ETDs

This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.

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Enzyme-induced carbonate precipitation for the mitigation of fugitive dust

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ABSTRACT Enzyme-Induced Carbonate Precipitation (EICP) using a plant-derived form of the urease enzyme to induce the precipitation of calcium carbonate (CaCO3) shows promise as a method of stabilizing soil for the mitigation of fugitive dust. Fugitive dust is a significant problem in Arizona, particularly in Maricopa County. Maricopa County is…

ABSTRACT Enzyme-Induced Carbonate Precipitation (EICP) using a plant-derived form of the urease enzyme to induce the precipitation of calcium carbonate (CaCO3) shows promise as a method of stabilizing soil for the mitigation of fugitive dust. Fugitive dust is a significant problem in Arizona, particularly in Maricopa County. Maricopa County is an EPA air quality non-attainment zone, due primarily to fugitive dust, which presents a significant health risk to local residents. Conventional methods for fugitive dust control, including the application of water, are either ineffective in arid climates, very expensive, or limited to short term stabilization. Due to these limitations, engineers are searching for new and more effective ways to stabilize the soil and reduce wind erosion. EICP employs urea hydrolysis, a process in which carbonate precipitation is catalyzed by the urease enzyme, a widely occurring protein found in many plants and microorganisms. Wind tunnel experiments were conducted in the ASU/NASA Planetary Wind Tunnel to evaluate the use of EICP as a means to stabilize soil against fugitive dust emission. Three different soils were tested, including a native Arizona silty-sand, a uniform fine to medium grained silica sand, and mine tailings from a mine in southern Arizona. The test soil was loosely placed in specimen container and the surface was sprayed with an aqueous solution containing urea, calcium chloride, and urease enzyme. After a short period of time to allow for CaCO3 precipitation, the specimens were tested in the wind tunnel. The completed tests show that EICP can increase the detachment velocity compared to bare or wetted soil and thus holds promise as a means of mitigating fugitive dust emissions.
ContributorsKnorr, Brian (Author) / Kavazanjian, Edward (Thesis advisor) / Houston, Sandra (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2014
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Measurement and Variability of Crude Urease Enzyme for Enzyme Induced Carbonate Precipitation (EICP) Applications

Description
Two challenges in the implementation of enzyme induced carbonate precipitation(EICP) are the cost of enzyme and the variability of the enzyme. Urease enzyme costs can be lowered drastically with the use of crude extract from plant materials, but experience has shown variability in the source of the crude urease enzyme, the crude urease…

Two challenges in the implementation of enzyme induced carbonate precipitation(EICP) are the cost of enzyme and the variability of the enzyme. Urease enzyme costs can be lowered drastically with the use of crude extract from plant materials, but experience has shown variability in the source of the crude urease enzyme, the crude urease enzyme extraction methods, and the concentration of the EICP solution can cause significant variability in the efficacy of the EICP solution. This thesis examines the variability in the efficacy of crude enzyme derived from jack beans (Canavalia ensiformis) and sword beans (Canavalia gladiata), two of the most commonly used sources of urease enzyme for EICP. The sources of variability investigated herein include the crude extraction method (including the effect of the bean husks on extraction) and different chemical constituent concentrations. These effects were assessed using enzyme activity measurements and precipitation efficiency tests. The activity tests were performed via spectrophotometry using Nessler's reagent. The precipitation tests looked at the influence of chemical constituent concentrations of 0.67 M calcium chloride and 1 M urea with non-fat dry milk in the EICP solutions and a higher concentration solution with chemical constituent concentrations of 2 M for both calcium chloride and urea with non-fat dry milk. The high concentration solution was selected based on preliminary testing results to maximize carbonate precipitation in one cycle of treatment. Significant sources of a decline in activity (and increase in variation) of the crude urease enzyme were found in extraction from sword beans with husks, high chemical constituent concentrations, and juicing instead of cheesecloth filtration. This thesis also examines the accuracy of commonly used correlation factors for converting electrical conductivity to urease enzyme activity. Crude jack bean and sword bean urease enzyme activity measurement via electrical conductivity was found to have a correlation coefficient that differed from the previously reported correlation when compared to activity measured via the more accurate spectrophotometry using Nessler’s reagent measurements.
ContributorsPearson, Rayanna (Author) / Kavazanjian, Edward (Thesis advisor) / Khodadadi Tirkolaei, Hamed (Committee member) / Salifu, Emmanuel (Committee member) / Arizona State University (Publisher)
Created2022