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Final Report: Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region
EPA Grant Number: R827933C020Subproject: this is subproject number 020 , established and managed by the Center Director under grant R825427
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: Urban Waste Management and Research Center (University New Orleans)
Center Director: McManis, Kenneth
Title: Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region
Investigators: Sansalone, John , Cartledge, Frank K. , Tittlbaum, Marty
Institution: Louisiana State University - Baton Rouge , University of New Orleans
EPA Project Officer: Krishnan, Bala S.
Project Period: July 1, 2000 through June 30, 2003
RFA: Urban Waste Management & Research Center (1998)
Research Category: Targeted Research
Description:
Objective:The objectives of this subproject are to: (1) develop an experimental bench scale clay liner; (2) evaluate the influence of cyclic interfacial redox conditions on the structure, porosity, integrity, and chemistry of clay liners; and (3) determine heavy metal mobility, clay liner interactions from leachate heavy metals under the influence of cyclic interfacial redox conditions generated by variable high groundwater conditions simulated in bench scale experiments.
Summary/Accomplishments (Outputs/Outcomes):Physical and chemical characteristics of landfill clay liner materials contribute significantly to their heavy metal isolation performance. The understanding of these characteristics is critical to evaluation of the isolation processes and the viability of the clay as a landfill liner material. In this subproject, basic indices of the three clay materials, Na-bentonite, kaolin, and Amite soil (sandy silty clay), were investigated. The results indicate that bentonite has the highest specific surface area and surface charge, whereas Amite soil has the lowest specific surface area and surface charge. Surface complexation models, including the constant capacitance model, the diffuse-layer model, and the triple-layer model, were used to model the potentiometric titration processes of the clay materials. A series of geochemistry algorithms were employed to examine surface phenomena. It was found that the surface complexation model could explain the experimental data and quantify the acidity constants of the clays. For the three clay materials tested, the constant capacitance model and the double-layer model could develop very similar acidity constant values. Although ionic strength had little effect on the protonation and deprotonation of kaolin, the protonation and deprotonation of bentonite and Amite soil increased with increasing ionic strength. Scanning electron microscopy spectral analyses suggest that interaction of metal species with bentonite is predominantly an ion exchange process.
The competitive interactions of Cu, Zn, Cd, and Pb with bentonite, kaolinite, and a native (sandy silty clay) soil (Amite soil) were investigated, and Freundlich isotherms were utilized to describe the experimental data. The results indicated that the adsorption capacities of the three clay materials decreased in the order: bentonite > Amite Soil > kaolin. The relative affinities of the four metals for the three clays followed a consistent trend with Pb > Cu > Zn > Cd. The analysis of interaction parameters of metal speciess on the clay materials indicates that Cu was preferentially adsorbed compared to Zn and Cd, whereas Pb was preferentially adsorbed compared to Cu for bentonite, kaolinite, and Amite soils. Metal species interaction with bentonite exhibited an ion exchange behavior. Ion exchange isotherms were interpreted in terms of metal species exchange selectivity. Results indicate that the selectivity for Pb could be altered by the presence of Cu, Zn, and Cd. The selectivity of the exchange reactions for Cu, Zn, and Cd, however, exhibited little change for combinations of these metals. This research indicates that with respect to selection and use of clay materials for landfill liners to contain metal species leachate, competitive adsorption must be considered. In addition to functioning as a physical separation barrier, clay materials can function as reactive barriers that exhibit selectivity for metal species.
A surface complexation model (the diffuse-layer model) was developed to model the adsorption of Cu, Zn, Cd, and Pb on to three clay liner materials, including bentonite, kaolin, and Amite soil at constant ionic strength (0.01 NaNO3). By using the previously determined acidity constants of the clay liner materials, the complexation constants of each metal species with the clay liner materials were determined under different experimental conditions, including mono-element and multiple-element systems. The parameters determined from the mono-element systems were then compared with those obtained from the multiple-element system, including a mixture of the four metal species, Mg, and Ca. The result indicated that there is little variation of the intrinsic surface complexation constants. Based on the analysis of values, it was found that the affinities of the clays for metal species increased in the order of kaolin < Amite soil < bentonite, whereas the affinities of the metal species for the clays increased in the order of Cd < Zn < Cu < Pb. Metal speciation also was investigated, and it was found that the distributions of metal species concentration in aqueous phase and solid were pH dependent, and they changed relatively slowly when kaolin was used as an adsorbent. The prediction of binding decrease as a result of competitive interaction was carried out with the aid of the three-dimensional graphs that were functions of pH and initial metal species concentration. It was suggested that the effect of competitive interaction was not significant at high pH and low initial metal concentration for the interaction of the four metals with bentonite. Competitive interaction, however, could reduce metal species binding in multiple-element system when pH was low or initial metal concentration was high. Binding decrease was very sensitive to the change of initial concentration at low pH value. The introduction of Mg and Ca could lead to the binding decrease of metal species onto the clay liner materials.
The kinetics models of metal species binding onto clays and compacted clay liner materials were applied in this research to describe the concentration decay in the batch model experiments. First order reaction, second order reaction, and the Elovich equation were used initially to describe metal species binding onto dispersed clays. It was found that first order reaction was the best of the three models investigated. The highest values of the adsorption rate constant were obtained for Pb and followed by Cu and Zn, whereas Cd had the smallest value of reaction constant. Metal species binding onto uncompacted clays followed the order of: bentonite > Amite soil > kaolin. Unlike dispersed clays, metal species binding onto compacted clays was a very slow process. Although the order of metal species in the adsorption process did not change, the order of clays followed bentonite > kaolin > Amite soil. The shrinking-core model and the pore and surface diffusion model were tested to model the transport of metal species in compacted clays. The models indicated the pore water diffusivities of the four metal species within the compacted bentonite, kaolin, and Amite soil were in the order of magnitudes of 10-10, 10-10, and 10-10 cm2/s, respectively. It also was found that both the shrinking-core model and the pore and surface diffusion model could well simulate heterogeneous metal species binding onto compacted clay liner materials. The analysis of the relative importance of pore and surface diffusions in the effective diffusivity indicated that pore diffusion and surface diffusion were dominant within compacted bentonite and kaolin, respectively, whereas both pore and surface diffusions were equally important within compacted Amite soil. A simple linear regression between metal species bound per unit mass of compacted clays and square root of time was made and the results indicated that this simple relationship was valid during the time interval investigated.
The role of redox potential on the porosity and hydraulic conductivity of the three landfill liner materials, including bentonite, kaolin, and Amite soil was investigated. The porosities of the clay liners were estimated from the clay-water characteristic curves. At the optimum moisture content, bentonite clay liner had the highest, whereas Amite soil had the lowest porosity. Bentonite, however, showed the smallest hydraulic conductivity, whereas kaolin possessed the highest hydraulic conductivity. It was found that Darcy’s law no longer applied for the compacted clay liners and a modified Darcy’s law, which was a power law function, was developed instead to describe the relation between water flow rate and hydraulic gradient. Clay liners were exposed to cyclic redox potential (- 200 mV, 0 mV, and + 300mV) and coupled pH (5, 6, and 7) changes in this subproject. The experimental results indicate that some parameters, such as pore size distribution and hydraulic conductivity, were changed for bentonite and Amite soil clay liners. Kaolin clay liner, however, showed little changes in either porosity or hydraulic conductivity. The increase in hydraulic conductivity of the clay liner was attributed to the increase in the portion of larger pores, which could be reflected by the increase in the leachate metal transport rate after the clay liners were subjected to cyclic redox potential and coupled pH changes. The relative order of the metal migration rate within the clay liners followed the order of Ca > Pb > Cu > Zn ˜ Cd > Mg, whereas the order of the clay transporting capacity followed bentonite > kaolin > Amite soil.
Supplemental Keywords:storm water, residuals, clay liner materials, heavy metal, surface area, surface complexation model, SEM analysis, pycnometry, Freundlich isotherm, competitive interaction, clay, metal species binding kinetics, first order reaction, shrinking-core model, redox potential, pH, porosity, hydraulic conductivity, diffuse-layer model, competitive adsorption, FITEQL, MINTEQ, speciation,
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INTERNATIONAL COOPERATION, Scientific Discipline, Waste, Civil/Environmental Engineering, Ecological Risk Assessment, Environmental Engineering, Municipal, Civil Engineering, Urban and Regional Planning, Engineering, evaluation of leaching, landfill design, solid waste, clay liners, landfill operation, municipal solid waste landfills, redox conditions, metals, municipal waste
Progress and Final Reports:
2000 Progress Report
Original Abstract
Main Center Abstract and Reports:
R825427 Urban Waste Management and Research Center (University New Orleans)
Subprojects under this Center:
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825427C001 Comprehensive Evaluation of The Dual Trickling Filter Solids Contact Process
R825427C002 Issues Involving the Vertical Expansion of Landfills
R825427C003 Deep Foundations on Brownfields Sites
R825427C004 Ambient Particulate Concentration Model for Traffic Intersections
R825427C005 Effectiveness of Rehabilitation Approaches for I/I Reduction
R825427C006 Urban Solid Waste Management Videos
R825427C007 UWMRC Community Outreach Multimedia Exhibit
R825427C008 Including New Technology into the Investigation of Inappropriate Pollutant Entries into Storm Drainage Systems - A User's Guide
R825427C009 Investigation of Hydraulic Characteristics and Alternative Model Development of Subsurface Flow Constructed Wetlands
R825427C010 Beneficial Use Of Urban Runoff For Wetland Enhancement
R825427C011 Urban Storm and Waste Water Outfall Modeling
R827933C001 Development of a Model Sediment Control Ordinance for Louisisana
R827933C002 Inappropriate Discharge to Stormwater Drainage (Demonstration Project)
R827933C003 Alternate Liner Evaluation Model
R827933C004 LA DNR - DEQ - Regional Waste Management
R827933C005 Landfill Design Specifications
R827933C006 Geosynthetic Clay Liners as Alternative Barrier Systems
R827933C007 Used Tire Monofill
R827933C008 A Comparison of Upflow Anaerobic Sludge Bed (USAB) and the Anaerobic Biofilm Fluidized Bed Reactor (ABFBR) for the Treatment of Municipal Wastewater
R827933C009 Integrated Environmental Management Plan for Shipbuilding Facilities
R827933C010 Nicaragua
R827933C011 Louisiana Environmental Education and Resource Program
R827933C012 Costa Rica - Costa Rican Initiative
R827933C013 Evaluation of Cr(VI) Exposure Assessment in the Shipbuilding Industry
R827933C014 LaTAP, Louisiana Technical Assistance Program: Pollution Prevention for Small Businesses
R827933C015 Louisiana Environmental Leadership Pollution Prevention Program
R827933C016 Inexpensive Non-Toxic Pigment Substitute for Chromium in Primer for Aluminum Sibstrate
R827933C017 China - Innovative Waste Composting Plan for the City of Benxi, People's Rupublic of China
R827933C018 Institutional Control in Brownfields Redevelopment: A Methodology for Community Participation and Sustainability
R827933C019 Physico-Chemical Assessment for Treatment of Storm Water From Impervious Urban Watersheds Typical of the Gulf Coast
R827933C020 Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region
R827933C021 Characterizing Moisture Content Within Landfills
R827933C022 Bioreactor Landfill Moisture Management
R827933C023 Urban Water Issues: A Video Series
R827933C024 Water Quality Modeling in Urban Storm Water Systems
R827933C025 The Development of a Web Based Instruction (WBI) Program for the UWMRC User's Guide (Investigation of Inappropriate Pollutant Entries Into Storm Drainage Systems)
R827933C027 Legal Issues of SSO's: Private Property Sources and Non-NPDES Entities
R827933C028 Brownfields Issues: A Video Series
R827933C029 Facultative Landfill Bioreactors (FLB): A Pilot-Scale Study of Waste Stabilization, Landfill Gas Emissions, Leachate Treatment, and Landfill Geotechnical Properties
R827933C030 Advances in Municipal Wastewater Treatment
R827933C031 Design Criteria for Sanitary Sewer System Rehabilitation
R827933C032 Deep Foundations in Brownfield Areas: Continuing Investigation
R827933C033 Gradation-Based Transport, Kinetics, Coagulation, and Flocculation of Urban Watershed Rainfall-Runoff Particulate Matter
R827933C034 Leaching and Stabilization of Solid-Phase Residuals Separated by Storm Water BMPs Capturing Urban Runoff Impacted by Transportation Activities and Infrastructure
R827933C035 Fate of Pathogens in Storm Water Runoff
R87933C020 Influence of Cyclic Interfacial Redox Conditions on the Structure and Integrity of Clay Liners for Landfills Subject to Variable High Groundwater Conditions in the Gulf Coast Region