UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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Item ENERGY-POSITIVE METHODS OF WASTEWATER TREATMENT-- AN EXAMINATION OF ANAEROBIC DIGESTION & BIO-ELECTROCHEMICAL TECHNOLOGY(2013) Gregoire, Kyla Patricia; Tender, Leonard; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The results presented here demonstrate plausibility of a hybrid Anaerobic Digester-Microbial Fuel Cell (AD-MFC) system for anaerobic primary (AD) and secondary (MFC) treatment and resource recovery from high-strength wastewater. We empirically determine the treatment efficiencies and energy densities achieved by the AD and MFC processes, both separately and when integrated as primary and secondary unit operations. On the basis of current production, undigested wastewater yielded an stable anodic current of 131 A/m3 when continuously fed to triplicate MFCs (chronoamperometry, Ean, -0.200V vs. Ag/AgCl). Substrate limitations in digested sludge reduced anodic current--36 A/m3, 17 A/m3, and 9 A/m3 were achieved from 6d, 13d, and 21d digestate, respectively. Cathodic limitations severely limited power/energy production by the MFC, with maximum power output of 11 W/m3 (69 mW/m2). Presumably, this was due to mass transport of oxygen reduction intermediates. When AD and MFC processes are de-coupled (i.e. each fed with undigested wastewater), the energy realized from AD (as biogas) was, on average, 29.6 kJ per m3 wastewater treated (8.2 Wh/m3), whereas the MFC produced, on average, 2.1 kJ per m3 wastewater treated (0.58 Wh/m3). On the basis of COD removal, AD separately generated 9,110 kJ per kg COD removed (2,530 Wh/kg COD) whereas MFC separately generated 0.18 kJ per kg COD removed (0.05 Wh/kg COD). When combined as primary and secondary unit processes with a 6-d digestion period (reaction period which yielded the highest net energy production), the energy output from AD (as biogas) was 23.9 kJ per m3 wastewater; the energy output from MFC (as electrical power) was 2.1 kJ per m3 wastewater. MFC treatment rates exceeded 90% COD removal, 80% VS removal and 80% TS removal, likely owing to the upflow, baffled reactor design that maximized interaction between wastewater and the anodic biofilm. Results indicate an inverse logarithmic relationship between digester retention time and subsequent MFC current production, i.e. maximal MFC current production is achieved with undigested waste, and an inverse linear relationship between digester retention time and subsequent COD/VS removal in MFCs. Breakthroughs must be made to address cathodic limitations of MFCs, before scaling is practically or economically viable.Item Promoting the production and consumption of wheat-based functional foods rich in antioxidants.(2008-11-20) Luther, Marla West; Yu, Liangli; Food Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The present study evaluated the effects of solid state yeast treatment and thermal processing on the extractability and in-vitro bioavailability of antioxidants from wheat bran and whole-wheat pizza crusts, and developed sample outreach materials for promoting the consumption of whole-wheat functional foods. The first section analyzed the effect of solid-state yeast treatment on the extractable antioxidant properties of wheat bran. Wheat bran was treated with ten commercially available food grade yeasts under solid state conditions. Antioxidant properties were evaluated by measuring total phenolic content, and radical scavenging capacities against the cation ABTS, peroxyl (ORAC), DPPH (RDCS), and hydroxyl (HOSC) radicals. Results showed that under the selected conditions, yeast strain LBE.11 was able to increase ORAC and HOSC radical scavenging by 50% and 67%, respectively. The second part of this study evaluated the impact of bran particle size, fermentation time, and baking time and temperature on the 100% ethanol extractable antioxidant capacities of whole wheat pizza crust. Results showed that pizza crusts produced with reduced bran particle size maintained antioxidant capacity throughout thermal processing. At 18 hrs of fermentation RDSC and TPC values of the pizza crusts were increased by 17% and 23%, respectively. Increasing baking temperature increased RDSC values by 14 and 17% for pizza crusts prepared with Lakin and Trego variety wheat, respectively. The third part of this study analyzed the in-vitro bioavailability of wheat antioxidants in baked pizza crusts. Antioxidant properties were evaluated by measuring total phenolic content, and radical scavenging capacities against the cation ABTS, peroxyl (ORAC), DPPH (RDCS), and hydroxyl (HOSC) radicals. Pizza crusts with higher available antioxidants may have a greater level of bio-available antioxidants. The final segment of this research was to develop a tri-fold for promoting the consumption of whole wheat foods. The tri-fold was designed to include food-specific knowledge, consumption consequences knowledge in addition to recipes and directions, and nutritional facts. Integrating research findings into outreach materials may be an effective way to increase functional food consumption. Results from these studies indicate that there are numerous ways to increase antioxidant levels in the diet.