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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
181

Comparaison des approches systémique, mécanique des fluides numérique et compartimentale pour la modélisation des réacteurs : application à un réacteur canal à boues activées / Comparison between systemic, computational fluids dynamic and compartmental approaches for reactor modelling : application to an activated sludge wastewater treatment channel reactor

Le Moullec, Yann 29 October 2008 (has links)
L'objectif de ce travail est de comparer les approches systémique, mécanique des fluides numérique (MFN) et compartimentale, une approche de modélisation en émergence basée sur l'exploitation quantitative de simulations de MFN pour construire le modèle. Une méthodologie de construction d'un tel modèle à compartiments est explicitée. Ces différentes approches de modélisation ont été appliquées au cas d'un réacteur pilote de traitement des eaux usées à boues activées : un réacteur triphasique (gaz/liquide/flocs), siège de réactions biologiques complexes. Le modèle hydrodynamique MFN a été validé par des mesures de champs de vitesse et de turbulence, réalisées par Vélocimétrie Laser Doppler ainsi que par des mesures de taux de vide réalisées à l'aide d'une sonde optique. L'hydrodynamique globale du réacteur est bien modélisée par un modèle piston à dispersion axiale et la MFN représente bien le comportement du réacteur. Des expériences sur réacteur pilote chargé en biomasse et alimenté par un substrat synthétique à base de Viandox ont été menées. La modélisation des réactions biologiques a été faite par le modèle ASM1 développé par l'IWA. Les modèles systémique et MFN permettent d'estimer l'évolution de la plupart des concentrations dans le réacteur avec moins de 25 % d'erreur. Des différences entre les deux modèles sont néanmoins observées. Il s'avère que le modèle à compartiment donne des résultats très similaires au modèle MFN pour un temps de calcul de 10 à 20 fois moindre. De plus ce modèle est presque aussi facile à manipuler qu'un modèle systémique et permet une meilleure compréhension des phénomènes mis en jeu dans le réacteur qu'avec un modèle MFN / The purpose of this work is the comparison of the systemic, computational fluid dynamics (CFD) and compartmental approaches. This last approach is a new method of model construction based on the quantitative results of a CFD simulation. A methodology to build such a model is described. These three modelisation approaches have been used to model a bench scale activated sludge wastewater treatment reactor : a complex biological tree-phase reactor (gas/liquid/floc). The CFD modelling has been validated with velocity and turbulence fields, obtained with laser doppler velocimétry and with void fraction measurements obtained with an optical probe. The global hydrodynamics of the reactor is well represented by a plug flow model with axial dispersion. This behaviour is well represented by CFD simulation of residence time distribution. Experiments on the bench scale activated sludge reactor fed with a synthetic substrate primarily composed of Viandox have been carried out. Biological reactions have been modelled by the ASM1 model developped by IWA. Evolution of almost all the concentrations along the reactor are simulated with a maximum error of 25 \% with systemic and CFD models. Some differences are highlighted between these two models. The compartmental model gives almost the same results as the CFD model with a calculation time from 10 to 20 times shorter. Moreover this compartment model is as easy to handle as the sytemic model and allows a better understanding of the phenomena which take place in the reactor than the CFD model
182

Fate of Glucocorticoid Receptor Agonists During Water and Wastewater Treatment Processes

Wu, Shimin, Wu, Shimin January 2016 (has links)
In recent years, endocrine disruption of corticosteroid signaling pathways in wildlife and humans by environmental chemicals have attracted increasing attention. The integrated potential of chemicals in the aquatic environment that disrupt corticosteroid actions have been evaluated using in vitro glucocorticoid receptor (GR) mediated bioassays. Exogenous natural and synthetic corticosteroids (CSs), which are widely used in human and animal therapeutic applications, were demonstrated to be the most important GR agonists, that can potentially cause adverse effects, especially on aquatic organisms. To date, only a few studies have investigated the occurrence and behavior of GR agonists in the aquatic environment and their removal in conventional wastewater treatment plants. Furthermore, there are hardly any data reported on the removal of GR agonists by advanced water and wastewater treatment, especially those synthetic CSs with high potency. To further understand the fate of GR agonists in water and wastewater treatment processes, a sensitive and robust LC-MS/MS method was successfully developed for analyzing a wide range of GR agonists in various environmental waters. The occurrence of GR agonists in surface water and groundwater was monitored along the Lower Santa Cruz River (SCR). Several GR agonists were detected, and a trend of degradation was observed downstream the two WWTP outfalls for both surface water and groundwater. The fate of GR agonists in a local wastewater treatment plant (WWTP) was investigated, and up to 14 GR agonists were detected at different stages. Highly potent synthetic CSs, including clobetasol propionate (CBP), fluticasone propionate (FTP), fluocinolone acetonide (FCA), and triamcinolone acetonide (TCA), were poorly removed in WWTP. Negative removal of some CSs was observed in primary treatment, which may due to the deconjugation of CS conjugates. Removal of GR agonists in secondary effluent during various advanced water treatment processes, including UV, ozonation, MF, RO and chlorination, were studied. UV and RO appeared to be the most efficient treatment process for the attenuation of GR agonists, followed by ozone, while chlorination had little effects on GR agonists in water. Bench-scale experiments were then carried out to investigate the removal of GR agonists by ultraviolet based advanced oxidation processes (UV/AOPs), and powder activated carbon (PAC). UV/chlorine and UV/H2O2 were demonstrated to be effective in removal GR agonists in wastewater, and UV photolysis would be the predominant mechanism in UV/AOP processes. Four types of PACs were tested for removing GR agonists in wastewater effluent, and Cabot HDB carbon was suggested, while Calgon PWA carbon was not recommended due to its low removal efficiency.
183

Odor Monitoring at the New Orleans East Bank Wastewater Treatment Plant

Figinsky, Felicia R 13 May 2016 (has links)
Hydrogen Sulfide is a corrosive, odorous, and hazardous gas that can cause issues for wastewater collection systems and treatment plants. When evaluating hydrogen sulfide concentrations it is important to consider the source, odor causing mechanism, and its level of toxicity. In this study, continuous hydrogen sulfide monitoring was performed for 8 locations within the New Orleans East Bank Wastewater Treatment Plant for a span of 5 months. Hot spots within the plant are located and data analysis is performed based on daily and hourly averages of hydrogen sulfide concentrations. The data was configured to show peak hydrogen sulfide concentrations at specific time intervals throughout the day.
184

Sustainable Ambient Air Quality Monitoring System

Aleti, Poojitha 10 August 2016 (has links)
Deterioration of air quality is a growing concern in the world. Air pollution causes serious health problems and also can sometimes result in death. In order to assess air quality, long term and continuous monitoring of pollutant levels in ambient air are needed, such monitoring is often expensive, cumbersome, and resource intensive and so the monitoring programs often fail to succeed. This research focused on designing an ambient air monitoring system by integrating (1) low-cost sensor with a battery, (2) repurposed materials to fabricate all-weather housing for air monitors, and (3) electronics needed to download the data to an on-site secure digital (SD) card, and to push the data wirelessly to the server. This monitoring system was tested at the selected locations in Harvey and Marrero Wastewater treatment plants (WWTPs) by monitoring hydrogen sulfide (H2S) levels. Preliminary analysis was done for few days and also, the results were analyzed.
185

Industrial Wastewater Treatment Using a South African Natural Zeolite, Clinoptilolite

Semosa, Selilo Bethuel 16 November 2006 (has links)
Student Number : 9400913V - MSc (Eng) dissertation - School of Chemical and Metallurgical Engineering - Faculty of Engineering and the Built Environment / Natural zeolites are finding applicability in a broad range of industrial processes. This study assesses the potential applications of a South African natural zeolite, Clinoptilolite, and develops a methodology to quickly screen and assess these applications. Zeolites are known to have ion exchange and adsorption properties. Wastewater treatment has been identified as a potentially important opportunity in South Africa, since South Africa - and particularly Gauteng - is a water scarce region. The wastewater treatment industry in this region can be divided into two main categories of effluent: namely chemicals from coal and the metal recovery and finishing related to the mining industry. The focus of this work was to find a method to screen for potential uses of Clinoptilolite in these industries. The major effluent treatment issue in respect of the effluents from coal-based processes was identified to be the removal of oxygenate organics that are highly soluble in water, such as ethanol and acetone. This problem cannot be solved using vapour-liquid equilibrium based processes due to high energy costs, and liquid-liquid equilibrium based processes inherently introduce new contaminants into the wastewater. We therefore screened the zeolite for application in the removal of soluble organics via adsorption. The zeolite was found to be unsuitable for the adsorption of acetone and ethanol due to the preferential adsorption of water. As a result we tested the potential of the zeolite as a drying agent for ethanol and acetone. It was found that this zeolite could find application in the dehydration of ethanol, but not acetone. In effluent from the mining and metals based industries, heavy metals frequently occur and are usually toxic, such as lead, zinc and nickel. Such contaminated water must be disposed of as toxic waste, and this is very costly. Thus being able to selectively remove these metals allows for the possible recovery and recycling of a potentially valuable metal. If no application can be found for the recovered metal, the loaded zeolite would need to be disposed of as toxic waste, but the volume of this waste is significantly smaller than that of the original effluent due to the concentration effect of ion exchange processes. All of the metals were ion exchanged onto the zeolite successfully. The zeolite exhibited exceptional selectivity for the removal of lead, and reduced the concentration of lead in the water to levels below detection by Atomic Adsorption. The selectivity for the uptake of the metals in decreasing order was lead, zinc and lastly nickel. Therefore, provided the zeolite can be regenerated, it could be used for effluent treatment in mining activities that have traces of lead in the ore body, such as zinc and silver deposits, and in the battery industry. As a result of the work presented in this dissertation, a further project was undertaken to investigate the regeneration of the zeolite. Preliminary findings indicate that although it can be regenerated, the zeolite capacity decreases with each successive regeneration cycle. More work is required on regeneration to improve the lifespan of the zeolite.
186

Análise parasitológica em esgotos tratados utilizados na agricultura / Parasitological analysis in treated sewage used in agriculture

Santos, Jeferson Gaspar dos 25 October 2010 (has links)
A diminuição da disponibilidade de água de boa de qualidade em nível mundial é resultado, entre outros fatores, do consumo elevado exercido pela agricultura irrigada. A fim de minimizar os impactos ocasionados por essa atividade aos recursos hídricos, muitos países demonstram a viabilidade do emprego de efluentes de esgoto tratado na agricultura. Contudo, esta prática oferece riscos à saúde pública através dos organismos patogênicos capazes de sobreviver no esgoto. Entre estes patógenos a OMS destaca os protozoários e os helmintos parasitas do homem, pelo fato de apresentarem maior período de sobrevivência em condições adversas e alto poder de infecção. O presente trabalho tem como objetivo realizar um levantamento qualitativo e quantitativo dos parasitas intestinais de importância sanitária presentes no esgoto afluente, no efluente tratado e no efluente desinfetado de duas estações de tratamento localizadas na cidade de Piracicaba. A ETE Cecap é composta por um sistema australiano com uma lagoa anaeróbia, lagoas facultativas primária e secundária e tratamento por filtração e desinfecção por cloração. A ETE Piracicamirim é constituída por reatores UASB seguidos por lagoa aerada, decantadores secundários de lodo ativado, tratamento por filtro de areia e desinfecção por radiação ultravioleta. Entre maio de 2008 e dezembro de 2009 foram coletas amostras do esgoto bruto e dos efluentes tratado e desinfetado, seguindo as orientações de AYRES e MARA (1996). As técnicas de preparo e análises parasitológicas foram realizadas segundo YANKO (1987) e WHO (1999). A ETE Cecap apresentou uma freqüência de amostras positivas de 40 por cento para o efluente desinfetado, sendo Toxocara sp o parasita mais presente com 46,17 ovos/l. A média de ovos de helmintos para o período de estudo foi 3,78 ovos/l de efluente desinfetado. A ETE Piracicamirim apresentou uma freqüência de 100 por cento para o efluente desinfetado. Ascaris sp foi o parasita mais encontrado nos três pontos de coleta. A média de ovos de helmintos para o período foi de 0,89 ovos/l de efluente desinfetado. A ETE Cecap não apresentou um efluente final propício à utilização na irrigação. Já o efluente proveniente da ETE Piracicamirim atende as recomendações da WHO (2006), para a presença de ovos de helmintos, para utilização na irrigação irrestrita / Decreased availability of good water quality worldwide is a result, among other factors, high consumption exerted by irrigated agriculture. In order to minimize the impacts caused by this activity to water, many countries demonstrate the viability of using treated sewage effluent in agriculture. However, this practice provides a public health risk through the pathogens can survive in sewage. Among these pathogens, WHO stresses the protozoa and helminths of human, because they presented greater period of survival in adverse conditions and high power of infection. This paper aims to evaluate the quality and quantity of intestinal parasites of sanitary importance present in the raw sewage in the treated effluent and disinfected from two treatment plants located in the city of Piracicaba. The sewage treatment plant CECAP comprises an Australian system with an anaerobic pond, facultative ponds primary and secondary treatment by filtration and disinfection by chlorination. The sewage treatment plant Piracicamirim consists of UASB followed by aerated lagoon, activated sludge secondary clarifiers, treatment by sand filter and disinfection by ultraviolet radiation. Between May 2008 and December 2009 were collected and samples of raw sewage effluent treated and disinfected, following the guidelines of AYRES and MARA (1996). The techniques of preparation and analysis were performed according parasitological YANKO (in 1987) and WHO (1999). CECAP showed rates of positive samples of 40 per cent for the effluent disinfected with Toxocara sp parasite more present with 46.17 eggs/l. The mean helminths eggs for the study period was 3.78 eggs/l effluent disinfected. Piracicamirim showed rates of 100 per cent for the effluent disinfected. Ascaris sp was the parasite most commonly found in the three collection sites. The mean helminths eggs for the period was 0.89 eggs/l effluent disinfected. CECAP not produced a final effluent suitable for irrigation use. Already the effluent from the sewage treatment plant Piracicamirim meets the recommendations of WHO (2006), for the presence of helminths eggs for use in unrestricted irrigation
187

Disposição de resíduos gerados em estações de tratamento de água em estações de tratamento de esgoto / Disposal of water treatment plants sludge in wastewater treatment plants

Scalize, Paulo Sergio 08 August 2003 (has links)
O presente trabalho foi realizado em duas fases. Na primeira, foram estimados os efeitos produzidos nos decantadores primários de uma ETE, após receber resíduo da ETA-SC, que utiliza sulfato de alumínio como coagulante. Foram realizados ensaios em colunas de sedimentação, onde os parâmetros SST, SSV, cor, turbidez, DQO, coliformes totais, Escherichia coli e parasitas, pesquisados no sobrenadante, diminuíram com o aumento da quantidade de resíduo adicionado. Com relação aos sedimentos obtidos nas colunas de sedimentação, foi encontrada maior quantidade de ST e menor resistência específica nos lodos provenientes das colunas que receberam os resíduos da ETA-SC. No teste de atividade metanogênica, a concentração molar de metano foi reduzida nos sistemas que receberam resíduo da ETA-SC, influenciando negativamente no desenvolvimento dos microrganismos metanogênicas. As espécies de microrganismos do gênero Methanothrix sp foram inibidas, sendo encontradas em maior número no frasco-reator controle e em menor quantidade a medida que se aumentou a quantidade do resíduo adicionado. Nesta etapa foi constatado que o resíduo da ETA-SC poderá apresentar interferências negativas sobre a digestão anaeróbia do lodo produzido em decantadores primários de uma ETE. Na segunda fase, na estação piloto, composta de lagoa de aeração seguida de lagoa de sedimentação, que recebeu resíduo da ETA-Fonte, que utiliza cloreto férrico como coagulante, foi verificado que tal resíduo melhorou a qualidade do efluente em termos de DQO, DBO, SST, turbidez, cor, amônio, nitrato, NTK e fosfato total. Os parâmetros ST, SDT, cloreto, nitrito, condutividade e pH não apresentaram diferenças significativas. Em relação ao exame microscópico não houve influências negativas no licor misto das lagoas de aeração. O lodo formado nas lagoas de sedimentação piloto apresentou-se em maior quantidade na lagoa que recebeu resíduo da ETA-Fonte. Neste lodo a resistência específica a filtração foi menor em comparação ao lodo da lagoa que não recebeu resíduo da ETA-Fonte. A desidratação deste lodo por centrifugação necessitou menor quantidade de polieletrólito. Baseado neste estudo não foi verificado interferências que possa impedir o lançamento do resíduo da ETA-Fonte na ETE-Araraquara. / This work was carried out in two phases. Effects of disposing the residues from a water treatment plant - ETASC, which uses alum as primary coagulant on the primary settling tanks was evaluated in the first one. Sedimentation tests using column indicated that parameters such as TSS, VSS, colour, turbidity, COD, total coliformes totais, Escherichia coli e parasites in the supernatant decreased with the increase of the amount of the water treatment wastes added to the column. With relation to the sediments produced in the column, it was found great amount of TS and lower specific solids resistance in those generated in the columns where the water treatment plant residues-WTPR were used. Molar concentration of methane was reduced in the tests performed with the sediments produced with water treatment plant residues and thus, altering negatively the development of methanogenic organisms. The growth of species of microorganism of genera Methanothrix sp was inhibited, which were found in great number in the control flask (with out WTPR) and in lower number as it was increased the amount of WTPR added to the column. It was observed that the WTPR generated in the city water treatment plant may interfere in the anaerobic digestion of sludge produced in primary settling tanks of a wastetreatment plant. A continuous pilot plant was operated in the second phase, which consisted of two aerated lagoon each one followed by a settling lagoon. Waste and WTPR from a watter treatment plant which ferric chloride were fed in one of the systems. It was observed that the use of WTPR improved the effluent quality of the settling lagoon evaluated in terms of COD, BOD, TSS, turbidity, color, ammonium, nitrate, TKN and total phosphate. Some parameters, such as TS, TDS, chloride, nitride, conductivity and pH did not present significant differences in both systems. Microscopic examinations indicated that no influence resulted in the aerated lagoon mixed liquor. A higher amount of sludge was formed in the lagoon system which received the WTPR. The specific resistance to filtration of this sludge was lower than that formed in the lagoon system with out WTPR addition. When dewatering both sludges, that one produced with the addition of WTPR required less amount of polymer. It was concluded that the WTPR produced in the water treatment plant of Araraquara may be disposed in the city wastewater treatment plant.
188

Avaliação exergética da geração e uso de biogás no setor sucroenergético. / Exergy assessment of biogas generation and usage in the sugarcane industry.

Nakashima, Rafael Nogueira 11 May 2018 (has links)
O resíduo da primeira destilação do vinho, a vinhaça, destaca-se dentre os demais gerados na produção de etanol de cana-de-açúcar pelo seu grande volume e alta concentração de substâncias orgânicas. O tratamento anaeróbio desse efluente pode melhorar suas características físico-química (e.g. pH e DQO) além de produzir um combustível alternativo ao gás natural, o biogás. No entanto, apesar dos possíveis ganhos energéticos e ambientais, essa tecnologia apresenta dificuldades em se tornar viável no setor sucroenergético. Tendo em vista esse cenário, este trabalho propõe uma nova análise termodinâmica, baseada no método exergético, do potencial da vinhaça e do biogás provindo de seu tratamento. Para isso, modelou-se a digestão anaeróbia da vinhaça por meio do ADM1 (Anaerobic Digestion Model Nº1) e atualizou-se o cálculo da exergia química deste efluente. Assim, os resultados obtidos indicam que o tratamento anaeróbio pode recuperar uma significativa parcela da exergia descartada com a vinhaça (44-52% de 189-1529 kJ/l), dependendo da degradabilidade e concentração do material orgânico, bem como o regime de operação do reator anaeróbio. Nota-se também, que apesar de a digestão anaeróbia ser mais eficiente com maiores tempos de retenção hidráulica, é preferível maximizar o volume de vinhaça tratada em detrimento da qualidade de conversão. Além disso, o desempenho anual da geração de biogás também é afetado pelo seu processo de partida e pela sazonalidade da produção de etanol. Por outro lado, a planta de biogás promove maiores reduções de exergia destruída em comparação com a fertirrigação e a concentração de vinhaça. Possíveis integrações térmicas entre a planta de biogás e a unidade de concentração de vinhaça foram propostas e analisadas, atingindo melhores eficiências exergéticas e reduzidas demandas térmicas. De forma geral, esse estudo demonstra a aplicação do método exergético na valorização de resíduos orgânicos por meio da produção de biogás. / The residue of the first distillation of wine, vinasse, stands outs in the sugarcane ethanol production due to its huge volume and high concentration of organic substances. The anaerobic treatment of this effluent can enhance its physical-chemical characteristics (e. g. pH and COD) in addition to produce an alternative fuel to natural gas, the biogas. However, although there are possible gains in the energy and environmental aspects, this technology presents difficulties to become viable in Brazilian market. Therefore, this work proposes a new thermodynamic analysis, based on the exergy method, of the potential of vinasse and biogas produced in its anaerobic treatment. In order to accomplish this, the anaerobic digestion of vinasse was modeled with ADM1 (Anaerobic Digestion Model Nº1) and the chemical exergy calculation of this effluent was updated. Thus, the results obtained indicate that the anaerobic treatment can recover a significant part of vinasse exergy (44-52% of 189- 1529 kJ/l), depending on the digestible material concentration, as well as the anaerobic reactor operation. It also can be notice that, although anaerobic digestion be more efficient at higher retention times, it is desirable to maximize treated vinasse volume to the detriment of conversion quality. Furthermore, the biogas production yearly performance is also affected by the reactor start-up process and the ethanol production seasonality. On the other hand, the biogas plant promotes higher reductions of exergy destruction in comparison with fertirrigation and vinasse concentration. Possible thermal integrations between the biogas plant and the vinasse concentration plant were proposed and analyzed, reaching better exergy efficiencies and reduced thermal demand. In general, this study demonstrates the exergy method application in organic residues upgrade by biogas production.
189

Preparação, caracterização e aplicação de ânodos de composição nominal Ti/RuyTi(1-y-x)SnxO2 na degradação eletroquímica de clorofenóis / Preparation, characterization and aplication of anodes of nominal composition Ti/RuyTi(1-y-x)SnxO2 in the degradation electrochemical of chlorophenols

Coteiro, Roberta Duarte 07 February 2007 (has links)
Neste trabalho foram preparados eletrodos de óxidos de composição nominal Ti/RuyTi(1-y-x)SnxO2 por decomposição térmica (400 °C) via três rotas diferentes: Método Tradicional empregando-se precursores inorgânicos dissolvidos em Isopropanol (MT/ISO) e em solução de HCl 1:1 (v/v) (MT/HCl) e, Método dos Precursores Poliméricos (MPP). Os recobrimentos de óxidos foram caracterizados por Microscopia Eletrônica de Varredura, análises de Energia Dispersiva de raios X e Difração de Raios X. A caracterização eletroquímica dos eletrodos foi feita por estudos de potencial em circuito aberto, tempo de vida útil e voltametria cíclica na ausência e na presença do poluente selecionado como modelo, o 4-clorofenol. Eletrólises do 4-clorofenol e de seus principais subprodutos foram realizadas em uma célula de fluxo tipo filtro-prensa e monitoradas por análises de Cromatografia Líquida de Alta Eficiência, Carbono Orgânico Total e íons cloreto em solução, além de testes bacteriológicos de toxicidade. Os resultados mostram que o método de preparação influencia na morfologia e na composição dos eletrodos, mas não afeta o tamanho dos cristalitos. Apesar das características distintas, MT/ISO e MPP são adequados para o preparo desses eletrodos pois evitam perdas dos componentes e proporcionam recobrimentos de estabilidade eletroquímica bastante apropriada frente às condições drásticas de eletrólise, viabilizando assim a aplicação destes eletrodos na degradação de poluentes orgânicos. Além disso, todos os eletrodos investigados são muito promissores para a degradação eletroquímica de clorofenóis, pois apresentam excelente atividade para o consumo do 4-clorofenol. Independente da composição e do método de preparação do eletrodo, os subprodutos formados na eletrooxidação de 4-clorofenol são: hidroquinona, benzoquinona, cloro-hidroquinona e 4-clorocatecol, além dos ácidos oxálico, maleico, málico, succínico e malônico. Embora a mineralização completa do poluente não tenha sido atingida, a toxicidade das soluções após o término das eletrólises diminui consideravelmente, visto que tanto o composto orgânico de partida quanto os subprodutos aromáticos formados são degradados com excelente eficiência, sobretudo quando se utilizam ânodos preparados por MT/ISO. / In this work oxides electrodes of nominal composition Ti/RuyTi(1-y-x)SnxO2 were prepared by thermal decomposition (400 °C) by three different routes: Traditional Method using inorganic precursors dissolved in either Isopropanol (MT/ISO) or a solution of HCl 1:1 (v/v) (MT/HCl) and the Polymeric Precursors Method (MPP).Oxides coatings were characterized by Scanning Electron Microscopy, Energy Dispersive X ray analyses and X ray Diffraction. The electrochemical characterization of the electrodes was performed by studies of potential in open circuit, service lifetime, and cyclic voltammetry in the absence and in the presence of the model pollutant 4-chlorophenol. Electrolyses of 4-chlorophenol and its main by-products were accomplished in filter-press flow cell and monitored by High Performance Liquid Chromatography, Total Organic Carbon, and analyses of chloride ions in solution, besides bacteriological toxicity tests. Results show that the preparation method influences the morphology and composition of the electrodes, but it does not affect the crystallite size. In spite of their different characteristics, MT/ISO and MPP are appropriate methods for the preparation of these electrodes because they avoid the loss of components and provide electrochemically stable coatings before the drastic conditions of electrolysis. Therefore, these electrodes can be applied in the degradation of organic pollutants. Furthermore, all the investigated electrodes are very promising for the electrochemical degradation of chlorophenols, because they present excellent activity regarding the consumption of 4-chlorophenol. Independent of the composition and the preparation method of the electrode, the by-products formed in the electrooxidation of 4-chlorophenol are hydroquinone, benzoquinone, chlorohydroquinone, and 4-chlorocatechol, as well as oxalic, maleic, malic, succinic, and malonic acids. Although the complete mineralization of the pollutant has not been reached, the toxicity of the solutions decreases considerably after the end of the electrolyses. This is because both the initial organic compound and the aromatic by-products formed in the electrolyses are degraded with excellent efficiency, especially when the anodes prepared by MT/ISO are employed.
190

Tratamento de efluentes industriais mediante a aplicação de argila organifílica e carvão ativado granular. / Industrial wastewater treatment through the use of granular organoclay and granular activated carbon.

Waelkens, Barbara Elisabeth 16 April 2010 (has links)
A presença do óleo pode trazer graves problemas ambientais quando lançado em corpos dágua. A remoção de óleos e graxas de efluentes industriais, principalmente quando na forma emulsificada ainda é um desafio para o tratamento de efluentes industriais. Argilas quimicamente modificadas com sais quaternários de amônio podem ser uma alternativa para o tratamento de efluentes oleosos por apresentarem características organofílicas, podendo desta forma ser utilizadas como material adsorptivo. O presente trabalho estuda a aplicabilidade de uma argila organofílica granular, seja de forma simples ou em combinação com carvão ativado granular, como meio filtrante para a remoção de óleos e graxas de dois efluentes industriais reais oriundos de uma indústria de laminação a frio e uma indústria automobilística. Ambos os efluentes apresentam concentrações baixas de óleos e graxas, variando entre 5 e 30 mg/l de óleos e graxas, entretanto, estes valores não estão sempre em concordância com a legislação vigente. A análise gravimétrica de óleos e graxas não forneceu dados confiáveis, entretanto, foi possível observar uma redução da concentração de carbono orgânico total (COT) após o tratamento com a argila organofílica granular. A redução da concentração de COT foi ainda maior após o tratamento do efluente com a composição Argila Organofílica Granular seguida de Carvão Ativado Granular. Tal composição é a mais recomendada, pois garante bons resultados, além de aumentar a vida útil do carvão ativado. / The presence of oil in rivers, lakes and oceans can cause serious environmental hazards. The removal of oil and grease from industrial effluents, especially in its emulsified form, is still a challenge for the industrial wastewater treatment sector. Clays chemically modified with quarternary ammonium salts can be an alternative for the treatment of oily wastewater. Given its organophilic characteristics these organoclays can be used as adsorptive media. The present study evaluates the applicability of a granular organoclay, be it in its simple form, or combined with activated granular charcoal, as a filtration medium for the oil and grease removal of two industrial effluents. Both effluents, one of a cold lamination industry and one of an automotive industry, have low oil and grease concentrations, between 5 and 30 mg/L, however these concentrations do not always comply with local directives. The data obtained by the gravimetric Oil and Grease analysis were not reliable, however it was possible to observe a reduction in the Total Organic Carbon (TOC) concentration of the effluent treated with the granular organoclay. It was also observed that the TOC concentration of the effluent was even larger when the effluent was treated with the composition, granular organoclay (GOC) followed by granular active charcoal (GAC). Thus, the composition GOC followed by GAC is the most recomended, for it garantees reliable results and enhances the GAC lifespan.

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