Browsing by Subject "Soil pollution"
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Item Electrode-assisted soil washing(Texas Tech University, 1993-12) Krishnan, RameshSoil contamination has become a serious problem and has attracted much attention in the United States. In most cases the necessity to clean contaminated soil arises from a threat to our underground drinking water supply. There are many alternatives to solving this problem. One of the most viable alternatives for cleaning contaminated soil is Soil Washing. The state-of-the-art soil washing technologies are effective in cleaning large-grained soils (sands and coarse silts), but are ineffective with fine-grained soils (fine silts and flocculated clays). Usually, for successful soil washing, the soil should contain less than 25% of clays and silts. An innovative soil washing technology has been experimentally demonstrated, at the Chemical Engineering Department of the Texas Tech University, to clean contaminated soils that contain a very high percentage of fines (silts and flocculated clays). This technology is called the Electrode Assisted Soil Washing (EASW) technology. The laboratory scale EASW device has proved successful in washing contaminated soils carrying a greater percentage of fine silts and clays. The primary contaminants used to test the EASW device are a straight-run diesel fraction from the Fina refinery at Big Spring, Texas, and 26.2 API crude oil. The soil, these contaminants were tested on, is Lubbock top soil. To further strengthen the credibility of the EASW technology, authentic contaminated soils from the "real world" were washed successfully. Soils from the Gulf Coast and from an old petroleum product loading terminal in New Jersey were washed to below 100 ppm of the contaminant on the soil. A formal patent search has been made regarding the EASW process and no prior art was found. On this basis, a formal patent application has been filed and is pending, for the invention of the EASW process.Item Fate of perchlorate in natural systems: intrinsic biodegradation, plant uptake, and remediation potential of wetlands(Texas Tech University, 2003-08) Tan, KuiPerchlorate (CIO4) has recently become a nationwide concern due to contamination in soil, sediment, surface water, and groundwater. Laboratory and field studies were initiated (1) to examine the potential of wetland systems to treat perchloratecontaminated waters, (2) to determine the intrinsic degradation kinetics in sediments and soils from multiple sites, and (3) to determine the fate of perchlorate in streams and near-surface sediments, including temporal and spatial distribution, plant uptake, and biological transformation potential. Results indicated that artificial wetlands might be a promising technology to treat perchlorate-contaminated waters, especially suitable for groundwater plumes or non-point surface water at lower perchlorate concentration levels. Wetland treatment efficiency was mainly controlled by nitrate concentration, organic substrate availability, and reoxygenation near the surface. Microbial degradation played a more important role than plant uptake and ftansformation in this type of wetland system. Perchlorate degradation rates and lag times in sediments and soils were site-specific and dependent on numerous environmental conditions, such as organic substrate availability, nitrate, initial C104' concentration, and prior exposure. Perchlorate degradation rates were mainly affected by organic substrate availability; lag time was mainly controlled by nitrate concentration and organic substrate availability. Rapid natural attenuation of perchlorate in sediments of natural habitats was demonstrated using in-situ dialysis samplers (peepers). Perchlorate penetration and persistence were found seasonally variable, with colder season showing the highest penetration. Biodegradation of perchlorate occurred over a depth of only 1-10 cm, and this active depth changed seasonally. Perchlorate distribution closely mirrored nitrate distribution in sediments. There was a large potential of perchlorate uptake in a variety of aquatic and terrestrial plants. Perchlorate uptake in aquatic plants from streams was up to two orders of magnitude higher than the bulk water concentration. Perchlorate uptake in tertestrial plants was dependent on exposure duration, species, and accessibility of perchlorate source. Plants may become the source and sink of perchlorate. This research has elucidated the fate of perchlorate in natural systems and highlighted the potential of using wetlands to treat perchlorate-contaminated water.Item In-situ degradation of high explosives(Texas Tech University, 1999-08) Brown, Justin HeathThe purpose of this research is to develop an in situ method to biodegrade high explosives in the vadose zone. The research project involves the construction of an experimental field site to force an anaerobic treatment zone and thus stimulate indigenous microorganisms to biodegrade the HE. The desired level of treatment is to reduce the HE concentrations to below the RRS2 values.Item Laboratory studies indicating the potential for bioremediation of high explosives in soil at the Pantex Plant(Texas Tech University, 1998-12) Medlock, Walter NThe main purpose of this thesis is to provide information in support ofthe field study. In May of 1998, eight, 30-ft wells were constmcted at the field study site to facilitate the gas injection and extraction procedure. The core samples from these wells were preserved and transported to Texas Tech University where they were analyzed with the following objectives in mind: (1) delineate the extent of HE contamination at the field study site, (2) determine if microbial (metabolic) activity is present in the soil, (3) enumerate the anaerobic microbial population, and (4) examine the relationships among HE concentration, metabolic activity, and microbial population.Item Sorption studies of subsurface pantex soils(Texas Tech University, 1997-08) Givens, Dennis R.The Pantex Plant is a Department of Energy facility that is jointly managed by Mason and Hanger-Silas Mason Company, Inc., and Battelle Memorial Institute (BMI). It is located approximately 18 miles northeast of Amarillo, Texas. The plant was built by the U.S. Army in 1942 for the purpose of ordnance production. The current primary mission deals with the assembly, disassembly, maintenance and modification of the nation's nuclear weapons. The plant also performs on-site machining and casting of conventional high explosives for use in nuclear weapons. Contamination of the groundwater beneath the Pantex Plant by several contaminants has been detected. Primary contaminants that have been detected are chromium, trinitrotoluene (TNT), trichloroethylene (TCE), high mehing explosive (HMX), and research and development explosive (RDX). The contamination has thus far been restricted to a perched aquifer that underlies the plant. However, there is concern that these contaminants could reach the Ogallala aquifer below if not naturally attenuated by the perched aquifer.