Since 2015, global guideline and regulatory values regarding poly- and perfluoroalkyl substances (PFASs) have rapidly evolved. While toxicological information is widely available for perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), guideline values have also been proposed or promulgated for many other species in the class. Approaches to setting regulatory values include direct read across approaches from PFOS and PFOA values to other compounds, scaling regulatory values on the basis of relative bioaccumulation, regulating multiple PFASs as a sum that assumes equal toxicity, regulating multiple PFASs as a sum that assumes a weighted toxicity, and setting analytical detection limits as the basis of regulation. Different regions have taken different approaches, and individual jurisdictions or states within specific regions have shown a propensity to adopt or advance upon the regional level approach.

This presentation will summarize the regulatory landscape across different regions globally, with an emphasis on North America. Under various regulatory paradigms, the best approaches to managing site investigation and clean up or water treatment will be discussed. For example, under regulatory paradigms where short chain PFASs or precursors can drive risk, different analytical tools and clean up technologies may be preferred to those used to characterize and treat PFOS and PFOA. A decision-tree based approach to site management based on the regulatory horizon will be presented.

Poly and Perfluoroalkyl Substances (PFASs) have emerged as high-priority and high-profile contaminants. PFAS contamination is widespread resulting in a need for large scale and point of entry (POET) PFAS treatment systems to treat drinking water supplies for PFAS. These PFAS impacts are also leading to additional PFAS investigations and the need for source area remediation. There are also increasing concerns and regulatory scrutiny of a larger suite of PFASs, including short-chain compounds, that have proven to be more difficult to treat with granular activated carbon (GAC); which has generally been considered the best available technology for PFOS/PFOA treatment.

There is an emerging need for remediation technologies that will contain and treat PFAS at the source. However, as more source area remediation is initiated where PFOS/PFOA and non-PFAS co-contaminant (e.g., petroleum hydrocarbons) concentrations are higher and concentrations of short chain compounds are also often higher, several potential concerns emerge when considering GAC. These potential concerns include frequency of GAC change outs, short chain removal performance, co-contaminant loading and preferential removal and others. These emerging needs require additional PFAS treatment options beyond GAC. High costs and concerns regarding potential off-site PFAS liabilities associated with landfill disposal and GAC reactivation also results in a need for on-site PFAS destruction.

Ion-exchange (IX) resin has shown significant promise for treating a broad suite of PFASs. These synthetic media can be regenerated on-site and reused. Regenerant solutions can then be distilled on-site to recycle/reuse the regenerant, yielding a concentrated PFAS residue.

An emerging technology developed at Clarkson University has been used successfully to destroy PFASs and a broad suite of co-contaminants in this residue. Although still under development, the Enhanced Contact Low Energy Plasma Reactor demonstrates that onsite destruction of PFASs can be accomplished.

This presentation will include the results of a several projects involving PFAS treatment using IX resins ranging from internally and externally funded R&D projects, to one of the first large-scale pump and treat systems employing IX resin and on-site regeneration at a large Department of Defense facility. Results from bench scale plasma destruction will also be presented.

Poly- and perfluoro alkyl substances (PFAS) comprise a diverse class of contaminants, which include PFOS (perfluorooctane sulfonate) and PFOA (perfluorooctanoic acid). PFAS are not amenable to bioremediation or conventional chemical treatment, and this limits in situ remediation options. PFAS are relatively ubiquitous in the environment at low concentrations, but source areas can exhibit higher PFAS concentrations. While the USEPA Health Advisory Limit of 70 nanograms per liter for the summation of PFOA and PFOS is not a maximum contaminant level (MCL), to be protective of potential beneficial reuse aquifers, PFAS groundwater plumes emanating from source zones will require some form of active management.

The use of conventional sorbents, such as granular activated carbon (GAC) and anion exchange (AIX) resins, to address PFAS in water have become a “de facto” interim measure in response to immediate needs for PFAS removal from drinking water. Challenges of more comprehensive PFAS treatment in drinking water may also be addressed using technologies such as reverse osmosis or nano-filtration. Extending these technologies to extracted groundwater for remediation purposes, which have various degrees of geochemical and co-contaminant competition often requires a treatment train, combining conventional sorbents and engineered filtration with more innovative and emerging remediation solutions for PFAS. These emerging solutions include many types of technologies to address source zones, mitigate mass flux in aquifers, or address PFAS in extracted water to improve the efficiency of conventional drinking water treatment technologies. There are new flocculation technologies, novel AIX resins, new-engineered sorptive media, electrochemical oxidation, electrocoagulation, sonolysis, and advanced oxidation processes combined with advanced reductive processes.

Remediation technologies for PFAS source zones in soil are primarily limited to excavation with on-site or off-site incineration (or other forms of thermal treatment) and in situ soil stabilization. For in situ soil stabilization to be considered viable, ongoing research and development is being conducted to evaluate the longevity of fixation amidst circumneutral pH and biotransformation, which may enhance PFAAs dissolution. Remediation of PFAS source zones and the associated groundwater plumes presently requires multiple technologies to protect human health in a cost-conscious manner. An investment in research and development to explore new technologies is part of a key initiative for groundwater preservation and protection of human health. The technologies discussed here will be presented, and their applicability/readiness to the remediation market will be assessed.

Per- and polyfluorinated alkyl substances (PFASs) are ubiquitous, persistent, anthropogenic chemicals that bioaccumulate in both humans and biota. The toxicity of certain PFASs such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) has been observed in some rodent studies. The potential for deleterious effects in humans is suspected, and is under further study. In response to our greater understanding of the toxicological properties of these compounds, different contaminant guidelines for selected PFASs in environmental matrices have been introduced in several jurisdictions

While significant effort continues to be focused on delineating the extent of PFAS contamination, an additional difficulty that may influence remediation efforts is the potential for in situ transformation of PFAS precursor compounds to the current PFASs of concern. These precursor compounds are not included as part of the suite of routine PFASs currently measured, and over time may transform to these compounds, introducing potential future risk and liability. This may require remediation efforts to not only consider target compounds of interest, but to also account for these oxidizable PFAS precursors. The challenge in accounting for these precursors is that the pool of precursors can be large and generally unknown. An assay has been developed, based on a previously published method, to measure the potential magnitude of the pool of PFAS precursor compounds (often referred to as PFAS “dark matter”) that may exist in contaminated soils and water. This presentation discusses this total oxidizable PFAS precursor assay using field sample examples and also examines its advantages and constraints.

Per- and polyfluoroalkyl substances (PFASs) have been identified at various release sites as compounds of interest. These compounds are considered emerging contaminants due to the rapidly evolving regulatory landscape associated with these parameters, as driven by advances in toxicology and human health risk assessment (HHRA) stemming from research in academia and government organizations. Internationally, researchers are actively assessing the toxicity of PFASs in a variety of species and exposure scenarios; however, the bulk of the published research to date focuses only on perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). A robust understanding of the current status of this research is required to evaluate the applicability and validity of various regulatory frameworks in the assessment of risk at release sites. This understanding is also needed to support the development of strategic approaches to addressing the risk.

This presentation will provide a survey of recent toxicological findings, bioaccumulation factors, human health screening levels, risk-driving pathways, and HHRA guidance related to PFASs, with a particular focus on the relevance of this information to guidance and regulatory frameworks in Canada. The review will cover recent toxicological studies and findings for PFASs from international academic and government research institutions, as well as approaches used for incorporating PFAS data, exposure scenarios, and toxicity values into HHRAs. Regulatory standards and guidelines for impacted media will also be reviewed and summarized.

PFAS have become one of the main emerging contaminant classes of focus in the public domain, mainly due to their widespread presence, persistence, bioaccumulative potential and toxicity. Their use has been documented in most sectors of the economy and at several federal sites. The approach to PFAS investigation is unique in view of their different properties compared to most conventional contaminants and considering the large number of Perfluoroalkyl Acids (PFAAs), precursors and breakdown products, the evolving regulatory environment, complex source compositions, fate and transport, as well as the potential effect of historical site remediation. Based on widespread usage and occurrence, it is expected that many sites may need to be investigated or re-opened to address potential risks associated with PFAS impacts and that this class of contaminants may become the critical path to achieve numerous site closures.

In view of the complexities associated with source composition, contaminant transport and PFAS distribution in the various environmental matrices, a novel visualization tool has been developed based on radar plots to analyze PFAS signatures. This is part of a multiple lines of evidence approach for PFAS site characterization and monitoring that has been developed.

The visualization tool was first used to compare specific PFAS signatures among various sites and differentiate multiple PFAS sources or background concentrations within the same site. The tool has been optimized to also allow for comparison of PFAS signatures in multiple investigation locations within the same site to illustrate how mixtures of PFAS can vary as a result of fate and transport (for example to map groundwater concentrations changes along the axis of a plume to assess compound-specific preferential transport) or to compare PFAS signatures in the same location between different environmental media to assess PFAS partitioning (soil vs. groundwater concentrations or surface water vs. sediment vs. fish tissue concentrations). Lastly the tool can also be used to assess variability of the PFAS signature over time at the same sampling locations as part of monitoring programs.

The presentation will show the applicability of the visualization tool for different PFAS sources (conventional and emerging) and environmental media, and demonstrate its successful application at various sites with primary focus on federal properties. We believe that this novel yet simple approach can assist site custodians, managers and federal departments with a better framework for characterization and monitoring of PFAS impacted sites.

Per- and Polyfluoroalkyl Substances (PFASs) are under investigation at various sites across the US where aqueous film forming foams (AFFF) have been used for fire protection. These sites are located in a wide variety of lithologic/hydrogeologic settings with varying Conceptual Site Models (CSMs) that can influence fate/transport (F&T) of PFASs. PFASs are biologically recalcitrant and highly soluble resulting in large dilute plumes and numerous impacts to drinking water systems. AFFF formulations include anionic, cationic, and zwitterionic PFASs and source areas are often comingled with other contaminants (e.g., petroleum hydrocarbons) at Fire Training Areas (FTAs) further complicating F&T. Surface water bodies downgradient from PFAS release areas have been contaminated with PFAS, but the relative contribution from groundwater transport versus surface flow and subsurface storm water flow is unclear. Sediment, pore-water and surface water downgradient from known PFAS releases are also consistently impacted by PFAS. PFAS has been found in fish tissue at concentrations suggesting significant bio-magnification. Long chain poly-fluorinated precursor compounds can biotransform under oxic/aerobic conditions into more heavily regulated PFASs including Perfluorooctanesulfonic acid (PFOS) and Perfluorooctanoic acid (PFOA) making dissolved oxygen/oxidation-reduction potential (DO/ORP) important parameters to consider when evaluating the potential for this biotransformation to occur. Patterns are emerging in the distribution, occurrence, persistence, and bio-magnification of PFAS.

This presentation presents the results of PFAS fate/transport evaluations conducted on a large portfolio of sites including the results of extraordinary F&T analytical testing for cation exchange capacity (CEC), Total organic Carbon (TOC), ph, and DO/ORP to assess their impact on F&T in source area soils. The evaluation explores the relationship between PFAS concentrations and key F&T parameters and considers whether correlations of these parameters can be made to plume length, peak concentrations, PFAS constituent transformations, and impacts to receptors. The resulting F&T hypothesis will inform site-specific CSM development and risk management strategies at PFAS impacted sites.

Due to an old firefighter training area, special attention is paid to the potential presence of poly- and perfluoroalkyl substances (PFAS) in the groundwater at CFB Bagotville. Applying the sampling protocols specific to these contaminants led us to modify the equipment used in the annual monitoring of the groundwater quality. In particular, the recommendation to proceed with a low flow sampling required the implementation of dual-valve pumps in several wells that are up to 100 metres deep. To reduce the risk of contaminating the samples submitted for lab analysis, modifying the pumps was necessary in order to eliminate certain components that contained PFAS. The numerous adjustments made not only effected the sampling material, but also the procedures and techniques used for collecting samples. This presentation will report on the different modifications made, the custom-made components and remaining questions.

Poly and perfluoroalkyl substances (PFAS) have been identified by many regulatory agencies as being compounds of concern within the environment. In recent years regulatory authorities have established a number of health-based values and evaluation standards with values for groundwater typically being less than 50 nanograms per litre. Contaminant studies suggest that the PFAS compounds are wide spread in the environment and are recalcitrant. Traditionally, impacted groundwater is extracted and treated on surface using media such as activated carbon and ion exchange resins. These treatment technologies are generally expensive and not efficient and can last for decades.

The application of in situ remedial technologies is common for a wide variety of compounds of concern however the application of in situ technologies for PFAS is just emerging. This field study involved the application of colloidal activated carbon at a site in Canada that the PFAS compounds perfluorooctanoate (PFOA) and perfluorooctane sulfonic acid (PFOS) were detected in the groundwater at concentrations up to 3,300 ng/L and 1,500 ng/L, respectively. The shallow silty sand aquifer was anaerobic in nature with groundwater flow being approximately 300 m/year. The colloidal activated carbon was applied using direct push technology resulting in the removal of the PFOA and PFOS to concentrations at or below the analytical detection limit over an 18-month period. Analysis of other PFAS also indicated that there were concentrations near or below the analytical detection limits. Detailed examination of cores taken post injection indicated that the colloidal activated carbon was successfully distributed within the impacted target zone with activated carbon being measured up to 5 m away from the point of injection. The results of the study suggest that colloidal activated carbon can be successfully applied to address low to moderated concentrations of PFAS within a shallow anaerobic aquifer.