A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item USE OF DRINKING WATER TREATMENT RESIDUALS AS A SOIL AMENDMENT FOR STORMWATER NUTRIENT TREATMENT(2010) O'Neill, Sean William; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Stormwater runoff has been implicated as a major source of excess nutrients to surface waters, contributing to the development of eutrophic conditions. Bioretention, a promising technology for urban stormwater pollution treatment, was investigated to determine if an aluminum-based water treatment residual (WTR) amended bioretention soil media (BSM) could adsorb phosphorus to produce discharge concentrations below 25 μg/L. Batch, small column, and vegetated column studies were employed to determine both the optimal BSM mixture and media performance. Media tests demonstrated P adsorption proportional to WTR addition. Final selected experimental media consisted of 75% sand, 10% silt, 5.8% clay, 5.2% WTR, and 3.4% bark mulch (air dry mass basis).This media showed excellent P removal relative to a non-WTR-amended media. Whereas the control media leached P (71.1% increase in mass), the experimental media adsorbed 85.7% of the P mass applied, displaying a cumulative effluent EMC of 16.1 μg/L, below the 25 μg/L goal.Item Evaluation of Leaching Protocols for the Testing of Coal Combustion Byproducts(2010) Becker, Jason Louis; Aydilek, Ahmet; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Beneficial reuse of coal combustion byproducts requires an evaluation of metal leaching potential. Reuse of high carbon fly ash in highway embankment construction was evaluated using different soil-fly ash mixtures and three common leaching tests: the water leach test (WLT), the Toxicity Characteristic Leaching Procedure (TCLP), and the column leach test (CLT). The effect of test methodology and pH on Cu, As, and Cr leaching was examined. TCLP concentrations for Cu and As exceeded those from WLTs in the majority of mixtures due to lower pH conditions, while Cr was higher in the WLT for alkaline fly ash mixtures. Peak CLT concentrations were higher than TCLP and WLT concentrations for the majority of mixtures, but usually decreased rapidly, suggesting that leachate concentrations might exceed regulatory limits, but only for a short time. Based on these results, a combined WLT and CLT leaching protocol for testing fly ash mixtures is presented.Item The Hydrologic and Water Quality Performance of the Sligo-Dennis Bioretention Cell(2010) Olszewski, Jennifer Marie; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention cells have been found to improve the hydrologic and water quality performance of impervious areas such as parking lots. The current study recorded hydrologic data from a bioretention cell in Silver Spring, MD, over a period of 2 years, collecting water quality data from 14 storm events. Data showed the cell completely captured storm events that produced less than or equal to 1.27 cm of rainfall, after which a linear relationship between cell outflow and cell inflow was observed. The cell was found to reduce the site CN from 96 down to 79 and to have a CN of 96 when assessed as a separate land use. The hydrologic performance was also compared to that of a forested stream near Baltimore, MD. While the cell performed similarly volumetrically for storms producing less than or equal to 2 cm of rainfall, the Sligo-Dennis flow-durations were typically half the length and double the flowrate of those of the forested stream.Item Design and testing of a microbial fuel cell for the conversion of lignocellulosic biomass into electricity(2010) Gregoire, Kyla Patricia; Becker, Jennifer; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Previous research has demonstrated that microbial fuel cells (MFCs) have the ability to degrade soluble substrates such as wastewater; however, very few studies have attempted the conversion particulate biomass to electricity in an MFC. A single-chamber, air cathode MFC was developed using a solid, lignocellulosic substrate (corncob pellets) as the electron donor. The first trial, using a prototype reactor with a graphite rod anode, ran for 415 hours, and generated a maximum open circuit voltage and current of 0.67 V and 0.25 mA, respectively. The second trial employed graphite brush anodes and multiple microbial inocula. A pasteurized soil inoculum resulted in negligible power (P = 0.144 mW/m3). The addition of rumen fluid, which naturally contains cellulose-degrading microorganisms, and Geobacter metallireducens, resulted in Pmax values of 77 mW/m3 and 159 mW/m3, respectively. Analysis of hydrogen, methane, organic acids, and the mass of substrate consumed provided insight into the relationship between cellulose oxidation, methanogenesis, and power production.Item SPILL AND BURNING BEHAVIOR OF FLAMMABLE LIQUIDS(2010) Benfer, Matthew; Quintiere, James G; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Unconfined liquid spill depths were measured for two liquid fuels and three non-flammable liquids atop a smooth concrete pad. Unconfined liquid spill thicknesses were found to be less than 0.1 cm in all fuels and liquids similar to fuels. Spill fires were conducted with volumes ranging from 0.2 ml to 450 ml for gasoline and denatured alcohol. Average burning rates for both unconfined liquid fuel spill fires increased linearly with increasing volume spilled. A liquid spill thickness model was developed and compared to experimental data. Comparisons showed good predictions for half of the liquids used. In addition, a liquid spill fire burning rate model was also developed and checked with experimental data. This model provided good qualitative results, however further development is still needed.Item USE OF INORGANIC BY-PRODUCT AMENDED COMPOST/MANURE TO SEQUESTER METALS AND PHOSPHORUS FROM DIFFUSE SOURCE POLLUTION(2010) Kim, Hunho; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Heavy metals and nutrients released from diffuse sources by urban and agricultural runoff are important pollutants causing aquatic toxicity and/or eutrophication in water bodies. Diffuse source pollution is difficult to address because of the dispersed and often dynamic nature of the flows, which often lead to economic impracticality of traditional approaches. Beneficial use of industrial and agricultural byproducts as amendments or media/barriers to treat diffuse source pollution can provide cost-effective solutions over various ranges of pollutants and flows. Two applications of this concept were examined in this research study: 1) Immobilization of phosphorus using Fe/Mn inorganic materials and an anaerobic incubation process; (2) Heavy metal removal from roof/wall runoff using a Biomat barrier supplemented with compost and inorganic byproducts. Through the first study, three different low cost Fe/Mn-rich materials (iron ore, steel slag and Mn tailings) were evaluated as amendments to decrease phosphorus mobility from manure. Anaerobic incubation of fresh dairy manure with the Fe/Mn rich materials was also evaluated. Steel slag addition significantly decreased water soluble phosphorus by 93% and Mehlich III extracted phosphorus by 80%, compared to manure-only control. An anaerobic incubation of manure with Fe ore decreased 62% water extractable P compared to fresh manure and 76% compared to incubated manure, due to oxalate extractable Fe (considered as amorphous Fe) increase. This work suggests possible anaerobic incubation use for non-active crystalline byproducts to decrease P loss from manure. Through the second study, the feasibility of Biomat use, a mixture of sand, compost and inorganic byproducts, was evaluated through column and bench-scale experiments to remove dissolved heavy metals. A 25% grass/food waste compost + steel slag + sand column was the best media, not only demonstrating excellent metal removals from diffuse sources but also exhibiting the immobility of sorbed metals on the media. Throughout bench scale experiments, hydraulic characteristics and heavy metal removal performance of the mat media were evaluated in perpendicular flow. After all bench scale experiments, metal extractions showed performed very limited metal mobility in the media. Design parameters, implementations, and recommendations for future full scale Biomat application in a field were established.Item GIS-Based Odor Impact Assessment from Biosolids Land Application Sites(2010) Intarakosit, Eakalak; Baecher, Gregory B.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids applied to agricultural land may upset neighboring communities due to the inherent malodorous smell of biosolids. The problem of the odor becomes a major concern in the wastewater treatment industry when community responses could vary from complaints to legal action to ban or reduce biosolids recycling through land. Unlike odor at a wastewater treatment facility, which is produced from the characteristics of wastewater itself and from individual unit processes, land-applied biosolids odor depends not only on the quality of biosolids, but also on the biosolids emissions levels, unfavorable weather conditions and topographic characteristics, and variation of human perception. Those factors increase the complexity of nuisance odor at land application sites. This dissertation aims to assess biosolids emission impacts on surrounding communities by estimating the level of biosolids odor emissions, simulating odor dispersion, and quantifying human perception to biosolids odor. Odor emission rates at land-applied biosolids fields were estimated using three different approaches: assumed flow rate, statistical inference, and simulated-flux chamber. The estimated emission rates were used as an input to dispersion models. The U.S. Environmental Protection Agency Regulatory Models, both screening and refined models, were used to simulate dispersion of biosolids odor at land application sites. A Geographic Information System (GIS) was employed to support modeling steps and to create maps. Appraisal of odor perception by receptors was assessed by use of Steven's psychophysics power law. The District of Columbia Water and Sewer Authority (DCWASA) land application fields in Virginia were used as case studies. More specifically, 45 fields in Albemarle and Orange Counties were focused on. Concentration prediction maps along with probability maps were created to support visualization and provide information on potential odor impacts to communities. Possible human perceptions were expressed in Intensity maps. The methods and results described in this dissertation can support decision makers in selecting appropriate land application sites prior distributing biosolids to reduce adverse effects from land-applied biosolids.Item Evaluation of solder-joint reliability for a 10mm Quad Flat Leadless package with top-side paddle using classical models for a leadless device and accelerated life testing(2009) Levin, Mark Alan; Barker, Dr. Donald; Reliability Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The standard QFN package consists of a leadless perimeter array and a bottom solderable thermal paddle. The thermal performance of the package can be improved by moving the paddle to the topside. The soldered surface area of the package reduces by about 80% with a top-side paddle. The soldered-joint life will also reduce due to the significant thermal coefficient of expansion mismatch between the QFN package and the circuit board. The solder-joint reliability of a large QFN package with top-side paddle is not well understood. This thesis evaluates the solder-joint reliability of a 10mm square leadless QFN package with top-side paddle. The analysis includes several classical models for a leadless package and compares modeling results to accelerated reliability testing. The accelerated tests include the influence mold compound and lead finish play on solder-joint life and ways to improve solder-joint reliability.Item The Spatial Distribution of Imperviousness in Watershed Hydrology(2009) Mejia, Alfonso Ignacio; Moglen, Glenn E.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Urbanization affects the hydrology of watersheds often leading to increases in runoff volumes and peak flows. These impacts are mainly attributed to the presence of imperviousness on the landscape which inhibits the soil infiltration process. Normally, these impacts are studied at the hillslope scale and under lumped watershed conditions. The impacts at the watershed scale under more spatially distributed conditions have been studied less. Advancements in spatial observations and techniques, distributed hydrologic modeling, and greater understanding of the importance of scale in hydrology have increased the feasibility and need for including spatial data sets and methods into hydrologic investigations. This dissertation focuses on understanding the role and importance of the spatial distribution of imperviousness in watershed hydrology. The spatial distribution of imperviousness is investigated by incorporating various spatial datasets, techniques, and modeling approaches that are used routinely for the hydrology of natural watersheds but less frequently for urbanized conditions. The distribution of imperviousness is investigated based on three approaches. The first approach uses optimization concepts to study where imperviousness can be placed in the watershed to reduce negative impacts on flooding. The second approach develops, implements, and tests a hydrologic event-based model to study the influence of the spatial distribution of imperviousness on the hydrologic response. The last approach relates analytically the space-time variability of rainfall, runoff, and the routing process to the imperviousness pattern, and synthesizes the complex space-time variations into a simpler framework. From the first approach distinct patterns of imperviousness were obtained that embodied water resources objectives. For example, the clustering of imperviousness along the main channel was found to globally reduce peak flows along the stream network. The second approach indicated that the overall imperviousness pattern can have a considerable impact on the hydrologic response. The last approach showed that the spatial patterns of rainfall and imperviousness can interact to increase or decrease the average amount of rainfall excess. The main contribution from this research is a larger understanding of the role of the spatial distribution of imperviousness in watershed hydrology. It also demonstrates the usefulness of applying hydrologic knowledge of natural watersheds to anthropogenically-altered watersheds.Item Environmental Performance and Sustainability of Bioretention Cells(2009) Jones, Philip Sumner; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bioretention cells use vegetation and soil media for source control of urban stormwater runoff, alleviating waterway impairment. Environmental performance of two cells was investigated. First, a cell capturing road runoff was monitored for one year. At a second cell, media were sampled to measure lifetime metal accumulation and evaluate the environmental, health, and maintenance implications of metal sequestration. Monitoring found high metal and suspended solids removal, generally poor nutrient performance, and chloride export. Runoff volume and peak flow rate reduction occurred for small storm events. For larger events, outflow volume consistently exceeded inflow because of unique site conditions. Lead, copper, and zinc media concentrations in the second cell were elevated but well below cleanup thresholds. Metals were strongly bound to bioretention media and largely immobile; lead bioavailability was comparable to generic soil estimates. Most metal accumulation was near the inflow point in the top 3 to 12 cm of media.