Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation

Hydrogen as an Indicator to Assess Biological Activity During Trace-Metal Bioremediation

Date: September 27, 2005
Creator: Peter R. Jaffe, John Komlos, Derick Brown
Description: Trace-metal and/or radionuclide bioremediation schemes require that specific redox conditions be achieved at given zones of an aquifer. Tools are therefore needed to identify the terminal electron acceptor processes (TEAPs) that are being achieved during bioremediation in an aquifer. Dissolved hydrogen (H2) concentrations have been shown to correlate with specific TEAPs during bioremediation in an aquifer. Theoretical analysis has shown that these steady-state H2 levels are solely dependent upon the physiological parameters of the hydrogen-consuming microorganisms, with H2 concentrations increasing as each successive TEAP yields less energy for bacterial growth. The objective of this research was to determine if H2 can still be used as an indicator of TEAPs during a uranium bioremediation scheme where an organic substrate is injected into the subsurface and organisms may consume H2 and carbon simultaneously. In addition, the effect of iron bioavailability on H2 concentrations during iron reduction was observed. The first phase of research determined the effect of a competing electron donor (acetate) on the kinetics of H2 utilization by Geobacter sulfurreducens in batch cultures under iron reducing conditions. The results indicate that, though the Monod kinetic coefficients describing the rate of H2 utilization under iron-reducing conditions correlate energetically with the coefficients found ...
Contributing Partner: UNT Libraries Government Documents Department
Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination Processes

Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination Processes

Date: December 13, 2005
Creator: Myneni, Satish C. B.
Description: Siderophores are biological macromolecules (400-2000 Da) released by bacteria in iron limiting situations to sequester Fe from iron oxyhydroxides and silicates in the natural environment. These molecules contain hydroxamate and phenolate functional groups, and exhibit very high affinity for Fe{sup 3+}. While several studies were conducted to understand the behavior of siderophores and their application to the metal sequestration and mineral dissolution, only a few of them have examined the molecular structure of siderophores and their interactions with metals and mineral surfaces in aqueous solutions. Improved understanding of the chemical state of different functional moieties in siderophores can assist in the application of these biological molecules in actinide separation, sequestration and decontamination processes. The focus of our research group is to evaluate the (a) functional group chemistry of selected siderophores and their metal complexes in aqueous solutions, and (b) the nature of siderophore interactions at the mineral-water interfaces. We selected desferrioxamine B (desB), a hydroxamate siderophore, and its small structural analogue, acetohydroxamic acid (aHa), for this investigation. We examined the functional group chemistry of these molecules as a function of pH, and their complexation with aqueous and solid phase Fe(III). For solid phase Fe, we synthesized all naturally occurring Fe(III)-oxyhydroxides ...
Contributing Partner: UNT Libraries Government Documents Department
Trace Metal Bioremediation: Assessment of Model Components from Laboratory and Field Studies to Identify Critical Variables

Trace Metal Bioremediation: Assessment of Model Components from Laboratory and Field Studies to Identify Critical Variables

Date: February 14, 2003
Creator: Jaffe, Peter & Rabitz, Herschel
Description: The objective of this project was to gain an insight into the modeling support needed for the understanding, design, and operation of trace metal/radionuclide bioremediation. To achieve this objective, a workshop was convened to discuss the elements such a model should contain. A ''protomodel'' was developed, based on the recommendations of the workshop, and was used to perform sensitivity analysis as well as some preliminary simulations in support for bioremediation test experiments at UMTRA sites. To simulate the numerous biogeochemical processes that will occur during the bioremediation of uranium contaminated aquifers, a time-dependent one-dimensional reactive transport model has been developed. The model consists of a set of coupled, steady state mass balance equations, accounting for advection, diffusion, dispersion, and a kinetic formulation of the transformations affecting an organic substrate, electron acceptors, corresponding reduced species, and uranium. This set of equations is solved numerically, using a finite element scheme. The redox conditions of the domain are characterized by estimating the pE, based on the concentrations of the dominant terminal electron acceptor and its corresponding reduced specie. This pE and the concentrations of relevant species are passed to a modified version of MINTEQA2, which calculates the speciation and solubilities of the species ...
Contributing Partner: UNT Libraries Government Documents Department
Enhancement of Bacterial Transport in Aerobic and Anaerobic Environments: Assessing the Effect of Metal Oxide Chemical Heterogeneities

Enhancement of Bacterial Transport in Aerobic and Anaerobic Environments: Assessing the Effect of Metal Oxide Chemical Heterogeneities

Date: September 30, 2005
Creator: Onstott, T.C.
Description: The goal of our research was to understand the fundamental processes that control microbial transport in physically and chemically heterogeneous aquifers and from this enhanced understanding determine the requirements for successful, field-scale delivery of microorganisms to metal contaminated subsurface sites. Our specific research goals were to determine; (1) the circumstances under which the preferential adsorption of bacteria to Fe, Mn, and Al oxyhydroxides influences field-scale bacterial transport, (2) the extent to which the adhesion properties of bacterial cells affect field-scale bacterial transport, (3) whether microbial Fe(III) reduction can enhance field-scale transport of Fe reducing bacteria (IRB) and other microorganisms and (4) the effect of field-scale physical and chemical heterogeneity on all three processes. Some of the spin-offs from this basic research that can improve biostimulation and bioaugmentation remediation efforts at contaminated DOE sites have included; (1) new bacterial tracking tools for viable bacteria; (2) an integrated protocol which combines subsurface characterization, laboratory-scale experimentation, and scale-up techniques to accurately predict field-scale bacterial transport; and (3) innovative and inexpensive field equipment and methods that can be employed to enhance Fe(III) reduction and microbial transport and to target microbial deposition under both aerobic and anaerobic conditions.
Contributing Partner: UNT Libraries Government Documents Department
CONCEPTUAL DESIGN OF OPTIMIZED FOSSIL ENERGY SYSTEMS WITH CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE

CONCEPTUAL DESIGN OF OPTIMIZED FOSSIL ENERGY SYSTEMS WITH CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE

Date: June 26, 2003
Creator: Ogden, Joan M.
Description: In this semi-annual progress report, we describe research results from an ongoing study of fossil hydrogen energy systems with CO{sub 2} sequestration. This work was performed under NETL Award No. DE-FC26-02NT41623, during the six-month period September 2002 through March 2003. The primary objective of the study is to better understand system design issues and economics for a large-scale fossil energy system co-producing H{sub 2} and electricity with CO{sub 2} sequestration. This is accomplished by developing analytic and simulation methods for studying the entire system in an integrated way. We examine the relationships among the different parts of a hydrogen energy system, and attempt to identify which variables are the most important in determining both the disposal cost of CO{sub 2} and the delivered cost of H{sub 2}. A second objective is to examine possible transition strategies from today's energy system toward one based on fossil-derived H{sub 2} and electricity with CO{sub 2} sequestration. We are carrying out a geographically specific case study of development of a fossil H{sub 2} system with CO{sub 2} sequestration, for the Midwestern United States, where there is presently substantial coal conversion capacity in place, coal resources are plentiful and potential sequestration sites in deep saline ...
Contributing Partner: UNT Libraries Government Documents Department
COARSE-GRID SIMULATION OF REACTING AND NON-REACTING GAS-PARTICLE FLOWS

COARSE-GRID SIMULATION OF REACTING AND NON-REACTING GAS-PARTICLE FLOWS

Date: October 1, 2004
Creator: Sundaresan, Sankaran
Description: Many processes involved in coal utilization involve handling of fine particles, their pneumatic transport, and their reactions in fluidized beds, spouted beds and circulating fluidized beds. One of the factors limiting our ability to simulate these processes is the hydrodynamics encountered in them. Two major issues that contribute to this limitation are lack of good and computationally expedient models for frictional interaction between particles, and models to capture the consequences of mesoscale structures that are ubiquitous in gas-solid flows. This project has focused on the development of these models through a combination of computer simulations and experiments. The principal goal of this project, funded under the ''DOE Vision 21 Virtual Demonstration Initiative'' is better simulation of circulating fluidized bed performance. The principal challenge funded through this cooperative agreement is to devise sound physical models for the rheological characteristics of the gas-particle mixtures and implement them in the open-domain CFD code MFIX. During the course of this project, we have made the following specific advances. (a) We have demonstrated unequivocally that sub-grid models are essential to capture, even qualitatively correctly, the macroscale flow structures in gas-particle flows in vertical risers. To this end, we developed sub-grid models of different levels of ...
Contributing Partner: UNT Libraries Government Documents Department
Precipitation and Deposition of Aluminum-Containing Phases in Tank Wastes

Precipitation and Deposition of Aluminum-Containing Phases in Tank Wastes

Date: January 12, 2005
Creator: Dabbs, Daniel M. & Aksay, Ilhan A.
Description: Aluminum-containing phases compose the bulk of solids precipitating during the processing of radioactive tank wastes. Processes designed to minimize the volume of high-level waste through conversion to glassy phases require transporting waste solutions near-saturated with aluminum-containing species from holding tank to processing center. The uncontrolled precipitation within transfer lines results in clogged pipes and lines and fouled ion exchangers, with the potential to shut down processing operations.
Contributing Partner: UNT Libraries Government Documents Department
CONCEPTUAL DESIGN OF OPTIMIZED FOSSIL ENERGY SYSTEMS WITH CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE

CONCEPTUAL DESIGN OF OPTIMIZED FOSSIL ENERGY SYSTEMS WITH CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE

Date: May 1, 2004
Creator: Ogden, Joan M.
Description: In this third semi-annual progress report, we describe research results from an ongoing study of fossil hydrogen energy systems with CO{sub 2} sequestration. This work was performed under NETL Award No. DE-FC26-02NT41623, during the six-month period September 2003 through March 2004. The primary objective of the study is to better understand system design issues and economics for a large-scale fossil energy system co-producing H{sub 2} and electricity with CO{sub 2} sequestration. This is accomplished by developing analytic and simulation methods for studying the entire system in an integrated way. We examine the relationships among the different parts of a hydrogen energy system, and attempt to identify which variables are the most important in determining both the disposal cost of CO{sub 2} and the delivered cost of H{sub 2}. A second objective is to examine possible transition strategies from today's energy system toward one based on fossil-derived H{sub 2} and electricity with CO{sub 2} sequestration. We are carrying out a geographically specific case study of development of a fossil H{sub 2} system with CO{sub 2} sequestration, for the Midwestern United States, where there is presently substantial coal conversion capacity in place, coal resources are plentiful and potential sequestration sites in deep ...
Contributing Partner: UNT Libraries Government Documents Department
CONCEPTUAL DESIGN OF OPTIMIZED FOSSIL ENERGY SYSTEMS WITH CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE

CONCEPTUAL DESIGN OF OPTIMIZED FOSSIL ENERGY SYSTEMS WITH CAPTURE AND SEQUESTRATION OF CARBON DIOXIDE

Date: December 1, 2003
Creator: Ogden, Joan M.
Description: In this second semi-annual progress report, we describe research results from an ongoing study of fossil hydrogen energy systems with CO{sub 2} sequestration. This work was performed under NETL Award No. DE-FC26-02NT41623, during the six-month period March 2003 through September 2003. The primary objective of the study is to better understand system design issues and economics for a large-scale fossil energy system co-producing H{sub 2} and electricity with CO{sub 2} sequestration. This is accomplished by developing analytic and simulation methods for studying the entire system in an integrated way. We examine the relationships among the different parts of a hydrogen energy system, and attempt to identify which variables are the most important in determining both the disposal cost of CO{sub 2} and the delivered cost of H{sub 2}. A second objective is to examine possible transition strategies from today's energy system toward one based on fossil-derived H{sub 2} and electricity with CO{sub 2} sequestration. We are carrying out a geographically specific case study of development of a fossil H{sub 2} system with CO{sub 2} sequestration, for the Midwestern United States, where there is presently substantial coal conversion capacity in place, coal resources are plentiful and potential sequestration sites in deep ...
Contributing Partner: UNT Libraries Government Documents Department
Studies in Chemical Dynamics

Studies in Chemical Dynamics

Date: June 27, 2003
Creator: Rabitz, Herschel & Ho, Tak-San
Description: This final report draws together the research carried from February, 1986 through January, 2003 concerning a series of topics in chemical dynamics. The specific areas of study include molecular collisions, chemical kinetics, data inversion to extract potential energy surfaces, and model reduction of complex kinetic systems.
Contributing Partner: UNT Libraries Government Documents Department
FIRST PREV 1 2 3 NEXT LAST