No description available.

Thesis (Ph.D)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2010. / Committee Chair: Taillefert, Martial; Committee Member: DiChristina, Thomas; Committee Member: Sobecky, Patricia; Committee Member: Van Cappellen, Philippe; Committee Member: Webb, Samuel. Part of the SMARTech Electronic Thesis and Dissertation Collection.

No description available.

Graduation date: 1994

Thesis (Ph.D.)--Memorial University of Newfoundland, 1999. / Bibliography: leaves 277-286.

In situ chemical oxidation is a promising technology for the remediation of persistent subsurface contamination. Increasingly, the persulfate ion is being studied for use in these systems, both on its own as a strong oxidant and as the precursor to the even more reactive sulfate radical. Persulfate has been shown to treat a wide range of contaminants, from traditional Superfund contaminants such as chlorinated solvents to emerging pharmaceutical contaminants. Additionally, persulfate ISCO can be tailored to site and pollutant specific characteristics based on the method of persulfate activation (e.g., energy and catalysis activation) to the sulfate radical. Thermal activation of persulfate is particularly promising because it can be easily controlled, requires no additional reagents, and commonly creates only non-toxic end products. While persulfate in-situ chemical oxidation technology is being commercially used, a mechanistic study of the physical and chemical processes controlling the effectiveness of this remedial approach is not well documented in the literature. Published work characterizing persulfate ISCO largely focuses on reactions in aqueous, batch systems, which fail to provide crucial design data when working with ever transient, multi-phase groundwater systems. The purpose of this research was twofold. Initial studies characterized the overall transport behavior of unactivated and thermally-activated persulfate (20, 60, and 90°C) in one-dimensional soil column systems packed with a natural sandy porous media. This necessitated the development of a flow-through, temperature-controlled, continuous-injection system for the delivery of heat-activated persulfate. Finally, as a proof of concept, experiments were conducted to investigate persulfate ISCO as a remedial approach for residual-phase trichloroethylene (TCE), a commonly detected, persistent subsurface contaminant. At all activation temperatures investigated, persulfate exhibited ideal transport behavior with negligible differences in the observed breakthrough curves of persulfate ion and nonreactive tracers in miscible displacement experiments. Additionally, moment analysis of the breakthrough curves measured for persulfate ion in solution indicated negligible interaction of persulfate with the sandy material under steady-state flow (average retardation factor equaled 1.00 ± 0.021). Persulfate ISCO for residual-phase trichloroethylene (TCE) was characterized at two flow rates, 0.2 mL/min and 0.5 mL/min, resulting in two degrees of apparent persulfate activation, 39.5% and 24.6%, respectively. Both ISCO soil column systems showed an initial, long-term plateau in effluent concentrations measured for TCE indicating steady-state dissolution of pure phase TCE. Effluent concentrations of TCE began decreasing after 75 and 100 pore volumes (normalized for the residual fraction of TCE in individual soil columns) in the 39.5% and 24.6% activated persulfate columns as compared to 110 pore volumes in the control study (flushed with electrolyte only). Pseudo first-order rate constants for the decreasing TCE concentrations were calculated using log-linear regression analysis. The measured reaction rate constants for the control, the 0.2 mL/min (39.5% activation) study, and the 0.5 mL/min (24.6% activation) study equaled 0.044, 0.063, and 0.083 hr-1, respectively. Additionally, moment analysis of the complete dissolution of TCE in the persulfate/activated persulfate remediation systems indicated approximately 33% degradation/oxidation of TCE mass present. As shown by this and other work, persulfate has enormous potential as a subsurface remediation technology. A more thorough understanding of the physical and chemical mechanisms controlling the behavior and application of persulfate in the subsurface, especially under transient conditions, is necessary for the growth of this technology. By characterizing heat-activated persulfate under dynamic conditions, describing the overall transport of persulfate/activated persulfate in a natural porous media, as well as a proof of concept for the ISCO treatment of a residual nonaqueous phase liquid, this work aids in improving the implementation of persulfate ISCO systems.

No description available.

No description available.

Aging and leaking water infrastructure wastes water resources and creates public health risks. Upgrading of potable water systems represents a large financial burden for water utilities and private property owners. The conventional approaches of repair, rehabilitation and replacement are very effective, but will take decades to implement even if a financial commitment to do so was made immediately. A novel approach of in-situ remediation of leaks, achieved by harnessing the ability of water or pipe to repair leaks via clogging, could potentially reduce leak rates and extend the lifetime of existing infrastructure at relatively low cost and inconvenience. Physical clogging, precipitation and metallic corrosion were identified as major mechanisms of in-situ leak remediation in potable water pipelines. Autogenous repair (i.e., self-repair without added particles) of small leak-holes (150–"1000 μm) in copper and iron was validated in the laboratory at water pHs of 3.0–11.0, operating water pressures of 20–60 psi, upward and downward leak orientations, and for a range of water chemistries. In bench scale experiments, the time to repair of iron pipe leaks increased with leak size to the power of 0.89–1.89, and decreased with pipe wall thickness to the power of -1.9 to -1.0. The time to repair of copper pipe leaks increased with water pressure to the power of 1.7. Additionally, the waters with a higher DO and corrosivity as measured by RSI, significantly decreased the time to repair of carbon steel 400 μm leaks by 50–70%. The presence of chlorine dioxide significantly increased the fraction of repaired 200 μm copper pipe leaks by 3 times when compared to the control without any disinfectant. In the building scale study, the fraction of repaired iron pipe leaks decreased with the logarithmic leak size with a slope of -0.65 after one-year duration of experiments, while leak orientation and water pressure were not influential in time to or likelihood of repair for iron pipe leaks. Addition of calcium carbonate particles (~8.8 μ]m), silica particles (~29 μm) and wood ash particles (~160 μm) in Blacksburg, VA tap water at a water pressure of 10 psi increased the fraction of remediated iron pipe leaks of 280–1000 μm diameter sizes. Although the control condition with no added particles for 58 days resulted in remediation of 0/12 leaks, remediation rate increased to 1/12 with calcium carbonate particles, to 10/12 with silica particles and to 10/12 with wood ash particles. Leak size and particle size played an important role in controlling the remediation success rate. The strength of the in-situ leak repair was sometimes very strong and resilient. The sealing materials of leak-holes repaired at 20–60 psi could sometimes withstand a 100 psi water pressure without failure, demonstrating the potential of the approach to sustain aging and leaking infrastructure. In-situ leak repair can also occur naturally, and the success rate might be unintentionally altered by adjustment of chemistry or treatments that decrease or increase particulates. / Ph. D. / Old and leaking pipes waste water resources and can contaminate water. Upgrading of drinking water systems represents a large financial burden for water utilities and home owners. The traditional approaches to repair or replace the leaking water pipes are very effective, but will take decades to implement even if a financial commitment to do so was made immediately. A new approach of leak remediation, achieved by changing the drinking water chemistry, could potentially reduce leak rates and repair water leaks while in use without digging up the buried water pipes. Therefore, leak remediation could extend the lifetime of existing infrastructure at relatively low cost and inconvenience, and may be necessary if society cannot afford pipe replacement. Recent field observations indicate that metal corrosion, one type of reaction that eats up water pipes and causes water leaks, could clog the leaks via the corrosion products. And the repair in most cases could last for a long period of time. Our work was the first to reproduce the field observations in the laboratory, revealing that water pipe leaks could be successfully clogged or remediated by natural corrosion reaction products, if the water chemistry is favorable. Additionally, our work also showed that water leaks could be clogged or remediated by addition of water particles to drinking water, which was practiced by Roman engineers a long time ago. There are legitimate health concerns about particulates because they are indicative of microbial risks, but addition of particulates to water at low levels might heal pipes without such concerns. We also proved that in some cases the repaired materials clogging the leaks could withstand a very high household water pressure, showing that the sealing materials in water leaks repaired with natural corrosion products or added water particles could create long term repairs. With improved practical understanding this approach might be usefully applied, either intentionally to repair existing leaks, or make sure that changes to water chemistry do not unintentionally make problems worse.

Nitroglycerin (NG) is a toxic explosive commonly found in soil and contaminated groundwater at old manufacturing plants and military ranges. When NG enters an aquifer, it behaves as a dense non-aqueous phase liquid (DNAPL). Nitroglycerin is an impact sensitive explosive and therefore excavating the area to remove or treat the contaminant can be dangerous. In situ bioremediation and natural attenuation of NG have been proposed as remediation alternatives and it is therefore necessary to understand the degradation mechanisms of NG in contaminated soil and groundwater and investigate the potential for using bioremediation at contaminated sites. Many bacteria have been isolated for the ability to transform NG as a source of nitrogen, but no isolates have used NG as a sole source of carbon, nitrogen, and energy. We isolated Arthrobacter JBH1 from NG contaminated soil by selective enrichment with NG as the sole growth substrate. The degradation pathway involves a sequential denitration to 1,2-dinitroglycerin (DNG) and 1-mononitroglycerin (MNG) with simultaneous release of nitrite. Flavoproteins of the Old Yellow Enzyme (OYE) family capable of removing the first and second nitro groups from NG have been studied in the past and we identified an OYE homolog in JBH1 capable of selectively producing the 1 MNG intermediate. To our knowledge, there is no previous report on enzymes capable transforming MNG. Here we show evidence that a glycerol kinase homolog in JBH1 is capable of transforming 1 MNG into 1-nitro-3-phosphoglycerol, which could be later introduced into a widespread pathway, where the last nitro group is removed. Overall, NG is converted to CO2 and biomass and some of the nitrite released during denitration is incorporated into biomass as well. As a result, NG can be now considered a growth substrate, which changes the potential to bioremediate NG contaminated sites. The magnitude of the effect of biodegradation processes in the fate of NG in porous systems was unknown, and we have been able to quantify these effects, determine degradation rates, and have evidence that bioaugmentation with Arthrobacter sp. strain JBH1 could result in complete mineralization in contaminated soil and sediments contaminated with NG, without the addition of other carbon sources. Site specific conditions have the potential to affect NG degradation rates in situ. Experiments were conducted to investigate NG degradation at various pH values and NG concentrations, and the effects of common co-contaminants on NG degradation rates. Arthrobacter JBH1 was capable of growing on NG at pH values as low as 5.1 and NG concentrations as high as 1.2 mM. The presence of explosive co-contaminants at the site such as trinitrotoluene and 2,4-dinitrotoluene lowered NG degradation rates, and could potentially result in NG recalcitrance. Collectively, these results provide the basis for NG bioremediation and natural attenuation at sites contaminated with NG without the addition of other sources of carbon. Nonetheless, careful attention should be paid to site-specific conditions that can affect degradation rates.