Fluid flow modeling in fractured rocks is a complicated and important research and application topic in many fields such as geological, hydrogeological, environmental and petroleum engineering. Commonly used methods based on equivalent continuum assumption for fluid flow modeling can generally be applied directly to the porous geological media, but have limited applicability when the geological medium is dominated by fractures. It often happens that only limited time, cost, hydrogeological data and computer resources are available in solving a practical problem of the fluid flow modeling in fractured rocks. Therefore, it is a challenge, but necessary, to investigate the hydraulic behaviors and propose new approaches, procedures, and methodologies to build a reliable fluid flow model for fractured rocks with limited available related data. The general concepts on fluid flow modeling in fractured rocks are introduced firstly and the different ways to treat major and minor fractures in 2-D and 3-D discrete fracture fluid flow modeling are propounded. The author has investigated the relations between the hydraulic behaviors and fracture geometry parameters and found out the effect of fracture parameters on the Representative Elementary Volume (REV) for the fracture systems with statistically distributed fracture geometry parameters including the size, orientation and location. Further, a systemic procedure for fluid flow modeling in fractured rocks in two-dimensional domain is suggested and demonstrated through a 2-D case study for groundwater resources evaluation. Six 3-D conceptual linear pipe discrete fracture fluid flow models which focus on the utilization of fracture information are proposed to simulate packer or pumping tests conducted in fractured rock masses. These models can reflect channel flow in fractures, simplify and minimize the complexity of fluid flow in fractures, save computer resources and increase the possibility to solve a field problem at large scales, and implement a discrete fracture fluid flow model easily. Finally, the author has developed a practicable systemic approach to determine the REV for hydraulic properties and then the hydraulic conductivity tensor for the REV in fractured rocks using single well packer test results. These procedures are illustrated through a 3-D case study by implementing the proposed fluid flow models.

The biotransformation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been researched in three situations: batch liquid phase, micro soil slurry reactors, and in-situ studies. A prospective consortium of bacteria found in horse manure was used as the primary source of microorganisms. From this consortium, five major strains were isolated. Serratia marcescens, one of the isolates, was found to be the most effective microorganism at biotransforming RDX in liquid phase. The growth and the biotransformation mechanism of RDX were characterized for both the consortium and Serratia marcescens. The biotransformation of RDX from soil matrices was tested in well-mixed micro soil slurry reactors and in undisturbed in-situ reactors. In the micro soil slurry reactors, carbon sources were varied (nutrient broth and corn steep liquor) and different bacteria were inoculated into the systems which already contained bacteria indigenous to the contaminated soil. There were two distinguishable pathways for the biotransformation of RDX in the soil slurry reactors. Different carbon sources promoted the biotransformation through the pathways differently. The addition of inocula to the systems did not provide any benefit as to the biotransformation rates. In the in-situ studies, a lag period of about 50 days was observed before biotransformation of RDX began. This lag period was believed to be due to mass transfer limitation and adaptation time for the bacteria. Again, adding other inocula to the indigenous bacteria did not provide any benefit towards the rate of biotransformation of RDX. In this study, bacteria indigenous to non-contaminated soil was tested as well and found not to biotransform RDX.

Because of the nature of their processes, semiconductor fabrication facilities use a large amount of water for the processing of microchips. This also means that a large amount of wastewater is discharged from semiconductor facilities. Because of this, there is a drive in the industry towards decreasing water consumption and wastewater discharge by optimizing processes and minimizing water usage, as well as by recycling and reusing wastewaters. The majority of aqueous wastewaters in semiconductor manufacturing come from rinse processes used after chemical baths during cleaning and also from chemical and mechanical planarization processes. This work focuses on the use of biological treatment as a chemical and energy efficient alternative for treating waste streams containing isopropyl alcohol (IPA) and copper. A consortium of bacteria capable of degrading IPA was selected and acclimated. This consortium was immobilized on activated carbon and used as packing for a fluidized-bed reactor. The bioreactor was able to degrade more than 95% of the IPA in the feed stream. In addition, the behavior of the bioreactor system was studied under transient feed conditions by introducing a series of pH and IPA shocks after the reactor had reached steady state. A 5X (500 ppm) step change of IPA in the feed caused the effluent IPA concentration in the reactor to increase ∼12%. After the step change was finished, the reactor quickly recovered to its steady state level. Similarly, a step change decrease in pH of the feed from 7 to 4 caused an ∼11% increase in effluent IPA concentration. A mathematical model based on diffusion and biodegradation of IPA through the biofilm as well as adsorption of IPA on the activated carbon was developed and tested. The model was able to predict the transient changes in IPA feed concentration very well. Finally, building upon the results of previous research studying the biosorption of copper on immobilized cells, a system for the simultaneous removal of IPA and copper was tested experimentally. After acclimation, the system was able to treat effectively a model wastewater containing 100 ppm of IPA and 50 ppm of copper.

<p> Marcellus Shale is one of the world's largest unconventional gas resources. Recent developments in horizontal drilling and hydraulic fracturing enabled efficient and economical extraction of natural gas from unconventional (shale) resources and have led to rapid expansion of natural gas production in the United States. Hydrofracturing generates large volume of flowback and produced water that contains high concentrations of total dissolved solids (TDS), heavy metals, and naturally occurring radioactive materials (NORMs) resulting in significant environmental and public concerns and challenging waste management issues. Ra-226 is the dominant form of NORM and is one of the key challenges for sustainable management of Marcellus Shale wastewater.</p><p> This study is focused on the life cycle of NORMs during natural gas extraction from Marcellus Shale. A rapid method for Ra-226 analysis by inductively coupled plasma mass spectrometry (ICP-MS) was developed to overcome some of the shortcomings of current analytical techniques (e.g., long detection time). The fate of Ra-226 under different scenarios associated with the shale gas extraction, including origin of Ra-226, partitioning in flowback water storage and treatment facilities, and associated solid waste disposal issues were evaluated in this study. This study showed that radium mainly originates from relative rapid shale leaching. High concentration of radium in the Marcellus Shale wastewater can be managed by proper treatment (e.g., sulfate precipitation). However, solid waste generated from treatment facilities or impoundments containing elevated radium concentrations far exceed the limits for disposal in the Resource Conservation and Recovery Act Subtitle D (RCRA-D) landfills. Current practice in landfill management allows the disposal of this solid waste by controlling the Allowed Source Term Loading (ALST) on annual basis. However, if the landfill capacity to accept all the NORM generated from Marcellus Shale gas extraction becomes insufficient, other disposal or beneficial use options for solid waste should be developed. Reuse of radium enriched barite as weighting agent in drilling mud might be a sustainable strategy to reduce the mass of NORM that has to be disposed in the landfills.</p><p> Health risks associated with NORMs were evaluated for several typical scenarios associated with Marcellus Shale gas extraction. Total effective dose equivalent (TEDE) at drilling pads, storage impoundments and landfills are well below the Nuclear Regulatory Commission (NRC) limit for the general public of 100 mrem/yr even under the worst-case scenario assumptions. Workers in the centralized waste treatment facilities might receive excessive TEDE and appropriate measures recommended by NRC should be applied. For example, a safe distance of 5 m is recommended to reduce TEDE to acceptable level. Hence, the key environmental and public health risks associated with NORM brought to the surface by natural gas extraction from Marcellus Shale are from the spills that may contaminate surface and groundwater.</p><p> Overall, this study contributes to the understanding of the fate of NORMs associated with Marcellus Shale gas wastewater management and expands the ability to resolve the environmental concerns associate with NORMs. A novel rapid analytical for Ra-226 measurement by ICP-MS offers an alternative for researchers to quickly analyze environmental samples. The fate of Ra-226 in centralized treatment facilities and storage facilities is important for operators to choose proper management strategy for liquid and solid waste disposal/reuse. The health risk associated with NORM that is assessed in this study will help to resolve the public concern stemming from the high NORM extracted from Marcellus Shale play and provides several options to further reduced its risks.</p>

Real-time control strategies were developed for biological systems requiring exposure to a number of different redox environments. The approach taken was to develop control strategies under static redox conditions, and then merge them into a unified scheme. The anoxic system studied consisted of the removal of oxidized nitrogen by Pseudomonas denitrificans. A control strategy that was based on detecting an inflection point in the transient ORP signal was applied. The inflection point was detected by searching for a minimum in the first derivative. Using this approach, all of the nitrate and nitrite was removed each cycle. Aerobic removal of toluene, performed by Pseudomonas putida, was then studied. In this system, the optimal strategy involved the second derivative of the transient ORP signal, and resulted in toluene removal efficiencies on the order of 95% per cycle. Finally, an attempt was made to automate a process requiring exposure to both anoxic and aerobic environments. In this system, oxidized nitrogen was removed under anoxic conditions, while carbon removal continued under an aerobic environment. Both processes were mediated by Pseudomonas denitrificans. This attempt was only partially successful. While little oxidized nitrogen remained at the end of the anoxic cycle, a significant amount of nitrite reappeared in the medium upon exposure to aerobic conditions. This result served to indicate the importance of the transition zone, and the difficulties associated with controlling sequential environments.

Recycling of bleaching effluents into the black liquor recovery system has become an important step of a closed cycle technology that, in a kraft pulp mill, will result in a reduction in pollutants discharge into receiving waters and also a decrease of fresh water consumption. / In the current work, the combustion of pre-dried solid samples of black liquor (BL), chlorination effluent (C/D), and extraction effluent (E 1) as well as two-component and three-component mixtures was investigated experimentally in a Thermogravimetric Analyzer (TGA) and in a Constant-Temperature Tube Furnace. / Results of the thermogravimetric analyses showed that solids from the C/D stage were similar to those of the black liquor solids in the volatile matter, char, and ash contents, while the solids from the E1 stage contained less volatiles and were richer in their ash content. Results also revealed that both effluents were devolatilized and gasified at lower rates than that of black liquor. The addition of up to 20% of either effluent did not have a significant impact of the TGA behaviour of black liquor. In addition, mixtures containing solids from the three liquors were very close to black liquor in terms of their devolatilization and gasification rates and followed a weight-loss trend similar to that of black liquor. / Effect of temperature, O2, mixing ratio on the chemical compositions of combustion products was investigated in a constant-temperature tube furnace. Chemical analyses of the gaseous and solid phases were performed using a Mass Spectrometer (MS) and an Ion Chromatograph (IC), respectively. Results showed the combustion products of two-component mixtures containing up to 20% of C/D or E1 in black liquor solids would not be significantly different from those of typical black liquor, except that they contained more HCl in the gas phase and larger amounts of chloride in the solid phase, especially when C/D was added. Their amounts were greatly influenced by temperature and oxygen. Combustion of three-component mixtures (BL-C/D-E1) resulted in products very similar to those obtained during the combustion of black liquor alone. The HCl yield was increased with temperature and BL content in the mixture.

Contaminants in aquatic systems tend to associate with particles and colloidal material and their impact on the environment is dependent on the nature and behavior of these carrier particles. This study investigates the role of aggregation and sedimentation in the fate and transport of particles and aggregates. Computational fluid dynamics modeling illustrates the significance of the hydrodynamics of porous aggregates on aggregation. Aggregation numerical modeling incorporating the porous fractal nature of aggregates results in accurate representations of particle size distribution evolutions compared to laboratory experiments. Settling velocities of aggregates that show non-Stoke's like behavior can be modeled taking into consideration the drag coefficient correction and the fractal porous density of the flocs. Applying the new aggregation and sedimentation model to a resuspension event suggests that the risk of exposure to contaminants in the water column is minimal as a consequence of washout and larger settling velocities of porous fractal aggregates.

<p> Seepage barriers have been used extensively to mitigate seepage problems in dams and levees. Although the designs of many of these dams and levees have been based on intact seepage barriers, seepage barriers have been shown to be susceptible to deformation and cracking when high differential hydraulic pressures act across the barrier. Cracking and deformation have also been observed due to thermal expansion and contraction during seepage barrier curing. Under certain conditions, a crack can lead to serious seepage problems, which could potentially lead to the development of a low-resistance seepage pathway. Three scenarios have been identified where there is potential for erosion to occur adjacent to a crack in a barrier: 1) erosion at the interface between a fine-grained soil and a course-grained soil, 2) erosion of overlying soil due to flow along a joint in bedrock, and 3) erosion of the barrier material itself. Previous studies have investigated the first mode of erosion and studies are underway to look into the second mode. The objective of this study is to investigate the third mode of erosion and to identify the conditions under which serious seepage problems can develop. The question considered was whether the combination of highly permeable material adjacent to a crack in a seepage barrier and a large differential head across the barrier combine to develop a velocity within the crack that is erosive to the seepage barrier material. Laboratory tests have been performed on a variety of seepage barrier materials to assess the potential for cracks to develop a preferred seepage path leading to a serious seepage problem. The results of this study will be useful in risk assessment studies of dams and levees with existing seepage barriers as well as in the design of new seepage barriers. Having knowledge of the conditions under which problems may occur will aid in the selection of seepage barrier types for new barriers, placement of instrumentation to monitor new and existing barriers, and mitigation of existing barriers where problems have been identified. The data provided will assist engineers in quantitatively assessing the potential for the propagation of critical seepage problems from cracks in seepage barriers. </p>

Aquifer flow-through columns were operated for 12 weeks to evaluate the benefits of oxygen addition on the biodegradation of a Chlroboenzene (CB) DNAPL source zone. Quantitative PCR was used to measure total bacteria (16S rDNA) and several aromatic oxygenase genes. CB removal was faster in the oxygen-amended columns compared to a control column, and qPCR showed that whereas the biphenyl and toluene dioxygenase biomarkers were most abundant, increases in the biomarker concentration for the phenol hydroxylase gene reflected best the higher CB removal due to aerobic biostimulation. DGGE analyses of the soil amended with oxygen revealed the dominant presence of Rhodococcus erythropolis (89% sequence similarity), which belongs to a genus known for its ability to degrade many priority pollutants, including CBs.

Arsenic has become a major contaminant of concern due to the increased knowledge of its toxicological and carcinogenic effects on human health, causing the maximum contaminant level (MCL) to be lowered from 50mug/L to 10mug/L in the United States. Lowering the MCL requires improving current methods or developing new ones to remove arsenic from the drinking water. Currently, there are many methods to remove arsenic, such as coagulation iron salts, ion exchange, and membranes. These methods can be expensive, have poor removal efficiency, and produce a large amount of waste. In this research, magnetite nanoparticles are evaluated as arsenic sorbents due to there magnetic properties for removal, minimal production of waste, and high surface area. Also, in this work, the kinetics of adsorption was examined along with the competitive adsorption of other ions (chloride, phosphate, sulfate, silica, and bicarbonate) in solution. Equilibrium was reached in about two hours for arsenate and arsenite; however, approximately 90% of the arsenate and arsenite was adsorbed within thirty minutes with 0.5g/L Fe3O4. The arsenate and arsenite equilibrium concentrations are similar which demonstrates the affinity of magnetite nanoparticles for both arsenite and arsenate. This work presents a model which predicts the amount of arsenic adsorbed by magnetite nanoparticles in the presence of several ions using a modified rate equation. To test the viability this arsenic removal method, it was tested on spiked arsenic tap water and arsenic contaminated groundwater from Brownsville, TX. In each case, the treatment goal of less than 10mug/L was reached with minimum residual iron in the water. Therefore, these results suggest that using magnetite nanoparticles is a feasible process to remove arsenic from the drinking water. This process could be applied as a household treatment system for developing and developed countries.