Landfill emissions are the major environmental impact associated with the landfilling of / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007

The specific objective of this study was to evaluate a PCI reverse osmosis membrane for / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006

Digitized by Kansas Correctional Industries

Spatial and temporal variation in inorganic contaminant concentration and distribution in a landfill leachate plume is examined to determine the mechanisms responsible for the observed variation, and to provide an assessment of the implications of this variation with respect to the interpretation of monitoring data, specifically with regards to its application to geochemical modelling. An integrated approach to field investigation was utilised in this study, including sample collection from a network of standard and bundled piezometers, surface and borehole geophysical investigation techniques, and a manometer board for the measurement of hydraulic head in bundled piezometers. Nine groundwater sampling events were conducted over a 12 month period, with sample analyses comprising field measurement of water quality parameters and redox sensitive elements, and laboratory analysis for major and trace elements and stable isotopes (??18O, ??2H, ??13C-DIC, ??15N). The vertical position of the centre of mass of the leachate plume was observed to vary up to 2 metres between monitoring events, and concentrations of key indicator parameters were observed to fluctuate by as much as 160%. The electrical images created by surface resistivity transects along a groundwater flow path between the landfill and a groundwater-fed pond a short distance downgradient suggest a plume configuration characterised by discrete pulses of concentrated leachate migrating in a conservative manner between the landfill and the pond. It is hypothesized that these leachate slugs are flushed into the aquifer during sustained periods of rainfall, presumed to be a significant driver of leachate mobilisation into the underlying aquifer. The most significant hydrogeochemical processes affecting contaminant mobilisation, transport and attenuation in the leachate-impacted shallow aquifer included microbial degradation of organic waste, dissolution of inorganic waste, ion exchange, precipitation of sulfide and carbonate minerals, mixing with rainfall recharge along flow path, and redox transformations along the plume fringe. These processes are supported by hydrogeochemical data analysis, and generally agree with the results of inverse geochemical modelling. While analysis of detailed groundwater monitoring appears to provide a plausible description of the plume dynamics, the results of the electrical resistivity transects indicates a more varied and complex plume configuration than is suggested by the borehole data alone. This integration of investigation techniques underscores the inherent inadequacy of even a high-resolution monitoring well network to accurately describe the full extent of variation in time and space within a contaminant plume, even in a relatively simple aquifer environment, and accentuates the potentially significant limitations of site-scale hydrogeochemical interpretation based solely on borehole monitoring data.

Thesis (M.Sc.)--University of Hong Kong, 1998. / Includes bibliographical references (leaf 71-73) Also available in print.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Tarek Abichou, Florida State University, College of Engineering, Dept. of Civil and Environmental Engineering. Title and description from dissertation home page (viewed June 21, 2004). Includes bibliographical references.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 201-209.

Using Environmental Protection Agency occurrence and concentration data, it is estimated that about 6 million pounds of arsenic-bearing residuals (ABSR) will be generated annually in the United States when full compliance with the new standard for arsenic in drinking water (10 μg/L) is realized. Effective management of disposal of ABSR requires both a full characterization of the materials and an understanding of the environment in which the disposal will occur. Currently, there are different testing methods to evaluate the stability of ABSR, the principal of which is the EPA Toxicity Characteristics Leaching Procedure (TCLP). These tests indicate that common ABSRs may be disposed in mixed-solid waste landfills. However, this and previous work shows that these testing methods may significantly underestimate the degree and mechanism of arsenic mobilization from the residuals, because critical physical and chemical dissimilarities exist between the tests and landfill conditions. In addition, no current testing methods simulate the mineralogic aging in those ABSR, which exhibit further complexity. Landfill disposal involves liquid and solid residence times on the order of months and decades, respectively, whereas leaching tests are completed in two days or less. Consequently, time dependent re-mineralization of residuals that would be routinely expected in landfill time scales is not addressed by standard leaching tests. Treating arsenic brines by co-precipitation with iron oxyhydroxides is an established and effective remediation method for small quantities of highly concentrated liquid arsenic waste, such as brines derived from mine tailings, ion exchange resin regeneration, and reverse osmosis treatment of drinking water. However, amorphous ferric hydroxide (AFH) is expected to exhibit mineralogical aging analogous to the observed natural evolution of ferrihydrite to goethite and hematite. The aim of this research is to develop methods for characterization of AFH sludges precipitated from concentrated arsenic brines which exhibit mineralogical aging and to evaluate the impact of such aging on arsenic leachability. Overall, aging the sludge resulted in consistently higher arsenic release.

The problem of domestic solid wastes buried in landfill sites is viewed from the aspect of leachate contamination and migration in the substrate. Generally, this occurs through the penetration of the contaminant into the liner material. This study assesses the efficiency of natural clay barriers as an expedient economic lining material. / Various chemical constituents of the landfill leachate of an actual waste containment site at Lachenaie (35 km east of Montreal) were determined from samples collected from specially designed basins. / In companion laboratory tests, these leachate samples were permeated through laboratory columns that contained the natural clay compacted at the optimum water content. The columns were constructed so as to permit simulation of slow, saturated, anaerobic flow of leachate through the clay lining surrounding the landfill and leachate basins. Leachates were permeated through the soil columns for periods of four to five months, during which effluents were collected periodically and analyzed for different chemical species and physical parameters. These chemical analyses measured changes in the concentration of: (a) cations (Na, K, Ca, and Mg), (b) anions (Cl, HCO$ sb3$, and CO$ sb3$), (c) total organic carbon (TOC), and (d) heavy metals (Fe, Zn, Pb, and Cu). The physical parameters measured included: (a) pH, and (b) specific conductivity. / Subsequent to the leaching tests, the column contents were cut into six sections and analyzed to determine the distribution profiles of the adsorbed and retained contaminants at various time durations. / Predictions, using a dispersion-convection model for concentration profile development for either adsorbed or retained contaminants, were compared with the experimentally determined profiles (both in leaching columns and landfill laboratory model). / Another set of experiments was also conducted to evaluate the effect of some organic fluids on the geotechnical properties of different clay soils (natural clay and two reference clay soils: illite and kaolinite). / The results from this study have demonstrated that the natural clay soil can be used to adequately contain the different contaminant species usually present in the leachate solutions. Furthermore, the data suggested that under favourable soil conditions, landfill leachates containing low levels of trace metals will not pose a substantial contamination threat to the subsurface environment, provided that a proper thickness of barrier is used. (Abstract shortened with permission of author.)

No description available.