This thesis presents the development of a numerical model for one-dimensional pollutant transport in a porous medium. A computer program POLUTE1D has been developed. The numerical model is based on the flow and mass transport equations and the finite element method has been used for its formulation. The problem involves unsaturated flow and convective dispersive transport of a contaminant species. A literature survey on the evaluation of the dispersion coefficient is included. A waste disposal dump site is analysed as a one-dimensional problem by using this model. The effect of the liner thickness, the liner permeability, the ponding head and the initial condition of the porous domain on the spread of the contaminant is studied. Conclusions are presented based on a parametric study. / M. Eng.

This study includes a systematic investigation of the bond strength of cementitious borehole plugs in welded tuff. Analytical and numerical analysis of borehole plug-rock stress transfer mechanics is performed. The interface strength and deformation are studied as a function of Young's modulus ratio of plug and rock, plug length and rock cylinder outside-to-inside radius ratio. The tensile stresses in and near an axially loaded plug are analyzed. The frictional interface strength of an axially loaded borehole plug, the effect of axial stress and lateral external stress, and thermal effects are also analyzed. Implications for plug design are discussed. Push-out tests are used to determine the bond strength by applying an axial load to the cement plugs. A total of 130 push-out tests are performed as a function of borehole size, plug length, temperature, and degree of saturation of the tuff cylinder. The use of four different borehole radii enables evaluation of size effects. A well-defined exponential strength decrease with increasing plug diameter results.

The process of fluid injection into granular media is relevant to a wide number of applications such as enhanced oil recovery, grouting, and the construction of permeable reactive barriers. The response of the subsurface is dependent on multiple factors such as in-situ stresses, fluid properties, flow rate, and formation type. Based on these conditions a variety of response mechanisms can be initiated ranging from simple porous infiltration to hydraulic fracturing. Currently, the mechanics of fluid injection into competent rock are well understood and can be sufficiently modeled using linear elastic fracture mechanics. Because the grains in rock formations are individually cemented together, they exhibit cohesion and are able to support tensile stresses. The linear elastic method assumes tensile failure due to stress concentrations at the fracture tip. A fracture propagates when the stress intensity factor exceeds the material toughness (Detournay, 1988) However, understanding fluid injection in cohesionless granular media presents a much larger obstacle. Currently, no theoretical models have been developed to deal with granular media displacements due to fluid injection. Difficulty arises from the complexity of fluid rheology and composition used in engineering processes, the strong coupling between fluid flow and mechanical deformation, the non-linear response of subsurface media, and the multi-scale nature of the problem. The structure of this thesis is intended to first give the reader a basic background of some of the fundamental concepts for non-Newtonian fluid flow in granular media. Fluid properties as well as some interaction mechanisms are described in relation to the injection process. Next, the results from an experimental series of injection tests are presented with a discussion of the failure/flow processes taking place. We developed a novel technique which allows us to visualize the injection process by use of a transparent Hele-Shaw cell. Specifically, we will be using polyacrylamide solutions at a variety of concentrations to study non-Newtonian effects on the response within the Hele-Shaw cell. By performing tests at a range of solution concentrations and injection rates we are to be able to identify a transition from an infiltration dominated flow regime to a fracturing dominated regime.

Thesis (M.S.)--Mississippi State University. Department of Chemical Engineering. / Title from title screen. Includes bibliographical references.

A high level of plant mortality on the Bisasar Road landfill, Durban, South Africa initiated an investigation into the primary causes of the mortalities and a search for potentially tolerant plant species. Field studies revealed that volunteer grass growth on cover soils was primarily limited by elevated soil C02, with high soil conductivity and low soil moisture possibly compounding the effect. Cynodon dactylon, the most abundant coloniser of the site appeared to be relatively sensitive to high soil CO2, whilst less common species such as Sporobolis cifricanus and Paspalum Paspoloides appeared to be less sensitive. Further research focused on the high mortality of trees planted on the landfill providing insight into the important variables limiting survival· and the relative differences in performance of 20 tree species. A more rigorous 14-month field experiment was designed and constructed, to assess the performance of 10 of the more promising tree species, the environmental conditions limiting tree growth and the benefit of a deeper layer of better quality topsoil. Some species, such as Barringtonia racemosa, performed relatively well in the field experiment, whilst other species such as Syzygium cordatum, and Harpephyllum caffrom experienced high mortalities and poor growth. The better quality topsoil layer provided little improvement in the performance of the stronger or the weaker species, however significant improvements were recorded for species with relatively intermediate performance. The composition of the soil atmosphere was shown to determine rooting depth. Species that performed better had deeper roots, possibly assisting them in utilising deeper soil moisture reserves. It was concluded that high soil CO2 and low soil O2 levels were the key variables responsible for poor tree survival and growth in this field experiment. A soil fumigation system was designed to provide more control of soil gas concentrations and to experimentally investigate differential species responses and the relative effects of soil CO2 and O2 on tree survival and growth. The apparatus fumigated, for a period of 140 days, the rhizosphere of 80 potted 'tolerant' (Barringtonia racemosa) and 'non tolerant' (Harpephyllum caffrum) trees with 4 treatments consisting of varying combinations of CO2 and 02. The difference in performance of Barringtonia racemosa and Harpephyllum caffrum in the experiment on the landfill was similar to that of the elevated CO2 low O2 fumigation treatment, supporting the premise that landfill gas was the key cause for poor performance of plants. Reduced stomatal conductance and resultant limitations on photosynthesis were found to be indicative of species sensitivity. Low O2 had an additive effect on the impact of elevated CO2 in Harpephyllum caffrum however, even with normal soil O2 levels, 25% soil CO2 had negative growth effects on this sensitive species. Maintenance of plant health and better performance of Barringtonia was attributed to a high inherent level of tissue porosity and aerenchyma. The research provided a greater understanding of the causes of poor vegetation growth and the possible mechanisms of species tolerance to landfill conditions. / Thesis (Ph.D.)-University of Natal, Durban, 2003.

Co-disposal with refuse in a controlled landfill is the cheapest option for the disposal of hazardous waste and, if carefully controlled, can be an effective treatment option. In this present study a high-strength phenolic wastewater and activated sewage sludge were co-disposed with refuse. The effectiveness of phenol catabolism at two organic loading rates (500mgt1 and 1000mgtl) was assessed in the presence of various co-disposal strategies. Leachate recycle at the lower phenol organic loading rate was found to facilitate the greatest rate of phenol catabolism. Despite the effective removal of phenol, however, leachate recycle promoted the production of high concentrations of ammoniacal-N and hydrogen sulphide. At the higher phenol organic loading rate, recirculation was ineffective in reducing the residual phenol concentration due to inhibition of the phenol-catabolisers. Microcosms operated with single elution and batch co-disposal strategies at both phenol organic loading rates resulted in serious detrimental effects on the refuse fermentation and subsequent leachate quality. A high-strength leachate obtained from a closed co-disposal site was characterised to determine its chemical composition and was assessed for its susceptibility to biological treatment. If carefully controlled, co-disposal sites should produce leachates which differ little in quality to those produced by municipal waste sites. The exceptionally high specific conductivity of the leachate used in this present study was, however, uncharacteristic of a leachate from a municipal waste site. The leachate required dilution to 25 % (v/v) before responding to aerobic biological treatment due to the presence of bactericidal/bacteriostatic components. Anaerobic treatment was ineffective even at a final dilution of 10% (v/v) of the original due to the inhibition of methanogenesis caused indirectly by the high concentration of sulphate in the leachate. Following phosphate addition, aerobic biological treatment effected a significant reduction in the chemical oxygen demand (COD) but did not reduce the ammoniacal-N concentration. Scaling and precipitation occurred following addition of the phosphate, and although these did not affect the biological process they can cause operational problems in full-scale leachate treatment plants. Ion exchange, with soil, and lime treatment, were, therefore, considered for their ability to reduce the inorganic content of the leachate prior to biological treatment. However, these particular pretreatments were unsuitable due to their ineffectiveness to reduce calcium, the main inorganic element involved in scaling, to an acceptable concentration. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

Reported research has suggested that poor persons and/or minorities are disproportionately exposed to environmental hazards such as incinerators, landfills, pesticides, and poor air quality. One accepted form of an environmental hazard is a waste management facility. This present research examined the variables minority percentage and median household income of the population surrounding each waste management facility under scrutiny within Lake County, Indiana. The two variables were each correlated with distance from the center of each waste management facility (as determined through a geographic information system) to a distance of three kilometers. The materials and methods used in this particular research provided for a more precise analysis of such correlations than has typified most of the earlier studies. Three significant correlations were found. First, the Gary landfill rendered a positive relationship between distance from the center of the site and increased income. Second, the Munster landfill revealed a negative relationship between distance to the center of the site and increased minority percentage of the population. Lastly, the Munster landfill also had a negative relationship between income and distance from the center of the landfill. Data showed that the large proportion of minority households surrounding the Munster landfill earned an income that would easily allow for social mobility. Such social mobility, arguably, allows a household to move away from an environmental hazard. It was concluded that no support for a claim of environmental racism could be found. Further, a call for a re-examination of the definition of environmental racism is made based upon the large number of wealthy minorities residing around the Munster landfill. / Department of Natural Resources and Environmental Management

Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2008. / Full text also available online. Scroll down for electronic link.

A laboratory study was conducted to determine nitrogen removal rates from a land-applied wastewater as a function of the length of time the wastewater remained in the root zone. A digital simulation model was used as an aid in describing soil water (and wastewater) movement through the root zone under wet conditions (i.e. root zone 50- 75% saturated). A procedure was developed to predict the rate and volume of drainage as a function of initial soil moisture content, amount of liquid applied, and time after liquid application. An exact relationship between nitrogen removals and wastewater residence time in the root zone could not be developed. However, removals of up to 95% of applied NH₄-N were demonstrated in an 18-cm deep root zone with residence times as short as 2 hours. The exact nature of these removals was not determined. / Ph. D.

Thesis. 1975. M.C.P.--Massachusetts Institute of Technology. Dept. of Urban Studies and Planning. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Bibliography : leaves 118-121. / M.C.P.