A 3-D seismic reflection survey was conducted at a groundwater contamination site to adequately image the near surface (<20m) at a level of detail to enhance ongoing remediation activities at the site. The site, Operable Unit 2 (OU2), located at Hill Air Force Base in Ogden, Utah has been the subject of a continuing effort to remove dense nonaqueous phase liquids (DNAPLs), solvents and degreasers, which had been dumped into trenches at the site for eight years. Subsurface maps of the near surface geology, based solely on data from the over 200 monitoring wells drilled at the site, do not provide sufficient detail of subsurface features that trap these contaminants to conduct site remediation in a cost-effective manner. The target geologic feature for remediation, a paleochannel complex, under a surface layer of unconsolidated sands, silts and gravels, cut into a thick layer of clay. The paleochannel traps both groundwater and contaminants. The paleochannel was the focus of an earlier 2-D survey, demonstrating the viability of the site for seismic methods. Successfully imaging the channel profile in three places, results from the 2-D survey served as a testbed for planning for the 3-D survey. The 3-D reflection survey covered an area of 37 x 95m centered over the paleochannel. After data processing, the resulting seismic volume shows a paleochannel complex with two channels from the north merging into a single channel that spreads out across the southern portion of the survey. Intersecting the channel are two displacement surfaces, origins unknown, disrupting channel flow and altering the pattern of erosion and deposition. The resulting map shows the channel complex with depth to base clay varying from 6 to 18.33m. Vertical resolution of the depth-to-clay map is 1.25m (lambda/2). Stratigraphic analysis of the sedimentary package above the interpreted clay surface confirms the seismic interpretation. Comparison with results from a tomographic study (Azaria, 2003) and a VSP study (Gao et al., 2003) at the site confirm the reflection survey results.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation).

Two often used permeability models, which are based on logarithmic mean of relaxation time distribution and irreducible water, were examined. The model based on irreducible water was found to be more suitable than the model based on mean value of relaxation time distribution when oil is present. The NMR response of North Burbank with partial saturation of air and water is different from those of other sandstones. The increase in the amplitude of the microporosity part of the relaxation time distribution after desaturation was observed for North Burbank. The clay lining a pore is diffusionally coupled with the large pores when 100% water saturated. After desaturation with air, the water in the microchannel is isolated and relaxes like water in an isolated micropore. It is generally believed that when the rock is water-wet, there is tendency for water to occupy the small pores and contact the majority of the rock surface. Water is typically relaxed by contact with grain surface, but oil at the center of the pore has no access to these surfaces and therefore can only relax by bulk processes. According to this study, $T\sb1$ distributions under partial saturation with brine/Soltrol followed the above behavior. However, for $T\sb2$ distributions, we found the Soltrol peaks for chlorite-coated North Burbank and highly shaly sandstones were broadened and shortened to shorter relaxation times due to diffusion and internal gradients effects. The diffusion effect can be supported by the same observation in 100% S$\rm\sb{w}$ condition. This suggests even if oil is prevented from contacting the grain surface, oil will not necessarily relax as a bulk oil in water-wet system.

The influence of electron donors on the ability to sustain tetrachloroethene (PCE) dechlorination was investigated in recycle columns containing a PCE-dechlorinating mixed culture. Over a period exceeding one year, it was demonstrated that equivalent amounts of lactate, methanol, and hydrogen could sustain rate and extent of dechlorination equally. Dechlorination was not impacted by competition for electron donor at high hydrogen partial pressures, despite the presence of an actively methanogenic community. Results from these experiments imply that cost and method of delivery may dictate electron donor selection for stimulation of anaerobic in situ dechlorination. Efforts to isolate PCE-dechlorinating organisms from the mixed culture resulted in the development of a highly purified co-culture that dechlorinated PCE to cis-dichloroethene and was dominated by curved, motile rods and cocci. Preliminary molecular biology techniques were employed to characterize the ecology of the purified culture. It was discovered that multiple microorganisms, one of which shared 98% 16S rDNA sequence identity with the fermentative coccus, Lactosphaera pasteurii, were present. Experiments characterizing the nutritional requirements of the purified coculture determined dechlorination sustainment required the addition of filter-sterilized cell extract prepared from the parent mixed culture. It was determined that hydrogen, pyruvate, glucose, ethanol, and yeast extract could sustain dechlorination, while formate, acetate, acetaldehyde, lactate, propionate, butyrate, and methanol could not. Experiments to determine the effect of dechlorination on the longevity and composition of PCE-containing NAPLs were conducted in continuous-flow stirred-tank reactors (CFSTRs). Comparisons between biotic and abiotic CFSTRs demonstrated that dechlorination resulted in a factor of 14 increase in PCE removal rates from the NAPL. Dechlorination daughter products partitioned between the aqueous and NAPL phases, resulting in temporal changes in NAPL composition. The combined effects of dissolution and dechlorination on the removal of chlorinated ethenes from the NAPL were described using a mathematical model that approximated dechlorination as a pseudo first-order process. It was determined that total chlorinated ethenes removal from the NAPL would be achieved in 13 days in the biotic CFSTRs, as compared to 77 days in the abiotic CFSTRs---corresponding to an 83% reduction in the longevity of the chlorinated ethenes component of the NAPL.

Unique genetic modifications to C. acetobutylicum altered the level of hydrogenase expression, allowing study of the resulting effects on the 2,4,6-trinitrotoluene (TNT) reduction rates to be possible. A strain designed to over-express the hydrogenase gene resulted in maintained TNT reduction during late growth phases when it is not typically observed. Strains exhibiting under-expression of hydrogenase produced slower TNT rates of reduction correlating to the expected inhibition of each strain type. Hydrogenase activity, measured by hydrogen production, in Clostridium acetobutylicum correlates strongly (R2 = 0.89) to TNT reduction rates. Indications suggested that hydrogenase potentially played an integral role in catalysis of TNT transformation by reducing its nitro substituents to the corresponding hydroxylamines. A mechanistic pathway is proposed by which this transformation takes place and may enhance the understanding of commonly found hydrogenases in other microorganisms and their ability to transform nitroaromatic compounds.

This thesis develops and applies seismic waveform tomography to solve the unique problem of imaging complicated shallow sub-structures with high resolution. Shallow sub-structures are commonly characterized by seismic reflection/refraction imaging, georadar and seismic travel time tomography (e.g., Steeples, 1998; Carcione et al., 2000 and Azaria, 2002). Their resolving power or applicability is often limited. In contrast, waveform tomography, a full wave field inversion technique, resolves sub-structures at a resolution that is a fraction of the illuminating wavelengths. Forward modeling in waveform tomography is based on a finite difference solution to the acoustic wave equation in the space-frequency domain. During inversion for model parameters, the technique efficiently calculates the gradient of a misfit function with respect to model parameters by correlating back-propagated and forward modeled wave fields, avoiding the forbidding task of explicitly computing Frechet kernels. Part of this study compares travel time and waveform tomography in a synthetic cross-well test. The two tomographic approaches are found to be complementary if data contains no significant low frequency spectra. I then apply waveform tomography to two datasets from a ground water contamination site at the Hill Air Force Base (HAFB) to sample formation heterogeneities and to map the 3D geometry of a buried paleo-channel where DNAPLs (Dense Non-Aqueous Phase Liquids) were dumped. The first is a VSP-surface seismic experiment. The final velocity model from waveform tomography applied to the VSP dataset generally correlates well with lithology logs, depth migrated 2D/3D reflection data and a velocity model from 3D travel time tomography. Large velocity variations vertically and laterally (200m/s) occur in a distance as short as ∼1m. The model is interpreted geologically and petrologically. Scale features down to ∼1.5m were recovered. I then apply waveform tomography to 45 2D seismic profiles extracted from a 3-D surface seismic experiment at HAFB, and recover the 3D geometry of a buried paleo-channel acting as a trap for DNAPLs. By combining the identified cross-sectional geometry, the 3D geometry of the channel is reconstructed. The subsurface map could be used to plan injection/extraction well placements with good precision and low cost in the on-going ground water remediation program.

Two new methods for the fabrication of porous membranes were studied. Ceramic membranes were obtained from alumoxane and ferroxane nanoparticles casted onto porous support materials. The synthesis of ferroxane nanoparticles was further investigated, in particular the kinetics of the reaction and the structure of the materials obtained by particle size measurements and EXAFS. The ceramics were characterized by nitrogen absorption isotherms, scanning electron microscope, and atomic force microscope. The permeability and molecular weight cut off (MWCO) of the ferroxane derived membranes were measured. These membranes have an average pore size of 24 run and a MWCO of 180,000 Daltons, which corresponds to the ultrafiltration range. The ferroxane nanoparticles were reacted with compounds containing other metallic atoms and mixed metal oxide nanoparticles were obtained. The nanoparticles can be applied to the fabrication of mixed metal oxide ceramics used in catalysis, fuel cells and other applications. The conductivity and surface acidity were determined in order to evaluate these materials as possible proton exchange membranes for fuel cells. The second fabrication method considered in this study is the template-derived process. Deposits of silica nanoparticles of variable morphology were prepared to be used as templates for porous membranes. The variables that control the morphology of the deposits were investigated, in particular those related to the solvent chemistry of the nanoparticle suspensions. The templates were obtained by self-assembly and Langmuir-Blodgett layer-by-layer deposition. By controlling the template deposition process, the self-assembly method was used to create dendritic templates with an asymmetric structure. The Langmuir-Blodgett technique was used to create bilayers of different pore size. Polystyrene membranes were fabricated as replicas of these template structures. The pore structure of the polymeric membranes was studied by scanning electron microscopy.

A high rate tetrachloroethene (PCE) dechlorinating culture was enriched under methanogenic conditions that was able to dechlorinate 86 mg/L PCE to cis-1,2-DCE and vinyl chloride within 15 hours. In subsequent studies, the influence of electron donor on the ability to sustain PCE dechlorination was investigated in upflow columns inoculated with either the PCE enrichment culture or a (1:1) mixture of the enrichment culture and soil from contaminated field sites. One column from each inoculum subset was fed 34 milliequivalents of lactate, methanol, or hydrogen as electron donor and 5 mg/L PCE every four days. PCE was dechlorinated to primarily vinyl chloride in all six columns. Rates of PCE dechlorination were found to be similar with regard to inoculum, and did not vary extensively between electron donors. High hydrogen partial pressures were not found to be inhibitory to dechlorination.

A generalized model is formulated to predict the time-dependent permeate flux by extending previous models to include the particle transport mechanisms of Brownian diffusion, shear-induced diffusion, inertial lift and concentrated flowing layers. A new model for estimating the capital costs of membrane plants is developed which incorporates individual cost correlations for different categories of manufactured equipment. The effects of particle size, design, and operating variables on permeate flux and treatment costs are investigated numerically. Optimization problems are formulated and solved to investigate (a) optimal membrane design and system operation, (b) optimal backflushing frequency, and (c) optimal selection of hybrid filtration configurations, over variable raw water quality. The combined theory predicts an unfavorable particle size, on the order of 10$\sp{-1}\ \mu$m, where net back-transport is at a minimum. This implies minimum permeate fluxes in the size range of 10$\sp{-2}\ \mu$m - 10$\sp{-1}\ \mu$m, depending on the operating time. These results support experimental observations of minima in back-transport (Chellam and Wiesner, 1996) and permeate flux (Fane, 1984). Inside-out hollow fiber geometry is predicted to be favorable for feed suspensions with small particles and/or low concentrations. The constant pressure mode of operation is predicted to yield higher specific permeate fluxes compared to the constant flux mode, particularly for particles which demonstrate mass-transfer limited behavior. Comparisons and parameter estimations made with available experimental data on polydisperse suspensions give solidosity estimates ranging from 0.70 to 0.77. Membrane design is predicted to be optimized at values of fiber radius (narrow) and length (short) where the permeate fluxes are maximized. Particles affected by mass-transport limitations demonstrate comparatively lower optimal transmembrane pressures. For unfavorable particles, treatment costs are predicted to be minimized at intermediate recoveries and backflushing frequencies. At small capacities, the hybrid hollow fiber ultrafiltration and spiral wound nanofiltration system with higher non-membrane capital costs is predicted to be largely non-optimal compared to hollow fiber nanofiltration. Membrane costs are expected to play a significant role in determining the optimal configuration at large capacities, where the hybrid configuration is predicted to become largely optimal.

The rapid urbanization of Asia in recent years has radically transformed cities through the incessant barrage of the man-made into the natural. These immense changes are particularly evident in the nation of Singapore where for decades, modernization, urban renewal and industrialization have been the primary objectives of the governing authority. Lying in its wake however, are a series environmental consequences, the results of which are far-reaching and have only recently been addressed. The Singapore River has through the years suffered such a fate. Once teeming with aquatic life, the river now lays still, healing silently. And while the authorities have since then embarked on major cleaning programs, pollution till today, remains a problem and marine life an uncertainty. The thesis proposes the introduction of a suite of bridges, a sequence of filtering devices which through serving the purpose of connecting the banks of the river, incorporate secondary functions--cultural, educational or recreational, following the course of the river, addressing the varying conditions along the edges in the attempt to create a new engagement between water and the edge, nature and the city.

The deposition of material that has precipitated out of solution can cause problems that plague a variety of engineering and biological processes. Scale formation in cooling towers, boilers, and oil/gas operations are prevented with chemical inhibitors such as nitrilotris (methylene phosphonic acid). The release of this phosphonate from solid material is studied with batch and dynamic flow experiments. The corresponding observations can be incorporated into SqueezeSoft(TM), a computer program, written by the Rice University Brine Chemistry Consortium. This work attempts to examine SqueezeSoft(TM)'s ability to identify the placement of inhibitor during a squeeze treatment and the corresponding reactions that occur. SqueezeSoft(TM) has been found to correctly predict the profile of inhibitor injected into a column packed with core material. Because this program is based on theory and not on empirical findings, it can be expanded to other more general applications.