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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Quantification of greenhouse gas emissions in biological wastewater treatment

Aboobakar, Amina January 2014 (has links)
There is an increasing need to reduce greenhouse gas (GHG) emissions and to identify influencing factors from wastewater treatment plants (WWTPs), particularly process emissions consisting of nitrous oxide (N2O), and methane (CH4) GHG, with global warming potentials about 310 and 21 times higher than carbon dioxide (CO2) respectively (IPCC, 2006). However, the challenges offered by full-scale environments, have to date, restricted a real-time, comprehensive approach of monitoring emissions and influencing factors. This study aimed at addressing this knowledge gap, by reporting the findings of a long-term, online, continuous monitoring of GHG emissions and operational variables. Lanes were monitored in nitrifying activated sludge plants (ASP) controlled under ammonia (NH4 + ) and dissolved oxygen (DO) set-points (DO setpoints monitored: 1.5 and 2.0 mg/L), as well as in a biological nutrient removal plant (BNR) under NH4 + control. The findings showed that CH4, although potentially formed in non-aerated compartments, was emitted in aerobic zones, at an average emission factor (EF) of 0.07 % of influent and removed chemical oxygen demand (COD). Nitrous oxide EFs on the other hand, depended on relative nitrogen fractions, with influent-based EFs showing a best-case scenario, at 0.05–0.72 % of both influent total nitrogen (TN) and NH4 + , compared to the higher EFs based on removed nitrogen at 0.13–3.9 % of TN and NH4 + removed. The processes operated under the same control settings (DO set-point 1.5 mg/L), had similar, or identical, EF, suggesting that settings could help predict the range of EF. Nitrous oxide was always produced in the presence of NH4 + , even at low concentrations (=<0.5 mg/L), therefore linking N2O production with NH4 + oxidation, particularly with nitrifier nitrification. Incomplete denitrification under low carbon to nitrogen (C/N) ratios also triggered N2O production (EFs of 2.4 and 4.1 % of reduced TN at C/N ratios of 2.8 and 2.4 respectively), particularly with intermittent aeration. Therefore, nitrifier denitrification and incomplete denitrification simultaneously occurred and triggered N2O production in the final stages of nitrification. The BNR lane was the most operationally stable process, therefore offering the best balance between efficiency (60–99 % less aeration and energy per kg of treated NH4 + ), low carbon footprint and reduced EFs (0.08–0.1 % of all nitrogen fractions). The second best option was the DO set-point control of 1.5 mg/L, with low EFs (0.05–0.2 %), stable operational conditions and reduction in aeration requirements (up to 340 % less than DO set-point 2.0 mg/L). Operating ASP under NH4 + control however, led to 7–96 % more efficiency than under DO set-points, although it required better control in the back end of the process. Only an online, long-term methodology such as adopted in this study, could provide insights into emission variability and the effect of operational variables on promoting or reducing emissions. Based on this, strategies to mitigate emissions at full-scale were recommended.
2

Investigating methods used to quantify gaseous emissions from vegetation fires using spectroscopic measurements

Tattaris, Maria January 2013 (has links)
This work investigates the application of ground-based trace gas spectroscopy to deter- mine the chemical makeup and quantity of smoke emitted from vegetation fires. Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS) has been infrequently deployed in fire emission studies, yet is potentially a portable, lightweight, inexpensive and simple method. Fourier Transform Infrared (FTIR) spectroscopy has been more commonly used in fire emissions studies, but not generally in the long (> 10 m) open-path ground-based geometry explored here. This research combines these approaches to investigate their ability to quantify trace gas fluxes emitted from open vegetation fires, in part to help validate estimates of fuel consumption rate based on fire radiative power [FRP] measures. UV and IR measurements of the smoke plumes from controlled open vegetation fires (> 4 hectares) were recorded during three field campaigns in Arnhem Land (Northern Australia), Kruger Park (South Africa) and Alberta (Canada). The UV-DOAS was used to quantify NO2 and SO2 vertical column amounts (maximum column amounts approx 200 ppmm), allowing the determination of flux-rates when used to traverse the smoke plume and coupled with plume velocity estimates. Horizontal column amounts of the main plume carbonaceous species (CO2, CO and CH4) were quantified using FTIR methods and used to calculate emission ratios and emissions factors for the target gases, providing detail on inter- and intra- fire variations that are often available from the current literature. Providing NO2 and SO2 are detectable by the FTIR, UV-DOAS flux-rates and FTIR emissions ratios can be combined to calculate flux rates for all FTIR-detectable species. This allows for the determination of the total carbon flux from the fires, and its variation over time. Since vegetation is approximately 50% carbon, this flux is in theory directly proportion to the fuel consumption rate, and directly comparable to the fire’s radiative power output variations as determined by airborne thermal imaging. Hence, in addition to providing the means to estimate smoke plume chemical makeup, emissions magnitude and variability, the simultaneous deployment of the techniques of UV-DOAS, FTIR spectroscopy and airborne thermal imaging enables the validation of FRP derived fuel consumption rates. The FRP method is gaining ground as a tool for improving biomass burning emissions inventories based on satellite observations, but at present has had relatively little validation. This study therefore contributes to the ongoing evaluation effort. Findings demonstrate that the UV-DOAS is an effective way to measure column amounts of SO2 and NO2 in vegetation fire plumes, providing that the fires are of an adequate size and emit smoke in sufficient quantities. The exact nature of the ability to accurately quantify NO2 and SO2 using the method did have a dependence on fuel type, since the combustion of different fuel types (e.g. grasses vs. woody fuels vs. organic soils) appeared to cause more of less of these particular gases to be emitted. There was difficulty in confidently detecting NO2 via the OP-FTIR approach for the majority of the study cases, due to the relatively weak IR absorption bands used and the relative scarcity of this gas in the plumes in comparison to some others studied. We advocate using the UV-DOAS and FTIR combination in relation to trace gas measurements from vegetation fires, providing SO2 or NO2 can be identified by the FTIR in the particular biomass burning situation under study. Where simultaneous FRP measurements are available, the carbonaceous flux rates calculated using the FTIR/UV-DOAS method show a strong correlation with FRP, helping to confirm the relationship between FRP and fuel consumption rate at the scale of these vegetation fires. This is to our knowledge currently by far the largest fires upon which this relationship has been evaluated, prior evaluations being limited to laboratory-scale events only.
3

Improvement of the oxygen reduction cathodes of microbial fuel cells designed to treat municipal wastewater

Burkitt, Richard John January 2014 (has links)
The Microbial Fuel Cell is a technology for self-powered pollution remediation, receiving widespread academic interest only since the turn of the 21st century. The device centres on immobilised anaerobic microbes that oxidise organic pollutants in industrial or domestic wastewater and generate an electrical charge. To generate useful energy from this charge, oxygen is commonly used as an electron acceptor at a cathode to complete the cell. This oxygen reduction reaction (ORR) requires catalysis and is thought to produce H2O at pH7. High cost materials such as Platinum and energy in-efficient materials such as activated carbon are typically used to catalyse this reaction in MFC’s. The majority of ORR catalysis research is based in acid or alkali media. To facilitate MFC commercialisation the project aim was to enhance cathode performance by developing an active, selective, stable and low cost oxygen reduction catalyst. Presented within this thesis is a fundamental study of the enzyme mimic catalyst Iron Phthalocyanine (FePc). With the addition of a novel anion selective binder and membranes, the low cost cathodes are applied to laboratory scale single chamber MFC’s fed with primary clarifier influent wastewater. With use of a rotating ring disc electrode, the O2 reduction mechanism was found to produce OH- and the O2 adsorption step was not rate limiting. The mechanism with the lowest overpotential proceeds through an intermediary of strongly adsorbed peroxide. Unfortunately, partial release of this H2O2, ranging from 0.5 to 7%, caused catalyst de-stabilisation. The traditional approach of catalyst pyrolysis was found to be ineffective remedy, reducing the number of viable sites (by 96%) and overall activity. It was hypothesised that pH splitting from OH- production could be reduced with anion selective materials. A Quaternary-1,4-diazabicyclo-[2.2.2]-octane Polysulfone (QDPSU) anion exchange ionomer utilising a Dabco anion exchange group was implemented in thin films and MFC cathodes as a substitute for Nafion. A facile tafel slope of 25.4 mV per decade of current implied a decrease in the overall activation energy for ORR. Oxygen diffusivity was comparable with Nafion and in real wastewater the air cathodes producing an average of 34% more power in MFC’s. An impedance spectroscopy study identified a numerical way of quantifying the poisoning of anion exchange groups. The addition of ion selective membranes increased the resistance showing this process to be related to ion diffusion, thin membranes with quaternary ammonium produced the best results.
4

An investigation of food and feed based mycotoxins as potential endocrine disrupting contaminants

Frizzell, Caroline Margaret January 2014 (has links)
Hormones regulate numerous biological processes. Endocrine disrupting compounds (EDCs) are chemicals which are capable of altering normal hormone signaling, and as a result may contribute to a wide range of adverse health effects. Mycotoxins are one group of compounds which remain to be extensively tested for endocrine disruption. These compounds are toxic secondary metabolites of fungi, which are ubiquitous in nature and may be present in the food and feed of humans and animals, respectively. This study has made use of human in vitro systems to assess the impact of mycotoxins on steroid hormone receptor and non-receptor mediated pathways. The mycotoxins tested included zearalenone (ZEN) and two of its metabolites, α- and β-zearalenol (α-and β-ZOL); alternariol (AOH); the trichothecenes deoxynivalenol (DON), T-2 and HT-2 toxins; ochratoxin A (OTA) and patulin (PAT). The bioassays used included reporter gene assays (RGAs) with natural estrogen, androgen, progestagen and glucocorticoid steroid receptors; and the H295R steroidogenesis model. Endpoints such as nuclear receptor transcriptional activity, receptor expression, hormone production, steroidogenic gene expression or cytosol protein expression were assessed. All of the mycotoxins tested had significant effects on one or more of these parameters when compared to controls. The human in vitro systems used in this thesis have proved very useful for assessing interferences with the endocrine system. As steroid hormones and steroid hormone action is critical to numerous normal biological processes, changes in the activity of steroid hormones due to interference by mycotoxins may serve as a discerning indicator of endocrine dysfunction. This knowledge on the mechanisms of action of various mycotoxins is valuable for risk assessment purposes, which are necessary in order safeguard humans and animals.
5

Oxidation of mercury in flue gas streams via gold catalysis

Morgan, Michelle Marie January 2015 (has links)
Mercury emission from coal-fired power plants is a global problem that has garnered attention due to regulations limiting the emission from anthropogenic sources. The three forms of mercury that are all emitted include: elemental mercury (HgO), oxidized mercury (Hg2+), which can both then form particulate mercury. Since current HgO removal technology is not effective, and HgO is extremely toxic, new catalytic solutions are necessary to allow complete oxidation of HgO. The aim of the project was to understand the mechanism of heterogeneous catalyzed mercury oxidation from simulated flue gas streams using supported gold catalysts. It has been proposed in the literature that three mechanisms could potentially be responsible for mercury oxidation: the Langmuir-Hinshelwood, the Eley-Rideal, and the Mars-Maessen mechanisms. To investigate the possible reactions, the mercury saturator was placed either before or after the catalyst bed and in some experiments, the gold catalyst was pre-saturated with mercury. Numerous characterization and gas-phase analysis techniques were used to identify surface changes and species present at both the surface and in the gas stream. For the gold catalysts, it was found that pre-saturating the catalyst with mercury improved mercury oxidation. Based on this data, mercury adsorption is necessary to promote the reaction, not mercury in the gas phase. In addition, the catalysts more efficient at oxidizing mercury generally had increased CI2 production. The gold-mercury amalgam was seen in the STEM images, but only in the more complex gas compositions, not in the N2/Hg gas mixture. In addition to the gold catalysts, ruthenium catalysts supported on titania were tested due to their promotion of the Deacon process. Mercury oxidation and CI2 production was as high with the ruthenium catalysts as with the gold supported catalysts. It is possible that the titania supports are better at producing an oxidized form of mercury, such as HgCI2.
6

An investigation of spatial and temporal pesticide dynamics at the catchment scale

Harrison, Rebecca Victoria January 2014 (has links)
Pesticides are an essential component of modern agriculture and large quantities are applied annually on a global basis to arable land to prevent crop loss. After application, pesticides can be taken up by plants, degraded or distributed in the environment between the soil and in surface water or groundwater. Transport of pesticides in runoff and subsurface flow during rainfall events poses a significant concern for water quality with adverse effects on drinking water and aquatic life. Establishing the links between pesticide applications, hydrology, soil properties and erosion dynamics is key to understanding the fate of pesticides in the environment. This study has used a multi-scale approach combining laboratory experiments with a focused field campaign in a lowland agricultural catchment to investigate spatial and temporal pesticide dynamics at the catchment scale. The research provides methodological development for analysis of pesticides in soil, an understanding of the behaviour of pesticides in the soil and water environment after application due to rainfall and a catchment scale study of pesticide transport and distribution annually, seasonally and during individual storm events. First order controls on pesticide transport have been identified to partly explain the distribution of pesticides through a catchment and the upstream conditions required for pesticide movement. These include timing of application, quantity of pesticide available, antecedent soil moisture and rainfall, storm event characteristics, land use and season. An investigation of sediment-associated pesticides showed no significant quantities in stream-bed, reservoir bed or suspended sediment during storm events. The major risk factor for pesticide movement was found to be dissolved pesticides in storm event runoff. Results of this research can be used by farmers, water companies, regulatory bodies and scientists to improve water resource protection from field to catchment scales.
7

Emissions abatement technology, fuels and low emissions vehicles : win-win for air quality and climate change

Cairns, Justin January 2013 (has links)
The impact of a change in emissions abatement technology, fuel or vehicle on carbon dioxide (CO) 2 and toxic air pollutant emissions derived from road transport was investigated. Road transport emissions were calculated and non-mobile source emissions rates were compiled for the base year 2005 for the City of Leicester, which was the case study for the research. Factor and cluster analysis were applied so that roads could be classified into groups, allowing diurnal traffic profiles to be assigned to roads with similar attributes prior to air quality modelling and to enable the characteristics of typical roads in Leicester to be identified. Five road classifications were developed. The emissions inventory compiled along with meteorological data, background pollutant concentration values and the five diurnal traffic profiles were input into an air quality model. The BOOT evaluation framework (Chang and Hanna 2005) was used to statistically evaluate the performance of the air quality model through comparisons of predicted and observed pollutant concentrations. The model was found to significantly over-predict and under-predict concentrations of nitrogen dioxide (NO) and particles with a diameter of less than ten microns (PM) at seven and five 210 monitoring locations across Leicester. A discussion of the sources of error in prediction was presented. The base-case was edited to reflect a change in emissions abatement technology, fuel or vehicle and emissions were recalculated. In addition, a vehicle kilometres travelled (VKT) restriction was imposed on the vehicle fleet that did not allow any increase in VKT from the base year. The changes to the base-case were made in increments of 5% until 100% was reached. Regression analysis was used to create 13 models that allowed the impact of the road transport strategies on CO and pollutant 2 emissions to be explored. A reduction in both CO and toxic air pollutant emissions (‘win-win’) was found when the penetration 2 of zero emissions vehicles (ZEVs) and plug-in hybrid electric vehicles (PHEVs) to the car fleet was modelled. Overall, the highest reduction in toxic pollutant and CO emissions were found for ZEVs, 2 which represent electric vehicles (EVs) under current legislation. A 53% (or greater) penetration of ZEVs to the car fleet was the only strategy for which a 50% reduction in CO for a 1990 base was 2 found. Therefore, this indicates that substantial and arguably radical changes are required if air quality and climate change limit values and targets to be achieved. A win-win for air quality and climate change was found when new emissions abatement technology was introduced into the car fleet. However, greater pollutantemissions reductions were observed with the introduction of new emissions abatement technology to light goods vehicle (LGV) and heavy goods vehicle (HGV) stocks. These strategies were found to have a negligible impact on CO 2 emissions. Consequently a trade-off was found where a ‘win-win’ was achieved through changes to the car fleet but at the cost of higher pollutant emissions reductions from other strategies. The introduction of new emissions abatement technology to the bus fleet on roads predominantly on key traffic corridors within Leicester’s air quality management area (AQMA) resulted in substantial air quality benefits. The same strategy did not result in a reduction in CO emissions. However, in the 2 context of an overall sustainable transport strategy the benefits of increasing bus patronage, which in turn may reduce the number of single occupancy vehicles on the road, is likely to have a more than compensatory effect. Substantial pollutant emissions reductions were found as a result of the introduction of new emissions abatement technology into the HGV and LGV fleets. However, these strategies were found to have negligible CO emissions reductions and therefore did not provide a win-win for air quality and climate change. Similarly, a win-win from the introduction of LPG to the car fleet was not found. Therefore, the uptake of LPG or investment in the introduction of new emissions abatement technology to the LGV or HGV fleets should only be considered as a part of a sustainable policy package that comprises other measures, such as logistics optimisation or a reduction in VKT. The findings of this research were used to inform a set of policy actions for Leicester City Council.
8

Development of biosensors and chemical sensors for the determination of metals in water and soil extracts

Rodriguez, Belen Bello January 2004 (has links)
No description available.
9

Bioengineering transgenic plants to detoxify nitroaromatic explosive compounds

Lorenz, Astrid January 2007 (has links)
No description available.
10

The control of combustion and pollutant emissions of pulverised fuel flames through the implementation of fuzzy logic based embedded reasoning

Zaidi, Syed Azhar Mehdi January 2002 (has links)
No description available.

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