La technique d’échantillonnage passif DGT (« Diffusive Gradients in Thin Films ») possède de nombreux avantages (intégration des variations temporelles, abaissement des limites de quantification) qui font d’elle une méthode prometteuse pour une utilisation en réseaux de mesure pour quantifier les éléments traces dans les eaux naturelles. Cependant, il existe encore des zones d’ombre qui constituent des freins à son utilisation dans un contexte réglementaire. Ce travail a donc pour objectif d’identifier des biais potentiels et ainsi contribuer à fiabiliser la méthode. Cette étude montre que l’obtention d’un résultat avec une incertitude minimisée doit passer par la détermination expérimentale des facteurs d’élution ; cependant, l’utilisation d’une valeur standard de 0,8 pour le Cr(III) et de 0,85 pour Al(III), Cd(II), Co(II), Cu(II), Ni(II), Pb(II) et Zn(II) est proposée afin d’alléger les manipulations tout en conservant une incertitude raisonnable (<10%). L’étude de l’influence de l’encrassement des dispositifs DGT a montré que la sorption des cations Cd(II), Cu(II) et Pb(II) sur les filtres encrassés affectent respectivement peu, modérément et fortement leur accumulation dans les échantillonneurs et donc leur quantification. Des durées d’exposition de moins d’une semaine sont alors préconisées pour ces éléments. En revanche, l’encrassement a eu un impact négligeable sur le Ni(II) et sur les oxyanions As(V), Cr(VI), Sb(V) et Se(VI). Enfin, une méthode de quantification simultanée du Cr(III), essentiel à la vie, et du Cr(VI), toxique, a été développée en vue d’améliorer l’évaluation de la toxicité d’une eau. Un unique échantillonneur DGT fixe les deux formes tandis qu’elles sont ensuite sélectivement séparées par une étape d’élution. Cette méthode est robuste sur une large gamme de forces ioniques et de concentrations en sulfate mais sur une gamme de pH plus restreinte ne couvrant pas toutes les eaux naturelles (4 à 6). / The passive sampling DGT technique (Diffusive Gradients in Thin Films) has a lot of benefits (time-weighted average concentrations, low limits of quantification) and would therefore be a useful tool for monitoring studies to quantify trace elements in natural water. However, there are still some limitations and grey areas that put the brakes on the development of the method for regulatory applications. The aim of this work is to identify potential biases and contribute to increase the method reliability. This study shows that a minimized uncertainty on results can be obtained only if elution factors are experimentally determined; however, standard values of 0.8 for Cr(III) and 0.85 for Al(III), Cd(II), Co(II), Cu(II), Ni(II), Pb(II) and Zn(II) are suggested to reduce manipulations while keeping reasonable uncertainty (<10%). Studying the influence of fouling developed on DGT devices showed that the sorption of cations Cd(II), Cu(II) and Pb(II) had, respectively, a slight, moderate and strong impact on their accumulation in DGT samplers and therefore on their quantification. Samplers should then be deployed for less than one week. In contrast, fouling had a negligible impact on oxyanions As(V), Cr(VI), Sb(V) and Se(VI). Finally, a method was developed to simultaneously quantify both Cr oxidation states naturally occurring in natural waters, which are Cr(III), essential to life, and Cr(VI), toxic. Both forms are accumulated in a single DGT sampler before being selectively separated during an elution step. This method is robust for wide ranges of ionic strengths and sulfate concentrations but for a narrower range of pH (4 to 6).

Abstract Heat exchangers are used in industrial processes to transfer energy from one source to another. Heat exchangers improve the energy efficiency of processes and therefore increase the profitability and decrease the environmental impact of production. Effectiveness of heat exchangers may be diminished by fouling, in which unwanted material deposits on the heat transfer surface reducing the heat transfer and increasing the pressure drop of the system. Due to fouling, the energy demand, and the operation and maintenance costs of industrial processes increase significantly. In addition, fouling causes considerable environmental effects due to the increased energy demand and the use of additives and cleaning chemicals. In this thesis, the crystallization fouling of calcium carbonate on heat transfer surfaces was studied using experimental and modeling methods with the aim to reduce fouling by increasing the understanding of the crystallization fouling phenomenon and providing a validated model for studying crystallization fouling on heat transfer surfaces. The fouling experiments were conducted in a laboratory scale set-up to study the crystallization fouling mechanism under controlled conditions. Based on the knowledge and data gained from the experiments, a crystallization fouling model was developed, and validated in various conditions. As a result, the most important parameters affecting crystallization fouling were identified, and the governing sub-processes were determined. The developed model was used to optimize the surface temperature of a heat exchanger to provide the maximum heat transfer rate when the heat exchanger is subject to fouling at various cleaning intervals. In addition, the used methods were applied in the study of the abatement of fouling by surface modifications. Based on the results, the studied crystallization process is governed by the surface integration sub-process. In addition, the residence time of the fluid at the wall affects the mass deposition. The results showed that the surface temperature and the shear stress are the most important parameters affecting fouling in the studied conditions, and therefore, they should be defined accurately. For this purpose, CFD was found to provide a useful tool. The developed models were found to predict reliably the experimental conditions. Therefore, the thesis shows that the developed model facilitates the design of heat exchangers, but also assists in minimizing the fouling of heat exchangers. / Tiivistelmä Lämmönvaihtimia käytetään teollisissa prosesseissa siirtämään energiaa kohteesta toiseen. Lämmönvaihtimet parantavat prosessien energiatehokuutta ja siten lisäävät tuotannon kannattavuutta ja vähentävät ympäristövaikutuksia. Lämmönvaihdinten energiatehokkuutta heikentää kuitenkin likaantuminen, jossa lämmönsiirtopinnalle muodostuu kerrostuma, joka heikentää lämmönsiirtoa ja aiheuttaa virtausvastusta. Likaantuminen lisää lämmönvaihdinten energiankulutusta ja käyttökustannuksia sekä aiheuttaa merkittäviä ympäristöpäästöjä kasvaneen energiantarpeen sekä lisä- ja puhdistusaineiden käytön vuoksi. Tässä työssä tutkittiin kalsium karbonaatin aiheuttamaa lämmönsiirtopintojen kiteytyvää likaantumista käyttäen sekä kokeellisia että mallinnusmenetelmiä. Työn tavoitteena oli lisätä tietoa kiteytyvästä likaantumisesta sekä kehittää validoitu laskentamalli, jolla voidaan tutkia lämmönsiirtopintojen kiteytyvää likaantumista. Likaantumiskokeet tehtiin laboratoriomittakaavan koelaitteessa, jolla voidaan tutkia likaantumismekanismia hallituissa olosuhteissa. Kokeista saadun tiedon ja aineiston perusteella kehitettiin kiteytyvää likaantumista kuvaava malli, joka validoitiin eri olosuhteissa. Tulosten perusteella identifioitiin tärkeimmät kiteytyvään likaantumiseen vaikuttavat parametrit sekä määritettiin rajoittavat osa-prosessit. Kehitettyä mallia käytettiin lämmönsiirtoprosessin optimoinnissa. Lisäksi käytettyjä metodeja sovellettiin tutkimukseen, jossa likaantumista pyrittiin vähentämään pintamodifikaatioiden avulla. Tulosten perusteella tutkittu kiteytymisprosessi on pinta-integraation rajoittama. Lisäksi havaittiin, että fluidin viipymäaika lämmönsiirtopinnalla vaikuttaa likaantumisnopeuteen. Tulokset osoittivat, että pintalämpötila ja leikkausjännitys ovat tärkeimmät kiteytyvään likaantumiseen vaikuttavat tekijät tutkituissa olosuhteissa. Näin ollen niiden tarkka määrittely on erittäin tärkeää likaantumisnopeuden mallintamiseksi luotettavasti. Virtauslaskenta (CFD) osoittautui hyödylliseksi työkaluksi näiden parametrien määrittämisessä. Tulosten perusteella kehitetty malli ennustaa luotettavasti kokeellisia olosuhteita. Näin ollen tämä työ osoittaa, että kehitettyä mallia voidaan käyttää apuna paitsi lämmönvaihtimien suunnittelussa myös lämmönsiirtopintojen kiteytyvän likaantumisen vähentämisessä.

A study on high-viscosity oil-water flow in horizontal pipes has been conducted applying experimental, mechanism analysis and empirical modelling, and CFD simulation approaches. A horizontal 1 inch flow loop was modified by adding a designed sampling section to achieve water holdup measurement. Experiments on high-viscosity oil-water flow were conducted. Apart from the data obtained in the present experiments, raw data from previous experiments conducted in the same research group was collated. From the experimental investigation, it is found that that the relationship between the water holdup of water-lubricated flow and input water volume fraction is closely related to the oil core concentricity and oil fouling on the pipe wall. The water holdup is higher than the input water volume fraction only when the oil core is about concentric. The pressure gradient of water-lubricated flow can be one to two orders of magnitude higher than that of single water flow. This increased frictional loss is closely related to oil fouling on the pipe wall. Mechanism analysis and empirical modelling of oil-water flow were conducted. The ratio of the gravitational force to viscous force was proposed to characterise liquid-liquid flows in horizontal pipes into gravitational force dominant, viscous force dominant and gravitational force and viscous force comparable flow featured with different basic flow regimes. For viscous force dominant flow, an empirical criterion on the formation of stable water-lubricated flow was proposed. Existing empirical and mechanistic models for the prediction of water holdup and/or pressure gradient were evaluated with the experimental data; the applicability of different models is demonstrated. Three-dimensional CFD modelling of oil-water flow was performed using the commercial CFD code Fluent. The phase configurations calculated from the CFD model show a fair agreement with those from experiments and mechanism analysis. The velocity distribution of core annular flow is characterised with nearly constant velocity across the oil core when the oil viscosity is significantly higher than the water viscosity, indicating that the high-viscosity oil core flows inside the water as a solid body. The velocity profile becomes similar to that of single phase flow as the oil viscosity becomes close to the water viscosity.

Maintenance of membrane performance requires inevitable cleaning or defouling of fouled membranes. Membrane cleaning using enzymes such as proteases, lipases, α-glucosidases from a sulphidogenic bioreactor was investigated. At first, dilute and concentrated enzyme extract were prepared form the sulphidogenic pellet. Enzyme assays on 0.5 % azocaisen, 1 % triacetin and 1 mg/ml ρ-nitrophenyl-α-D-glucopyranoside were performed using the concentrated enzyme extract (0 – 200 mg/ml). For membrane fouling, an abattoir effluent was obtained from Ostritech Pty (Ltd), Grahamstown, South Africa. The effluent was characterised for presence of potential foulants such as lipids, proteins, amino acids and carbohydrates. Static fouling of polysulphone membranes (0.22 μm, 47 mm) was then performed using the abattoir effluent. Cleaning of the fouled membranes was also performed using at first the dilute and then the concentrated form (200 mg/ml) of enzyme extracts. Qualitative and quantitative biochemical analysis for proteins, lipids and carbohydrates was performed to ascertain the presence of foulants on polysulphone membranes and their removal by dilute or concentrated enzyme extracts. The ability of dilute enzyme extracts to remove proteins lipids, and carbohydrates fouling capillary UF membrane module; their ability to restore permeate fluxes and transmembrane pressure after cleaning/defouling was also investigated. Permeate volumes from this UF membrane module were analysed for protein, amino acids, lipids, and carbohydrates concentrations after fouling and defouling. Fouling was further characterized by standard blocking, cake filtration and pore blocking models using stirred UF cell and polyethersulphone membranes with MWCO of 30 000, 100 000 and 300 000. After characterization of fouling, polyethersulphone membranes with MWCO of 30 000 and 300 000 were defouled using the concentrated enzyme extract (100 mg ml). Enzyme activities at 200 mg/ml of enzyme concentration were 8.071 IU, 86.71 IU and 789.02 IU for proteases, lipases and α-glucosidases. The abattoir effluent contained 553 μg/ml of lipid, 301 μg/ml of protein, 141 μg/ml of total carbohydrate, and 0.63 μg/ml of total reducing sugars. Proteins, lipids and carbohydrates fouling polysulphone membranes after a day were removed by 23.4 %, when a dilute enzyme was used. A concentrated enzyme extract of 200 mg/ml was able to remove proteins, lipids and carbohydrates up to 5 days of fouling by 100 %, 82 %, 71 %, 68 % and 76 % respectively. Defouling of dynamically fouled capillary ultrafiltration membranes using sulphidogenic proteases was successful at pH 10, 37°C, within 1 hour. Sulphidogenic proteases activity was 2.1 U/ml and flux Recovery (FR %) was 64. Characterization of fouling revealed that proteins and lipids were major foulants while low concentration of carbohydrates fouled polyethersulphone membranes. Fouling followed standard blocking for 10 minutes in all the membranes; afterwards fouling adopted cake filtration model for membranes with 30 000 MWCO and pore blocking model for membranes with 300 000 MWCO. A concentration of 100 mg/ml of enzyme extract was able to remove fouling from membranes with MWCO of 30 000. Defouling membranes that followed pore blocking model i.e. 300 000 MWCO was not successful due to a mass transfer problem. From the results of defouling of 30 000 and 300 000 MWCO it was concluded that defouling of cake layer fouling (30 000 MWCO) was successful while defouling of pore blocking fouling was unsuccessful due to a mass transfer problem. The ratio of enzymes present in the enzyme extract when calculated based on enzymatic activity for proteases, lipases and α-glucosidases was 1.1 %, 11 % and 87.9 %. It was hypothesized that apart from proteases, lipases, α and β-glucosidases; phosphatases, sulphatases, amonipeptidases etc. from a sulphidogenic bioreactor clean or defoul cake layer fouling by organic foulants and pore blocking fouling provided the mass transfer problem is solved. However, concentration of enzymes from a sulphidogenic bioreactor has not been optimized yet. Other methods of concentrating the enzyme extract can be investigated for example use of organic solvents.

Water is a scarce and unevenly distributed national resource and it is, therefore, important to reduce water consumption in paper mills. Closure of water systems for reuse, however, directly and indirectly results in an increase in the numbers and types of microorganisms resulting in poor runnability, lower production rates and increased safety hazards. The aim of this study was to investigate the microbiology of paper-mill water systems in South Africa to aid in closure of water systems whilst controlling microbial fouling. Different environmental parameters monitored at paper mills were reviewed together with microbial enumeration techniques employed by industry and characterisation and identification methods to study bacteria. Various environmental and process parameters could play an important role in the number and type of microorganisms in a paper-mill water system. The highest correlation between an environmental parameter and biological activity was found for oxidation-reduction potential and the numbers of culturable aerobic bacteria. Other environmental parameters that significantly influenced microbial numbers were temperature, dissolved oxygen, dissolved solids, chemical oxygen demand, nitrogen, phosphorous, specific water consumption, pulp furnish, biocide class and retention time. The characterisation and identification of problematic bacteria in paper mills could enable better control since the correct biocides could be applied to minimise microbiologically associated problems. Prevalent bacteria that were isolated from the water systems of 14 paper machines were typed into 35 distinct groups using ERIC-PCR and PCR-RFLP and identified with sequence analysis. Eleven of the 35 types were identified to species level, 20 types were identified to genus level and the remaining four types were identified to family level. It was found that the majority of bacteria belonged to the genera Acinetobacter and Pseudomonas that contain well-known slime-forming bacterial species. Traditional methods employed to investigate bacteria in industrial water systems often do not accurately represent the composition and diversity of bacterial communities. DGGE analysis could provide a powerful tool for monitoring bacterial diversity, since it is able to discriminate between identical sizes of PCR-amplified DNA fragments that differ in their sequence content. The use of DGGE to monitor changes in microbial populations could improve control of microbial fouling, but more analyses would be needed to validate the results of the present study. / Dissertation (MSc (Microbiology))--University of Pretoria, 2008. / Microbiology and Plant Pathology / unrestricted

Orientadores: Francisco Maugeri Filho, Andrea Limoeiro Carvalho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-22T11:19:31Z (GMT). No. of bitstreams: 1 Michelon_Mariano_M.pdf: 21190388 bytes, checksum: 346134051a71b6148d3357e82826c8b8 (MD5) Previous issue date: 2013 / Resumo: Galacto-oligossacarídeos (GOS) são oligossacarídeos não digeríveis que apresentam propriedades prebióticas, pois auxiliam na proliferação de bifidobactérias no cólon. Os GOS podem ser obtidos pela reação de transgalactosilação da galactose catalisada pela enzima ?-galactosidase a partir de substratos ricos em lactose. Neste processo, as misturas de açúcares obtidas após a síntese contêm além dos GOS, mono- e dissacarídeos residuais. Portanto, uma alternativa interessante para aumentar a participação dos GOS no mercado de alimentos funcionais e também incrementar seu valor comercial é sua separação dos demais açúcares. Para tal finalidade, os processos de separação por membranas de nanofiltração podem ser empregados. Estes apresentam vantagens em relação aos processos cromatográficos como a economia de energia e a simplicidade de operação e de ampliação de escala. Deste modo, o objetivo deste trabalho foi desenvolver uma metodologia para purificação de GOS utilizando membranas de nanofiltração. A partir de uma solução modelo contendo GOS, lactose, glicose e galactose, as membranas de nanofiltração NP010 e NP030 constituídas de polietersulfonas com massa molecular de corte de 1000 e 400 Da, respectivamente, e as membranas Desal 5-DK, Desal 5-DL e Desal 5-HL ambas constituídas de poliamidas aromáticas com massa molecular de corte de 150-300 Da foram utilizadas em um sistema de escala laboratorial que simula um processo de filtração tangencial na pressão de 3 MPa a 30°C. A membrana NP030 foi selecionada, pois apresentou nestas condições o maior fator de purificação (FP) de 1,68±0,06, diferindo-se estatisticamente das demais membranas testadas. Após a etapa de seleção, foi conduzido um delineamento composto 22, com faces centradas e tréplicas nos pontos centrais, totalizando 11 ensaios, variando a pressão de operação do sistema (2 a 4 MPa) e a temperatura do processo (15 a 55°C). A pressão de 3 MPa e a temperatura de 35°C resultaram nos maiores valores de FP (>1,77). Em seguida, um processo de diafiltração descontínua foi realizado com a finalidade de aumentar a pureza da solução retida e verificou-se que após a 1º etapa de diafiltração o valor de FP (~1,87) manteve-se constante até o 4º ciclo de diafiltração. As análises das micrografias obtidas através de microscopia eletrônica de varredura (MEV) mostram que a membrana NP030 apresenta deposições de solutos e adesão de micro-organismos na superfície filtrante após sua utilização e lavagem com água, indicando a necessidade de um controle das incrustações e do biofouling para sua reutilização. As micrografias obtidas através de MEV do suporte da membrana indicaram uma possível compactação física. Como etapa subsequente, foi realizada uma validação industrial do processo, utilizando uma unidade piloto de filtração de fluxo tangencial com um módulo espiral da membrana NP030. Foi possível observar que a solução final retida apresentou após 3900 s um valor de FP de 2,55 e uma recuperação de GOS de 97,82%. Foi possível identificar os mecanismos de incrustações dos poros através dos valores dos coeficientes cinéticos de adsorção e pode-se concluir que as incrustações da galactose e da glicose correspondem a um modelo padrão de bloqueio dos poros, enquanto que para os GOS e a lactose a um modelo de bloqueio parcial. Foi estimado o tamanho médio dos poros de permeção da membrana NP030, sendo possível afimar que a probabilidade dos poros de permeação da membrana estarem contidos no intervalo entre 1,94-3,47 nm é de 68,2%. Com estes resultados, pode-se afirmar que as membranas de nanofiltração podem ser utilizadas como uma etapa inicial na purificação dos GOS obtidos através de síntese enzimática. Para obtenção de uma solução com pureza comercial, outras técnicas de purificação deveram ser aplicadas após a nanofiltração / Abstract: Galactooligosaccharides (GOS) are oligosaccharides that present non-digestible prebiotic properties because they assist in the proliferation of bifidobacteria in the human colon. GOS may be obtained by the transgalactosylation reaction of galactose catalyzed by the ?- galactosidase enzyme from substrates rich in lactose. In this process the mixtures of sugars obtained after synthesis contain not only GOS, but also mono-and disaccharide residues. Thus, an interesting alternative to increase the participation of GOS in the functional foods market and also enhance its commercial value is its separation from other sugars. For this purpose, separation processes utilizing nanofiltration membranes may be employed. These processes have advantages over chromatographic processes including energy saving and simplicity of operation and scale increase. The objective of this study was therefore to develop a methodology for purification of GOS using nanofiltration membranes. From a solution containing GOS, lactose, glucose and galactose, the nanofiltration membranes NP010 and NP030, composed of polyethersulfones with molecular weight cut-offs of 1000 Da and 400, respectively, as well as the membranes Desal 5-DK, Desal 5-DL and Desal 5-HL made of aromatic polyamides with molecular mass cut-offs of 150-300 Da were used in a system that simulates a laboratory scale cross-flow filtration process at a pressure of 3 MPa at 30°C. The NP030 membrane was selected because at these conditions it presented the highest purification factor (PF) of 1.68±0.06, statistically different from the other membranes tested. After the selection step, a compound 22 design was conducted with centered faces and triplicate of the central points, totaling 11 assays, varying the operating pressure of the system (2 to 4 MPa) and the process temperature (15 to 55°C). The pressure of 3 MPa and temperature of 35°C resulted in the highest PF values (>1.77). Then a discontinuous diafiltration process was carried out in order to increase the purity of the retained solution, where it was found that after the 1st diafiltration step the PF (~1.87) remained constant until the 4th diafiltration step. Analyses of the micrographs obtained by scanning electron microscopy (SEM) showed that membrane NP030 presents deposits of solutes and adhesion of microorganisms on the filter surface after use and washing with water, indicating the need for control of fouling and biofouling for reuse. The SEM micrographs of the membrane support indicated a possible physical compaction. In a subsequent step, an industrial validation of the process was performed using a pilot tangential flow filtration unit with a model NP030 spiral membrane. It was observed that the final solution retained after 3900 s presented a PF value of 2.55 and a recovery of 97.82% GOS. It was possible to identify the fouling mechanisms of the pores using values of the kinetic adsorption coefficients and it could be concluded that galactose and glucose fouling corresponded to a standard blocking model of the pores, while for lactose and GOS a partial blocking model. The average pore size of the NP030 membrane was estimated, thus it was possible to affirm the probability of the membrane permeation pores in the interval between 1.94-3.47 nm, which was 68.2%. Based on these results, nanofiltration membranes may be used as an initial step in purification of GOS obtained by enzymatic synthesis. To obtain a solution with commercial purity, other purification techniques should be applied after nanofiltration / Mestrado / Engenharia de Alimentos / Mestre em Engenharia de Alimentos

The present Doctoral Thesis makes the first study on the growth of epibionts in the nets of marine farms of the Western Mediterranean. Also, this Doctoral Thesis is a novel contribution in the field of marine biofouling by collecting information not only taxonomically but also the ecology of the actors and factors involved. The objective of this study is to know the most common epibionts in Mediterranean marine aquaculture nets and their relationship with depth, season, situation on the farm and the response of the epibionts to the presence of a commercial antifouling paint with Based on cuprous oxide, performing for this purpose an exhaustive statistical analysis. To this end, 192 polyethylene sheets of 400 cm2 were placed on a Spanish southeast sea farm, specifically in the municipality of Villajoyosa (Alicante), at two different depths, with different orientations and antifouling paint and without it. The plates were collected in four periods of the year: in early spring, early summer, early autumn and the last, after 1 year submerged. Macroscopic species were studied at the taxonomic level and the data were treated with the Stathgraphics Centurion XVI.II and Promov software 15,02 to perform the relevant statistical studies. Nothing has been written before this work on the impact of these paintings on the colonies of the epibionts studied in this thesis, although it has been verified with this thesis that antifouling painting is an effective technique for the fight against marine epibiontes, And that works in addition to any depth and with any orientation. Also, it has been corroborated that the plates were covered more of organisms ,according to the time of exposure in the sea, It had or not antifouling painting,The chronological order of invasion of the plates by the epibionts has also been verified. In addition, the sheets that were located in the discharge area of the fish facility and under the current, were plates populated with a greater number of epibionts, regardless of the depth, orientation or presence of the antifouling paint. / La presente Tesis Doctoral realiza el primer estudio acerca de los crecimientos de epibiontes en las redes de granjas marinas del Mediterráneo Occidental. Asimismo, esta Tesis Doctoral supone una aportación novedosa en el campo del biofouling marino al recoger información no sólo de manera taxonómica sino también de ecología de los actores y factores participantes. Es objeto de este estudio el conocer los epibiontes más comunes en las redes de acuicultura marina mediterránea y su relación con la profundidad, la estación del año, la situación en la granja y la respuesta de los epibiontes ante la presencia de una pintura antifouling comercial con base en óxido cuproso, realizando para ello un exhaustivo análisis estadístico. Con dicho objetivo, se dispusieron 192 placas de polietileno de 400 cm2 en una granja marina del sudeste español, en concreto en el municipio de Villajoyosa (Alicante), a dos diferentes profundidades, con diferentes orientaciones y con pintura antifouling y sin ella. Las placas se recogieron en cuatro periodos del año: a principios de primavera, a principios de verano, a principios de otoño y las últimas, después de 1 año sumergidas. Se estudiaron a nivel taxonómico las especies macroscópicas y se trataron los datos con el software Stathgraphics Centurion XVI.II y ProMV 15.02 para realizar los estudios estadísticos pertinentes. No se ha escrito nada antes de este trabajo sobre el impacto de éstas pinturas en las colonizaciones de los epibiontes estudiados, si bien se ha comprobado con esta Tesis que la pintura antifouling es un técnica efectiva para la lucha contra los epibiontes marinos, y que funciona además a cualquier profundidad y con cualquier orientación. Asimismo, se ha corroborado que las placas se cubrían más con organismos conforme transcurría el tiempo de exposición en el mar, tuvieran o no pintura antifouling y sin que ninguna especie llegara a colonizar y desplazar a las especies previas. Se ha podido constatar también el orden cronológico de invasión de las placas por los epibiontes. Además, las placas que se localizaban en la zona de descarga del vertido de la instalación piscícola y estaban a sotacorriente fueron placas pobladas con mayor número de epibiontes, independientemente de la profundidad, orientación o presencia o no de la pintura antifouling. / La present tesi doctoral realitza el primer estudi sobre els creixements de epibionts a les xarxes de granges marines de la Mediterrània Occidental. Així mateix, aquesta tesi doctoral suposa una aportació innovadora en el camp del biofouling marí en recollir informació no només de manera taxonòmica sinó també d'ecologia dels actors i factors participants. És objecte d'aquest estudi el conèixer els epibionts més comuns en les xarxes d'aqüicultura marina mediterrània i la seva relació amb la profunditat, l'estació de l'any, la situació a la granja i la resposta dels epibionts davant la presència d'una pintura antifouling comercial amb base en òxid cuprós, realitzant per a això una exhaustiva anàlisi estadística. Amb aquest objectiu, es van disposar 192 plaques de polietilè de 400 cm2 en una granja marina del sud-est espanyol, en concret al municipi de la Vila Joiosa (Alacant), a dues diferents profunditats, amb diferents orientacions, i amb I sense pintura antifouling . Les plaques es van recollir en quatre períodes de l'any: a principis de primavera, a principis d'estiu, a principis de tardor i les últimes, després d'1 any submergides. Es van estudiar a nivell taxonòmic les espècies macroscòpiques i es van tractar les dades amb els programes Stathgraphics Centurion XVI.II i ProMV 15.02 per realitzar els estudis estadístics pertinents. No s'ha escrit res abans d'aquest treball sobre l'impacte d'aquestes pintures en les colonitzacions dels epibionts estudiats , si bé s'ha comprovat en aquesta Tesi que la pintura antifouling és un tècnica efectiva per la lluita contra els epibionts marins, i que funciona a més a qualsevol profunditat i amb qualsevol orientació. Així mateix, s'ha corroborat que les plaques es cobrien amb més organismes a mesura que transcorria el temps d'exposició al mar, tinguessin o no pintura antifouling, i sense que cap espècie arribés a colonitzar i desplaçar a les espècies prèvies. S'ha pogut constatar també l'ordre cronològic d'invasió de les plaques pels epibionts. A més, les plaques que es localitzaven a la zona de descàrrega de l'abocament de la instal·lació piscícola i estaven a sotacorrent van ser plaques poblades amb major nombre d¿epibionts, independentment de la profunditat, orientació o presència o no de la pintura antifouling. / Meseguer Hernández, E. (2017). ESTUDIO DEL BIOFOULING ASOCIADO A CULTIVOS MARINOS "OFFSHORE" EN EL MEDITERRÁNEO ESPAÑOL [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/85679 / TESIS

In this Doctoral Thesis the study of the influence of the operating parameters of the activated sludge process on the physical and chemical characteristics of the mixed liquor, from different membrane bioreactors (MBR), has been carried out. In addition, an optical characterization of the mixing liquor has been performed. In order to achieve the above mentioned aim, samples of the mixed liquor from an MBR treating municipal wastewater were first analysed and then, the characteristics of two MBR mixed liquors treating the leachates from two treatment plants of the organic fraction of municipal solid waste (OFMSW) were evaluated. It is noteworthy that the difference between the two industrial MBR lies on the feeding (inlet) to the MBR, which is determined by the treatment performed to the OFMSW, since one of them consists of a wet anaerobic digestion (MBR-LS) and the other of a dry anaerobic digestion (MBR-HS), so that the latter leachate contains higher concentration of suspended solids in its composition. For the chemical characterization of the mixture liquor, the extracellular polymeric substances (EPS) have been analysed. EPS are formed by the sum of extracted extracellular polymeric substances (eEPS) and soluble microbial products (SMP). These substances are considered the main cause of membranes fouling in MBRs and are basically formed by proteins and polysaccharides, which can be both attached to the cell wall and outside the cell, in form of eEPS or SMP. Regarding the physical characterization, in particular it has been analysed and studied the effect on the membrane fouling of the total and volatile suspended solids, the viscosity, the capillary suction time and the particle size, measured through the resistance to filtration. Finally, in the municipal MBR, cell viability with epifluorescence microscopy has been studied, as well as the main components of EPS have been stained by two different methods. In addition, a statistical study has evaluated the effect of the main operating parameters of the MBR on the characterization parameters of the mixed liquor. By means of least squares regression, the operational parameters that influence SMP production in industrial MBR have been studied. The study was completed by evaluating the fouling of an ultrafiltration membrane with proteins extracted from EPS and subsequently purified with ammonium sulphate at different pH values. To this end, different synthetic proteins (bovine serum albumin, casein, haemoglobin and lysozyme) were first analysed and then compared with the proteins extracted from the mixed liquor. Membrane fouling with purified eEPS proteins has also been studied along with sodium alginate added in the same concentration as the proteins. The results obtained demonstrate, firstly, that SMP play an important role in the membrane fouling. The concentration of proteins has been considerably higher than that of carbohydrates both in SMP and in eEPS, although SMP influenced to a greater extent on the filtration of the activated sludge. In addition, it is shown that bacteria under stress conditions, caused for example by increase in conductivity, increase the production of SMP, and therefore, membrane fouling increases. On the other hand, it is concluded that a low hydraulic retention time favours a high carbohydrates concentration and consequently drives to an increase in the viscosity and capillary suction time, also increasing the membrane fouling. / En la presente Tesis Doctoral se ha llevado a cabo el estudio de la influencia de los parámetros de operación del proceso de fangos activos en las características físicas y químicas de los licores de mezcla, procedentes de diferentes biorreactores de membrana (MBR). Además, se ha realizado una caracterización óptica del licor de mezcla. Para ello, en primer lugar se tomaron muestras del licor de mezcla de un MBR que trata aguas residuales urbanas y, a continuación, se evaluaron las características de los licores de mezcla de dos MBR que tratan los lixiviados procedentes de dos plantas de tratamiento de la fracción orgánica de los residuos sólidos urbanos (FORSU). Cabe destacar que la diferencia entre los dos MBR industriales radica en la alimentación (afluentes) al MBR, que viene determinada por el tratamiento que se realiza a la FORSU, ya que uno de ellos consiste en una digestión anaerobia en vía húmeda (MBR-LS) y, el otro, en una digestión anaerobia en vía seca (MBR-HS), por lo que este último lixiviado contiene mayor concentración de sólidos en suspensión en su composición. Para la caracterización química del licor de mezcla, se han analizado las sustancias poliméricas extracelulares (EPS), formadas por la suma de las sustancias poliméricas extracelulares extraídas (eEPS) y los productos solubles microbianos (SMP). Estas sustancias se consideran las principales causantes del ensuciamiento de las membranas del MBR y están formadas básicamente por proteínas y polisacáridos, los cuales pueden estar tanto adheridos a la pared celular como fuera de la célula, en forma de eEPS o SMP. En cuanto a la caracterización física, en concreto se ha analizado y estudiado el efecto en el ensuciamiento de las membranas de los sólidos en suspensión totales y volátiles, la viscosidad, el tiempo de succión capilar y el tamaño de partícula, medido a través de las resistencias a la filtración. Finalmente, en el MBR urbano se ha estudiado la viabilidad celular con microscopía de epifluorescencia, así como se han teñido para su caracterización óptica los principales componentes de las EPS por dos métodos distintos. Además, mediante un estudio estadístico se ha evaluado el efecto de los principales parámetros de operación de los MBR sobre los parámetros de caracterización del licor de mezcla. Mediante regresión por mínimos cuadrados se han estudiado los parámetros operacionales que influyen en la producción de SMP en los MBR industriales. El estudio se ha completado evaluando el ensuciamiento de una membrana de ultrafiltración con proteínas extraídas de las EPS y posteriormente purificadas con sulfato amónico, a diferentes valores de pH. Para ello, en primer lugar se han caracterizado diferentes proteínas sintéticas (albúmina de suero bovino, caseína, hemoglobina y lisozima) para compararlas con las proteínas extraídas del licor de mezcla. También se ha estudiado el ensuciamiento de la membrana con las proteínas purificadas de las eEPS junto con alginato de sodio en la misma proporción. Los resultados obtenidos demuestran en primer lugar que los SMP juegan un papel importante en el ensuciamiento de las membranas. Tanto en su composición como en la de las eEPS, la concentración de proteínas determinada ha sido considerablemente mayor que la de carbohidratos, si bien éstos influyen incluso en mayor medida en la filtrabilidad del fango activo. Además, se demuestra que las bacterias bajo condiciones de estrés, causado por ejemplo por aumento de conductividad, aumentan la producción de SMP, y por tanto, se incrementa el ensuciamiento de las membranas. Por otro lado, se concluye que un tiempo de retención hidráulico bajo favorece una concentración elevada de carbohidratos y consecuentemente provoca un aumento de la viscosidad y el tiempo de succión capilar, aumentando también el ensuciamiento de la membrana. / En la present Tesi Doctoral s'ha dut a terme l'estudi de la influència dels paràmetres d'operació del procés de fangs actius en les característiques físiques i químiques de licors de mescla, procedents de diferents biorreactors de membrana (MBR). A més, s'ha realitzat una caracterització òptica del licor de mescla. Per a això, en primer lloc es van prendre mostres del licor de mescla d'un MBR que tracta aigües residuals urbanes i, a continuació, es van avaluar les característiques dels licors de mescla de dos MBR que tracten els lixiviats procedents de dues plantes de tractament de la fracció orgànica dels residus sòlids urbans (FORSU). Cal destacar que la diferència entre els dos MBR industrials radica en l'alimentació (afluents) al MBR, que ve determinada pel tractament que es realitza a la FORSU, ja que un d'ells consisteix en una digestió anaeròbia en via humida (MBR-LS) i, l'altre, en una digestió anaeròbia en via seca (MBR-HS), per la qual cosa este últim lixiviat conté major concentració de sòlids en suspensió en la seua composició. Per a la caracterització química del licor de mescla, s'han analitzat les substàncies polimèriques extracel¿lulars (EPS), formades per la suma de les substàncies polimèriques extracel¿lulars extretes (eEPS) i els productes solubles microbians (SMP). Estes substàncies es consideren les principals causants de l'embrutiment de les membranes del MBR i estan formades bàsicament per proteïnes i polisacàrids, els quals poden estar tant adherits a la paret cel¿lular com fora de la cèl¿lula, en forma d'eEPS o SMP. Quant a la caracterització física, en concret s'ha analitzat i estudiat l'efecte en l'embrutiment de les membranes dels sòlids en suspensió totals i volàtils, la viscositat, el temps de succió capil¿lar i la grandària de partícula, mesurat a través de les resistències a la filtració. Finalment, en el MBR urbà s'ha estudiat la viabilitat cel¿lular amb microscòpia d'epifluorescència, així com s'han tenyit per a la seua caracterització òptica els principals components de les EPS per dos mètodes distints. A més, per mitjà d'un estudi estadístic s'ha avaluat l'efecte dels principals paràmetres d'operació dels MBR sobre els paràmetres de caracterització del licor de mescla. Per mitjà de regressió per mínims quadrats s'han estudiat els paràmetres operacionals que influeixen en la producció de SMP en els MBR industrials. L'estudi s'ha completat avaluant l'embrutiment d'una membrana d'ultrafiltració amb proteïnes extretes de les EPS i posteriorment purificades amb sulfat amònic, a diferents valors de pH. Per a això, en primer lloc s'han caracteritzat diferents proteïnes sintètiques (albúmina de sèrum boví, caseïna, hemoglobina i lisozima) per a comparar-les amb les proteïnes extretes del licor de mescla. També s'ha estudiat l'embrutiment de la membrana amb les proteïnes purificades de les eEPS junt amb alginat de sodi en la mateixa proporció. Els resultats obtinguts demostren en primer lloc que els SMP juguen un paper important en l'embrutiment de les membranes. Tant en la seua composició com en la de les eEPS, la concentració de proteïnes determinada ha sigut considerablement major que la de carbohidrats, si bé estos influeixen inclús en major grau en la filtrabilidad del fang actiu. A més, es demostra que els bacteris baix condicions d'estrès, causat per exemple per augment de conductivitat, augmenten la producció de SMP, i per tant, s'incrementa l'embrutiment de les membranes. D'altra banda, es conclou que un temps de retenció hidràulic baix afavoreix una concentració elevada de carbohidrats i conseqüentment provoca un augment de la viscositat i el temps de succió capil¿lar, augmentant també l'embrutiment de la membrana. / Zuriaga Agustí, E. (2017). Influencia de las características físicas y químicas del licor de mezcla en Bioreactores de Membrana y su correlación con los parámetros de operación en aguas residuales urbanas e industriales [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90512 / TESIS

The use of Reverse osmosis (RO) membranes have been significantly increasing in water desalination, and the main operational obstacle in RO desalination plants is membrane fouling. Among other solutes, dissolved biopolymers, such as polysaccharides can lead to severe membrane fouling especially with the addition of calcium ions because of the complexation formation between the surface of membrane and foulants materials. However, this complexation can also take place in the feed bulk, resulting in foulants aggregates formation. Although there are some physical techniques that can maintain the membrane performance without reducing its lifetime, only chemical cleanings are still commonly used in RO plants. In this study, a novel cleaning method is proposed to restore the membrane performance by removing the deposited foulants without reducing the membrane lifetime. The cleaning method is based on using water saturated with dissolved CO2 gas, and its principle is based on producing spontaneous CO2 bubbles due to local pressure difference leading to nucleation of bubbles throughout the membrane surface, especially at nucleation sites, which improve the cleaning efficiency. Alginic acid sodium salt was used as a model of polysaccharides foulants in presence of different concentrations of NaCl and calcium ions aiming to enhance membrane fouling, and then CO2 cleaning solution efficiency, in terms flux recovery (FR), was tested under different operating conditions and compared to other cleaning methods. Average FR of 20%±3, 25%±3 and 80%±3 for MilliQ water, a cleaning solution at pH4, and CO2 solution at 6 bar, 0.17 m/s, and 23 ̊C ±0.2 for 6 minutes were obtained, respectively. The efficiency of this novel cleaning method was also compared to direct osmosis overnight, and the average flux was comparable (about 60%±3), though that the cleaning time was significantly different. Various calcium concentrations (0-10 mM) were added in the alginate solution to study the fouling behavior in terms of the potential for bulk complexation to form cake alginate layer on the membrane surface rather than a gel layer, and the role of CO2 bubbles nucleation to remove foulants was investigated. This cleaning method can be considered as an alternative more environmentally friendly technique in RO application.

Membrane fouling, which is caused by deposition/adsorption of foulants on the surface or within membrane pores, still remains a bottleneck that hampers the widespread application of membrane bioreactor (MBR) technology for wastewater treatment. Recently membrane surface modification has proved to be a useful method in water/wastewater treatment to improve the surface hydrophilicity of membranes to obtain higher water fluxes and to reduce fouling. In this study, membrane modification was investigated by depositing a thin film of same thickness of TiO2 on the surface of an ultrafiltration alumina membrane. Various thin-film deposition (TFD) methods were employed, i.e. electron-beam evaporation, sputter and atomic layer deposition (ALD), and a comparative study of the methods was conducted to assess fouling inhibition performance in a lab-scale anaerobic MBR (AnMBR) fed with synthetic municipal wastewater. Thorough surface characterization of all modified membranes was carried out along with clean water permeability (CWP) tests and fouling behavior by bovine serum albumin (BSA) adsorption tests. The study showed better fouling inhibition performance of all modified membranes; however the effect varied due to different surface characteristics obtained by different deposition methods. As a result, ALD-modified membrane showed a superior status in terms of surface characteristics and fouling inhibition performance in AnMBR filtration tests. Hence ALD was determined to be the best TFD method for alumina membrane surface modification for this study. ALD-modified membranes were further characterized to determine an optimum thickness of TiO2-film by applying different ALD cycles. ALD treatment significantly improved the surface hydrophilicity of the unmodified membrane. Also ALD-TiO2 modification was observed to reduce the surface roughness of original alumina membrane, which in turn enhanced the anti-fouling properties of modified membranes. Finally, a same thickness of ALD-TiO2 and ALD-SnO2 modified membranes were tested for alginate fouling inhibition performance in a dead-end constant-pressure filtration system. This is the first report on the application of SnO2-modified ceramic membrane for testing its alginate fouling potential; which was determined to be nearly-same for both modified membranes with a negligible amount of difference. This revealed SnO2 as a potential future anti-foulant to be tested for membrane modification/fabrication for application in water/wastewater treatment systems.