Browsing by Subject "Filters and filtration"
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Item Artificial recharge of playa water through filter drains(Texas Tech University, 1988-05) Wong, Twee ChingNOT AVAILABLEItem Biodegradation of paint VOC mixtures in biofilters(2004) Park, Jung Su; Kinney, Kerry A.The surface coating industry is facing increasingly stringent environmental regulations that require the control of volatile organic compounds (VOCs) and hazardous air pollutants. Biofiltration is an attractive alternative for paint spray booth applications but these facilities pose several challenges to biofiltration technology . Specifically, offgas streams from painting operations are characterized by complex VOC mixtures, frequent shutdown and restart events, high volumetric flow rates, and relatively low contaminant concentrations. The objectives of this research were to investigate the feasibility of biofiltration for paint spray booth applications and to delineate how key operating parameters and biofilter history affect the degradation of VOC mixtures and the microbial population in biofilters. The results indicate that biofilters are a feasible option for treating the emissions from paint spray booth facilities. Removal efficiencies as high as 95% or greater were achieved even under intermittent feed conditions. Biofilter performance was found to strongly depend on nitrogen supply, particularly during the start up period. Overall VOC removal was limited by the toluene and xylene components of the waste gas stream. When the inoculating culture was developed so as to maintain the degradation capacity of the culture for each VOC component of the paint mixture, a sequential feeding strategy did not provide any initial advantage with respect to VOC removal; however, the system ultimately achieved higher removals of the toluene. Biofilm samples analyzed using the DGGE technique indicate that the fungal population in the bioreactors was relatively uniform across the biofilters and stable over extended periods of operation. The DGGE banding pattern for the bacterial population, on the other hand, indicates that the bacterial community was spatially distinct and became less diverse after 200 days of operation. While this research focused on biofilters treating paint VOC mixtures, it is anticipated that many of the phenomena observed will be applicable to other bioreactor systems and contaminant mixtures.Item Development of nanofiber protective substrates(Texas Tech University, 2004-08) Subbiah, ThandavamoorthyElectrospinning uses high voltage electric field to produce high surface area fibers in the nanometer range. Polymeric nanofibers were prepared by the electrospinning process and were characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). A study on the relationship between process parameters and fiber characteristics was undertaken. The dependence of fiber morphology on the solvent volatility and collector substrate characteristics was critically analyzed. Results on the self assembling nature of the charged fibers over different collector substrates were obtained and reported in the thesis. Defect free nanofiber webs with high specific surface area and low porosities suitable enough to be used as adsorptive filtration membranes were prepared. Polyurethane nanofibers were used as nano metal oxide catalyst carriers by successfully impregnating the catalyst in a single-step electrospinning process. Aerosol filtration abilities of nanofiber membranes were tested and the results are presented.Item Linking gene expression to performance in a fungal vapor-phase bioreactor treating ethylbenzene(2004) Gunsch, Claudia Kneller; Kinney, Kerry A.Item The optimal use of enhanced oil recovery polymers under hostile conditions(2009-05) Levitt, David Benjamin, 1980-; Pope, G. A.The purpose of this work is to frame the main issues one must face in the design of a mobility control process using polyacrylamide and related acrylic polymers under hostile conditions. Proper preliminary lab evaluation techniques, chemical degradation and related calcium tolerance issues, thermal degradation, and economic optimization based upon injectivity are discussed. Emphasis is placed on stability under alkaline conditions, the use of sodium dithionite to prevent thermal degradation, and the beneficial use of in-situ hydrolysis to increase injectivity. Filtration properties are a focus of screening experiments, and though it often takes several days to achieve acceptable filter ratios in the lab, experience from two field observations indicate that even high molecular weight polymers have filtration ratios on the order of 1.2 or less before they are injected, so preparation procedures that do not result in this may not yield results that scale to the field. Chemical stability issues with acrylamide polymers are addressed in two parts, the first describing the kinetics of hydrolysis under neutral and alkaline conditions and the second estimating the calcium tolerance of aged polymers using industrial and lab produced analogues. Under alkaline conditions, hydrolysis is very rapid, even at low temperatures. Though aged copolymers of acrylamide (AM) and 2-acrylamide 2-methyl propane sulfonate (AMPS) exhibit similar calcium tolerances to similarly aged polyacrylamide (PAM), viscosity loss is much higher for the latter as this limit is approached. Thermal, or "oxidative" degradation, is examined using Pourbaix diagrams for iron to understand the commonly reported relationships between pH, Eh, and stability. The beneficial effects of sodium carbonate and sodium dithionite on polymer solutions as well as some inconsistencies in the literature point towards a catalytic role played by ppb level amounts of iron in oxidative degradation mechanisms. It is put forward that addition of sodium dithionite is a conservative approach to all acrylic-backboned polymer floods, and practical issues related to this are discussed. A simple analytical model is developed to take a brief look at economic optimization of polymer viscosity, and this is used to demonstrate the benefits of in-situ hydrolysis in alkaline or high-temperature floods.