Ph.D., Faculty of Science, University of the Wiwatersrand, 2011 / Biological production of hydrogen gas has received increasing interest from the international community during the last decade. Most studies on biological fermentative hydrogen production from carbohydrates using mixed cultures have been conducted in conventional continuous stirred tank reactors (CSTR) under mesophilic conditions. Investigations on hydrogen production in reactor systems with attached or self-immobilized microbial growth have also appeared recently in the literature. These investigations on attached or self-immobilised bacteria involve hydrogen production in the mesophilic and thermophilic temperature range. The present study investigated the design and operational features of anaerobic fluidized granular bed bioreactor (AFGB) system which would facilitate the simultaneous achievement of high productivities (HPs) and high hydrogen yields (HYs).Where high HPs is greater than 120 mmol H2 /(L.h) and HYs greater than 4 mol H2/mol glucose. Theoretical maximum yield for an exponentially growing non-granulated bacterial monoculture will always be less than the thermodynamic maximum of 4 mol H2 /mol glucose: C6H12O6 +4H2O → 2CH3COO- + 4H2 + 4H+ + 2HCO3. The design features included reducing the total non-working or dead volume of bioreactor system. The operational improvements included application of thermophilic temperatures and high rates of de-gassed effluent recycling through the fluidized granular bed. An example of an optimal ratio of effluent recycle rate (R) to bioreactor working volume (V) was (3.0 L/min)/(3.2 L/min) = 0.94 minutes. Under conditions where temperatures were maximised and V/R were minimized the HPs increased to 21.58 L H2 /h. Also under these conditions the HYs increased above 3.0 mol H2/mol glucose. Specific hydrogen productivity for the fluidized granular bed increased from 0.25 L H2 / (g BM.h) or 8.83 mmol H2 / (g BM.h) at 45 oC to 0.525 L H2 / (g BM.h) or 18.03 mmol H2 / ( g BM.h) at 70 oC. A 3.64 fold increase in hydrogen yield occurred with an increase in temperature from 45 oC to 70 oC. XX When expressed in terms of glucose, this represents an increase from 1.34 mol H2 /mol glucose to 4.65 mol H2 /mol glucose. Finally, an evaluation of the net energy production by the AFGB system revealed a positive energy balance, making thermophilic biohydrogen production energetically viable from a commercial perspective.

Este projeto de pesquisa visou à investigação do desempenho do reator UASB (10 L de volume) no tratamento da vinhaça quando submetido a aumento progressivo da carga orgânica em condições termofílicas. A carga orgânica afluente média foi de 2,79 gDQO/L.dia (desvio de 1,5 gDQO/L.dia) e média efluente bruto de 1,24 gDQO/L.dia (desvio de 0,93 gDQO/L.dia). A operação atingiu o limite de carregamento de 6,5 gDQO/L.dia, limitado pela produção excessiva de ácidos voláteis totais que atingiram concentrações da ordem de 1.200 mgHac/L, tóxicas para biomassa metanogênica. A adaptação do lodo mesofílico às condições termofílicas ocorreu no período de 55 dias, que pode ser considerado um período curto. A operação com ácidos orgânicos para enriquecimento do lodo não se mostrou eficaz, com acúmulo desses ácidos para a COV de 10 gDQO/L.dia. A operação com etanol mostrou-se eficaz para a recuperação do lodo, com COV de 8,0 gDQO/L.dia, obtendo-se eficiência máxima de remoção de DQO de 80%. As eficiências máximas na operação foram durante a adaptação do lodo, com COV de 1,20 gDQO/L.dia (92,0%) e durante a operação do sistema, com COV de 3,50 gDQO/L.dia (83,0%). O TDH médio desenvolvido neste trabalho foi de 1,34 dias. Este dado levantou questionamentos a respeito de um TDH ótimo utilizado para este tipo de tratamento, devido a grande variação de TDHs encontrados na literatura em trabalhos correlatos (entre 1,0 e 6,5 dias). / This research project had the objective to investigate the performance of the UASB reactor (10 L of volume) in the vinasse treatment submitted to progressive organic loadings under thermophilic conditions. The organic matter upload average was 2,79 gDQO/L.day (standard deviation of 1,5 gDQO/L.day) and the full organic matter average was 1,24 gDQO/L.dia (standard deviation of 0,93 gDQO/L.day). The operation reached the organic limit loading in 6,5 gCOD/L.day, limited by the excessive production of total volatile acids that reached concentrations beyond 1.200 mgHac/L, toxic to metanogenic biomass. Adaptation of mesophilic sludge to thermophilic conditions occurred in a period of 55 days, what can be considered a short period. The operation with organic acids for sludge enrichment did not seem to be efficient, accumulating these acids in a 10 gCOD/L.day. The operation with ethanol seemed to be efficient for sludge recuperation, of 8,0 gCOD/L.day, reaching maximum COD reduction efficiencies of 80%. The maximum operation efficiency was during sludge adaptation with 1,20 gCOD/L.day (92,0%) and during operation system, with 3,50 gCOD/L.day (83%). The HDT average developed in this research was 1,34 days. These data bring questions about the HDT optimum for this kind of anaerobic treatment, in correlation with significant variation of HDT used in another studies in the literature (between 1,0 and 6,5 days of HDT).

Composting has been practiced for thousands of years as a way of stabilizing and recycling organic matter into useful soil amendments. Thermophilic compost releases significant amounts of heat at temperatures (~140 °F) that are useful for environmental heating or process water. This heat has been taken advantage of in various ways throughout history, but development of a widely adopted technology remains elusive. The biggest barrier to adoption of compost heat recovery (CHR) systems is projecting accurate, attractive economic returns. The cost of transfer equipment is significant, and with variability in composting substrates and methods, it is difficult to predict the power and quality of heat a proposed system would produce. While the ultimate heat release may be calculated with standard techniques, the dynamics of compost temperature and thermal power are less understood. As heat yield is one of many goals, better understanding of compost’s thermal dynamics is important for CHR optimization. This research addresses the issue by developing a field test that measures heat release and temperature across a representative-scale compost volume. The compost test vessel was built from common construction materials and insulated enough to be self-heating in cold weather. A 4’ x 4’ x 4’ cube of 2” foam insulation panels held 1.812 cubic yards of active compost, intermittently aerated at ~35 CFM. Data from 84 temperature sensors, and one pressure sensor at the blower, was logged at 1-minute intervals for a period of 35 days. Spatial temperature fields were estimated by Kriging, and used to calculate conductive heat loss and compost volume temperature over time. Enthalpy loss was calculated using the blower pressure curve, temperature data and humidity assumptions. The compost exhibited wide variation in temperature and heat flow over time, and less horizontal symmetry than expected. The results are dynamic and best viewed graphically. Enthalpy loss varied with adjustments to the aeration cycle, ranging from 100 to 550 W (60-minute average rates), while conductive losses were in the range of 75 W. Peak sustained thermal output was around 600 W (500 W by aeration) from days 11-13 with about 0.6 yd3 of compost in the thermophilic zone; however, this cooled the compost significantly. Aeration was then reduced, and the compost temperature recovered, with 50% - 90% of the compost volume above 130 °F from days 14-23; during this period, total heat loss was around 150 - 200 W with aeration loss around 60-100 W. The test was successful in producing hot compost and building temperature field and heat loss models. However representative aeration rates cooled a large amount of the compost volume as cool air was drawn into the vessel. Aeration rate reduction accomplished desired compost temperatures, but resulted in low enthalpy extraction rate and temperature. Future work will address this issue with the ability to recirculate air through the compost.

The microbial ecology of 45 high temperature (> 50 ° C) petroleum reservoirs was investigated by isolating and characterizing bacteria that were present in their produced fluids. Initial work was aimed at selecting a suitable high temperature petroleum reservoir for the study of natural microbial populations. Experimental work then focussed on establishing the physico-chemical conditions that prevail in the selected reservoir and on developing media and enrichment conditions for the isolation of microorganisms indigenous to the reservoir. The ability of reservoir bacteria to grow and survive under the physical and chemical conditions found in the selected reservoir was used to assess the likelihood of an indigenous origin for these bacteria. The petroleum reservoir selected for study was the Alton petroleum reservoir (SW Queensland, Australia). It was established that most of the physico-chemical conditions in the Alton reservoir had remained unchanged since oil recovery began. The stability of redox conditions (90 mV) in the reservoir over its operating life was identified as an important factor in the coexistence of strict aerobic and strict anaerobic bacterial populations within the reservoir. An important change that has occurred in the Alton reservoir over its operating life because of oil recovery was an increase in water pH from 6.41 to 8.42 as a result of carbon dioxide loss (1.36 atm to 0.0134 atm) from the reservoir. Development of novel enrichment procedures that simulated Alton reservoir conditions led to the isolation of previously unreported aerobic and anaerobic populations of thermophilic bacteria. The aerobic bacteria isolated were identified as either endosporeforming heterotrophic bacteria from the genus Bacillus or nonspore-forming heterotrophic bacteria resembling members of the genus Thermoleophilum. All aerobes grew on carbon sources such as acetate and n-heptadecane that are normal constituents of the reservoir. The anaerobic bacteria isolated were characterized as sheathed fermentative bacteria from the order Thermotogales or non-sheathed fermentative bacteria. In parallel studies, the natural microbial populations in other reservoirs were investigated and I concluded that fermentative microorganisms were common inhabitants of high temperature petroleum reservoirs. The isolation of fermentative bacteria from these high temperature petroleum reservoirs established that fermentative bacteria are a fourth major microbial group, together with hydrocarbon-oxidizers, sulphate-reducers and methanogens, to be reported in petroleum reservoirs. The fermentative bacteria use organic nutrients and carbohydrates, but not contemporary crude oil as the principal nutrient source within reservoir waters. The thermophilic bacteria isolated from Alton petroleum reservoir demonstrated growth characteristics such as temperature (optima 50-70 ° C and range 37-85 ° C), pH (optima 6.0-9.0 and range 5.0-9.0 and salinity (optima 0-15 g per litre and range 0-30 g per litre), that were consistent with conditions encountered in the Alton reservoir (temperature 75 � C, pH 8.5 and TDS 2.7 g per litre). The isolated bacteria also demonstrated a number of characteristics that might enable them to survive adverse conditions that could be encountered in a petroleum reservoir environment. The characteristics that contribute to aerobic bacteria surviving in and overcoming periods of oxygen limitation include well-documented processes such as sporulation, by Bacillus spp., and microaerophily. The characteristics that contribute to fermentative bacteria surviving were: (1) a natural tolerance to reservoir physico-chemical fluctuations, (2) an ability to remain viable when metabolic activity was suppressed to very low rates by the growth-limiting conditions imposed, and (3) possible formation of viable ultramicrobacteria (UMB). Formation of UMB (bacteria smaller than 0.3 |im) by thermophilic bacteria has not been reported previously. The recovery of thermophilic UMB by filtration from the Alton reservoir water indicates that these bacteria occur in natural habitats. This study found the formation of thermophilic UMB and their survival characteristics differed considerably from that reported for the mesophilic, marine bacterium Vibrio sp. DWI. Unlike mesophilic marine bacteria, thermophilic bacteria did not always respond to nutrient deprivation by forming UMB and that these UMB did not show any increased ability to survive in the face of adverse conditions. Although the formation of UMB as part of routine cell growth and division was not demonstrated directly in this study, circumstantial evidence suggests that they form part of a natural life cycle. The exact conditions that result in UMB formation and their role in survival remain unresolved. The capacity of nonspore-forming indigenous populations from Alton to survive sudden shifts in environmental conditions that might result from common oilfield operations was poor. Such operations were demonstrated to be inhibitory or lethal to Alton reservoir bacteria. It also was concluded that such oilfield operations suppress indigenous microbiota. However, the impacts of most oilfield operations within a reservoir are likely to be confined to the immediate area surrounding injection and producing wells. Minimizing the localized effects of oilfield practices on indigenous reservoir populations will lead to the better management of undesirable microbial activity in reservoirs such as H2S formation (souring) and facilitate development of better microbially mediated oil recovery process. This study showed that selected reservoir isolates possess characteristics which are suitable for in situ biotechnological applications such as microbially enhanced oil recovery (MEOR). Characteristics favourable for enhanced oil recovery include a capability for UMB formation, which would enable better dispersion, and resistance to high concentrations of reservoir components such as calcium, magnesium, strontium, heavy metals and hydrocarbons.

Graduation date: 1994

<p>To ensure the sustainability of bioethanol production, major attention has been directed to develop feedstocks which provide an alternative to food-crop biomass. Lignocellulosic (LC) biomass, which is chiefly composed of industrial plant residues, is a carbon-rich reservoir that is presently attracting much attention. However LC material is highly recalcitrant to bioprocessing and requires a mixture of physical and enzymatic pretreatment in order to liberate fermentable sugars. Thermostable enzymes are extremely desirable for use in thermophilic fermentations due to their inherent stability. Hemicellulose, a core constituent of LC, requires a cascade of hemicellulases to stimulate the depolymerisation of its xylan backbone. &alpha / -L-arabinofuranosidase (AFase) increases the rate of lignocellulose biodegradation by cleaving arabinofuranosyl residues from xylan thereby increasing the accessibility of other hemicellulases. Twenty thermophilic Actinomycete isolates were screened for AFase activity using pnp-arabinofuranoside as the substrate. Three strains (ORS #1, NDS #4 and WBDS #9) displayed significant AFase activity and were identified as Streptomyces species with 16S rRNA gene sequence analysis. Genomic DNA was isolated from these strains and a cosmid library constructed in the shuttle vector pDF666. Subsequent functional and PCR-based screening revealed no positive clones.</p>

<p>To ensure the sustainability of bioethanol production, major attention has been directed to develop feedstocks which provide an alternative to food-crop biomass. Lignocellulosic (LC) biomass, which is chiefly composed of industrial plant residues, is a carbon-rich reservoir that is presently attracting much attention. However LC material is highly recalcitrant to bioprocessing and requires a mixture of physical and enzymatic pretreatment in order to liberate fermentable sugars. Thermostable enzymes are extremely desirable for use in thermophilic fermentations due to their inherent stability. Hemicellulose, a core constituent of LC, requires a cascade of hemicellulases to stimulate the depolymerisation of its xylan backbone. &alpha / -L-arabinofuranosidase (AFase) increases the rate of lignocellulose biodegradation by cleaving arabinofuranosyl residues from xylan thereby increasing the accessibility of other hemicellulases. Twenty thermophilic Actinomycete isolates were screened for AFase activity using pnp-arabinofuranoside as the substrate. Three strains (ORS #1, NDS #4 and WBDS #9) displayed significant AFase activity and were identified as Streptomyces species with 16S rRNA gene sequence analysis. Genomic DNA was isolated from these strains and a cosmid library constructed in the shuttle vector pDF666. Subsequent functional and PCR-based screening revealed no positive clones.</p>

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [87]-101).

Thesis (Ph.D.)--North Carolina State University. / Includes vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Stephen Craig Cary, College of Earth, Ocean, & Environment. Includes bibliographical references.