Thesis (M.S.)--Oregon State University, 2001. / Typescript (photocopy). Includes bibliographical references (leaves 97-103). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves [135]-139). Also available on the Internet.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on November 20, 2009). Thesis advisor: Dr. Mitchell Schulte. Includes bibliographical references.

Rates of microbial reactions are important in understanding groundwater chemistry and bioremediation. In aquifers, microbial rates depend on physicochemical and biological factors and also on how groundwater transport impacts microbial reactions at pore-scale. I numerically simulate microbial acetate consumption in a porous medium, focusing on how physical heterogeneity of the medium impacts the rates. My model is a 3-D cube, which represents a portion of a sandy aquifer. Acetate is supplied by groundwater flow through the cube, and microbes live on randomly distributed grain surfaces by oxidizing acetate. I simulated microbial acetate oxidation under a range of groundwater velocity, acetate concentrations, spatial heterogeneity, and other physicochemical conditions. The results demonstrate a significant gap in microbial kinetics between the pore-scale and continuum model. Specifically, microbial rates are larger in porous media of greater heterogeneity. For this reason, I propose that microbial parameters should not be applied directly to field-scale biogeochemical modeling.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in hydrogeology, School of Geosciences. Johannesburg, 23 May 2016. / Groundwater treatment by chemical precipitation is a popular form of remediation at mines that are in operation. The water quality status at the implementation of the PAT in this study was compared to the water quality status after a six-month period of active remediation. Chromium is very important as an industrial metal owing to its numerous uses in a variety of industries. The objective of the remedial action is to intercept the Cr(VI) plume, abstract contaminated groundwater and chemically treat it on the surface. The long-term (15-year) objective is to eventually reduce Cr(VI) concentrations in the aquifer(s) to below 0.05 mg/ℓ. The PAT system was implemented as a mediumterm (5-year) strategy to intercept the Cr(VI) contamination plume during migration to prevent it from negatively impacting on groundwater users downstream of the mine. In the vicinity of the three PAT systems’ abstracting wells, water levels declined by an average of 2 m compared to the same period in 2014. Periodical fluctuations in the fractured aquifer are reflective of the influence of fractures on groundwater flow. In the aquifer, hydrochemical signatures show evidence of mixing between the primary and secondary aquifers. The treatment system has been successful in reducing Cr(VI) to Cr(III) and precipitating Cr(OH)3. The treatment system was designed to treat Cr(VI), other elevated constituents and generally high dissolved ions are not treated in this remedial process. Sulphate concentrations increase after treatment as a result of the addition of Fe(II)SO4 for chromate contamination treatment purposes. The simulated reaction path shows that the transformation of CrO4 2- to Cr2O3 in the treatment system is not immediate. The Cr(VI) to Cr(III) transformation is irreversible, this is beneficial as the water is abstracted from more reducing conditions, and the treatment ponds are open to the atmosphere thus the conditions following dosing with Fe(II)SO4 are oxic and chromate complexes are stable over a wider range of Eh-pH conditions than Cr(III) compounds. This ensures that the efficiency of the dosing system is not reversed in Settling Pond B. The modelled flow paths are similar to the inferred flow vectors in the plume capture zone. Fracture flow is the dominant type of flow, the fault zones and dykes create high permeability conduits to flow. Flow paths are parallel to fault lines or the lateral dimension of dykes; flow occurs along fractures and deformation zones. The reduction of Cr(VI) concentrations in some of the peripheral sampling points indicates that the PAT system has been successful in capturing the chromate contaminated water through pumping. Keywords: Hexavalent chromium, groundwater pollution, remediation, pump-and-treat, fractured aquifers / GR2016

No description available.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1983. / Includes bibliographical references (leaves 117-120).

Thesis (M.S. - Hydrology)--University of Arizona, 1984. / Includes bibliographical references (leaves 68-72).

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 185-191). Also available in electronic format on the Internet.

published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy