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The objective of this study is to provide an experimental performance assessment of cement borehole plugs subjected to dynamic loadings. This includes the study of dried-out plugs as well as of plugs that have remained wet throughout the testing period. Literature review indicates lack of quantitative data on plug performance under dynamic loading. Nevertheless, it shows that deep underground structures in competent rocks are safer than surface structures, openings at shallow depth, and openings in fractured rocks, when subjected to earthquakes and subsurface blasts. Flow test results indicate that wet cement seals are less permeable than Charcoal granite. Sealing performance is severely degraded when cement seals are allowed to dry. Dye injection tests show that the flow penetrates uniformly through the wet plugs, but occurs only along the plug/rock interface of the dried-out plugs. The permeability of wet and dried-out cement seals does not change significantly after the application of dynamic loads.

The objective of this study is to identify and examine potential mechanisms of radionuclide transport as vapor at a high-level radioactive waste repository located in unsaturated fractured rock. Transport mechanisms and processes have been investigated near the repository and at larger distances. Transport mechanisms potentially important at larger distances include ordinary diffusion, viscous flow and free convection. Ordinary diffusion includes self and binary diffusion, Knudsen flow and surface diffusion. Pressure flow and slip flow comprise viscous flow. Free convective flow results from a gas density contrast. Transport mechanisms or processes dominant near the repository include ordinary diffusion, viscous flow plus several mechanisms whose driving forces arise from the non-isothermal, radioactive nature of high-level waste. The additional mechanisms include forced diffusion, aerosol transport, thermal diffusion and thermophoresis. Near a repository vapor transport mechanisms and processes can provide a significant means of transport from a failed canister to the geologic medium from which other processes can transport radionuclides to the accessible environment. These issues are believed to be important factors that must be addressed in the assessment of specfic engineering designs and site selection of any proposed HLW repository.

Samples of ordinary copper, hot-isotactically-pressed (HIP) copper, and simulated borosilicate high-level waste glass were leached at 25°C, 51°C, and 80°C in solutions simulating brine and silicate groundwaters. It was found that the amount of glass leached increased at higher temperatures, and more leaching occurred in brine than in silicate groundwater. This behavior is predicted by Le Chatelier's Principle. Similarly, more copper was dissolved at higher temperatures, and more was dissolved in brine than in silicate groundwaters.

An analysis was performed of a Texas gulf coast hazardous waste injection well disposal system. The system was complicated by the presence of a fault which transected the injection interval. The existence of the fault presented the potential for enhanced vertical migration of the injected solutes via a tortuous path of interconnected, highly permeable sand units. Evaluation of this potential necessitated a fully three dimensional model which incorporated the arrangement of the alternating shales and sands and their associated discontinuities. Computer run time and memory limitations compelled a dissection of the problem into components, as well as the utilization of a specific mixture of conservative and realistic assumptions. The analysis indicated that within 10,000 years, the waste would advance vertically no further than one hundred feet into the overlying stratigraphy, and laterally no further than 24,000 feet from the point of injection.

Landfill leachate, the liquid discharge from Municipal Solid Waste (MSW) landfills, is the combination of the surface runoff and ground water that percolates through the waste and the liquid contained in the waste itself and is considered to be toxic and presents a potential harm to the environment. Raw leachate contains high concentrations of biodegradable and non-biodegradable carbon as well as high concentrations of ammonia nitrogen. Traditionally, landfill leachate has been treated biologically through aerobic processes which reduce the biological carbon to carbon dioxide and biomass (bacterial growth) and ammonia nitrogen to nitrates. Unfortunately this is not sufficient to protect the environment from harm. It is necessary to further treat the leachate anaerobically to transform the nitrates to elemental nitrogen which is removed from the leachate as nitrogen gas. Biodegradable carbon is often the rate limiting substrate as carbon is consumed during the preceding nitrifying phase. Biodegradable carbon can be supplemented through the addition of methanol, at great expense Leachate from the Mariannhill Landfill site is currently treated aerobically in a sequencing batch reactor where nitrification is achieved. The nitrified leachate is then used as a dust suppressant on the current site. It is anticipated that in 2012 the Land fill site would have reached capacity thereby eliminating the need to irrigate and leaving the site with an excess of nitrified leachate that will present an environmental risk. The denitrifying performance of raw commercial garden refuse, pine bark and composted garden refuse as a growth medium and carbon source was investigated through the establishment of batch and column tests. CGR Raw proved the most successful of the three growth media, achieving full denitrification at a loading rate of 1700 mg NO3-N/kg of substrate/day. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

Thesis (MTech. degree in Water Care ) - Tshwane University of Technology, 2007. / This research project investigated the total nitrogen removal capabilities of a nitrification and denitrification system treating two medium strength municipal landfill leachates. The characteristics of the leachates differed as one was obtained from general waste (GLB+) and the other from mixed industrial and general waste (H:h). This project was commissioned to develop a leachate treatment philosophy and a leachate management plan for the Vissershok landfill site near Cape Town. The aim of this leachate treatment trial project was to establish leachate treatability of different types of leachate, characterise leachate and effluent quality, determine alkalinity requirements, assess hydraulic retention periods and sludge production and confirm whether leachate quality can inhibit successful treatment in a sequencing batch reactor system. The two units were operated as simple Sequencing Batch Reactors (SBRs) by treating the leachate in a biological treatment process. Both units were initially seeded with activated sludge obtained from a sewage treatment works. Provision was made to supplement carbonaceous nutrient and phosphorus to the system. In the first stage of the study a controlled nitrification system was maintained to treat ammoniacal-nitrogen and the next stage denitrification was used to treat nitrate and nitrite-nitrogen levels. A completely automated daily cycle was used to treat the leachate and altered according to process requirements. The results showed that during nitrification ammoniacal-nitrogen concentrations as high as 2032.4 mg/l were consistently reduced to less than 0.1 mg/l. Similarly, for denitrification, nitrate-and nitrite-nitrogen concentrations were also consistently reduced to less than 0.1 mg/l, with a methanol utilisation ratio of CH3OH:N at 4.80:1. Chemical oxygen demand (COD) removal efficiencies were in the range 57-65% depending on loading rates applied. In conclusion it was shown that: (a) the biodegradable organics (COD) was reduced considerably (b) complete nitrification and denitrification occurred (c) no constituents of the leachate caused inhibition of the biological process.

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