Barrett, The Honors College Thesis/Creative Project Collection
Barrett, The Honors College at Arizona State University proudly showcases the work of undergraduate honors students by sharing this collection exclusively with the ASU community.
Barrett accepts high performing, academically engaged undergraduate students and works with them in collaboration with all of the other academic units at Arizona State University. All Barrett students complete a thesis or creative project which is an opportunity to explore an intellectual interest and produce an original piece of scholarly research. The thesis or creative project is supervised and defended in front of a faculty committee. Students are able to engage with professors who are nationally recognized in their fields and committed to working with honors students. Completing a Barrett thesis or creative project is an opportunity for undergraduate honors students to contribute to the ASU academic community in a meaningful way.
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- Creators: Chemical Engineering Program
Description
Nitrate (NO3- ) and selenate (SeO42-) are common contaminants found in mining wastewater. Biological treatment has proved successful using bacteria capable of respiring NO3- into nitrogen gas and SeO42- into Se°. The Membrane Biofilm Reactor (MBfR) utilizes biofilm communities on the surface of hollow-fiber membranes to transform oxidized water contaminants into innocuous reduced products. For this project, I set up two MBfRs in a lead and lag configuration to reduce NO3- [input at ~40-45 mg NO3-N/L] and SeO42- [0.62 mg/L], while avoiding sulfate (SO42-) [~1600-1660 mg/L] reduction. Over the course of three experimental phases, I controlled two operating conditions: the applied hydrogen pressure and the total electron acceptor loading. NO3- in the lead MBfR showed average reductions of 50%, 94%, and 91% for phases I, II, and III, respectively. In the lag MBfR, NO3- was reduced by 40%, 96%, and 100% for phases I, II, and III. NO2- was formed in Stage I when NO3- was not reduced completely; nevertheless NO2- accumulation was absent for the remainder of operation. In the lead MBfR, SeO42- was reduced by 65%, 87%, and 50% for phases I, II, and III. In the lag MBfR, SeO42- was reduced 60%, 27%, and 23% for phases I, II, and III. SO42- was not reduced in either MBfR. Biofilm communities were composed of denitrifying bacteria Rhodocyclales and Burkholderiales, Dechloromonas along with the well-known SeO42--reducing Thauera were abundant genera in the biofilm communities. Although SO42- reduction was suppressed, sulfate-reducing bacteria were present in the biofilm. To optimize competition for electron donor and space in the biofilm, optimal operational conditions were hydrogen pressures of 26 and 7 psig and total electron acceptor loading of 3.8 and 3.4 g H2/m2 day for the lead and lag MBfR, respectively.
ContributorsMehta, Sanya Vipul (Author) / Rittmann, Bruce (Thesis director) / Ontiveros-Valencia, Aura (Committee member) / Chemical Engineering Program (Contributor) / School of International Letters and Cultures (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
This report investigates the mass-transfer kinetics of gas diffusion through an asymmetrical hollow-fiber membrane developed for the membrane biofilm reactor (MBfR) when it is used to microbiologically convert syngas (a mixture of H2, CO2, and CO) to organic products. The asymmetric Matrimid® membrane had superior diffusion fluxes compared to commercially available symmetric, three-layer composite and polypropylene single-layer membranes. The Matrimid® asymmetric membrane had a H2 gas-gas diffusion flux between 960- and 1600-fold greater than that of the composite membrane and between 32,000- and 46,800-fold greater than that of the single-layer membrane. Gas-gas diffusion experiments across the Matrimid® membrane also demonstrated plasticization behavior for pure CO2 and H2 gas feeds. In particular, a 10 psia increase in inlet pressure resulted in a 12-fold increase in permeance for H2 and a 16-fold increase for CO2. Plasticization was minimal for symmetric composite and single-layer membranes. Thus, diffusion fluxes were much higher for the asymmetric membrane than for the symmetric composite and single-layer membranes, and this supports the promise of the asymmetric membrane as a high-efficiency means to deliver syngas to biofilms able to convert the syngas to organic products. Gas-liquid diffusion was much slower than gas-gas diffusion, and this supports the benefit of using the MBfR approach over fermentation reactors that rely on sparging syngas.
ContributorsArafa, Omar M. (Author) / Rittmann, Bruce (Thesis director) / Torres, Cesar (Committee member) / Chemical Engineering Program (Contributor) / W.P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
With global warming becoming a more serious problem and mankind's alarming dependency on fossil fuels, the need for a sustainable and environmentally friendly fuel source is becoming more important. Biofuels produced from photosynthetic microorganisms like algae or cyanobacteria offer a carbon neutral replacement for petroleum fuel sources; however, with the technology and information available today, the amount of biomass that would need to be produced is not economically feasible. In this work, I examined a possible factor impacting the growth of a model cyanobacterium, Synechocystis sp. PCC6803, which is heterotrophic bacteria communities accompanying the cyanobacteria. I experimented with three variables: the type of heterotrophic bacteria strain, the initial concentration of heterotrophic bacteria, and the addition of a carbon source (glucose) to the culture. With experimental information, I identified if given conditions would increase Synechocystis growth and thus increase the yield of biomass. I found that under non-limiting growth conditions, heterotrophic bacteria do not significantly affect the growth of Synechocystis or the corresponding biomass yield. The initial concentration of heterotrophic bacteria and the added glucose also did not affect the growth of Synechocystis. I did see some nutrient recycling from the heterotrophic bacteria as the phosphate levels in the growth medium were depleted, which was apparent from prolonged growth phase and higher levels of reactive phosphate in the media.
ContributorsCahill, Brendan Robert (Author) / Rittmann, Bruce (Thesis director) / Krajmalnik-Brown, Rosa (Committee member) / W. P. Carey School of Business (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
The need for clean fuel sources is greater than ever, as fossil fuel dependence has soared and harmful emissions are being released into the atmosphere at increasingly higher rates. A viable solution to this issue is the use of microalgae for the creation of biofuels, as it holds a high concentration of lipids without requiring arable land for growth. This experiment studies downstream applications of microalgae, including how the extraction efficiency can be improved for greater lipid yield. 3-dimethyldodecylammonium propanesulfonate, myristyltrimethylammonium bromide and sodium dodecyl sulfate were used as surfactants to break down the algae cell walls and improve lipid recovery. The incubation times of the biomass in the surfactant were also studied at 0, 4.5, 24, 48 and 72 hours to more fully examine how surfactants affect the extraction of lipids. Along with this, hexane and isopropanol were used as the main extraction solvent in this experiment, but testing was done to compare these lipid yields to when ethyl acetate was used as the solvent. It was found that the MTMAB surfactant led to the greatest cell disruption, as its lipid yields were consistently higher than those of the other surfactants. Also, longer incubation times did improve the amount of lipid extracted, showing that the surfactants do have a strong effect on the cell breakdown. Finally, it was found that the ethyl acetate was a slightly more effective solvent than hexane and isopropanol in the conditions of this experiment. Overall, a stronger understanding of the wet extraction process was gained from these tests, as well as more insight into how some of the variables interact and work together during extraction.
ContributorsMartarella, Rebecca Lynne (Author) / Rittmann, Bruce (Thesis director) / Lai, Sean Yen-Jung (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12
Description
The microalgae Scenedesmus have been regarded as a potential source for biofuel production, having up to ~30% of dry weight as lipids used for biodiesel fuel production. Electro-selective fermentation (ESF) is a novel approach that can selectively degrade proteins and carbohydrates while conserving lipids within algal cells, while simultaneously enhancing lipid wet-extraction and biohydrogenation. ESF is a combination of SF and Microbial Electrolysis Cell (MEC) technologies. Experiments reported here prove that ESF is an effective means of enhancing lipid wet-extraction by ~50% and achieving 36% higher lipid saturation conversion, compared to SF, over 30 days of semi-continuous operation. Anode-respiring bacteria (ARB) residing on the anode surface produced a current that led to increased rate of organic substrate utilization, protein degradation, and ultimately enhanced lipid extraction and biohydrogenation that converted unsaturated to saturated fatty-acids. Thus, ESF provides a promising method for enhancing lipid extraction for biofuel production.
ContributorsRastogi, Neil K (Author) / Rittmann, Bruce (Thesis director) / Liu, Liu (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05