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Gainesville, FL, United States

Jain P.,Innovative Waste Consulting Services | Townsend T.G.,University of Florida
Waste Management | Year: 2013

A landfill reclamation project was considered to recover landfill airspace and soil, reduce future groundwater impacts by removing the waste buried in the unlined area, and optimize airspace use at the site. A phased approach was utilized to evaluate the technical and economic feasibility of the reclamation project; based on the results of these evaluations, approximately 6.8. ha of the unlined cells were reclaimed. Approximately 371,000 in-place cubic meters of waste was mined from 6.8. ha in this project. Approximately 230,600 cubic meters of net airspace was recovered due to beneficial use of the recovered final cover soil and reclaimed soil as intermediate and daily cover soil, respectively, for the current landfill operations. This paper presents the researchers' landfill reclamation project experience, including a summary of activities pertaining to reclamation operations, an estimation of reclamation rates achieved during the project, project costs and benefits, and estimated composition of the reclaimed materials. © 2012 Elsevier Ltd. Source

Xu Q.,Innovative Waste Consulting Services | Xu Q.,Peking University | Tolaymat T.,U.S. Environmental Protection Agency | Townsend T.G.,University of Florida
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2012

The addition of liquids to municipal solid waste landfills, a practice sometimes performed under pressure to promote moisture distribution, has the potential to affect slope stability as a result of increased pore water pressure (and reduced shear strength) in the landfilled waste. Liquids addition into waste by using buried horizontal trenches was modeled to determine pore water pressure distributions, and the resulting effect on slope stability was assessed for different operational strategies. Model results using typical mechanical properties for solid waste found that pressurized liquids addition under a sloped landfill surface was possible without inducing a slope failure, providing liquids distribution was not obstructed. A reduction in the factor of safety occurred when simulating a poorly functioning leachate collection and removal system, a low-permeability cover layer within the landfill, a seepage control strategy using low-permeability soil, high liquids addition pressures, and waste permeability decreasing with depth. The sensitivity of the model results to input parameters was evaluated and graphically presented. The results demonstrate how pressurized liquids addition has the potential to affect slope stability and provide important insights for engineers charged with designing and permitting such systems. © 2012 American Society of Civil Engineers. Source

Xu Q.,University of Science and Technology of China | Powell J.,Innovative Waste Consulting Services | Tolaymat T.,U.S. Environmental Protection Agency | Townsend T.G.,University of Florida
Journal of Hazardous, Toxic, and Radioactive Waste | Year: 2013

The occurrence of leachate seepage at side slopes of municipal solid waste landfills represents a major design and operational concern at bioreactor landfills where leachate is recirculated into the waste mass to enhance degradation of organic materials. Full-scale bioreactor landfills typically add liquids to the waste under pressure to optimize moisture distribution. When liquids are added at a high pressure or at a flow rate higher than the absorption capacity of the waste mass, there is a possibility of seeps. Two general approaches to controlling landfill leachate seepage are described: a less aggressive strategy where liquid volumes are limited to avoid seeps and a more aggressive strategy where seeps are more likely to occur but with design and operation considerations in place to mitigate seepage. Liquids addition into waste using buried horizontal trenches was modeled to determine moisture distribution under a variety of conditions most likely to lead to leachate seepage at bioreactor landfills. Based on the modeling results, leachate seepage can occur in the presence of both high- and low-permeability soil layers. In addition, the injection pressure and setback distance of recirculation devices play important roles in seepage prevention and control. Several practical seepage control strategies are illustrated, including the selection and placement of daily or intermediate cover materials, pressure control, and the application of a clay plug as part of recirculation device design and construction. Finally, the setback distance for a horizontal injection trench was calculated based on the saturated zone equation; the setback distance provides a way to estimate the appropriate recirculation device design distance to prevent seepage at bioreactor landfills. © 2013 American Society of Civil Engineers. Source

Ko J.H.,Peking University | Powell J.,Innovative Waste Consulting Services | Jain P.,Innovative Waste Consulting Services | Kim H.,Gannon University | And 2 more authors.
Journal of Hazardous, Toxic, and Radioactive Waste | Year: 2013

The addition of air to landfilled municipal solid waste (MSW) was examined at an operating bioreactor landfill in Florida. An airaddition system was designed to provide sufficient capacity to aerobically degrade a targeted mass of waste in a 3-year period. Approximately 1.385 million standard m3 [at 15.5°C and 101.3 kPa (1 atm)] of air in total was added to 78 small-diameter vertical wells located in clusters of three different depths (6, 12, and 18 m deep in the landfill). The cumulative volume of air added was much less than design capacity, a result of difficulties in adding air to deeper and wetter landfill areas and rapid temperature increases in waste near some of the wells. Consistent long-term aerobic conditions could never be established. Gas concentration measurements throughout the experiments were not in the explosive range, but temperature measurements corresponding to continuous air addition did require frequent adjustment and cessation of air addition to wells to avoid fire formation. Although air addition could play some role in bioreactor landfill operation, results from this study suggest that maintaining aerobic conditions as the dominant waste decomposing environment within typical large bioreactor landfills operated with liquids addition is very difficult to achieve. © 2013 American Society of Civil Engineers. Source

Pleasant S.,University of Florida | O'Donnell A.,University of Florida | Powell J.,Innovative Waste Consulting Services | Jain P.,Innovative Waste Consulting Services | Townsend T.,University of Florida
Science of the Total Environment | Year: 2014

High concentrations of iron (Fe(II)) and manganese (Mn(II)) reductively dissolved from soil minerals have been detected in groundwater monitoring wells near many municipal solid waste landfills. Air sparging and vadose zone aeration (VZA) were evaluated as remedial approaches at a closed, unlined municipal solid waste landfill in Florida, USA. The goal of aeration was to oxidize Fe and Mn to their respective immobile forms. VZA and shallow air sparging using a partially submerged well screen were employed with limited success (Phase 1); decreases in dissolved iron were observed in three of nine monitoring wells during shallow air sparging and in two of 17 wells at VZA locations. During Phase 2, where deeper air sparging was employed, dissolved iron levels decreased in a significantly greater number of monitoring wells surrounding injection points, however no radial pattern was observed. Additionally, in wells affected positively by air sparging (mean total iron (FeTOT) <4.2mg/L, after commencement of air sparging), rising manganese concentrations were observed, indicating that the redox potential of the groundwater moved from an iron-reducing to a manganese-reducing environment. The mean FeTOT concentration observed in affected monitoring wells throughout the study was 1.40mg/L compared to a background of 15.38mg/L, while the mean Mn concentration was 0.60mg/L compared to a background level of 0.27mg/L. Reference wells located beyond the influence of air sparging areas showed little variation in FeTOT and Mn, indicating the observed effects were the result of air injection activities at study locations and not a natural phenomenon. Air sparging was found effective in intercepting plumes of dissolved Fe surrounding municipal landfills, but the effect on dissolved Mn was contrary to the desired outcome of decreased Mn groundwater concentrations. © 2014. Source

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