The ability of a self-contained denitrification system, using fermentation products from waste fish solids, to maintain reliable performance was studied. Denitrification performance was described kinetically and stoichiometrically under different initial nitrate-nitrogen and soluble organic carbon to nitrate-nitrogen ratios. Characterization of soluble organic carbon (measured as soluble chemical oxygen demand, sCOD) indicated that volatile fatty acids (VFA) were generated during the fermentation of the waste fish solids. The results from batch experiments showed that over the range of initial nitrate concentrations studied, complete denitrification was achieved within 6 hrs. sCOD, nitrite, and nitrate profiles across several batch experiments showed that transient nitrite accumulations occurred, but the maximum measured concentrations never completely inhibited nitrate removal. The results suggested that the rate of denitrification was influenced by the initial sCOD to nitrate-nitrogen ratio when transient nitrite concentrations remained below 20 mg/L. However, when nitrite-nitrogen exceeded 25 mg/L, the rate of denitrification was negatively correlated with the maximum measured nitrite-nitrogen concentration. The stoichiometric carbon requirement was not correlated to any parameters believed to influence carbon consumption. After complete denitrification was achieved residual sCOD was still measured, which could not be identified as VFAs. Batch aerobic treatment of denitrified effluent resulted in a 60 to 70 % removal of the residual sCOD when allowed to react for 8 days. It was further determined that the residual sCOD exerted an oxygen of 5.81 on g COD/g C. Additional studies were conducted to maximize sCOD production during fermentation. Increasing the fermentation temperature from 28 oC to 40 oC facilitated a 36 % increase in the specific sCOD production rate (g sCOD/ g fish solids applied). In addition to sCOD production, ammonia production increased 20 % when the fermentation was conducted at the elevated temperature. An analysis comparing the cost of methanol addition to support denitrification to the cost associated with fermenting waste fish solids indicated that supplementing fermentation products with methanol resulted in the least costly strategy for promoting denitrification of an aquaculture waste stream. / Master of Science

Surface mining for coal in the Central Appalachians contributes total dissolved solids (TDS) to headwater streams, especially below larger mines and associated valley fills. My objective was to characterize the geochemical properties of a range of surface soils and associated geologic strata from the Central Appalachian coalfields and to relate those properties to simple field indicators, such as color or rock type. I hypothesized that these indicators can accurately predict certain geochemical properties. Thirty-three vertical weathering sequences were sampled from eight surface mines throughout the Central Appalachian coalfields, for a total of 204 individual samples. No differences were found among sites in overall saturated paste specific conductance (SC; used as a proxy for TDS) levels, but significant geochemical differences existed among samples. Sulfate release dominated SC levels, followed closely by Ca and Mg. Surficial soils and sandstones were yellowish-brown in color, high in citrate dithionite (CD) - extractable Al, Fe, and Mn, and low in SC, compared to underlying sandstones, shales, and mudstones, which were grayish to black, low in CD-extractable Al, Fe, and Mn, and significantly higher in SC. Saturated paste As and P were higher in A horizons, whereas Se was significantly higher in unweathered bedrock than in soil or weathered bedrock. Samples generating exothermic reactions with 30% H2O2 produced higher SC levels, sulfate, Mg, and Se. In conclusion, the mine spoils studied varied widely in geochemical properties. The simple field indicators presented here, such as color, weathering status, rock type, and H2O2 reaction can provide valuable guidance for identifying TDS risk which would greatly improve operator's ability to actively minimize TDS release. I recommend using soil and weathered, yellowish-brown sandstone layers as a source of low TDS spoil material whenever possible. The H2O2 field test is useful for identification of TDS and Se risk. Underlying unweathered bedrock layers should be treated as "potentially high TDS spoils". Particularly high risk spoils include gray to black mudstones and shales, coals, and coal associated shales, mudstones, and clays directly associated with coal seams. I recommend hydrologically isolating these spoils using techniques similar to those used historically for acid-forming materials. / Ph. D.

The purpose of this thesis has been achieved. Vector notation has been used in developing the equations necessary for the analysis of three dimensional elastic rings. An elastic centroid for the elastic ring has been located with a tabular procedure for exacting the solution to the problem. For a comparison of the solutions between the method based on three elastic centroids with the method based on one elastic centroid, one need refer to Figures 7 and 10. Comparing the two methods, it is the author's opinion that the method herein presented is superior if for no other reason than simplicity. The development of the six equations can be readily followed and the tabular form of Figure 7 presented as an orderly means for obtaining the coefficients of the six unknowns. Figure 10 presents a method involving a similar tabular form as in Figure 7 along with the additional calculations that must be made before the correction moments and shears can be obtained. The necessity of these additional terms serves to obscure the physical significance of the final equations. / Master of Science

Historically, environmental research associated with Appalachian coal surface mines focused on acid mine drainage and reclamation. Recent studies suggest that electrical conductivity (EC) levels above 500 ?S cm-1 can impair Appalachian streams, shifting the focus towards limiting release of total dissolved solids (TDS) and associated elements of concern. Previous column studies utilized an unsaturated bi-weekly leaching design to evaluate the behavior of overburden with respect to TDS, pH, and trace metals. The objective of this study was to determine the effects of column saturation, leaching solution chemistry, and leaching cycle on the release of TDS and associated elements from an unweathered sandstone. Treatments evaluating potential saturation, leaching solution pH, and leaching cycle included saturated, standard method, vacuum, and standpipe fitted columns; simulated acid rain, de-ionized water, and CaCO3 leaching solutions; and 2x week-1, 1x week-1, 2x month-1, and 1x day-1 leaching cycles. Saturation level in the column significantly impacted leachate pH, EC level, and the release of sulfate, bicarbonate, and associated cations by potentially affecting trace sulfide oxidation and carbonate dissolution reactions. Little evidence of saturation was noted with the standard method. Leaching solution bulk chemistry did not alter leachate chemistry. Longer times between dosing cycles corresponded to higher EC, bicarbonate, and associated cation levels, especially over time. Sulfate, Ca, and Se exhibited the greatest percent release based on total mass losses during peak elution. For managing TDS, time between precipitation events and saturation level can strongly affect short and long-term EC level, its major contributors, and elements of concern. / Master of Science

The adsorption isotherms for ethanol-cyclohexane, ethanol-benzene, and benzene-cyclohexane vapor mixtures on Cab-O-Sil and on Graphon at 20, 30, and 40°C were measured at constant total pressure. The adsorption isotherms for the pure components were also obtained. The ethanol/Graphon isotherms were intermediate between Types II and III; for the other systems, Type II isotherms were obtained. The amounts of the pure vapors adsorbed on Cab-O-Sil followed the order ethanol > benzene > cyclohexane. The adsorption isotherms for benzene and cyclohexane on Graphon were almost identical. Except at low relative pressures, the amount of ethanol adsorbed on Graphon was greater than the amounts of benzene or cyclohexane adsorbed. Isosteric heats of adsorption and BET cross-sectional areas were calculated for the pure adsorbates on Cab-O-Sil and on Graphon. The data indicated that the three adsorbates do not form close-packed monolayers on the Cab-O-Sil surface. The isosteric heat and the integral entropy of adsorption for ethanol on Graphon suggested that ethanol forms a hydrogen-bonded structure on the Graphon surface. The binary vapor adsorption isotherms were compared to the pure component isotherms. In several instances, the amounts of the components adsorbed from the mixtures were greater than from the pure states. For the Cab-O-Sil systems, selective adsorption of ethanol occurred from ethanol-cyclohexane and ethanol-benzene mixtures; benzene was selectively adsorbed from benzene-cyclohexane mixtures. The adsorbate-vapor composition diagrams for benzene-cyclohexane mixtures on Graphon all contained adsorption azeotropes. Very little selective adsorption of either component occurred. In general, benzene and cyclohexane were selectively adsorbed from benzene-ethanol and cyclohexane-ethanol mixtures on Graphon. Adsorption azeotropes occurred in the 20°C isotherms for these two systems at high ethanol mole fractions. The temperature dependence of the selectivity for the systems studied followed no consistent trend. Comparison of the binary vapor adsorption isotherms with the analogous solution adsorption isotherms indicated that selectivity is generally higher in adsorption from solution. The experimental binary vapor adsorption isotherms were compared to those calculated from the pure vapor adsorption isotherms using the ideal adsorbed solution model. It was found that the adsorbed solutions were ideal or slightly nonideal for all three mixtures on Cab-0-Sil and for benzene-cyclohexane mixtures on Graphon. The nonideal behavior observed for benzene-ethanol and cyclohexane-ethanol mixtures on Graphon was attributed to the presence of benzene or cyclohexane disrupting the hydrogen-bonded structure of ethanol on the Graphon surface. It was concluded that the ideal adsorbed solution model is a useful one for predicting binary vapor adsorption equilibria. / Ph. D.

The finite element method has been demonstrated previously to provide an effective means for the analysis of two dimensional elastic and plastic continua. The method is applied herein to the axially symmetric, solid, and is extended to fracture analysis. The numerical analysis may be broken into three parts. The first involves the role of linear elasticity, the second deals with the elastic-plastic deformations, and the third is concerned with the interaction between such deformation and the fracture process. For the finite solid element method, the crack is thought to initiate below the surface of a notch, approximately in the region of highest triaxiality of the stress σ_ii under the ultimate load, rather than at the root of the notch. Thus the maximum value of σ_ii at ultimate load becomes the assumed criterion for the first phase of the fracture; i.e., the brittle fracture. The crack propagates inward and outward until the octahedral shear stress 𝜏_C, in the remainder of the cross section are above the triaxial stresses. At this stage, the specimen fails in shear and a shear lip forms at the root of the notch, provided it is not exceptionally sharp, and at the inner circumference of the hole of the hollow notched specimens. Thus 𝜏_C becomes the criterion of fracture during this second stage. For the lattice analogy method, the fracture is assumed to progress as each critically stresses member reaches its ultimate and is deleted from the remaining assembly. Both the finite solid element method and the lattice analogy method are used to analyze numerically the solid and hollow notched tensile specimens with the ultimate load held constant during fracture. The finite solid element analysis was also made with this load decreased so as to keep σ_ii and/or 𝜏_C constant at their original maximum values. Comparisons with analytical and exp7rimental results are made and found to be satisfactory. / Ph. D.

Waste sludge is frequently treated by anaerobic digestion to kill pathogens, generate methane gas and reduce odors so the sludge can be safely land applied. In an attempt to reduce sludge volumes and improve sludge dewatering properties, the use of thermal hydrolysis (TH), a sludge pretreatment method, has been adopted by numerous wastewater treatment plants, among them being the District of Columbia Water and Sewage Authority (DC WASA). The use of anaerobic digestion in collaboration with thermal hydrolysis has been shown to increase VS removal, COD removal and biogas production. The sludge generated also dewaters to a higher cake solids than from conventional anaerobic digestion. Unfortunately, DC WASA has found that the use of thermal hydrolysis had brought about two major issues. These are: (a) does thermal hydrolysis increase destruction of fats, oils and greases compared to conventional digestion? and (b) is the mixing method used at Virginia Tech (recirculating gas mixing) capable of stripping ammonia from the digester? Therefore the main purpose of this study is to evaluate these issues which occur with the use of the thermal hydrolysis process. Experiments were conducted in two phases. The first phase was to assess the performance of anaerobic digesters via their biogas production with and without long chain fatty acid addition and with or without thermal hydrolysis. This research was further carried out in two stages. First a mixture of unsaturated long chain fatty acids (hydrolyzed and unhydrolyzed) was used. The fatty acid mixture included oleic, linoleic and linolenic acids, which contain one, two and three double bonds, respectively. In the second stage, the effect of a single unsaturated fatty acid (hydrolyzed and unhydrolyzed) was analyzed. If extra gas is generated, grease addition to the digesters will be implemented. If thermal hydrolysis produces more gas, the greases will be added through the thermal hydrolysis unit rather than being added directly to the digester. The results showed that addition of long chain fatty acids greatly increased gas production and the long chain fatty acids that were thermally hydrolyzed generated more gas than the untreated long chain fatty acids, although the gain was not large. The second phase of the study was carried out by alternating the type of recirculating gas mixing (partial and continuous) in the anaerobic bioreactor. To achieve this goal, short-term anaerobic bioreactor studies were conducted by varying the frequency of the gas. The result showed that continuous gas recirculation at the bottom of the digester was responsible for stripping ammonia from the system. It appeared that up to 500 mg/L of ammonia was being stripped from the digester operating at 20 day solids retention time. This suggests that ammonia can be stripped if a reduction of ammonia in the digester was desired. / Master of Science

By shearing activated sludge using a high shear rotor stator device, bioavailable proteinaceous material can be produced. Operation at elevated temperatures, serves to increase the amount of material that is rendered soluble (<0.45 um) and biodegradable. The storage of sludge under anoxic condition prior to shearing does not appear to enhance solublization of solids, though deflocculation and deterioration of dewaterablility was observed. Anaerobic digestibility appears to be enhanced by the addition of a high shear as shown by increases in gas production and volatile solids destruction. The dewatering properties of activated sludge, measured by capillary suction time, deteriorated with the addition of sheared solids, but reaeration resulted in near complete recovery. The role of iron and iron chemistry plays a critical role in the activated sludge. Iron apparently selectively removes protein, in particular material ranging in the 1.5 um to 30K size range. The addition of ferric iron was found to increase SVI and decrease zone-settling velocity, when added to reactors with mechanically disintegrated sludges. Similar trends were not observed in reactors dosed with ferrous iron. Preliminary results suggest that the ferric/ferrous redox chemistry may serve to enhance floc structure, as observed by increased settling velocity and shear resistance for sludges dosed with ferrous sulfate. / Master of Science

No presente trabalho, efetuamos um extensivo estudo das propriedades eletrônicas e estruturais de nanofios de silcio (Si NWs) utilizando simulações computacionais totalmente ab-initio (metodo do DFT). Mostramos que nestes sistemas, diferentes facetas podem ser eletronicamente ativas ou inativas nos estados de borda dependendo apenas da maneira como os átomos de superfície se ligam aos átomos mais internos. Estes efeitos são causados pelo confinamento quântico nos fios, e por isso podem ser estendidas para outros tipos de fios semicondutores. Nossos resultados podem ser utilizados para guiar o processo de manufatura de sensores baseados em nanofios. Efetuamos cálculos ab-initio de transporte eletrônico nos nanofios com radicais de NH2 adsorvidos em diferentes facetas. Estas análises indicam que há diferenças entre a resposta do sistema a perturbações em superfícies distintas que são eletronicamente ativas. Em certas circunstâncias que serão discutidas, o nível de impureza gera centros espalhadores que reduzem o transporte eletrônico de maneira mais uniforme, enquanto em outros casos as quedas na transmitância são extremamente agudas, com perfil lembrando ressonâncias de fano. Investigamos ainda dopagem de Si NWs com boro e fósforo. Mostramos que estas impurezas se distribuem de maneira razoavelmente uniforme em sítios internos e superficiais dos fios. Embora o confinamento quântico tenda a tornar os níveis de impureza significativamente mais profundos nos fios que no cristal de Si, mostramos que rapidamente, para diâmetros acima de 30°A, dopagem com características de bulke recuperada. Efeitos associados as diferentes superfícies nas quais as impurezas estão localizadas também foram identificados, e acordo com nossas constatações anteriores. Estudamos outra importante impureza em nanofios de Si, que é o ouro, que é utilizado como catalisador no crescimento destes fios. Nossas analises indicam que ha uma forte tendência para estes átomos serem incorporados em sítios superficiais, onde eles não introduzem estados próximos ao gap de energia. Isso indica que ouro pode ser utilizado para catalisar estes fios sem afetar suas propriedades eletrônicas. Por fim analisamos as propriedades eletrônicas de heteroestruturas filiformes de silicio-germânio. Dispositivos eletrônicos baseados nestes materiais têm apresentado propriedades superiores a de equivalentes em arquitetura planar ou mesmo dispositivos baseados em outros nanofios. Nossas análises indicam que estes materiais podem apresentar tão variadas que os tornam candidatos `a diversas implementações tecnológicas, desde detectores de alta sensibilidade e grande liberdade de manipulação até materiais de propriedades eletrônicas robustas e pouco sujeitas a indesejáveis perturbações. / We have performed an extensive study on the electronic and structural properties of silicon nanowires (NWs) using parameter free computational simulations (DFT). We show that in Si NWs, surfaces whose atoms are connected to inner ones perpendicularly to the wires axes become electronically inactive at the band edges. However, when these bonds are oriented along the growth axes the surface states contribute significantly to the formation of the HOMO and LUMO, even for relatively large wires (diameters > 30 °A). This is the dimension of the smallest experimental as-grown wires. These effects are caused by the fact that the electronic wave function is confined in the two directions perpendicular to the wires axes but it is not along it. Therefore, these conclusions can be extended to other types of semiconductor NWs, grown along different directions, with different facets and even surface reconstructions. These results can be used to guide actual implementations of NW based chemical and biological sensors, in a fashion that is now being followed by experimentalists. Following this work, we have investigated the electronic transport in these NWs with a NH2 radical adsorbed on different types of facets. These investigations not only confirm our previous conclusions but also indicate different effects associated with impurities adsorbed on distinct active surfaces. In some cases, the impurity level induces scattering centres that reduce the transport in an uniform way, whereas on other types of facets the decrease in the eletronic transport is sharp, suggesting the occurence of fano resonance.

A diversity of animals move on and bury within dry and wet granular media, such as dry desert sand or rainforest soils. Little is known about the biomechanics and neural control strategies used to move within these complex terrains. Burial and subsurface locomotion provides a particularly interesting behavior in which to study principles of interaction because the entire body becomes surrounded by the granular environment. In this dissertation, we used three model organisms to elucidate control principles of movement within granular substrates: the sand-specialist sandfish lizard which dives into dry sand using limb-ground interactions, and swims subsurface using body undulations; the long-slender shovel-nosed snake which undulates subsurface in dry sand with low slip; and the ocellated skink, a desert generalist which buries into both wet and dry substrates. Using muscle activation measurements we discovered that the sandfish targeted optimal kinematics which maximized forward speed and minimized the mechanical cost of transport. The simplicity of the sandfish body and kinematics coupled with a fluid-like model of the granular media revealed the fundamental mechanism responsible for neuromechanical phase lags, a general timing phenomenon between muscle activation and curvature along the body that has been observed in all undulatory animals that move in a variety of environments. Kinematic experiments revealed that the snake moved subsurface using a similar locomotion strategy as the sandfish, but its long body and low skin friction enabled higher performance (lower slip). The ocellated skink used a different locomotor pattern than observed in the sandfish and snake but that was sufficient for burial into both wet and dry media. Furthermore, the ocellated skink could only reach shallow burial depths in wet compared to dry granular media. We attribute this difference to the higher resistance forces in wet media and hypothesize that the burial efficacy is force-limited. These studies reveal basic locomotor principles of burial and subsurface movement in granular media and demonstrate the impact of environmental interaction in locomotor behavior.