What’s Being Done to Deal with “Forever Chemicals” in Our Water?

In all likelihood, you’ve been exposed to PFAS (per- and polyfluoroalkyl substances) for years without even knowing it. Whether through food packaging, non-stick cookware, waterproof clothing, or drinking water sources, you and most of the global population have probably been regularly exposed to a class of over 4000 substances that fall into the family of PFAS [1],[2]. Known as “forever chemicals”, PFAS is detectable in virtually the entire US population [3]. The harmful effects of PFAS are only recently coming to light. And undoubtedly, the list of health complications resulting from PFAS exposure will grow as we learn more about this class of chemicals. But efforts are underway to deal with these chemicals that have found their way into so many aspects of our life. Even though the complexity of the problem ensures no simple fixes, remediation techniques are being developed and refined to remove and reduce PFAS from drinking water supplies.

PFAS in our environment

The physiochemical properties of PFAS that have made its commercial and industrial use so widespread, have also resulted in its being found in so many aquatic and terrestrial environments. The carbon-fluorine (C-F) bond within PFAS is extremely stable and highly resistant to heat and environmental degradation. The persistent nature of these chemicals has resulted in their being labeled “forever chemicals” [4].

A number of sites may contribute to the introduction of PFAS into the environment. This includes chemical plants that produce PFAS, military bases, firefighting training centers, airports, textile and carpet manufacturing facilities, wastewater treatment plants, and landfills [3]. Inevitably, PFAS finds its way into groundwater, surface water, and soils. PFAS has been detected in many different trophic levels in various ecosystems. Human exposure may be through sources such as non-stick cookware, tap water, or the food supply.

While the data is far from complete, PFAS accumulations in human tissue are now being linked to a variety of health problems. Low levels of these chemicals have been detected in humans across the globe [5]. Health issues may include cancer (kidney and testicular), decreased immune response, and developmental defects in fetuses and infants. The negative effects of PFAS in plants and non-human animals are less well known but are also under investigation [6].

In 2016, the EPA issued a health advisory to limit PFOA and PFOS exposure to less than 70 parts per trillion, but these standards are not currently enforceable [7]. (PFOA and PFOS are two of the most common chemicals in the PFAS family.)

The Delaware River: A water source for New Jersey
Photo by Craig Aimone 

What’s currently being done to mitigate PFAS in our water

Remediation technologies are being used to remove and reduce PFAS from drinking water supplies. While these technologies have had varying degrees of success, there is no one technology that addresses PFAS in all water supplies due to the number of variables between water sources. For example, techniques that work to remove long chain PFAS don’t necessarily work to remove short chain PFAS as effectively. And while removing PFAS from water supplies is essential, it is not a complete solution as now a concentration of PFAS exists that must subsequently be dealt with. The waste product resulting from removal of PFAS from water or soil must either be stored for the long term or destroyed.

The technologies used in treating PFAS in water have largely been adapted from other wastewater treatment processes. These technologies are centered around the concepts of adsorption, filtration through membranes, and destruction of the PFAS on a molecular scale.

Adsorption uses the attractive interactions between PFAS molecules and a specially designed adsorbent material that has been engineered specifically for the purpose. Adsorption technologies are currently the most widely used PFAS remediation technology partly due to their affordability [8]. Activated carbons and ion exchange (IX) resins are two of the leading adsorption techniques. IX resins are now being commercially designed specifically for the purpose. Both techniques still have challenges that need to be addressed. When utilizing activated carbons, other contaminants in the wastewater such as organic materials and minerals compete with PFAS for adsorption sites on the activated carbon which reduces the amount of PFAS that is adsorbed. IX resins face similar challenges with the pH of the water and the resin properties also playing a factor in the efficiency of PFAS adsorption. Even with these challenges, both techniques can remove PFOA and PFOS from water at concentrations in the parts per billion range with greater that 90% efficiency [9]. Bio-sorbents such as bio-char, wheat and rice husks, and cellulose are also showing promise as adsorbents.  

The most promising filtration techniques include nanofiltration (NF) and reverse osmosis (RO). Both NF and RO use membranes with specific pore sizes to physically stop PFAS particles from passing through. NF typically use membrane pore sizes from 1-10 nanometers (nm) whereas RO uses membranes with pore sizes of less than 1 nm [10]. High pressure is used to force the contaminated water through the membrane which results in the separation of the contaminant from the water. Fouling, or obstruction of the membrane inevitably results from the process which decreases the amount of PFAS captured. Both processes commonly exceed 95% capture rates and can both handle high volumes of water. These technologies are both relatively expensive to set up and operate, and both produce a stream of wastewater concentrated with PFAS needing further handling and treatment. Despite their drawbacks, both processes are well studied, relatively effective technologies.

The breakdown of PFAS “molecules” is the ultimate goal of remediation. Even if PFAS is successfully removed from soil or water, if it can’t be destroyed and turned into a non-toxic byproduct, it must then be stored indefinitely. Destruction is primarily accomplished by breaking up the C-F bond within a PFAS molecule. Ultraviolet light has shown some success, but it can also result in the formation of hydrofluoric acid (HF) which is a toxic byproduct also needing some form of treatment [11]. Incineration at high temperatures is another technique being utilized, but it often produces toxic gases. These technologies continue to be researched.

It seems likely that some combination of these technologies will be the best approach to this problem. Limitations of the treatments discussed here can be considered and complimentary technologies can be used to maximum effect. The potential downside of a combined approach will be the costs associated with multi-staged treatments [10].

Prohibiting the manufacture and use of PFAS is an obvious step forward. This of course wouldn’t do anything to remediate the PFAS already in our environment, but it would stop the predicament from becoming worse. The sheer number of chemicals within the PFAS ‘family’, and the fact that there are most likely chemicals still being identified as PFAS adds to the complexity of the landscape. Agencies are starting to  regulate the use of PFAS, but their complete prohibition seems unlikely in the short term.

Wastewater treatment tanks in Burlington County, New Jersey 
Photo by Craig Aimone

Downplaying the health risks of PFAS

Unfortunately, the health agencies we rely on to inform of us of the hazards we may encounter in our everyday environment are failing to appropriately inform us of the risks of PFAS [12]. Studies conducted have found that federal and state webpages do not treat this issue with an appropriate level of nuance. They fail to address the needs of communities most at risk to PFAS exposure. Websites and other communications downplay the health risks and largely fail to provide helpful guidance to mitigate the risks of PFAS. The public is largely left uninformed and without any effective strategy to deal with this pervasive issue.

The future of PFAS

Introduced in the 1950’s, PFAS has since been discovered in almost every corner of the globe. With numerous pathways to exposure, PFAS has become a threat to the health of our population and our environment. We still don’t know the complete scope of health problems caused by exposure to PFAS. While efforts are underway to develop technologies to reduce, remove and destroy PFAS, much work remains to be done. Technologies need to continue to be improved by becoming more efficient and economical. Health organizations need to do a better job of informing the public of the dangers and providing strategies for those most at risk. Informing the public may also force governments to act more quickly to develop strategies to deal with the problem of “forever chemicals.”

 

 References

[1]        D. M. Wanninayake, “Comparison of currently available PFAS remediation technologies in water: A review,” J. Environ. Manage., vol. 283, p. 111977, Apr. 2021, doi: 10.1016/j.jenvman.2021.111977.

[2]        K. H. Kucharzyk, R. Darlington, M. Benotti, R. Deeb, and E. Hawley, “Novel treatment technologies for PFAS compounds: A critical review,” J. Environ. Manage., vol. 204, pp. 757–764, Dec. 2017, doi: 10.1016/j.jenvman.2017.08.016.

[3]        D. M. Kempisty and L. Racz, Eds., Forever chemicals: environmental, economic, and social equity concerns with PFAS in the environment, First edition. Boca Raton: CRC Press, 2021.

[4]        D. B. LaFrance, “PFAS 101,” J. AWWA, vol. 111, no. 7, pp. 10–10, Jul. 2019, doi: 10.1002/awwa.1318.

[5]        M. F. Rahman, S. Peldszus, and W. B. Anderson, “Behaviour and fate of perfluoroalkyl and polyfluoroalkyl substances (PFASs) in drinking water treatment: A review,” Water Res., vol. 50, pp. 318–340, Mar. 2014, doi: 10.1016/j.watres.2013.10.045.

[6]        J. Zodrow et al., “PFAS Experts Symposium 2: PFAS Toxicology and Risk Assessment in 2021—Contemporary issues in human and ecological risk assessment of PFAS,” Remediat. J., vol. 32, no. 1–2, pp. 29–44, Mar. 2022, doi: 10.1002/rem.21706.

[7]        E. M. Bell et al., “Exposure, health effects, sensing, and remediation of the emerging PFAS contaminants – Scientific challenges and potential research directions,” Sci. Total Environ., vol. 780, p. 146399, Aug. 2021, doi: 10.1016/j.scitotenv.2021.146399.

[8]        H. N. Phong Vo et al., “Poly‐and perfluoroalkyl substances in water and wastewater: A comprehensive review from sources to remediation,” J. Water Process Eng., vol. 36, p. 101393, Aug. 2020, doi: 10.1016/j.jwpe.2020.101393.

[9]        J. Horst et al., “Water Treatment Technologies for PFAS: The Next Generation: J. Horst et al ./Groundwater Monitoring & Remediation” Groundw. Monit. Remediat., vol. 38, no. 2, pp. 13–23, May 2018, doi: 10.1111/gwmr.12281.

[10]      S. Yadav et al., “Updated review on emerging technologies for PFAS contaminated water treatment,” Chem. Eng. Res. Des., vol. 182, pp. 667–700, Jun. 2022, doi: 10.1016/j.cherd.2022.04.009.

[11]      S. Garg et al., “Remediation of water from per-/poly-fluoroalkyl substances (PFAS) – Challenges and perspectives,” J. Environ. Chem. Eng., vol. 9, no. 4, p. 105784, Aug. 2021, doi: 10.1016/j.jece.2021.105784.

[12]      A. Ducatman, J. LaPier, R. Fuoco, and J. C. DeWitt, “Official health communications are failing PFAS-contaminated communities,” Environ. Health, vol. 21, no. 1, p. 51, May 2022, doi: 10.1186/s12940-022-00857-9.