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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.
271

Digestive Tracts: Early Modern Discourses of Digestion

Purnis, Jan 05 December 2012 (has links)
This project explores early modern conceptualizations of the body, offering a cultural history of the belly. I apply the tools of literary, historico-cultural, and discourse analysis to textual depictions of the digestive organs and the processes of digestion they perform. Concentrating particularly on the nexus of body, culture, and language, and continuously foregrounding the material underpinnings of linguistic expression, I argue that representations of the digestive organs serve to naturalize ideology and that digestion is itself an apt metaphor for the processes by which ideology is internalized. In my first chapter, I argue that the stomach is a central site through which hierarchies of gender are expressed and assimilated. I analyze Shakespeare’s The Taming of the Shrew in the context of early modern cultural metaphors associated with the stomach and in the context of medical theories of digestion, according to which hotter male digestion is superior to colder female digestion. Drawing upon Marx’s economic theory and his less-noted physiological rhetoric, in Chapter Two I trace how increasing commodity exchange and concomitant changes to social relations are reflected in, and promoted by, a paradigm shift in medical interpretations of the physiological functions of the liver. Chapter Three offers a more detailed and literary analysis of this process, demonstrating how Spenser’s allegory of the body in Book Two of The Faerie Queene participates directly in the ideological work necessary for the transition to capitalism by naturalizing the consumption and production of commodities driving it. The focus of Chapter Four is on the use of bodily metaphors of excretion in colonialist propaganda to legitimate the enforced migration of those described as England’s “excrements” to the colonies. Influenced by Norbert Elias’s theory of the “civilizing process,” I read these metaphors in light of altering social attitudes towards literal excrement, and I demonstrate how representations of the body’s excretory organs in Phineas Fletcher’s The Purple Island mirror the social processes of the “civilization” and discipline of self, nation, and Other.
272

Digestive Tracts: Early Modern Discourses of Digestion

Purnis, Jan 05 December 2012 (has links)
This project explores early modern conceptualizations of the body, offering a cultural history of the belly. I apply the tools of literary, historico-cultural, and discourse analysis to textual depictions of the digestive organs and the processes of digestion they perform. Concentrating particularly on the nexus of body, culture, and language, and continuously foregrounding the material underpinnings of linguistic expression, I argue that representations of the digestive organs serve to naturalize ideology and that digestion is itself an apt metaphor for the processes by which ideology is internalized. In my first chapter, I argue that the stomach is a central site through which hierarchies of gender are expressed and assimilated. I analyze Shakespeare’s The Taming of the Shrew in the context of early modern cultural metaphors associated with the stomach and in the context of medical theories of digestion, according to which hotter male digestion is superior to colder female digestion. Drawing upon Marx’s economic theory and his less-noted physiological rhetoric, in Chapter Two I trace how increasing commodity exchange and concomitant changes to social relations are reflected in, and promoted by, a paradigm shift in medical interpretations of the physiological functions of the liver. Chapter Three offers a more detailed and literary analysis of this process, demonstrating how Spenser’s allegory of the body in Book Two of The Faerie Queene participates directly in the ideological work necessary for the transition to capitalism by naturalizing the consumption and production of commodities driving it. The focus of Chapter Four is on the use of bodily metaphors of excretion in colonialist propaganda to legitimate the enforced migration of those described as England’s “excrements” to the colonies. Influenced by Norbert Elias’s theory of the “civilizing process,” I read these metaphors in light of altering social attitudes towards literal excrement, and I demonstrate how representations of the body’s excretory organs in Phineas Fletcher’s The Purple Island mirror the social processes of the “civilization” and discipline of self, nation, and Other.
273

Anaerobic Digestion of Corn Ethanol Thin Stillage for Biogas Production in Batch and By Downflow Fixed Film Reactor

Wilkinson, Andrea 10 June 2011 (has links)
Anaerobic digestion (AD) of corn thin stillage (CTS) offers the potential to reduce corn grain ethanol production energy consumption. This thesis focuses on results collected from AD of CTS at mesophilic temperatures in batch and by down-flow fixed film reactor. Experiments conducted include a series of biochemical methane potential (BMP) assays that investigated the digestion of CTS as the sole carbon source at a variety of food-to- microorganism ratios with and without acclimated biomass, under co-digestion conditions and also with the addition of supplemental nutrients. Additional BMP assays were conducted which investigated the potential to reduce fresh water consumption by using of digested effluent for substrate dilution. Continuous studies employed two 28L down-flow stationary fixed film reactors to examine. Chemical oxygen demand and volatile solids removal efficiencies greater than 85% were achieved up to an organic loading rate of 7.4 g TCOD/L/d and hydraulic retention time of 5 days.
274

Characterization of Pretreatment Impacts on Properties of Waste Activated Sludge and Digestibility

Kianmehr, Peiman January 2010 (has links)
Technologies for pretreatment of waste activated sludges (WAS) prior to digestion are of increasing interest to wastewater treatment utilities because of their promise for improving sludge digestibility and reducing the mass of biosolids remaining after digestion. While there has been considerable study of pretreatment processes, a common approach to describing the impact of pretreatments on sludge biodegradability has not been developed. The overall objective of this study was to develop protocols that can be employed to characterize the impact of pretreatment processes on WAS digestion. Sonication and ozonation were employed as models of physical and chemical pretreatment technologies respectively. A range of physical, chemical and biological responses were evaluated to assess the impact of pretreatment on WAS properties as well as digestibility. WAS samples that were generated over a range of solids residence times (SRTs) under controlled operating conditions were employed to facilitate an assessment of the interaction between pretreatment and WAS properties on digestibility. The VS, COD and soluble TKN responses indicated that a significant fraction of the WAS solids were solublized by sonication and ozonation, however, it appeared that the types of materials which were solublized was affected by the SRT at which the WAS was generated and the level of pretreatment. The results indicated that the impact of pretreatment on biodegradability of WAS was not described by solublization values exclusively without considering the SRT of the sludge and the level and type of pretreatment. A higher level of proteinaceous materials was preferentially solublized as the result of pretreatment. Respirometry revealed that both sonication and ozonation substantially reduced the viable heterotrophs in the sludge and modestly increased the readily biodegradable fraction of COD. The ultimate yields of CH4 and NH4 in BMP tests and VFAs in BAP tests revealed that pretreatment marginally increased the ultimate digestibility of the sludges. Only a high dose of ozonation substantially increased the digestibility of the 15 day SRT sludge. However, both sonication and ozonation substantially increased the rate of hydrolysis which is typically the rate limiting process in WAS digestion. The BMP test was not a useful test to evaluate the rate of methane generation due to inhibition of methanogens in the early days of BMP test for pretreated sludges. The comparison between VFA and ammonia responses in day 10 of BAP test and ultimate values of these responses after 60 days in BMP test revealed linear relationships between these responses. According to these relationships, a set of models were introduced in this study. The models can be employed to predict the ultimate methane and ammonia generation using soluble COD, VFA or ammonia responses in day 10 of BAP tests. The BAP test was determined to be a shorter test (10 days) than the BMP (55 to 60 days) test and could provide information on the rates of hydrolysis and acidification/ammonification processes. Characterization of biodegradable and non-biodegradable material in WAS samples was conducted using a simplified ADM1 model. The characterization also revealed that proteins are a substantial fraction of biodegradable materials. The estimated ammonia, VFA and methane values from the stoichiometric model were similar to the corresponding values from the experiments. This supported the validity of the simplified model for all sludges employed in this study.
275

Enzymatic treatement of wastewater sludge in presence of a cation binding agent : improved solubilisation and increased methane production

Beijer, Ronja January 2008 (has links)
Stockholm Water is a water and sewage company with Henriksdal as one of two wastewater treatment plants (WWTPs). At Henriksdal wastewater sludge generated in the wastewater treatment process is digested which generate biogas; a mixture of mainly methane and carbon dioxide. If purified to methane content of 96 - 98 % this gas is called biomethane. Biogasmax is a project aiming to reduce the use of fossile fuels in Europe by providing that biogas is a good technical, economical and environmental alternative as vehicle fuel. The specific aim for Stockholm Water is to increase the biogas production at the existing plant in Henriksdal. Enzymatic treatment of wastewater sludge is an innovative technique earlier proofed to increase the biogas production from wastewater sludge with up to 60 %. The enzyme activity is in turn proven to significantly increase in the presence of a cation binding agent. One aim with this thesis was to investigate if the sludge from Henriksdal wastewater treatment process at all is affected of enzymatic treatment in presence of a cation binding agent since this has shown to have some significance. The chemical oxygen demand (COD) was measured in the liquid phase of sludge after treatment and used as a measurement of treatment effect. Another aim of this thesis was to look into the possibility to increase the methane production from sludge at Henriksdal WWTP. This was investigated through batch laboratory digestion tests. The sludge from Henriksdal WWTP was shown to be a good substrate for the enzymes added. COD in the liquid phase was increased with 17 – 32 % depending on the dose of enzymes and sodium citrate added. Digestion of sludge with a total addition of 18.6 mg enzymes per 1 g total solids (TS) and a concentration of 5 mM sodium citrate increased the methane production with almost 18 % compared to untreated sludge. This equals an increase of 18.3 % when converted to represent a totally blended and continuous digestion chamber at Henriksdal WWTP. The increased methane production also results in a sludge reduction out from the digestion chambers. The increased methane production and sludge reduction though does not fulfil the increased costs for the enzymes and sodium citrate applied. These doses must be decreased and the costs for both enzymes and sodium citrate must be reduced for this technique to be economically feasible in a full scale operation.
276

Different Pretreatments to Enhance Biogas Production : A comparison of thermal, chemical and ultrasonic methods

Wang, Liqian January 2011 (has links)
No description available.
277

Mechanism of zeolite activity in biogas co-digestion

Hansson, Anna January 2011 (has links)
Biogas is a source of renewable energy and is produced at anaerobic conditions. The gas consists mainly of methane (55-70 %) and carbon dioxide (30-45 %). Biogas can be used as vehicle fuel after the gas has been upgraded to a methane content of approximately 97 %. There are several companies in Sweden producing biogas. Svensk biogas AB in Linköping is one of the largest. The company has two biogas production plants; one in Linköping and one in Norrköping. To meet the surge demand for biogas it is not only important to increase the volumetric capacity of the digesters, but also to optimize the process at the existing production plants in different ways. Zeolites, a clay mineral, have earlier been shown to have a positive effect on anaerobic digestion of certain substrates. The aim of this master’s thesis was to investigate if the organic loading rate could be increased and/or if the hydraulic retention time could be reduced by addition of zeolites to a reactor treating slaughterhouse waste as a substrate. The aim was further to investigate which substance/substances that zeolites possibly could affect. Addition of the zeolite clinoptilolite in a continuously stirred lab tank reactor showed a significantly lower accumulation of volatile fatty acids compared to that in a control reactor without zeolites added, when the hydraulic retention time was kept low (30 days) and the organic loading rate was high (4.8 kg VS/ (m3 × day)). The same results were observed upon zeolite addition in a batch experiment, which also showed a decreased lag phase. Neither the specific gas production nor the methane concentration was significantly affected by addition of zeolites. Furthermore, addition of a possible inhibitor, long-chain fatty acids (LCFA), increased the lag phase further when slaughterhouse waste was used as a substrate. The conclusion from the observed results is that a metabolite or metabolites produced during the anaerobic degradation is/are the reason to inhibition and an increased lag phase.
278

The Biogas Production Plant at Umeå Dairy — Evaluation of Design and Start-up

Asplund, Stina January 2005 (has links)
As a part of a large project at Norrmejerier, a biogas production plant has been constructed at Umeå Dairy. In this plant wastewater, residual milk and whey are decomposed and biogas is produced. The biogas is burned in a steam boiler. The biogas plant is designed as an anaerobic contact process, with sludge separation and recirculation by a clarifier. The fat in the substrate is treated in a separate reactor. The purpose of this study is to evaluate the design and start-up of this biogas production plant. Further, the interaction with the contractor responsible for construction and start-up is evaluated. The plant is generally well designed, the process conditions are suitable and the objectives are realistic. However, the seed sludge is unsuitable and the time plan is too optimistic. At the end of the period of this study, the plant was running and all central components are performing as intended. Still, the objectives have not been reached. This is mainly attributed to the poor quality of the seed sludge. The management of the plant and the interaction with the contractor has generally been good. Most problems that arose were of typical start-up nature. Others were due to insufficient planning or lack of communication. Further, several design flaws were identified during start-up. Washout of sludge has been one of the most significant drawbacks during start-up. This inconvenience seems to be the result of improper seed sludge and a too hasty increase of the organic loading rate. / Norrmejerier har som en del av ett större projekt låtit uppföra en anläggning för biogasproduktion vid Umeå mejeri. I anläggningen, som är utformad som en anaerob kontaktprocess, behandlas avloppsvattnen och andra organiska restprodukter från mejeriet tillsammans med vassle från både Umeå och Burträsk mejeri. Fettet i substratet avskiljs och behandlas separat. Den biogas som produceras vid nedbrytningen av det organiska materialet bränns i en brännare och ånga produceras. Syftet med den här studien är att utvärdera anläggningens design, valda processförhållanden och förfarandet under uppstarten av biogasanläggningen. Dessutom utvärderas interaktionen med den tyska entreprenör som är ansvarig för konstruktion och uppstart. Anläggningens utformning och valda processbetingelser är passande och de uppsatta målen är rimliga. Däremot är valet av ymp olämpligt och tidsplanen för uppstarten är för optimistisk. När denna studie avslutades var anläggningen i bruk och biogas producerades. Alla de mål för som formulerats hade dock inte uppnåtts. Ympens dåliga kvalitet är den mest bidragande orsaken till att uppstartsperioden har blivit förlängd. Arbetet under uppstarten och samarbetet med entreprenören har generellt sett varit lyckat. Man har dock stött på många komplikationer, varav de flesta har varit av typisk uppstartsnatur. Andra har varit resultatet av bristande planering och kommunikation. En rad konstruktions- och designfel har också identifierats under uppstarten. Slamflykt från reaktorerna har varit det mest betydande problemet hos den biologiska processen. Denna förlust av slam förmodas bero på olämpligt val av ymp och en alltför hastig ökning av den organiska belastningen i reaktorerna under uppstarten.
279

Characterization of Pretreatment Impacts on Properties of Waste Activated Sludge and Digestibility

Kianmehr, Peiman January 2010 (has links)
Technologies for pretreatment of waste activated sludges (WAS) prior to digestion are of increasing interest to wastewater treatment utilities because of their promise for improving sludge digestibility and reducing the mass of biosolids remaining after digestion. While there has been considerable study of pretreatment processes, a common approach to describing the impact of pretreatments on sludge biodegradability has not been developed. The overall objective of this study was to develop protocols that can be employed to characterize the impact of pretreatment processes on WAS digestion. Sonication and ozonation were employed as models of physical and chemical pretreatment technologies respectively. A range of physical, chemical and biological responses were evaluated to assess the impact of pretreatment on WAS properties as well as digestibility. WAS samples that were generated over a range of solids residence times (SRTs) under controlled operating conditions were employed to facilitate an assessment of the interaction between pretreatment and WAS properties on digestibility. The VS, COD and soluble TKN responses indicated that a significant fraction of the WAS solids were solublized by sonication and ozonation, however, it appeared that the types of materials which were solublized was affected by the SRT at which the WAS was generated and the level of pretreatment. The results indicated that the impact of pretreatment on biodegradability of WAS was not described by solublization values exclusively without considering the SRT of the sludge and the level and type of pretreatment. A higher level of proteinaceous materials was preferentially solublized as the result of pretreatment. Respirometry revealed that both sonication and ozonation substantially reduced the viable heterotrophs in the sludge and modestly increased the readily biodegradable fraction of COD. The ultimate yields of CH4 and NH4 in BMP tests and VFAs in BAP tests revealed that pretreatment marginally increased the ultimate digestibility of the sludges. Only a high dose of ozonation substantially increased the digestibility of the 15 day SRT sludge. However, both sonication and ozonation substantially increased the rate of hydrolysis which is typically the rate limiting process in WAS digestion. The BMP test was not a useful test to evaluate the rate of methane generation due to inhibition of methanogens in the early days of BMP test for pretreated sludges. The comparison between VFA and ammonia responses in day 10 of BAP test and ultimate values of these responses after 60 days in BMP test revealed linear relationships between these responses. According to these relationships, a set of models were introduced in this study. The models can be employed to predict the ultimate methane and ammonia generation using soluble COD, VFA or ammonia responses in day 10 of BAP tests. The BAP test was determined to be a shorter test (10 days) than the BMP (55 to 60 days) test and could provide information on the rates of hydrolysis and acidification/ammonification processes. Characterization of biodegradable and non-biodegradable material in WAS samples was conducted using a simplified ADM1 model. The characterization also revealed that proteins are a substantial fraction of biodegradable materials. The estimated ammonia, VFA and methane values from the stoichiometric model were similar to the corresponding values from the experiments. This supported the validity of the simplified model for all sludges employed in this study.
280

Modeling Volatile Organic Sulfur Compounds In Anaerobic Digestion

Du, Weiwei January 2010 (has links)
Anaerobic digestion is a common process for treatment of wastewater sludge from municipal sewage systems. Volatile sulfur compounds, including volatile organic sulfur compounds (VOSCs) and hydrogen sulfide, have been reported as the most odorous compounds in digestion emissions and impurities which can damage facilities for generation, transportation, storage, and utilization of biogas. There has been no comprehensive study on biological generation and degradation kinetics of VOSC or modeling VOSC behaviors through anaerobic sludge digestion. The goal of the present study was to establish a model for VOSC conversions in anaerobic sludge digestion which could facilitate quantitative analysis of VOSC emissions in anaerobic digestion. VOSCs and methionine were employed in dosed batch tests. VOSC conversion processes in anaerobic methionine digestion have been identified. The kinetics for the identified VOSC degradation and conversion processes were determined at 35 and 55 °C respectively. Mixed-second order kinetics were found to best fit the conversion processes. A model was established based on the identified processes and estimated kinetic constants. To extend the model to VOSC release in anaerobic sludge digestion, mesophilic and thermophilic incubations were conducted with four different sludge samples. The effects of temperature and sludge source on VOSC release patterns were assessed. It was found that an unidentified DMS generation mechanism was triggered in the mesophilic incubation of activated sludge in which iron was dosed. To apply the model which was established based on methionine degradation in sludge digestion, hydrolysis of particulate materials was incorporated. The model simulations for VOSC behavior in thermophilic batch incubation were able to represent the observed VOSC releases. However, the simulations could not well fit the observed VOSC release at 35 ° because the model did not include the unidentified DMS generation mechanism. Application of the model to bench-scale digesters was lack-of-fit. It may have been due to imprecise estimation of the degradable sulfur in the feed sludge. In addition, in the batch tests and digester operation the ratios of the raw and digested sludge were different. This might have resulted in different concentrations of the microorganisms which mediated biotransformations and hence resulted in different kinetic constants.

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