer risk, according to reporting cited by HZDR. The chemicals are present in the bloodstream of most Americans, and high concentrations have been detected in Germany’s Elbe River, a finding that has spurred research under the country’s National Water Strategy.

PFAS were first produced in a laboratory setting in the mid-20th century, with early producers including 3M and DuPont. According to Children’s Health Defense, those companies “made billions of dollars producing millions of pounds of ‘forever chemicals,’ even though they knew, for decades, the chemicals damaged environmental and human health.” Teflon, one well-known PFAS product, was discovered in 1938 by a chemist working for DuPont, according to David Michaels’ book “The Triumph of Doubt.” A January 2025 report from the U.S. Environmental Protection Agency found that so-called “forever chemicals” have contaminated 2,394 water systems across the United States.

Hydrodynamic Cavitation Uses Collapsing Bubbles

In hydrodynamic cavitation, water passes through a constriction, forming vapor bubbles that PFAS attach to because of their surface-active properties, according to Dr. Sebastian Reinecke, head of HZDR’s Department of Water and Environmental Technologies. When the bubbles collapse under rising pressure, local temperatures spike to several thousand degrees Celsius, breaking the carbon-fluorine bonds. Cavitation also creates highly reactive hydroxyl radicals that may help destroy compounds produced during the initial stages of PFAS breakdown.

The experiments focused on PFOS, a well-studied and exceptionally persistent member of the PFAS family. By the end of the test, the process had degraded about 37% of the dissolved PFOS molecules while releasing fluoride. Reinecke stated the team’s goal: “Our goal is to improve the process to a degradation rate of more than 80% of the PFAS in the solution and mineralizing more than 50% of the fluorine that is bound in the chemicals.”

Cold Plasma With Gas Bubbles Attacks PFAS Rapidly

In a separate set of experiments, environmental engineer Dr. Amit Kumar combined cold atmospheric plasma with gas dispersion to destroy PFAS. The method works under normal conditions and does not require catalysts or added chemicals. Reinecke described the setup: “The PFAS attach to the surface of the gas bubbles. As they rise, the water is constantly circulated. This brings the PFAS to the surface, where they are broken down in the plasma.”

The plasma treatment nearly completely degraded both long-chain and short-chain PFAS and released about 35% of the fluorine atoms as fluoride salts. The results were faster than cavitation, but the method consumes more energy per volume unit and produces numerous transformation products that have not yet been fully characterized. Reinecke noted that additional experiments are underway to determine whether any of those transformation products could pose health risks.

Researchers Plan to Combine Both Technologies

The HZDR team is now adapting the plasma system to treat larger amounts of contaminated water. By using multiple electrodes and a technical gas injector, the researchers are increasing the reaction volume from roughly 50 milliliters to five liters. The longer-term goal is to combine plasma treatment with hydrodynamic cavitation into a single system. Reinecke said, “I believe we’ll achieve high degradation rates by combining the highly reactive species from the plasma with the effects of cavitation.”

If successful, the combined technology could give industrial operators a new method for destroying PFAS in contaminated wastewater before the chemicals spread into rivers and oceans, officials said.

FAQ

What are PFAS and why are they called forever chemicals?

PFAS, or per- and polyfluoroalkyl substances, are a class of more than 10,000 compounds characterized by carbon-fluorine bonds that are among the strongest in organic chemistry. Their durability made them useful in manufacturing for greaseproof, stain-proof and water-resistant products, but that same stability means they resist natural breakdown and persist in the environment and human bodies.

How do the two PFAS destruction methods tested by HZDR work?

Hydrodynamic cavitation forces water through a constriction, creating vapor bubbles that collapse under pressure and generate localized temperatures of several thousand degrees Celsius, which break carbon-fluorine bonds. Cold atmospheric plasma combined with gas dispersion lets PFAS attach to rising gas bubbles at the water surface, where they are broken down by the plasma. The plasma method does not require catalysts or added chemicals.

What results did the HZDR tests produce?

Hydrodynamic cavitation degraded about 37% of dissolved PFOS in tap water while releasing fluoride. Cold atmospheric plasma nearly completely degraded both long-chain and short-chain PFAS and released about 35% of the fluorine atoms as fluoride salts, though it consumed more energy per unit volume and generated transformation products not yet fully characterized.