Sparging regulation for destruction of PFOS and PFOA using a hydrogen-polarized vacuum ultraviolet photolysis system
The PFAS “forever chemical” problem
Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS) are two of hundreds of specific types of PFASs, or perfluoroalkyl and polyfluoroalkyl substances. These substances, nicknamed forever chemicals, are found in various industrial applications due to their excellent ability to repel both water and oil. As a result, PFASs are used in hundreds of different items, ranging from waterproof clothing, nonstick cookware, firefighter equipment, and more.
Unlike many other substances, PFASs can easily build up in the environment since they are difficult to destroy using traditional remediation methods and are hard for natural processes to break down. As a result, forever chemicals present a great health risk to humans, plants, animals, and the environment and are found commonly in drinking water, food, and within homes.
Unfortunately, at even just a few parts per trillion, forever chemicals have been linked to a wide variety of human health issues. Risks from PFASs are widespread. In the US for example, almost 100 percent of Americans have already been exposed to toxic levels of these chemicals.
Some common health problems related to PFASs include:
- Low birth rates
- Severe liver and kidney issues
- Endocrine issues
- Reproductive issues
- Compromised immune system
- High cholesterol
- Increased risk of cancer
New methods to eliminate forever chemicals
As a result of these health risks, researchers have been working to find new strategies to mitigate human exposure to forever chemicals and to more effectively eliminate them from the environment while manufacturers have started to limit or discontinue PFAS use in various products.
Researchers at the University of California developed a novel method to destroy PFOAs and PFOSs present in water using a hydrogen-polarized vacuum ultraviolet photolysis system. By exposing the PFAS-contaminated water to a vacuum UV light at 185 nm after pre-saturating the water with 99.99% H2 for 30 min and continuously sparging with H2 throughout the reaction, it was found that there was degradation of PFOA and PFOS up to 95% as well as defluorination up to 94%.
Flow regulation in hydrogen-polarized vacuum ultraviolet photolysis systems
To remove PFOA and PFOS from drinking water, hydrogen is first added to the contaminated water. After this, the water is exposed to a 185 nm vacuum UV light at a sufficient voltage and wattage while hydrogen is continuously pumped into the water. After just a few minutes to hours, the treatment is complete.
For this system to function properly, H2 must be accurately added to the water undergoing PFAS removal, both prior to and during the process via sparging. Additionally, nitrogen gas is used as a purge gas and pumps continuously into the lamp-housing quartz sleeves in order to reduce attenuation of the 185 nm vacuum UV light by the ambient air.
By implementing accurate and precise mass flow controllers for both the hydrogen sparging and the nitrogen purging processes, gas waste is limited, ensuring that researchers can determine the precise amount of hydrogen necessary to degrade a specific amount of PFAS using this process.
Alicat MC series mass flow controllers are well suited for sparging applications. With full-scale flow ranges from 0.5 SCCM to 12,000 SLPM and a wide turndown ratio of 0.01% to 100%, they offer exceptional precision and repeatability across a range of flow volumes – key factors in ensuring consistent results.
Likewise, CODA KC-Series mass flow controllers deliver high accuracy (±1.0% of reading standard, ±0.5% of reading in high-accuracy models), making them ideal for variable PFAS dosing. With Modbus, EtherNet/IP, and PROFINET support, they integrate seamlessly with PLCs and SCADA systems—perfect for automated, programmable gas delivery in both pilot and full-scale PFAS remediation.
A recent study explored an alternative setting where nitrogen was used to sparge inside UV reactors to degrade PFAS. While the method showed some promise, it achieved less than 10% defluorination for PFOS and failed to meet the general standards for PFAS destruction for wide use.
On a more hopeful note, researchers at a Chinese university in 2024 demonstrated that simple techniques like boiling water combined with activated carbon filtration can reduce PFAS levels in drinking water by 50–90%, offering a more accessible solution for reducing exposure.
Why it matters, 2025 update
Findings from the Environmental Protection Agency’s Fifth Unregulated Contaminant Monitoring Rule in 2025 as compared to 2024 show that an additional 15 million Americans are at risk of being exposed to harmful PFAS chemicals, bringing the total at risk to 158 million.
According to findings released from a 2024 survey done by the U.S. Government Accountability Office, this could be partially attributed to poor as yet limited implementation of regulations, as only 33% of water systems across the U.S. had fully implemented treatment methods for PFAS. The requirement to be fully compliant is still several years away. Other factors, like industrial pollution and waste treatment contribute to sustain forever chemicals in the environment.
Despite these challenges, scientific research into PFAS mitigation continues to make strides and while the science may not be there quite yet –the continued efforts of researchers are leading the charge in developing innovative solutions. Their work is needed to improve water quality and safe living conditions for communities across the globe.