Дисертації з теми "Dissolved oxygen Dam removal"

Dans le contexte de la rivière Sélune en France, où deux barrages sont en cours de retrait pour rétablir la continuité hydro-sédimentaire de la rivière, cette thèse s'est fixée pour objectif de comprendre les impacts potentiels de ces changements sur la dynamique de la zone hyporhéique. Cette zone, cruciale dans les cycles hydrologiques ainsi que pour la reproduction de certaines espèces de poisson, demeure mal comprise du fait du faible nombre de donnée disponibles. Pour pallier à ce problème, un réseau de capteurs autonomes mesurant différentes variables physico-chimiques a été déployé à partir d'octobre 2021, sur une durée de 2 ans. La méthodologie de cette étude repose sur l'analyse des gradients physico-chimiques verticaux dans les sédiments du lit de la rivière, en se penchant sur l'oxygène et la conductivité. L'hétérogénéité de la perméabilité a également été examinée grâce à des mesures de conductivité électrique. Les résultats ont révélé des variations spatiales significatives de la perméabilité du lit. En particulier, l'impact du flux sédimentaire lié à l'arasement des barrages a été observé, provoquant une diminution de la perméabilité dans certaines zones. En ce qui concerne l'oxygène dissous, les variations observées sont liées aux régimes d'infiltration et d'exfiltration, avec possiblement des baisses temporaires dues à l'activité microbienne en réponse à l'apport de matière organique. De plus, l'arrivée de sédiments en mai 2022 semble avoir entraîné une période prolongée d'anoxie, avec potentiellement des conséquences majeures pour la faune aquatique. Cette recherche a contribué à une meilleure compréhension de la zone hyporhéique et a souligné l'impact significatif du flux sédimentaire sur la perméabilité, la dynamique de l'oxygène et le phénomène de colmatage. Elle a également ouvert de nouvelles perspectives pour l'analyse des propriétés hydrothermiques du lit de la rivière, des flux d'eau et l'utilisation de mesures de conductivité électrique pour estimer la profondeur des échanges nappe-rivière, ainsi que le développement de modèles théoriques pour prédire le transport des éléments dissous et leur dégradation
In the context of the Selune River in France, where two dams are currently being removed to restore hydro-sedimentary continuity in the river, this thesis aimed at understanding the potential impacts of these changes on the dynamics of the hyporheic zone. This zone, crucial for the reproduction of certain species and economic activities, requires in-depth monitoring. To achieve this, a network of autonomous sensors measuring various physicochemical variables was deployed starting in October 2021, for a duration of 2 years. The methodology of this study is based on the analysis of vertical physicochemical gradients in the riverbed sediments, focusing on oxygen and conductivity. The heterogeneity of permeability was also examined through measurements of electrical conductivity. The results revealed significant spatial variations in bed permeability. Specifically, the impact of sediment transport released by the dam removal was observed, causing a decrease in permeability in certain areas. Regarding dissolved oxygen, local variations were related to infiltration and exfiltration regimes, with temporary decreases due to microbial activity in response to organic matter input. Furthermore, the arrival of sediments in May 2022 led to an extended period of anoxia, with potentially significant consequences for aquatic fauna. This research has contributed to a better understanding of the hyporheic zone and emphasized the significant impact of sediment transport on permeability, oxygen dynamics, and clogging phenomena. It has also opened new perspectives for the analysis of hydrothermal properties of the riverbed, water flow, and the use of electrical conductivity measurements to estimate the depth of groundwater-river exchanges, as well as the development of theoretical models to predict the transport and degradation of dissolved elements

A pilot scale nitrogen (N) removal system was constructed and operated for approximately 365 days and was designed to remove inorganic total ammonia nitrogen (TAN) from solids-separated dairy manure. An anaerobic fermenter, upstream of the N removal reactor, produced volatile fatty acids (VFAs), to be used as an electron donor to fuel denitrification, and TAN at a COD:N ratio of 18:1. However, sufficient amounts of non-VFA COD was produced by the fermenter to fuel the denitrification reaction at an average NO3- removal rate of 5.3 ± 2 mg/L NO3--N. Total ammonia N was removed from the fermenter effluent in an N removal reactor where a series of aerobic and anoxic zones facilitated aerobic TAN oxidation and anoxic NO3- and NO2- reduction. The minimum dissolved oxygen (DO) concentration allowing for complete TAN removal was found to be 0.8 mg/L. However, TAN removal rates were less than predicted using default nitrifying kinetic parameters in BioWin®, a biological modeling simulator, which indicated the presence of a nitrification inhibitor in fermented dairy manure. Furthermore, an N balance during the aerobic zone indicated that simultaneous nitrification-denitrification (SND) was occurring in the aerobic zone of the N removal reactor and was most apparent at DO concentrations below 1.3 mg/L. A series of nitrite generation rate (NGR) experiments confirmed the presence of an inhibitor in fermented dairy manure. A model sensitivity analysis determined that the most sensitive ammonia oxidizing bacteria (AOB) kinetic parameters were the maximum specific growth rate, , and the substrate half saturation coefficient, . Nitrifying inhibition terms of competitive, non-competitive, mixed competitive, and un-competitive were applied to the growth rate equation in BioWin® but an accurate representation of the observed TAN removal rates in the pilot scale system could not be found by adjusting the kinetic parameters alone. Reducing the default BioWin® hydrolysis rate by approximately 50% produced a more accurate calibration for all inhibition terms tested indicating that the hydrolyization of organic N in dairy manure is less than typical municipal waste water.
Master of Science

Anammox is one of the main processes discovered quite recently for removal of ammonium from wastewater. Anammox process is cost effective, in that low energy and carbon source is needed. Partial nitritation is a perquisite for anammox in wastewater treatment for removal nitrogen and therefore partial nitritation/Anammox technology is studied substantially and applied in full-scale. However, the technology at present can only be used to treat high rich ammonium streams. Application of Anammox for treatment of low ammonium wastewater is not possible because of low yield of Anammox bacteria. The study aimed at devising strategies for using the Anammox technology to treat wastewater streams with low concentration of ammonium nitrogen. The objective was to get systems that could concentrate ammonium from low ammonium waste streams, so as to be able to treat it with partial nitritation/Anammox process. Two methods were used to concentrate ammonium: ion exchange and reverse osmosis. Ion exchange method was used to concentrate UASB effluents of about 24 - 40 mg NH4-N/l to 188 - 367 mg  NH4-N/l respectively which is about 9 times the initial concentrations. At VRF 5, 163 mg  NH4-N/l concentrate was attained from 41.8 mg  NH4-N/l RO feed. Results also showed that concentrates from both methods are able to be treated with partial nitritation/Anammox technology. However it took more than 32 hours to complete treatment of ion exchange concentrates while it took less than 24 hours to finish the partial nitritation/Anammox process of RO concentrates. The longer time taken can be attributed to high salinity of the concentrates which is as a result of NaCl which was used for regeneration in ion exchange process. Both ion exchange and reverse osmosis are viable methods for concentrating ammonium from UASB effluents. Dissolved oxygen was very important factor that influenced the biological process.

Bench and pilot scale determinations of the volumetric oxygen transfer coefficient, K_La, were performed on an improved A²/O biological nutrient removal (BNR) pilot plant. Effluent from a full scale primary clarifier, used as pilot plant influent, was found to have an alpha (ratio of process to clean water K_La) of 0.71 as determined in a 21 liter bench scale reactor and an alpha of 0.332 as determined in a 0.45 m³ aeration basin of the 2.4 m³ pilot plant. Alpha of a 1:1 mixture of primary clarifier effluent with pilot plant return activated sludge was determined to be 0.94 at bench scale and 0.71 at pilot scale. An assay of alphas through the initial non aerated treatment zones of the pilot plant using the bench scale reactor indicated that alphas peaked in the effluent of the first anaerobic zone (alpha equal to 1.01) and were lower in the second anaerobic zone and first anoxic zone. An assay of alphas in the three pilot plant series sideline aeration basins indicated that alpha was maximum in the first aeration basin (alpha equal to 0.905) and were lower in the second and third aeration basins (0.716 and 0.661 respectively). A consistent increase in average surface tension was noted from the first to second to third aeration basins, however the differences were not statistically significant. A comparison of pilot plant alphas determined in the first aeration basin following anaerobic nominal hydraulic retention times of 0.0, 0.21, 0.43, and 0.64 hours yielded alpha values of 0.71, 0.94, 0.64, and 0.74 respectively. Like the assay using the bench scale reactor, the alpha values at pilot scale peaked following treatment in only one anaerobic zone (nominal HRT of 0.21 hours). The study concludes that short exposures in an initial anaerobic reactor as required for biological phosphorus removal may benefit oxygen transfer efficiency through increased alphas, however the benefits of long periods of anaerobic reaction time (over 0.43 hours) are uncertain.
Master of Science

Le sulfure d'hydrogène (H2S) et le méthyle-mercaptan (MM) sont les contaminants odorants les plus abondants parmi le quatuor qui compose les soufres réduits totaux (SRT) (H2S, CH3SH, (CH3)2S, (CH3)2S2) dans les émissions atmosphériques des industries papetières Kraft. L'association de SRT avec suffisamment d'oxygène peut être exploitée sur la base de la chimie du fer, pour convertir les SRT gazeux en produits non-volatils et non-odorants. Le procédé utilise l'oxyde-hydroxyde de Fe/Ce (Fe/CeOx) dans des solutions alcalines où l'absorption oxydative de H2S et de MM (sous forme d’ hydrosulfure et de méthyle mercapture) est favorisée. Des protocoles d'électrophorèse capillaire ont été développés pour la séparation, l'identification et la quantification de l’hydrosulfure, du méthyle mercapture, des polysulfures, du thiosulfate, du sulfate, du sulfite et du tétrathionate. La cinétique et le mécanisme de la réaction anoxique entre l’hydrosulfure et le Fe/CeOx ont été étudiés aux pH [8.0-11.0] dans un réacteur batch liquide-solide. La plupart du Fe(II) produit à pH = 9.5 reste associée à la surface de l'oxyde dans l’échelle de temps des expériences. L’hydrosulfure a été converti en thiosulfate, polysulfures et, probablement, en soufre élémentaire, alors que le Fe2+ lixivié et le thiosulfate ont montré une production équimolaire pour pH ≥ 9.5. Un mécanisme de réaction détaillé pour l'oxydation anoxique d’hydrosulfure par le Fe/CeOx a été proposé pour expliquer la formation des produits ci-dessus et dont un modèle cinétique a été dérivé pour décrire les vitesses de lixiviation du Fe(II) et de consommation d’hydrosulfure. En conditions oxiques à pH [8.5-11.0], le Fe/CeOx oxyde l’hydrosulfure via une voie combinée hétérogène-homogène pour former les mêmes produits qu’en anoxique. L'oxygène accélère l'oxydation de l’hydrosulfure par le Fe/CeOx par un facteur de plus de trois en comparaison avec la réaction anoxique. L'oxygène assume un double rôle : d'abord, il ré-oxyde le fer de Fe(II) à Fe(III); en second lieu, il favorise l'oxydation de l`hydrosulfure vers les polysulfures et de ces-ci vers le thiosulfate, un produit non-volatile et non-odorant. L'oxydation du méthyle mercapture par Fe/CeOx a été étudiée aux différentes valeurs du pH [10.5-12] en conditions anoxique et oxique. Des conversions de mercapture allant jusqu'à 100% ont été obtenues en conditions oxiques bien que la conversion du mercapture se soit avérée tributaire de la quantité d'oxygène dissous. L'interférence avec l’hydrosulfure co-mélangé avec le mercapture a causé une inhibition dans la conversion des deux polluants. Une telle inhibition est due aux polysulfures naissants formés par l'oxydation de l’hydrosulfure. L'oxydation du méthyle mercapture par le système Fe/CeOx/O2 n'a pas affecté la capacité de régénération du Fe(III) de surface par l'oxygène dissous. Fe/CeOx semble être un matériau très prometteur pour un éventuel procédé de lavage-oxydatif pour l’élimination du méthyle mercaptan dans les émissions des industries papetières de type Kraft.
Hydrogen sulfide (H2S) and methyl mercaptan (MM) are the most abundant odor contaminants among the Total Reduced Sulfur (TRS) quartet (H2S, CH3SH, (CH3)2S, (CH3)2S2) contained in the Kraft mill atmospheric emissions. The association of TRS with sufficient oxygen could be taken advantage of, based on the iron chemistry, to convert TRS gases to odorless non-volatile products. The process uses Fe/Ce oxide-hydroxide (Fe/CeOx) slurried in alkaline solutions where both H2S and MM oxidative absorption (in the form of hydrosulfide and methyl mercaptide) is promoted. Capillary electrophoresis protocols were developed for the separation, identification and quantification of hydrosulfide, methyl mercaptide, polysulfides, thiosulfate, sulfate, sulfite and tetrathionate. The kinetics and mechanism of the anoxic reaction between hydrosulfide and Fe/CeOx were studied for pH [8.0-11.0] in a batch slurry reactor. Most of Fe(II) produced at pH = 9.5 remained associated with the oxide surface in the time-frame of the experiments. Hydrosulfide was converted into polysulfides, thiosulfate and, probably, elemental sulfur, while the leached Fe2+ and thiosulfate dovetailed equimolarly. A detailed reaction pathway of the anoxic oxidation of hydrosulfide by Fe/CeOx was proposed for explaining the formation of above products and whereof a kinetic model was derived to depict the Fe2+ leaching and hydrosulfide consumption rates. In oxic conditions at pH [8.5-11.0], Fe/CeOx will oxidize hydrosulfide via a combined heterogeneous-homogenous pathway to yield the same products as in anoxia. Oxygen enhanced Fe/CeOx-promoted hydrosulfide oxidation by more than a factor three when compared with anoxic reaction. Oxygen is believed to have a double role: first, it re-oxidizes iron from Fe(II) to Fe(III); second, it promotes oxidation of hydrosulfide to polysulfides which in turn transforms into non-volatile, non-odorous thiosulfate. The reaction between methyl mercaptide and Fe/CeOx was studied at different pH values [10.5-12] both in anoxic and oxic conditions. Up to 100% conversions of mercaptide were obtained in oxic conditions, though the mercaptide conversion was found to be tributary to the dissolved oxygen. Interference with hydrosulfide co-mixed with mercaptide caused an inhibition in the conversion for both pollutants, due to the incipient polysulfides formation. The oxidation of methyl mercaptide by the Fe/CeOx/O2 system did not affect the re-oxidative regeneration of surface Fe(III) by O2. Fe/CeOx appears to be a very promising material for a redox-scrubbing process targeting the TRS emissions from Kraft mills, via in situ regeneration of Fe(III) sites by O2.
Inscrit au Tableau d'honneur de la Faculté des études supérieures

Tableau d'honneur de la Faculté des études supérieures et postdoctorales, 2006-2007
Le sulfure d'hydrogène (H2S) et le méthyle-mercaptan (MM) sont les contaminants odorants les plus abondants parmi le quatuor qui compose les soufres réduits totaux (SRT) (H2S, CH3SH, (CH3)2S, (CH3)2S2) dans les émissions atmosphériques des industries papetières Kraft. L'association de SRT avec suffisamment d'oxygène peut être exploitée sur la base de la chimie du fer, pour convertir les SRT gazeux en produits non-volatils et non-odorants. Le procédé utilise l'oxyde-hydroxyde de Fe/Ce (Fe/CeOx) dans des solutions alcalines où l'absorption oxydative de H2S et de MM (sous forme d’ hydrosulfure et de méthyle mercapture) est favorisée. Des protocoles d'électrophorèse capillaire ont été développés pour la séparation, l'identification et la quantification de l’hydrosulfure, du méthyle mercapture, des polysulfures, du thiosulfate, du sulfate, du sulfite et du tétrathionate. La cinétique et le mécanisme de la réaction anoxique entre l’hydrosulfure et le Fe/CeOx ont été étudiés aux pH [8.0-11.0] dans un réacteur batch liquide-solide. La plupart du Fe(II) produit à pH = 9.5 reste associée à la surface de l'oxyde dans l’échelle de temps des expériences. L’hydrosulfure a été converti en thiosulfate, polysulfures et, probablement, en soufre élémentaire, alors que le Fe2+ lixivié et le thiosulfate ont montré une production équimolaire pour pH ≥ 9.5. Un mécanisme de réaction détaillé pour l'oxydation anoxique d’hydrosulfure par le Fe/CeOx a été proposé pour expliquer la formation des produits ci-dessus et dont un modèle cinétique a été dérivé pour décrire les vitesses de lixiviation du Fe(II) et de consommation d’hydrosulfure. En conditions oxiques à pH [8.5-11.0], le Fe/CeOx oxyde l’hydrosulfure via une voie combinée hétérogène-homogène pour former les mêmes produits qu’en anoxique. L'oxygène accélère l'oxydation de l’hydrosulfure par le Fe/CeOx par un facteur de plus de trois en comparaison avec la réaction anoxique. L'oxygène assume un double rôle : d'abord, il ré-oxyde le fer de Fe(II) à Fe(III); en second lieu, il favorise l'oxydation de l`hydrosulfure vers les polysulfures et de ces-ci vers le thiosulfate, un produit non-volatile et non-odorant. L'oxydation du méthyle mercapture par Fe/CeOx a été étudiée aux différentes valeurs du pH [10.5-12] en conditions anoxique et oxique. Des conversions de mercapture allant jusqu'à 100% ont été obtenues en conditions oxiques bien que la conversion du mercapture se soit avérée tributaire de la quantité d'oxygène dissous. L'interférence avec l’hydrosulfure co-mélangé avec le mercapture a causé une inhibition dans la conversion des deux polluants. Une telle inhibition est due aux polysulfures naissants formés par l'oxydation de l’hydrosulfure. L'oxydation du méthyle mercapture par le système Fe/CeOx/O2 n'a pas affecté la capacité de régénération du Fe(III) de surface par l'oxygène dissous. Fe/CeOx semble être un matériau très prometteur pour un éventuel procédé de lavage-oxydatif pour l’élimination du méthyle mercaptan dans les émissions des industries papetières de type Kraft.
Hydrogen sulfide (H2S) and methyl mercaptan (MM) are the most abundant odor contaminants among the Total Reduced Sulfur (TRS) quartet (H2S, CH3SH, (CH3)2S, (CH3)2S2) contained in the Kraft mill atmospheric emissions. The association of TRS with sufficient oxygen could be taken advantage of, based on the iron chemistry, to convert TRS gases to odorless non-volatile products. The process uses Fe/Ce oxide-hydroxide (Fe/CeOx) slurried in alkaline solutions where both H2S and MM oxidative absorption (in the form of hydrosulfide and methyl mercaptide) is promoted. Capillary electrophoresis protocols were developed for the separation, identification and quantification of hydrosulfide, methyl mercaptide, polysulfides, thiosulfate, sulfate, sulfite and tetrathionate. The kinetics and mechanism of the anoxic reaction between hydrosulfide and Fe/CeOx were studied for pH [8.0-11.0] in a batch slurry reactor. Most of Fe(II) produced at pH = 9.5 remained associated with the oxide surface in the time-frame of the experiments. Hydrosulfide was converted into polysulfides, thiosulfate and, probably, elemental sulfur, while the leached Fe2+ and thiosulfate dovetailed equimolarly. A detailed reaction pathway of the anoxic oxidation of hydrosulfide by Fe/CeOx was proposed for explaining the formation of above products and whereof a kinetic model was derived to depict the Fe2+ leaching and hydrosulfide consumption rates. In oxic conditions at pH [8.5-11.0], Fe/CeOx will oxidize hydrosulfide via a combined heterogeneous-homogenous pathway to yield the same products as in anoxia. Oxygen enhanced Fe/CeOx-promoted hydrosulfide oxidation by more than a factor three when compared with anoxic reaction. Oxygen is believed to have a double role: first, it re-oxidizes iron from Fe(II) to Fe(III); second, it promotes oxidation of hydrosulfide to polysulfides which in turn transforms into non-volatile, non-odorous thiosulfate. The reaction between methyl mercaptide and Fe/CeOx was studied at different pH values [10.5-12] both in anoxic and oxic conditions. Up to 100% conversions of mercaptide were obtained in oxic conditions, though the mercaptide conversion was found to be tributary to the dissolved oxygen. Interference with hydrosulfide co-mixed with mercaptide caused an inhibition in the conversion for both pollutants, due to the incipient polysulfides formation. The oxidation of methyl mercaptide by the Fe/CeOx/O2 system did not affect the re-oxidative regeneration of surface Fe(III) by O2. Fe/CeOx appears to be a very promising material for a redox-scrubbing process targeting the TRS emissions from Kraft mills, via in situ regeneration of Fe(III) sites by O2.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
In wastewater treatment, activated sludge systems have been a technology widely applied as secondary treatment. During this step, which has a strong biological aspect, it is necessary to introduce oxygen supply for the maintenance of metabolic activity of the bacteria through the aerators. Aeration devices are responsible for most of the energy consumption in this stage. In this background, the influence of three aeration intensities (atmospheric air flow 3.5, 7.0 and 10.5 L.min-1) and the concentration of dissolved oxygen (DO) on the dimension of activated sludge flocs as well as on the efficiency of organic matter removal were assessed using a traditional activated sludge system which was fed with synthetic domestic wastewater. Samples were taken weekly from the three units that make up the system feed, aeration and storage tank in order to verify the Chemical Oxygen Demand (COD). It was established the process efficiency through a comparison between the initial and final COD. Besides the parameters already mentioned, this monitoring work on activated sludge batch system was also observed by Mixed Liquor Suspend Solids (MLSS), Volatile Suspend Solids (VSS), pH and temperature measures. The results have showed a maximum removal efficiency around 75% in the first aeration sequence and approximately 85% for the second and third one. For the first aeration, the DO concentration remained higher than 3.0 mg.L-1 and a diameter range from 10 to 60 μm was observed. In the second e third sequence, the DO concentration remained higher than 4.0 mg.L-1 with a diameter range of 10 until 200 μm. Although the sequence 1 and 2 have presented similar performances for organic matter removal, the sequence 2 promoted a regular floc size distribution and with lower values of Sludge Volumetric Index (SVI) meaning a better flocculating ability. In addition, the results reaffirmed what the literature has reported: higher DO concentrations produce flocs with greater dimensions
No tratamento de ?guas residu?rias, os sistemas de lodos ativados t?m sido uma tecnologia largamente aplicada como tratamento secund?rio. Durante essa etapa, a qual possui uma caracter?stica fortemente biol?gica, ? necess?rio o fornecimento de oxig?nio para a manuten??o da atividade metab?lica das bact?rias atrav?s de aeradores. Os dispositivos de aera??o s?o respons?veis pela maior parte do consumo de energia ao longo dessa fase. Nesse contexto, a influ?ncia de tr?s intensidades de aera??o (vaz?o de ar atmosf?rico de 3,5, 7,0 e 10, 5 L.min-1) e a concentra??o de oxig?nio dissolvido (OD) sobre a dimens?o de flocos de lodo ativado, e bem como sobre a efici?ncia de remo??o foram avaliadas utilizando um sistema tradicional de lodos ativados alimentado com efluente dom?stico sint?tico. Amostras foram retiradas semanalmente das tr?s unidades que compunham o sistema tanque de alimenta??o, de aera??o e de armazenamento para verificar a Demanda Qu?mica de Oxig?nio (DQO). A efici?ncia do processo foi estabelecida atrav?s da compara??o entre a DQO inicial e final. Al?m dos par?metros j? mencionados, este trabalho de monitoramento do sistema de lodos ativados de bancada foi observado tamb?m por meio de medi??es de S?lidos em Suspens?o Totais (SST) e Vol?teis (SSV), pH e temperatura. Os resultados mostraram uma efici?ncia m?xima de remo??o de quase 75% na primeira sequ?ncia de aera??o e aproximadamente 85% para a segunda e terceira sequ?ncias. Para a primeira aera??o, a concentra??o de OD manteve-se maior que 3,0 mg.L-1 e uma faixa de di?metro de 10 a 60 μm foi observada, enquanto que na segunda e terceira sequ?ncia, a concentra??o de OD permaneceu superior a 4,0 mg.L-1 com uma faixa de di?metro de 10 a 200 μm. Embora a sequ?ncia 2 e 3 tenham apresentado, ambas, desempenhos similares para remo??o de mat?ria org?nica, a sequ?ncia 3 promoveu uma distribui??o de tamanho de flocos mais regular e com baixos valores de ?ndices Volum?tricos do Lodo (IVL), configurando em uma melhor habilidade de sedimenta??o. Em adi??o, os resultados reafirmam o que literatura tem relatado, maiores concentra??es de OD produzem flocos com maiores dimens?es

Объектом исследования являлось вещество натриевая соль 2-этилтио-6-нитро-1,2,4-триазоло-[5,1-c]-1,2,4-триазин-7-она, дигидрат (УПИ-802). Цель работы: количественное определение лекарственного вещества натриевой соли 2-этилтио-6-нитро-1,2,4-триазоло-[5,1-c]-1,2,4-триазин-7-она дигидрата методом вольтамперометрии. В случае УПИ-802 наиболее полезным для количественного определения является сигнал электровосстановления нитрогруппы. Исследованы процессы восстановления нитрогруппы исследуемого вещества в водных и апротонных растворах с применением вольтамперометрии в условиях физического удаления растворенного кислорода и без удаления кислорода. Установлено, что скорость восстановления УПИ-802 контролируется диффузией, процесс восстановления нитрогруппы является необратимым и проходит в две стадии в буферном растворе Бриттона-Робинсона. Первая волна восстановления, которая лежит в области потенциалов -0,31 – (-0,8) В, соответствует присоединению 4 электронов. Обнаружено, что электровосстановление нитрогруппы протекает с предшествующим протонированием. Выбран оптимальный режим регистрации аналитического сигнала исследуемого вещества УПИ-802 на стеклоуглеродном электроде в условиях химического способа удаления растворенного кислорода – квадратно-волновой с амплитудой импульса 0,05 В, частотой импульса 35 Гц. Показана возможность применения толстопленочных углеродсодержащих электродов для определения исследуемого вещества методом квадратно-волновой вольтамперометрии. Выполнена оценка показателей качества методики анализа, таких как линейность, повторяемость (сходимость) и внутрилабораторная прецизионность.
The object of the study was the substance 2-ethylthio-6-nitro-1,2,4-triazolo-[5,1-c]-1,2,4-triazin-7-one sodium salt dihydrate (UPI-802). Objective: quantification of 2-ethylthio-6-nitro-1,2,4-triazolo-[5,1-c]-1,2,4-triazin-7-one sodium salt dihydrate by the method of voltammetry. For UPI-802, the signal of electroreduction of a nitro group is the most useful for quantitative determination. The processes of the nitro group reduction of the test substance in aqueous and aprotic solutions was studied using voltammetry in conditions of physical removal of dissolved oxygen and without oxygen removal. It was established that the rate of reduction of UPI-802 is controlled by diffusion, the processes of reduction of the nitro group is irreversible and proceeds in two stages in a Britton-Robinson buffer solution. The first recovery wave, lying in the potential region of -0,31 - (-0,8) V, corresponds to the addition of 4 electrons. It was found that the electroreduction of the nitro group proceeds with previous protonation. The optimal mode for recording the analytical signal of the UPI-802 on the glassy carbon electrode was selected in conditions of chemical method for removing dissolved oxygen – square-wave with a pulse amplitude of 0,05 V and a pulse frequency of 35 Hz. The possibility of using thick-film carbon-containing electrodes to determine the test substance by the method of square-wave voltammetry was shown. The quality indicators of the analysis technique, such as linearity, repeatability (convergence) and intralaboratory precision, were evaluated.

Dams fragment streams and rivers, with >14,000 in New England alone, and have the potential to significantly alter the physical, chemical, and biological characteristics of lotic systems. For example, dams can alter temperature and dissolved oxygen (DO) regimes, which can, in turn, affect species distributions, whole system metabolism, and nutrient processing rates. Moreover, changes in temperature signal life history cues (e.g., emergence, egg-hatching, migration) for many species of aquatic organisms, and present another avenue for dams to alter biotic communities. Despite the prevalence of small dams in the landscape and their potential significant impacts on temperature and DO, dams have not been well-studied and published impacts vary widely across sites. Given the variation in impact, I sought to quantify the impacts of small dams to stream temperature and DO, and to determine the drivers of inter- and intra-site variation in response. To accomplish this, I deployed 160 continuous temperature data loggers at 30 small, surface-release dams in Massachusetts. The majority of sites (61%) had higher temperatures downstream of the dam compared to upstream and most (85%) experienced decreasing temperatures with increasing distance downstream of the dam, such that the warmest temperatures were located closest to the dam. At approximately half of the temperature sites, flow had a homogenizing effect on temperatures throughout the study reach, whereby impacts were more pronounced (e.g., more warming, faster decay rates) under periods of low flow than under high flow conditions. Magnitude of warming varied greatly among sites, and this variation was explained best by landscape position and reservoir volume, with dams in smaller watersheds and with larger reservoir volumes experiencing greater warming magnitudes. Forest cover, dam height, and the presence of an auxiliary spillway best predicted the downstream temperature decay rate, with temperatures cooling fastest downstream of shorter dams in forested basins that did not have an auxiliary spillway. I used continuous DO loggers upstream, within the impoundment, and downstream of 12 dams to identify dam impacts to DO. Most sites experienced lower DO (66%) within the impoundment compared to upstream; however, 58% of the sites showed no difference in diel ranges between these reaches. The effect of dams on downstream DO was mixed, with increases, no change, and decreases relative to upstream condition; however, the majority of sites (58%) experienced a suppressed downstream diel range relative to upstream. The upstream slope, basin size, and dam height drove the impoundment response, such that dams with steeper upstream reach slopes, located in smaller basins, and with shorter dam heights experienced the greatest decreases in impoundment DO relative to upstream. Differences between downstream and upstream DO were best explained by upstream slope and impoundment volume, whereby sites with steeper upstream reaches and larger volumes of water within the impoundment experienced the largest decreases in downstream DO when compared to upstream reaches. These results may help managers prioritize dam removal at sites where a dam is having larger and more negative (e.g., elevated temperatures, decreased DO) impacts, and therefore where the greatest benefits should occur following restoration.

Bio-based and biodegradable polymers are regarded as potential replacements of traditional fossil based plastics. Polyhydroxyalkanoates (PHAs) are widely studied biopolymers due to their broad range of thermal and mechanical properties. The impacts of operational conditions, such as pH, temperature, organic loading rate and sludge retention time, in PHA production process by mixed microbial cultures (MMCs) have been evaluated by previous studies, but the influence of dissolved oxygen (DO), which is directly related to process energetic demand, was rarely discussed. This thesis is focused on the effects of DO on the microbial culture selection and PHA accumulation stages, as well as the impact of DO on a combined PHA production and nutrient removal process for wastewater treatment. Efficient Plasticicumulans dominating microbial cultures were enriched under both high DO (3.47 ± 1.12 mg/L) and low DO (0.86 ± 0.50 mg/L) conditions in the feast phase containing mostly the same populations but with different relative abundance. Butyrate and valerate were found to be the preferred substrates as compared to acetate and propionate regardless of DO concentrations. Compared to acetate and propionate, the butyrate and valerate uptakes were not significantly impacted by low DO levels in the PHA accumulation stage. A metabolic model was developed for the first time to describe the substrate preference among multiple volatile fatty acids (VFAs), providing a successful approach for PHA composition prediction and process efficiency optimization when four competing VFAs are supplied. Further, DO level control through both the feast and famine phases of culture selection was applied, at 3.79±0.65 mg/L and 0.48±0.29 mg/L respectively. The low DO level in both the feast and famine phases proved to be insufficient for successful MMC enrichment. By characterizing the microbial evolution under the unlimited DO conditions, it was found that Paracoccus was the dominating population (>50%) in the selected cultures, and substrate competition was correlated with the abundance of Plasticicumulans during culture selection. In order to optimize the integrated PHA production and nutrient removal process fed with ammonia-rich feedstocks in full scale implementation, the impact of DO on both processes was investigated. Much higher DO affinity for VFA consumption was observed as compared to nitrification. A DO control strategy was proposed based on the observation that the PHA production was not influenced while nitrogen was removed by simultaneous nitrification and denitrification processes when controlling DO at low levels (e.g. 0.4-0.8 mg/L).

A fuzzy logic controller (FLC) for the dissolved oxygen (DO) concentration of a wastewater bioreactor is presented. The FLC is developed and tested based on simulations using first order plus dead time models obtained from experiments with an actual wastewater bioreactor. The FLC uses feedback of the error in DO concentration and rate of change of the DO concentration and manipulates the stem position of the flow control valves (FCVs) supplying air to the bioreactor. The proposed FLC is tested for robustness across several process models, two of which include proposed worst-case process conditions. The performance of the proposed hand tuned FLC is compared to that of a similarly tuned proportional-integral-derivative controller. The FLC is implemented as a lookup table for speed and ease of deployment. The disturbances present in the experimental step testing data are characterized and used as the basis for disturbing the control loop during controller performance testing. A low-pass filter is then included to subsequently smooth the feedback signal. The nonlinear relationship between the FCV stem position and output flow is modelled and included in the controller performance testing. A genetic algorithm (GA) is developed that manipulates the membership functions of the FLC to yield an optimal controller for the ensemble of process models. The ability of the GA to converge on an optimal FLC is verified through repeated trials. The performance of the GA optimized FLC is observed under realistic process conditions and is benchmarked against a manually optimized PID controller.

碩士
淡江大學
水資源及環境工程學系
84
This study is a experiment for taking nitrogen and phosphorus off from themunicipal wasterwater by "anaerobic- aerobic-anoxic-aerobic activated sludgeprocess". The experimental influent was typical municipal wasterwater with theflow of 60.0 L/hr,and 75% raw wastewater flow into the anaerobic tanks, theothers to the anoxic tanks, and the return sludge are 25%. The main controlfactor is dissolved oxygen concentration in the previous aerobic tanks, todiscuss the influences of different dissolved oxygen c oncentration aboutsimultanneous carbon,nitrogen and phosphorus removal. Because of rainingduring the period of experiment, it caused denitrification effect lower, andremoval efficiencies lower. This study is also discussing the influence aboutraining to the efficiencies and characteristics by nitrogen and phosphorusremoval from water with anaerobic-aerobic-anoxic- aerobic activated sludgeprocess. The conclusion about the influences of simultanneous carbon,nitrogenand phosphorus removal. in aerobic t anks DO=2.5,1.5,1.0 mg/L as follow. 1)Theaverage nitrification rate constant(KN) are 0.717, 0.619, and 0.313mgN/gMLSS/h. The KN in DO= 1.0 mg/L is about 50% in DO= 1.5 mg/L and Do= 2.5mg/L. It's beccuse the higher dissolved oxygen concentration can raise thenitrification rate and it is better for nitrified to multiply. It causedobvious differiences nitrification rate constant in the environment of higheror lower dissolved oxygen concentration. 2)When the average dissolved oxygenconcentration are 0. 5, 0.3, 0.2 and 0.0mg/L, the average denitrification rateconstant(KDN) are 0.258, 0.426, 0.477.and 0.631 mgN/gMLSS/h. The KDN of DO=0.5 in anoxic is about 40.9% in DO= 0.0mg/L. One of the elements to rasise theefficiencies of denitrification is to maintain the absolute anoxic conditionin anoxic tank. 3)During the constant raining period of time,the SBOD/P ofinfluent is between 6~9,and PO43- concentration of effluent is over 3.0 mg/Lin previous aerobic tank. And polyP organisms luxury uptake of p hosphorus isunobserved. It can't get effect of phosphorus removal. When the influentSBOD/P ≧ 12,the effluent PO43- concentration of previous aerobic tank isminor of 1.5 mg/L. And the polyP organisms luxury uptake of phosphorus isobviously. 4)During the unrained period of time, the influent SBOD/NOX-N ofanoxic tank is over 1.42, denitrification rate is over 85%. And during theconstant raining days, the nfluent SBOD/NOX-N of anoxic tank is lower to 1.0,denitrification rate is lower to 46.3~77.3%.It i s said that the higherSBOD/NOX-N will be good to the process of denitrification.

Enhanced biological phosphorus removal (EBPR) is the most economic and sustainable option used in wastewater treatment plants (WWTPs) for phosphorus removal. In this process it is important to control the competition between polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs), since EBPR deterioration or failure can be related with the proliferation of GAOs over PAOs. This thesis is focused on the effect of operational conditions (volatile fatty acid (VFA) composition, dissolved oxygen (DO) concentration and organic carbon loading) on PAO and GAO metabolism. The knowledge about the effect of these operational conditions on EBPR metabolism is very important, since they represent key factors that impact WWTPs performance and sustainability. Substrate competition between the anaerobic uptake of acetate and propionate (the main VFAs present in WWTPs) was shown in this work to be a relevant factor affecting PAO metabolism, and a metabolic model was developed that successfully describes this effect. Interestingly, the aerobic metabolism of PAOs was not affected by different VFA compositions, since the aerobic kinetic parameters for phosphorus uptake, polyhydroxyalkanoates (PHAs) degradation and glycogen production were relatively independent of acetate or propionate concentration. This is very relevant for WWTPs, since it will simplify the calibration procedure for metabolic models, facilitating their use for full-scale systems. The DO concentration and aerobic hydraulic retention time (HRT) affected the PAO-GAO competition, where low DO levels or lower aerobic HRT was more favourable for PAOs than GAOs. Indeed, the oxygen affinity coefficient was significantly higher for GAOs than PAOs, showing that PAOs were far superior at scavenging for the often limited oxygen levels in WWTPs. The operation of WWTPs with low aeration is of high importance for full-scale systems, since it decreases the energetic costs and can potentially improve WWTP sustainability. Extended periods of low organic carbon load, which are the most common conditions that exist in full-scale WWTPs, also had an impact on PAO and GAO activity. GAOs exhibited a substantially higher biomass decay rate as compared to PAOs under these conditions, which revealed a higher survival capacity for PAOs, representing an advantage for PAOs in EBPR processes. This superior survival capacity of PAOs under conditions more closely resembling a full-scale environment was linked with their ability to maintain a residual level of PHA reserves for longer than GAOs, providing them with an effective energy source for aerobic maintenance processes. Overall, this work shows that each of these key operational conditions play an important role in the PAO-GAO competition and should be considered in WWTP models in order to improve EBPR processes.