Theses and Dissertations from UMD
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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 give thesis/dissertation in DRUM
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Item Electricity Generation Using Sediment Microbial Fuel Cells with a Manganese Dioxide Cathode Catalyst(2014) Tatinclaux, Maia; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wastewater treatment plants employ an energetically costly aerobic unit process to remove organic matter from municipal wastewater; this process is known as activated sludge. Microbial fuel cells (MFCs) present an anaerobic, energy-saving approach to wastewater treatment that results in electricity generation. However, MFCs are often limited by internal resistance from membrane fouling and slow cathodic oxygen reduction. This work examined an option to overcome these limitations-- adapting membrane-less sediment microbial fuel cells (SMFCs) for use with wastewater as an organic substrate by using floating carbon cloth air cathodes coated with an oxygen reduction reaction (ORR) catalyst. The performance of a platinum ORR catalyst at the cathode was compared to a manganese dioxide ORR catalyst and several additional cathode materials and reactor configurations were tested to optimize SMFC performance. The MnO2 catalyst, though significantly cheaper than platinum, was unable to sustain consistent high cathode potentials in wastewater over time.Item OPTIMIZATION AND EQUILIBRIUM MODELING FOR RENEWABLE ENERGY: FOCUS ON WASTEWATER-TO-ENERGY APPLICATIONS(2013) U-tapao, Chalida; Gabriel, Steven A; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation presents three novel optimization models for sustainable wastewater management. The Blue Plains Advance Wastewater treatment plant (AWTP) operated by the District of Columbia Water and Sewer Authority (DC Water) is used as a case study. The application to the Blue Plains AWTP is presented to illustrate the usefulness of the model and how wastewater treatment plants (WWTPs), solid waste disposal plants, community management groups can actively and positively participate in energy and agricultural markets. Besides the conversion of the solid end products into biogas and electricity via digesters, WWTP can also produce Class B biosolids for land application or Class A biosolids for use as fertilizer. Chapter 1 introduces the Blue Plains case study and other important aspects of wastewater management. The first problem, discussed in Chapter 2, is a multi-objective, mixed-integer optimization model with an application to wastewater-derived energy. The decisions involve converting the amount of solid end products into biogas, and/or electricity for internal or external purposes. Three objectives; maximizing total value, minimizing energy purchased from external sources and minimizing carbon dioxide equivalent (CDE) emissions were presented via an approximation to the Pareto optimal set of solutions. The second type of problem is a stochastic multi-objective, mixed-integer optimization model with an application to wastewater-derived energy and is presented in Chapter 3. This model considers operational and investment decisions under uncertainty. We also consider investments in solar power and processing waste from outside sources for revenue and other benefits. The tradeoff decision between operational and investment costs and CDE emissions are presented. The third type of optimization model is a stochastic mathematical program with equilibrium constraints (MPEC) for sustainable wastewater management and is presented in Chapter 4. This two-level optimization problem is a stochastic model with a strategic WWTP as the upper-level player. The lower-level players represent the fertilizer, natural gas, compressed natural gas (CNG) and electricity markets. All the lower-level players are price-takers. Chapter 5 considers a comparison of the three optimization models discussed above and highlights differences. Chapter 6 provides conclusions, contributions, and potential future directions.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 EVALUATION OF ANTIBIOTIC-RESISTANT BACTERIA IN TERTIARY TREATED WASTEWATER, RECLAIMED WASTEWATER USED FOR SPRAY IRRIGATION, AND RESULTING OCCUPATIONAL EXPOSURES(2010) Goldstein, Rachel Elizabeth Rosenberg; Sapkota, Amy R; Maryland Institute for Applied Environmental Health; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Occupational exposures to vancomycin-resistant Enterococcus (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) in reclaimed wastewater used for spray irrigation were evaluated. In 2009, wastewater was collected from a tertiary-treatment facility, and reclaimed wastewater, nasal and dermal swab samples from an irrigation site. Samples were evaluated for MRSA and VRE using standard methods, PCR, and susceptibility testing. MRSA and VRE were isolated from all wastewater samples except effluent. While wastewater MRSA isolates were multidrug resistant (98%), no MRSA was isolated in irrigation water or swabs. VRE was isolated in one irrigation water sample. Fewer irrigation workers were colonized with S. aureus (31%) compared to controls (46%), but they harbored more multidrug resistant S. aureus. This is the first study to 1) evaluate antibiotic-resistant bacteria (ARB) in U.S. reclaimed wastewater and resulting occupational exposures, and 2) detect MRSA in U.S. wastewater. The findings suggested that tertiary wastewater treatment effectively reduced MRSA and VRE.Item Integration of Sustainable Infrastructure at a Neighborhood Scale(2006-12-20) Binder, Michael P; Kelly, Brian; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)By concentrating power generation, water treatment and waste management facilities at large centralized sites on the edge of its cities, modern industrial society allows us to ignore our responsibility for the damage we are doing to the environment. This thesis project proposes the integration and distribution of neighborhood-scaled power and waste management functions throughout our urban centers, demonstrating the efficacy of localized infrastructure based on sustainable natural and man-made cycles, making it simultaneously beautiful and providing a desirable amenity to the residents. The heart of this thesis project is the design for an indoor garden space which also integrates solar power management, nature-inspired wastewater treatment and solid waste recycling. The program will include an environmental education center using the facility as an operational example. A site in Northwest Washington DC, bounded by New Jersey Ave., New York Ave., North Capitol and K Streets has been selected for its redevelopment opportunities.