Robert M. Quigley

Barrier Systems for Waste Disposal Facilities

1. Basic Concepts. 2. Leachate Characteristics and Collection. 3. Clay Liners: Compaction, Hydraulic Conductivity and Clay Mineralogy. 4. Clay/Leachate Compatibility by Measurement of Hydraulic Conductivity. 5. Flow Modelling. 6. Chemical Transfer by Diffusion. 7. Contaminant Transport Modelling. 8. Evaluation of Diffusion and Distribution Coefficients. 9. Field Studies of Diffusion and Hydraulic Conductivity. 10. Contaminant Migration in Intact Porous Media: Analysis and Design Considerations. 11. Migration in Fractured Media: Analysis and Design Considerations. 12. Geosynthetic Clay Liners (GCLs). 13. Geomembrane Liners. 14. Covers. 15. Geotechnical and Related Design Issues. 16. Integration of Hydrogeology and Engineering in Barrier Design and Impact Assessment. Index.

Clayey Barrier Systems for Waste Disposal Facilities

Basic concepts. Introduction. Overview of barrier systems. Transport mechanisms and governing equations. Complicating factors. Modeling the finite mass of contaminant. Modeling a thin permeable layer as a boundary condition. Hand solutions so some simple problems. Summary. Design considerations. Introduction. Impact assessment. Waste and leachate composition. Leachate mounding and collection. Leakage through liners. Leak detection systems. Landfill capping and the control of infiltration. Choic of barrier system and service life considerations. Geotechnical considerations. Summary. Clayey barriers: compaction, hydraulic conductivity and clay mineralogy. Introduction. Methods of assessing hydraulic conductivity. Compaction-permeability relationships. Clay mineralogy. Clay colloid chemistry. Clay-leachate compatibility by measurement of hydraulic conductivity. Introduction. Soil- MSW leachate compatibility. Compatibility of clays with liquid hydrocarbon permeants. Summary and conclusions. Flow modeling. Introduction. One-dimensional flow models. Analysis of two-and three-dimensional flow. Finite difference approximation. Application of the finite element method to the analysis of plane flow. Boundary element methods. Chemical transfer by diffusion. Introduction. Free solution diffusion (Do). Diffusion through soil. Steady-state diffusion. Transient diffusion. Use of laboratory and field profiles to measure diffusion coefficient De. Diffusion during hydraulic conductivity testing for clay - leachate compatibility. Summary and conclusions. Contaminant transport modeling.Introduction. Analytical solutions. Application of Laplace transforms to develop a finite layer solution for a single layer. Contaminant transport into a single layer considering a landfill of finite mass and an underlying aquifer. Finite layer analysis. Contaminant migration in a regularly fractured medium. Determination of diffusion and distribution coefficients. Introduction. Obtaining diffusion and partitioning/distribution coefficients: basic concepts. Example tests for obtaining diffusion and distribution coefficients for inorganic contaminants. Dispersion at low velocities in clayey soils. Effective porosity. Distribution coefficients and nonlinearity. Effect of leachate composition, interaction and temperature. Diffusion and sorption of organic contaminants. Use of field profiles to estimate diffusion coefficients. Summary and conclusions. Field studies of diffusion and hydraulic conductivity. Introduction. Examples of long-term field diffusion. Examples of short-term diffusion. Hydraulic conductivity of contaminated clay liners. Contaminant migration in intact porous media: analysis and design considerations. Introduction. Mass of contaminant, the ref erence height of leachate, Hr, and the equivalent height of leachate, Hf. Development of a contaminant plume. Effect of base velocity. Effect of horizonta

A laboratory estimation of diffusion and adsorption coefficients for several volatile organics in a natural clayey soil

Abstract A laboratory diffusion-test estimation of the diffusion coefficient ( D ) and the adsorption coefficient ( K d ) for several volatile organic species in a saturated, relatively undisturbed, clayey soil is presented. The species considered were acetone, 1,4- dioxane , aniline, chloroform and toluene, at maximum concentrations ranging from 200 to 300 mg L−1. In addition to the diffusion tests, batch tests were performed for aniline, chloroform and toluene, and the resulting K d - values were compared with those estimated from the diffusion tests. For the more soluble species (acetone, 1,4- dioxane and aniline) D- and K d - values were readily inferred from the diffusion-test results and are considered to accurately represent diffusion through the soil and adsorption onto the soil solids under the conditions imposed. For the hydrophobic species (chloroform and toluene), the inferred D- and K d - values from the diffusion test are significantly influenced by adsorption of the species onto the diffusion cell material, resulting in unreasonably high D- and K d - values . However, it is shown that by combining the results of both batch tests and diffusion tests, an upper and lower bound estimate of D and K d may be obtained.

Heavy metal migration at a landfill site, Sarnia, Ontario, Canada—2: metal partitioning and geotechnical implications

Abstract Heavy metal profiles below a 15-year old sanitary landfill overlying a 30 m thick natural clay deposit are presented. Results indicate that unlike soluble species such as Cl − and Na + which have migrated distances up to 130 cm, Cu, Zn and Pb have migrated only up to 10 cm. The extent of Fe migration is estimated to be 20 cm. Highly reducing conditions at the interface ( E h = −130mV), coupled with the alkaline nature of the clay pore waters, have resulted in the precipitation of migrated heavy metals as carbonates. At the clay/waste interface, 88, 84 and 80% of the excess Fe, Zn and Pb, respectively, are present as secondary carbonates. This is confirmed by selective chemical dissolution analyses which also show that Fe, Zn, Pb and, to a greater extent, Cu are present in solid organic forms at the interface. Batch equilibrium studies clearly show that Cu and Pb removal from leachate is significantly increased by the presence of carbonates in the soil. For example, 75% more Pb is removed by the carbonate-rich bulk soil than the carbonate-free soil. The batch studies also show that when the pH > 5.2, removal of metal increases significantly due to precipitation as carbonates. From the results it is concluded that the presence of metal sludges in landfills lined naturally or artifically by a carbonate-rich clayey barrier reduces the rate of migration of numerous toxic transition metals and may also decrease the barrier porosity by precipitation. The decreases in porosity will be beneficial to the performance of the barrier due to reductions in both advection and diffusion.

Comparison of Laboratory-Measured GCL Hydraulic Conductivity Based on Three Permeameter Types

Specimen preparation, installation, and testing procedures are presented for testing a needle-punched geosynthetic clay liner (GCL) in a consolidation-type, fixed-ring constant-flow-rate hydraulic conductivity apparatus. The proposed approach is illustrated by reporting the results obtained for a GCL statically confined to effective stresses of ∼3 and ∼35 kPa, hydrated and permeated with distilled water and concentrated aqueous salt solutions (0.6 and 2.0 N NaCl), and sequentially permeated with concentrated aqueous salt solutions (0.6 and 2.0 N NaCl) after initial permeation with distilled water. The issue of potential preferential sidewall flow in the fixed-ring permeameter tests was then addressed by comparing results with those conducted under otherwise similar testing conditions in a double-ring and flexible-wall permeameter. Reasonable reproducibility of the test results was obtained between the different types of permeameters, suggesting that, if present, preferential sidewall flow was negligibly small and was not significant on the calculated hydraulic conductivity values. This conclusion was found to be valid for the range of permeant types (distilled water and 0.6 and 2.0 N NaCl), static-confining stresses, and hydrating mediums considered. Premature arrival of the salt solution front in the effluent (i.e., solute breakthrough) during fixed-ring hydraulic conductivity testing was explained as a probable diffusion-dominated transport mechanism through the relatively thin GCL specimens.

Heavy metal migration at a landfill site, Sarnia, Ontario, Canada—I. Thermodynamic assessment and chemical interpretations

Abstract The transition metals Fe, Cu, Zn and Pb have diffused only 10–20 cm into the clay barrier at the Confederation Road landfill compared to 130 cm for porewater chloride. Other major dissolved species, including the alkali and alkaline earth metals, have also diffused out of waste landfill and into clay subsoils more rapidly than the metals. Redox potentials, E h , indicate strongly reducing conditions (E h = − 130 mV) in the clayey soil at the subsoil/waste interface and increase to +50 mV at a depth of 45 cm below the interface. pH values are close to 8 within the subsoil but the slightly lower values (7.8–8) near the interface may result from production of organic acids during degradation of the wastes. Thermodynamic analysis of subsoil pore waters indicates that Fe, Cu, Zn and Pb exist primarily as metal-hydroxy complexes of the forms [MeOH] + and [Me(OH) 2 ] 0 , although a complex of [PbCl] + may be significant, but not predominant. The analysis also demonstrates that the dissolved transition metal concentrations of the subsoil pore waters are controlled at carbonate mineral saturation levels, whereas Fe concentrations in leachate solutions associated with the wastes are controlled at FeS 2 saturation levels. Thermodynamic calculations and E h -pH diagrams suggest that Fe(OH) 2 , Zn(OH) 2 and Pb(OH) 2 are not stable phases in the solids of the subsoil. This means that observed “hydroxide” phases reported in the selective dissolution analysis by Yanful and Quigley (1986) have to be re-evaluated.

Coal-Clay Triboelectrification

Experimental results are presented for the triboelectrification of coal-clay specimens in air at 20°C and 20.7 kPa. The coal was a vitrinite from Hat Creek, BC, and the clays were relatively pure kaolinite and montmorillonite. The cumulative charge after 100 contacts was much greater for kaolinite than montmorillonite in contact with the coal; however, the curves intersect each other after 10-30 contacts. Further work is under way to try to explain the unusual buildup in charge by an analysis of the volumetric charges and conductivity of the dry clays. The triboelectrification of coal-clay mixtures will play a major role in any contemplated electrostatic beneficiation of much of the coal which will be mined in Western Canada.

Electrostatic Charges on Clays

Cation charges present on the surfaces of clay minerals are expected to play a major role in industrial processes involving dry electrostatic separation of granular mixtures containing clay particles. A recent promising potential application has been the removal of clay from British Columbia pulverized coals prior to burning. The clay minerals kaolinite and montmorillonite form the main component of the ash in most Canadian coals: kaolinite is eastern coals and montmorillonite in western coals. The electric charges present on the surfaces of the clay mineral kaolinite have been analyzed from an application point of view, namely, for their ability to transfer onto and remain on other surfaces after contact and separation. Kaolinite samples homoionized with calcium and sodium were prepared from natural kaolin, and the charge transfer after contact and separation with coal was compared for various dry densities of the kaolinite. The results show the following. 1) The electric charge transfer from calcium kaolinite is substantially larger than that from both the sodium kaolinite and natural kaolinite. Charge transfer from untreated montmorillonite exceeds that from all kaolinite samples. 2) The charge transfer after 100 contacts is inversely proportional to the dry density of the clay on a semilog scale. The phenomenon is believed to be related to the changes which occur in the total contact area and in the electrical conductivity of the clay.

Hydrocarbon Liquids and Clay Microstructure

Extensive studies of the interactions between organic liquids and clay minerals have been carried out over the past 10 years. The work has dealt primarily with hydraulic conductivity, k, and the influence that organic liquids of low dielectric constant have on measured values of k (Michaels and Lin, 1954; Lambe, 1956; Mesri and Olson, 1971; Brown et al., 1984; Acar et al., 1985; Fernandez and Quigley, 1985, 1988; Foreman and Daniel, 1986; Quigley and Fernandez, 1989). In most cases, the above articles have dealt with double layer theory and resultant physicochemical effects, with little attention given to the role of soil fabric and microstructure.

Electrostatic beneficiation of gold ores

The authors present encouraging results obtained in separation of the Doyon gold ores when using the electrostatic inverted roof apparatus described by I.I. Inculer et al. (ibid., vol.IA-9, no.3, p.318-23, 1983). The electrification phenomena through combined tribo-electric and inductive charging were studied at various relative humidities. Contrary to expectations, the experimental work showed that the best separations are achieved at relatively high humidities of approximately 70% or higher. One of the main cost factors in electrostatic beneficiation of minerals is that of drying the material. The lesser drying required of this gold ore may be of considerable economic importance. >