Underestimation of Per- and Polyfluoroalkyl Substances in Biosolids: Precursor Transformation During Conventional Treatment.

Wastewater treatment plants generate a solid waste known as biosolids. The most common management option for biosolids is to beneficially reuse them as an agricultural amendment, but because of the risk of pathogen exposure, many regulatory bodies require pathogen reduction before biosolids reuse. Per- and polyfluoroalkyl substances (PFAS) are well documented in biosolids, but limited information is available on how biosolids treatment processes impact PFAS. Furthermore, quantification of PFAS has focused on perfluoroalkyl acids (PFAAs) which are a small fraction of thousands of PFAS known to exist. The objective of this study was to quantify 92 PFAS in biosolids collected from eight biosolids treatment facilities before and after four pathogen treatment applications: composting, heat treatment, lime treatment, and anaerobic digestion. Overall, total PFAS concentrations before and after treatment were dominated by PFAA precursor species, in particular, diPAPs which accounted for a majority of the mass of the Σ92PFAS. This differs from historic data that found PFAAs, primarily PFOS, to dominate total PFAS concentrations. Treatment options such as heat treatment and composting changed the ratio of PFAA precursors to PFAAs indicating a transformation of PFAS during treatment. This study finds that PFAA precursors are likely underrepresented by other studies and make up a larger percentage of the total PFAS concentration in biosolids than previously estimated.

Assessment of Municipal Solid-Waste Landfill Liner Performance.

The leachate collection system (LCS) and leak detection system (LDS) flow rate data from 240 cells (or a combination of cells) at 54 municipal solid-waste landfills (located in seven US states) with double-liner systems were analyzed to assess the performance of the primary liner system. The average LCS leachate collection rates for the study sites ranged from 380 L ha-1 day-1 (40.7 gal. acre-1 day-1) to 22,400 L ha-1 day-1 (2,390 gal. acre-1 day-1) on a sitewide basis, and the average LDS leachate collection rates ranged from 1.8 L ha-1 day-1 (0.2 gal. acre-1 day-1) to 577 L ha-1 day-1 (61.7 gal. acre-1 day-1) on a sitewide basis. Assuming all leachate generated is collected either by the LCS or LDS, the data suggest that the primary liner systems' aggregated efficiency is over 98%. The collection efficiency at sites that used a composite liner (geomembrane underlain by a geosynthetic clay liner or a compacted clay liner) system was not statistically different from the sites that used only a geomembrane as the primary liner (geomembrane underlain by a permeable layer) (median of 99% for both types). Leakage rates were compared with those estimated from the equations used by the hydrologic evaluation of landfill performance (HELP) model. The comparison suggests that the equations used by the HELP model to estimate leakage through the liner overestimate the leakage rate through geomembrane primary liners but underestimate the leakage rate through composite primary liners based on the HELP-model-default defect size and suggested defect frequency. It is also possible that groundwater intrusion could contribute to a portion of the leachate collected from the LDS because leachate quality data collected from a few sites indicated the LCS leachate had a higher concentration of most constituents than the leachate collected from LDS.

Per- and Polyfluoroalkyl Substances (PFAS) in Street Sweepings.

One hundred and seventeen street sweeping samples were collected and analyzed for per- and polyfluoroalkyl substances (PFAS). Fifty-six samples were collected in one city (Gainesville, Florida) allowing for an in-depth city-wide characterization. Street sweepings from five other urban areas, (Orlando, n = 15; Key West, n = 15; Pensacola, n = 12; Tampa, n = 13; and Daytona Beach, n = 6) were analyzed to provide a city-to-city comparison of PFAS. Within our analytical workflow, 37 PFAS were quantified across all samples, while the maximum number of PFAS quantified at one site was 26. Of those PFAS quantified in Gainesville, 60% were perfluoroalkyl acids (PFAAs) and 33% were precursors to PFAA. Among the PFAAs, short-chain perfluoroalkyl carboxylic acids (PFCAs) were the dominant class representing 26% of the total PFAS by concentration. In the comparison across different urban cities, the dominant compound by concentration and frequency of detection varied; however, perfluorooctanoic acid (PFOA) and linear perfluorooctanesulfonic acid (PFOSlin) were the two PFAS that were detected the most frequently. This study documents the first-time detection of hexadecafluorosebacic acid and perfluoro-3,6,9-trioxaundecane-1,11-dioic acid within environmental samples.

Comparison of trace element mobility from MSWI ash before and after plasma vitrification.

A common perception of plasma arc treatment systems for municipal solid waste incineration ash is that the resulting vitrified slag is inert from an environmental perspective. Research was conducted to examine this hypothesis and to assess whether reduced pollutant release results from pollutant depletion during the process of the ash with plasma, or encapsulation in the glassy vitrified matrix. The concentrations of four discrete municipal solid waste incineration ash samples before and after plasma arc vitrification in a bench-scale unit were compared. Slag and untreated ash samples were leached using several standardized approaches and mobility among the four metals of interest (e.g. As, Cd, Pb and Sb) varied across samples, but was generally high (as high as 100% for Cd). Comparison across methods did not indicate substantial encapsulation in the vitrified slag, which suggests that reduced pollutant release from plasma arc vitrified slag is due to pollutant depletion by volatilization, not encapsulation. This has significant implications for the management of air pollution control residues from waste-to-energy facilities using plasma arc vitrification.

Toward Comprehensive Per- and Polyfluoroalkyl Substances Annotation Using FluoroMatch Software and Intelligent High-Resolution Tandem Mass Spectrometry Acquisition.

Thousands of per- and polyfluoroalkyl substances (PFAS) exist in the environment and pose a potential health hazard. Suspect and nontarget screening with liquid chromatography (LC)-high-resolution tandem mass spectrometry (HRMS/MS) can be used for comprehensive characterization of PFAS. To date, no automated open source PFAS data analysis software exists to mine these extensive data sets. We introduce FluoroMatch, which automates file conversion, chromatographic peak picking, blank feature filtering, PFAS annotation based on precursor and fragment masses, and annotation ranking. The software library currently contains ∼7 000 PFAS fragmentation patterns based on rules derived from standards and literature, and the software automates a process for users to add additional compounds. The use of intelligent data-acquisition methods (iterative exclusion) nearly doubled the number of annotations. The software application is demonstrated by characterizing PFAS in landfill leachate as well as in leachate foam generated to concentrate the compounds for remediation purposes. FluoroMatch had wide coverage, returning 27 PFAS annotations for landfill leachate samples, explaining 71% of the all-ion fragmentation (CF2)n related fragments. By improving the throughput and coverage of PFAS annotation, FluoroMatch will accelerate the discovery of PFAS posing significant human risk.

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

Large volumes of per- and polyfluoroalkyl substances (PFAS)-contaminated wastewaters, such as municipal solid waste landfill leachates, pose a challenge for PFAS treatment technologies in practice today. In this study, the surfactant properties of PFAS were exploited to concentrate the compounds in foam produced via the bubble aeration of landfill leachate. The effectiveness of the foaming technique for concentrating PFAS varied by compound, with a mean removal percentage (the percent difference between PFAS in leachate before and after foam removal) of 69% and a median removal percentage of 92% among the 10 replicate foaming experiments. This technique appears to be similarly effective at sequestering sulfonates and carboxylate PFAS compounds and is less effective at concentrating the smallest and largest PFAS molecules. The results of this study suggest that for the pretreatment or preconcentration of landfill leachates, foaming to sequester PFAS may provide a practical approach that could be strategically coupled to high-energy PFAS-destructive treatment technologies. The process described herein is simple and could feasibly be applied at a relatively low cost at most landfills, where leachate aeration is already commonplace.

Characterizing municipal solid waste component densities for use in landfill air space estimates.

Understanding the densities of individual waste materials in landfills as a function of landfill overburden pressure can provide a means to estimate the space occupied by these materials when they are landfilled. A compression device was used to simulate the overburden pressures in a landfill to determine the densities associated with 14 material categories. The materials with the greatest density were food waste, yard waste, and glass, ranging from 1302 to 1865 kg m-3. The lowest density was associated with aluminum and steel/tin cans at 206 and 389 kg m-3, respectively. Some materials did not exhibit a large variation in density when the load increased, indicating that their density was mostly independent of the overburden pressure. The data gathered from this research can be used as lifecycle assessment impact categories, where the functional unit of interest is 1 tonne of a material and the impact is measured as m3 of landfill space occupied.

Polycyclic aromatic hydrocarbons in processed yard trash.

This work examines polycyclic aromatic hydrocarbon (PAH) concentrations in yard trash at various stages of the yard trash management cycle of collection, stockpiling, grinding and screening into mulch, and composting. Total extractable PAH concentrations were measured in yard trash at various management stages from 10 locations in Florida. The concentrations of 16 PAH compounds in processed yard trash ranged from 0.38 to 14 mg kg-1. PAH concentrations were detected in vegetative material harvested from a residential neighborhood, but were below the United States Environmental Protection Agency residential regional screening levels (RSLs). PAH concentrations near or above the RSLs were common in both unprocessed and processed yard trash collected at waste management facilities. PAH concentrations were amongst the highest in newly ground yard trash samples and were amongst the lowest in composted yard trash samples. These findings are important because land application of some waste materials, such as construction and demolition debris fines and street sweepings, are sometimes limited due to PAH. If processed yard trash, which is commonly land applied in residential settings, possesses similar PAH concentrations, evaluation of current risk assessment practices for land-applied wastes may require further examination.

Re-evaluating the TCLP's Role as the Regulatory Driver in the Management of Municipal Solid Waste Incinerator Ash.

Up to 30% of the municipal solid waste (MSW) that is incinerated for energy recovery ends up as MSW incinerator (MSWI) ash. In light of the large volume of MSWI ash and the expenses and regulatory burden if this ash were managed as a hazardous waste, U.S. MSWI facilities place great emphasis on ensuring MSWI ashes pass the toxicity characteristic leaching procedure (TCLP). The focus on passing the TCLP has the unintended consequence of making recycling more difficult and arguably making the ash less benign. This policy analysis examines current U.S. MSWI ash management practices in relation to the TCLP, and discusses the role of the TCLP as a regulatory driver in the management of MSWI ashes. A review of existing information, example data, and common MSWI ash management practices provide insight into potential issues with the current approach and opportunities for alternative directions.

Material- and Site-Specific Partition Coefficients for Beneficial Use Assessments.

Partition coefficient (Kd) values available in the literature are often used in fate and transport modeling conducted as part of beneficial use risk assessments for industrial byproducts. Because element partitioning depends on soil properties as well as characteristics of the byproduct leachate, site-specific Kd values may lead to more accurate risk assessment. In this study, contamination risk to groundwater of beneficially reused byproducts was assessed using batch leaching tests on waste to energy bottom ash and coal combustion fly ash. Leachates were equilibrated with eight different soils to obtain the waste-soil-specific Kd,exp values for the metals of interest. The Kd,exp values were used as inputs in the Industrial Waste Management Evaluation Model to demonstrate the degree to which Kd estimates affect risk assessment outcomes. Measured Kd,exp values for the most part fell within the large range of Kd values reported in the literature, but IWEM results using default Kd values for some types of soils resulted in overestimated risk compared to those derived from Kd,exp values. Modeled concentration at the receptor location was much lower for some elements for those soils with high concentrations of iron and aluminum.

Blending organic material with municipal solid waste incinerator bottom ash to promote in-situ carbonation in road base.

The use of municipal solid waste incinerator bottom ash for road-base construction is an accepted practice in Europe and Asia, and of growing interest in the US. It is common practice to cure bottom ash by stockpiling it for several weeks before using it in this application. The curing process exposes the bottom ash to atmospheric carbon dioxide, which promotes carbonation, lowering its pH (making it less alkaline), and making many heavy metals less soluble. While this process makes bottom ash a more environmentally acceptable material, it takes time and requires additional handling. This article investigates a concept to facilitate carbonation of bottom ash in its compacted state, potentially eliminating the stockpile curing process. It is demonstrated here that blending a small amount of organic material with bottom ash will accelerate carbonation and lower pH in compacted samples by providing a carbon source for bacteria to produce carbon dioxide. Different quantities of biosolids (1%, 2%, 3%, and 5% by mass) were added to compacted bottom ash samples to examine the effect of organic materials on carbonation, and results were compared with a compacted control bottom ash sample. The pH of the control bottom ash sample decreased from 12.07 to 9.78 after 63 days, while the pH of the sample containing 5% biosolids decreased from 11.70 to 9.74 in only 7 days and to 8.18 after 63 days. Physical testing was conducted to examine suitability for beneficial use. The results indicate that bottom ash containing less than 3% biosolids met minimum bearing strength requirements for road base.

Replacing Recycling Rates with Life-Cycle Metrics as Government Materials Management Targets.

In Florida, the passing of the Energy, Climate Change, and Economic Security Act of 2008 established a statewide mass-based municipal solid waste recycling rate goal of 75% by 2020. In this study, we describe an alternative approach to tracking performance of materials management systems that incorporates life-cycle thinking. Using both greenhouse gas (GHG) emissions and energy use as life-cycle indicators, we create two different materials management baselines based on a hypothetical 75% recycling rate in Florida in 2008. GHG emission and energy use footprints resulting from various 2020 materials management strategies are compared to these baselines, with the results normalized to the same mass-based 75% recycling rate. For most scenarios, LCI-normalized recycling rates are greater than mass-based recycling rates. Materials management strategies that include recycling of curbside-collected materials such as metal, paper, and plastic result in the largest GHG- and energy-normalized recycling rates. Waste prevention or increase, determined as the net difference in per-person mass discard rate for individual materials, is a major contributor to the life-cycle-normalized recycling rates. The methodology outlined here provides policy makers with one means of transitioning to life-cycle thinking in state and local waste management goal setting and planning.

Characterisation and management of concrete grinding residuals.

Concrete grinding residue is the waste product resulting from the grinding, cutting, and resurfacing of concrete pavement. Potential beneficial applications for concrete grinding residue include use as a soil amendment and as a construction material, including as an additive to Portland cement concrete. Concrete grinding residue exhibits a high pH, and though not hazardous, it is sufficiently elevated that precautions need to be taken around aquatic ecosystems. Best management practices and state regulations focus on reducing the impact on such aquatic environment. Heavy metals are present in concrete grinding residue, but concentrations are of the same magnitude as typically recycled concrete residuals. The chemical composition of concrete grinding residue makes it a useful product for some soil amendment purposes at appropriate land application rates. The presence of unreacted concrete in concrete grinding residue was examined for potential use as partial replacement of cement in new concrete. Testing of Florida concrete grinding residue revealed no dramatic reactivity or improvement in mortar strength.

Evaluation of a buried vertical well leachate recirculation system for municipal solid waste landfills.

Vertical liquids addition systems have been used at municipal landfills as a leachate management method and to enhance biostabilization of waste. Drawbacks of these systems include a limitation on pressurized injection and the occurrence of seepage. A novel vertical well system that employed buried wells constructed below a lift of compacted waste was operated for 153 days at a landfill in Florida, USA. The system included 54 wells installed in six clusters of nine wells connected with a horizontally-oriented manifold system. A cumulative volume of 8430 m3 of leachate was added intermittently into the well clusters over the duration of the project with no incidence of surface seeps. Achievable average flow rates ranged from 9.3 × 10-4 m3 s-1 to 14.2 × 10-4 m3 s-1, which was similar to or greater than flow rates achieved in a previous study using traditional vertical wells at the same landfill site. The results demonstrated that pressurized liquids addition in vertical wells at municipal solid waste landfills can be achieved while avoiding typical operational and maintenance issues associated with seeps.

Does Disposing of Construction and Demolition Debris in Unlined Landfills Impact Groundwater Quality? Evidence from 91 Landfill Sites in Florida.

More than 1,500 construction and demolition debris (CDD) landfills operate in the United States (U.S.), and U.S. federal regulations do not require containment features such as low-permeability liners and leachate collection systems for these facilities. Here we evaluate groundwater quality from samples collected in groundwater monitoring networks at 91 unlined, permitted CDD landfills in Florida, U.S. A total of 460,504 groundwater sample results were analyzed, with a median of 10 years of quarterly or semiannual monitoring data per site including more than 400 different chemical constituents. Downgradient concentrations of total dissolved solids, sulfate, chloride, iron, ammonia-nitrogen, and aluminum were greater than upgradient concentrations (p < 0.05). At downgradient wells where sulfate concentrations were greater than 150 mg/L (approximately 10% of the maximum dissolved sulfate concentration in water, which suggests the presence of leachate from the landfill), iron and arsenic were detected in 91% and 43% of samples, with median concentrations of 1,900 µg/L and 11 µg/L, respectively. These results show that although health-based standards can be exceeded at unlined CDD landfills, the magnitude of detected chemical concentrations is generally small and reflective of leached minerals from components (wood, concrete, and gypsum drywall) that comprise the bulk of discarded CDD by mass.

Chemical characterization of high-temperature arc gasification slag with a focus on element release in the environment.

High-temperature arc gasification (HTAG) has been proposed as a viable technology for the generation of energy and the production of saleable byproducts from municipal solid waste (MSW). Total concentrations of elements in HTAG slag were assessed and indicated a high partitioning of trace elements (Pb, Cd, and As) into the flue gas, an issue of concern when assessing the air pollution control residues (APCR) status as a hazardous waste. Hazardous waste leaching tests [such as the toxicity characteristic leaching procedure (TCLP)] were performed and confirmed that the slag did not meet U.S. criteria for a hazardous waste. Leaching was assessed using batch and column tests; the results revealed that Sb and Al were elevated in respect to risk-based regulatory thresholds. Slag samples were carbonated to simulate weathering effects, and although leachable concentrations of Al did decrease by an order of magnitude, Sb concentrations were found to increase. Low total concentrations of certain trace elements (As, Cd, and Pb), with respect to MSW incineration bottom ashes support the potential for reuse of HTAG slag; however, leaching of elements (Pb, Al, and Sb) in batch and column tests indicate that proper engineering controls would need to be taken to ensure protection of water supplies in a reuse application.

Life-cycle inventory and impact evaluation of mining municipal solid waste landfills.

Recent research and policy directives have emerged with a focus on sustainable management of waste materials, and the mining of old landfills represents an opportunity to meet sustainability goals by reducing the release of liquid- and gas-phase contaminants into the environment, recovering land for more productive use, and recovering energy from the landfilled materials. The emissions associated with the landfill mining process (waste excavation, screening, and on-site transportation) were inventoried on the basis of diesel fuel consumption data from two full-scale mining projects (1.3-1.5 L/in-place m(3) of landfill space mined) and unit emissions (mass per liter of diesel consumption) from heavy equipment typically deployed for mining landfills. An analytical framework was developed and used in an assessment of the life-cycle environmental impacts of a few end-use management options for materials deposited and mined from an unlined landfill. The results showed that substantial greenhouse gas emission reductions can be realized in both the waste relocation and materials and energy recovery scenarios compared to a "do nothing" case. The recovery of metal components from landfilled waste was found to have the greatest benefit across nearly all impact categories evaluated, while emissions associated with heavy equipment to mine the waste itself were found to be negligible compared to the benefits that mining provided.

Effect of water treatment additives on lime softening residual trace chemical composition--implications for disposal and reuse.

Drinking water treatment residues (WTR) offer potential benefits when recycled through land application. The current guidance in Florida, US allows for unrestricted land application of lime softening WTR; alum and ferric WTR require additional evaluation of total and leachable concentrations of select trace metals prior to land application. In some cases a mixed WTR is produced when lime softening is accompanied by the addition of a coagulant or other treatment chemical; applicability of the current guidance is unclear. The objective of this research was to characterize the total and leachable chemical content of WTR from Florida facilities that utilize multiple treatment chemicals. Lime and mixed lime WTR samples were collected from 18 water treatment facilities in Florida. Total and leachable concentrations of the WTR were measured. To assess the potential for disposal of mixed WTR as clean fill below the water table, leaching tests were conducted at multiple liquid to solid ratios and under reducing conditions. The results were compared to risk-based soil and groundwater contamination thresholds. Total metal concentrations of WTR were found to be below Florida soil contaminant thresholds with Fe found in the highest abundance at a concentration of 3600 mg/kg-dry. Aluminum was the only element that exceeded the Florida groundwater contaminant thresholds using SPLP (95% UCL = 0.23 mg/L; risk threshold = 0.2 mg/L). Tests under reducing conditions showed elevated concentrations of Fe and Mn, ranging from 1 to 3 orders of magnitude higher than SPLP leachates. Mixed lime WTR concentrations (total and leachable) were lower than the ferric and alum WTR concentrations, supporting that mixed WTR are appropriately represented as lime WTR. Testing of WTR under reducing conditions demonstrated the potential for release of certain trace metals (Fe, Al, Mn) above applicable regulatory thresholds; additional evaluation is needed to assess management options where reducing conditions may develop.

Anisotropy estimation of compacted municipal solid waste using pressurized vertical well liquids injection.

Waste hydraulic conductivity and anisotropy represent two important parameters controlling fluid movement in landfills, and thus are the key inputs in design methods where predictions of moisture movement are necessary. Although municipal waste hydraulic conductivity has been estimated in multiple laboratory and field studies, measurements of anisotropy, particularly at full scale, are rare, even though landfilled municipal waste is generally understood to be anisotropic. Measurements from a buried liquids injection well surrounded by pressure transducers at a full-scale landfill in Florida were collected and examined to provide an estimate of in-situ waste anisotropy. Liquids injection was performed at a constant pressure and the resulting pore pressures in the surrounding waste were monitored. Numerical fluid flow modeling was employed to simulate the pore pressures expected to occur under the conditions operated. Nine different simulations were performed at three different lateral hydraulic conductivity values and three different anisotropy values. Measured flowrate and pore pressures collected from conditions of approximate steady state were compared with the simulation results to assess the range of anisotropies. The results support that compacted municipal waste in landfills is anisotropic, provide anisotropy estimates greater than previous measurements, and suggest that anisotropy decreases with landfill depth.

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.