Dissertations / Theses on the topic 'Bioreactors'

Three membrane bioreactors, a low flux filter (LFF), a diafilter (DF), and an ion-exchange (IE) membrane bioreactor were used to treat water polluted with 50 ppm-N nitrate. The three systems were compared in terms of removal efficiency of nitrate, operational complexity, and overall quality of the treated water. In the low flux filter (LFF) membrane bioreactor an hemo-dialysis hollow fiber module was used and operated continuously for 29 days with a constant flux of permeate. The performance of the system was constant during the span of the experiment, which demonstrated that when the module was operated under constant low flux of permeate, the membrane filtration process was not affected by fouling. The removal rate of the LFF was 100% since the treated effluent did not contain nitrate or nitrite. The volumetric denitrification rate was 240 g-N day-1 m-3, which is within the range of denitrification rates obtained in tubular membrane modules. The treated effluent contained acetate, the carbon source of the biological process, and other inorganic nutrients, which showed that operating this ultrafiltration module at controlled flux did not improve the retention of these substances in the bioreactor. The same hemo-dialysis hollow fiber module employed in the LFF system was used in the diafilter (DF) membrane bioreactor. In the DF system, however, the membrane module was used as a contactor that separated the treated water and the bioreactor system, which allowed the transfer of solutes through the membrane porous structure and supported the growth of a biofilm on the membrane surface. The nitrate removal rate of the DF system increased from 76% to 91% during the 17 days assay. Unfortunately, this improvement could be attributed to microbial contamination of the water circuit because significant concentrations of the carbon source, acetate, nutrients, and nitrate were found in the treated effluent. The volumetric denitrification rate of the system was 200 g-N day-1 m-3, and the surface denitrification rate was lower than values previously reported for contactor membrane bioreactors. The results hereby presented do not evidence any advantage of operating the Filtral 20 ® membrane module as a contactor instead of as a filter such as in the LFF system. On the other hand, the third system herein presented, the IE membrane bioreactor, demonstrated several advantages of a contactor configuration but with a non-porous ion exchange membrane module in place of the Filtral 20 ®. As in a contactor system, the anion membrane provided a surface for biofilm growth, facilitated the transport of nitrate, and prevented mixing of treated water and bioreactor medium. Compared to the two previous systems, the most remarkable result of the IE was the reduction of secondary pollution in the treated water. The concentrations of phosphate and ethanol were zero and less than 1% of the concentration in the bioreactor, respectively. In addition, the IE system was less complex than the two other systems because the ion exchange membrane is non-porous. Therefore, unlike with porous contactors, it was not necessary to control the flux of treated water that could be lost through the bioreactor. The average surface denitrification rate of the IE system was 7.0 g-N day-1 m-2, which is higher than what had been reported for other contactor denitrification systems. However, because of the low surface to volume ratio of the membrane module that was used, the volumetric denitrification rate of the IE system was low, equivalent to 65 g-N day-1 m-3.
Master of Science

Low solubility of oxygen has resulted in high bioreactor energy requirements in order to supply sufficient oxygen to aerobic bioprocesses. It is desirable to reduce energy consumption in bioreactors to benefit environmental sustainability as well as economic feasibility. This is particularly important with the resurgence of interest in bio-based commodity products. Some research has suggested that venturi aeration of bioreactors will reduce energy consumption by eliminating the need for air compression, while at the same time maintaining or improving oxygen transfer rates. On the other hand, there are findings that suggest venturi aeration has lower energy efficiency than conventional sparging and oxygen transfer rates achieved are too low sustain aerobic biological processes. A comparison of the aeration of geometrically-similar reactors using the same analytical methods to determine kLa is not available in the literature. This comparison should also address analysis of energy input including energy used for compressing gas sparged into a stirred tank reactor; the investigation of mass transfer rates at higher flow rates (vvm) in venturi-aerated reactors and resulting cell response to these higher flow rates. This is the topic of the dissertation presented. In this laboratory scale study, venturi aerators were characterised and energy consumption as a function of oxygen mass transfer rates compared with a geometrically identical aerated stirred tank reactor by evaluating the volumetric mass transfer coefficients (kLa). The kLa was investigated in varying reactor setups using the dynamic gassing-in method.

The combination of two membrane technologies coupled together in series has become a standard technology when it comes to producing reclaimed water of high quality for potable reclamation or industrial applications. This combination of two membrane processes is referred to as integrated membrane systems (IMS). Despite the widespread experience gained utilizing such a process technology around the world, there are a number of aspects of the process technology which require further investigation including the fate of compounds of emerging concern (CEC), the control of N-Nitrosodimethylamine (NDMA) formation, the use of energy associated with the process and the total cost of producing the reclaimed water, and monitoring membrane integrity in RO treatment processes. The objective of this work was to further the knowledge in one aspect related to each of these four challenges and then bring each of these areas together in the discussion to understand whether proposing a decision support system for the online monitoring and operation of integrated systems would allow improvements to the current state-of-the-art.
La combinació de dos tecnologies de membrana acoblades en sèrie ha esdevingut un tecnologia consolidada degut a la capacitat de produir aigua d’elevada qualitat i potencialment reutilitzable per aplicacions industrials com fins i tot per ser potabilitzada. Tot i l’elevada experiència adquirida en aquests processos combinats, encara hi ha aspectes del procés que calen una investigació més profunda que inclogui el coneixement sobre l’eliminació dels compostos emergents, el control de la formació de N-Nitrosodimetilamines (NDMA), l’ús de l’energia associada amb el procés incloent el cost total de produir l’aigua reutilitzable, i el seguiment de la integritat de la membrana en el tractament amb osmosi inversa (OI). L’objectiu d’aquest treball recau en avançar en el coneixement dels aspectes relacionats amb cada un dels quatre reptes esmentats, per aconseguir discutir de forma conjunta la millor forma d’integrar aquest nou coneixement adquirit proposant un sistema d’ajuda a la decisió pel control i seguiment de l’operació de sistemes integrats de membrana (SIM).

Nitrate is practically ubiquitous in waters abstracted for municipal potable water production in Europe due to decades of intensive agricultural practice. Ion exchange is principally selected to target abstracted waters with elevated nitrate concentrations. However, the cost associated with disposal of the waste stream has re-ignited interest in destructive rather concentrative technologies. This thesis explores the potential of membrane bioreactor (MBR) technology for the removal of nitrate from potable water. Two configurations are considered: an MBR to replace ion-exchange completely; and an MBR to treat the ion-exchange waste stream in-situ for re-use. For the replacement MBR, permeate quality can be affected by nitrite accumulation, micro-organism and carbon breakthrough. However, at steady-state and provided substrate addition was controlled, permeate quality was consistently high. Selection of an appropriate substrate was observed to improve permeability by a factor of three. Permeability was sustained within the MBR by adopting a dead-end filtration strategy having identified a relationship between filtered volume, flux and suspended solids concentration. Provided the filtered volume within a single filtration cycle did not exceed a set volume, the accumulated deposit was reversible. For the ion-exchange waste stream MBR, organic carbon breakthrough was considerable. However, the impact upon resin capacity was apparently limited when permeate was re-used for resin regeneration. Salt shocking did not induce permeability decline although some denitrification capacity was lost. Cost evaluation demonstrated that operating ion- exchange in parallel with MBR regenerant treatment was more cost effective than ion exchange with direct disposal.

La producció de proteïnes recombinants en plantes representa una oportunitat per a la seva obtenció i utilització comercial. L'objectiu principal d'aquesta tesi industrial ha estat el desenvolupament de sistemes vegetals de producció de proteïnes, eficients i competitius econòmicament, amb possibilitats de portar-les al mercat. Per fer-ho hem explorat dos sistemes: els cultius cel·lulars de Daucus carota i les fulles de Nicotiana benthamiana, cadascun d'ells amb els seus avantatges i limitacions. Com a prova de concepte, ambdós sistemes van ser utilitzats per a la producció d'"insulin-like growth factor 1" (IGF1), un pèptid d'alt valor afegit per a les indústries cosmètica i farmacèutica. S'assajaren vàries estratègies innovadores per a millorar els rendiments de producció augmentant l'expressió gènica i reduir costos de purificació del producte. A més, l'activitat biològica de l'IGF1 i els seus derivats produïts en planta va ser avaluada en comparació amb pèptids sintètics. Com a primera estratègia s'assajaren supressors del silenciament de l'ARN d'origen viral per tal d'incrementar l'expressió gènica. En assajos d'expressió transitòria amb la proteïna verda fluorescent com a marcadora, seleccionàrem la proteïna P1b del ipomovirus Cucumber vein yellowing virus (CVYV). Els nostres resultats amb línies cel·lulars de pastanaga sobreexpressores de l'IGF1 o el seu pèptid derivat CPP-IGF1 (variant dissenyada per a millorar la seva penetració en cèl·lules humanes) mostraren que en combinació amb P1b s'arribava a rendiments de producció 4 vegades majors que les línies sense el supressor del silenciament. A més, els pèptids foren dirigits al medi de cultiu per facilitar el seu aïllament mitjançant una simple clarificació. En assajos d'activitat, les fraccions obtingudes confirmaren ser capaces d'incrementar la divisió de fibroblasts humans. En relació amb l'estabilitat de la producció, s'observà una reducció propera al 33% després de vint-i-un cicles de propagació successius, per la qual cosa s'implementà la criopreservació de les línies transgèniques per mantenir els rendiments de producció originals, i així establir bancs cel·lulars per usos futurs. Alhora, es desenvolupà un sistema de producció transitòria de l'IGF1 i el CPP-IGF1 en fulles de N. benthamiana utilitzant un vector derivat del virus del mosaic del tabac, Tobacco mosaic virus (TMV). Aquest sistema va permetre reduir el temps d'obtenció del pèptid actiu, encara que en comparació amb la producció a les línies cel·lulars l'obtenció del producte no fou tan senzilla. Per tal de facilitar la purificació de l'IGF1 a partir de les matrius vegetals, aplicàrem una estratègia innovadora basada en fusions a oleosina per dirigir la producció a cossos lipídics. Aquesta tecnologia ja havia estat utilitzada en llavors, però no en cultius cel·lulars i escassament en fulles. Les nostres observacions mostraren la presència d'abundants cossos lipídics en nombrosos cultius cel·lulars incloent-hi els de D. carota amb l'excepció de les dues espècies model analitzades, Nicotiana tabacum i Arabidopsis thaliana. Desafortunadament, l'expressió estable de fusions a l'oleosina sembla que va afectar greument al creixement dels calls cel·lulars, pel que s'exploraren alternatives de la seva aplicació a la producció en fulles. Per tal d'augmentar la quantitat de cossos lipídics, la producció de les fusions a l'oleosina es realitzà simultàniament amb la d'inductors de l'acumulació de triacilglicerols utilitzant elements clau de la seva ruta biosintètica en A. thaliana: l'enzim DGAT1 i el factor de transcripció WRI1. Quan ambdós inductors foren co-expressats en combinació amb fusions a oleosina i l'IGF1 en plantes de N. benthamiana, es va obtenir fins 1 μg/g d'IGF1 unit als cossos lipídics, fàcilment aïllable i actiu. El nostre treball proporciona evidències que la utilització de supressors del silenciament de l'ARN, els vectors virals i la tecnologia de les oleosines contribueixen al potencial de les matrius vegetals per a la producció de proteïnes d'interès.
La producción de proteínas recombinantes en plantas representa una oportunidad para su obtención y uso comercial. El objetivo principal de esta tesis industrial ha sido el desarrollo de sistemas vegetales de producción de proteínas, eficientes y competitivos a nivel económico, con posibilidades de llevarlas al mercado. Para ello hemos explorado dos sistemas: los cultivos celulares de Daucus carota y las hojas de Nicotiana benthamiana, cada uno con sus ventajas y limitaciones. Como prueba de concepto, ambos sistemas fueron utilizados para la producción de “'insulin-like growth factor 1” (IGF1), un péptido de alto valor añadido para las industrias cosmética y farmacéutica. Se ensayaron varias estrategias innovadoras para mejorar los rendimientos de producción aumentando la expresión génica y para reducir costes de purificación del producto. Además, la actividad biológica de IGF1 y sus derivados producidos en plantas se evaluó en comparación con péptidos sintéticos. Como primera estrategia se ensayaron supresores del silenciamiento de ARN de origen viral para incrementar la expresión génica. En ensayos de expresión transitoria con la proteína verde fluorescente como marcadora, seleccionamos la proteína P1b del ipomovirus Cucumber vein yellowing virus (CVYV). Nuestros resultados con líneas celulares de zanahoria sobreexpresoras de IGF1 o su péptido derivado CPP-IGF1 (variante diseñada para mejorar su penetración en células humanas) mostraron que en combinación con P1b alcanzaban rendimientos de producción 4 veces mayores que las líneas sin el supresor del silencing. Además, los péptidos fueron dirigidos al medio de cultivo para facilitar su aislamiento por simple clarificación. En ensayos de actividad, las fracciones obtenidas confirmaron ser capaces de incrementar la división de fibroblastos humanos. En relación a la estabilidad de la producción, se observó una reducción cercana al 33% después de veintiún ciclos de propagación sucesivos, por lo que se implementó la criopreservación de las líneas transgénicas para mantener los rendimientos de producción originales, y así establecer bancos de líneas celulares para usos futuros. También se desarrolló un sistema de producción transitoria de IGF1 y CPP-IGF1 en hojas de N. benthamiana utilizando un vector derivado del virus del mosaico del tabaco, Tobacco mosaic virus (TMV). Este sistema permitió reducir el tiempo de obtención del péptido activo, aunque en comparación con la producción en líneas celulares la obtención del producto no fue tan sencilla. Con el fin de facilitar la purificación de IGF1 desde matrices vegetales, aplicamos una estrategia innovadora basada en fusiones a oleosina para dirigir la producción a cuerpos lipídicos. Esta tecnología ya había sido utilizada en semillas, pero no en cultivos celulares, y escasamente en hojas. Nuestras observaciones mostraron la presencia de abundantes cuerpos lipídicos en numerosos cultivos celulares, incluyendo los de D. carota, con la excepción de las dos especies modelo analizadas, Nicotiana tabacum y Arabidopsis thaliana. Desafortunadamente, la expresión estable de fusiones a oleosina pareció afectar gravemente el crecimiento de los callos celulares, por lo que se exploró la alternativa de su aplicación a la producción en hojas. Para aumentar la cantidad de cuerpos lipídicos, la producción de las fusiones a oleosina se realizó simultáneamente con inductores de la acumulación de triacilgliceroles, usando elementos clave de su ruta biosintética en A. thaliana: la enzima DGAT1 y el factor de transcripción WRI1. Cuando ambos inductores fueron co-expresados en combinación con fusiones de oleosina e IGF1 en plantas de N. benthamiana, se obtuvo hasta 1 μg/g de IGF1 unida a los cuerpos lipídicos, fácilmente aislable y activo. Nuestro trabajo proporciona evidencias de que la utilización de supresores del silenciamiento de ARN, los vectores virales y la tecnología de oleosinas contribuyen al potencial de las matrices vegetales para la producción de proteínas de interés.
The production of proteins in plant cell cultures and whole plants represents great opportunities to develop products for commercial use. The main objective of this industrial thesis was to develop economic and efficient plant production systems to bring proteins of interest to the market. We explored two different systems, Daucus carota cell cultures and Nicotiana benthamiana leaves, each having advantages and drawbacks depending on the intended use of the products. As a proof of concept, both systems were applied in the production of the human insulin-like growth factor 1 (IGF1), a high value peptide for the cosmetic and therapeutic industries. Innovative strategies to enhance gene expression and to facilitate product purification were used to improve yields and to reduce costs. Moreover, the biological activity of the produced IGF1 and derivatives was evaluated and compared to the chemically synthesized peptides to demonstrate the usefulness of production systems. Our first approach to enhance gene expression and improve peptide yields was with RNA silencing suppressors (RSSs). Using transient expression assays and the green fluorescent protein (GFP) as reporter, we selected the P1b from the Cucumber vein yellowing virus (CVYV) Ipomovirus as the RSSs to enhance gene expression in carrot cell cultures. Our results demonstrated that transgenic lines overexpressing IGF1 or the derivative CPP-IGF1 (a variant tailored to enhance the delivery to human cells) reached up to 4-fold higher peptide yields in combination with P1b than without. The IGF1 or CPP-IGF1 was targeted to the culture media being easily purified by simple clarification of suspensions. Moreover, we found that the media containing the produced IGF1 or CPP-IGF1 stimulated the division of human fibroblasts. A cryopreservation process was applied to the transgenic lines to avoid the reduction in peptide production found over successive propagation cycles. This allowed us to recover the original yields, opening up the possibility of establishing master cell banks. We also developed a transient production system of IGF1 and CPP-IGF1 using N. benthamiana leaves and a derived tobacco mosaic virus vector. This system resulted in similar yields of active peptides to cell cultures with the main advantage of shortening production times, although requiring more complex downstream purification. Our innovative strategy to facilitate the purification of IGF1 from plant matrices was the use of oleosin fusion technology for lipid droplet (LDs) targeting. This technology has been previously used in LD-rich seeds, but unexplored in plant cell cultures or LD-poor tissues such as leaves. Our work showed that model cell cultures from Nicotiana tabacum or Arabidopsis thaliana were an exception, as many other plant cell cultures, including D. carota cells, do contain a large number of LDs and are susceptible to produce oleosin fusion proteins. However, as the stable expression of oleosin fusions severely affected callus cell growth, we tested the technology in transient expression in leaves. Due to the low level of LDs in leaves, oleosin fusion proteins production was in combination with triacylglycerol (TAG) induction to increase LD content simultaneously. For this purpose, key components of the TAG biosynthetic pathway, A. thaliana derived elements such as the enzyme DGAT1 and the regulatory factor WRI1 were co-expressed with the IGF1 oleosin fusion proteins in N. benthamiana leaves. Using this strategy, we obtained yields up to 1 μg/g of IGF1 bound to LDs, easily purified and fully active. Our work provides evidence of the potential of plant matrices to produce valuable peptides. Also, the oleosin technology, the use of RSSs and viral vectors explored will serve to overcome some of the known limitations of plant systems to produce active products of industrial interest.

Anaerobic treatment of municipal wastewaters or other wastewaters of weaker strength has conventionally been difficult, especially in regions of cooler climate. Issues with solids retention and sufficient biomass concentration and activities required for treatment are usually of primary concern in these situations. However, the recent incorporation of membranes in the anaerobic treatment of municipal wastewater has made this technology feasible through the absolute retention of biomass within the reactor. Among the many advantages this technology has over its aerobic membrane bioreactor (MBR) counterpart, the most attractive may be the absence of an energy requirement for aeration. Although the anaerobic membrane bioreactor (AnMBR) is a promising technology, limited understanding of the interactions between the reactor biomass and the filtration membranes in the AnMBR has generally confined it to the lab scale level. To this end, the subject of examination for this study is the feasibility of AnMBR treatment of municipal wastewaters, with a strong focus towards membrane operation at moderate operating temperatures. Two experiments were conducted during this study. The first was the long-term operation of two commercially available membranes (hollow fibre and flat sheet) operated in parallel within the reactor. The achievable operational OLR range for the AnMBR was about 1.25 kg COD/m³-d. COD removal efficiency for the AnMBR system during biomass acclimatization was 84% with the addition of supplemental acetate in the feed. This decreased to 43% after the removal of supplemental acetate at a reactor temperature of 25 °C. Biogas production of the system decreased by 20% subsequent to a temperature decrease of 5 °C, due likely to decreased methanogenic activities. The second experiment was to assess the mechanism(s) of membrane flux decline and to compare them with mechanisms identified for the same membranes applied in an aerobic MBR system. The major difference between filtration of the aerobic and anaerobic mixed liquor was the membrane surface cake layer fouling. The observed anaerobic mixed liquor resistance was nearly 100 times greater than the aerobic contribution. It was observed that the mechanism of flux decline of the organic membrane in an anaerobic environment was due to surface cake layer fouling.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

The performance of a submerged membrane bioreactor for the duty of gas field produced water treatment was appraised. The system was operated under steady state conditions at a range of mixed liquor suspended solids (MLSS) concentrations and treatment and membrane performance examined. Organics removal (COD and TOC) display removal rates between 90 and 97%. Removal of specific target compounds Benzene, Toulene, Ethylbenzene and Xylene were removed to above 99% in liquid phase with loss to atmosphere between 0.3 and 1%. Comparison of fouling rates at a number of imposed fluxes has been made between long term filtration trials and short term tests using the flux step method. Produced water fed biomass displays a greater fouling propensity than municipal wastewater fed biomass from previous studies. Results indicate an exponential relationship between fouling rate and flux for both long and short term trials, although the value was an order of magnitude lower during long term tests. Moreover, operation during long term trials is characterised by a period of pseudo stable operation followed by a catastrophic rise in TMP at a given critical filtration time (tfi, ) during trials at 6 g. L"1. This time of stable operation, tfit, is characterised by a linear relationship between fouling rate and flux. Results have been compared with the literature. Data for membrane fouling prior to the end of t fit yielded a poor fit with a recently proposed model. Trends recorded at t> trlt revealed the fouling rate to follow no definable trend with flux. The system showed resilience to free oil shocking up to an oil concentration of 200ppmv. Following an increase in oil concentration to 500 ppmv, rapid and exponential fouling ensued.

Anaerobic treatment has historically been considered unsuitable for the treatment of domestic wastewaters. The work presented in this thesis focuses on the incorporation of membranes into the anaerobic bioreactor to uncouple solid retention time and hydraulic retention time. This in turn prevents biomass washout and allows sufficient acclimatisation periods for anaerobes. However, the exposure of membranes to anaerobic biomass comes with its own inherent problems namely fouling. Fouling was found to take place in two stages; a rapid phase characterised by solid and bacterial cell deposition and a slow phase characterised by the travel of colloidal matter to the membrane surface. Gas sparging was also found to attenuate fouling to a considerable extent despite the fact that biomass characteristics were critical factors in the fouling of the system. In addition, side stream membranes showed differing characteristics to submerged membranes. A comparison of anaerobic membrane bioreactors to conventional anaerobic systems and aerobic membrane bioreactors highlighted the advantage of this system over other comparable technologies. The anaerobic membrane bioreactor is less energy intensive than the aerobic membrane bioreactor, fouls differently to this system and achieves much better performance than would be seen if conventional anaerobic systems were used in the treatment of domestic or municipal wastewaters.

Membrane bioreactors (MBRs) show great promise for productivity improvement and energy conservation in conventional bioprocesses for wastewater reclamation. In order to attain high productivity in a bioprocess, it is crucial to retain the microorganisms in the bioreactors by preventing wash out. This enables recycling of the microorganisms, and is consequently saving energy. The main feature of MBRs is their permeable membranes, acting as a limitative interface between the medium and the microorganisms. Permeation of nutrients and metabolites through the membranes is thus dependent on the membrane characteristics, i.e. porosity, hydrophilicity,and polarity. The present thesis introduces membranes for MBRs to be used in a continuous feeding process, designed in the form of robust, durable, and semi-hydrophilic films that constitute an effective barrier for the microorganisms, while permitting passage of nutrients and metabolites. Polyamide 46 (polytetramethylene adipamide), a robust synthetic polymer, holds the desired capabilities, with the exception of porosity and hydrophilicity. In order to achieve adequate porosity and hydrophilicity, bulk functionalization of polyamide 46 with different reagents was performed. These procedures changed the configuration from dense planar to spherical, resulting in increased porosity. Hydroxyethylation of the changed membranes increased the surface tension from 11.2 to 44.6 mJ/m2. The enhanced hydrophilicity of PA 46 resulted in high productivity of biogas formation in a compact MBR, due to diminished biofouling. Copolymerization of hydrophilized polyamide 46 with hydroxymethyl 3,4-ethylenedioxythiophene revealed electroconductivity and hydrophilic properties, adequate for use in MBRs. To find either the maximal pH stability or the surface charge of the membranes having undergone carboxymethylation, polarity and the isoelectric point (pI) of the treated membranes were studied by means of a Zeta analyzer. The hydroxylated PA 46 was finally employed in a multilayer membrane bioreactor and compared with hydrophobic polyamide and PVDF membranes. The resulting biogas production showed that the hydroxylated PA 46 membrane was, after 18 days without regeneration, fully comparable with PVDF membranes.

MBR process consists of a suspended growth biological reactor combined with a membrane unit. The widespread of this system for waste water treatment is contained by membrane fouling, which is strongly influenced by three factors: biomass characteristics, operating conditions and membrane characteristics. Fouling control techniques mainly include low-flux operation (sub-critical flux operation) and/or high-shear slug flow aeration in submerged. configuration. Based on the concept of the critical flux (Jo), the flux-step method has been developed to more fully characterise transmembrane pressure (TMP) behaviour during constant-fluxoperation. A zero rate of TMP increase was never attained during the trial, such that no critical flux, in its strictest definition, could be defined in this study for a submerged MBRs challenged with real and simulant sewage. Under similar operating conditions, Jc was obtained around 18 and 10 L.m-2.h-1 for a submerged MBR fed by real and synthetic sewage respectively. Three TMP-based parameters have been defined, all indicating the same flux value at which fouling starts to be more significant (the weak form of Jo). Results from factorial experimental designs revealed the relative effect of MLSS levels, aeration rate and membrane pore size on J, The MLSS effect on Jc was generally around double that of the aeration effect. The calculation of mean sub-critical values for the different TMP-based parameters suggest lower short-term fouling resistance for large pore sized membranes. A direct comparison between the two MBR configurations revealed a greater J, for the submerged compared to the SS MBR (22 and 11 L.m-2.h-1 respectively) under similar hydraulic conditions. The fluid hydrodynamics has been studied for both configurations, leading to an accurate calculation of shear at the membrane surface in SS MBR and to the determination of the minimum gas velocity required for Taylor bubble formation in submerged MBR (around 0.1 m.s-1). Finally, the effect of operating conditions such as process configuration, feed nature, and aeration type on biomass characteristics has been assessed and link to membrane fouling. Key words: Fouling, MBR, critical flux, process configuration, biomass characterisation.

Thesis (Ph. D.)--Ohio State University, 2003.
Title from first page of PDF file. Document formatted into pages; contains xiv, 113 p.; also includes graphics Includes bibliographical references (p. 84-87). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--Washington State University, August 2009.
Title from PDF title page (viewed on Aug. 3, 2009). "School of Chemical Engineering and Bioengineering." Includes bibliographical references.

En un reactor anaeróbico de lecho empacado y de flujo ascendente con carbón activado (AC) biológico se obtuvieron altas velocidades de conversión del colorante azoico Acid Orange 7 a tiempos espaciales muy cortos, hasta 99% en 2.0 min. Tanto el área superficial específica como la conductividad electrónica del AC contribuyeron a las mayores velocidades de reducción. La agitación en el lecho de carbón produjo un incremento de la bioconversión del colorante. Se estableció un modelo cinético de decoloración que implica catálisis heterogénea y bioreducción. La biodegradabilidad anaeróbica de un colorante azoico en el sistema reactivo agitado pudo ser predicha a partir de su potencial de reducción. Las velocidades de decoloración fueron significativamente influenciadas por las propiedades texturales del AC y moderadamente afectadas por su química superficial. Este bioreactor catalítico parece ser una alternativa atractiva para la mejora económica de las tecnologías de tratamiento de aguas residuales textiles y de colorantes.
In an anaerobic upflow packed-bed reactor with biological activated carbon (AC), high azo dye Acid Orange 7 conversion rates were achieved during very short space times up to 99% in 2.0 min. Both electron conductivity and specific surface area of AC contributed to higher reduction rates. The application of stirring in the carbon bed resulted in an increase of dye bioconversion. A decolourisation model was developed involving both heterogeneous catalysis and bioreduction. The anaerobic biodegradability of an azo dye could be predicted by its reduction potential in the stirred reactor system. The decolourisation rates were found to be significantly influenced by the textural properties of AC and moderately affected by its surface chemistry. This catalytic bioreactor system seems to be an attractive alternative for economically improving textile/dye wastewater technologies.

Bioartificial Liver (BAL) is a term for medical devices designed to replace natural liver functions. The idea behind the use of artificial livers is to either externally support an injured liver to recovery or bridge a patient with a failing liver to transplantation. Central to all BAL systems is a bioreactor for culturing liver cells. The main function of this reactor is to provide a cell adhesion matrix and supply the necessary nutrient solution. A high cellular oxygen uptake rate combined with low solubility in aqueous media makes oxygen supply to the liver cells the most constraining factor in current reactor designs. Devices with parallel-plate channel geometry promise high efficiency for blood detoxification and liver metabolism. However, due to their specific flow regime oxygen depletion in the medium is a major problem in these devices. This thesis explores a unique method of controlling and measuring dissolved oxygen in BAL cell-culture bioreactors and lab-on-a-chip devices. Testing is performed using simulations, prototype bioreactor devices and in-vitro measurement of dissolved oxygen. Several strategies developed to fabricate the bioreactors and integrate oxygen sensing are presented. Emphasis is placed on techniques that provide compatibility with commonly used microfabrication processes, while allowing for laterally-resolved measurement of oxygen in a re-usable, low-cost setup. The most significant contribution presented is the development and assessment of the tapered cell-culture bioreactor with integrated PtOEPK/PS oxygen sensor. The combination adopts a unique approach to oxygen control. Bioreactor shape is used to modulate the oxygen supplied to cells via the resulting shear-stress function. By linearly increasing the shear-stress oxygen concentration can be maintained constant over the length of the reactor. Using the integrated oxygen sensor, the resulting concentration profile can be monitored in real-time with high lateral resolution. The advantage of the device over existing techniques is that no additional oxygenation inside the reactor chamber is required to maintain a certain concentration profile and that oxygen concentration can be mapped in-situ without having to introduce further chemicals into the perfusion medium. This thesis presents a number of other contributions: a grayscale mask process, development of the PtOEPK/PS sensor patterning method and signal optimization regime, demonstration of the multi-stream flow application, an experimental setup for sensor calibration and a process to pattern cell-adhesion proteins simultaneously with the oxygen sensor, a multi-layer BAL prototype and the results of a brief experiment to test an approach using vertically aligned carbon nanotube bundles as fluidic conduits for bile drainage.

Cette thèse propose un modèle dynamique d'un bioréacteur à membrane submergée (sMBR) comprenant les comportements physiques et biologiques du processus. La filtration (aspect physique) est un modèle de résistances en série composé de la résistance réversible (liée au processus de formation d'un gâteau qui peut être enlevé par lavage de l'air) et de la résistance à colmatage irréversible. La fonction biologique est mise en œuvre par l'extension du modèle de chemostat simple avec un mécanisme de filtration.L'analyse du modèle comprend : l'analyse asymptotique, l'observabilité, la contrôlabilité et l'étude dynamique lente et rapide. Cette dernière, basée sur le théorème de Tikhonov, révèle la possibilité de simplifier la dynamique du modèle en découplant le processus en trois échelles de temps : l'évolution du colmatage à long terme (dynamique lente), la dégradation biologique ( dynamique rapide) et la formation du gâteau (dynamique ultrarapide). Comme les processus avec sMBRs sont relativement nouveaux, les données réelles de processus sont difficiles à obtenir. Ainsi, une installation pilote d'un système de recirculation de l'aquaculture avec une sMBR est conçue, construite et automatisée. Des mesures en ligne du processus, tels que la température, les matières en suspension (MES), l'ammoniac et les concentrations des effluents nitrates, la croisée de l'air et des débits d'effluents et la pression transmembranaire, sont réunis afin de valider le modèle proposé.Pour mettre en évidence le cadre général du modèle proposé, le même modèle est composé d'ensembles de données réelles obtenues à partir d'une installation de traitement des eaux usées à sMBR. Par conséquent, une identification de paramètre est organisée en trois étapes correspondant aux trois échelles de temps obtenues à partir de l'analyse analytique. L'identification de paramètre est implémentée en utilisant une fonction de coût aux moindres carrés pondérés et l'inverse de la Fisher Matrix Information (FIM), qui est utilisé pour obtenir les intervalles de confiance des paramètres calculées par une borne inférieure sur la matrice de covariance des estimations des paramètres. La capacité du modèle à prédire la pression transmembranaire et la dégradation biologique est prouvée par la validation du modèle et la validation croisée des résultats.Concernant le contrôle du processus, deux approches différentes sont utilisées : un contrôleur partielle linéaire basé sur la théorie de Lyapunov est conçu afin de stabiliser la production encrassement en actionnant dans la croisée de l'air et les flux d'effluents; une commande prédictive de modèle non linéaire (NMPC) est mise en œuvre afin d'optimiser le taux de production d'effluent et de maximiser la période entre deux opérations de lessivage chimique.Les résultats présentés dans cette thèse montrent l'importance des études analytiques sur des modèles afin de traiter la cognition et la simplification de modèle. Un autre point important est la structure du modèle dynamique simple avec une petite quantité de paramètres. Ce travail montre que cette structure est suffisante pour mettre en œuvre des stratégies de contrôle avancé sur les processus sMBR et même de prédire la dégradation biologique et la dynamique de croissance du colmatage
This thesis proposes a simple submerge membrane bioreactor (sMBR) dynamic model that comprises physical and biological process behaviors. The filtration, physical aspect, is a resistance-in-series model that is composed with reversible resistance, linked to sludge cake formation process that can be detached by air scouring, and the irreversible fouling resistance. The biological feature is implemented extending the simple chemostat model to the filtration mechanism. The model asymptotic analysis, observability, controllability and fast and slow dynamic study are carried out. The latter, based on the Tikhonov's theorem, reveals the possibility to simplify model dynamics by decoupling the process in three time scales, i.e. long-term fouling evolution (slow dynamic), biological degradation (fast dynamic) and fouling cake formation (ultrafast dynamic). As sMBR processes are relativity new, real process data are scarce. Thus, a recirculating aquaculture system pilot plant with an sMBR is design, build and automated. Process online measurements such as: temperature, total suspended solids (TSS), ammonia and nitrate effluent concentrations, air cross- and effluent flow rates and trans-membrane pressure are gathered in other to validate the proposed model. To evidence the model general framework the same model is confronted with real data sets obtained from an sMBR wastewater treatment plant. Therefore, a parameter identification is organized in three steps corresponding to the three time scales obtained from the analytical analysis. The parameter identification is implemented using a weighted least-squares cost function and the inverse of the Fisher Information Matrix (FIM), which is used to obtain the parameters confidence intervals, is computed by a lower bound on the covariance matrix of the parameter estimates. The model capacity to predict trans-membrane pressure and biological degradation is proved by model validation and cross-validation results, in which an accurate correlation coefficients (R^2) of approximately 0.83 are obtained. Concerning the process control, two different approach are used: a partial-linearizing feedback Lyapunov controller is designed in order to stabilize the fouling production by actuating in the air cross- and effluent flows; and a nonlinear model predictive control (NMPC) is implemented in other to optimize the effluent production rate and maximize the period between two chemical cleaning procedures. The results included in this thesis show the importance of analytical model studies in order to process cognition and model simplification. Another important point is the simple dynamic model structure, with a small quantity of the parameters, which is adequate to implement advanced control strategies on sMBR processes and, similarly, to predict biological degradation and fouling build-up dynamics

The thesis describes an experimental investigation of the flow in a shaken bioreactor of cylindrical geometry with a flat bottom. Several reactor designs can be distinguished that attain mixing in different ways: oscillatory flow mixers (OFM), static mixers, stirred vessels and shaken bioreactors. Shaken bioreactors are often small-scale mixers (microwells) employed in the early stage of bioprocess development (i.e. microbial fermentation, bioconversion and product recovery techniques), before the developed process is implemented in a large-scale industrial stirred tank. However, despite their wide use, little is known about the fluid mechanics of these systems. In the present study Particle Image Velocimetry (PIV) measurements are carried out to determine the variation of the flow dynamics in a cylindrical shaken geometry for different operating conditions such as medium height, shaking frequency, orbital shaking diameter, cylinder inner diameter and fluid viscosity. In the first part phase-resolved measurements are carried out with PIV to provide a thorough characterisation of the flow and mixing dynamics occurring in a cylindrical shaken bioreactor for a fluid of low viscosity (i.e. water). From this analysis a flow scaling law based on the Froude number, Fr, is identified, which correlates the shape and inclination of the free surface to the occurrence of a flow transition. More specifically it was found that at low Fr the mean flow ischaracterised by a toroidal vortex with its axis aligned along the azimuthal direction, while after flow transition the free surface exhibits a phase lag and a vortical structure with a vertical axis that precesses around the cylinder axis is present. In the second part of the thesis flow characteristics, such as the interfacial area, circulation time, vortex size and location, kinetic energy and viscous dissipation rate of kinetic energy for a fluid of low viscosity are analysed in depth. The free surface interfacial area was directly measured by image analysis to assess oxygen transfer potential and was compared to an analytical solution valid for low Fr. The non-dimensional time and length scales of the vortical structures occurring in the cylindrical bioreactor were determined to provide an insight into the mixing dynamics, while a Reynolds decomposition analysis of the kinetic energy was carried out to assess the onset of a laminar-turbulent flow transition with increasing Fr. Direct measurements of the viscous dissipation rate of the kinetic energy, ǫ, were obtained across the tank to help assess micro-mixing and identify regions in the bioreactor experiencing higher levels of viscous stresses that can potentially affect cell growth. In the third part of the thesis the flow obtained with Newtonian fluids of higher viscosity is investigated and the flow scaling law determined for water is extended to a broader range of viscosity. A flow transition map based on Fr and Re is identified and four main regions characterised by different mean flow dynamics are shown. The turbulent kinetic energy levels and shear rate magnitudes are assessed for different combinations of Fr and Re. The results offer valuable new information for the design of mixing processes and crucial data to validate computational fluid dynamics simulations of cylindrical shaken bioreactors.

The role of energy as a stimulant for economic growth and environmental sustainabilityof any nation has made the focus on green fuels, including fermentative hydrogen (bioH2) andmethane (bioCH4), to be a priority for the World’s policy makers. Nigeria, as the most populousAfrican country, with worsening energy crisis, can benefit from the introduction of the bioH2 andbioCH4 technologies into the country’s energy mix, since such technologies have the potential ofgenerating energy from organic wastes such as fruit waste.Fruit waste was studied in detail in this work because of its great economic andenvironmental potential, as large quantities of the wastes (10–65% of raw fruit) are generatedfrom fruit consumption and processing. Meanwhile, bioH2 and bioCH4 productions involvinganaerobic microorganisms in direct contact with organic wastes have been observed to result insubstrate and product inhibitions, which reduce the gas yields and limit the application of thetechnologies on an industrial scale. For example, in this study, the first experimental work todetermine the effects of hydraulic retention times and fruit mixing on bioH2 production fromsingle and mixed fruits revealed the highest cumulative bioH2 yield to be equivalent to 30% ofthe theoretical yield. However, combining the fermentation process with the application ofmembrane encapsulated cells and membrane separation techniques, respectively, could reducesubstrate and product inhibitions of the microorganisms. This study, therefore, focused on theapplication of membrane techniques to enhance the yields of bioH2 and bioCH4 productions fromthe organic wastes.The second experimental work which focused on reduction of substrate inhibition,involved the investigation of the effects of the PVDF membrane encapsulation techniques on thebioH2 and bioCH4 productions from nutrient media with limonene, myrcene, octanol and hexanalas fruit flavours. The results showed that membrane encapsulated cells produced bioCH4 fasterand lasted longer, compared to free cells in limonene. Also, about 60% membrane protectiveeffect against myrcene, octanol and hexanal inhibitions was obtained. Regarding bioH2production, membrane encapsulated cells, compared to free cells, produced higher average dailyyields of 94, 30 and 77% with hexanal, myrcene and octanol as flavours, respectively. The finalpart of the study, which was aimed at reducing product inhibition, involved the study of theeffects of membrane permeation of volatile fatty acids (VFAs) on the bioreactor hydrodynamicsin relation to bioH2 production. The investigation revealed that low transmembrane pressure of104Pa was required to achieve a 3L h-1m-2 critical flux with reversible fouling mainly due to cakelayer formation, and bioH2 production was also observed to restart after VFAs removal.The results from this study suggest that membrane-based techniques could improve bioH2and bioCH4 productions from fermentation media with substrate and product inhibitions.

The increasing worldwide contamination of aquatic environment with pollutants introduced by anthropogenic sources has become of great concern. Although present at low concentration, many of these pollutants have considerable long-term impacts on the ecosystem, such that extremely challenging legislative limits on their concentration in effluents are being proposed. This has led to the examination of membrane bioreactor (MBR) technology for wastewater treatment, since it offers the best and most consistent treated water quality of all biotreatment processes. However, both a review of the literature and experimental study reveals that MBRs appear to offer insufficient benefit over conventional processes to make their implementation for this duty viable, given their significantly higher cost. Notwithstanding this, the fate of micropollutants in MBR processes represents the most rapidly growing research topic in the general MBR subject area. Despite the wide range of products commercially available, the majority are hollow fibre (HF) products based on polyvinylidene difluoride (PVDF) or polyethersulfone (PES) and almost all are in the pore size range between 0.04 and 0.4 μm. Whilst differences in module design across the whole range of products constrains their interchangeability, the increased acceptance of and confidence in this technology is reflected in the increased rate of implementation of large installations and the overall exponential growth in the market of 11-13% per year. However, there appears to be a dysfunction between the needs of the industry and the primary research area within the academic community, with practitioners identifying clogging as the main impediment to sustainable operation while 31% of all research papers published to end 2009 were based on fouling and less than 1% on clogging. Experimental study of operation of an MBR to treat municipal wastewater based on a new HF material has revealed that studies based on aeration step provide a more realistic indication of critical operation than classical flux step experiments, since the latter involve imposing a hydraulic shock on the membrane. Simple measured sludge fouling propensity parameters did not appear to relate to fouling rate, with a counter-intuitive relationship arising under some operating conditions.

The project aimed to extend the limited knowledge ofMBR (Membrane Bioreactor) operation for the treatment of stabilised (old) landfillleachate using an air-lift tubular membrane configuration and comparing the results with those obtained for sewage treatment under largely identical conditions. SRT (solids retention time) was used as the principal fixed variable in the two trials so as to allow comparison of process performance for the two different feedwaters. Supplementary tests were also conducted on: 1. bench-scale porous pots, used to identify the optimum HRT (hydraulic retention time) value for leachate treatment, and 2. intermittent aeration, used to minimise aeration demand. At bench scale removals of69 ± 1% and 99.9 ± 0.1% chemical oxygen demand (COD) and ammonia (NH/) respectively were achieved at an HR T of 5 d and temperatures ~ 21°C. For this trial the mixed liquor volatile suspended solids/mixed liquor suspended solids (MLVSSnvn.SS) ratio was 0.7 ± 0.03 and the volumetric loading rate (VLR) 0.4±0.02 kgCOD m- 3 dol and 0.15 ± 0.003 kgNlI/ m-3 dol; the COD and NH/ food to microorganism ratio (FIM) ratio values were respectively 0.1 ± 0.01 and 0.04 ± 0.004 dol; specific oxygen utilisation rate (SOUR) was 16 ± 7 mg02.gVSS- 1 .h- 1 and nitrifiers:heterotrophs ratio was around 80:20. This compared with similar nitrifiers proportions (i.e. 70 to 80%) reported in the literature. During pilot trials COD removals at the stabilised period were consistently larger for sewage (69 - 83%) than leachates at the pseudo stability phase (28 - 56%), the latter being somewhat lower than values reported in the literature for full-scale plants. However, for both feedwaters maximum was obtained at VLRs between 0.99 and 1.2 kgCOD.m- 3 .d- 1 • NRt + removals were readily achieved with values ~ 88.6%. Biomass characteristics, namely particle size distribution (PSD), extracellular polymeric substances (EPS) concentrations and dynamic viscosity (11) were found to be similar for both sewage and leachate sludges, while soluble microbial products (SMP), MLVSS!.MLSS, F/M, SOUR, and heterotrophslnitrifiers proportions differed. most likely i due to impact of the feedwater character. Microbial dynamics and speciation were highly dependent on feed water quality showing that highly variable feeds such as leachate and sewage would develop inconsistent bacterial communities but analogous to each other. Constant feeds, on the other hand, would develop highly consistent bacterial community profiles. Nevertheless species richness or abundance of neither group (i.e. inconsistent and consistent communities) was significantly correlated to microbial foulants production such as SMP andlor EPS. Even further it was found that either microbial community would have no effect on COD or TOC (total organic carbon) levels of the treated feeds. Critical flux (Je) tests revealed fouling of leachate biomass to be more severe than that imposed by sewage biomass. and that fouling by the leachate biomass is predominantly attributable to the feedwater itself. No correlation between fouling and conventional biomass foulants (i.e. SMP and EPS proteins and carbohydrates) was evident, whilst a stronger correlation of fouling was shown with TOC of the SMP fraction. The ceramic membrane material tested was, as expected, more resistant to fouling than the polymeric membranes used. The highest le values on continuous air-sparging for sewage and leachate were 36 and 24 L.m"2.h"1 respectively. for polymeric membranes, and about 30 L.m"z.h"l during intermittent air-lift conditions for sewage, while absent for leachate. For ceramic membranes no le values were observed at continuous air-sparging. whilst no fouling was evident for either polymeric or ceramic materials challenged with leachate operating with intermittent aeration (0.5 -1 Hz) up to a flux (1) ofl3 and 44 L.m"l.h"l. Cylindrical geometry lumens were found to be more effective during air-lift operations than square lumens.

The project aimed to extend the limited knowledge ofMBR (Membrane Bioreactor) operation for the treatment of stabilised (old) landfillleachate using an air-lift tubular membrane configuration and comparing the results with those obtained for sewage treatment under largely identical conditions. SRT (solids retention time) was used as the principal fixed variable in the two trials so as to allow comparison of process performance for the two different feedwaters. Supplementary tests were also conducted on: 1. bench-scale porous pots, used to identify the optimum HRT (hydraulic retention time) value for leachate treatment, and 2. intermittent aeration, used to minimise aeration demand. At bench scale removals of69 ± 1% and 99.9 ± 0.1% chemical oxygen demand (COD) and ammonia (NH/) respectively were achieved at an HR T of 5 d and temperatures ~ 21°C. For this trial the mixed liquor volatile suspended solids/mixed liquor suspended solids (MLVSSnvn.SS) ratio was 0.7 ± 0.03 and the volumetric loading rate (VLR) 0.4±0.02 kgCOD m- 3 dol and 0.15 ± 0.003 kgNlI/ m-3 dol; the COD and NH/ food to microorganism ratio (FIM) ratio values were respectively 0.1 ± 0.01 and 0.04 ± 0.004 dol; specific oxygen utilisation rate (SOUR) was 16 ± 7 mg02.gVSS- 1 .h- 1 and nitrifiers:heterotrophs ratio was around 80:20. This compared with similar nitrifiers proportions (i.e. 70 to 80%) reported in the literature. During pilot trials COD removals at the stabilised period were consistently larger for sewage (69 - 83%) than leachates at the pseudo stability phase (28 - 56%), the latter being somewhat lower than values reported in the literature for full-scale plants. However, for both feedwaters maximum was obtained at VLRs between 0.99 and 1.2 kgCOD.m- 3 .d- 1 • NRt + removals were readily achieved with values ~ 88.6%. Biomass characteristics, namely particle size distribution (PSD), extracellular polymeric substances (EPS) concentrations and dynamic viscosity (11) were found to be similar for both sewage and leachate sludges, while soluble microbial products (SMP), MLVSS!.MLSS, F/M, SOUR, and heterotrophslnitrifiers proportions differed. most likely i due to impact of the feedwater character. Microbial dynamics and speciation were highly dependent on feed water quality showing that highly variable feeds such as leachate and sewage would develop inconsistent bacterial communities but analogous to each other. Constant feeds, on the other hand, would develop highly consistent bacterial community profiles. Nevertheless species richness or abundance of neither group (i.e. inconsistent and consistent communities) was significantly correlated to microbial foulants production such as SMP andlor EPS. Even further it was found that either microbial community would have no effect on COD or TOC (total organic carbon) levels of the treated feeds. Critical flux (Je) tests revealed fouling of leachate biomass to be more severe than that imposed by sewage biomass. and that fouling by the leachate biomass is predominantly attributable to the feedwater itself. No correlation between fouling and conventional biomass foulants (i.e. SMP and EPS proteins and carbohydrates) was evident, whilst a stronger correlation of fouling was shown with TOC of the SMP fraction. The ceramic membrane material tested was, as expected, more resistant to fouling than the polymeric membranes used. The highest le values on continuous air-sparging for sewage and leachate were 36 and 24 L.m"2.h"1 respectively. for polymeric membranes, and about 30 L.m"z.h"l during intermittent air-lift conditions for sewage, while absent for leachate. For ceramic membranes no le values were observed at continuous air-sparging. whilst no fouling was evident for either polymeric or ceramic materials challenged with leachate operating with intermittent aeration (0.5 -1 Hz) up to a flux (1) ofl3 and 44 L.m"l.h"l. Cylindrical geometry lumens were found to be more effective during air-lift operations than square lumens.

Bubble columns are widely used in the bio-processing industry to perform large scale, aerobic fermentations. For this reason, there is a clear interest in optimising both the design and operation of such reactors. One cost-effective approach is the development of a Computational Fluid Dynamics (CFD) model of the process; the major advantage of this methodology being that it provides detailed information about the flow patterns within the column, knowledge which is difficult to experimentally obtain at an industrial scale. Such data are of particular value as it has been conjectured that poor distribution of nutrients leads to a reduction in the process yield. Hence, the aim of this work was the development of a CFD model capable of accurately describing flow in bubble columns operated in the industrially relevant heterogeneous flow regime (i.e. at superficial velocities greater than 0.1 m/s). In order to develop and validate such a model, it was necessary to obtain experimental data for both an air/water system as well as an air/fermentation media system, the latter being a topic rarely examined in the literature. Hence, a comprehensive experimental program was undertaken at both the bench-top (using a column 0.19 m in diameter and 1 m in height) and pilot-scales (using a column 0.39 m in diameter and 2 m in height). A comprehensive experimental dataset consisting of measurements of the mixing time, overall hold-up, bubble size distribution, as well as profiles of the local hold-up, liquid velocity and gas velocity was generated. Both experimental configurations were modelled using CFD; with the model predictions being in satisfactory agreement with the experimental data at both scales. The development of a predictive model capable of accurately describing the complex mixing patterns in bubble columns (both with and without the presence of surfactants) operating in the heterogeneous flow regime is seen as a key step in the design and optimisation of such systems.

Monitoring and controlling pH is of utmost importance in bioprocessing as it directly affects product yield and quality. Multiplexed experiments can be performed in nanobioreactors for optimisation of yield and cell heterogeneity in a relatively quick and inexpensive manner. In this thesis, a pH holographic sensor (holosensor) is miniaturised to 3.11 nL in volume and integrated into a PDMS-glass microfluidic chip for monitoring the growth of Lactobacillus casei Shirota. Although other established methods for monitoring cell cultures can be utilised, miniaturised holosensors enable real-time and non-consumptive monitoring of the bacterial cell culture growth medium. The 2-hydroxyethylmethacrylate (HEMA)-co-2-(trifluoromethyl) propenoic acid (TFMPA) holosensor was fabricated using an adapted technique from photolithography, coupled with the use of a polymerisation inhibitor to control the gel polymerisation with diameters not exceeding a standard deviation of 0.067. The hologram brightness was optimised to 1.05 ms integration time with 36X magnification using a low power (0.290 mW) 532 nm green continuous wave (CW) laser with a devised beam-offset technique. The holosensor was characterised with ionic strength balanced (9.50 mS/cm) McIIvaine pH buffers and a calibration curve plotted together with measured ionic strength, optical density at 600 nm (OD600) and pH. Correspondingly, RGB-xyY transformed values were plotted in the CIE 1931 chromaticity diagram. Later, a miniaturised 0.4φ HEMA-co-TFMPA holosensor and array was also demonstrated. Together with the 3.0φ holosensor, an accuracy parameter for the 0.4φ spot and array holosensors were calculated to be 99.08%, 99.38% and 97.77% respectively. Further work involved studying the issues associated with fabricating gels with unusually flat gel profiles. Other preliminary results suggested the alternative of utilising polymers as a holosensor substrate, together with a dye-free method for hologram fabrication, outlined the prospective possibility of a miniaturised holosensor integrated into a polymer microfluidic chip with the flexibility of hologram colour customisation for cell culture monitoring.

Mixing plays a substantial role in determining the overall performance of a bioreactor. Well mixing in bioreactor, especially for ethanolic fermentation process is important for the homogenization of miscible and immiscible liquids, gas dispersion and suspension of solid particles. Improper mixing will eventually affect the biological and kinetics reactions occurring in the bioreactor and subsequently deteriorate the bioreactor performance. Currently, most modeling and control applications of bioreactors have been devoted to ideally mixed assumption, for simplicity. This is not realistic in practical applications. Furthermore, the strength and accuracy of the bioreactor models reflect their performance and subsequently its control strategy. Therefore, it is vital to consider the imperfect mixing for the control of bioreactor.In this study, a batch, micro-aerobic bioreactor for ethanolic fermentation process will be considered for modeling. Up to date, not much study has been conducted in exploiting the mixing mechanism for controlling this type of bioreactor. Traditionally, only the bioreactor conditions such as temperature and pH are controlled for such a batch bioreactor. Other parameters, such as aeration rate and stirrer speed are not used to control the bioreactor. Thus, it is difficult to improve the bioreactor performance as the bioreactor performance is less sensitive to both temperature and pH than to the mixing mechanism. However, the mixing behaviour of the bioreactor needs to be captured if we are to employ both aeration rate and stirrer speed for the control of such a batch bioreactor.It is known that aeration rate and stirrer speed could significantly affect the biological and kinetics reactions. Therefore, both aeration rate and stirrer speed are suggested in this work as manipulated variables in the modeling of batch bioreactor. Thus, with this approach the ideally mixed assumption will be relaxed.The models proposed will be implemented for control studies. New control strategies will be established for continuous bioreactor, whereby dilution rate and substrate concentration are considered as disturbance variables and both aeration rate and stirrer speed are suggested as manipulated variables. With this approach, the practicability of the proposed models could be investigated.The aims of this research have therefore been as follows: 1. To experimentally study the impact of aeration rate and stirrer speed on the bioreactor performances, i.e. yield and productivity. 2. To develop an integrated bioreactor model to allow us to employ the aeration rate and stirrer speed as manipulated variables for control design. 3. To establish new control strategies for bioreactor without the ideally mixed assumption.A systematic approach has been proposed to develop the non-ideally mixed bioreactor model and to design the control strategy of the lab-scale fermentation process. Three modeling approaches are employed, i.e. data-based, kinetics hybrid and kinetics multi-scale models for the analysis of the impacts of both aeration rate and stirrer speed on the performance of bioreactor. Using the three models, the aeration rate and stirrer speed are also used to analyze the mixing mechanism in the bioreactor.Furthermore, new control strategies are then proposed for the bioreactor. By using the proposed control strategies, the effect of both aeration rate and stirrer speed on the overall performance could be analyzed in the face of disturbances on other process parameters. Furthermore, the stability and achievable performance of the control strategies could be compared for different models. Hence, the proposed control strategies would lead to a better operation of the bioreactor.The study highlighted the following main findings: 1. It is identified that both aeration rate and stirrer speed could affect significantly the overall performance of the bioreactor. Therefore, both aeration rate and stirrer speed rather than temperature and pH could be used as manipulated variables for controlling the bioreactor. The ideally mixed assumption is relaxed where the mixing mechanism of the bioreactor is included in the proposed model.2. The main issue in modeling is the complexity of the microbial reactions and kinetics of the bioreactor performance for the non-ideally mixed behaviour of the bioreactor. Thus, it is important to identify the main reactions and kinetics which actually affect the bioreactor performance. In this study, Monod’s kinetics has been employed with the implementation of both aeration rate and stirrer speed. It is shown that the kinetics multi-scale model demonstrated good predictions of the mixing mechanism of bioreactor. Different conditions of aeration rate and stirrer speed influence the mixing mechanism and thus, contribute to the dynamics and kinetics within the bioreactor. These show that both aeration rate and stirrer speed play important role in studying the non-ideally mixed mechanism of the bioreactor.3. Optimization results, however, suggest that the kinetics hybrid model gives the most comparable values of maximum yield and productivity. Thus, this model is suggested for the determination of the optimum conditions of the bioreactor operation due to its simplicity in model construction, as compared to the kinetics multi-scale model.4. The control strategy of bioreactor using the data-based model does not always produce good performance, especially in the face of large disturbances. This implies that the use of models with ideally mixed assumptions would not always give good overall performance. Therefore, the controllability of the bioreactor performance is further improved with the implementation of the proposed non-ideally mixed bioreactor model. It is observed that both databased and kinetics hybrid models are able to keep the controlled variables in their set-point values by manipulating both aeration rate and stirrer speed for low disturbance changes.Hence, this research contributes on the understanding of mixing phenomena in micro-aerobic fermentation process from which a set of optimal operational conditions and control strategies to enhance its performance are developed.

Modern landfilling constitutes an unavoidable final step in solid waste management. It aims to close the “Material Cycle” bringing elements back to the non-mobile state they were in before their extraction. At the same time, the application of Sustainability Principle to landfills prescribes to guarantee environmental protection and health safety, ensuring that the disposed waste will be chemically and biochemically stable within a reasonable amount of time. A “Sustainable Landfill” must combine these two fundamental purposes, balancing the efforts to obtain a “sustainable closure of material loop”. The enhancement of biochemical processes in a landfill, with the purpose of reaching faster environmentally safe conditions and terminate the post closure care, is one of the main debated topics in waste management scientific literature. The general aim of the PhD project was giving a contribution to this debate through the lab-scale testing of systems able to simulate landfills behaviour and the analysis of the long-term expectable chemical status of waste undergone to sustainable landfilling. The first part of the work is an overview on the basic biochemical processes in landfills and on the laboratory-scale landfill simulation tests. The approach used by the PhD student is mainly experimental, starting from the design and the management of several laboratory-scale landfill simulation tests. The elaboration of the obtained data was useful for evaluating the performances of the tested bioreactor concepts as well as for comparing the results to other scientific data derived from a thorough bibliographic research. The original work produced by the student can be subdivided in three different arguments. The Semi-aerobic, Anaerobic, Aerated (S.An.A. ®) hybrid bioreactor is an innovative landfill concept, lab-scale run with promising results concerning the enhancement of methane production and the reduction of the long-term emissions. The effects of the recirculation of reverse osmosis leachate concentrate inside the landfill have been analysed to check if the potential accumulation of contaminants in waste body can turn this practice unsustainable. The Final Storage Quality (FSQ) procedure, for endorsing the landfill Post Closure Care termination, was tested on an over-stabilized waste of which total emissions and chemical speciation of main elements were calculated.
Il moderno sistema di deposito finale dei rifiuti in discarica costituisce un passaggio inevitabile nella gestione dei rifiuti solidi. Il suo scopo è chiudere il “ciclo della materia” riportando gli elementi allo stato di immobilità in cui erano prima di essere estratti. Contemporaneamente, l’applicazione del principio di sostenibilità alle discariche prescrive di garantire la salvaguardia ambientale e della salute, assicurando che il rifiuto smaltito diventi chimicamente e bio-chimicamente stabile entro un tempo “ragionevole”. Una “Discarica Sostenibile” deve combinare questi due principi, bilanciando i contributi per ottenere una “chiusura sostenibile del ciclo della materia”. Il potenziamento dei processi biochimici in discarica, con lo scopo di raggiungere più velocemente condizioni che garantiscano la salvaguardia ambientale e terminare la fase di post-chiusura, è uno degli argomenti più dibattuti nella letteratura scientifica inerente alla gestione dei rifiuti. Lo scopo generale del progetto di dottorato è stato contribuire a questo dibattito, mediante lo svolgimento di test in scala di laboratorio utili a simulare l’andamento dei processi in discarica e analizzando lo stato biochimico finale dei rifiuti trattati. La prima parte del lavoro consiste in una panoramica sui processi biochimici in discarica e sulla metodica dei test biochimici in scala di laboratorio. L’approccio usato dallo studente in questa tesi è principalmente sperimentale, basato sulla progettazione, l’esecuzione e la rielaborazione dei dati di svariate simulazioni di discarica in laboratorio. La discussione dei risultati ottenuti è stata propedeutica alla valutazione delle performance dei modelli concettuali testati così come al confronto con altri risultati ottenuti grazie a una approfondita ricerca bibliografica. Il lavoro originale svolto dallo studente può essere diviso in tre progetti principali. Il reattore ibrido Semi-aerobico, Anaerobico, Aerato (S.An.A ®) è una concetto innovativo testato in scala di laboratorio con promettenti risultati per quanto concerne la stimolazione della produzione di metano e la riduzione delle emissioni di lungo termine. Gli effetti del ricircolo del concentrato di percolato da osmosi inversa all’interno del corpo rifiuti di una discarica sono stati analizzati per verificare se possano esistere potenziali accumuli di contaminanti che rendano insostenibile tale pratica. La procedura di Final Storage Quality (FSQ) per determinare la chiusura della fase di aftercare di una discarica è stata testata su un rifiuto sovra-stabilizzato di sui sono state calcolate emissioni totali e la speciazione chimica degli elementi principali.

Membrane bioreactors (MBR) are a combination of common bioreactors and membrane filtration units for biomass retention, presenting unique advantages like high effluent quality and a smaller footprint than the one by conventional wastewater treatment plants. However, fouling and its associated costs are the main drawbacks related to this technology. This thesis presents a step towards the integrated operation of MBRs through experimental and model-based studies. Interactions between the biological (nutrient removal and sludge characteristics) and physical (hydrodynamics and filtration) processes in MBRs were studied, with the final aim being to improve their integrated operation and control. Moreover, the reduced energy costs and the better understanding of MBR operation may contribute to making MBR systems a more competitive technology to deal with water scarcity problems
Els bioreactors de membranes (BRM) són una combinació dels reactors convencionals i una unitat de filtració que reté la biomassa, de manera que presenten com a gran avantatge una qualitat de sortida amb estàndards de reutilizació, i molt poca necessitat d’espai. Tanmateix, l'embrutiment i els seus costs associats són els principals inconvenients d'aquesta tecnologia. Aquesta tesi presenta un pas endavant cap a l’operació integrada dels BRM mitjançant estudis experimentals i de modelització. Les interaccions entre els processos biològics (eliminació de nutrients i característiques de la biomassa) i físics (hidrodinàmica i filtració) que tenen lloc als BRM s’han estudiat amb l’objectiu final de millorar-ne la seva operació i el control integrat. A més, s'han reduit els costos energètics, els quals contribueixen a la millora de la competitvitat de la tecnologia BRM com a solució potencial per a problemes d’escassetat d’aigua

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

This thesis is concerned with the biodegradation of oily sludges typically found at refinery sites as waste residues from the refining of mineral oil. Currently these type of wastes represent significant environmental risk. Current technology that addresses containment during treatment to regulate the release of volatile organic carbons and reduction of the polynuclear aromatic hydrocarbons in the sludge, is incineration. Incineration is a costly option and this research has shown that the same treatment standards as incineration is achievable through bioreactor treatment with the correct process and reactor design.

Membrane bioreactors (MBRs) are commonly used in wastewater treatment processes. In fact, the demand is expected to increase with more than double digit growth annually over the next decade [5]. However, operational costs of MBRs are still higher compared to operational costs of conventional treatment plants due to the additional aeration and pumping required in MBRs. This study examines the feasibility of using excess air that was used to clean the membrane for water conveyance (known as airlift pump), for a minimized energy use in MBR processes. In order to meet the objective, prototypes of airlift pumps were built with different dimensions. The experimental results of each prototype were comprehensively compared to existing models in the literature. The models were modified for a better fit of the experimental data. It was determined whether a new apparatus, where many riser tubes were bundled together, would behave like many individual riser tubes. While the air was injected at the bottom of the individual riser tube previously, the bundled riser tubes of the new apparatus would be attached to a rubber sheet; this, was attached to a frame. The rubber sheet was added to the apparatus in order to trap the air in the tank and lead it to the bundle of riser tubes. Different collector angles of the rubber as well as different water heights were investigated. The experimental results were compared to the previously modified models. The last step was to design a system that redirects the pumped water so that it can be transported back to the head of the MBR plant. The results suggest that air exiting to the atmosphere from an MBR can be used to transport the water. However, the models are only able to predict water flows for individual airlift pumps that consist of a single riser tube, where the air is injected at its bottom. Further research needs to be done in order to be able to predict water flows that can be achieved in systems, such as the one proposed in this present study, which uses a bundle of riser tubes.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate