Em biorreatores de agitação mecânica (STR), a circulação e a mistura do fluido são influenciadas pela configuração do equipamento e pela disposição dos impelidores e aspersores de gás. Já em biorreatores airlift, sua geometria e, principalmente, o tipo e forma de aspersão de oxigênio, têm primordial efeito tanto na transferência de oxigênio quanto no crescimento microbiano e na formação de produtos. Para o cultivo de Aspergillus oryzae IPT-301, o suprimento de oxigênio é um parâmetro fundamental, em razão do metabolismo unicamente aeróbio deste microrganismo. Neste contexto, analisou-se o transporte de massa gasosa em ambos os equipamentos, contendo fluidos com viscosidades distintas: água destilada e diferentes concentrações de soluções de pectina. Com estudos de mecânica dos fluidos, correlações matemáticas empíricas para determinação do coeficiente volumétrico de transferência de oxigênio (KLa) foram utilizadas para relacionar os resultados experimentais com os calculados. A produção de pectinases também foi avaliada nesses equipamentos. O meio de cultivo continha sais nutrientes, extrato de levedura, glicose e pectina cítrica. Avaliaram-se diferentes configurações de impelidores Rushton e pitched blade, além de várias geometrias de aspersores de gás, tais como ferradura de aço inoxidável, pedra sinterizada, aeradores de aquário e de latão e funis de vidro sinterizado. Em STR, a análise fatorial mostrou que os maiores incrementos de KLa foram com a combinação de impelidores Rushton, em água, com aspersor do tipo aquário a 700rpm e 1,71L/L/min; em airlift, com o aspersor aquário, alocado na região externa do tubo interno, e com o aspersor pedra sinterizada. O modelo proposto por Miller (1974) foi o mais adequado para determinar a potência requerida pelos fluidos deste trabalho, em STR e sob aeração. O modelo de Wang et al. (1979), com adaptações, ajustou-se aos dados com água; e para as soluções de pectina, a correlação descrita por Badino Jr. et al. (2001) foi melhor ajustada. Três ensaios para produção enzimática foram processados em STR: ambos com três impelidores Rushton, aspersores dos tipos ferradura (A), aquário (B) e aquário com meio com pectina desesterificada (C). Em airlift, foram testadas as condições produtivas com os aspersores do tipo aquário (externo) (A), pedra sinterizada (B) e aquário (externo), com pectina desesterificada (C). Em STR, o melhor resultado de KLa, em meio isento de células, foi na condição C (29,88h-1), bem como vantagens econômicas como o menor tempo de permanência da máxima frequência dos agitadores (tf,máx) (A: 23h; B: 8,5h; C:5h). Porém, resultado superior de máxima produção de pectinases foi na condição B (A: 24,60U/mL; B: 25,53U/mL; C: 13,36U/mL) em tf,máx inferior à condição A. Em airlift, o transporte de oxigênio, em meio isento de células, foi mais favorecido em A (21,96h-1), bem como o menor tempo máximo para manter a máxima vazão específica do gás (A: 29h; B: 72h; C: 57h). Além disso, a máxima atividade enzimática foi superior na mesma condição (A: 24,61U/mL; B: 21,94U/mL; C: 2,29U/mL). Assim, conclui-se que, desde que planejadas as condições operacionais e de processo de produção de pectinases de A. oryzae, ambos os biorreatores podem ser aplicados na produção de pectinases fúngicas. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior,CAPES / In stirred tank reactors (STR), circulation and mixing of fluid are influenced by the reactor configuration and by how the impellers and the gas spargers are arranged in them. On the other hand, in airlift bioreactors, their geometry and especially the type and form of oxygen sparging have an effect on both oxygen transfer and on microbial growth and product formation. Oxygen supply for the cultivation of Aspergillus oryzae IPT-301 is a key parameter due to the aerobic metabolism of this microorganism. In this context, oxygen transfer in both equipments was analyzed. They contained fluids with different viscosities: distilled water and different concentrations of pectin solutions. Through the use of fluid mechanics studies, empirical mathematical correlations were used in order to determine the volumetric oxygen transfer coefficient (KLa) to match experimental and calculated results. Pectinase production was also assessed in those devices. The culture medium contained salts, yeast extract, glucose and citrus pectin. Different Rushton and pitched blade impeller configurations were evaluated, as well as various gas sparger geometries, such as stainless steel horseshoe, sintered stone, aquarium and brass spargers, and also sintered glass funnels. In STR, factorial design showed that the largest KLa value was obtained with the combination of Rushton impellers, in water, with the aquarium sparger, at 700rpm and 1.71L/min; in airlift, with the same sparger, put in the outer space of the inner tube and with the sintered stone sparger. The empirical correlation proposed by Miller (1974) was the most suitable one to determine the power requirement by the fluids in this work, in STR and under aeration. The correlation proposed by Wang et al. (1979), with adaptations, was better adjusted to the data set with water; the correlation described by Badino Jr. et al. (2001) was better suited for pectin solutions. Three tests for enzyme production were processed in STR: with three Rushton impellers, in all of them, and horseshoe (A), aquarium (B) and aquarium with non-esterified pectin medium (C) spargers. In airlift, enzyme production was tested with aquarium (external) (A), sintered stone (B) and aquarium (external) with non-esterified pectin (C) spargers. In STR, the best result of KLa in cell-free medium was provided in condition C (29.88h-1), as well as economic advantages such as shorter length of maintenance of the maximum impeller speed (tf,máx) (A: 23h; B: 8.5h; C: 5h). Nonetheless, higher pectinase production was obtained in condition B (A: 24.60U/mL; B: 25.53U/mL, C: 13.36U/mL) in tf,máx shorter than in condition A. In airlift, higher oxygen transfer in cell-free medium was obtained in condition A (21.96h-1), as well as the lowest length of maintenance of the maximum specific gas flow rate (A: 29h; B: 72h; C: 57h). Furthermore, maximum enzyme activity was higher in the same condition (A: 24.61U/mL; B: 21.94U/mL, C: 2.29U/mL). Thus, we conclude that if the operational conditions for pectinase production by A. oryzae are well planned, both bioreactors can be applied for the production of fungal pectinases.

Ácido lactobiônico e sorbitol têm importantes aplicações na indústria cosmética e farmacêutica. Esses produtos podem ser obtidos de forma equimolar em reações catalisadas por glicosefrutose oxidorredutase (GFOR) e glicono-δ-lactonase (GL), enzimas presentes no periplasma de Zymomonas mobilis. As reações são geralmente conduzidas com células bacterianas imobilizadas, sendo que a técnica de preparo deste biocatalisador demanda tempo, além de ser onerosa. Alternativas para a simplificação do preparo do biocatalisador imobilizado em alginato de cálcio e sua aplicação em diferentes regimes de operação e reatores foram estudadas neste trabalho, com o objetivo de aumentar o potencial de transferência dessa tecnologia para o setor industrial. Modificações na técnica de imobilização de Z. mobilis foram avaliadas quanto às concentrações do polímero e da solução de CaCl2 e do tempo de gelificação, buscando melhorar as propriedades mecânicas do gel e possibilitar sua utilização em reações repetidas. No caso, não foram observadas alterações significativas na resistência do suporte e nos parâmetros de avaliação da reação em qualquer das condições avaliadas. Assim, a técnica foi mantida na forma previamente definida: alginato de sódio, 2% (m/v); CaCl2, 0,3 mol/L; tempo de gelificação, 10 a 240 minutos. A reutilização do biocatalisador imobilizado por sete bateladas repetidas, num total de 176 horas, possibilitou a obtenção de cerca de 500 mmol/L de produtos (ácido lactobiônico e sorbitol) por ciclo, com valores médios de rendimento e de produtividade específica de 80% e 1,12 mmol/g/h. A possibilidade de supressão da permeabilização celular com brometo de cetil trimetil amônio (condição CTAB) foi demonstrada, uma vez que se constatou que a reticulação de células de Z. mobilis com glutaraldeído (condição Glu), além de inibir o metabolismo fermentativo de carboidratos como glicose ou frutose, permitiu o acúmulo dos produtos de bioconversão, sem afetar a atividade catalítica das enzimas. A atividade enzimática para a condição Glu (35 U/g de células) foi semelhante à da condição de referência CTAB (31 U/g). Adicionalmente, com o sistema imobilizado, constatou-se que o tratamento das células com glutaraldeído, normalmente feito antes da imobilização (condição Glu Imb), também pode ser suprimido, uma vez que o tratamento único das esferas do suporte (condição Branco Imb) com o agente de reticulação é suficiente para inativar o metabolismo de Z. mobilis. Os rendimentos em ácido lactobiônico e sorbitol, independentemente da condição (Glu Imb ou Branco Imb), foram da ordem de 80%, com concentrações de produto de cerca de 500 mmol/L. A estabilidade das enzimas nas reações de bioconversão manteve-se próxima à inicial após 150 dias de armazenagem. Reações de bioconversão foram conduzidas em regime descontínuo, em reator de agitação mecânica, com 20 e 30 g/L do biocatalisador imobilizado, resultando em 530 mmol/L de produtos em 24 horas. O processo foi testado, ainda, em regime descontínuo alimentado a fim de possibilitar o uso de maior massa de lactose, que não poderia ser empregada em descontínuo devido à baixa solubilidade deste carboidrato em água. Com 20 g/L de biomassa imobilizada, concentrações de produtos de 745 mmol/L foram obtidas em 42 horas, enquanto com 30 g/L foram necessárias 32 horas para atingir-se 776 mmol/L. Os resultados para as reações conduzidas em biorreator tubular com agitação pneumática, com 20 g/L de células, em regimes descontínuo e descontínuo alimentado foram muito próximos aos encontrados no sistema com agitação mecânica, demonstrando a flexibilidade do processo sob esse aspecto. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Lactobionic acid and sorbitol have important applications in cosmetic and pharmaceutical industries. These products can be obtained in equimolar basis in reactions catalysed by glucose-fructose oxidoreductase (GFOR) and glucono-δ-lactonase (GL), enzymes that are present in the periplasm of Zymomonas mobilis. The reactions are usually conducted with immobilized bacterial cells, the preparation technique of this biocatalyst being time demanding and expensive. Some alternatives for the simplification of the preparation of calcium alginate-immobilized biocatalyst and its application in different operation modes and types of bioreactors were studied in this work, with the aim of increasing the potential of this technology to be transferred to the industrial sector. Modifications in the technique of Z. mobilis immobilization were evaluated regarding the concentrations of sodium alginate and CaCl2 solution and the time of gelification, as an attempt to improve the mechanical properties of the gel and to allow its use in repeated reactions. In this case, no significant changes in both the support resistance and the reaction evaluation parameters were observed for any condition assessed. As such, the technique remained as previously defined: sodium alginate, 2% (w/v); CaCl2, 0.3 mol/L; gelification time, from 10 to 240 minutes. The reuse of the immobilized biocatalyst for seven consecutive batches, totalling 176 hours of reaction, allowed the attainment of products (lactobionic acid and sorbitol) concentrations of about 500 mmol/L, with approximately 80% of yield and 1.12 mmol/g/h of specific productivity. The possibility of suppression of the cell permeabilization with cetyl trimethyl ammonium bromide (CTAB condition) was demonstrated, since the crosslink of Z. mobilis with glutaraldehyde (Glu condition), besides inhibiting the fermentative metabolism of carbohydrates such as glucose or fructose, allowed the bioconversion products accumulation, without affecting the catalytic activity of the enzymes. The activity of GFOR/GL for the Glu condition (35 U/g of cell) was similar to the reference condition CTAB (31 U/g). Additionally, for the immobilized process, it was found that the cell treatment with glutaraldehyde, that is usually done before immobilization (Glu Imb condition), can also be suppressed because the sole treatment of the support beads with the crosslink agent (White Imb Condition) is enough to inactivate Z. mobilis metabolism. The yields in lactobionic acid and sorbitol, independently of the condition (Glu Imb or White Imb), were about 80%, with products concentrations nearly to 500 mmol/L. The enzymes stability remained stable after 150 days of storage. Bioconversion reactions were carried out in batch mode in a mechanically stirred reactor, with 20 and 30 g/L of the immobilized biocatalyst, resulting in 530 mmol/L of products after 24 h. The process was also tested in fed-batch mode with the purpose of allowing the use of a larger mass of lactose, which could not be employed in batch because of the relatively low solubility of this carbohydrate in water. With 20 g/L of immobilized biomass, product concentrations of 745 mmol/L were obtained in 42 h, whereas with 30 g/L 32 h were needed to reach 776 mmol/L. The results for the reactions conducted in pneumatic-agitated tubular bioreactor with 20 g/L of cells, in batch and fed-batch modes, were very close to those found in the system with mechanical agitation, evidencing the flexibility of the process under this aspect

This study was performed to increase knowledge of oxygen mass transfer (kLa) and mixing times in the scale-up of disposable bioreactors.Results of oxygen mass transfer studies showed kLa to increase with increasing agitation and aeration rates. By maintaining a scale-up constant such as gassed power to volume or shear, an almost constant kLa was achieved during scale-up from 50 to 2000 L. Using the scale-up constant Pg/V resulted in statistically higher kLa values at greater reactor volumes. Mixing times were revealed to be significantly affected by agitation, but not by the aeration rates tested. No pattern was recognized in the mixing time data over an increase in volume. Commonly used methods for predicting kLa upon scale-up were compared to experimental data. New coefficients were determined to fit the historic models to the parameters of this study, namely the unique geometry and low agitation and aeration rates used in the single-use systems. Each of the resulting four models was found to have average error rates from 16-23%. Although the error rates are not statistically different, the Moresi and Patete model was determined to be most conceptually accurate. The Moresi and Patete model found kLa to be more dependent on aeration than on the power input. This finding was consistent with the results of the experimental studies. The results of this study were for aeration rates (0.02-0.04 vvm) and agitation rates (Pg/V range of 2-20 W/m3) that are commonly used in single-use bioreactor systems.

The nitrogen reduction goals for the Chesapeake Bay are proving particularly difficult achieve. One of the contributing sources of N loading to the Bay is legacy N from groundwater springs. Denitrifying spring bioreactors are a best management practice that offers an opportunity to abate N from groundwater springs. The objective of this research is to estimate the regional abatement costs to remove legacy N using bioreactors. We identified 196 candidate springs for bioreactor installation that had a median spring flow of greater or equal to 100 m3 d-1 and greater or equal to 3 mg L-1. Under assumptions that 25% of the spring flow can be diverted to the bioreactor and a bioreactor N removal efficiency of 20%, we estimate that it would cost $3,325,400 yr-1 to abate 106,911 kg N yr-1. The driving factor of driving the unit costs of N removal is the amount of spring flow treated by the bioreactor. Further research is needed to understand how to optimize bioreactor performance and the benefits of increasing the percentage of spring flow treated given the impact these two factors on the cost-effectiveness of spring bioreactors in removing N. / Master of Science / There is a Chesapeake Bay Watershed total maximum daily load (TMDL) to reduce pollutants from going into the Bay. The reduction measures to achieve the TMDL goals must be in place by 2025. The nitrogen reduction goal for the Bay is proving particularly difficult to achieve. One of the contributing sources of N loading to the Bay is legacy N from groundwater springs. Denitrifying spring bioreactors are a best management practice that offers an opportunity to abate N from groundwater springs. One form of a denitrifying bioreactor is a hole in the ground filled with carbon substrate (i.e. woodchips) that is used to treat N rich water. Due to the conditions created in the spring bioreactor, the process of denitrification occurs, and N is removed from the water treated. The objective of this research is to estimate the regional abatement costs to remove legacy N using bioreactors. We identified 196 candidate springs for bioreactor installation that had a median spring flow of greater or equal to 100 m3 d-1 and greater or equal to 3 mg L-1. Under assumptions that 25% of the spring flow can be diverted to the bioreactor and a bioreactor N removal efficiency of 20%, we estimate that it would cost $3,325,400 yr-1 to abate 106,911 kg N yr-1. The driving factor of driving the unit costs of N removal is the amount of spring flow treated by the bioreactor. Further research is needed to understand how to optimize bioreactor performance and the benefits of increasing the percentage of spring flow treated given the impact these two factors on the cost-effectiveness of spring bioreactors in removing N.

No description available.

No description available.

The biological treatment of metalworking fluids (MWFs) is a cost effective alternative to conventional waste disposal processes. While research has proven that this process is capable of treating large volumes of wastes with high organic concentrations, there are uncertainties about the mechanisms by which the treatment occurs, and there are limitations that must be overcome. There is a need to understand the importance of the mechanisms by which carbon (and hence COD) is removed from the wastewater. This will allow for waste practitioners to make better decisions for optimizing the process, and for disposing of waste (i.e sludge) that is generated. The biological treatment process is also susceptible to biocides present within formulations. These compounds either need to be removed before the treatment process, or the bioreactors need to be made more resistant to them to ensure that their presence does not hinder the reactor functioning. This study aims to answer the uncertainties about the carbon removal mechanisms involved in the treatment of oil-containing MWFs. In the first experimental chapter, it is shown that the predominant mechanism of carbon removal is oil/water separation induced by emulsifier degradation, and hence the bioprocess treatment rate is significantly affected by the biodegradability of surfactants and by the presence of cations found naturally in the water that used to prepare the emulsions. The study then provides insights into the potential that coagulation and coalescence has for removing inhibitory components commonly found in MWFs. Coagulation and coalescence is shown to effectively remove biocides with low aqueous solubility (iodopropynyl butylcarbamate) and those that partition themselves into the oil phase (o-phenyl phenate and its sodium salt). Finally, to improve the resistance of reactors to inhibitory compounds, factors influencing the development of fixed-film reactors are investigated. A micro-cosmic system is used to study the both physico-chemical effects and nutritional factors on the development of biofilm reactors. It is shown that biofilm yields can be controlled through pH adjustment, and that these yields are maximized with phosphate stimulation and ammonium limitation. It is then shown that fixed-film reactors are able to treat metalworking fluids even under conditions deemed to be inhibitory. In summary, this project provides insights into further understanding and enhancing the biological treatment of MWFs.

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.

published_or_final_version / abstract / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy