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Timothy G. Townsend - One of the best experts on this subject based on the ideXlab platform.
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wet Landfill decomposition rate determination using methane yield results for excavated waste samples
Waste Management, 2012Co-Authors: Hwidong Kim, Timothy G. TownsendAbstract:Abstract An increasing number of Landfills are operated to accelerate waste decomposition through liquids addition (e.g., leachate recirculation) as a wet Landfill. Landfill design and regulation often depend on utilizing Landfill gas production models that require an estimate of a first-order gas generation rate constant, k . Consequently, several studies have estimated k using collected gas volumes from operating wet Landfills. Research was conducted to examine an alternative approach in which k is estimated not from collected Landfill gas but from solid waste samples collected over time and analyzed for remaining gas yield. To achieve this goal, waste samples were collected from 1990 through 2007 at two full-scale Landfills in Florida that practiced liquids addition. Methane yields were measured from waste samples collected over time, including periods before and after leachate recirculation, and the results were applied to a first-order decay model to estimate rate constants for each of the sites. An initial, intensive processing step was conducted to exclude non-biodegradable components from the methane yield testing procedure. The resulting rate constants for the two Landfills examined were 0.47 yr −1 and 0.21 yr −1 . These results expectedly exceeded the United States Environmental Protection Agency’s rate constants for dry and conventional Landfills (0.02–0.05 yr −1 ), but they are comparable to wet Landfill rate constants derived using Landfill gas data (0.1–0.3 yr −1 ).
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Landfill disposal of cca treated wood with construction and demolition c d debris arsenic chromium and copper concentrations in leachate
Environmental Science & Technology, 2008Co-Authors: Jenna Jambeck, Timothy G. Townsend, Helena M SologabrieleAbstract:Although phased out of many residential uses in the United States, the disposal of CCA-treated wood remains a concern because significant quantities have yet to be taken out of service, and it is commonly disposed in Landfills. Catastrophic events have also led to the concentrated disposal of CCA-treated wood, often in unlined Landfills. The goal of this research was to simulate the complex chemical and biological activity of a construction and demolition (C&D) debris Landfill containing a realistic quantity of CCA-treated wood (10% by mass), produce leachate, and then evaluate the arsenic, copper, and chromium concentrations in the leachate as an indication of what may occur in a Landfill setting. Copper concentrations were not significantly elevated in the control or experimental simulated Landfill setting (α = 0.05). However, the concentrations of arsenic and chromium were significantly higher in the experimental simulated Landfill leachate compared to the control simulated Landfill leachate (α = 0.05,...
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Landfill disposal of cca treated wood with construction and demolition c d debris arsenic chromium and copper concentrations in leachate
Environmental Science & Technology, 2008Co-Authors: Jenna Jambeck, Timothy G. Townsend, Helena M SologabrieleAbstract:Although phased out of many residential uses in the United States, the disposal of CCA-treated wood remains a concern because significant quantities have yet to be taken out of service, and it is commonly disposed in Landfills. Catastrophic events have also led to the concentrated disposal of CCA-treated wood, often in unlined Landfills. The goal of this research was to simulate the complex chemical and biological activity of a construction and demolition (C&D) debris Landfill containing a realistic quantity of CCA-treated wood (10% by mass), produce leachate, and then evaluate the arsenic, copper, and chromium concentrations in the leachate as an indication of what may occur in a Landfill setting. Copper concentrations were not significantly elevated in the control or experimental simulated Landfill setting (alpha = 0.05). However, the concentrations of arsenic and chromium were significantly higher in the experimental simulated Landfill leachate compared to the control simulated Landfill leachate (alpha = 0.05, p < 0.001). This indicates that disposal of CCA-treated wood with C&D debris can impact leachate quality which, in turn could affect leachate management practices or aquifers below unlined Landfills.
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reduced sulfur compounds in gas from construction and demolition debris Landfills
Waste Management, 2006Co-Authors: Qiyong Xu, Timothy G. Townsend, Matthew M Booth, Paul A Chadik, Gabriel BittonAbstract:Abstract The biological conversion of sulfate from disposed gypsum drywall to hydrogen sulfide (H2S) in the anaerobic environment of a Landfill results in odor problems and possible health concerns at many disposal facilities. To examine the extent and magnitude of such emissions, Landfill gas samples from wells, soil vapor samples from the interface of the waste and cover soil, and ambient air samples, were collected from 10 construction and demolition (C&D) debris Landfills in Florida and analyzed for H2S and other reduced sulfur compounds (RSC). H2S was detected in the well gas and soil vapor at all 10 sites. The concentrations in the ambient air above the surface of the Landfill were much lower than those observed in the soil vapor, and no direct correlation was observed between the two sampling locations. Methyl mercaptan and carbonyl sulfide were the most frequently observed other RSC, though they occurred at smaller concentrations than H2S. This research confirmed the presence of H2S at C&D debris Landfills. High concentrations of H2S may be a concern for employees working on the Landfill site. These results indicate that workers should use proper personal protection at C&D debris Landfills when involved in excavation, Landfill gas collection, or confined spaces. The results indicate that H2S is sufficiently diluted in the atmosphere to not commonly pose acute health impacts for these Landfill workers in normal working conditions. H2S concentrations were extremely variable with measurements occurring over a very large range (from less than 3 ppbv to 12,000 ppmv in the soil vapor and from less than 3 ppbv to 50 ppmv in ambient air). Possible reasons for the large intra- and inter-site variability observed include waste and soil heterogeneities, impact of weather conditions, and different site management practices.
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Landfill bioreactor design operation
1997Co-Authors: Debra R. Reinhart, Timothy G. TownsendAbstract:Introduction Scope and Objectives The Evolution of Landfills for Waste Management Landfills as Bioreactors Regulatory Status Organization of the Book Modern Landfill Fundamentals Introduction Overview of Modern Sanitary Landfills Landfill Containment Systems Collection and Control of Leachate Leachate Collection and Storage Leachate and Gas Management at MSW Landfills Landfill Operation Strategies Landfill Bioreactor Studies Laboratory Scale Studies Pilot-Scale Bioreactor Studies Full-Scale Landfill Bioreactor Studies Summary Full-Scale Experiences with Bioreactor Landfills - Case Studies Introduction Southwest Landfill, Alachua County, Florida Central Facility Landfill, Worcester County, Maryland Winfield Landfill, Columbia County, Florida Pecan Row Landfill, Lowndes County, Georgia Lower Mount Washington Valley Secure Landfill, Conway, New Hamshire Coastal Regional Solid Waste Management Authority Landfill, Craven County, North Carolina Lemons Landfill, Stoddard County, Missouri Mill Seat Landfill, Monroe County, New York Yolo County Landfill, California Additional Full-Scale Efforts The Hydrodynamics of Leachate Recirculating Landfills Introduction Leachate Generation Moisture Movement Unsaturated Leachate Flow Mathematical Modeling of Leachate Recirculation Leachate Recirculation Field Testing The Impact of Leachate Recirculation of Leachate and Gas Characteristics Introduction Leachate Characteristics of Recirculating Landfills Leachate Treatment Implications Leachate Quantities Gas Production Landfill Bioreactor Design Introduction Liner/Leachate Collection System Leachate Storage Leachate Reintroduction Systems Leachate Recirculation System Design Final and Intermediate Caps Gas Collection Cell Construction Construction Costs Summary Landfill Bioreactor Operation Introduction Waste Characterization Oxidation Reduction Conditions Moisture Content Recirculation Strategies Effects of Waste Placement Rate Use of Old Cells Bioreactor Augmentation Daily and Intermediate Covers Settlement Monitoring When is the Waste Stable? Materials Recovery and Reuse from Bioreactor Landfills Introduction Landfill Treatment and Reclamation Strategies Mass Balance Design for Landfill Reclamation Methods of Landfill Reclamation Previous Experience with Landfill Reclamation Use of Reclaimed Materials Future Directions for Bioreactor Landfills References Index
Dongsheng Shen - One of the best experts on this subject based on the ideXlab platform.
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leaching behavior of iron from simulated Landfills with different operational modes
Bioresource Technology, 2011Co-Authors: Jun Yao, Dongsheng Shen, Fangfang Xia, Huajun Feng, Huan Feng, Chenjing Jiang, Chengran FangAbstract:Abstract The aim of the present study was to investigate the leaching behavior of iron from simulated Landfills with different operation modes, with an emphasis on the variation of iron in different oxidation state, ferrous Fe(II) and ferric Fe(III) percentage and the distribution of iron content in different Landfill leachate fractions. The leaching behavior and accumulated amounts of iron leached out by leachate from conventional Landfill (CL) and leachate recirculated Landfill (RL) exhibited decidedly different trends except for the initial 28 days. In addition, the percentage of iron leached from CL and RL accounted 1.00% and 0.14% for the total amount in Landfills, respectively. No correlations between iron and selected characteristics in leachate were found were observed in the two simulated Landfills. Significant positive correlations between particulate bound iron and Fe(III) were found in the leachates from RL (R2 = 0.748) and CL (R2 = 0.833).
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migration behavior of cu and zn in Landfill with different operation modes
Journal of Hazardous Materials, 2010Co-Authors: Yuyang Long, Dongsheng Shen, Hongtao WangAbstract:Cu and Zn were chosen to study the heavy metal migration behavior and mechanism in three simulated Landfills with different operation modes, namely conventional Landfill (CL), leachate directly recirculated Landfill (RL) and leachate pre-treated bioreactor Landfill (BL). It showed that Cu and Zn in refuse experienced periodic migration and retention gradually during decomposition, and the variation of Cu(II) and Zn(II) in leachate correspondingly reflected the releasing behavior of Cu and Zn in Landfill refuse at different stabilization stages. Except for their accumulated leaching amounts, Cu(II) and Zn(II) concentrations in leachate from Landfills with different operation modes had no significant difference. The accumulated leaching amounts of Cu and Zn from CL showed exponential increase, while those of RL and BL showed exponential decay. The operation of bioreactor Landfill with leachate recirculation can obviously attenuate the heavy metal leaching than conventional operation. The introduction of methanogenic reactor (MR) in bioreactor Landfill can further promote the immobilization of heavy metal in refuse than leachate recirculation directly.
Morton A. Barlaz - One of the best experts on this subject based on the ideXlab platform.
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national estimate of per and polyfluoroalkyl substance pfas release to u s municipal Landfill leachate
Environmental Science & Technology, 2017Co-Authors: Johnsie R Lang, Mckay B Allred, Jennifer A Field, James W Levis, Morton A. BarlazAbstract:Landfills are the final stage in the life cycle of many products containing per- and polyfluoroalkyl substances (PFASs) and their presence has been reported in Landfill leachate. The concentrations of 70 PFASs in 95 samples of leachate were measured in a survey of U.S. Landfills of varying climates and waste ages. National release of PFASs was estimated by coupling measured concentrations for the 19 PFASs where more than 50% of samples had quantifiable concentrations, with climate-specific estimates of annual leachate volumes. For 2013, the total volume of leachate generated in the U.S. was estimated to be 61.1 million m3, with 79% of this volume coming from Landfills in wet climates (>75 cm/yr precipitation) that contain 47% of U.S. solid waste. The mass of measured PFASs from U.S. Landfill leachate to wastewater treatment plants was estimated to be between 563 and 638 kg for 2013. In the majority of Landfill leachate samples, 5:3 fluorotelomer carboxylic acid (FTCA) was dominant and variations in concen...
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National Estimate of Per- and Polyfluoroalkyl Substance (PFAS) Release to U.S. Municipal Landfill Leachate
2017Co-Authors: Johnsie R Lang, Mckay B Allred, Jennifer A Field, James W Levis, Morton A. BarlazAbstract:Landfills are the final stage in the life cycle of many products containing per- and polyfluoroalkyl substances (PFASs) and their presence has been reported in Landfill leachate. The concentrations of 70 PFASs in 95 samples of leachate were measured in a survey of U.S. Landfills of varying climates and waste ages. National release of PFASs was estimated by coupling measured concentrations for the 19 PFASs where more than 50% of samples had quantifiable concentrations, with climate-specific estimates of annual leachate volumes. For 2013, the total volume of leachate generated in the U.S. was estimated to be 61.1 million m3, with 79% of this volume coming from Landfills in wet climates (>75 cm/yr precipitation) that contain 47% of U.S. solid waste. The mass of measured PFASs from U.S. Landfill leachate to wastewater treatment plants was estimated to be between 563 and 638 kg for 2013. In the majority of Landfill leachate samples, 5:3 fluorotelomer carboxylic acid (FTCA) was dominant and variations in concentrations with waste age affected total estimated mass. There were six PFASs that demonstrated significantly higher concentrations in leachate from younger waste compared to older waste and six PFAS demonstrated significant variation with climate
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using observed data to improve estimated methane collection from select u s Landfills
Environmental Science & Technology, 2013Co-Authors: Xiaoming Wang, Ajay Singh Nagpure, Joseph F Decarolis, Morton A. BarlazAbstract:The anaerobic decomposition of solid waste in a Landfill produces methane, a potent greenhouse gas, and if recovered, a valuable energy commodity. Methane generation from U.S. Landfills is usually estimated using the U.S. EPA's Landfill Gas Emissions Model (LandGEM). Default values for the two key parameters within LandGEM, the first-order decay rate (k) and the methane production potential (L0) are based on data collected in the 1990s. In this study, observed methane collection data from 11 U.S. Landfills and estimates of gas collection efficiencies developed from site-specific gas well installation data were included in a reformulated LandGEM equation. Formal search techniques were employed to optimize k for each Landfill to find the minimum sum of squared errors (SSE) between the LandGEM prediction and the observed collection data. Across nearly all Landfills, the optimal k was found to be higher than the default AP-42 of 0.04 yr −1 and the weighted average decay for the 11 Landfills was 0.09 − 0.12 yr −1 . The results suggest that the default k value assumed in LandGEM is likely too low, which implies that more methane is produced in the early years following waste burial when gas collection efficiencies tend to be lower.
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a performance based system for the long term management of municipal waste Landfills
Waste Management, 2011Co-Authors: Jeremy W F Morris, Morton A. BarlazAbstract:Landfills have been the dominant alternative for disposal of solid waste and there are tens of thousands of closed Landfills throughout the world that require a long-term management strategy. In contrast to approaches based on time or target values, this paper describes a performance-based methodology for evaluation of post-closure care (PCC). Using the methodology, critical components of PCC at a Landfill, including leachate and gas management, groundwater monitoring and cover integrity, are considered to determine whether a Landfill meets defined conditions for functional stability and can transition from regulated PCC to a post-regulatory custodial care program representing de minimus care activities only. The methodology is predicated on understanding the biological, chemical, and physical behavior of a Landfill and the presence of sufficient data to verify expected trends in Landfill behavior. If an evaluation suggests that a change can be made to PCC, the Landfill owner must perform confirmation monitoring and then surveillance monitoring at a decreasing frequency to verify that the change is protective of human health and the environment. A hypothetical case study showed that using the methodology to evaluate site-specific PCC requirements could result in increased environmental protection at comparable cost by spending available funds where they are most needed.
Hongtao Wang - One of the best experts on this subject based on the ideXlab platform.
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fugitive halocarbon emissions from working face of municipal solid waste Landfills in china
Waste Management, 2017Co-Authors: Wenjing Lu, Wafa Dastyar, Xindi Fu, Ruihong Meng, Hao Li, Ming Zhao, Hongtao WangAbstract:Abstract Halocarbons are important anthropogenic greenhouse gases (GHGs) due to their long lifetime and large characteristic factors. The present study for the first time assessed the global warming potential (GWP) of fugitive halocarbon emissions from the working face of Landfills in China. The national emissions of five major halocarbons (CFC-11, CFC-113, CH2Cl2, CHCl3 and CCl4) from the working face of municipal solid waste Landfills in China were provided through observation-based estimations. The fluxes of halocarbons from working face of Landfills were observed much higher than covered cells in Landfills hence representing the hot spots of Landfill emissions. The annual emissions of the halocarbons from Landfills in China were 0.02–15.6 kt·y−1, and their GWPs were 128–60,948 kt-CO2-eq·y−1 based on their characteristic factors on a 100-year horizon. CFC-113 was the dominant species owing to its highest releasing rate (i.e. 15.4 ± 19.1 g·t−1) and largest characteristic factor, resulting in a GWP up to 4036 ± 4855 kt-CO2-eq·y−1. The annual emissions of CFC-113 from Landfills (i.e. 0.61 kt·y−1) made up ∼76% of the total national CFC-113 emissions. The GWPs of halocarbons were estimated ∼14.4% of Landfill methane emissions. Therefore, fugitive halocarbons emissions from working face are significant sources of GHGs in Landfill sites in China, although they comprise a small fraction of total Landfill gases.
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migration behavior of cu and zn in Landfill with different operation modes
Journal of Hazardous Materials, 2010Co-Authors: Yuyang Long, Dongsheng Shen, Hongtao WangAbstract:Cu and Zn were chosen to study the heavy metal migration behavior and mechanism in three simulated Landfills with different operation modes, namely conventional Landfill (CL), leachate directly recirculated Landfill (RL) and leachate pre-treated bioreactor Landfill (BL). It showed that Cu and Zn in refuse experienced periodic migration and retention gradually during decomposition, and the variation of Cu(II) and Zn(II) in leachate correspondingly reflected the releasing behavior of Cu and Zn in Landfill refuse at different stabilization stages. Except for their accumulated leaching amounts, Cu(II) and Zn(II) concentrations in leachate from Landfills with different operation modes had no significant difference. The accumulated leaching amounts of Cu and Zn from CL showed exponential increase, while those of RL and BL showed exponential decay. The operation of bioreactor Landfill with leachate recirculation can obviously attenuate the heavy metal leaching than conventional operation. The introduction of methanogenic reactor (MR) in bioreactor Landfill can further promote the immobilization of heavy metal in refuse than leachate recirculation directly.
Peter Kjeldsen - One of the best experts on this subject based on the ideXlab platform.
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quantification of methane emissions from 15 danish Landfills using the mobile tracer dispersion method
Waste Management, 2015Co-Authors: Jacob Monster, Jerker Samuelsson, Peter Kjeldsen, Charlotte ScheutzAbstract:Highlights: • Quantification of whole Landfill site methane emission at 15 Landfills. • Multiple on-site source identification and quantification. • Quantified methane emission from shredder waste and composting. • Large difference between measured and reported methane emissions. - Abstract: Whole-site methane emissions from 15 Danish Landfills were assessed using a mobile tracer dispersion method with either Fourier transform infrared spectroscopy (FTIR), using nitrous oxide as a tracer gas, or cavity ring-down spectrometry (CRDS), using acetylene as a tracer gas. The Landfills were chosen to represent the different stages of the lifetime of a Landfill, including open, active, and closed covered Landfills, as well as those with and without gas extraction for utilisation or flaring. Measurements also included Landfills with biocover for oxidizing any fugitive methane. Methane emission rates ranged from 2.6 to 60.8 kg h{sup −1}, corresponding to 0.7–13.2 g m{sup −2} d{sup −1}, with the largest emission rates per area coming from Landfills with malfunctioning gas extraction systems installed, and the smallest emission rates from Landfills closed decades ago and Landfills with an engineered biocover installed. Landfills with gas collection and recovery systems had a recovery efficiency of 41–81%. Landfills where shredder waste was deposited showed significant methane emissions,more » with the largest emission from newly deposited shredder waste. The average methane emission from the Landfills was 154 tons y{sup −1}. This average was obtained from a few measurement campaigns conducted at each of the 15 Landfills and extrapolating to annual emissions requires more measurements. Assuming that these Landfills are representative of the average Danish Landfill, the total emission from Danish Landfills were calculated at 20,600 tons y{sup −1}, which is significantly lower than the 33,300 tons y{sup −1} estimated for the national greenhouse gas inventory for 2011.« less
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Tracer method to measure Landfill gas emissions from leachate collection systems.
Waste Management, 2010Co-Authors: Anders Michael Fredenslund, Charlotte Scheutz, Peter KjeldsenAbstract:Abstract This paper describes a method developed for quantification of gas emissions from the leachate collection system at Landfills and present emission data measured at two Danish Landfills with no Landfill gas collection systems in place: Fakse Landfill and AV Miljo. Landfill top covers are often designed to prevent infiltration of water and thus are made from low permeable materials. At such sites a large part of the gas will often emit through other pathways such as the leachate collection system. These point releases of gaseous constituents from these locations cannot be measured using traditional flux chambers, which are often used to measure gas emissions from Landfills. Comparing tracer measurements of methane (CH 4 ) emissions from leachate systems at Fakse Landfill and AV Miljo to measurements of total CH 4 emissions, it was found that approximately 47% (351 kg CH 4 d −1 ) and 27% (211 kg CH 4 d −1 ), respectively, of the CH 4 emitting from the sites occurred from the leachate collection systems. Emission rates observed from individual leachate collection wells at the two Landfills ranged from 0.1 to 76 kg CH 4 d −1 . A strong influence on emission rates caused by rise and fall in atmospheric pressure was observed when continuously measuring emission from a leachate well over a week. Emission of CH 4 was one to two orders of magnitude higher during periods of decreasing pressure compared to periods of increasing pressure.
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characterization of an old municipal Landfill grindsted denmark as a groundwater pollution source Landfill hydrology and leachate migration
Waste Management & Research, 1998Co-Authors: Peter Kjeldsen, Aase Grundtvig, Pia Winther, Jens Strodl AndersenAbstract:Investigations into the pollution of groundwater from old Landfills have, in most cases, focused on delineating the pol lution plume rather than on the Landfill as a source of ground water pollution. Landfills often cover large areas and spatial variations in leachate composition within the Landfill may have great impact on the location of the main pollution plume in the downstream aquifer. The history of the Grind sted Landfill in Denmark was investigated using aerial photo graphs and interviews. On the basis of the aerial photographs, waste volume and age of the different areas of the Landfill were evaluated. A pronounced variability in leachate compo sition was observed in the 31 leachate wells installed through the waste. The spatial variability was analysed by statistical methods, and a semivariogram model was able to describe the variability both on small and large scale. The spatial varia tions in leachate composition are very important for locating the main source of the groundwater pollution and ...
