The remediation process for PFAS can be quite involved, due to the many chemistry challenges.
Many typical water purification techniques are not able to remove PFAS from water. These ineffective techniques include bio-degradation, micron filtration, sand filtration, ultrafiltration, coagulation, flocculation, clarification, and oxidation by ultraviolet light, hypochlorite, chlorine dioxide, chloramine, ozone, or permanganate. None of these techniques will work. The only techniques that have been found to remove PFAS from water, are carbon adsorption, ion exchange, and reverse osmosis. Also, some experimental techniques such as gas flotation are being tried with success.
Before the PFAS removal treatment, the water must first be treated to remove suspended solids, particles, colloids, iron, manganese, Total Organic Carbon, oxidizing agents, bacteria, and various other contaminants, so that the carbon media, ion exchange media, or reverse osmosis unit can succeed in removing the PFAS. Thus the water is said to be pretreated prior to PFAS removal. Such pretreatment may include many of the techniques mentioned above in the second paragraph: micron filtration, clarification, etc.
Once the water has been prepared, the selection of PFAS removal technique is made. Finally, once the PFAS is removed by the carbon, ion exchange or reverse osmosis, it must be permanently disposed of. Each of these technologies has many advantages and disadvantages. Learn more about which PFAS removal technology is best for you by contacting us or downloading or brochure at the top of the page.
Typically disposal consists of either burning the PFAS in a high-temperature incinerator (best available technology). With carbon, the carbon media may be recycled for use elsewhere after the PFAS is burned off. With resin, the media is typically used once and incinerated. Resin lasts a very long time, so the economics are attractive. With reverse osmosis, the client must have a suitable destination for the concentrate water stream, which is termed RO Reject. This stream can itself be further treated with carbon, or in some cases, ion exchange before discharge. As the volume of reject water is small relative to the feed, the economics may succeed. Any release would be subject to approval by the regulatory authorities. The stream could also be deep well injected or treated by evaporation-crystallization followed by incineration or landfill.
- PFAS history
Perfluoro Alkyl substances come in many varieties. While there are an estimated 4700 (and growing) different types of these compounds, the ones of most concern are typically chains of 4-9 carbon atoms, fully saturated with fluorine, terminating in either a sulfonate or carboxylic moiety, or functional group. Some of the most common PFASs and their abbreviations are: Sulfonic Acids/Sulfonates: - PFBS – perfluoro butanesulfonic acid - PFHxS – perfluorohexane sulfonic acid 8 - PFOS - perfluorooctane sulfonic acid Carboxylic Acids: - PFBA – perfluoro butanoic acid - PFHxA - perfluorohexanoic acid - PFHpA – perfluoro heptanoic acid - PFOA – perfluorooctanoic acid - PFNA - perfluorononanoic acid
This class of compounds has been around for over 60 years and was originally developed by organic chemists in search of better performing surfactants in certain applications. The three most common classes of applications are firefighting foams, surface-active agents in consumer products, and surface-active agents in manufacturing. Firefighting foams using PFAS form an excellent film for the suppression of liquid hydrocarbon-fueled fires. The foam coats the liquid fuel and smothers the fire. Consumer products use PFAS for oil resistance in food packaging, and for stain resistance in fabric and leather. Manufacturing applications include emulsifiers, wetting agents, and constituents of coating materials. The dual lipo-phobic and hydrophobic characteristics of the PFAS molecule confer superior performance in these applications.
Substitution of non-PFAS surfactant materials or alternately, a program of careful use, handling, recovery and destruction are warranted. Incineration of the material is the gold standard of treatment of material that is removed from water or sludge. If incineration is not possible, then concentration and a method of permanent sequestration are called for. Although landfill is still allowed in some jurisdictions, this practice is expected to reduce in frequency, in favor of more permanent and less risky alternatives. The key emerging areas of treatment are:
- legacy sites: Remediation of firefighting sites, Remediation of military sites, Remediation of industrial discharge sites
- ongoing use cases: Treatment of drinking water that has been contaminated with PFAS, Cleanup of municipal wastewater treatment water, prior to discharge (recycling back into the environment), Cleanup of industrial wastewater prior to being discharged into a receiving body, Treatment of the newer classes of PFASs that have not yet had their safety determined