Concentrating Per- and Polyfluoroalkyl Substances (PFAS) in Municipal Solid Waste Landfill Leachate Using Foam Separation

Cationic surfactant-assisted foam fractionation enhances the removal of short-chain perfluoroalkyl substances from impacted water

Several studies have demonstrated that air-bubbling and foam fractionation techniques can efficiently remove long-chain PFAS from contaminated water. However, removing short-chain PFAS is challenging due to its lower surface activity and inability to form self-assembly structures at the air-water interface. In this study, we tested various additives, including salts, surfactants, and polymers, to improve short-chain PFAS (e.g., perfluorobutanesulfonic acid (PFBS) and perfluorobutanoic acid (PFBA)) removal in non-foaming solutions using a bench-scale system. We found that in the presence of cetyltrimethylammonium chloride (CTAC) and salt, air-bubbling can significantly remove 0.5 μg L-1 of PFBS and PFBA in deionized water by >99% (15 min) and 81% (60 min), respectively. The decline of surface tension and the formation of thin foam-like layers during bubbling, controlled by the concentration of CTAC, significantly improved the removal of short-chain PFAS. Adding anionic and neutral surfactants showed no removal of short-chain PFAS during bubbling, suggesting the importance of the electrostatic interactions between short-chain PFAS and the cationic CTAC. We observed a 1:1 M ratio between CTAC and PFBS removed from the solution, suggesting the formation of ion pairs in the solution and enhancing the surface activity of the overall neutral (PFAS-CTAC) complex. A mass balance of the system revealed that the primary mechanism by which PFAS was removed from non-foaming waters was through aerosol generation (70-100%). Using the optimized condition, PFAS mixtures (short- and long-chain PFAS, including five recently regulated PFAS by USPEA, 2 nM each) in deionized water and natural groundwater were successfully removed to below detection (>99% removal; <2 ng L-1), except for PFBA (25-73% removal). These results provide an improved understanding of the mechanism by which PFAS is removed during foam fractionation and highlight the need for capturing aerosols enriched with PFAS to prevent secondary contamination.

A critical review of biochar for the remediation of PFAS-contaminated soil and water

Per- and polyfluoroalkyl substances (PFAS) present significant environmental and health hazards due to their inherent persistence, ubiquitous presence in the environment, and propensity for bioaccumulation. Consequently, the development of efficacious remediation strategies for soil and water contaminated with PFAS is imperative. Biochar, with its unique properties, has emerged as a cost-effective adsorbent for PFAS. Despite this, a comprehensive review of the factors influencing PFAS adsorption and immobilization by biochar is lacking. This narrative review examines recent findings indicating that the application of biochar can effectively immobilize PFAS, thereby mitigating their environmental transport and subsequent ecological impact. In addition, this paper reviewed the sorption mechanisms of biochar and the factors affecting its sorption efficiency. The high effectiveness of biochars in PFAS remediation has been attributed to their high porosity in the right pore size range (>1.5 nm) that can accommodate the relatively large PFAS molecules (>1.02-2.20 nm), leading to physical entrapment. Effective sorption requires attraction or bonding to the biochar framework. Binding is stronger for long-chain PFAS than for short-chain PFAS, as attractive forces between long hydrophobic CF2-tails more easily overcome the repulsion of the often-anionic head groups by net negatively charged biochars. This review summarizes case studies and field applications highlighting the effectiveness of biochar across various matrices, showcasing its strong binding with PFAS. We suggest that research should focus on improving the adsorption performance of biochar for short-chain PFAS compounds. Establishing the significance of biochar surface electrical charge in the adsorption process of PFAS is necessary, as well as quantifying the respective contributions of electrostatic forces and hydrophobic van der Waals forces to the adsorption of both short- and long-chain PFAS. There is an urgent need for validation of the effectiveness of the biochar effect in actual environmental conditions through prolonged outdoor testing.

Analysis of ammonia-nitrogen removal kinetics by stage in pilot scale vertical flow wetlands treating landfill leachate in series

This study explored the effect stage number and plant type have on ammonia-nitrogen (NH3-N) removal kinetics in a two-stage pilot-scale vertical flow constructed wetland (VFCW) system treating landfill leachate. Half of the VFCW columns were planted with Typha latifolia and the other half Scirpus californicus, and half of the columns were loaded with municipal solid waste landfill leachate (diluted to 1 part leachate to 2 parts total) with the effluent from these columns was collected in two separate barrels. The remaining columns were loaded with the effluent collected from the first columns, creating a two-stage VFCW system with four unique pairs to be tested. The leachate used here experienced no prior pre-treatment, and average influent concentrations of NH3-N for the first- and second-stage VFCWs were 508 and 321 mg L-1, respectively- much higher than many other VFCW treatment systems. Some reduction in chemical oxygen demand was observed, as well as generation of nitrate and nitrite, evidence of nitrification. No apparent correlation between aboveground biomass and removal of NH3-N was observed. Overall removal efficiency of NH3-N through two stages of VFCWs was 53.7% for columns planted with T. latifolia and 58.3% for those planted with S. Californicus. Average NH3-N removal efficiencies for the first stage VFCWs were 32.7% and 34.3%, while those in the second stage were 31.3% and 36.5%; no significant difference was observed between the first and second stage, suggesting that stage number does not have a significant effect on the removal efficiency of NH3-N in the primary treatment of landfill leachate via VFCWs. However, average mass removal rates of NH3-N in the first stage were 166 and 175 mg L-1 d-1; the second stage was significantly lower at 99.4 and 112 mg L-1 d-1, indicating that the first stage removed more pollutants overall.

Characterization of per- and polyfluoroalkyl substances (PFAS) and other constituents in MSW landfill leachate from Puerto Rico

Elevated per- and polyfluoroalkyl substance (PFAS) concentrations have been reported in municipal solid waste (MSW) landfill leachate with higher levels in wet and warmer subtropical climates. Information about landfill leachate characteristics is much more limited in tropical climates. In this study, 20 landfill leachate samples were collected from three MSW landfills on the tropical island of Puerto Rico and results were compared against landfills nationally and within Florida, USA. The samples collected in Puerto Rico underwent physical-chemical analysis, as well as a quantitative analysis of 92 PFAS. Samples described in this study include discrete leachate types, such as leachate, gas condensate, and leachate which has undergone on-site treatment (e.g., RO treatment, phytoremediation, lagoons). A total of 51 PFAS were detected above quantitation limits, including perfluorohexylphosphonic acid, a perfluoroalkyl acid (PFAA) which has not been reported previously in landfill leachate. ∑PFAS concentrations in this study (mean: 38,000 ng L-1), as well as concentrations of individual PFAS, are significantly higher than other reported MSW landfill leachate concentrations. The profiles of leachates collected from on-site treatment systems indicate possible transformation of precursor PFAS as a result of treatment processes - oxidizing conditions, for example, may facilitate aerobic transformation, increase the concentrations of PFAAs, and possibly increase the apparent ∑PFAS concentration. Extreme climate events, including rising temperatures and more frequent hurricanes, have placed additional strain on the solid waste management infrastructure on the island - adding complexity to an already challenging PFAS management issue. As concern grows over PFAS contamination in drinking water, these findings should inform solid waste and leachate management decisions in order to minimize PFAS emissions in island environments.

The role of suspended biomass in PFAS enrichment in wastewater treatment foams

Foaming in aerated bioreactors at wastewater treatment plants (WWTPs) has been identified as an operational issue for decades. However, the affinity of per- and polyfluoroalkyl substances (PFAS) for air-liquid interfaces suggests that foam harvesting has the potential to become a sustainable method for PFAS removal from sewage. Aerated bioreactors' foams are considered three-phase systems, comprising air, aqueous and solid components, the latter consisting of activated sludge biomass. To achieve a comprehensive understanding of the capability of aerated bioreactors' foams to enrich PFAS, we analysed PFAS concentrations from WWTPs in both the solid and aqueous phases of the collapsed foams (foamate) and underlying bulk mixed liquors. Our findings show that PFAS enrichment occurs not only in the aqueous phase but also in the solid phase of the foamate. This suggests that previous field studies that only analysed the aqueous phase may have underestimated the capability of the aerated bioreactors' foams to enrich PFAS. Fractions of PFOA and PFOS sorbed to the solid phase of the foamate can be as high as 60 % and 95 %, respectively. Our findings highlight the importance of implementing effective foamate management strategies that consider both the aqueous and solid phases.

Macronutrient and PFOS bioavailability manipulated by aeration-driven rhizospheric organic nanocapsular assembly

Ubiquitous presence of the extremely persistent pollutants, per- and polyfluoroalkyl substances, is drawing ever-increasing concerns for their high eco-environmental risks which, however, are insufficiently considered based on the assembly characteristics of those amphiphilic molecules in environment. This study investigated the re-organization and self-assembly of perfluorooctane sulfonate (PFOS) and macronutrient molecules from rhizospheric organic (RhO) matter induced with a common operation of aeration. Atomic force microscopy (AFM) with infrared spectroscopy (IR)-mapping clearly showed that, after aeration and stabilization, RhO nanocapsules (∼ 1000 nm or smaller) with a core of PFOS-protein complexes coated by "lipid-carbohydrate" layers were observed whereas the capsule structure with a lipid core surrounded by "protein-carbohydrate-protein" multilayers was obtained in the absence of PFOS. It is aeration that exerted the disassociation of pristine RhO components, after which the environmental concentration PFOS restructured the self-assembly structure in a conspicuous "disorder-to-order" transition. AFM IR-mapping analysis of faeces combined with quantification of component uptake denoted the decreased ingestion and utilization of both PFOS and proteins compared with lipids and carbohydrates when Daphnia magna were fed with RhO nanocapsules. RhO nanocapsules acted as double-edged swords via simultaneously impeding the bioaccessibility of hazardous PFOS molecules and macronutrient proteins; and the latter might be more significant, which caused a malnutrition status within merely 48 h. Elucidating the assembly structure of natural organic matter and environmental concentration PFOS, the finding of this work could be a crucial supplementation to the high-dose-dependent eco-effect investigations on PFOS.

A review of foam fractionation for the removal of per- and polyfluoroalkyl substances (PFAS) from aqueous matrices

The detection of per- and polyfluoroalkyl substances (PFAS) in aqueous matrices is an emerging environmental concern due to their persistent, bioaccumulative and toxic properties. Foam fractionation has emerged as a viable method for removing and concentrating PFAS from aqueous matrices. The method exploits the surface-active nature of the PFAS to adsorb at the air-liquid interfaces of rising air bubbles, resulting in foam formation at the top of a foam fractionator. The removal of PFAS is then achieved through foam harvesting. Foam fractionation has gained increasing attention owing to its inherent advantages, including simplicity and low operational costs. The coupling of foam fractionation with destructive technologies could potentially serve as a comprehensive treatment train for future PFAS management in aqueous matrices. The PFAS-enriched foam, which has a smaller volume, can be directed to subsequent destructive treatment technologies. In this review, we delve into previous experiences with foam fractionation for PFAS removal from various aqueous matrices and critically analyse their key findings. Then, the recent industry advancements and commercial projects that utilise this technology are identified. Finally, future research needs are suggested based on the current challenges.

Assessing construction and demolition wood-derived biochar for in-situ per- and polyfluoroalkyl substance (PFAS) removal from landfill leachate

With regulations for per-and polyfluoroalkyl substances (PFAS) impending, the abundance of these chemicals of emerging concern in municipal solid waste (MSW) landfill leachate increasingly challenges landfill operators to seek on-site leachate pre-treatment options. This two-staged study explores the potential reuse of biochar derived from construction and demolition debris (CDD) wood as an in-situ PFAS sorbent for application within MSW landfill leachate collection systems. Batch leaching tests were first used to examine the feasibility of capturing PFAS from landfill leachate using two sources of CDD-wood-derived biochar. Then, columns were used to test the in-situ sorption capabilities of the same biochars under simulated landfill conditions. All leachates were characterized for pH, chemical oxygen demand, ammonia-nitrogen, and 92 PFAS. Seventeen PFAS were detected in the batch leaching experiment, and nine PFAS were detected in column leachates. In the batch leaching scenario, Biochar 1 achieved a maximum of 29% PFAS reduction compared to controls. Columns containing Biochar 1 generated leachates with PFAS concentrations 50% to 80% higher than those in control columns for the duration of the experiment. Columns containing Biochar 2 generated leachates with PFAS concentrations 44% less than controls in week 1 and similar concentrations in weeks 2, 3, and 4. In this study, PFAS removal from landfill leachate using biochar derived from CDD wood was not significant. Further research on biochar derived from CDD wood is needed before it can be recommended as an in-situ landfill leachate pre-treatment method.

Combination of separation and degradation methods after PFAS soil washing

The current study evaluated a three-stage treatment to remediate PFAS-contaminated soil. The treatment consisted of soil washing, foam fractionation (FF), and electrochemical oxidation (EO). The possibility of replacing the third stage, i.e., EO, with an adsorption process was also assessed. The contamination in the studied soils was dominated by perfluorooctane sulfonate (PFOS), with a concentration of 760 and 19 μg kg-1 in soil I and in soil II, accounting for 97 % and 70 % of all detected per-and polyfluoroalkyl substances (PFAS). Before applying a pilot treatment of soil, soil washing was performed on a laboratory scale, to evaluate the effect of soil particle size, initial pH and a liquid-to-soil ratio (L/S) on the leachability of PFAS. A pilot washing system generated soil leachate that was subsequently treated using FF and EO (or adsorption) and then reused for soil washing. The results indicated that the leaching of PFAS occurred easier in 0.063-1 mm particles than in the soil particles having a size below 0.063 mm. Both alkaline conditions and a continual replacement of the leaching solution increased the leachability of PFAS. The analysis using one-way ANOVA showed no statistical difference in means of PFOS washed out in laboratory and pilot scales. This allowed estimating twenty washing cycles using 120 L water to reach 95 % PFOS removal in 60 kg soil. The aeration process removed 95-99 % PFOS in every washing cycle. The EO and adsorption processes achieved similar results removing up to 97 % PFOS in concentrated soil leachate. The current study demonstrated a multi-stage treatment as an effective and cost-efficient method to permanently clean up PFAS-contaminated soil.

A critical review of perfluoroalkyl and polyfluoroalkyl substances (PFAS) landfill disposal in the United States

Landfills manage materials containing per- and polyfluoroalkyl substances (PFAS) from municipal solid waste (MSW) and other waste streams. This manuscript summarizes state and federal initiatives and critically reviews peer-reviewed literature to define best practices for managing these wastes and identify data gaps to guide future research. The objective is to inform stakeholders about waste-derived PFAS disposed of in landfills, PFAS emissions, and the potential for related environmental impacts. Furthermore, this document highlights data gaps and uncertainties concerning the fate of PFAS during landfill disposal. Most studies on this topic measured PFAS in liquid landfill effluent (leachate); comparatively fewer have attempted to estimate PFAS loading in landfills or other effluent streams such as landfill gas (LFG). In all media, the reported total PFAS heavily depends on waste types and the number of PFAS included in the analytical method. Early studies which only measured a small number of PFAS, predominantly perfluoroalkyl acids (PFAAs), likely report a significant underestimation of total PFAS. Major findings include relationships between PFAS effluent and landfill conditions - biodegradable waste increases PFAS transformation and leaching. Based on the results of multiple studies, it is estimated that 84% of PFAS loading to MSW landfills (7.2 T total) remains in the waste mass, while 5% leaves via LFG and 11% via leachate on an annual basis. The environmental impact of landfill-derived PFAS has been well-documented. Additional research is needed on PFAS in landfilled construction and demolition debris, hazardous, and industrial waste in the US.

Hydrothermal Alkaline Treatment (HALT) of Foam Fractionation Concentrate Derived from PFAS-Contaminated Groundwater

While foam fractionation (FF) process has emerged as a promising technology for removal of per- and polyfluoroalkyl substances (PFASs) from contaminated groundwater, management of the resulting foam concentrates with elevated concentrations of PFASs (e.g., >1 g/L) remains a challenge. Here, we applied hydrothermal alkaline treatment (HALT) to two foam concentrates derived from FF field demonstration projects that treated aqueous film-forming foam (AFFF)-impacted groundwater. Results showed >90% degradation and defluorination within 90 min of treatment (350 °C, 1 M NaOH) of all 62 PFASs (including cations, anions, and zwitterions) identified in foam concentrates. Observed rate constants for degradation of individual perfluoroalkyl sulfonates (PFSAs, CnF2n+1-SO3-), the most recalcitrant class of PFASs, in both foam concentrates were similar to values measured previously in other aqueous matrices, indicating that elevated initial PFAS concentrations (e.g., PFHxSinit = 0.55 g/L), dissolved organic carbon (DOC; up to 4.5 g/L), and salt levels (e.g., up to 325 mg/L chloride) do not significantly affect PFAS reaction kinetics. DOC was partially mineralized by treatment, but a fraction (∼15%) was recalcitrant. Spectroscopic characterization revealed molecular features of the HALT-recalcitrant DOC fraction, and nontarget high-resolution mass spectrometry tentatively identified 129 nonfluorinated HALT-recalcitrant molecules. Analysis of process energy requirements shows that treating PFAS-contaminated foam concentrates with HALT would add minimally (<5%) to the overall energy requirements of an integrated FF-HALT treatment train.

Foam fractionation and electrochemical oxidation for the treatment of per- and polyfluoroalkyl substances (PFAS) in environmental water samples

Treatment of waters contaminated by per- and polyfluoroalkyl substances (PFAS) in large volumes remains a challenge to date. Treatment trains comprising separation and destruction technologies are promising to manage PFAS contamination. Foam fractionation (FF) and electrochemical oxidation (EO) are two cost-effective technologies for PFAS separation and destruction, respectively. This work systematically explored the performance of a treatment train of FF followed by EO (FF-EO) for treating PFAS in environmental water samples. For each treatment step, the dependence of the treatment performance on operational factors and other variables were analyzed statistically. The statistical analysis revealed PFAS enrichment and removal depend significantly on PFAS carbon chain length, solution conductivity, and PFAS concentration. Whether FF-EO treatment costs less energy than direct EO without FF mainly relies upon PFAS carbon chain length and TOC content in the sample. Both correlations were found to be linear. For all environmental water samples in this study, FF-EO is more energy-efficient than EO alone.

Target and Suspect Screening Integrated with Machine Learning to Discover Per- and Polyfluoroalkyl Substance Source Fingerprints

This study elucidates per- and polyfluoroalkyl substance (PFAS) fingerprints for specific PFAS source types. Ninety-two samples were collected from aqueous film-forming foam impacted groundwater (AFFF-GW), landfill leachate, biosolids leachate, municipal wastewater treatment plant effluent (WWTP), and wastewater effluent from the pulp and paper and power generation industries. High-resolution mass spectrometry operated with electrospray ionization in negative mode was used to quantify up to 50 target PFASs and screen and semi-quantify up to 2,266 suspect PFASs in each sample. Machine learning classifiers were used to identify PFASs that were diagnostic of each source type. Four C5-C7 perfluoroalkyl acids and one suspect PFAS (trihydrogen-substituted fluoroethernonanoic acid) were diagnostic of AFFF-GW. Two target PFASs (5:3 and 6:2 fluorotelomer carboxylic acids) and two suspect PFASs (4:2 fluorotelomer-thia-acetic acid and N-methylperfluoropropane sulfonamido acetic acid) were diagnostic of landfill leachate. Biosolids leachates were best classified along with landfill leachates and N-methyl and N-ethyl perfluorooctane sulfonamido acetic acid assisted in that classification. WWTP, pulp and paper, and power generation samples contained few target PFASs, but fipronil (a fluorinated insecticide) was diagnostic of WWTP samples. Our results provide PFAS fingerprints for known sources and identify target and suspect PFASs that can be used for source allocation.

Management of per- and polyfluoroalkyl substances (PFAS)-laden wastewater sludge in Maine: Perspectives on a wicked problem

This article discusses the challenges and potential solutions for managing wastewater sludge that contains per- and polyfluoroalkyl substances (PFAS), using the experience in Maine as a guide toward addressing the issue nationally. Traditional wastewater treatment, designed to remove excess organic waste and nutrients, does not eliminate persistent toxic pollutants like PFAS, instead partitioning the chemicals between discharged effluent and the remaining solids in sludge. PFAS chemistry, the molecular size, the alkyl chain length, fluorine saturation, the charge of the head group, and the composition of the surrounding matrix influence PFAS partitioning between soil and water. Land application of sludge, incineration, and storage in a landfill are the traditional management options. Land application of Class B sludge on agricultural fields in Maine peaked in the 1990s, totaling over 2 × 106 cu yd over a 40-year period and has contaminated certain food crops and animal forage, posing a threat to the food supply and the environment. Additional Class A EQ (Exceptional Quality) composted sludge was also applied to Maine farmland. The State of Maine banned the land application of wastewater sludge in August 2022. Most sludge was sent to the state-owned Juniper Ridge Landfill, which accepted 94 270 tons of dewatered sludge in 2022, a 14% increase over 2019. Between 2019 and 2022, the sum of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) concentrations in sludge sent to the landfill ranged from 1.2 to 104.9 ng/g dw. In 2022, the landfill generated 71.6 × 106 l of leachate. The concentration of sum of six PFAS in the leachate increased sixfold between 2021 and 2022, reaching 2 441 ng/l. The retention of PFAS within solid-waste landfills and the potential for long-term release of PFAS through liners into groundwater require ongoing monitoring. Thermal treatment, incineration, or pyrolysis can theoretically mineralize PFAS at high temperatures, yet the strong C-F bond and reactivity of fluorine require extreme temperatures for complete mineralization. Future alternatives may include interim options such as preconditioning PFAS with nonpolar solvents prior to immobilization in landfills, removing PFAS from leachate, and interrupting the cycle of PFAS moving from landfill, via leachate, to wastewater treatment, and then back to the landfill via sludge. Long-term solutions may involve destructive technologies such as electron beam irradiation, electrochemical advanced oxidation, or hydrothermal liquefaction. The article highlights the need for innovative and sustainable solutions for managing PFAS-contaminated wastewater sludge.

Molecular Dynamics Simulation Prediction of the Partitioning Constants (KH, Kiw, Kia) of 82 Legacy and Emerging Organic Contaminants at the Water-Air Interface

The tendency of organic contaminants (OCs) to partition between different phases is a key set of properties that underlie their human and ecological health impacts and the success of remediation efforts. A significant challenge associated with these efforts is the need for accurate partitioning data for an ever-expanding list of OCs and breakdown products. All-atom molecular dynamics (MD) simulations have the potential to help generate these data, but existing studies have applied these techniques only to a limited variety of OCs. Here, we use established MD simulation approaches to examine the partitioning of 82 OCs, including many compounds of critical concern, at the water-air interface. Our predictions of the Henry's law constant (K_H) and interfacial adsorption coefficients (K_iw, K_ia) correlate strongly with experimental results, indicating that MD simulations can be used to predict K_H, K_iw, and K_ia values with mean absolute deviations of 1.1, 0.3, and 0.3 logarithmic units after correcting for systematic bias, respectively. A library of MD simulation input files for the examined OCs is provided to facilitate future investigations of the partitioning of these compounds in the presence of other phases.

Degradation of per- and polyfluoroalkyl substances in landfill leachate by a thin-water-film nonthermal plasma reactor

Per- and polyfluoroalkyl substances (PFAS) are present in landfill leachate, posing potential challenges to leachate disposal and treatment. This work represents the first study of a thin-water-film nonthermal plasma reactor for PFAS degradation in landfill leachate. Of the 30 PFAS measured in three raw leachates, 21 were above the detection limits. The removal percentage depended on the category of PFAS. For example, perfluorooctanoic acid PFOA (C8) had the highest removal percentage (77% as an average of the three leachates) of the perfluoroalkyl carboxylic acids (PFCAs) category. The removal percentage decreased when the carbon number increased from 8 to 11 and decreased from 8 to 4. The effects of various landfill leachate components, including sodium chloride, acetate, humic acids, pH, and surfactants, had no or minor impacts (<30%) on PFOA mineralization in synthetic samples. This might be explained by the plasma-generation and PFAS-degradation mainly occurring at the gas/liquid interface. Shorter-chain PFCAs were produced as intermediates of PFOA degradation, and shorter-chain PFCAs and perfluorosulfonic acids (PFSAs) were produced as intermediates of perfluorooctanesulfonic acid (PFOS). The concentrations of the intermediates decreased with decreasing carbon number, suggesting a stepwise removal of difluoromethylene (CF₂) in the degradation pathway. Potential PFAS species in the raw and treated leachates were identified at the molecular level through non-targeted Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The intermediates did not show accurate toxicity per Microtox bioassay.

Behavior of Per- and polyfluoroalkyl substances (PFAS) in Pilot-Scale vertical flow constructed wetlands treating landfill leachate

This study investigated the behavior of per- and polyfluoroalkyl substances (PFAS) in multiple pilot-scale vertical flow constructed wetlands (VFCW) treating landfill leachate. Eight pilot-scale VFCW columns planted with Typha latifolia or Scirpus Californicus were fed untreated municipal solid waste (MSW) landfill leachate that was diluted with potable water at a 1:10 ratio (1 part leachate to 10 parts total) at a fixed daily hydraulic loading rate of 0.525 m d^-1. Ninety-two PFAS were examined and 18 PFAS were detected at quantifiable concentrations (7 precursor species and 11 terminal species). The average concentration of Σ₉₂ PFAS in the influent was 3,100 ng L^-1, which corresponded with minimal reduction in the effluents from the four VFCW (decreases ranged from 1% to 12% on average for Σ₁₈ PFAS); however, precursors 6:3 FTCA, 7:3 FTCA, N-MeFOSAA, and N-EtFOSAA concentrations decreased significantly in the VFCW effluents, and significant decreases in the concentrations of these PFAA-precursors were concurrent with a significant increase in concentrations of five PFAAs (PFBA, PFNA, PFBS, PFOS, and PFOSI). This trend indicates that from a regulatory perspective, standalone VFCWs are likely to produce an apparent PFAS increase, which may also be true for many other leachate treatment processes incorporating aerobic biological treatment. Additional treatment to address PFAS should be integrated prior to the use of any system, including VFCWs, for the treatment of constituents of concern in MSW landfill leachate.

Per- and polyfluoroalkyl substances (PFAS) distribution in landfill gas collection systems: leachate and gas condensate partitioning

While per- and polyfluoroalkyl substances (PFAS) have been reported extensively in municipal solid waste (MSW) landfill leachate,they have rarely been quantified in landfill gas or in discrete landfill liquids such as landfill gas condensate (LGC), and the potential for PFAS to partition to the condensate has not been reported. LGC and leachate collected from within gas wells known as gas well pump-out (GWP) from three MSW landfills underwent physical-chemical characterization and PFAS analysis to improve understanding of the conditions under which these liquids form and to illuminate PFAS behavior within landfills. LGC was observed to be clear liquid containing ammonia and alkalinity while GWP strongly resembled leachate - dark in color, high in chloride and ammonia. Notably, arsenic and antimony were found in concentrations exceeding regulatory thresholds by over two orders of magnitude in many LGC samples. LGC contained a lower average concentration of ΣPFAS (19,000 ng L) compared to GWP (56,000 ng L); however, LGC contained more diversity of PFAS, with 53 quantified compared to 44 in GWP. LGC contained proportionally more precursor PFAS than GWP, including more semi-volatile PFAS which are rarely measured in water matrices, such as fluorotelomer alcohols and perfluoroalkane sulfonamido ethanols. This study provides the first detailed comparison of these matrices to inform timely leachate management decisions.

Drinking water nanofiltration with concentrate foam fractionation-A novel approach for removal of per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are recognized as persistent pollutants that have been found in drinking water sources on a global scale. Semi-permeable membrane treatment processes such as reverse osmosis and nanofiltration (NF) have been shown effective at removing PFAS, however, disposal of PFAS laden concentrate is problematic. Without treatment of the concentrate, PFAS is released into the environment. The present work examined a novel PFAS removal scheme for drinking water using NF filtration with treatment of the resulting NF concentrate via foam fractionation (FF) with and without co-surfactants. The NF-pilot removed 98% of PFAS from AFFF contaminated groundwater producing permeate with 1.4 ng L^-1 total PFAS. Using FF resulted in ∑PFAS removal efficiency of 90% from the NF concentrate and with improved removal of 94% with addition of cationic co-surfactant. The resulting foamate composed approximately 2% of the NF feedwater volume and contained greater than 3000 ng L^-1 PFAS or 41 times greater than the NF feedwater. Addition of the cationic co-surfactant to the FF process resulted in increased removal efficiency of the shorter chain PFAS, specifically 37% for PFPeA, 9% for PFHxA, and 34% for PFBS thus attaining 59%, 99% and 96% removal efficiency, respectively. PFOA, PFPeS, PFHxS, PFOS each attained 99% FF removal with or without co-surfactant addition.

A critical review of the occurrence, fate and treatment of per- and polyfluoroalkyl substances (PFASs) in landfills

The aim of this critical review is i) to summarize the occurrence of Per- and polyfluoroalkyl substances (PFASs) in landfills; ii) to outline the environmental fate and transport of PFASs in landfills; iii) to compare the treatment technologies of PFASs in landfill leachate and remediation methods of PFASs in surrounding groundwater; iv) to identify the research gaps and suggest future research directions. In recent years, PFASs have been detected in landfills around the world, among which Perfluoroalkyl acids (PFAAs) especially Perfluorooctanoic acid (PFOA) and Perfluorooctane sulfonic acid (PFOS) are mostly studied due to their long-term stability. Short-chain PFASs (<8 carbons) are more common than long-chain PFASs (≧8 carbons) in landfill leachate. PFASs in landfill leachate are eventually transported to the surrounding groundwater, surface water and soil. Some PFASs evaporate from landfills to the ambient air. To avoid the environmental and health risks of PFASs in landfills, new technologies and combined use of existing technologies have been implemented to treat PFASs in landfill leachate. Integrated remediation methods are applied to control the diffusion of PFASs in groundwater surrounding landfills. In future, the mechanisms of PFAAs precursors degradation, the correlation among PFASs in different environmental media around landfills, as well as the environmental behavior and toxic effect of combined pollutants together with PFASs in landfill leachate and surrounding groundwater should be studied.

Critical review on phytoremediation of polyfluoroalkyl substances from environmental matrices: Need for global concern

Poly- and perfluoroalkyl substances (PFAS) are a class of emerging organic contaminants that are impervious to standard physicochemical treatments. The widespread use of PFAS poses serious environmental issues. PFAS pollution of soils and water has become a significant issue due to the harmful effects of these chemicals both on the environment and public health. Owing to their complex chemical structures and interaction with soil and water, PFAS are difficult to remove from the environment. Traditional soil remediation procedures have not been successful in reducing or removing them from the environment. Therefore, this review focuses on new phytoremediation techniques for PFAS contamination of soils and water. The bioaccumulation and dispersion of PFAS inside plant compartments has shown great potential for phytoremediation, which is a promising and unique technology that is realistic, cost-effective, and may be employed as a wide scale in situ remediation strategy.

Removing per- and polyfluoroalkyl substances (PFAS) in water by foam fractionation

Treatment of large volumes of waters contaminated by per- and polyfluoroalkyl substances (PFAS) remains a challenge. This work presented a systematic study on PFAS removal by foam fractionation (FF). Experiments were conducted on both laboratory-spiked and environmental water samples containing PFASs. It is found that higher air flow, greater ionic strength, and addition of thickener boosted PFAS removal in the defoamed bottom solutions and intensified enrichment in the collected foam. FF treatments of a landfill leachate, a groundwater contaminated by aqueous film-forming foams, and a wastewater treatment plant effluent sample were evaluated. The removal reached above 70% for most monitored PFASs, except the ones of short alkyl chains. PFAS concentrations in the final collected foams were up to over 30 × than that in the original samples. Analysis using high-resolution mass spectrometry revealed enrichment of non-target PFASs by FF. The results of this study demonstrate great effectiveness of FF in removing most PFASs from waters, producing low-volume, highly concentrated solutions of PFASs in all tested environmental samples.

Swimming with PFAS in public and private pools

Per- and polyfluoroalkyl substances (PFAS) are a class of anthropogenic chemicals used to provide water and stain resistance in many consumer products. Their widespread use, nearly ubiquitous presence across multiple environments, and growing list of adverse health effects has raised concerns among communities. PFAS have been frequently detected and quantified globally in wastewater, groundwater, surface and drinking water; however, the presence of PFAS in swimming pool water - a unique matrix in which constituents may concentrate through evaporation and which also may present a high risk of direct human exposure - has not been reported. Here, ultra-high performance liquid chromatography - tandem mass spectrometry (UHPLC-MS/MS) was used to monitor 92 PFAS in 54 water samples collected from city, apartment, hotel, and personal swimming pools in six Florida cities. In total, 14 PFAS were detected with six perfluoroalkyl acids - perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA) and perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorobutane sulfonate (PFBS) - detected in every sample. PFHxA accounted for 49% of all PFAS quantified in this study. PFAS profiles were compared between sites as a function of pool type, rate of use, and geographic location. Total ΣPFAS concentrations were similar across pool types, with both the highest (633 ng/L) and lowest (1.9 ng/L) measurements found in public city pools. Between sites, higher PFAS levels were observed in city pools in Miami, Melbourne and Tampa compared to Naples, Orlando and Gainesville. Our findings highlight the potential exposure of PFAS in an underexplored and yet important exposure pathway in communities.

Poly- and Perfluoroalkyl Substances (PFAS) in Landfills: Occurrence, Transformation and Treatment

Landfills have served as the final repository for > 50 % municipal solid wastes in the United States. Because of their widespread uses and persistence in the environment, per- and polyfluoroalkyl substances (PFAS) (>4000 on the global market) are ubiquitously present in everyday consumer, commercial and industrial products, and have been widely detected in both closed (tens ng/L) and active (thousands to ten thousands ng/L) landfills due to disposal of PFAS-containing materials. Along with the decomposition of wastes in-place, PFAS can be transformed and released from the wastes into leachate and landfill gas. Consequently, it is critical to understand the occurrence and transformation of PFAS in landfills and the effectiveness of landfills, as a disposal alternative, for long-term containment of PFAS. This article presents a state-of-the-art review on the occurrence and transformation of PFAS in landfills, and possible effect of PFAS on the integrity of modern liner systems. Based on the data published from 10 countries (250 + landfills), C4-C7 perfluoroalkyl carboxylic acids were found predominant in the untreated landfill leachate and neutral PFAS, primarily fluorotelomer alcohols, in landfill air. The effectiveness and limitations of the conventional leachate treatment technologies and emerging technologies were also evaluated to address PFAS released into the leachate. Among conventional technologies, reverse osmosis (RO) may achieve a high removal efficiency of 90-100 % based on full-scale data, which, however, is vulnerable to the organic fouling and requires additional disposal of the concentrate. Implications of these knowledge on PFAS management at landfills are discussed and major knowledge gaps are identified.

Foam fractionation of per- and polyfluoroalkyl substances (PFASs) in landfill leachate using different cosurfactants

Foam fractionation is one solution to recover per- and polyfluoroalkyl substances (PFASs) from aqueous sources. The separation process is based on the sorption of PFASs to the air-water interface of bubbles. In many practical cases, the PFAS concentration in the polluted liquid is too low to sustain foam formation and requires the support of a cosurfactant not only to act as a collector of PFAS but also to produce and sustain foam for effective separation. However, there is a lack of information regarding the appropriate choice of cosurfactant and its quantitative effect on the interfacial partitioning of PFASs on the air bubbles. This study is directed to (i) evaluate the effectiveness of four cosurfactants with different-charged headgroups (i.e., anionic, cationic, zwitterionic and nonionic) for foam fractionation of PFASs, and (ii) estimate the air-water interfacial partitioning (K_i) of PFASs in the presence of four different types of cosurfactants. The K_i values span over 4 orders of magnitude with good correlation with PFASs molar volume. All of the cosurfactants were effective for the removal of the long chain PFASs (1.2-4 logs). The cationic and zwitterionic surfactants have oppositely charged head groups with respect to the anionic PFASs and therefore facilitate increased separation due to charge interactions. Some short chain PFASs (e.g., Perfluorobutanesulfonic acid (PFBS), Perfluoropentanesulfonic acid (PFPeS)) can be effectively removed using cationic and zwitterionic cosurfactants.

Concentrations of perfluoroalkyl and polyfluoroalkyl substances before and after full-scale landfill leachate treatment

Many consumer and industrial products, industrial wastes and dewatered sludge from municipal wastewater treatment plants containing per- and polyfluoroalkyl substances (PFAS) are disposed of in landfills at the end of their usage, with PFAS in these products leached into landfill leachates. On-site leachate treatment is one possible method to reduce PFAS in leachates. Many landfills are equipped with on-site leachate treatment systems, but few full-scale facilities have been systematically evaluated for PFAS concentration changes. The objective of this study was to evaluate a cross-section of full-scale on-site landfill treatment systems to measure changes in PFAS concentrations. Leachate samples were collected before and after treatment from 15 facilities and were evaluated for 26 PFAS, including 11 perfluoroalkyl carboxylic acids (PFCAs), 7 perfluoroalkyl sulfonic acids (PFSAs), and 8 perfluoroalkyl acid precursors (PFAA-precursors). Transformation of precursors was evaluated by the total oxidizable precursor (TOP) assay. Results showed no obvious reductions in total measured PFAS (∑26PFAS) for on-site treatment systems including ponds, aeration tanks, powdered activated carbon (PAC), and sand filtration. Among evaluated on-site treatment systems, only systems fitted with reverse osmosis (RO) showed significant reductions (98-99 %) of ∑26PFAS in the permeate. Results from the TOP assay showed that untargeted PFAA-precursors converted into targeted short-chain PFCAs increasing ∑26PFAS in oxidized samples by 30 %, on average. Overall, results of this study confirm the efficacy of RO systems and suggest the presence of additional precursors beyond those measured in this study.

Do PFAS changes in landfill leachate treatment systems correlate with changes in physical chemical parameters?

Per- and polyfluoroalkyl substances (PFAS) have been found at relatively elevated concentrations in landfill leachates. Some landfill facilities treat physical-chemical parameters of their leachates using on-site leachate treatment systems before discharge. The objective of this study was to evaluate whether changes in physical-chemical parameters of leachate at on-site treatment systems (including bulk measurements, oxygen demanding components, and metals) were associated with concentration changes in PFAS. Leachates were evaluated at 15 on-site treatment facilities which included pond systems, aeration tanks, powdered activated carbon (PAC), sand filtration, reverse osmosis (RO) and combination treatment processes. Results show that most physical-chemical parameters and PFAS were significantly reduced in RO systems (over 90 %). For pond systems, statistically significant correlations (r_s > 0.6, p < 0.05) were observed between ∑₂₆PFAS changes and the changes in pH, alkalinity, ammonia, and some metals. Significant correlations were also found between ∑₈PFAAs precursors changes and specific conductivity (SPC), pH, alkalinity, ammonia, and metals changes. For aeration tank systems, significant correlations (r_s > 0.6, p < 0.05) were observed between ∑₂₆PFAS changes and changes in total dissolved solids and zinc, and between the changes of ∑₈PFAAs precursors and field pH. These correlations are believed to be associated with rainfall dilution and precipitation of calcium carbonate and other metals as leachate is introduced to the atmosphere.

Assessment of per- and polyfluoroalkyl substances (PFAS) in the Indian River Lagoon and Atlantic coast of Brevard County, FL, reveals distinct spatial clusters

Per- and polyfluoroalkyl substances (PFAS) constitute a class of highly stable and extensively manufactured anthropogenic chemicals that have been linked to a variety of adverse health effects in humans and wildlife. These compounds are ubiquitously distributed in the environment and have been measured in aquatic systems globally. However, there are limited data on longitudinal comprehensive assessments of PFAS profiles within sensitive aquatic ecosystems. Surface water samples were collected from the Indian River Lagoon (IRL) and the Atlantic coast within Brevard County (BC), FL in December of 2019 (n = 57) and again from corresponding locations in February of 2021 (n = 40). Samples were analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) to determine the occurrence, concentration, and distribution of 92 PFAS. No significant difference in total PFAS concentrations were identified between samples collected in 2019 (87 ng/L) and those collected in 2021 (77 ng/L). However, comparisons of PFAS among four natural sub-regions within Brevard County revealed site- and regional-specific differences. The Banana River exhibited the greatest concentration of total PFAS, followed by the southern Indian River, the northern Indian River, and then the Atlantic coast. Six distinct PFAS profiles were identified with the novel application of multivariate statistical cluster analysis, which may be useful for identifying potential sources of PFAS. Elevated total PFAS and unique compound mixtures identified in the Banana River are most likely a result of industrial discharge and extensive historical use of aqueous film-forming foams (AFFF). The environmental persistence of PFAS threatens key ecosystem services and the ecological homeostasis of the Indian River Lagoon - the most biologically diverse estuary in North America. Brevard County offers a unique model site that may be used to investigate potential exposure and health implications for wildlife and adjacent coastal communities, which could be extrapolated to better understand and manage other critical coastal systems.

Survey of per- and polyfluoroalkyl substances (PFAS) in surface water collected in Pensacola, FL

As the persistence of per- and polyfluoroalkyl substances (PFAS) become a global concern, information about the occurrence and characteristics of PFAS in estuarine and marine ecosystems is poorly represented. In this study, the presence of 51 PFAS were monitored in the Pensacola Bay System (PBS), Florida, USA. Due to the presence of many potential PFAS sources in close proximity to the PBS (e.g., military bases, industries, airports and several firefighting stations), the distribution and concentration of PFAS in this estuarine environment provides insights into the fate of these complex compounds as well as the possible impacts on coastal systems. Surface water was collected and analyzed from 45 different sites via Strata-X-AW cartridge extractions and ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis. Recoveries for many PFAS (13/51) were >60% (mean 77 %), with relative standard deviations below 20%, except for N-methylperfluoro-1-octanesulfonamidoacetic acid (N-MeFOSAA) (22%). Of the perfluoroalkyl carboxylic acids (PFCAs), which comprised the majority of PFAS detected: perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) were present in all samples; however, perfluoropentanoic acid (PFPeA) was the individual PFAS with the highest concentration of this group (51.9 ng.L⁻¹, at site 81). The PFAS detected at the highest concentrations were perfluoroalkyl sulfonic acids (PFSA), with perfluorooctane sulfonic acid (PFOS) having the highest detected concentration (269 ng.L⁻¹, at site 81). At all sites, at least eight or more PFAS were quantified. Past and current use of PFAS-containing materials and their fate in areas surrounding military bases, airports, and industries, require more in-depth monitoring efforts to better determine the need for regulation, management, and/or remediation. Here, sites located close to areas suspected of PFAS use had elevated concentrations. For example, one coastal location near an airfield had a ΣPFAS of 677 ng.L⁻¹. Expansion from these ongoing efforts will focus on assessment of PFAS-related effects in local wildlife and evaluating the distribution of PFAS at these “hotspot” sites during large episodic weather events, a critically understudied phenomenon regarding PFAS and vulnerable coastal environments.

•

Elevated PFAS levels were quantified in Pensacola Bay surface water.

•

ΣPFOS was the compound detected with the highest concentration between all PFAS.

•

PFAS diversity increased near sites with industrial effluent and suspected AFFF usage.

Rate, Efficiency, and Mechanisms of Electrochemical Perfluorooctanoic Acid Degradation with Boron-Doped Diamond and Plasma Electrodes

The removal of per- or polyfluorinated alkyl substances (PFAS) has received increasing attention because of their extreme stability, our increasing awareness of their toxicity at even low levels, and scientific challenges for traditional treatment methods such as separation by activated carbon or destruction by advanced oxidation processes. Here, we performed a direct and systematic comparison of two electrified approaches that have recently shown promise for effective degradation of PFAS: plasma and conventional electrochemical degradation. We tailored a reactor configuration where one of the electrodes could be a plasma or a boron-doped diamond (BDD) electrode and operated both electrodes galvanostatically by continuous direct current. We show that while both methods achieved near-complete degradation of PFAS, the plasma was only effective as the cathode, whereas the BDD was only effective as the anode. Compared to the BDD, plasma required more than an order of magnitude higher voltage but lower current to achieve similar degradation efficiency with more rapid degradation kinetics. All these factors considered, it was noted that plasma or BDD degradation resulted in similar energy efficiencies. The BDD electrode exhibited zero-order kinetics, and thus, PFAS degradation using the conventional electrochemical method was kinetically controlled. On the contrary, analysis using a film model indicated that the plasma degradation kinetics of PFAS using plasma were mass-transfer-controlled because of the fast reaction kinetics. With the help of a simple quantitative model that incorporates mass transport, interfacial reaction, and surface accumulation, we propose that the degradation reaction kinetically follows an Eley-Rideal-type mechanism for the plasma electrode, and an intrinsic rate constant of 2.89 × 10⁸ m⁴ mol^-1 s^-1 was obtained accordingly. The investigation shows that to realize the true kinetic potential of plasma degradation for water treatment, mass transfer to the interface must be enhanced.

Emerging technologies for PFOS/PFOA degradation and removal: A review

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are highly recalcitrant anthropogenic chemicals that are ubiquitously present in the environment and are harmful to humans. Typical water and wastewater treatment processes (coagulation, flocculation, sedimentation, and filtration) are proven to be largely ineffective, while adsorption with granular activated carbon (GAC) has been the chief option to capture them from aqueous sources followed by incineration. However, this process is time-consuming, and produces additional solid waste and air pollution. Treatment methods for PFOS and PFOA generally follow two routes: (1) removal from source and reduce the risk; (2) degradation. Emerging technologies focusing on degradation are critically reviewed in this contribution. Various processes such as bioremediation, electrocoagulation, foam fractionation, sonolysis, photocatalysis, mechanochemical, electrochemical degradation, beams of electron and plasma have been developed and studied in the past decade to address PFAS crisis. The underlying mechanisms of these PFAS degradation methods have been categorized. Two main challenges have been identified, namely complexity in large scale operation and the release of toxic byproducts. Based on the literature survey, we have provided a strength-weakness-opportunity-threat (SWOT) analysis and quantitative rating on their efficiency, environmental impact and technology readiness.

Pilot-Scale Continuous Foam Fractionation for the Removal of Per- and Polyfluoroalkyl Substances (PFAS) from Landfill Leachate

Per- and polyfluoroalkyl substances (PFAS) are of concern for their ubiquity in the environment combined with their persistent, bioaccumulative, and toxic properties. Landfill leachate is often contaminated with these chemicals, and therefore, the development of cost-efficient water treatment technologies is urgently needed. The present study investigated the applicability of a pilot-scale foam fractionation setup for the removal of PFAS from natural landfill leachate in a novel continuous operating mode. A benchmark batch test was also performed to compare treatment efficiency. The ΣPFAS removal efficiency plateaued around 60% and was shown to decrease for the investigated process variables air flow rate (Q _air), collected foam fraction (%_foam) and contact time in the column (t _c). For individual long-chain PFAS, removal efficiencies above 90% were obtained, whereas the removal for certain short-chain PFAS was low (<30%). Differences in treatment efficiency between enriching mode versus stripping mode as well as between continuous versus batch mode were negligible. Taken together, these findings suggest that continuous foam fractionation is a highly applicable treatment technology for PFAS contaminated water. Coupling the proposed cost- and energy-efficient foam fractionation pretreatment to an energy-intensive degradative technology for the concentrated foam establishes a promising strategy for on-site PFAS remediation.

Municipal solid waste incineration (MSWI) ash co-disposal: Influence on per- and polyfluoroalkyl substances (PFAS) concentration in landfill leachate

Municipal solid waste incineration (MSWI) ash is often managed through co-disposal with unburned wastes in landfills, a practice previously reported to result in enhanced leaching of pollutants (e.g., heavy metals) in landfill leachate. The objective of this study was to evaluate the effect of co-disposed unburned wastes on per- and polyfluoroalkyl substances (PFAS) in MSWI ash landfill leachate. Leachate was collected from four landfills containing MSWI ash, either as a sole waste stream or co-disposed of with sewage sludge and MSW screenings. Samples of ash and unburned materials were collected and assessed separately for leachable PFAS in the laboratory. All samples were analyzed for 26 PFAS. Results showed that greater ash content was associated with lower leachate PFAS concentrations. The pure ash monofill exhibited the lowest PFAS in landfill leachate (290 ng L-1) while the landfill contained a large amount of unburned waste had the highest PFAS (11,000 ng L-1). For laboratory leaching tests, average ∑26PFAS concentration in lab ash leachate (310 ng L-1) was 10 and 24 times lower than observed in lab sewage sludge leachate (3,200 ng L-1) and lab MSW screenings leachate (7,500 ng L-1), respectively. Leachate from the ash-only landfill had ∑26PFAS concentration similar to what was measured in the ash itself. On the contrary, ∑26PFAS concentration in co-disposal landfill leachates were similar to those in PFAS-rich unburned waste itself, regardless of the percentages of landfilled unburned wastes. We hypothesize that leachate generated in co-disposal scenarios preferentially flows through PFAS-rich unburned materials and that biotransformation of precursors enhanced by unburned waste degradation further contributes to higher concentrations of terminal PFAS in ash co-disposal sites. Landfill operators should expect PFAS in leachates to be higher when PFAS-rich unburned wastes are disposed of alongside MSWI ash, even if the unburned fraction is small.

Per- and Polyfluorinated Alkyl Substances (PFAS) cycling within Michigan: Contaminated sites, landfills and wastewater treatment plants

Concentrations of Per- and Polyfluorinated Alkyl Substances (PFAS) from public and private sources in Michigan compiled for wastewater treatment plants (WWTPs) (influent, effluent, biosolids), contaminated sites, and landfill leachates reveal complex cycling within the natural and engineered environment. Analysis of 171 contaminated sites in Michigan by source release indicate four dominant PFAS sources - landfills, aqueous film-forming foams (AFFF), metal platers, and automotive/metal stamping - account for 75% of the contamination. Diverse chemical signatures were observed for leachates collected from 19 landfills (mostly type II municipal) with the dominant PFAS ranging from perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) to shorter-chained compounds, perfluorohexanoic acid (PFHxA), perfluorobutanoic acid (PFBA), and perfluorobutanesulfonic acid (PFBS). Analysis of PFAS carbon chain length as a function of landfill age shows the transition of C8s in leachate from older landfills to C4s and C6s in younger landfills, consistent with the phasing out and replacement of C8s. PFAS mass flux in leachate for landfills studied range between 5 - 2,000 g/yr and are highest for active landfills, which generate greater leachate volumes and contain fresh PFAS wastes. Detailed study of 10 WWTPs with industrial pretreatment programs indicate numerous chemical transformations across the plants that yield effluent PFAS concentrations as much as 19 times greater than influent, attributed to transformations of unmeasured precursors in the influent to measured, stable PFAS in the effluent. PFOA, PFHxA, perfluoropentanoic acid (PFPeA), PFBA, and PFBS show the greatest increases across the plant ranging from 20% to nearly 2,000%. PFOS concentrations decreased across 6 WWTPs, consistent with a strong tendency to adsorb onto biosolids. Estimated mass of discharge of (mostly unregulated) PFAS from WWTPs to receiving waters range from 40 g/yr to 128 kg/yr.

Evaluation of Different Extraction Methods for the Analysis of Per- and Polyfluoroalkyl Substances in Dried Blood Spots from the Florida Manatee (Trichechus manatus)

Per- and polyfluoroalkyl substances (PFAS) are environmental contaminants linked to adverse health effects in humans and wildlife. Marine mammals, particularly manatees, have shown potential as sentinels for evaluating the presence and effects of anthropogenic chemicals. However, traditional blood collection techniques with marine mammals can be challenging, highlighting the need for improved strategies. In the present study, four different methods for the extraction of PFAS from dried blood spots were evaluated. Environ Toxicol Chem 2021;40:2726-2732. © 2021 SETAC.

Ticks as novel sentinels to monitor environmental levels of per- and polyfluoroalkyl substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent, ubiquitous pollutants. It is important to continuously monitor the presence of PFAS contamination, utilizing both legacy and new sentinels. In this study, environmental PFAS levels were evaluated using ticks as a sentinel model due to their world-wide distribution, hematophagous nature, and ease of collection and sampling. Hematophagy in discrete blood meals, from a suite of vertebrates, allows ticks to sample dozens of species of consumers and bioaccumulation across communities. Four different species of ticks, across two states (NY, n = 28 in mid-April of 2020 and FL, n = 32 between 2015 and 2020) with two sampling sites in each state were analyzed for the presence of 53 PFAS. The total PFAS concentration in ticks was the lowest at Newburgh (NY), a site that has been undergoing remediation efforts, while the highest total PFAS concentrations were measured in ticks at the Sweetwater site, a wastewater treatment wetland. Detection of PFAS and the potential for variation between tick species and between locations are necessary to establish the utility of ticks as sentinels, in addition to assessing additional environmental factors, such as other wildlife, water, or soil.

Perfluoroalkyl acids on suspended particles: Significant transport pathways in surface runoff, surface waters, and subsurface soils

Eroded particles from the source zone could transport a high concentration of perfluoroalkyl acids (PFAAs) to sediments and water bodies. Yet, the contribution of suspended particles has not been systematically reviewed. Analyzing reported studies, we quantitatively demonstrate that suspended particles in surface water can contain significantly higher concentrations of PFAAs than the sediment below, indicating the source of suspended particles are not the sediment but particles eroded and carried from the source zone upstream. The affinity of PFAAs to particles depends on the particle composition, including organic carbon fraction and iron or aluminum oxide content. In soils, most PFAAs are retained within the top 5 m below the ground surface. The distribution of PFAAs in the subsurface varies based on site properties and local weather conditions. The depth corresponding to the maximum concentration of PFAA in soil decreases with an increase in soil organic carbon or rainfall amount received in the catchment areas. We attribute a greater accumulation of PFAAs near the upper layer of the subsurface to an increase in the accumulation of particles eroded from source zones upstream receiving heavy rainfall. Precursor transformation in the aerobic zone is significantly higher than in the anaerobic zone, thereby making the aerobic subsurface zone serve as a long-term source of groundwater pollution. Collectively, these results suggest that suspended particles, often an overlooked vector for PFAAs, can be a dominant pathway for the transport of PFAAs in environments.

Managing and treating per- and polyfluoroalkyl substances (PFAS) in membrane concentrates

Per- and polyfluoroalkyl substances (PFAS), which are present in many waters, have detrimental impacts on human health and the environment. Reverse osmosis (RO) and nanofiltration (NF) have shown excellent PFAS separation performance in water treatment; however, these membrane systems do not destroy PFAS but produce concentrated residual streams that need to be managed. Complete destruction of PFAS in RO and NF concentrate streams is ideal, but long-term sequestration strategies are also employed. Because no single technology is adequate for all situations, a range of processes are reviewed here that hold promise as components of treatment schemes for PFAS-laden membrane system concentrates. Attention is also given to relevant concentration processes because it is beneficial to reduce concentrate volume prior to PFAS destruction or sequestration. Given the costs and challenges of managing PFAS in membrane concentrates, it is critical to evaluate both established and emerging technologies in selecting processes for immediate use and continued research.

The last straw: Characterization of per- and polyfluoroalkyl substances in commercially-available plant-based drinking straws

Paper and other plant-based drinking straws are replacing plastic straws in commercial settings in response to trending plastic straw bans and the larger global movement for reducing plastic pollution. The water-resistant properties of many plant-based straws, however, may be attributed to the use of per- and polyfluoroalkyl substances (PFAS) during manufacturing. In this study, 43 brands of straws (5 plastic, 29 paper, 9 other plant-based) were analyzed for the presence of 53 semi-volatile PFAS using ultra high-performance liquid chromatography tandem mass spectrometry. While the plastic straws had no measurable PFAS, 21 PFAS were detected in the paper and other plant-based straws, with total mean PFAS concentrations (triplicate analysis) ranging from 0.043 ± 0.004 ng/straw to 29.1 ± 1.66 ng/straw (median = 0.554 ng/straw). Perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA) and perfluorohexanoic acid (PFHxA) were the most frequently detected species. In a follow-up experiment, the brand with the highest PFAS levels and most diversity was tested for leaching in water at initial temperatures of 4 °C, 20 °C, and 90 °C. Approximately 2/3 of the total extractable PFAS leached compared to the initial methanol extraction. Semi-volatile PFAS concentrations measured in this study may be the result of manufacturing impurities or contamination, as PFAS approved for food-contact use are, typically, polymeric species. The presence of PFAS in plant-based drinking straws demonstrates that they are not fully biodegradable, contributing to the direct human ingestion of PFAS and to the cycle of PFAS between waste streams and the environment.

Thermal Decomposition of Anionic, Zwitterionic, and Cationic Polyfluoroalkyl Substances in Aqueous Film-Forming Foams

In this study, we investigated thermal decomposition mechanisms of cationic, zwitterionic, and anionic polyfluoroalkyl substances, including those present in aqueous film-forming foam (AFFF) samples. We present novel evidence that polyfluoroalkyl substances gave quantitative yields of perfluoroalkyl substances of different chain lengths during thermal treatment. The results support a radical-mediated transformation mechanism involving random-chain scission and end-chain scission, leading to the formation of perfluoroalkyl carboxylic acids such as perfluorooctanoic acid (PFOA) from certain polyfluoroalkyl amides and sulfonamides. Our results also support a direct thermal decomposition mechanism (chain stripping) on the nonfluorinated moiety of polyfluoroalkyl sulfonamides, resulting in the formation of perfluorooctanesulfonic acid (PFOS) and other structurally related polyfluoroalkyl compounds. Thermal decomposition of 8:2 fluorotelomer sulfonate occurred through end-chain scission and recombination reactions, successively yielding PFOS. All of the studied polyfluoroalkyl substances began to degrade at 200-300 °C, exhibiting near-complete decomposition at ≥400 °C. Using a high-resolution parent ion search method, we demonstrated for the first time that low-temperature thermal treatments of AFFF samples led to the generation of anionic fluoroalkyl substances, including perfluoroheptanesulfonamide, 8:2 fluorotelomer sulfonic acid, N-methyl perfluorooctane sulfonamide, and a previously unreported compound N-2-propenyl-perfluorohexylsulfonamide. This study provides key insights into the fate of polyfluoroalkyl substances in thermal processes.

From Waste Collection Vehicles to Landfills: Indication of Per- and Polyfluoroalkyl Substance (PFAS) Transformation

Municipal solid waste contain diverse and significant amounts of per- and polyfluoroalkyl substances (PFAS), and these compounds may transform throughout the "landfilling" process from transport through landfill degradation. Fresh vehicle leachates, from commercial and residential waste collection vehicles at a transfer station, were measured for 51 PFAS. Results were compared to PFAS levels obtained from aged landfill leachate at the disposal facility. The landfill leachate was dominated by perfluoroalkyl acids (PFAAs, including perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs); 86% of the total PFAS, by median mass concentration), while the majority of PFAS present in commercial and residential waste vehicle leachate were PFAA-precursors (70% and 56% of the total PFAS, by median mass concentration, respectively), suggesting precursor transformation to PFAAs during the course of landfill disposal. In addition, several PFAS, which are not routinely monitored-perfluoropropane sulfonic acid (PFPrS), 8-chloro-perfluoro-1-octane sulfonic acid (8Cl-PFOS), chlorinated polyfluoroether sulfonic acids (6:2, 8:2 Cl-PFESAs), sodium dodecafluoro-3H-4,8-dioxanonanoate (NaDONA), and perfluoro-4-ethylcyclohexanesulfonate (PFECHS)-were detected. Potential degradation pathways were proposed based on published studies: transformation of polyfluoroalkyl phosphate diester (diPAPs) and fluorotelomer sulfonic acids (FTS) to form PFCAs via formation of intermediate products such as fluorotelomer carboxylic acids (FTCAs).

An Overview of Per- and Polyfluoroalkyl Substances (PFAS) in the Environment: Source, Fate, Risk and Regulations

The current article reviews the state of art of the perfluoroalkyl and polyfluoroalkyl substances (PFASs) compounds and provides an overview of PFASs occurrence in the environment, wildlife, and humans. This study reviews the issues concerning PFASs exposure and potential risks generated with a focus on PFAS occurrence and transformation in various media, discusses their physicochemical characterization and treatment technologies, before discussing the potential human exposure routes. The various toxicological impacts to human health are also discussed. The article pays particular attention to the complexity and challenging issue of regulating PFAS compounds due to the arising uncertainty and lack of epidemiological evidence encountered. The variation in PFAS regulatory values across the globe can be easily addressed due to the influence of multiple scientific, technical, and social factors. The varied toxicology and the insufficient definition of PFAS exposure rate are among the main factors contributing to this discrepancy. The lack of proven standard approaches for examining PFAS in surface water, groundwater, wastewater, or solids adds more technical complexity. Although it is agreed that PFASs pose potential health risks in various media, the link between the extent of PFAS exposure and the significance of PFAS risk remain among the evolving research areas. There is a growing need to address the correlation between the frequency and the likelihood of human exposure to PFAS and the possible health risks encountered. Although USEPA (United States Environmental Protection Agency) recommends the 70 ng/L lifetime health advisory in drinking water for both perfluorooctane sulfonate (PFO) perfluorooctanoic acid (PFOA), which is similar to the Australian regulations, the German Ministry of Health proposed a health-based guidance of maximum of 300 ng/L for the combination of PFOA and PFOS. Moreover, there are significant discrepancies among the US states where the water guideline levels for the different states ranged from 13 to 1000 ng L−1 for PFOA and/or PFOS. The current review highlighted the significance of the future research required to fill in the knowledge gap in PFAS toxicology and to better understand this through real field data and long-term monitoring programs.