Thesis (Ph. D.)--Columbia University, 1931. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 33-34.

Thesis (Ph. D.)--Columbia University, 1931. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 33-34.

A novel rapid method for the determination of biochemical oxygen demand (BOD) has been developed. By replacing oxygen, the terminal electron acceptor in the microbial oxidation of organic substrate, with the ferricyanide ion, a significant increase in the rate of the biochemical reaction could be achieved. This arises from the high solubility of the ferricyanide ion (compared to oxygen); therefore allowing for elevated microbial populations without rapid depletion of the electron acceptor. Therefore, the BOD of a sample can be determined within 1-3 hours compared to 5-days with the standard BOD5 assay. A range of microorganisms were shown to be able to use the ferricyanide ion as an alternative electron acceptor for the biodegradation of a range of organic compounds in the ferricyanide mediated BOD (FM-BOD) assay. The most suitable biocatalyst in the FM-BOD method, however, was shown to be a mixture of microorganisms that was capable of degrading large amounts and types of compounds. These mixed consortia of microorganisms included a synthetic mixture prepared in our laboratory and two commercially available consortia, BODseedTM and Bi-ChemTM. When these seed materials were employed in the FM-BOD assay, the method was shown to closely estimate the BOD5 values of real wastewater samples. The linear dynamic working range of the FM-BOD method was also greatly extended compared to the standard BOD5 assay (nearly 50 times greater) and other oxygen based BOD biosensors. The immobilisation of the microbial consortia by both gel entrapment and freeze-drying methods was shown to greatly reduce the preparation and handling time of the mixed consortia for use in the FM-BOD method. Immobilisation of the mixed microbial consortium in LentiKats®, a PVA hydrogel, resulted in a marked increase in the stability of the biocatalyst. Diffusion limitations resulting from the gel matrix, however, reduced the rate and extent of the bioreaction as well as the linear dynamic working range of the method. Freeze-drying techniques were shown to circumvent some of the limitations identified with gel entrapment for the immobilisation of the mixed consortia. The freeze-dried consortia could be used off-the-shelf and demonstrated reduced diffusional restrictions. A marked decrease in the viability of the microorganisms was observed directly following the freeze-drying process and in subsequent storage. Carrageenan, however, was shown to afford a significant degree a protection to the cells during the freeze-drying process.

Microbial fuel cells (MFC) are an emerging renewable technology which converts complex organic matter to electrical power using microorganisms as the biocatalyst. A variety of biological relevant organic matters such as glucose, acetate and ethanol have been utilized for the successful operation of a MFC. In this regard, the investigation of a MFC inoculated with ethanol oxidizing bacteria is of particular interest for this research due to its ability to simultaneously produce electricity while reducing ethanol pollution (a type of volatile organic carbon (VOC) pollutant) with potential use in modified biological air pollution control technology such as biofiltration. In this research, ethanol-oxidizing microbial species isolated from soil and compost samples were identified, with Acinetobacter calcoaceticus being the dominant strain. In order to understand the metabolism of the anode microbial cells, which is considered to be the key dictating the performance of a MFC, a systematic analysis/optimization of the growth rate and biomass production for A. calcoaceticus were carried out. A maximum specific growth rate with a final biomass concentration of 1.68 g/l was derived when aerated at a rate of 0.68 vvm. It has been recognized that one of the principle constraints in increasing the current density of MFCs is the electron transfer from the bacteria to the anode. In this sense, the addition of a redox mediator, which facilitates the process of the electron transfer, is desired for the efficient operation of a MFC. Thionine, methylene blue (MB), resorufin and potassium ferricyanide that have been profusely utilized as effective mediator compounds in many MFC studies, however, specific information on the biomass sorption of these compounds was lacking and therefore were selected for this research. All mediators tested were reduced biologically in A. calcoaceticus inoculated samples as indicated by the color transition from the pigmented oxidized form to the colorless reduced form. Subsequent tests on mediator color removal revealed that physical adsorption by the biomass, aggregation as well as precipitation accounted for a significant portion of the color loss for thionine and MB. It was speculated that the fraction of the initial mediator concentration sequestered, aggregated and/or precipitated no longer contributed to the electron transfer process, resulting in a current production which was proportional to the measurable mediator concentration remained in anode solution. To verify this hypothesis, chronoamperometric measurements were conducted for various mediator systems at known initial and measurable concentrations. The data obtained on the current produced were in good agreement with the theoretical predictions calculated from the actual mediator concentration, suggesting that the current produced depended on the concentration of mediator remaining in solution. Finally, the microbial reduction kinetics and the cytotoxicity of potassium ferricyanide were analyzed. The reduction of potassium ferricyanide followed zero order kinetics with the specific reduction rate increased as the initial mediator concentration increased from 1 mM to 200 mM. Inhibitory effects on cell growth were observed at initial potassium ferricyanide concentration of 50 mM.

O dióxido de titânio (TiO2) é atualmente um dos catalisadores mais utilizados para remoção de poluentes em efluentes, devido a sua alta estabilidade química, baixo custo, não toxicidade e possibilidade de ativação por radiação solar. O ferricianeto ()63− é um dos complexos cianometálicos mais estáveis gerados nos efluentes da mineração aurífera. Nesta pesquisa se apresenta o estudo de degradação deste complexo por meio de fotolise, fotocatálise com TiO2, e fotocatalise assistida com peróxido (H2O2). Para conferir a degradação do complexo foram analisados ao final do processo, parâmetros químicos como quantificação de cianeto livre, formação de amônia, nitrato, assim como precipitação de ferro metálico. Os ensaios foram feitos no Laboratório de Fotoquímica e Superfícies-LAFOS da Universidade Federal Rio Grande do Sul por meio de uma lâmpada de irradiação UV, o reagente utilizado foi o ferricianeto de potássio [K3Fe(CN)6] grau analítico, preparado como uma solução sintética em condições próximas do pH dos efluentes de mineradoras, a pesquisa foi conduzida em condições de pressão e temperatura ambiente (1 atm e 25°C), testando diferentes concentrações de TiO2 e um analise sob irradiação solar. A partir de uma solução de 100 mg L-1 o efeito da fotólise demostrou que o complexo estudado apresenta uma grande estabilidade uma vez que em condições de irradiação UV (λ>300nm) foi observada uma baixa taxa de degradação após um período de 24 h, abaixo de 20%, enquanto em um sistema de fotocatálise heterogênea com TiO2 em condições alcalinas foram obtidas degradações de até 70%. O melhor resultado se atingiu no sistema de fotocatalise assistida com peroxido, sendo usado 2.5 vezes menos peroxido do que é utilizado na indústria, alcançando 83% degradação para um dos complexos mais estáveis formado pelo cianeto, o ferricianeto. Foram avaliados diferentes parâmetros para analisar o comportamento e degradação do complexo ferricianeto, como por exemplo a adsorção em fase escura do complexo sobre o catalisador; efeito da dosagem de TiO2, ação do H2O2 em baixa concentração, incidência da radiação UV em diferentes fontes com potência de 120 e 200 W e finalmente com radiação solar. Os resultados obtidos mostraram a influência do TiO2 junto com irradiação UV para atingir a degradação do complexo e formação de produtos menos tóxicos. / Titanium dioxide (TiO2) is one of the most frequently used catalysts applied for effluent treatment by pollution removal due to its high chemical stability, low cost, non-toxicity and the solar power is capable to activated it. Ferricyanide ()63− is one of the most stable cyanometallic complexes generated in the gold mining effluents. This research presents the study degradation of this complex by means of photolysis, photocatalysis with TiO2, and photocatalysis assisted with peroxide (H2O2). In order to verify the degradation of the complex, chemical parameters such as quantification of free cyanide, formation of ammonia, nitrate, as well as precipitation of metallic iron were analyzed at the end of the process. The tests were conducted at LAFOS (Surface and Photochemistry Laboratory) at UFRGS (Federal University of Rio Grande do Sul), using a UV irradiation lamp, the reagent used was potassium ferricyanide [K3Fe(CN)6] analytical grade, prepared as a synthetic solution with pH close to what is found at mining companies effluents. The tests were performed at normal temperature and pressure (1 atm e 25°C), testing different concentrations of TiO2 and an analysis under solar irradiation. From a solution of 100 mg L-1 the photolysis effect showed that the complex studied feature a high stability since under UV irradiation conditions (λ> 300 nm) a low degradation rate was observed after a period of 24 h, below 20%, whereas in a heterogeneous photocatalysis system with TiO2 under alkaline conditions degradations of up to 70% were obtained. The best result was obtained in the peroxide assisted photocatalysis system, using 2.5 times less peroxide than is used by the industry, reaching 83% degradation to one of the most stable complexes formed by cyanide, ferricyanide. Different parameters were used to analyze the degradation of ferricyanide complex, such as adsorption in dark stage over the catalyst; low concentration of H2O2, effects from TiO2 dosage, UV radiation incidence from different sources of 120 and 200W and finally solar radiation. The results obtained show the TiO2 influence along with UV irradiation to achieve degradation of the complex and less toxic products.

Microbial fuel cells were designed and operated using waste activated sludge as a substrate and as a source of microorganisms for the anodic chamber. Waste activated sludge provided a bacterial consortium predisposed to the solubilization of particulate matter and utilization of substrates commonly found in wastewater. Dissolved oxygen and ferricyanide were used as the electron acceptors in the catholytes. Microbial fuel cell comparisons were made while operating under identical conditions but using the two different electron acceptors. Comparisons were based on the electricity production observed during MFC operation, wastewater quality of the waste activated sludge anolytes and the community level physiological profiling of the microbial communities in the anolytes. Electrons liberated during substrate utilization in the anodic chamber traveled to the cathodic chamber where they reduced the electron acceptors. The anode and cathode chambers were connected by a Nafion ® proton exchange membrane to allow for cation migration. Various soluble carbon sources were dosed to the microbial fuel cells at measured intervals during operation via direct injection to the anolyte. During bovine serum albumin dosing, average power production levels reached 0.062 mW and 0.122 mW for the dissolved oxygen microbial fuel cell and the ferricyanide microbial fuel cell, respectively. These were 100% and 25% greater than the power production levels observed throughout the rest of the study. Increases in current production were observed following the dosing of sodium acetate, glucose and bovine serum albumin. No increase in current was observed following glycerol dosing. Sodium acetate dosing triggered an immediate response, while glucose and bovine serum albumin responded in approximately 2 minutes. A chemical oxygen demand mass balance was calculated for both microbial fuel cells. The lack of balance closure was attributed to unmeasured methane production. An accumulation of particulate waste activated sludge components was observed for both microbial fuel cells. The anolyte pH during operation was typically less than waste activated sludge pH, which was attributed to volatile fatty acid accumulation in the anolytes during fermentation processes. Community level physiological profiling was accomplished through the analysis of ecological data obtained with BIOLOG ® ECOplates. Samples were plated and analyzed under anaerobic conditions, mimicking the environment in the anode chamber of the MFCs. ECOplate data were transformed by a logarithmic function prior to principle component analysis. The community level physiological profiling indicated that shifts in the microbial community profile, as measured through the carbon source utilization patterns, occurred throughout acclimation and following the dosing of various carbon source substrates. Shifts due to glycerol dosing differed from shifts due to the dosing of sodium acetate, glucose and bovine serum albumin.

Microbial fuel cells were designed and operated using waste activated sludge as a substrate and as a source of microorganisms for the anodic chamber. Waste activated sludge provided a bacterial consortium predisposed to the solubilization of particulate matter and utilization of substrates commonly found in wastewater. Dissolved oxygen and ferricyanide were used as the electron acceptors in the catholytes. Microbial fuel cell comparisons were made while operating under identical conditions but using the two different electron acceptors. Comparisons were based on the electricity production observed during MFC operation, wastewater quality of the waste activated sludge anolytes and the community level physiological profiling of the microbial communities in the anolytes. Electrons liberated during substrate utilization in the anodic chamber traveled to the cathodic chamber where they reduced the electron acceptors. The anode and cathode chambers were connected by a Nafion ® proton exchange membrane to allow for cation migration. Various soluble carbon sources were dosed to the microbial fuel cells at measured intervals during operation via direct injection to the anolyte. During bovine serum albumin dosing, average power production levels reached 0.062 mW and 0.122 mW for the dissolved oxygen microbial fuel cell and the ferricyanide microbial fuel cell, respectively. These were 100% and 25% greater than the power production levels observed throughout the rest of the study. Increases in current production were observed following the dosing of sodium acetate, glucose and bovine serum albumin. No increase in current was observed following glycerol dosing. Sodium acetate dosing triggered an immediate response, while glucose and bovine serum albumin responded in approximately 2 minutes. A chemical oxygen demand mass balance was calculated for both microbial fuel cells. The lack of balance closure was attributed to unmeasured methane production. An accumulation of particulate waste activated sludge components was observed for both microbial fuel cells. The anolyte pH during operation was typically less than waste activated sludge pH, which was attributed to volatile fatty acid accumulation in the anolytes during fermentation processes. Community level physiological profiling was accomplished through the analysis of ecological data obtained with BIOLOG ® ECOplates. Samples were plated and analyzed under anaerobic conditions, mimicking the environment in the anode chamber of the MFCs. ECOplate data were transformed by a logarithmic function prior to principle component analysis. The community level physiological profiling indicated that shifts in the microbial community profile, as measured through the carbon source utilization patterns, occurred throughout acclimation and following the dosing of various carbon source substrates. Shifts due to glycerol dosing differed from shifts due to the dosing of sodium acetate, glucose and bovine serum albumin.

The reversible reduction of hexacyanoferrate(III) to the Fe(II) form is a well-known standard in electrochemistry. It is however reported to be highly dependent on the solvent environment.[i] This electrochemical project has aimed to examine the behaviour of ferricyanide in aprotic environment by changing the solvent to acetonitrile, a medium polar solvent with a high dielectric constant. The method used for research is cyclic voltammetry. Ferricyanide has been examined in aqueous and aprotic solvent and has been studied in comparison to ferrocene, which is a well-known chemical substance. When studying ferricyanide in acetonitrile solvent under inert conditions, a completely new voltammetric picture was drawn where the standard reduction potential in aqueous solvent of 43 mV (SCE) was dramatically lowered and a new redox reaction with a higher reduction potential seemed to be present at -97mV (Ag/Ag+) when ferricyanide went through redox process from 0 V to +1.3 V to -0.5 V and back to 0V again. When examining the redox process an EC reaction was found to be coupled to the new peak. This process was studied within the time limit for the project. Some properties of the possible chemical has been presented and the conclusions are discussed in the report. Suggestions are made for how to move forward with the research. [i] (a) Gutmann V., Gritzner G., and Danksagmuller K., Inorganica Chimica Acta, 17 1976 81; (b) Noftle R.E. and Pletcher D., Journal of Electroanalytical Chemistry, 1990 273, 293.

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