Advanced reduction processes (ARPs) have demonstrated efficient degradation of poly- and perfluoroalkyl substances (PFAS). This paper describes the maturity level of more established ultraviolet ...(UV)-based ARPs, along with other reductive processes in the research stage. Commercial ARP vendors offer varying formats of UV-activated photosensitization of chemical additives to generate hydrated electrons in batch mode. These systems are typically coupled with preliminary separation processes and treat a concentrated PFAS waste stream. Other reduction approaches such as metal catalytic reduction have not yet left the academic space. Key areas of progress needed include cost-effective pretreatment approaches, and, relatedly, demonstration of ARPs in complex waste concentrates. Further improvement in reaction kinetics and developing an effective process for treating the most recalcitrant PFAS will also increase adoption of ARPs.
•ARPs have high potential in degrading and defluorinating PFAS in water.•Presently, only a few ARP processes are commercially available, all UV-based.•Owing to high energy cost, ARPs are used for treating low-flowrate PFAS concentrates.•Therefore, ARPs are coupled with other separation technics such as ion exchange.•Complete operating systems are all in the scale of <500 m3/day influent flow rates.
As per- and polyfluoroalkyl substances (PFAS) infiltrate the environment via industrial, commercial, and domestic sources, the demand for robust, cost-effective, and straightforward analytical assays ...intensifies to enhance PFAS characterization and quantification. To address this demand, this study introduces a novel UV-H2O2-TOP assay, identifying optimal parameters such as pH (5–9), oxidant concentration (500 mM H2O2), activation rate (63 mM H2O2 h−1), and an acceptable total organic carbon (TOC) limit (~1000 mg/L TOC) to achieve maximum PFAA precursor conversion. Additional work was performed further optimizing the UV-TOP assay, by confirming its superiority to heat activation, identifying the effectiveness of different persulfate salts, and investigating different concentrations of sodium persulfate and sodium hydroxide at a 1:2.5 ratio on PFCA yield. Our investigation concluded by applying the UV-H2O2-TOP assay, using sodium persulfate as the TOP assay oxidant, to 6:2 FTS and five different AFFF samples. High-resolution mass spectrometry and an expanded analytical suite support sample analysis, facilitating direct quantification of ultra-short chain perfluoroalkyl carboxylates (PFCAs) and common fluorotelomer compounds including 5:3/5:1:2 fluorotelomer betaine and 6:2 fluorotelomer sulfonamido betaine. Results highlight several advantages of this tandem UV-activated method, including enhanced preservation of perfluoroalkyl chains (post-oxidation of 6:2 fluorotelomer sulfonate resulted in 28 % PFHpA, 47 % PFHxA, 25 % C3–C5 PFCA), capacity to handle high TOC limits (1000 mg/L TOC), and ability to incorporate higher persulfate concentrations in a single oxidation cycle.
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•UV-activated H2O2 mineralizes up to ~1000 mg/L of total organic carbon.•Optimal parameters identified include pH (5–9) and oxidant concentration (500 mM H2O2).•Sodium persulfate identified as an effective alternative to potassium persulfate for the UV-TOP assay.•Tandem UV-H2O2-TOP assay demonstrates better preservation of longer PFCA chain lengths compared to thermal and UV-TOP.
Remediation technologies are urgently needed to degrade poly – and per fluoroalkyl substances (PFAS) in groundwater and soils. Since high energy electron beam (eBeam) technology involves rapid ...oxidation and reduction reactions it has the potential to breakdown PFAS. In this study, the technology was applied to PFAS-contaminated groundwater and soil samples to degrade PFOS and PFOA and other PFAS. An eBeam dose of 2000 kGy (kGy) reduced PFOS and PFOA concentrations in groundwater by 87.9% and 53.7% respectively. In soils with 10% moisture content, PFOS and PFOA concentrations were reduced by 99.9% and 86.5%, respectively. Out of 17 different PFAS that were detected in the soil sample, the 2000 kGy dose was able to degrade 10 PFAS to below detectable levels: PFNA (initially 19.4 ng/g), PFDA (3.9 ng/g), PFPeS (12.1 ng/g), PFHxS (365 ng/g), PFHpS (18.0 ng/g), PFNS (4.3 ng/g), 4:2 FTS (16.6 ng/g), 6:2 FTS (146.1 ng/g), 8:2 FTS (165.6 ng/g) and PFOSA (171.8 ng/g). Of the remaining 7 PFAS, the removal efficiency ranged between 49% and 99.9%. It appears that eBeam degradation of PFAS in soil is more effective at reduced soil moisture content.
•Remediation technologies needed for PFAS-contaminated soil and ground water.•2000 kGy eBeam dose achieved significant PFAS removal in soil and water.•Temperature increase associated with high doses involved in PFAS degradation.•Reduced soil moisture enhances PFAS remediation.
Poly- and perfluoroalkyl substances (PFASs) are a class of fluorinated chemicals that are utilized in firefighting and have been reported in groundwater and soil at several firefighter training ...areas. In this study, soil and groundwater samples were collected from across a former firefighter training area to examine the extent to which remedial activities have altered the composition and spatial distribution of PFASs in the subsurface. Log K oc values for perfluoroalkyl acids (PFAAs), estimated from analysis of paired samples of groundwater and aquifer solids, indicated that solid/water partitioning was not entirely consistent with predictions based on laboratory studies. Differential PFAA transport was not strongly evident in the subsurface, likely due to remediation-induced conditions. When compared to the surface soil spatial distributions, the relative concentrations of perfluorooctanesulfonate (PFOS) and PFAA precursors in groundwater strongly suggest that remedial activities altered the subsurface PFAS distribution, presumably through significant pumping of groundwater and transformation of precursors to PFAAs. Additional evidence for transformation of PFAA precursors during remediation included elevated ratios of perfluorohexanesulfonate (PFHxS) to PFOS in groundwater near oxygen sparging wells.
Sixty leading members of the scientific, engineering, regulatory, and legal communities assembled for the PFAS Experts Symposium in Arlington, Virginia on May 20 and 21, 2019 to discuss issues ...related to per‐ and polyfluoroalkyl substances (PFAS) based on the quickly evolving developments of PFAS regulations, chemistry and analytics, transport and fate concepts, toxicology, and remediation technologies. The Symposium created a venue for experts with various specialized skills to provide opinions and trade perspectives on existing and new approaches to PFAS assessment and remediation in light of lessons learned managing other contaminants encountered over the past four decades. The following summarizes several consensus points developed as an outcome of the Symposium:
Regulatory and policy issues: The response by many states and the US Environmental Protection Agency (USEPA) to media exposure and public pressure related to PFAS contamination is to relatively quickly initiate programs to regulate PFAS sites. This includes the USEPA establishing relatively low lifetime health advisory levels for PFAS in drinking water and even more stringent guidance and standards in several states. In addition, if PFAS are designated as hazardous substances at the federal level, as proposed by several Congressional bills, there could be wide‐reaching effects including listing of new Superfund sites solely for PFAS, application of stringent state standards, additional characterization and remediation at existing sites, reopening of closed sites, and cost renegotiation among PRPs.
Chemistry and analytics: PFAS analysis is confounded by the lack of regulatory‐approved methods for most PFAS in water and all PFAS in solid media and air, interference with current water‐based analytical methods if samples contain high levels of suspended solids, and sample collection and analytical interference due to the presence of PFAS in common consumer products, sampling equipment, and laboratory materials.
Toxicology and risk: Uncertainties remain related to human health and ecological effects for most PFAS; however, regulatory standards and guidance are being established incorporating safety factors that result in part per trillion (ppt) cleanup objectives. Given the thousands of PFAS that may be present in the environment, a more appropriate paradigm may be to develop toxicity criteria for groups of PFAS rather than individual PFAS.
Transport and fate: The recalcitrance of many perfluoroalkyl compounds and the capability of some fluorotelomers to transform into perfluoroalkyl compounds complicate conceptual site models at many PFAS sites, particularly those involving complex mixtures, such as firefighting foams. Research is warranted to better understand the physicochemical properties and corresponding transport and fate of most PFAS, of branched and linear isomers of the same compounds, and of the interactions of PFAS with other co‐contaminants such as nonaqueous phase liquids. Many PFAS exhibit complex transport mechanisms, particularly at the air/water interface, and it is uncertain whether traditional transport principles apply to the ppt levels important to PFAS projects. Existing analytical methods are sufficient when combined with the many advances in site characterization techniques to move rapidly forward at selected sites to develop and test process‐based conceptual site models.
Existing remediation technologies and research: Current technologies largely focus on separation (sorption, ion exchange, or sequestration). Due to diversity in PFAS properties, effective treatment will likely require treatment trains. Monitored natural attenuation will not likely involve destructive reactions, but be driven by processes such as matrix diffusion, sorption, dispersion, and dilution.
The consensus message from the Symposium participants is that PFAS present far more complex challenges to the environmental community than prior contaminants. This is because, in contrast to chlorinated solvents, PFAS are severely complicated by their mobility, persistence, toxicological uncertainties, and technical obstacles to remediation—all under the backdrop of stringent regulatory and policy developments that vary by state and will be further driven by USEPA. Concern was expressed about the time, expense, and complexity required to remediate PFAS sites and whether the challenges of PFAS warrant alternative approaches to site cleanups, including the notion that adaptive management and technical impracticability waivers may be warranted at sites with expansive PFAS plumes. A paradigm shift towards receptor protection rather than broad scale groundwater/aquifer remediation may be appropriate.
This study compared detection of perfluoroalkyl acids (PFAAs) in public drinking water with PFAA serum concentrations for 1566 California women. PFAA occurrence in drinking water from U.S. EPA’s ...third Unregulated Contaminant Monitoring Rule (UCMR3) database was linked by residential zip code to study participants. Detectable water concentrations of perfluorooctanoic acid (PFOA) ranged from 0.020 to 0.053 μg/L and of perfluorooctanesulfonic acid (PFOS) from 0.041 to 0.156 μg/L. Forty percent of detectable concentrations exceeded the 2016 Health Advisory Level of 0.07 μg/L for combined PFOA and PFOS concentrations. Serum concentrations of PFOS and PFOA significantly differed between participants with and without detectable measures of these compounds in water (Wilcoxon P ≤ 0.0007). Median serum concentrations of PFOS and PFOA were 29% and 38% higher, respectively, among those with detectable levels in water compared to those without detectable levels. Validation of this approach and replication of these results in other study populations are warranted.
Abstract
Sixty leading members of the scientific, engineering, regulatory, and legal communities assembled for the PFAS Experts Symposium in Arlington, Virginia on May 20 and 21, 2019 to discuss ...issues related to per‐ and polyfluoroalkyl substances (PFAS) based on the quickly evolving developments of PFAS regulations, chemistry and analytics, transport and fate concepts, toxicology, and remediation technologies. The Symposium created a venue for experts with various specialized skills to provide opinions and trade perspectives on existing and new approaches to PFAS assessment and remediation in light of lessons learned managing other contaminants encountered over the past four decades. The following summarizes several consensus points developed as an outcome of the Symposium:
Regulatory and policy issues: The response by many states and the US Environmental Protection Agency (USEPA) to media exposure and public pressure related to PFAS contamination is to relatively quickly initiate programs to regulate PFAS sites. This includes the USEPA establishing relatively low lifetime health advisory levels for PFAS in drinking water and even more stringent guidance and standards in several states. In addition, if PFAS are designated as hazardous substances at the federal level, as proposed by several Congressional bills, there could be wide‐reaching effects including listing of new Superfund sites solely for PFAS, application of stringent state standards, additional characterization and remediation at existing sites, reopening of closed sites, and cost renegotiation among PRPs.
Chemistry and analytics: PFAS analysis is confounded by the lack of regulatory‐approved methods for most PFAS in water and all PFAS in solid media and air, interference with current water‐based analytical methods if samples contain high levels of suspended solids, and sample collection and analytical interference due to the presence of PFAS in common consumer products, sampling equipment, and laboratory materials.
Toxicology and risk: Uncertainties remain related to human health and ecological effects for most PFAS; however, regulatory standards and guidance are being established incorporating safety factors that result in part per trillion (ppt) cleanup objectives. Given the thousands of PFAS that may be present in the environment, a more appropriate paradigm may be to develop toxicity criteria for groups of PFAS rather than individual PFAS.
Transport and fate: The recalcitrance of many perfluoroalkyl compounds and the capability of some fluorotelomers to transform into perfluoroalkyl compounds complicate conceptual site models at many PFAS sites, particularly those involving complex mixtures, such as firefighting foams. Research is warranted to better understand the physicochemical properties and corresponding transport and fate of most PFAS, of branched and linear isomers of the same compounds, and of the interactions of PFAS with other co‐contaminants such as nonaqueous phase liquids. Many PFAS exhibit complex transport mechanisms, particularly at the air/water interface, and it is uncertain whether traditional transport principles apply to the ppt levels important to PFAS projects. Existing analytical methods are sufficient when combined with the many advances in site characterization techniques to move rapidly forward at selected sites to develop and test process‐based conceptual site models.
Existing remediation technologies and research: Current technologies largely focus on separation (sorption, ion exchange, or sequestration). Due to diversity in PFAS properties, effective treatment will likely require treatment trains. Monitored natural attenuation will not likely involve destructive reactions, but be driven by processes such as matrix diffusion, sorption, dispersion, and dilution.
The consensus message from the Symposium participants is that PFAS present far more complex challenges to the environmental community than prior contaminants. This is because, in contrast to chlorinated solvents, PFAS are severely complicated by their mobility, persistence, toxicological uncertainties, and technical obstacles to remediation—all under the backdrop of stringent regulatory and policy developments that vary by state and will be further driven by USEPA. Concern was expressed about the time, expense, and complexity required to remediate PFAS sites and whether the challenges of PFAS warrant alternative approaches to site cleanups, including the notion that adaptive management and technical impracticability waivers may be warranted at sites with expansive PFAS plumes. A paradigm shift towards receptor protection rather than broad scale groundwater/aquifer remediation may be appropriate.
Perfluoroalkyl acids (PFAAs) are used to impart oil- and water-repellant and surfactant properties to numerous products, and they are among the most persistent chemicals to ever enter commerce. PFAAs ...are detected in the blood of humans all over the world. The two 8-carbon PFAAs, perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS), have been associated with a number of adverse health outcomes. In this research, a new oxidation-based technique of PFAA precursor measurement was developed for aqueous and solid samples. Along with other analytical tools, this precursor assay was used to gain insight into the occurrence and fate of PFAA precursors in two sources: urban runoff and soil and groundwater impacted by firefighting materials known as aqueous film forming foams (AFFF). The occurrence of PFAA precursors in urban runoff was investigated to determine the extent to which runoff could serve as a source of PFAAs to drinking water supplies during storage in aquifers or reservoirs. An indirect technique of measuring PFAA precursors was developed for urban runoff samples by exposing samples to a high concentration of hydroxyl radicals and converting precursors to measureable perfluorinated carboxylate products (Chapter 2). By comparing perfluorinated carboxylate concentrations before and after oxidation, the total concentration of PFAA precursors was inferred. Analysis of thirty-three urban runoff samples collected from locations around the San Francisco Bay, CA indicated that C8 forms of PFAAs and C6 forms of PFAA precursors were predominant in runoff. The assay demonstrated that commonly measured PFAA precursors represented only a small fraction (<25%) of the total concentration of precursors present in runoff, confirming the utility of the precursor assay. To assess the persistence of AFFF-derived PFAA precursors, groundwater, soil, and aquifer solids were obtained in 2011 from an unlined firefighter training area at a U.S. Air Force Base where AFFF was regularly used between 1970 and 1990 (Chapter 3). To measure the total concentration of PFAA precursors in archived AFFF formulations and AFFF-impacted environmental samples, the oxidation-based assay developed in Chapter 2 was adapted for these media. This precursor assay was employed along with direct measurement of twenty-two precursors found in AFFF and a suite of other poly- and perfluoroalkyl substances (PFASs). On a molar basis, precursors accounted for 41% to 100% of the total concentration of PFASs in archived AFFF formulations. In the training area, precursors measured by the precursor assay accounted for an average of 23% and 28% of total PFASs in groundwater and solids samples, respectively. Thus, much of the mass of precursors released at the site appeared to be converted to perfluorinated carboxylates and sulfonates over a residence time of twenty years or more. In order to elucidate the conditions most amenable to AFFF-derived PFAA precursor transformation, microcosms were constructed with soil and sediment inocula and were incubated under different redox conditions with two different types of AFFF (Chapter 4). Live microcosms amended with AFFF manufactured by 3M demonstrated an ability to utilize the carbon in AFFF, but no changes in PFAS concentrations were observed over 60- to 90-day incubation periods. The main precursor in AFFF manufactured by Ansul, 6:2 fluorotelomer thioamido sulfonate (6:2 FtTAoS), was transformed in both aerobic and anaerobic live incubations. Application of the precursor assay to microcosm slurries suggested that all unquantifiable biological transformation products under aerobic conditions were partitioned to the microcosm slurry. In the anaerobic microcosms, the precursor assay indicated that unidentified biological transformation products were either sufficiently volatile to leave the slurry or unable to be oxidized to perfluorinated carboxylates. Transformation products reported in soil and groundwater beneath many U.S. military firefighter training areas (Chapter 3) are consistent with the aerobic transformation products observed in Ansul AFFF-amended microcosm. (Abstract shortened by UMI.)
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