Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000. / Oxygen transport across biofilms and membranes may be a limiting factor in the operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in which fungi are immobilized within the wall of a porous polysulphone capillary membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide) were investigated in a bare membrane (without a biofilm being present). The work provides a basis for further transport study in membranes where biomass is present. The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet membranes. The diaphragm-cell method employs two well-stirred compartments separated by the desired membrane to be tested. The membrane is maintained horizontally. -The gas (solute) concentration in the lower compartment is measured versus time, while the concentration in the upper liquid-containing compartment is maintained at a value near zero by a chemical reaction. The resistances-in-series model can be used to explain the transfer rate in the system. The two compartments are well stirred; this agitation reduces the resistances in the liquid boundary layers. Therefore it can be assumed that in this work the resistance in the membrane will be dominating. The method was evaluated using oxygen as a test. The following factors were found to influence mass transfer coefficient: i) the agitation in the two compartments; ii) the concentration of the reactive solution and iii) the thickness of the membrane.

Thesis (DTech (Chemical Engineering))--Cape Peninsula University of Technology, 2009. / Includes bibliographical references. Also available online.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 173 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 138-142).

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xiii, 112 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 92-94).

published_or_final_version / abstract / toc / Civil Engineering / Doctoral / Doctor of Philosophy

Thesis submitted in fulfilment of the requirements for the degree DOCTOR TECHNOLOGIAE: ENGINEERING: CHEMICAL In the FACULTY OF ENGINEERING At the CAPE PENINSULA UNIVERSITY OF TECHNOLOGY 2009 / The white rot fungus, Phanerochaete chrysosporium strain BKMF-1767 (ATCC 24725), produces the extracellular enzymes, Lignin peroxidase (LiP) and Manganese peroxidase (MnP), that constitute the major route for lignin degradation by this organism. LiP and MnP have also been shown to play a major role in aromatic pollutant degradation. Due to the need for continuous production of LiP and MnP, a fixed-film bioreactor, classified as a membrane gradostat reactor (MGR), was developed. The implementation of batch-reactor operational parameters to the MGR system was found to be ineffective, thus creating the need for further research to improve the operational aspects of the MGR system to optimise its capabilities for continuous and industrial-scale operations. The research undertaken in this study, provides information that can be used to classify the dissolved oxygen (DO) transport kinetics into immobilised fixed-films of P. chrysosporium. Operational limitations of the MGR relating to environmental stresses in the bioreactor during operation and to biofilm deterioration, including limitations of DO mass transport, oxidative stress, trace element accumulation and polysaccharide storage in the fungal biomass, were evaluated in single capillary MGR systems (SCMGRs). These conditions were identified as existing in the continuous MGR systems. From DO profiles, the oxygen consumption and flux into the biofilms, including the distribution of DO, was determined to be dependent on the immobilised biofilm’s age. Younger biofilms showed higher DO distribution than older biofilms even when aeration was directed to the extracapillary space (ECS) of the reactor against the biofilm’s surface. An increase in anaerobic zone thickness was observed to be increasing with an increase in biofilm thickness. Although, DO kinetic parameters were comparable with those obtained in submerged mycelia pellets, higher oxygen consumption values were observed in biofilms grown in the SCMGRs. The limitations of MGR were identified as: 1) poor DO distribution in immobilised biofilms because of b-glucan production and storage in the immobilised biomass, resulting in ethanol production; 2) the peroxidation of lipids of the biofilms, which in turn will affect the long-term performance of the biomass caused by oxygenation and 3) trace element ion accumulation enhanced by b-glucan production. Furthermore, trace element ion accumulation was higher in the MGRs than in batch cultures using the same nutrient medium. The development of a perfluorocarbon (PFC) emulsion for the MGRs to counteract these limitations was investigated. The compatibility of the emulsion with oxygen-carrying capacity was shown with an improvement in biomass generation, LiP/MnP production and overall consumption of primary substrates, mainly glucose and ammonium tartrate, in batch cultures. The emulsions investigated were based on the addition of oxygen carriers: Perfluorooctyl bromide (PFOB), Bis-(Perfluorobutyl) ethene (PFBE) and Perfluoropropylamine (PFPA), using Pluronic F 68 (PF 68) as the surfactant. Concentrations of 10 to 30% (w/v) PFC and 8.5% (w/v) PF 68 were tested successfully in batch cultures. The emulsions containing 10% (w/v) PFCs resulted in improved biomass performance as opposed to emulsions with higher PFC oil concentrations. An emulsion containing 10% (w/v) PFOB was used to evaluate its efficacy in the SCMGRs, as the biomass yield and overall enzyme production were superior to PFPA and PFBE-based emulsions with similar oil concentrations. After successfully applying PFOB and PF 68 to the SCMGRs, the following results were obtained: 1) reduced ethanol production; 2) reduced trace element accumulation; 3) lower b-glucan production and 4) improved DO-penetration ratio in immobilised biofilms.

Submitted in fulfillment of the academic requirements for the Master’s Degree in Technology: Chemical Engineering, Durban University of Technology. Durban. South Africa, 2015. / Increased public concern over health and the environment, the need to expand existing wastewater treatment plants due to population increase, and increasingly stringent discharge requirements, have created a need for new innovative technologies that can generate high quality effluent at affordable cost for primary and secondary re-use. The membrane biological reactor (MBR) process is one of the innovative technologies that warrant consideration as a treatment alternative where high quality effluent and/or footprint limitations are a prime consideration. MBR processes have been applied for the treatment of industrial effluent for over ten years (Harrhoff, 1990). In this process, ultrafiltration or microfiltration membranes separate the treated water from the mixed liquor, replacing the secondary settling tanks of the conventional activated sludge process. Historically, energy costs associated with pumping the treated water through the membranes have limited widespread application for the treatment of high volumes of municipal wastewater. However, recent advancements and developments in membrane technology have led to reduced process energy costs and induced wider application for municipal wastewater treatment (Stephenson et al., 2000). This report describes a small and pilot scale demonstration study conducted to test a woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) process for use in domestic wastewater treatment. The study was conducted at Durban Metro Southern Wastewater Treatment Works, Veolia Plant, South Africa. The main objective of this project was to develop and evaluate the performance of an aerobic woven fabric microfiltration immersed membrane bioreactor (WFM-IMBR) for small scale domestic wastewater treatment. The experiments were oriented towards three sub objectives: to develop the membrane pack for immersed membrane bioreactor based on WF microfilters; to evaluate the hydrodynamics of WF membrane pack for bioreactor applications; and to evaluate the long-term performance and stability of WFM-IMBR in domestic waste water treatment. The literature was reviewed on membrane pack design for established commercial IMBR. The data collected from literature was then screened and used to design the WF membrane pack. Critical flux was used as the instrument to measure the WF membrane pack hydrodynamics. Long-term operation of the WFM-IMBR was in two folds: evaluating the performance and long term stability of WFM-IMBR. The membrane pack of 20 flat sheet rectangular modules (0.56 m by 0.355 m) was developed with the gap of 5 mm between the modules. The effects of parameters such as mixed liquor suspended solids or aeration on critical flux were examined. It was observed that the critical flux decreased with the increase of sludge concentration and it could be enhanced by improving the aeration intensity as expected and in agreement with the literature. Hence the operating point for long term subcritical operation was selected to be at a critical flux of 30 LMH and 7.5 L/min/module of aeration. Prior to the long term subcritical flux of WFM-IMBR, the operating point was chosen based on the hydrodynamic study of the WF membrane pack. The pilot scale WFM-IMBR demonstrated over a period of 30 days that it can operate for a prolonged period without a need for cleaning. Under subcritical operation, it was observed that there was no rise in TMP over the entire period of experimentation. Theoretically this was expected but it was never investigated before. Good permeate quality was achieved with 95% COD removal and 100% MLSS removal. The permeate turbidity was found to be less than 1 NTU and it decreased with an increase in time and eventually stabilized over a prolonged time. Woven fibre membranes have demonstrated great potential in wastewater treatment resulting in excellent COD and MLSS removal; low permeate turbidity and long term stability operation. From the literature surveyed, this is the first study which investigated the use of WF membranes in IMBRs. The study found that the small scale WFM-IMBR unit can be employed in fifty equivalence person and generate effluent that is free of suspended solids, having high levels of solid rejection and has acceptable discharge COD for recycle. Future work should be conducted on energy reduction strategies that can be implemented in WFM-IMBR for wastewater treatment since high energy requirements have been reported by commercial IMBRs.

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2006. / Recent advances in inorganic material preparation for membrane fabrication have extended the use of membranes to high temperature and chemically harsh environments. This has allowed inorganic membranes to be integrated into catalytic reactors, resulting in the concept known as Catalytic Membrane Reactors (CMRs). CMRs have overall important benefits of product quality, plant compactness, environmental impact reduction and energy savings. It has found use in a broad range of applications including biochemical, chemical, environmental and petrochemical systems. In these CMRs, the membranes perform a variety of functions, and consequently they are categorized according to the primary role of the membrane: extractor, distributor or contactor. In this dissertation the different uses of an extractor Catalytic Membrane Reactor (eCMR) are evaluated with the help of model reactions. In the eCMR the primary function of the membrane is to selectively extract one of the reaction products from the reaction zone, thereby combining the benefits of separation and reaction in one unit operation. This can lead to a number of advantages, of which the two most important ones include: (a) conversion beyond thermodynamic equilibrium in equilibrium restricted reactions and/or (b) the improvement of product selectivity in consecutive/parallel reaction networks. The dehydrogenation of isobutane, an equilibrium restricted reaction, was evaluated in a dense Palladium and a MFI-zeolite/alumina composite eCMR. These two eCMRs, consisting of a membrane packed with a Pt/In/Ge-MFI-zeolite catalyst, differed only on the basis of the membrane used. The palladium membrane showed superior extraction and selectivity capability for hydrogen in the reaction mixture compared to the MFI/alumina composite membrane. Regardless of these facts, the performances of the Pd and MFI eCMR, when evaluated at the same reaction conditions, were similar. The isobutane conversion to isobutene, employing high sweep rates (185 ml/min) could be increased up to ca. 37 % at 723 K, compared to 14 % in the conventional packed-bed reactor. The similar performance of the two different eCMRs was evaluated using a Catalytic Membrane Reactor model. Model results showed that in order for the extractortype CMR to completely draw benefit from the combination of membrane and catalyst in the same unit for conversion enhancement, a very active catalyst should be developed, able to sustain the high extraction ability of the membrane. This was the first time that these two eCMRs were evaluated at similar reaction conditions in order to study the influence of the nature of the membrane material on the working of the eCMR. The eCMR was also used to carry out meta-xylene isomerization. This part focused on the extraction of para-xylene from the meta-xylene isomerization reaction zone with a MFI eCMR (MFI-zeolite membrane and Pt-HZSM5 fixed-bed catalyst) in order to improve the reaction selectivity towards para-xylene. Para-xylene is an important industrial chemical used as a precursor for polyester resin, and in order to meet the paraxylene demand, ortho- and meta-xylenes are converted via the xylene isomerization reaction to xylene isomers. It has been shown that the pore-plugged MFI-zeolite membranes used in this study can selectively extract para-xylene from a mixture of xylenes. Using an extractor type catalytic membrane reactor instead of a conventional fixed-bed reactor for meta-xylene isomerization, can lead to higher para-xylene selectivities. The para-xylene selectivity can even be improved to 100% if the CMR is operated in the permeate-only mode, but this comes at a price of lower para-xylene yields. When operated in combined mode (i.e. mixing both permeate and retentate streams after the reactor), the CMR shows an improvement on both para-xylene productivity (ca. 10 % maximum at conditions studied) and selectivity when compared to the conventional reactor. This is the first time paraxylene selectivity could successfully be improved by employing an extractor Catalytic Membrane Reactor. This dissertation also led to the design and construction of a new generation membrane reactor testing bench, a first in the Department of Process Engineering, University of Stellenbosch. The bench allows for high temperature evaluation of membranes and Catalytic Membrane Reactors. The design is simple and easily adaptable for use to evaluate various different reactions.

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2000. / Stricter government regulations and higher energy costs have forced the chemical industry to focus more on environmentally friendly processes and to reduce energy consumption. The main goals of chemical companies are to obtain a high product yield and selectivity, and to reduce unwanted side products. Furthermore, if ractions can be performed at lower temperature, while maintaining the reaction conversion, it will result in large energy savings. Low termperature dehydrogenation reactions (below 300 degrees C) are very selective and do not produce many by-products, but conversion is limited by the reaction equilibrium. The conversion limitations have resulted in the development of alternative processes in recent years for producing alkenes from alkanes and aldehydes or ketones from alcohols....