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[Display omitted] • Three PFAS leached from biochar derived from construction/demolition (CDD) wood. • 5:3 FTCA was reduced by CDD wood biochar in landfill leachate batch leaching. • Low biochar surface area and high matrix organic matter hinder PFAS sorption. • CDD wood biochar not recommended for in-situ landfill leachate PFAS reduction. 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. [ABSTRACT FROM AUTHOR]

As regulatory frameworks for per- and polyfluoroalkyl substances (PFAS) evolve, the solid waste community seeks to manage PFAS risks effectively. Despite extensive research on PFAS in municipal solid waste (MSW) and wastewater sludge, there is limited information on a major global waste stream which seldom gleans regulatory oversight — construction and demolition debris (CDD). This study sampled a CDD processing facility to provide material-specific information on the PFAS profile within CDD. The bulk CDD accepted by this facility was separated into major categories, representatively sampled, then characterized for total available PFAS (∑ 92 PFAS). As reprocessed CDD is ultimately recycled or landfilled, often unencapsulated or in unlined landfills, the PFAS leaching potential was also examined using two leaching procedures. Among the categories assessed for total PFAS, carpeting, carpet padding, and gypsum drywall showed elevated concentrations compared to other components, with most of the PFAS mass contributed by precursor species. However, materials with the highest total PFAS, such as carpeting, did not necessarily exhibit the highest leaching, and leachate was predominantly composed of terminal species rather than precursors. Extrapolating these findings with national CDD generation and management data inventories suggests that despite MSW having higher total available PFAS concentrations, the leachability of PFAS from landfilled CDD is comparable, raising legitimate concerns with CDD disposal practices, particularly in unlined CDD landfills. [Display omitted] • Various PFAS levels detected in CDD components. • Majority of total available PFAS was from precursor species. • Leachable PFAS consisted mainly of PFCAs. • Data were extrapolated to estimate US CDD waste PFAS mass. • CDD may pose similar or greater leaching risk compared to MSW. [ABSTRACT FROM AUTHOR]

• Co-disposing MSWI ash with unburned waste on PFAS in landfill leachate. • Higher MSWI ash content associated with lower PFAS landfill leachate concentration. • Ash co-disposal resulted in higher PFAS concentration in landfill leachate. • Disposing MSWI ash as a single waste stream may be a better management strategy. 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 ∑ 26 PFAS 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 ∑ 26 PFAS concentration similar to what was measured in the ash itself. On the contrary, ∑ 26 PFAS 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. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Climate has been previously indicated as a factor in MSW landfill leachate PFAS. • No PFAS data is published for leachate from landfills in tropical climates. • 51 PFAS were quantified in 20 leachate samples from MSW landfills in Puerto Rico. • Mean total PFAS concentrations (38,000 ng L−1) were higher than other US studies. • On-site leachate treatment may cause PFAS transformation, changes in PFAS profile. [ABSTRACT FROM AUTHOR]

[Display omitted] • Estimated amount of ∑ 26 PFAS released from landfills (M ̇ SW) was 36.8 g/ha-yr. • 97% and 3% of M ̇ SW was found in leachate and stormwater, respectively. • Less than 1% of M ̇ SW was found in gas condensate and groundwater. • ∑ 8 PFAA-precursors/∑ 26 PFAS was consistent in the leachate released. • PFAS from landfills will be released for an estimated period of over 40 years. Per- and polyfluoroalkyl substances (PFAS) have been found at high levels within landfill environments. To assess PFAS distributions, this study aimed to evaluate PFAS mass flux leached from disposed solid waste and within landfill reservoirs by mass balance analyses for two full-scale operational Florida landfills. PFAS mass flux in different aqueous components within landfills were estimated based on PFAS concentrations and water flow rates. For PFAS concentration, 26 PFAS, including 18 perfluoroalkyl acids (PFAAs) and 8 PFAA-precursors, were measured in samples collected from the landfills or estimated based on previous studies. Flow rates of aqueous components (rainfall, evapotranspiration, runoff, stormwater, groundwater, leakage, gas condensate, and leachate) were evaluated through the Hydrologic Evaluation of Landfill Performance model, water balance, and Darcy's Law. Results showed that the average PFAS mass flux leached from the solid waste standardized by area was estimated as 36.8 g/ha-yr, which was approximately 1 % to 3 % of the total amount of PFAS within the solid waste. The majority of PFAS leached from the solid waste (95 % to 97 %) is captured by the leachate collection system, with other aqueous components representing much smaller fractions (stormwater system at 3 % to 5 %, and gas condensate and groundwater at < 1 %). Also, based on the results, we estimate that PFAS releases will likely occur at least over 40 years. Overall, these results can help prioritize components for waste management and PFAS treatment during the anticipated landfill release periods. [ABSTRACT FROM AUTHOR]

[Display omitted] • PFAS concentrations in aqueous samples were measured at two landfills. • PFAS in municipal solid waste leachate was more variable than MSW ash leachate. • PFAS concentrations were stable within landfills (coefficient of variation < 50 %) • Leachate in uncovered trenches had the highest fluctuations. • PFAS fluctuations associated with alkalinity, total organic carbon, and ammonia. Studies of per- and polyfluoroalkyl substances (PFAS) fluctuations at landfills have focused on municipal solid waste (MSW) leachate. Few studies exist that evaluate fluctuations (defined by the coefficient of variation, CV) in MSW incinerator ash (MSWA) landfill leachate and that evaluate PFAS fluctuations in stormwater, groundwater, and treated liquids on-site. In this study, aqueous landfill samples (leachate, treated leachate, stormwater, gas condensate, ambient groundwater, and effluent from a groundwater remediation system) were collected from a MSW and an MSWA landfill geographically located within close proximity (less than 40 km). The objective of this study was to compare the leachate compositions between these two landfill types and to evaluate temporal variations. Results indicated that the CV of total detected PFAS concentrations in leachate was higher for the MSW landfill (CV = 43 %) compared to the MSWA landfill (CV = 16 %). The total detected PFAS concentration in MSW leachate samples (mean: 9641 ng/L) was higher than in MSWA leachate samples (mean: 2621 ng/L) (p < 0.05). Within a landfill, PFAS concentrations were correlated (r s > 0.6, p < 0.05) with alkalinity, total organic carbon (TOC), and ammonia. Results from the on-site leachate treatment system at the MSW landfill indicated reductions in COD, TOC, and ammonia; however, the ∑ 26 PFAS concentration increased 3 % after the treatment. Overall, results demonstrated that differences between landfill types and fluctuations in PFAS within landfills should be considered when designing landfill leachate collection and treatment systems to remove PFAS. The comparative analysis in this study can provide insights into optimizing leachate management for MSW and MSWA landfills. [ABSTRACT FROM AUTHOR]

• PFAS concentration was evaluated for 15 on-site leachate treatment facilities. • PFAA-precursors convert into PFAAs in the treated effluent. • PFAS concentration and species distribution fluctuate at the surface amid aeration. • RO systems reduce over 95 % of PFAS concentration in the permeate. • The interpretation of TOP assay for leachate is subject to limitations. 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 (∑ 26 PFAS) 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 ∑ 26 PFAS in the permeate. Results from the TOP assay showed that untargeted PFAA-precursors converted into targeted short-chain PFCAs increasing ∑ 26 PFAS 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fifteen landfill facilities, with on-site treatment systems in Florida, were evaluated. • Changes between influent and effluent (Δ) were analyzed. • Δ conductivity, pH, alkalinity, and ammonia were associated with Δ PFAS. • Δ PFAS were associated with Δ Ba, Co, Ca, Fe, Mg and Zn. • Associations may be due to effects from dilution and chemical precipitation. 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 ∑ 26 PFAS changes and the changes in pH, alkalinity, ammonia, and some metals. Significant correlations were also found between ∑ 8 PFAAs 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 ∑ 26 PFAS changes and changes in total dissolved solids and zinc, and between the changes of ∑ 8 PFAAs 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. [ABSTRACT FROM AUTHOR]

and polyfluoroalkyl substances (PFAS) have been measured in aqueous components within landfills. To date, the majority of these studies have been conducted in Florida. This current study aimed to evaluate PFAS concentrations in aqueous components (leachate, gas condensate, stormwater, and groundwater) from four landfills located outside of Florida, in Pennsylvania, Colorado, and Wisconsin (2 landfills). The Pennsylvania landfill also provided the opportunity to assess a leachate treatment system. Sample analyses were consistent across studies including the measurements of 26 PFAS and physical-chemical parameters. For the four target landfills, average PFAS concentrations were 6,900, 22,000, 280, and 260 ng L−1 in the leachate, gas condensate, stormwater, and groundwater, respectively. These results were not significantly different than those observed for landfills in Florida except for the significantly higher PFAS concentrations in gas condensate compared to leachate. For on-site treatment at the Pennsylvania landfill, results suggest that the membrane biological bioreactor (MBBR) system performed similarly as aeration-based leachate treatment systems at Florida landfills resulting in no significant decreases in ∑ 26 PFAS. Overall, results suggest a general consistency across US regions in PFAS concentrations within different landfill liquid types, with the few differences observed likely influenced by landfill design and local climate. Results confirm that leachate exposed to open air (e.g., in trenches or in treatment systems) have lower proportions of perfluoroalkyl acid precursors relative to leachate collected in enclosed pipe systems. Results also confirm that landfills without bottom liner systems may have relatively higher PFAS levels in adjacent groundwater and that landfills in wetter climates tend to have higher PFAS concentrations in leachate. [Display omitted] • Like other studies, higher PFAS in leachate than stormwater and groundwater. • PFAS higher in gas condensate than leachate, unlike other studies. • Physical chemical parameters like other studies, but not correlated with PFAS. • MBBR system performed similarly as aeration-based leachate treatment. • Consistency was found for PFAS in landfills from different US states. [ABSTRACT FROM AUTHOR]

Variable chemistries of liquids from landfills can potentially impact levels of per- and polyfluoroalkyl substances (PFAS). The objective of the current study was to evaluate relationships between physical-chemical properties (bulk measurements, oxygen demand components, and metals) and PFAS concentrations in different types of aqueous landfill samples. Aqueous landfill samples were collected from 39 landfill facilities in Florida, United States. These samples included leachates from landfills that receive different waste types, such as municipal solid waste incineration ash (MSWA), construction and demolition debris (C&D), and municipal solid waste (MSW). Additional aqueous landfill samples were sourced from treated landfill leachate, gas condensate, stormwater, and groundwater from within and near the landfill boundaries. Results showed significant correlations (p < 0.05) between ∑ 26 PFAS and alkalinity (r s = 0.83), total organic carbon (TOC) (r s = 0.84), and ammonia (r s = 0.79) for all leachate types. Other physical-chemical parameters that were significantly correlated (r s > 0.60, p < 0.05) with PFAS included specific conductivity, chemical oxygen demand (COD), and to a lesser extent, total dissolved solids (TDS) and total solids (TS). For gas condensates, PFAS was significantly correlated with TOC. Stormwater and groundwater, within and near the landfill boundaries, had considerably lower levels of PFAS and had a minimal correlation between PFAS and physical-chemical parameters. Although PFAS concentrations and physical-chemical parameters and their correlations varied between different types of aqueous landfill samples, results suggest that physical-chemical properties can be useful indicators of relative PFAS concentrations within a leachate type. More research is needed to validate the mechanisms that relate physical-chemical parameters to PFAS concentrations in landfill leachates. [Display omitted] • Aqueous samples from 39 landfill facilities in Florida were evaluated. • PFAS and 35 physical-chemical parameters were analyzed. • Alkalinity, TOC, and ammonia were correlated with PFAS. • Some associations were dependent on leachate type. • Associations may be due to dilution and chemical precipitation when released. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Two leachates were collected from landfill gas systems: condensate and well pumpout. • Gas condensate is not colored, contains ammonia, alkalinity, and some metalloids. • Gas well pump-out is dark in color, resembles leachate, high chloride concentrations. • Condensate has lower total PFAS abundance, but greater diversity of species. • PFAS which are more abundant in condensate include semi-volatile FTOHs and FASEs. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS), found in many consumer products, are commonly disposed of in landfills at the end of their service lives. To identify landfill liquids that should be prioritized for treatment, this study aimed to evaluate PFAS levels in different aqueous samples from landfills and identify relationships between PFAS and landfill characteristics. Twenty-six PFAS including 11 perfluoroalkyl carboxylic acids (PFCAs), 7 perfluoroalkyl sulfonates (PFSAs), and 8 perfluoroalkyl acid precursors (PFAA-precursors) were measured in municipal solid waste (MSW) leachate, construction and demolition debris (CDD) leachate, municipal solid waste incineration (MSWI) ash leachate, gas condensate, stormwater, and groundwater from landfills. Based on the median, results show that PFAS levels in MSW leachate were the highest (10,000 ng L−1), CDD leachate were intermediate (6200 ng L−1), and MSWI ash leachate were the lowest (1300 ng L−1) among the leachates evaluated. PFAS levels in gas condensate (7000 ng L−1) were similar to MSW leachate. PFAS in stormwater and groundwater were low (medians were less than 500 ng L−1). Dominant subgroups included PFCAs and PFAA-precursors in all leachates. PFSAs were also found in CDD leachate, PFAA-precursors in gas condensate, and PFCAs in stormwater and groundwater. Landfill characteristics significantly correlated with ∑ 26 PFAS included waste proportions (percentage of MSWI ash in landfill, |r s | = 0.22), operational status (active or not, |r s | = 0.27) and rainfall (30-d cumulative rainfall, |r s | = 0.39). The results from this study can be used to prioritize which landfills and which reservoir of liquids (and corresponding subgroup of PFAS) to target for PFAS management. [Display omitted] • ∑ 26 PFAS in gas condensate ≈ landfill leachates > stormwater > groundwater. • Among landfill leachates, ∑ 26 PFAS concentrations in MSW > CDD > MSWI ash. • PFCAs dominant in all aqueous samples and precursors also dominant in leachates. • ∑ 26 PFAS significantly correlated with some landfill characteristics. • Results can be used to inform management of liquids at landfills. [ABSTRACT FROM AUTHOR]