With one of the strongest chemical bonds, per- and polyfluoroalkyl substances (PFAS) upend conventional approaches and call for creative solutions. In our Februrary 2019 PFAS Newsletter we introduced two treatment technologies—granular activated carbon (GAC) and anion exchange resin (AIX). These methods use a sorbent (GAC or AIX) to separate PFAS from a drinking water or groundwater source. Though successful pilot and full-scale applications have elevated the profile of these separation technologies, they have not entirely solved the PFAS problem.
Recirculating PFAS in the environment from one media to another without destruction draws significant concern globally. Currently, there is no clear guidance on managing PFAS-laden wastes. As such, spent GAC or AIX are often disposed in local landfills or are incinerated at temperature below 1000°C, which removes PFAS from spent sorbent but does not destroy them. In addition, there are concerns about accidental PFAS releases during shipping and handling PFAS-laden wastes off site. To effectively neutralize PFAS as a threat to human health, researchers are increasingly testing the power of destruction technologies.
When Destruction Works
- AFFF concentrates
- Groundwater within PFAS source areas
- Remediation waste streams (such as wastewater generated from regeneration of GAC or regenerable ion exchange resin, foam fractionation, soil washing, rejected reverse osmosis concentrates, chemical or electro-coagulation)
- Landfill leachate
Destruction technology...can completely defluorinate PFAAs (such as PFOS and PFOA) to innocuous end products.
Because of the emerging market for destructive PFAS technologies, they are often promoted hastily without demonstrating complete defluorination and without confidence the technology can meet stringent effluent discharge requirements. Carefully consider the applicability of these technologies for a specific site and/or application before investment in full-scale treatment systems.
The development and commercialization of PFAS destruction technologies will not be easy. Several ex-situ destructive technologies have moved from flask to field, which include sonolysis, electrochemical oxidation and ultraviolet oxidative/reductive destruction. Careful consideration and understanding of PFAS transformation and defluorination must be incorporated into the technology evaluation for a particular site/application with thoughtful design of bench and pilot scale systems to demonstrate technology and incorporate economic feasibility in the selection process.
The Road Ahead
Consideration of balanced technology benefits and limitations that should be discussed with technology providers include:
- High energy demand and feasibility of high energy/cost at the scale required for the system
- Health and safety concerns
- Feasibility of operating large-scale systems, if required
- Incomplete PFAS destruction resulting in accumulation of fluorinated intermediates that are generated but not measurable
- Feasibility of achieving stringent (i.e. very low) treatment requirements
- Effectiveness in destroying all PFAS chemicals, including short chain PFAS
- Generation of non-PFAS toxic byproducts
At CDM Smith, our approach to assessing PFAS destructive technologies includes treatability testing at the bench, pilot and full-scale using three lines of evidence, which results in more accurate verification of PFAS destruction. And our collaborations with universities and research foundations allow us to explore the latest analytical methods for understanding the destructive mechanisms, including Total Oxidizable Precursor Assay, nontarget PFAS analysis, and total extractable organic fluorine analysis.