Many industrial activities discharge sulphate- and metal-containing wastewaters, including the manufacture of pulp and paper, mining and mineral processing, and petrochemical industries. Acid mine drainage (AMD) is an example of such sulphate- and metal-containing waste streams. Formation of AMD is generally the result of uncontrolled oxidation of the sulphide minerals present in the terrain in which the drainage flows with concomitant leaching of the metals. Acid mine drainage (AMD) and other sulphate- and metal-containing waste streams are amenable to active biological treatment. Anaerobic reduction of sulphate, reaction of produced sulphide with metal ions present in the waste stream, and biooxidation of excess sulphide are three main sub-processes involved in the active biotreatment of AMD. Anaerobic reduction of sulphate can be achieved in continuous stirred tank bioreactors with freely suspended cells or in immobilized cell bioreactors. The application of freely suspended cells in a continuous system dictates a high residence time to prevent cell wash-out, unless a biomass recycle stream is used. In an immobilized cell system biomass residence time becomes uncoupled from the hydraulic residence time, thus operation of bioreactor at shorter residence times becomes possible. In the present work, kinetics of anaerobic sulphate reduction was studied in continuous immobilized cell packed-bed bioreactors. Effects of carrier matrix, concentration of sulphate in the feed and sulphate volumetric loading rate on the performance of the bioreactor were investigated. The bioreactor performance, in terms of sulphate reduction rate, was dependent on the nature of the carrier matrix, specifically the total surface area which was provided by the matrix for the establishment of biofilm. Among the three tested carrier matrices, sand displayed the superior performance and the maximum volumetric reduction rate of 1.7 g/L-h was achieved at the shortest residence time of 0.5 h. This volumetric reduction rate was 40 and 8 folds faster than the volumetric reduction rates obtained with glass beads (0.04 g/L-h; residence time: 28.6 h) and foam BSP (0.2 g/L-h; residence time: 5.3 h), respectively. Further kinetic studies with sand as a carrier matrix indicated that the extent of volumetric reduction rate was dependent on the feed sulphate concentration and volumetric loading rate. At a constant feed sulphate concentration, increases in volumetric loading rate caused the volumetric reduction rate to pass through a maximum, while increases in feed sulphate concentrations from 1.0 g/L to 5.0 g/L led to lower volumetric reduction rates. The maximum volumetric reduction rates achieved in the bioreactors fed with initial sulphate concentration of 1.0, 2.5 and 5.0 g/L were 1.71, 0.82 and 0.68 g/L-h, respectively. The coupling of lactate utilization to sulphate reduction was observed in all experimental runs and the rates calculated based on the experimental data were in close agreement with calculated theoretical rates, using the stoichiometry of the reactions involved. The maximum volumetric reduction rates achieved in the immobilized cell bioreactors were significantly faster than those reported for freely suspended cells employed in the stirred tank bioreactors.

Hydrogen sulphide (H2S) is a serious problem for many industries, including oil production and processing, pulp and paper, and wastewater treatment. In addition, H2S is usually present in natural gas and biogas. It is necessary to control the generation and release of H2S into the environment because H2S is corrosive, toxic, and has an unpleasant odour. In addition, the removal of H2S from natural gas and biogas is essential for preventing the emission of SO2 upon combustion of these gases. Physicochemical processes have been developed for the removal of H2S. These processes employ techniques such as chemical or physical absorption, thermal and catalytic conversion, and liquid phase oxidation. In comparison, biological processes for the removal of sulphide typically operate at ambient temperature and pressure, with the feasibility for the treatment of smaller streams, and the absence of expensive catalysts. The objective of the present work was to study the biooxidation of sulphide under denitrifying conditions in batch system and a continuous immobilized cell bioreactor using a mixed microbial culture enriched from the produced water of a Canadian oil reservoir. <p>In the batch experiments conducted at various initial sulphide concentrations, an increase in the sulphide oxidation and nitrate reduction rates was observed as the initial sulphide concentration was increased in the range 1.7 to 5.5 mM. An extended lag phase of approximately 10 days was observed when sulphide concentrations around or higher than 14 mM were used. This, when considered with the fact that the microbial culture was not able to oxidize sulphide at an initial concentration of 20 mM, indicates the inhibitory effects of sulphide at high concentrations.<p>The effect of the initial sulphide to nitrate concentrations ratio (ranging from 0.3 to 4.0) was also studied. As the initial sulphide to nitrate ratio decreased, the sulphide oxidation rates increased. The increasing trend was observed for initial nitrate concentrations in the range of 1.3 to 7.3 mM, corresponding to ratios of 4.08 to 0.83. The increase in nitrate reduction rates was more pronounced than that of the sulphide oxidation rates. However at nitrate concentrations higher than 7.3 mM (ratios lower than 0.83) the nitrate reduction rate remained constant. The percentage of sulphide that was oxidized to sulphate increased from 2.4% to 100% as the initial sulphide to nitrate ratio decreased from 4.08 to 0.42. This indicated that at ratios lower than 0.42, nitrate would be in excess and at ratios exceeding 4.08, nitrate would be limiting. In the continuous bioreactor systems, at sulphide loading rates ranging from 0.26 to 30.30 mM/h, sulphide conversion remained in the range of 97.6% to 99.7%. A linear increase in the volumetric oxidation rate of sulphide was observed as the sulphide loading rate was increased with the maximum rate being 30.30 mM/h (98.5% conversion). Application of immobilized cells led to a significant increase in oxidation rate of sulphide when compared with the rates obtained in a bioreactor with freely suspended cells. At nitrate loading rates ranging from 0.19 to 24.44 mM/h, the nitrate conversion ranged from 97.2% to 100% and a linear increase in volumetric reduction rate was observed as the nitrate loading rate was increased, with the maximum rate being 24.44 mM/h (99.7% conversion). <p>A second bioreactor experiment was conducted to investigate the effects of sulphide to nitrate concentrations ratio on the performance of the system. Sulphide conversion was complete at sulphide to nitrate ratios of 1.1 and 1.3, but decreased to 90.5% at the ratio of 3.1 and 65.0% at the ratio of 5.0, indicating nitrate was limiting for sulphide to nitrate ratios of 3.1 and 5.0. The increase in the sulphide to nitrate ratio (and the resulting limitation of nitrate) caused a decrease in the volumetric reaction rate of sulphide.<p>Nitrate conversion was complete at sulphide to nitrate ratios of 1.3, 3.1, and 5.0; however, at a ratio of 1.1, the conversion of nitrate dropped to 59.6%, indicating that nitrate was in excess, and sulphide was limiting. The volumetric reaction rate of nitrate decreased as the sulphide to nitrate ratio increased for ratios of 1.3, 3.1, and 5.0; this was due to the decrease in the nitrate loading rate. For sulphide to nitrate ratios of 1.1 and 1.3, 7.2% and 19.6% of the sulphide was converted to sulphate, respectively. At ratios of 3.1 and 5.0, no sulphate was generated. For ratios between 1.3 and 5.0, an increase in the ratio caused a decrease in the generation of sulphate.

Cyanide is a known toxic chemical, the production of plastics, electroplating, tanning, chemical syntheses, etc. At short-term exposure, cyanide causes rapid breathing, tremors, and long-term exposure to cyanide cause weight loss, thyroid effects, nerve damage and death. Although chemical and physical processes can be employed to degrade cyanide and its related compounds, they are often expensive and complex to operate. A proven alternative to these processes is biological treatment, which typically relies upon the acclimation and enhancement of indigenous microorganisms. Biological degradation of cyanide has often been offered as a potentially inexpensive and environmentally friendly alternative to conventional processes. The aims of first part of study were to evaluate the biodegradability of tetracyanonickelate (TCN) by Klebsiella oxytoca under anaerobic conditions. Results reveal that TCN can be biotransformed to methane by resting cells of K. oxytoca. Results also show that TCN biodegradation was inhibited by the addition of nitrate, nitrite, or ammonia at higher concentrations (5 and 10 mM). Moreover, it was found that the optimum pH for TCN conversion by K. oxytoca was about 7.1. Results from the fermenter experiment show that TCN can be completely degraded within 14 days. K. oxytoca is capable of using TCN as the nitrogen source under anaerobic conditions. TCN could be biotransformed to non-toxic end product (methane) by resting cells of K. oxytoca. Those studies provide us insight into the characteristics of TCN conversion by K. oxytoca under anaerobic conditions. In second part of this study, the technology of immobilized cells can be applied in biological treatment to enhance the efficiency and effectiveness of biodegradation. In this study, potassium cyanide (KCN) was used as the target compound and both alginate (AL) and cellulose triacetate (CT) gels were applied for the preparation of immobilized cells. The free suspension systems reveal that the cell viability was highly affected by initial KCN concentration and pH. Results show that immobilized cell systems could tolerate a higher level of KCN concentration and wider ranges of pH. In the batch experiments, the maximum KCN removal rates using alginate and cellulose triacetate immobilized beads were 0.108 and 0.101 mM h-1 at pH 7, respectively. Results also indicate that immobilized system can support a higher biomass concentration. Complete KCN degradation was observed after the operation of four consecutive degradation experiments with the same batch of immobilized cells. This suggests that the activity of immobilized cells can be maintained and KCN can be used as the nitrogen source throughout KCN degradation experiments. The maximum KCN removal rates using AL and CT immobilized beads in continuous-column system were 0.224 and 0.192 mM h-1 with initial KCN concentration of 3 mM, respectively. In third part of this study, a microbial process for the degradation of propionitrile by K. oxytoca was studied. The free and immobilized cells of K. oxytoca were then examined for their capabilities on degrading propionitrile under various conditions. The efficiency and produced metabolic intermediates and end-products of propionitrile degradation were monitored in bath and continuous bioreactor experiments. Results reveal that up to 100 mM and 150 mM of propionitrile could be removed completely by the free and immobilized cell systems, respectively. Furthermore, AL and CT immobilized cell systems show higher removal efficiencies in wider ranges of temperature (20-40¢XC) and pH (6-8) compared with the free cell system. Results also indicate that immobilized cell system could support a higher cell density to enhance the removal efficiency of propionitrile. Immobilized cells were reused in five consecutive degradation experiments, and up to 99% of propionitrile degradation was observed in each batch test. This suggests that the activity of immobilized cells can be maintained and reused throughout different propionitrile degradation processes. A two-step pathway was observed for the biodegradation of propionitrile. Propionamide was first produced followed by propionic acid and ammonia. Results suggest that nitrile hydratase and amidase were involved in the degradation pathways of K. oxytoca. In the continuous bioreactor, both immobilized cells were capable of removing 150 mM of propionitriles completely within 16 h, and the maximum propionitriles removal rates using AL and CT immobilized beads were 5.04 and 4.98 mM h-1, respectively. Comparing the removal rates obtained from batch experiments with immobilized cells (AL and CT were 1.57 and 2.18 mM h-1 at 150 mM of propionitrile, respectively), the continuous-flow bioreactor show higher potential for practical application. These findings would be helpful in designing a practical system inoculated with K. oxytoca for the treatment of cyanide-containing wastewater.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 152-171).

Regiomeric mixture of HMe2Si(CH2)3(i-Bu)6Si7O9(OH)3 (6), containing a Si-H group in one of the ligands of the silsesquioxane, was tethered onto a vinyl terminated hyperbranched poly(siloxysilane) polymer via a hydrosilation reaction to generate extremely active catalysts, P1-8 and c-P1-8. The synthesis of 6, in good yield, was accomplished via hydrosilation of CH2=CHCH2(i-Bu)7Si8O12 (1) to generate ClMe2Si(CH2)3(i-Bu)7Si8O12 (3) followed by the reduction of 3 with LiAlH4 to afford HMe2Si(CH2)3(i-Bu)7Si8O12 (4) where the base-catalyzed excision of one framework silicon was employed to generate a regiomeric mixture of 6. [Ti(NMe2){Et3Si(CH2)3(i-Bu)6Si7O12}] (7), [Ti(NMe2){HMe2Si(CH2)3(i-Bu)6Si7O12}] (8), [Ti(NMe2){(i-C4H9)7Si7O12}] (9) and [Ti(NMe2){(c-C6H11)7Si7O12}] (10) were synthesized via protonolysis of Ti(NMe2)4 with one equivalent of the trisilanol precursor in order to determine if the presence of isomers would be intrinsically different as compared to the uniformly substituted catalysts. Isomers 8 and 9, demonstrated lower activity as compared to the uniformly substituted catalysts 9 and 10, however the isomers still exhibited extremely high catalytic activity for the epoxidation of 1-octene using tert-butyl hydroperoxide (TBHP) relative to titanium catalysts used in industry. Additionally, 9, 10, P1-8 and c-P1-8 were very selective catalysts for the epoxidation of various olefins such as terminal (1-octene), cyclic (cyclohexene or 1-methylcyclohexene), and more demanding olefins (limonene or α-pinene) employing TBHP as the oxidant. Furthermore, P1-8 and c-P1-8 were recyclable with minimal loss of titanium however the catalysts could also be repaired if a loss in activity was observed. Preliminary epoxidation reactions employing P1-8 and c-P1-8 along with hydrogen peroxide (H2O2) as the oxidant were also explored using different solvents. P1-8 degraded quickly due to the hydrolysis of the titanium from the large amount of water present in the reaction mixture however c-P1-8 showed activity for the epoxidation of cyclohexene. Finally, regiomeric mixture of Ti(NMe2)(HS(CH2)3)(i-C4H9)6Si7O12) (13), was tethered onto gold nanoparticles for the conversion of propene to propylene oxide using molecular hydrogen and oxygen. While the catalysts showed low activity under our reaction conditions, numerous improvements can be investigated in order to improve upon the catalysts.

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2007. / Radhakrishna, Harish, Committee Member ; Zhu, Cheng, Committee Member ; LaPlaca, Michelle C., Committee Member ; Garca, Andrs J., Committee Chair ; Kowalczyk, Andrew P., Committee Member.

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Made available in DSpace on 2014-10-09T12:52:00Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:06Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Resumo: O presente trabalho apresenta um estudo de produção de ácido lático a partir de Lactobacillus rhamnosus imobilizado por aprisionamento em alginato de cálcio, com a utilização de soro de queijo como fonte de carbono alternativa à glicose encontrada tradicionalmente no meio MRS para bactérias láticas. A imobilização foi efetiva com 2 % de alginato, tendo eficiência de 99,99 %, e taxa de saída de células de 0,25 %, utilizando MRS como meio de cultivo. Estudou-se também o uso de fontes alternativas de nitrogênio como água de maceração de milho, Pro-Floo®, autolisado de levedura e sulfato de amônio. Os melhores resultados de produção e rendimento foram obtidos a partir da utilização de soro de queijo com as fontes de nitrogênio do MRS (extrato de levedura, peptona e extrato de carne), chegando a um rendimento (Yp/s) de 0,83, com produtividade de 0,90 g.L-1.h-1, seguido do cultivo com água de maceração de milho (AMM) e Pro-Floo®, com Yp/s de 0,72 e 0,57 respectivamente. No cultivo com água de maceração de milho a produção de ácido lático atingiu 119,04 g/L em 48 h. Com células livres, o melhor resultado de rendimento foi 0,73 quando de utilizou água de maceração de milho, com produtividade de 2,25 g.L-1.h-1 e produção de ácido lático de 107,89 g/L. Foram realizados dois ensaios utilizando uma modificação no alginato com ácido palmítico, para melhoria na viabilidade das células imobilizadas. Houve melhora no Yp/s quando se utilizou a alginato modificado com ácido palmítico passando de 0,72 para 0,79 no cultivo com AMM e de 0,57 para 0,67 quando se utilizou Pro-Floo®. Outro cultivo foi conduzido em reator de leito empacotado com imobilização em alginato recoberto de polietilenoimina, utilizando meio MRS. No reator pode-se observar a produção contínua de ácido lático até 72 horas com rendimento de 0,88 em 4 horas de cultivo atingindo uma concentração de 11,79 g/L de ácido lático. / Abstract: This work presents a study of lactic acid production by Lactobacillus rhamnosus immobilized by entrapment technique in calcium alginate, using whey as alternative carbon source, avoiding glucose use in the traditional MRS medium for lactic acid bacteria. Cell immobilization was effective using 2% of alginate, with efficiency of 99.99% and rate of cell release of 0.25 %. Alternative nitrogen sources like corn steep liquor (CSL), Pro-Floo®, autolyzed yeast and ammonium sulfate was also studied. The higher values of production and yield (Yp/s) were obtained in the cultivation with whey and the MRS nitrogen sources (yeast extract, peptone and meat extract), reaching an Yp/s of 0.83, and productivity of 0.90 g.L-1.h-1, followed by the cultivation with corn steep liquor and Pro-Floo®, with Yp/s of 0.72 and 0.57 respectively. With corn steep liquor, the lactic acid production reached 119.04 g/L in 48 h. In the culture with free cells the yield was 0.73 with corn steep liquor in 48 h, the productivity was 2.25 g.L-1.h-1 and production 107.89 g/L. Two experiments were done with a palmitolation of alginate to improve of immobilized cell viability. Increase in yield was obtained when palmitolation was employed; the yield increased from 0.72 to 0.79 in the cultivation using corn steep liquor, and from 0.57 to 0.67 when Pro-Floo® was used an alternative nitrogen source. Another experiment was realized in a packed-bed continuous reactor, with polyethyleneimine coated alginate beads, using MRS as culture medium. It was observed continuous lactic acid production until 72 h, with a yield of 0.88 in 4 hours reaching a lactic acid concentration of 11.79 g/L. / Orientador: Jonas Contiero / Coorientador: Cristina Jacques Bolner de Lima / Banca: Rubens Monti / Banca: Eliana Setsuko Kamimura / Mestre

The aim of this master thesis was to investigate a photochemical degradation of three representatives of parabens (methylparaben, ethylparaben and propylparaben) in aqueous solutions. Two experimental arragements were adopted in the study: a heterogeneous photocatalytic process on an immobilized TiO2 and a reaction in a homogeneous mixture; in the latter arrangement, the effect of Fe(III) concentrations was examined.