Browsing by Subject "Ammonia"
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Item Item Balancing ammonia and alkalinity for nitrification at Walnut Creek Wastewater Treatment Plant(2014-05) Weidner, Austin David; Lawler, Desmond F.The Walnut Creek Wastewater Treatment Plant in Austin, Texas, has recently experienced increasing influent ammonia concentrations. Nitrification, the biological process used to treat ammonia, consumes alkalinity, which makes it difficult to properly treat ammonia while still maintaining the pH above the required discharge level of pH 6. Operators have looked to the addition of chemicals to supplement alkalinity; one creative alkalinity source was CaCO₃ solids, which are generated by the lime-softening process at Davis Water Treatment Plant. In 2011, the utility began transferring solids to Walnut Creek and immediately noticed improvements in both the nitrification efficiency and the effluent pH. However, undissolved solids accumulated at Walnut Creek and had a detrimental effect on the biosolids treatment efficiency at Hornsby Bend Biosolids Management Plant. Ultimately the costs of the poor biosolids treatment forced the utility to examine an alternative alkalinity source. The objective of this thesis is to help Walnut Creek optimize the use of various alkalinity sources to find a long-term solution that will improve the alkalinity and ammonia balance for adequate nitrification. Analysis of the plant’s influent characteristics suggested that industrial users, especially the semiconductor industry, are major contributors of ammonia and sulfate to the wastewater. A theoretical modeling based on chemical equilibrium predicted that using the CaCO₃ solids would provide a maximum alkalinity benefit of 47 mg/L as CaCO₃. Experimental dissolution jar tests were conducted to verify the model predictions and estimate the kinetics of dissolution. Results from these tests showed no significant dissolution of CaCO₃, and that the solids remained unchanged throughout the test. These results indicate that CaCO₃ solids are not recommended to provide alkalinity at Walnut Creek. Finally, the use of Mg(OH)₂ for alkalinity was employed at Walnut Creek and allowed operators to reduce the blowers that provide aeration. To quantify this observation, bubbling column tests were conducted to measure differences in the oxygen transfer rate at various Mg(OH)₂ concentrations. However experimental results did not match the expectations, so future work is required.Item Characterization of ammonia emissions from ground level area sources at central texas dairies(2009-05-15) Mutlu, AtillaThere is a need for a robust and accurate technique to measure ammonia (NH3) emissions from animal feeding operations (AFOs) to obtain emission inventories and to develop abatement strategies. Seasonal studies were conducted to measure NH3 emissions from open-lot and free-stall dairies in central Texas since summer of 2003. Ammonia emission flux (EFl) was measured using an isolation flux chambers (FC) protocol from ground level area sources (GLAS) and converted to emission factor (EF) to potentially develop source specific NH3 emission control strategies. The GLAS including open-lots, free-stall barns, separated solids, primary and secondary lagoons and milking parlor were sampled to estimate NH3 emissions. In the first study, assessment of summer and winter data from the open-lot dairy indicated that overall NH3 EFs were 11.6 ?7.1 kg NH3 year-1 head-1 for the summer and 6.2 ?3.7 kg NH3 year-1 head-1 for the winter season. The estimated annual NH3 EF was 9.4 ?5.7 kg NH3 year-1 head-1 for this open-lot dairy. The estimated NH3 emission factor for winter was nearly 47% lower than summer EF. Open-lot corrals (~63%) in summer and (~95%) in winter were the highest contributors to NH3 emissions for the open-lot dairy. In the second study, the EFs for the free-stall dairy were determined to be 11.1 ?4.9 kg NH3 year-1 head-1 for summer season and 4.7? 4.9 kg NH3 year-1 head-1 for winter season. The estimated annual NH3 EF was 8.4 ?4.9 kg NH3 year-1 head-1 for this free-stall dairy. In winter, composted manure and free-stalls contributed nearly 73% to the total NH3 emissions for the dairy. However in summer, approximately 65% of overall NH3 emissions were contributed by two lagoons at the dairy. The overall differences between winter and summer NH3 emissions from the dairies were due to ambient temperature variations and loading rates of manure on GLAS. There was spatial variation of NH3 emissions from the open-lot earthen corrals due to variable animal density within different divisions of the open-lot. This spatial variability was attributed to dispirit manure loading within these areas.Item Evaluation of a Rice/Soy Fermentate on Broiler Performance, Litter Characteristics, and Fecal Odorant Volatilization(2012-10-19) Williams, MalloriThe objective of this research was to determine the effect of a rice/soy fermentate when included in broiler diets and spray applied as a litter amendment on broiler performance, litter characterization, and ammonia and odorant volatilization. A series of three experiments were conducted to evaluate the effectiveness of the fermentate to reduce ammonia and odor compound volatilization when spray-applied to on recycled broiler litter. In experiment 1, spray-applying the two fermentate products did not affect ammonia volatilization; however the methodology was verified, as reductions were observed in the positive control. In experiment 2, spray application of the rice/soy fermentate did not have any impact on litter characteristics or average broiler body weight. However spray application of the rice/soy fermentate significantly reduced (P<0.05) observed mortality at the conclusion of the experiment. In experiment 3, spray application of the two fermentate products on fresh pine shavings following two activation times did reduce ammonia volatilization; although significant (p < 0.05) differences were observed in carbon and nitrogen content on day 43 and nitrogen content on day 35. Two experiments were conducted to evaluate the effectiveness of two fermented rice/soy products on volatilization of fecal odor compound volatilization and performance parameters when included in broiler diets. In experiment 1, the addition of fermentate B at 900 g/ton increased (p < 0.05) d 21 body weight. The inclusion of both fermentates (A and B) resulted in significant decreases (p < 0.05) in multiple volatile organic compounds, strongly associated with odor related to poultry. In experiment 2, the addition of fermentate B at 900 g/ton resulted in a significant increase (p < 0.05) in d 14 body weight. Inclusion of both rice/soy fermentates (A and B) significantly increased (p < 0.05) carcass weights. Additionally, significant reductions (p < 0.05) were observed in day 21 and 42 fecal pH with both fermentates (A and B). Taken in totality, these data demonstrate the ability of a rice/soy fermentate to alter litter nutrient content and intestinal environment resulting in increased nitrogen sequestering, reduced digest pH, reduce odorant volatilization, increased early bird weight, and reduce early mortality.Item Glow Discharge Enhanced Chemical Reaction: Application in Ammonia Synthesis and Hydrocarbon Gas Cleanup(2014-06-05) Ming, PingjiaTwo different plasma enhanced processing technologies were investigated in this study: ammonia synthesis from steam and nitrogen, and hydrocarbon gas clean up. Ammonia is a common sanitizer in swimming pool and fish tank, changing the pH of the water, which does not benefit bacteria. Also ammonia is used in various NOx reduction technologies, for example, selective catalytic reduction (SCR) methods have been studied for the cleaning of diesel engine exhaust. A small compact glow discharge was applied to investigate ammonia synthesis from steam and nitrogen. Ammonia was successfully detected via UV-VIS absorbance and through increasing pH value of treated water by product gas. Heavier hydrocarbon C3 to C5 are produced with natural gas, but cannot be used in sensitive energy conversion systems, like solid oxide fuel cell (SOFC). Utilizing small amount of energy to clean up and reform heavier hydrocarbon into synthesis gas is necessary when using hydrocarbon sources which contain heavier hydrocarbons mixture such as EPE (74.8% methane, 8% ethane, 8% ethylene, 2.1% propane and 1.1% Propene). Non-thermal plasmas, due to their unique non-equilibrium characteristics, offer advantages as method of reforming at lower temperature (100-150 ?C) and atmospheric pressure. For an EPE gas mixture, a high conversion and low specific energy cost is desirable. Variation in discharge power density, air and, water addition were tested, in order to find conditions which were energetically feasibility, efficiency and sufficiently reduced the higher hydrocarbon. High conversion efficiency was achieved, in propane and propene, which was more than 90%, without carbon deposition through air addition. For a 1 J/ml power density and 1.08 O2/C ratio condition, a process efficiency of 74% and 54% available output energy was achieved. At the same time, the concentration of ethane, ethylene, propane, propylene, and acetylene were cleaned-up to value of 1.01%, 1.67%, 0.08%, 0.00%, and 0.50%, respectively, less than 20% of their original input amount. Higher power density produced cleaner (less high hydrocarbons) in the products, and were still energetically feasible, but less efficient.Item Influence of surface passivation on the photoluminescence from silicon nanocrystals(2010-08) Salivati, Navneethakrishnan; Ekerdt, John G.; Downer, Michael C.; Mullins, C. B.; Korgel, Brian A.; Hwang, Gyeong S.Although silicon (Si) nanostructures exhibit size dependent light emission, which can be attributed to quantum confinement, the role of surface passivation is not yet fully understood. This understanding is central to the development of nanocrystal-based detectors. This study investigated the growth, surface chemistry, passivation with deuterium (D2), ammonia (ND3) and diborane (B2D6) and the resulting optical properties of Si nanostructures. Si nanocrystals less than 6 nm in diameter are grown on SiO2 surfaces in an ultra high vacuum chamber using hot-wire chemical vapor deposition and the as grown surfaces are exposed to atomic deuterium. Temperature programmed desorption (TPD) spectra show that that the nanocrystals surfaces are covered by a mix of monodeuteride, dideuteride and trideuteride species. The manner of filling of the deuteride states on nanocrystals differs from that for extended surfaces as the formation of the dideuteride and trideuteride species is facilitated by the curvature of the nanocrystal. No photoluminescence (PL) is observed from the as grown unpassivated nanocrystals. As the deuterium dose is increased, the PL intensity also begins to increase. This can be associated with increasing amounts of mono-, di- and trideuteride species on the nanocrystal surface, which results in better passivation of the dangling bonds and relaxing of the reconstructed surface. At high deuterium doses, the surface structure breaks down and amorphization of the top layer of the nanocrystal takes place. Amorphization reduces the PL intensity. Finally, as the nanocrystal size is varied, the PL peak shifts, which is characteristic of quantum confinement. The dangling bonds and the reconstructed bonds at the NC surface are also passivated and transformed with D and NDx by using deuterated ammonia (ND3), which is predissociated over a hot tungsten filament prior to adsorption. At low hot wire ND3 doses PL emission is observed at 1000 nm corresponding to reconstructed surface bonds capped by predominantly monodeuteride and Si-ND2 species. As the hot wire ND3 dose is increased, di- and trideuteride species form and intense PL is observed around 800 nm that does not shift with NC size and is associated with defect levels resulting from NDx insertion into the strained Si-Si bonds forming Si2=ND. The PL intensity at 800 nm increases as the ND3 dose is increased and the intensity increase is correlated to increasing concentrations of deuterides. At extremely high ND3 doses PL intensity decreases due to amorphization of the NC surface. In separate experiments, Si NCs were subjected to dissociative (thermal) exposures of ammonia followed by exposures to atomic deuterium. These NCs exhibited size dependent PL and this can be attributed to the prevention of the formation of Si2=ND species. Finally, deuterium-passivated Si NCs are exposed to BDx radicals formed by dissociating deuterated diborane (B2D6) over a hot tungsten filament and photoluminescence quenching is observed. Temperature programmed desorption spectra reveal the presence of low temperature peaks, which can be attributed to deuterium desorption from surface Si atoms bonded to subsurface boron atoms. The subsurface boron likely enhances nonradiative Auger recombination.Item Interactions of inversion with other vibrations in the normal and deuterated ammonias(Texas Tech University, 1971-01) Cress, Daniel HuggNot availableItem Kinetics of low temperature oxidation of ammonia trace quantities(Texas Tech University, 1973-08) Bentsen, Peter CraigThe purpose of this study is actually threefold. The first is to provide the experimental data for the oxidation of ammonia over a platinum catalyst in the ppm range which is so obviously missing from the literature. The second is to use these data to obtain a quantitative mathematical description or model of the rate of ammonia oxidation with emphasis on the utilization of this model for design purposes. The third is to study catalyst stability and be able to quantify the deactivation.Item Selective reduction of nitrogen dioxide by ammonia(Texas Tech University, 1972-12) Cheng, Yang-lehNot availableItem The adsorption of ammonia on copper-sulfate impregnated silica gel(Texas Tech University, 1971-05) Schlittler, Charles EdwardNot availableItem The oxidation of ammonia on a supported ruthenium catalyst(Texas Tech University, 1971-05) Johnson, Tiffin ElmoreThe buildup of biologically produced ammonia in a closed spacecabin environment represents a hazard to crewmen making extended voyages. The primary source of ammonia is urine, and although efforts are made to control emissions at this source, traces of ammonia escape into the spacecabin. In order to maintain a safe and breathable atmosphere for life support, the spacecraft's trace contaminant removal system must be able to efficiently remove this ammonia. Potentially the best method of doing this is through catalytic oxidation to water and molecular nitrogen. The National Aeronautics and Space Administration (NASA) has awarded Texas Tech University a two year research contract (NAS 1-9506) to study the changes which ammonia undergoes when passed through the catalytic oxidizer of a spacecraft trace contaminant removal system.