Current Questions About PFAS: Interview with Expert Dr Ian Ross

An important action should be to immediately start restricting nonessen­tial uses like cosmetics, dishwasher rinse aids, car waxes or toilet paper. A focus on commercial and domestic uses that result in discharges to wastewater treatment plants, would assist with preventing PFAS being concen­trated in biosolids and spread on crops as fertilizer, with the PFAS potentially making its way into dairy products. To detect PFAS it can be important to apply non-target analysis, which can compre­hen­sively assess their concen­tra­tions, as opposed to using a list of just 120 target compounds. There are potentially thousands of PFAS with several non-targeted chemical analytical methods available to detect them.

European regulations are heading in the right direction as they combine restric­tions on products which contain PFAS, based on essential use. They also have regulations focused on the sum of all PFAS detected in water, which should be below 0.5 micrograms per litre. They are still assessing which non-target methods are viable for use, with a combination of chemical analytical tools likely being most effective and economic when used in a logical sequential order, to screen and identify PFAS. There can be a broad spectrum of PFAS, with multiple physical and chemical properties, some extremely toxic and others used as therapeutic drugs. So individual PFAS need to be assessed and regulated considering what is known about their properties.

If there is an essential need for PFAS, there are no effective alter­na­tives and they are used not in a dispersive manner (such as fire­fight­ing foams), then there’s a question regarding restric­tions until alter­na­tives are found. However, if the alter­na­tives are also extremely persistent, such as siloxanes, it seems wise to avoid them. The essential use concept is critical for application of PFAS restric­tions, with several uses potentially having limited envi­ron­men­tal impact. However, making PFAS manu­fac­tur­ers responsible for lifetime management costs associated with use and disposal of their products, could stimulate innovation to switch to less toxic, biodegrad­able, natural alter­na­tives. Many products contain PFAS where credible alter­na­tives exist, for example outdoor, waterproof fabrics can be effective using natural waxes.

There are several types of remediation tech­nolo­gies available to manage PFAS impacted soils. These include thermal approaches which look promising, but expensive, with air emissions needing careful assessment using non-target chemical analyses. The use of soil stabi­liza­tion can be a pragmatic approach to preventing PFAS leach from soils, but long-term studies have not been done to show that a range of PFAS remain stabilized over future years. Soil washing can be applied, but compre­hen­sive assessments of the range of PFAS associated with soils has not yet been done to evaluate success. The water treatment tech­nolo­gies associated with soil washing may need to involve several approaches to treat a range of PFAS.

There are several approaches for treatment of a broad range of PFAS, in the spectrum, such as nanofil­tra­tion or reverse osmosis. This can be expensive and creates a concen­trated waste, as a rejectate, that then needs to be treated to destroy the PFAS it contains. This can be achieved using a range of approaches in a treatment train. Several water treatment tech­nolo­gies are able to remove a specific but potentially limited range of PFAS, such as activated carbon, with ion exchange resins removing a broader array of PFAS. However, these types of treatment adsorptive approaches have not yet been assessed to remove the full spectrum of PFAS, that are anticipated to be removed using reverse osmosis.

CDM Smith is pioneering on multiple fronts to assist with PFAS management with over 60 funded research and development projects. For example, we were the first to apply combi­na­tions of innovative tech­nolo­gies such as foam frac­tion­a­tion, to concentrate a range of PFAS before they are destroyed using elec­tro­chem­i­cal oxidation. Further treatment trains using membrane filtration, foam frac­tion­a­tion and destructive treatment using hydrother­mal alkali (HALT) are being developed. Our technical team members were the first to commer­cially apply non-target methods for site inves­ti­ga­tions and develop an under­stand­ing of non-aqueous phase solid (NAPS) phases of PFAS, as liquid crystals, which adsorb to the interior of fire suppression systems. We have four US Department of Defense funded projects, focused on the impacts from PFAS to concrete surfaces, researching treatment approaches and assessing the reasons why concrete surfaces so much PFAS. We have recently char­ac­ter­ized the PFAS concen­trat­ing in biosolids at wastewater treatment plants across the US and have developed patented approaches to remove and concentrate the regulated PFAS by simply adapting wastewater treatment plant operations. Other works include searches for sources of PFAS using multiple different analytical tools to fingerprint PFAS.