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Cooling tower plume rise, dilution and dispersion is investigated using a numerical model. Both single and double sources are considered. The main aim of the investigation is concerned with comparison of the computational results to existing wind tunnel experimental data as well as simple empirical rise height formula. Analysis of the interaction of adjacent sources, and subsequent rise augmentation compared to that of a single source, is a central theme of the work. A full-scale hybrid mechanical cooling tower is modelled as a surface mounted cuboid block 20 m high with an internal development duct of 10 m diameter. Both jet and moderately buoyant plume type sources are studied. Two exit velocity ratios are also considered. An oncoming atmospheric boundary is modelled with an associated logarithmic velocity profile and profiles of turbulence kinetic energy and length scale. Two double source orientations, tandem and side-by-side with respect to the oncoming cross wind, are studied. Physical symmetry is utilised and so only half of the domain is modelled. Both the small-scale (wind tunnel) and full-scale were modelled. The small-scale work used combinations of a low Reynolds number k-e turbulence model and both hybrid and QUICK discretisation schemes. The high Reynolds numbers encountered in the fullscale allowed the use of a number of different turbulence models, namely the standard k-e model, the RNG k-e model and a differential flux model, combined again with the hybrid and QUICK discretisation schemes. The results of a number of sensitivity tests showed that plume rise in this case was not sensitive to the turbulence model constant C3 or to source turbulence levels. A decrease in the turbulent Prandtl number led to a marked increase in the turbulent diffusion of the thermal plume. Horizontal plume spreading was underpredicted in both small and full-scales compared to the experimental data. Plume rise and dilution was, in the majority of cases, predicted accurately compared to both the experimental data and also to rise heights given by simple empirical relationships. Generally, the choice of discretisation scheme was a more important factor than choice of turbulence model. Interaction of side-by-side plumes was dominated by the interaction of the rotating vortex pairs within the plumes. A tandem source arrangement led to early merging and efficient rise enhancement. Merging into a single type plume occurred sooner with an decrease in exit velocity ratio, R.

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.

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.

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.

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.

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 (Ph.D. ) - James Cook University, 2005. / Typescript (photocopy) Bibliography: leaves 188-206.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 204-228).