Browsing by Author "Hughes, John M."

Now showing 1 - 6 of 6
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    Exhaust gas emissions from a prototype scrap tire incinerator/wastewater treatment plant sludge dryer
    Tober, M. Lyn (Virginia Tech, 1996)
    In conjunction with Atlantic Pacific Engineering and the Henry County Public Service Authority, Virginia Tech’s Environmental Engineering program measured the emissions from an experimental scrap tire incinerator/wastewater treatment plant sludge dryer. This report recounts the techniques used and the results obtained during this testing. The Virginia Department of Environmental Quality supplied a list of pollutants of permitting interest which included a variety of criteria pollutants, toxics, and metals. Sampling for all the listed compounds required adherence to EPA Methods 5, 201A, 29, 0010, 0011, 0030, 6, 7D, 26A, and 18. Emissions testing transpired during the incinerator’s 72-hour test burn: 0800 October 30th to 0800 November 2nd, 1995. Due to time constraints, only part of one nonpotable water sampling series was completed rather than the proposed duplicate testing using both drying agents: nonpotable water and sludge. High particulate (57 lb/hr) and metal (21.4 lb/hr total) emissions indicate a fairly significant amount of air pollution control equipment will be necessary for a commercial plant. Both nitrogen oxides and sulfur dioxide had low emission rates: 1.73 lb/hr and 0.64 lb/hr, respectively, due to the nonpotable water spray acting as a fairly efficient scrubber removing a great deal of nitrogen oxides, sulfur dioxide, and some metals. Because of sample analysis preparation problems, no organics results were obtained. Commercial development of this incinerator will have to include a sizable quantity of air pollution control equipment: a $5 million plant will need approximately $1 million worth of control equipment.
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    Factors Affecting Mobility of Copper in Soil-Water Matrices
    Al-Taher, Hossam (Virginia Tech, 2001-02-02)
    Copper is applied to many crops as a fungicide/bactericide, including plasticulture tomato growing operations. Field tests have shown that copper is sometimes found in ground water near these fields. Therefore, a laboratory study was undertaken to determine if this copper can result from plasticulture application and to determine the mechanisms that account for the movement through soil to the subsurface. From the factors that may affect this mobility process; TOC, dryness and its temperature cycle and water content of the soil were selected for study. These factors were investigated in both batch and continuous flow (column) processes. Copper mobility through soil columns was associated with TOC mobility, and soil drying had a major effect on both copper and TOC mobility. The concentration of copper eluted from columns containing dried soils was up to 20 times higher from those containing wet soils. The extent of dryness was found to affect mobility. First-flush-pattern for both copper and TOC from the columns was observed in all columns studies. In this research the copper mobility through the A- and B-horizon of Bojac sandy loam from the Eastern Shore of Virginia was studied. This study included both batch and column processes. The effects of pH, TOC and humic substances were investigated. The mobility of copper was found to be higher through A-horizon soil. The pH was found to have a considerable effect on the mobility of copper and TOC. The highest mobility of copper was achieved at pH 6.24 and its mobility through both soil horizons was associated with the mobility of TOC. A study of the humic substances indicated that fulvic acids had 4 times higher adsorption capacity for copper than humic acids. The association between fulvic acids and copper, coupled with the mobility of TOC and fulvic acids in the soil, accounted for transport of copper through soil columns.
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    Geochemcial Controls on Arsenic and Phosphorus in Natural and Engineered Systems
    Davis, Jason Edward (Virginia Tech, 2000-12-14)
    This thesis elucidates fundamental reactions that can control concentrations of arsenic and phosphate in water sources. High levels of arsenic or phosphorus have significant implications for the environment-- arsenic is extremely toxic to humans while phosphorus can cause eutrophication. Initial work focused on arsenic solids that might exert geochemical control on soluble arsenic. Formation of proposed iron, barium, copper and zinc-arsenic solids were systematically examined under realistic environmental conditions. Thermodynamically favored copper, ferrous and barium solids did not form under circumstances of significance to drinking water sources. However, sorption of arsenic to iron, zinc and copper solids was discovered to be very significant, depending on the pH and solids age. Given the established importance of sorption in arsenic and phosphate chemistry, two key constituents (silica and sulfide) implicated in mobilization of sorbed arsenic or phosphate were examined in detail. The addition of silica, which competes with arsenate or phosphate for sorption sites on Al(OH)3 and Fe(OH)3 hydroxides, caused release of 0-30% sorbed As and P at pHs between 7.0 and 8.5. Reaction of sulfide with Fe(OH)3 led to instantaneous release of 50-95% of sorbed As and P through a reductive dissolution mechanism. This instantaneous release was slowly reversed as orpiment (As2S3) and vivianite [Fe3(PO4)2] slowly precipitated, but under other circumstances, these solids would not be expected to form. Modeling results suggest that arsenic and phosphate concentrations could either increase or decrease in response to reaction between Fe(OH)3 and sulfides, thereby reconciling literature reports that seemed to contradict one another.
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    Investigation of water vapor effects on the detection of nitric acid vapor with the tungstic acid technique
    Marinaro, Ralph Michael (Virginia Polytechnic Institute and State University, 1986)
    An automated tungstic acid technique (TAT) has been successfully used to measure gaseous HNO₃ in the presence of water vapor. The TAT is based on the diffusion of gaseous HNO₃ to the interior walls of a tube coated with tungsten VI oxide (WO₃), where it is selectively chemisorbed. The collected HNO₃ sample is thermally desorbed from the WO₃ surface, as NO, and measured by a chemiluminescent oxides of nitrogen analyzer. The integrated analyzer response is directly proportional to the nitric acid collected. Based on nitric acid hydration characteristics, a decrease in the diffusion coefficient and thus collection efficiency for denuder type measurement techniques may result with increased atmospheric water vapor (i.e., relative humidity). This study emphasizes the effect of water vapor (i.e., relative humidity) as a potential interferent for HNO₃ collection with the TAT system. The effect of water vapor (< 78% RH) on the collection efficiency for HNO₃ with the tungstic acid technique is negligible at 25°C, but is significant only at elevated sampling temperatures. This threshold effect is further substantiated and eliminated when a modified sampling collection system was designed with coolant capabilities. The new design has been tested to sub-part-per-billion (NOx analyzer detection limit) levels with minimal loss of gaseous HNO₃ signal, thereby increasing sensitivity to atmospheric HNO₃ concentrations and maintaining the gas/aerosol sample integrity.
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    Predictive model for plume opacity
    Lee, Kai-Tien (Virginia Polytechnic Institute and State University, 1985)
    In recent years, as control systems for boiler emissions have been upgraded, some utility sources have experienced increased plume opacity. Cases of plume opacity exceeding in-stack opacity are due to 1) the aerosol formed by condensation of primary sulfuric acid and water vapor onto polydisperse plume particles and 2) the presence of fine particles which grow into the visual size range by heterogeneous condensation and coagulation processes as the plume is cooled and diluted by mixing with the ambient air. In order to better understand the factors leading up to acid plume formation, a computer simulation model has been developed. This plume opacity model has been utilized to simulate sulfuric acid aerosol formation and growth. These processes result from homogeneous nucleation, condensation and coagulation which substantially increase the concentration of submicrometer sized aerosols. These phenomena bring about significant increases in plume opacity. Theoretical relationships have been derived and transformed into 21 computer model to predict plume opacity at various downwind distances resulting from pulverized coal combustion operations. This model consists of relatively independent components-such as an optics module, a bimodal particle size distribution module, a polydisperse coagulation module, a vapor condensation and nucleation module and a plume dispersion module-which are linked together to relate specific flue gas emissions and meterological conditions to plume opacity. This unique, near-stack, plume-opacity-model approach provides an excellent tool for understanding and dealing with such complex issues as: • increasing plume opacity observed for emissions containing sulfuric acid aerosols, • explaining the correlation between primary particle size distribution and light—scattering effects, • predicting the opacity level resulting from combustion of various coal types, • predicting control equipment effects on plume opacity.
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    A Scrolling Geotextile Fabric Filter Device for Primary Clarification
    Riddle, Craig Stuart (Virginia Tech, 2002-09-17)
    This study investigated the feasibility of using a portable geotextile fabric based filtering device to remove suspended solids from raw sewage. This device was considered to replace a conventional primary clarifier. The proposed filtration process directs wastewater influent through a geotextile fabric filter. As filtering progresses, and solids accumulate on the fabric, the loaded fabric is scrolled to present a fresh surface. Only non-woven polypropylene geotextile fabrics were investigated. These products are constructed by spunbonding or needle-punch technique. Needle-punched fabrics proved superior in terms of Total Suspended Solids (TSS) filtering performance and fabric usage rates. Spunbonded products absorbed less moisture, reducing loaded fabric weight. Fabric thickness did not affect filtration efficiencies for either type of geotextile. Process variables affecting unit performance were investigated. Flow rate, head level, and fabric tension did not affect TSS removal. Fabric tension, however, is limited by tensile strength of the geotextile material. Two wastewater receving basin configurations for the device were investigated. An influent basin with two 450 angled walls forming a V-shape performed better in terms of fabric feed rates. It is recommended for full-scale applications. Finally, several methods were used in an effort to improve treatment performance. Polymer use, and polymer use in conjunction with pre-screening of wastewater, were both used. Polymer use alone did not increase the operating efficiency. Polymer use, along with pre-screening, was promising enough to consider this as a stand-alone treatment system.