An approach based on neural networks for estimation and generalization of crossflow filtration processes

The crossflow filtration process differs of the conventional filtration by presenting the circulation flow tangentially to the filtration surface. The conventional mathematical models used to represent the process have some limitations in relation to the identification and generalization of the system behaviour. In this paper, a system based on artificial neural networks is developed to overcome the problems usually found in the conventional mathematical models. More specifically, the developed system uses an artificial neural network that simulates the behaviour of the crossflow filtration process in a robust way. Imprecisions and uncertainties associated with the measurements made on the system are automatically incorporated in the neural approach. Simulation results are presented to justify the validity of the proposed approach. (C) 2007 Elsevier B.V. All rights reserved.

A fuzzy inference system for identification of crossflow filtration processes

The crossflow filtration process differs of the conventional filtration by presenting the circulation flow tangentially to the filtration surface. The conventional mathematical models used to represent the process have some limitations in relation to the identification and generalization of the system behavior. In this paper, a system based on fuzzy logic systems is developed to overcome the problems usually found in the conventional mathematical models. Imprecisions and uncertainties associated with the measurements made on the system are automatically incorporated in the fuzzy approach. Simulation results are presented to justify the validity of the proposed approach.

Applying fuzzy logic systems in the estimation of crossflow filtration processes

The crossflow filtration process differs of the conventional filtration by presenting the circulation flow tangentially to the filtration surface. The conventional mathematical models used to represent the process have some limitations in relation to the identification and generalization of the system behavior. In this paper, a system based on fuzzy logic systems is developed to overcome the problems usually found in the conventional mathematical models. Imprecisions and uncertainties associated with the measurements made on the system are automatically incorporated in the fuzzy approach. Simulation results are presented to justify the validity of the proposed approach.

Identification of Research Portfolio for the Development of Filtration Equipment

This piece of work which is Identification of Research Portfolio for Development of Filtration Equipment aims at presenting a novel approach to identify promising research topics in the field of design and development of filtration equipment and processes. The projected approach consists of identifying technological problems often encountered in filtration processes. The sources of information for the problem retrieval were patent documents and scientific papers that discussed filtration equipments and processes. The problem identification method adopted in this work focussed on the semantic nature of a sentence in order to generate series of subject-action-object structures. This was achieved with software called Knowledgist. List of problems often encountered in filtration processes that have been mentioned in patent documents and scientific papers were generated. These problems were carefully studied and categorized. Suggestions were made on the various classes of these problems that need further investigation in order to propose a research portfolio. The uses and importance of other methods of information retrieval were also highlighted in this work.

Towards integrated operation of membrane bioreactors : effects of aeration on biological and filtration performance

Two experimental studies evaluated the effect of aerobic and membrane aeration changes on sludge properties, biological nutrient removal and filtration processes in a pilot plant membrane bioreactor. The optimal operating conditions were found at an aerobic dissolved oxygen set-point (DO) of 0.5mgO2L-1 and a membrane specific aeration demand (SADm) of 1mh-1, where membrane aeration can be used for nitrification. Under these conditions, a total flow reduction of 42% was achieved (75% energy reduction) without compromising nutrient removal efficiencies, maintaining sludge characteristics and controlled filtration. Below these optimal operating conditions, the nutrient removal efficiency was reduced, increasing 20% for soluble microbial products, 14% for capillarity suction time and reducing a 15% for filterability. Below this DO set-point, fouling increased with a transmembrane pressure 75% higher. SADm below 1mh-1 doubled the values of transmembrane pressure, without recovery after achieving the initial conditions

Pretreatment in membrane filtration of wood hydrolysate

Interest in recovery of valuable components from process streams has increased in recent years. Purpose of biorefinery is to utilize components that otherwise would go to waste. Hemicelluloses, for example, could be utilized in production of many valuable products. One possible way to separate and fractionate hemicelluloses is membrane filtration. In the literature part of this work membrane fouling in filtration processes of pulp and paper process- and wastewaters was investigated. Especially purpose was to find out the possible fouling compounds, after which facilities to remove or modify such components less harmful were studied. In the experimental part different pretreatment methods, mainly to remove or degrade lignin from wood hydrolysate, were studied. In addition, concentration of hemicelluloses and separation from lignin were examined with two ultrafiltration membranes; UFX5 and RC70PP. Changes in feed solution, filtration capacity and fouling of membranes were used to evaluate the effects of pretreatment methods. Changes in hydrolysate composition were observed with different analysis methods. Filtration of hydrolysate proved to be challenging, especially with the UFX5 membrane. The more hydrophilic RC70PP membrane did not seem to be fouled as severely as the UFX5 membrane, according to pure water flux measurements. The UFX5 membrane retained hemicelluloses rather well, but problems arose from rapid flux decline resulting from concentration polarization and fouling of membrane. Most effective pretreatment methods in the case with the UFX5 membrane proved to be prefiltration with the RC70PP membrane, activated carbon adsorption and photocatalytic oxidation using titanium dioxide and UV radiation. An additional experiment with PHW extract showed that pulsed corona discharge treatment degraded lignin quite efficiently and thus improved filtration capacity remarkably, even over six times compared to the filtration with untreated extract.

Hybrid modeling of convective laminar flow in a permeable tube associated with the cross-flow process

The confined flows in tubes with permeable surfaces arc associated to tangential filtration processes (microfiltration or ultrafiltration). The complexity of the phenomena do not allow for the development of exact analytical solutions, however, approximate solutions are of great interest for the calculation of the transmembrane outflow and estimate of the concentration, polarization phenomenon. In the present work, the generalized integral transform technique (GITT) was employed in solving the laminar and permanent flow in permeable tubes of Newtonian and incompressible fluid. The mathematical formulation employed the parabolic differential equation of chemical species conservation (convective-diffusive equation). The velocity profiles for the entrance region flow, which are found in the connective terms of the equation, were assessed by solutions obtained from literature. The velocity at the permeable wall was considered uniform, with the concentration at the tube wall regarded as variable with an axial position. A computational methodology using global error control was applied to determine the concentration in the wall and concentration boundary layer thickness. The results obtained for the local transmembrane flux and the concentration boundary layer thickness were compared against others in literature. (C) 2007 Elsevier B.V. All rights reserved.

Kalvosuodatusprosessin tehostaminen paperiteollisuuden sovelluksissa

Tässä diplomityössä tutkittiin kalvosuodatuksen esikäsittelymenetelmiä ja kalvonpesua. Työn kirjallisuusosassa käsitellään vuon alenemiseen vaikuttavia tekijöitä, esikäsittelymenetelmiä ja kalvonpesua. Kokeellisessa osassa tutkittiin kemiallisten esikäsittelyjen vaikutusta vuon alenemiseen paperitehtaan happaman kiertoveden kirkkaan suodoksen kalvosuodatuksessa. Esikäsittelykemikaalit olivat ympäristöystävällisiä ja paperinvalmistusprosessiin soveltuvia. Lisäksi tutkittiin kalvonpesuaineiden pesutehokkuuksia. Tutkitut esikäsittelyaineet olivat mikrokiteinen kitosaani, karboksimetyyliselluloosa, selluloosa- ja puukuitu sekä kaupallinen antiskalantti. Pesuaineista tutkittiin kolmea kaupallista kalvonpesuainetta, yhtä kalvopesun tehostusainetta sekä peretikkahappoa. Kokeet tehtiin kahdella laboratoriomittakaavaisella kalvosuodattimella. Kalvoina käytettiin kahta nanosuodatus- ja yhtä ultrasuodatuskalvoa. Vuon alenemista tutkittiin suodatuksen aikaisena alenemisena ja vesivuohon verrattavana alenemisena. Esikäsittelyjen vaikutusta erotustehokkuuteen tutkittiin ioni-, johtokyky-, orgaanisen hiilen kokonaispitoisuus-, sokeri-, sameus- ja ligniinireduktioilla. Lisäksi määritettiin kalvon likaantuminen suodatuksen aikana vesivuon määrityksillä ennen ja jälkeen suodatuksen. Pesutehokkuus määritettiin vesivuon määrityksillä suodatuksen jälkeen ja pesun jälkeen. Kitosaani- ja karboksimetyyliselluloosakäsittelyillä oli vuon alenemista estävä vaikutus hydrofiilisellä nanosuodatuskalvolla suodatettaessa. Kitosaanikäsittelyn 5 g/dm3:n ja karboksimetyyliselluloosakäsittelyn 2 g/ dm3:n annostuksella vuot alentuivat suodatuksen aikana 8 %-yksikköä vähemmän kuin ilman esikäsittelyä. Puukuitukäsittely stabiloi 0,1 g/dm3:n annostuksella saman kalvon vuota, kun kiintoainetta ei poistettu syötöstä. Hydrofobisen nanosuodatuskalvon vuon alenemista ehkäisivät puu- ja selluloosakuitukäsittelyt sekä karboksimetyyliselluloosakäsittely. Karboksimetyyliselluloosakäsittely vähensi vuon alenemista 25 %-yksikköä ja puukuitukäsittely 13 %-yksikköä. Hydrofiilisellä ultrasuodatuskalvolla vuon aleneminen oli pientä ilman esikäsittelyä. Reduktioihin esikäsittelyt vaikuttivat parhaiten ultrasuodatuskalvolla. Kitosaanikäsittely nosti 1 g/dm3:n annostuksella alumiinireduktion 50 %:sta 96 %:iin ja 5 g/dm3:n annostuksella rautareduktion 30 %:sta 55 %:iin. Karboksyylimetyyliselluloosakäsittelyt vaikuttivat parantavasti mangaanin, magnesiumin, raudan ja kalsiumin reduktioihin. Optimi karboksyylimetyyliselluloosa-annostus oli 2 g/dm3. Merkittävin reduktion nousu oli kalsiumilla, jonka reduktio nousi esikäsittelyllä 4 %:sta 57 %:iin. Reduktiota nostava mekanismi oli kalvon pinnalle muodostuva sekundaarikerros. Pesuaineista tehokkain oli entsyymiä sisältävä kalvonpesuaine. Suurin vaikutus sillä oli hydrofobisen nanosuodatuskalvon pesussa. Optimiannostuksella (0,5 %) kalvon vesivuo pesun jälkeen oli 114 % pesua edeltäneestä vesivuosta. Muut kaupalliset pesuaneet oli tehokkaita hydrofiilisille kalvoille. Peretikkahappo oli yksittäisenä pesuaineena heikkotehoinen.

Recovery and purification of surfactin from fermentation broth by a two-step ultrafiltration process

Surfactin is a bacterial lipopeptide produced by Bacillus subtilis and it is a powerful surfactant, having also antiviral, antibacterial and antitumor properties. The recovery and purification of surfactin from complex fermentation broths is a major obstacle to its commercialization; therefore, two-step membrane filtration processes were evaluated using centrifugal and stirred cell devices while the mechanisms of separation were investigated by particle size and surface charge measurements. In a first step of ultrafiltration (UF-1), surfactin was retained effectively by membranes at above its critical micelle concentration (CMC); subsequently in UF-2, the retentate micelles were disrupted by addition of 50% (v/v) methanol solution to allow recovery of surfactin in the permeate. Main protein contaminants were effective]), retained by the membrane in UF-2. Ultrafiltration was carried out either using centrifugal devices with 30 and 10 kDa MWCO regenerated cellulose membranes, or a stirred cell device with 10 kDa MWCO polyethersulfone (PES) and regenerated cellulose (RC) membranes. Total rejection of surfactin was consistently observed in UF-1, while in UF-2 PES membranes had the lowest rejection coefficient of 0.08 +/- 0.04. It was found that disruption of surfactin micelles, aggregation of protein contaminants and electrostatic interactions in UF-2 can further improve the selectivity of the membrane based purification technique. (C) 2007 Elsevier B.V. All rights reserved.

Caracterização e biodegradação de lodo de estações de tratamento de água para descarte em aterro sanitário

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da eficiência das ondas de ultra-som em relação ao hipoclorito de sódio e à filtração adsorção na eliminação de microrganismos em estação de tratamento de água

Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC

Reaproveitamento de meio de cultivo de Arthrospira platensis tratado por processos de microfiltração e ultrafiltração

Micro-organismos fotossintetizantes, incluído aqui o gênero Arthrospira, vêm sendo amplamente produzidos em larga escala em vários países, detendo um mercado que gera mais de 1 bilhão de dólares ao ano. A produção industrial utiliza grande volume de água com alta concentração salina para produzir milhares de toneladas de biomassa microalgal. É crescente a utilização de tratamento de águas por processo de separação por membranas, demonstrando ser uma técnica que gera água de ótima qualidade, de instalação compacta e de fácil automação. No presente trabalho, foi avaliada esta tecnologia para o reaproveitamento do meio de cultura em novos cultivos de micro-organismos fotossintetizantes, visando contribuir para a sustentabilidade deste processo produtivo. O efluente do cultivo de Arthrospira platensis oriundo de processo descontínuo em minitanques foi submetido a tratamento por membranas de filtração tangencial, incluindo microfiltração (MF) (porosidades de 0,65 µm e de 0,22 µm) e ultrafiltração (UF) (peso molecular de corte de 5.000 Da), em pressões transmembrana (TMP) de 22,5 a 90 kPa. Os processos de MF levaram a reduções médias de 53,9±1,3 % e 93,1±1,1 % de matéria orgânica natural (NOM) e pigmentos nos meios residuais, respectivamente. Com o uso de processos de UF, cujos meios foram previamente tratados por MF (0,22 µm e 22,5 kPa), as reduções médias de NOM e pigmentos foram de 57,2±0,5 % e 94,0±0,8 %, respectivamente. Os processos de MF com TMP de 22,5 kPa levaram a concentrações celulares máximas (Xm) equivalentes às obtidas com meio novo. O uso de membrana de 0,65 µm e TMP de 22,5 kPa levou a uma perda média de 2,9 %, 22,7 % e 16,4% dos nutrientes carbonato, fosfato e nitrato, respectivamente, mas a correção desses valores aos mesmos do meio padrão levou à obtenção dos mais altos valores de Xm (3586,6±80 mg L-1), produtividade em células (505,0±11,6 mg L-1 d-1) e fator de conversão de nitrogênio em células (29,6±0,7 mg mg-1). O teor protéico da biomassa foi estatisticamente igual ao da biomassa obtida de cultivo com meio padrão novo. Os dados deste trabalho evidenciam que processos de filtração por membrana são promissores para o reuso de meio de micro-organismos fotossintetizantes.

Integration of Membrane Filtration and Photolysis Processes for Drinking Water Treatment

Dissertation presented to obtain the Ph.D degree in Engineering and Technology Sciences, Chemical Engineering.