Matching Items (5)
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Description
In situ remediation of contaminated aquifers, specifically in situ bioremediation (ISB), has gained popularity over pump-and-treat operations. It represents a more sustainable approach that can also achieve complete mineralization of contaminants in the subsurface. However, the subsurface reality is very complex, characterized by hydrodynamic groundwater movement, geological heterogeneity, and mass-transfer

In situ remediation of contaminated aquifers, specifically in situ bioremediation (ISB), has gained popularity over pump-and-treat operations. It represents a more sustainable approach that can also achieve complete mineralization of contaminants in the subsurface. However, the subsurface reality is very complex, characterized by hydrodynamic groundwater movement, geological heterogeneity, and mass-transfer phenomena governing contaminant transport and bioavailability. These phenomena cannot be properly studied using commonly conducted laboratory batch microcosms lacking realistic representation of the processes named above. Instead, relevant processes are better understood by using flow-through systems (sediment columns). However, flow-through column studies are typically conducted without replicates. Due to additional sources of variability (e.g., flow rate variation between columns and over time), column studies are expected to be less reproducible than simple batch microcosms. This was assessed through a comprehensive statistical analysis of results from multiple batch and column studies. Anaerobic microbial biotransformations of trichloroethene and of perchlorate were chosen as case studies. Results revealed that no statistically significant differences were found between reproducibility of batch and column studies. It has further been recognized that laboratory studies cannot accurately reproduce many phenomena encountered in the field. To overcome this limitation, a down-hole diagnostic device (in situ microcosm array - ISMA) was developed, that enables the autonomous operation of replicate flow-through sediment columns in a realistic aquifer setting. Computer-aided design (CAD), rapid prototyping, and computer numerical control (CNC) machining were used to create a tubular device enabling practitioners to conduct conventional sediment column studies in situ. A case study where two remediation strategies, monitored natural attenuation and bioaugmentation with concomitant biostimulation, were evaluated in the laboratory and in situ at a perchlorate-contaminated site. Findings demonstrate the feasibility of evaluating anaerobic bioremediation in a moderately aerobic aquifer. They further highlight the possibility of mimicking in situ remediation strategies on the small-scale in situ. The ISMA is the first device offering autonomous in situ operation of conventional flow-through sediment microcosms and producing statistically significant data through the use of multiple replicates. With its sustainable approach to treatability testing and data gathering, the ISMA represents a versatile addition to the toolbox of scientists and engineers.
ContributorsMcClellan, Kristin (Author) / Halden, Rolf U. (Thesis advisor) / Johnson, Paul C (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2013
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Description
Characterization of petroleum spill site source zones directly influences the selection of corrective action plans and frequently affects the success of remediation efforts. For example, simply knowing whether or not nonaqueous phase liquid (NAPL) is present, or if there is chemical storage in less hydraulically accessible regions, will influence corrective

Characterization of petroleum spill site source zones directly influences the selection of corrective action plans and frequently affects the success of remediation efforts. For example, simply knowing whether or not nonaqueous phase liquid (NAPL) is present, or if there is chemical storage in less hydraulically accessible regions, will influence corrective action planning. The overarching objective of this study was to assess if macroscopic source zone features can be inferred from dissolved concentration vs. time data. Laboratory-scale physical model studies were conducted for idealized sources; defined as Type-1) NAPL-impacted high permeability zones, Type-2) NAPL-impacted lower permeability zones, and Type-3) dissolved chemical matrix storage in lower permeability zones. Aquifer source release studies were conducted using two-dimensional stainless steel flow-through tanks outfitted with sampling ports for the monitoring of effluent concentrations and flow rates. An idealized NAPL mixture of key gasoline components was used to create the NAPL source zones, and dissolved sources were created using aqueous solutions having concentrations similar to water in equilibrium with the NAPL sources. The average linear velocity was controlled by pumping to be about 2 ft/d, and dissolved effluent concentrations were monitored daily. The Type-1 experiment resulted in a source signature similar to that expected for a relatively well-mixed NAPL source, with dissolved concentrations dependent on chemical solubility and initial mass fraction. The Type-2 and Type-3 experiments were conducted for 320 d and 190 d respectively. Unlike the Type-1 experiment, the concentration vs. time behavior was similar for all chemicals, for both source types. The magnitudes of the effluent concentrations varied between the Type-2 and Type-3 experiments, and were related to the hydrocarbon source mass. A fourth physical model experiment was performed to identify differences between ideal equilibrium behavior and the source concentration vs. time behavior observed in the tank experiments. Screening-level mathematical models predicted the general behavior observed in the experiments. The results of these studies suggest that dissolved concentration vs. time data can be used to distinguish between Type-1 sources in transmissive zones and Type-2 and Type-3 sources in lower permeability zones, provided that many years to decades of data are available. The results also suggest that concentration vs. time data alone will be insufficient to distinguish between NAPL and dissolved-phase storage sources in lower permeability regions.
ContributorsWilson, Sean Tomas (Author) / Johnson, Paul (Thesis advisor) / Kavazanjian, Edward (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2014
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Description
After the Salt River Project announced it would be closing the Navajo Generating Station (NGS) by the end of 2019, efforts to keep the plant open and running were immediately undertaken by community members, the Navajo and Hopi Nations, and the supplying mine owner Peabody Energy. With no buyers willing

After the Salt River Project announced it would be closing the Navajo Generating Station (NGS) by the end of 2019, efforts to keep the plant open and running were immediately undertaken by community members, the Navajo and Hopi Nations, and the supplying mine owner Peabody Energy. With no buyers willing to take on the project, the NGS and the supplying Kayenta Mine will be closing in December 2019. This report focuses on the effects of large coal-fired plant closure on the surrounding community in three comparative cases in an effort to understand what the Coconino County and the Navajo and Hopi Nations might be headed towards in the coming years. By examining economic factors such as poverty and unemployment, communities may be better prepared by knowing what to expect. Then, specific particularities the Navajo and Hopi Nations face in regards to remediation and redevelopment of the NGS area are analyzed and compared to six other cases of coal plants closed and remediated in the past. To continue facilitating a better understanding of a just transition for the communities dependent on the NGS and Kayenta mine for jobs, future studies could focus on remediation options and renewable energy (RE) capacity.
Keywords: coal plant closure, remediation, Navajo Generating Station
ContributorsAnderson, Melanie Jane (Author) / Sheriff, Glenn (Thesis director) / Mahoney, Maren (Committee member) / School of Politics and Global Studies (Contributor) / School of International Letters and Cultures (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2019-12
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Description
Terrestrial crude oil spills compromise a soil’s ability to provide ecosystem services by inhibiting plant life and threatening groundwater integrity. Ozone gas, a powerful oxidant, shows promise to aid in soil recovery by degrading petroleum hydrocarbons into more bioavailable and biodegradable chemicals. However, previous research has shown that ozone can

Terrestrial crude oil spills compromise a soil’s ability to provide ecosystem services by inhibiting plant life and threatening groundwater integrity. Ozone gas, a powerful oxidant, shows promise to aid in soil recovery by degrading petroleum hydrocarbons into more bioavailable and biodegradable chemicals. However, previous research has shown that ozone can change the soil pH and create harmful organic compounds.
The research objective was to determine the short-term ecological toxicity of ozonation byproducts on seed germination of three distinct plant types (radish, lettuce, and grass) compared to untreated and uncontaminated soils. We hypothesize that the reduction of heavy hydrocarbon contamination in soil by ozone application will provide more suitable habitat for the germinating seeds. The effect of ozone treatment on seed germination and seedling quality was measured using ASTM standards for early seedling growth in conjunction with a gradient of potting soil amendments. Ozonation parameters were measured using established methods and include total petroleum hydrocarbons (TPH), dissolved organic carbon (DOC), and pH.
This study demonstrated the TPH levels fall up to 22% with ozonation, suggesting TPH removal is related to the amount of ozone delivered as opposed to the type of crude oil present. The DOC values increase comparably across crude oil types as the ozonation dose increases (from a background level of 0.25 g to 6.2 g/kg dry soil at the highest ozone level), suggesting that DOC production is directly related to the amount of ozone, not crude oil type. While ozonation reduced the mass of heavy hydrocarbons in the soil, it increased the amount of ozonation byproducts in the soil. For the three types of seeds used in the study, these changes in concentrations of TPH and DOC affected the species differently; however, no seed type showed improved germination after ozone treatment. Thus, ozone treatment by itself had a negative impact on germination potential.
Future research should focus on the effects of post-ozonation, long-term bioremediation on eco-toxicity. By helping define the eco-toxicity of ozonation techniques, this research can improve upon previously established ozone techniques for petroleum remediation and provide economic and environmental benefits when used for soil treatment.
ContributorsJanuszewski, Brielle (Author) / Rittmann, Bruce (Thesis director) / Yavuz, Burcu (Committee member) / Civil, Environmental and Sustainable Eng Program (Contributor) / School of International Letters and Cultures (Contributor) / School of Politics and Global Studies (Contributor, Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Description

Cyanidioschyzon merolae, a unicellular extremophilic red algae, is found in hot, acidic groundwater with high concentrations of heavy metals. The association makes it an ideal species to investigate mechanisms of heavy metal tolerance, which may lead to its use in phyco- remediation wherein photosynthetic algae use biological processes to bind

Cyanidioschyzon merolae, a unicellular extremophilic red algae, is found in hot, acidic groundwater with high concentrations of heavy metals. The association makes it an ideal species to investigate mechanisms of heavy metal tolerance, which may lead to its use in phyco- remediation wherein photosynthetic algae use biological processes to bind and remove toxic substances. Two strains of C. merolae, MS1 and 10D, are genetically very similar, despite the latter lacking a cell wall. To investigate heavy metal toxicity and the role of the cell wall, the two strains of C. merolae were exposed to various concentrations of cadmium and cultures were evaluated spectrophotometrically to assess the impact on growth over a 7-day period. The IC50 values of MS1 and 10D were estimated to be 15 and 0.5 ppm CdCl2 respectively, indicating that the cell wall provides protection under the presence of heavy metals. Cadmium uptake was also measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to investigate metal ion exclusion and acidocalcisome-Cd2+ chelation as potential tolerance mechanisms. ICP-OES data indicated that 10D inoculum pretreated with phosphate depletion and re-supplementation, to induce Cd chelation in acidocalcisomes, then cultured in MA2 had the highest biomass Cd content of all strains and treatments (0.321 ppm; 31.55%). The cell wall clearly promotes survival and resistance to higher concentrations of environmental heavy metals, however, neither MS1 nor 10D seemed to be strains primed for phyco-remediation of heavy metal contamination through cellular uptake and sequestration.

ContributorsIsachsen, Iona (Author) / Lammers, Peter (Thesis director) / Seger, Mark (Committee member) / Lauersen, Kyle (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor) / School of Sustainability (Contributor)
Created2022-05