Tesi: "Biofouling"

1

Smith, Gordon William Graham. "Biofouling of dental handpieces." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/3075/.

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Dental handpieces (HP’s) are used during semi-critical and critical dental procedures that imply the HP must be sterile at the point of use. The aim of this study was to undertake a quantitative and qualitative analysis of dental HP contamination to inform the development of HP cleaning. Preliminary validation work on protein desorbtion methods and protein detection assays resulted in boiling in 1% sodium dodecylsulphate (SDS) and the o-phthaldialedhyde (OPA) assay (sensitivity 5 μg/ml) selected for further use in this study. A quantitative and qualitative analysis of HP microbial and protein contamination was then undertaken. Before decontamination, bacteria were isolated from high speed HP’s (n=40) (median 200 cfu, range 0-1.9x104 CFU/instrument), low speed HP’s(n-40) (median 400 cfu, range 0-1x104 CFU/instrument) and surgical HP’s (n=20) (median 1x103, range 0-3.7x104 CFU/instrument). A range of oral bacteria were identified in addition to Staphylococcus aureus and Propionibacterium acnes. Protein was detected from high speed HP’s (median 1.3, range 0- 210g), low speed HP’s (median 15.41 μg, range 0 - 448 μg) and surgical HP’s (median 350 μg, range 127.5– 1,936 μg) before decontamination. Serum albumin and salivary mucin were identified on surgical HP’s before decontamination. Calcium based deposits and contaminants trapped in lubricating oil were also detected using scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX). The efficacy of detergents and a HP cleaning solution at cleaning HP contaminants was assessed in vitro with a standard test soil and disruption of biofilms with a range of cleaning efficacies noted from each cleaning solution tested. Alkaline detergents caused a significant biomass disruption of P. acnes biofilms compared to ROH2O alone. HP cleaning solution resulted in fixation of the biofilm and blood to the surface. The efficacy of novel HP cleaning machines was also assessed using a test soil based on the data generated in this study. Efficacy varied between devices tested with one demonstrating efficient protein removal in all but 1 HP location. The data presented describes a quantitative and qualitative assessment of common contaminants of HP’s, mainly bacteria, salivary mucin and serum albumin. In-vivo biofouling levels of HP’s are several fold lower than standard test soil formulations and consideration should be given to use of HP test soil based on in-vivo data to validate HP cleaning processes. The data generated in this thesis should aid in designing dental HP test soils and cleaning regimens.

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2

Arnaud, Damien. "Biofouling on reverse osmosis membranes." Thesis, Arnaud, Damien (2015) Biofouling on reverse osmosis membranes. Honours thesis, Murdoch University, 2015. https://researchrepository.murdoch.edu.au/id/eprint/29838/.

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Membrane biofouling is a major concern in water treatment processes as it can significantly reduce the system’s efficiency. Biofouling is mainly caused by microorganisms, and is difficult to control or avoid. It leads to higher operating pressure which strains the membrane, shortens the membrane life, and increases maintenance costs. Multiple literature reviews suggest that the main contributors to membrane biofouling are polysaccharides. This is why in this project two model polysaccharides (alginate and xanthan) were used to study their individual fouling effects on reverse osmosis efficiency, as well as their fouling effects coupled with calcium chloride on the same system’s efficiency. During experiments, the polysaccharides were used in 0.2g/L concentrations, while calcium chloride was used at a concentration of 1.3mM. Because alginate and xanthan are two different types of polysaccharides, they would be expected to have different physical and chemical properties and thus have different fouling behaviours. It was found that the polysaccharides did not have much effect on the system’s efficiency in the absence of calcium chloride. In experiments where calcium chloride was added in the feed solution with the polysaccharide, it was demonstrated that the addition of salt led to increased membrane fouling and greater decreases in system efficiency. The fouled membranes were kept for confocal laser scanning microscopy of the fouling layers. The images determined the general structure of the cake formed on the membrane. Using the Imaris software, calculations on the average volume the cake layer was occupying (bio-volume) and the average compactness of the cake layer could be done. During experiments, the membrane showed good salt rejections with over 96% salt rejection for each experiment

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3

Suwannakarn, Monthat. "Biofouling on forward osmosis system." Thesis, Suwannakarn, Monthat (2016) Biofouling on forward osmosis system. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/33949/.

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Fouling is an inevitable issue that all membrane systems have to face. The presence of membrane fouling causes membrane systems (such as reverse osmosis and forward osmosis) to suffer the increase of resistance thus reducing the efficiency of the systems. This raises concerns about the osmosis technology as it also reduces the system and membrane lifetime while increasing the maintenance costs. From previous papers and literature review, polysaccharides were found to be the main contributor to membrane fouling. The literature explains the polysaccharides that caused the membrane fouling were alginate, BSA, AHA, xanthan and others however, only alginate and xanthan were tested in this research project. The mixing interaction of other cations such as Ca2+ with some of the aforementioned polysaccharides (salt in the form of CaCl2 and NaCl were also tested to see the changes in fouling effects when both are combined. Throughout the experiments, a fixed amount of NaCl and CaCl2 and the polysaccharide were kept constant. The draw solution (NaCl mixed with DI water) was always retained to be saturated. These experiments were designed in this way to examine the differences between each polysaccharide and its combination towards fouling behaviour, since alginate and xanthan have different chemical characteristics. The results show that xanthan causes a higher resistance compared to alginate. In the case where NaCl and CaCl2 were present in the feed solution, the resistance of both polysaccharides greatly increases thus resulting in lowering the flux and ultimately decreasing the system efficiency. Out of all the experiments, the xanthan with salt resulted in highest flux decrease while the alginate only had the least flux decline (excluding the baseline experiment). Further analysis was done using the total organic carbon (TOC) and confocal laser scanning microscopy (CLSM). These examinations demonstrated the characteristics and properties of the polysaccharide layers that were formed on the membrane surface. The CLSM result was compared with the flux and resistance movement and it was found that they supported each other (and the findings were closely related). Since CLSM analysis is able to show the x, y and z dimension, the thickness can be found within each CLSM images. Therefore the thickness of the polysaccharide (fouling) layer (from CLSM images) was thick and/or dense, the (a higher resistance was achieved) higher the resistance would be and vice versa.

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4

Zaghy, Amar. "Biofouling in reverse osmosis processes." Thesis, Zaghy, Amar (2016) Biofouling in reverse osmosis processes. Honours thesis, Murdoch University, 2016. https://researchrepository.murdoch.edu.au/id/eprint/33970/.

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Reverse Osmosis (RO) is a water purification technology that uses a semi-permeable membrane to remove salt and other particles from drinking water. It is the dominant technology which has overtaken many conventional systems in recent years. Membrane biofouling is the main disadvantage of using RO technology which can result in reducing the system’s efficiency. The rejected microorganisms on the surface of the membrane form a fouling layer (biofouling) which leads to a decline in permeate flux, increase of hydraulic resistance, increase in operating pressure, and shortening of the membrane life. Polysaccharides, produced by microorganisms, are the main substances responsible for membrane biofouling. In this study, two types of polysaccharides (alginate and pullulan) were used to investigate their individual fouling effects as well as their fouling effects coupled with sodium chloride and calcium chloride. 50 mM of ionic strength (27.5 g NaCl + 1.47 g CaCl2) and 0.2 g/L of polysaccharides were used in the fouling experiments conducted with a laboratory-scale reverse osmosis system. It was found that alginate lead to more reduction in system’s efficiency in comparison with pullulan. The effect of alginate on the efficiency of the system was much more severe in the presence of salt, namely sodium chloride and calcium chloride, compared to its individual effect in the absence of salt. The addition of salt led to an increase in membrane fouling and a decrease in system’s efficiency. On the other hand, it was found that pullulan enhanced the system’s efficiency when it is combined with salt. To support the above findings, a Confocal Laser Scanning Microscopy (CLSM) analysis, a Total Organic Carbon (TOC) test, and an estimation of the weight of produced fouling layers were performed. In general, analysing the results of the tests supported the findings.

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5

Tasso, Mariana Patricia. "Bioactive coatings to control marine biofouling." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-25187.

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The colonization of immersed surfaces by a myriad of marine organisms is a complex, multi-stage, species-specific process giving rise to economic and environmental costs. This unwanted accumulation of organisms in the marine environment, called biofouling, has been attacked from different fronts, going from the ‘problem-elimination-as-problem-solving’ strategy (essentially through the use of biocides) to more elaborated and environmentally-friendly options based on the principle of ‘non-stick’ or ‘easy foul-release’ surfaces, which do not jeopardize marine life viability. Several marine organisms rely on proteinaceous adhesives to secure a holdfast to surfaces. Proteolytic enzymes have been demonstrated to be effective agents against settlement and settlement consolidation onto surfaces of marine bacteria, algae, and invertebrates, their proposed mode-of-action being the enzymatic degradation of the proteinaceous components of the adhesives. So far, however, the evidence remains inconclusive since most of the published investigations refer to commercial preparations where the enzyme is mixed with other components, like additives, which obviously act as additional experimental variables. This work aims at providing clear, conclusive evidence about the potential of serine proteases to target the adhesives produced by a group of model marine biofoulers. The strategy towards the goal consisted in the preparation and characterization of maleic anhydride copolymer nanocoatings modified by a surface-bound enzyme, Subtilisin A, the active constituent of the commercial preparations reported as effective against biofouling. The enzyme-containing maleic anhydride copolymer films were characterized (enzyme surface concentration, activity, stability, roughness and wettability) and thereafter tested in biological assays with three major biofoulers: spores of the green alga Ulva linza, cells of the pennate diatom Navicula perminuta, and cyprid larvae of the barnacle Balanus amphitrite. The purpose of the biological assays was to elucidate the efficacy of the immobilized catalyst to discourage settlement and/or to facilitate removal of these organisms from the bioactive layers. Results confirmed the initial hypotheses related to the enzymatic degradation of the biological adhesives: the immobilized protease was effective at reducing the adhesion strength of Ulva spores and Navicula diatoms in a manner that correlated with the enzyme activity and surface concentration, and deterred settlement of Balanus amphitrite barnacle cyprids even at the lowest surface activity tested. By facilitating the removal of biofilm-forming diatoms and of spores of the troublesome alga Ulva linza, as well as by interfering with the consolidation of adhesion of the calcareous Balanus amphitrite macrofouler, the enzyme-containing coatings here disclosed are considered to constitute an appealing and promising alternative to control marine biofouling without jeopardizing marine life.

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6

Ekblad, Tobias. "Hydrogel coatings for biomedical and biofouling applications." Doctoral thesis, Linköpings universitet, Sensorvetenskap och Molekylfysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54304.

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Many applications share a substantial and yet unmet need for prediction and control of interactions between surfaces and proteins or living cells. Examples are blood-contacting biomaterials, biosensors, and non-toxic anti-biofouling coatings for ship hulls. The main focus of this thesis work has been the synthesis, characterization and properties of a group of coatings, designed for such applications. Many types of substrates, particularly plastics, were coated directly with ultrathin, hydrophilic polymer coatings, using a newly developed polymerization method initiated by short-wavelength ultraviolet light. The thesis contains eight papers and an introduction aimed to provide a context for the research work. The common theme, discussed and analyzed throughout the work, has been the minimization of non-specific binding of proteins to surfaces, thereby limiting the risk of uncontrolled attachment of cells and higher organisms. This has mainly been accomplished through the incorporation of monomer units bearing poly(ethylene glycol) (PEG) side chains in the coatings. Such PEG-containing “protein resistant” coatings have been used in this work as matrices for biosensor applications, as blood-contacting inert surfaces and as antibiofouling coatings for marine applications, with excellent results. The properties of the coatings, and their interactions with proteins and cells, have been thoroughly characterized using an array of techniques such as infrared spectroscopy, ellipsometry, atomic force microscopy, surface plasmon resonance and neutron reflectometry. In addition, other routes to fabricate coatings with high protein resistance have also been utilized. For instance, the versatility of the fabrication method has enabled the design of gradients with varying electrostatic charge, affecting the protein adsorption and leading to protein resistance in areas where the charges are balanced. This thesis also describes a novel application of imaging surface plasmon resonance for the investigation of the surface exploration behavior of marine biofouling organisms, in particular barnacle larvae. This technique allows for real-time assessment of the rate of surface exploration and the deposition of protein-based adhesives onto surfaces, a process which was previously very difficult to investigate experimentally. In this thesis, the method was applied to several model surface chemistries, including the hydrogels described above. The new method promises to provide insights into the interactions between biofouling organisms and a surface during the critical stages prior to permanent settlement, hopefully facilitating the development of antibiofouling coatings for marine applications.

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7

Yeh, Po Ying. "MEMS-based anti-biofouling - mechanism, devices and application." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7528.

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A novel anti-biofouling mechanism based on the combined effects of electric field and shear stress was reported. The mechanism was observed in millimeter-scale piezoelectric plates coated with different metal materials and microfabricated Micro-Electro-Mechanical Systems (MEMS) devices. Experimental observation on the quantities of protein desorption and theoretical calculations on surface interactions (van der Waals, electrostatic, hydrophobic, shear stress) have been carried out. This anti-fouling mechanism can also be activated by a vibrating micromachined Si/SiO₂ membrane. The combined effect of polyethylene glycol (PEG) grafting and application of vibration on attenuation of protein adsorption was also investigated. Vibrating PEG-grafted surfaces significantly attenuate protein adsorption, especially at low PEG grafting densities. Polymer steric interaction dominates over vibration interaction with protein on surfaces with high PEG grafting densities. Monothiol-functionalized hyperbranched polyglycidols (HPG-SH) were synthesized and self-assembled on the gold surface. The characteristics of the polymer were studied and compared with linear PEG using various surface analysis techniques. This hyperbranched polyglycidol is more resistant to protein adsorption than is linear PEG of similar molecular weight. In addition, higher molecular weight HPG shows less protein adsorption than does lower molecular weight HPG. The hyperbranched polyglycidols (without a thiol group) were further modified to generate functionality for microchannel-based liquid chromatography applications. The microchannel surface was first amino modified by allylamine plasma, and amino groups then reacted with N-hydroxy succinimide-functionalized HPGs to form strong amide bonds. The grafted HPGs are resistant to nonspecific protein adsorption. The succinimidyl ester groups degrade in water to form carboxyl groups on HPGs. By giving extra carboxyl groups to each HPG, the HPG can selectively capture positive avidin from a mixture of avidin and bovine serum albumin (BSA). To increase the capture efficiency, the microchannel was integrated with micropillar arrays as the liquid chromatography column.

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8

Coward, Rebecca L. "Preventing marine biofouling : the fouling-release-coating approach." Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419043.

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The unwanted build up of fouling organisms on immersed structures has been a problem that has been addressed over the years in many different ways, from tar and pitch on the hulls of vessels to various toxin based ablative coatings and most recently, foul-release coatings that present a non stick surface to which organisms can not adhere strongly. These foul-release coatings have been relatively successful and further investigation into the formulation of siloxane based coatings is a environmentally acceptable and commercially viable concept. The significance of the hydrophilicity of a range of cured siloxane polymers upon the attachment of marine fouling species is presented. The polymers were synthesised from polymethylhydrosiloxane (PDHS) with the grafting of hydrophilic ethoxy based, linear chains of various lengths. Following cross linking, films of these materials were characterised by Nuclear magnetic resonance (NMR), Infrared (lR) spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle goniometry, topography, thermal analysis, sorption of water, force of adhesion and nano-indentation. The films were tested by bacterial growth and attachment studies, the growth and attachment of various algal propagules and also by static raft trials. Results suggest that there is a maximum hydrophilic content possible when investigating these coatings, due to the intake of water molecules, which causes swelling and subsequent degradation of the stability of the coating. The optimum hydrophilic content for achieving minimum adhesion of fouling organisms was unclear, however, trends in experimental data were identified. The bacterial attachment and growth studies conducted upon Fucus propagules indicated an increase in growth upon the PMHS polymers with the addition of3-{2-[2-(2-methoxy-ethoxy)-ethoxy]ethoxy}- propene groups, while the Sargassum propagules illustrated a reduction in growth during the same conditions. Ulva and Enteromorpha propagules showed no visible trends in growth upon the coatings tested. The surface energy and adhesion results illustrate that the PDMS with 3-{2-[2- (2-methoxy-ethoxy)-ethoxy]-ethoxy}-propene groups were the most adhesive of the coatings teste4 (14.9 oN in comparison to 3-9 oN) but possessed the lowest surface energy (22.46 mJ m2 ). In exposure trials over a 10 month period, the peroxide cured coatings out performed the other curing systems tested, however the colonisation of the range of polymers was inconclusive.

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9

Asapu, Sunitha. "An Investigation of Low Biofouling Copper-charged Membranes." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1399633649.

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10

Zhang, Kai. "Understanding biofouling in membrane bioreactors treating synthetic paper wastewater." Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1109079842.

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11

Massons, Gassol Gerard. "Biofouling control in reverse osmosis membranes for water treatment." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/461092.

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L’osmosi inversa (OI) és una de les tecnologies de purificació d'aigua més competitives. Els sistemes d'OI han evolucionat significativament en els últims anys per a proporcionar solucions reals i sostenibles als problemes relacionats amb l'aigua. Un dels principals obstacles que impedeix l'expansió en l'ús d'OI en la reutilització de l'aigua, és la pèrdua de rendiment que els elements d'OI experimenten a l'operar amb aigües contaminades. Aquest fenomen de embrutament continua sent un dels majors reptes a resoldre per elements de OI utilitzats en plantes industrials o de tractament d'aigües residuals. A causa de la complexitat d'estudiar aquests problemes en sistemes d'escala industrial, és necessari desenvolupar protocols per reproduir els efectes en equips de laboratori. Els efectes de l’embrutament solen apareixer després de diversos mesos. No obstant, per poder realitzar la recerca en un temps realista, el procés ha ser accelerat de forma controlada i el més realista possible. S'ha estudiat l'efecte de diferents variables operacionals en el desenvolupament de l’embrutament biològic. També s'ha avaluat el paper dels paràmetres de construcció de mòduls d'OI, provant en paral·lel diferents membranes i espaciadors, per millorar el disseny d'elements resistents al embrutament. Els resultats dels assaigs realitzats demostren clarament que diferents químiques de membrana poden proporcionar una reducció significativa en els nivells de embrutament. Tot i això, es va trobar que el principal contribuent al desenvolupament dels biofilms es el espaciador. El disseny de l'espaciador es va estudiar en detall per aconseguir un comportament equilibrat en mòduls d'OI que tracten aigües amb un risc d’embrutament biològic elevat. Es van probar espaciadors amb diferents espessors, separacions i angles. Alguns dissenys van mostrar avantatges en la perdua de pressió generada, així com en l'acumulació d’embrutament biològic i orgànic. La osmosis inversa (OI) es una de las tecnologías de purificación de agua más competitivas. Los sistemas de OI han evolucionado significativamente en los últimos años para proporcionar soluciones reales y sostenibles a los problemas relacionados con el agua. Uno de los principales obstáculos que impide la expansión del uso de OI en la reutilización del agua es la pérdida de rendimiento que los elementos de OI experimentan al operar con aguas contaminadas. Este fenómeno de ensuciamiento sigue siendo uno de los mayores desafíos para los elementos de OI utilizados en plantas industriales o de tratamiento de aguas residuales. Debido a la complejidad de estudiar estos problemas en sistemas de escala industrial, es necesario desarrollar protocolos para reproducir los efectos en equipos de laboratorio. Los efectos del ensuciamiento suelen ocurrir después de varios meses. Sin embargo, para poder realizar la investigación en un tiempo realista, el proceso necesita ser acelerado de manera controlada y lo más realista posible. Se ha estudiado el efecto de diferentes variables operacionales en el desarrollo del ensuciamiento biológico. También se ha evaluado el papel de los parámetros de construcción de módulos de OI, probando en paralelo diferentes membranas y espaciadores, para mejorar el diseño de elementos resistentes al ensuciamiento. Los resultados de los ensayos realizados mostraron claramente que diferentes químicas de membrana pueden proporcionar una reducción significativa en los niveles de bioensuciamiento. Sin embargo, se encontró que el principal contribuyente al desarrollo de biofilms fue el espaciador. El diseño del espaciador se estudió en detalle para lograr un comportamiento equilibrado en módulos de OI que tratan aguas propensas al ensuciamiento biológico. Se ensayaron espaciadores con diferentes espesores, espaciamiento y ángulo. Algunos diseños mostraron ventajas en la perdida presión generada, así como en la acumulación de ensuciamiento biológico y orgánico. Reverses osmosis (RO) filtration is one of the most competitive water purification technologies. RO systems have evolved significantly in the last years to provide real and sustainable solutions to water-related problems. One of the main hurdles that hinders RO expansion in water reuse, is the loss of performance that RO elements suffer when dealing with contaminated waters. This phenomenon known as fouling, remains to be one of the biggest challenges for RO elements used in industrial or wastewater treatment plants. Due to the complexity to study these problems in large scale systems, protocols need to be developed in order to mimic full-scale plants operation on a bench scale. Fouling problems are usually occurring after several month of operations. However, for a realistic time-scale research, the process needs to be accelerated in a controlled way and as similar as possible to what would be occurring naturally. The effect of different operating variables on biofouling development was studied. The role of RO module construction was also evaluated, testing different membranes and feed spacers side-by-side, to guide the improvements on the design of fouling resistant elements. The results from the trials performed clearly showed that different membrane chemistries can provide significant reduction in the levels of biofouling detected after operation. However, it was found that the main contributor to biofilm development was feed spacer. Large differences in the amount of biofouling generated could be associated with feed spacer presence. Feed spacer design was then studied in detail to achieve a balanced performance in spiral wound RO modules treating waters prone to biofouling. Feed spacers with various thickness, spacing and angle were tested and some designs showed advantages in pressure drops, as well as on biologic and organic fouling accumulation.

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Rasmussen, Kjetil. "Marine biofouling - microbial adhesion to non-solid gel surfaces." Doctoral thesis, Norwegian University of Science and Technology, Department of Biotechnology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-519.

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The scope for this work was to develop rapid assays for enumerating microorganisms on gels, and to test whether fouling of gel surfaces is principally different from that of solid substrata. For this purpose, a standard set of different gels were selected, based on biocompatibility, polymer charge and gel strength. Bacterial adhesion to gels could be conveniently enumerated by first staining with SYBR Green I nucleic acid gel strain. Images were then collected using a confocal scanning laser microscope, followed by image analysis to determine the percent coverage of bacteria. Diatom adhesion could be qualified using a fluorescence scanner recording the fluorescent chlorophyll, showing a clear correlation between average fluorescence signals and cell density determined by counting. This method was successfully tested on glass, gels, a painted surface and an antifouling coated surface.Adhesion of the marine bacterium Pseudomonas sp. NCIMB 2021on gels decreased at higher shear rates. At low shear rates, adhesion varied significantly between different gels in the following descending order: alginate > agarose > chitosan > PVA-SbQ. Lowest cell coverage at all shear rates was recorded on the most hydrophobic gel, PVA-SbQ. Earlier work has shown that this organism adhere better to solid hydrophobic than solid hydrophilic surfaces. Thus, other properties than the surface free energy may be more important for bacterial adhesion to the gels. The marine diatom Amphora coffeaeformis was applied in the different adhesion arrays under different shear conditions. At high shear, cells adhered better to highly ionic polymer gels alginate and chitosan than to the low charge polymer gels agarose and PVA-SbQ. At very low shear, A. coeffeaeformis developed a film even on agarose equivalent to that on the charged polymer gels. Adhesion to PVA-SbQ remained low at all shear rates. As observed for solid substrate, low charge density led to reduced attachment. Settlement of Balanus amphitrite cypris larvae was tested at different polymer concentrations of the hydrogels. All gels inhibited cypris settlement compared to solid polystyrene controls. Gels consisting of 2.5% PVA-SbQ or 0.5% agarose showed the most promising antifouling properties. In all gel experiments, most of the non-settled larvae were able to settle when transferred and offered a suitable solid substratum. Results indicated that the gel strength was an important factor for cyprid settlement on gels, while the surface wettability seemed to be of minor importance.A few preliminary field experiments were carried out. These tests suggested that marine bacterial biofilm development is more readily on glass than on a PVA-SbQ gel surface, in accordance with monoculture lab experiments. However, similar amounts of photosynthetic organisms adhered to gels of agorose, alginate, chitosan and PVA-SbQ tested in an outdoor seawater basin during spring bloom. Finally, barnacle settlement was delayed on PVA-SbQ gels exposed in the open sea. After incubation for a full summer season, even those gels became as covered with marine fouling organisms as any other non-toxic surface. In conclusion, no universal antifouling effects of hydrogels were found. However, this work suggests that both adhesion of a bacterium and settlement of barnacle cypris larvae on gel surfaces may be principally different from solid substrata. Diatom adhesion, on the other hand, was lower on gels with a low charge density, as observed for solid substrata. In general, the most hydrophobic gel, PVA-SbQ, was the least attractive surface for all three organisms.

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Mahon, A. M. "Control of algal biofouling on coastal man-made structures." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517355.

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14

Wong, Yiu-ming, and 黃耀明. "Biofouling treatment of seawater cooling systems in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B42574778.

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15

Ashhuby, Bashir Ali. "Biofouling studies on reverse osmosis desalination of hypersaline waters." Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/3599/.

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Biological fouling of reverse osmosis (RO) membranes is affected by many factors, and it is not clearly understood, especially with respect to hypersaline waters. Biofouling minimisation requires understanding of the fundamentals of the biofilm development. It is also necessary to monitor biofilm development at various stages and its relation to concentration polarisation phenomena. The two main goals were to explore the biological diversity of a hypersaline lake called "Qabar-Onn"t located in the Sahara; and to better understand what biotic and abiotic factors govem biofouling of RO membranes treating hypersaline waters. Three halotolerant bacterial strains (Euhalothece species, BAAOOl and BAA002, and Halomonas pantelleriensis species, BAA003) were isolated from the lake using conventional culturing methods, and were identified based on 16S rRNA sequencing. Two isolated species, Eukalothece species BAAOOI and Halomonas pantelleriensis species BAA003 were used as model microorganisms to evaluate the potential of biofilm development on RO membranes. Salinity and surface roughness, which affect biofilm initiation and growth, were investigated. A novel, in-situ monitoring device was used to detect initiation of biofilm formation, and its relation to solutes and concentrations near RO membrane surfaces. The results showed that Qabar-Onn Lake is inhabited by a wide range of microorganisms, which seem to have a strong potential to adapt to the rapid increase in the lake salinity. In addition to salinity, pH also is limiting factor on biodiversity and microorganisms' dominance. Biofouling was strongly controlled by membrane characteristics and feed salinity. Lower surface roughness and low salinity contributed to less biofilm formation. Furthermore, the absence of monovalent anions (i. e. chloride) in the feed enhanced flux at low salinities; however, its absence severely decreased flux at higher salinities. Similarly, microorganisms present in the feed extremely enhanced the permeate flux at low salinities, however, at high salinities the flux decreased in the presence of microorganisms.

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Mott, Irene EsmeÌ Catherine. "Biofouling and corrosion studies using simulated cooling water systems." Thesis, University of Birmingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272612.

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17

Su, Xueju. "Development and evaluation of anti-biofouling nano-composite coatings." Thesis, University of Dundee, 2013. https://discovery.dundee.ac.uk/en/studentTheses/e92553a4-c3aa-49b0-8868-46a8c161ed96.

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Abstract (sommario):

The rapid development of the global offshore industry and of amphibious chemical, steel and power plants leads to more intensive use of natural water resources (sea, river and lake water) as a cooling medium. However, heat exchangers using the water as a coolant suffer from biofouling problem, which reduces heat transfer performance significantly. The cost of cleaning and lost output can be extremely high. The high incidence of infections caused by the biofilm formation on the surfaces of medical devices and implants, including catheters and bone fracture fixation pins etc. has a severe impact on human health and health care costs. An approach to reduce biofouling or infection rate is the application of a range of different coatings to the surfaces of equipment. So far the most promising coatings include Ni–P–PTFE coatings and modified diamond like carbon (DLC) coatings etc. However these coatings need to be futher improved and optimised in order to get the best anti-biofouling performance. In this study, a range of novel Ni–P–PTFE-biocide polymer nanocomposite coatings and modified DLC coatings with B, F, N, Si and Ti were designed and produced using electroless plating, magnetron sputter ion-plating and plasma enhanced chemical vapour deposition techniques. The surface properties of the coatings were characterized using surface analysis facilities, including AFM, EDX, OCA-20, SEM and XPS. These nano-composite coatings and nano-structured surfaces were evaluated with bacterial strains that frequently cause heat exchanger biofouling or medical devices-related infections. The experimental results showed that new Ni–P–PTFE-biocide polymer nanocomposite coatings reduced bacterial adhesion by 70% and 94% respectively, compared with Ni–P–PTFE and stainless steel. The experimental results showed that both type and content of the doped elements in DLC coatings had significant influence on bacterial adhesion. The new doped DLC coatings, including Si-N-DLC, F-DLC, B-DLC and Ti-DLC coatings as well as new SiOx-like coatings reduced bacterial adhesion by 60-90% compared with pure DLC and stainless steel. B and Ti-doped DLC coatings also reduced residual protein adhesion by 88-95% compared with pure DLC coatings and stainless steel. In general bacterial adhesion decreased with decreasing total surface energy or with increasing ?- surface energy of the coatings. The bacterial adhesion mechanism of the coatings was explained with extended DLVO theory.

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18

Garner, Bradley John. "Biofouling and corrosion studies of a copper-nickel alloy." Thesis, University of Surrey, 1987. http://epubs.surrey.ac.uk/847454/.

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The marine biofouling and corrosion of Kunifer 10 (10% Ni, 1. 5% Fe, copper alloy), was studied using a combination of analytical techniques including x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDXA) and electron microscopy. Particular emphasis was placed on the very early stages of fouling, although the study continued until a climax community of macrofouling organisms had become established. Dissolved organic matter (DOM), was successfully extracted from seawater by ultrafiltration and chloroform-emulsion separation. The collected materials were partially characterised using fourier transform infrared spectroscopy (FTIR) and standard chemical analyses. Extracted materials were found to be mainly carbohydrate in character, with lesser quantities of protein. The FTIR investigations indicated considerable seasonal variation in the extracted DOM. XPS proved to be a suitable technique to investigate the development of marine organic and inorganic films that form on the alloy. Adsorbed organic macromolecules exhibited a characteristic spectral "fingerprint". The effect of elevated DOM on the corrosion behaviour of the Kunifer 10 alloy was investigated, using DC and AC impedance electrochemistry. Studies indicated that a temporary loss of passivation occurred in the presence of DOM under transient oxygen conditions. The development of organic layers on the alloy was shown to influence subsequent stages of biofouling, Kunifer 10 coated with elevated levels' of organic extracts was less likely to become fouled by microorganisms, although certain extracts appeared to stimulate the settlement of marine protozoans. However, such effects were short lived due to the continual formation of bio/corrosion layers. An unusual form of corrosion, not previously documented, is reported and an explanation for the exfoliation of the bio/corrosion films on Kunifer 10 is suggested. A range of cupronickel-iron alloys were assessed for their short-term marine biofouling/corrosion performance. Of the alloys tested Kunifer 10 showed optimum resistance. The study includes a literature review on marine biofouling and corrosion.

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19

ZHANG, KAI. "UNDERSTANDING BIOFOULING IN MEMBRANE BIOREACTORS TREATING SYNTHETIC PAPER WASTWATER." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1109079842.

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20

Wong, Yiu-ming. "Biofouling treatment of seawater cooling systems in Hong Kong." Click to view the E-thesis via HKUTO, 1998. http://sunzi.lib.hku.hk/hkuto/record/B42574778.

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21

Thompson, Ina Sharon. "Optimisation of sodium hypochlorite dosing at Wylfa Power Station : an experimental study with Mytilus edulis." Thesis, Bangor University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263175.

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22

Wills, Amanda Jane. "Mitigation of biofouling using tube inserts in conjunction with biocides." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396232.

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23

Smith, Margaret J. "The use of hydrogels to prevent biofouling on underwater sensors." Thesis, University of Glasgow, 2007. http://theses.gla.ac.uk/2541/.

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Abstract (sommario):

The biofouling resistant coatings of hydrogel containing the cationic surfactants benzalkonium chloride and Arquad 2C-75 both extended the fouling free period in marine temperate waters. In the case of BAC the coating stayed clean for 10-12 weeks and the Arquad 2C-75 for 12-14 weeks. Due to the longer life of the hydrogel containing the Arquad 2C-75 instrument trials were carried out using this material. An effective method of attaching the coatings to the optical and membrane ports of sensors was developed and allows the coating to be either held in either a screw down or bolted polymer ring. The diffusion coefficient of cationic surfactants in seawater is reduced compared to diffusion coefficients in freshwater. In seawater the diffusion coefficient of benzalkonium chloride was found to be 2.44 x 10-6 cm2 s-1 compared to 7.78 x 10-6 cm2 s-1 in distilled water at 25°C. Careful choice of gas permeable membrane can result in a slightly longer biofouling lifetime, but only by 1-2 weeks. At 6 weeks all gas permeable membranes had significant fouling which affected their gas permeability. The diffusion rates of ammonia gas, a gas commonly measured in the sea, through PTFE gas sensor membranes varied between PTFE manufacturers with flux measurements ranging from 0.05-1131 µg cm-2 h-1. In addition to the hydrogel testing on instruments within this project a variety of external research groups and environmental agencies are currently testing the hydrogels on their instrumental ports.

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24

Ross, Katherine Ann. "Biofouling in suspended cultivation of the scallop Pecten maximus (L.)." Thesis, University of Liverpool, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250291.

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25

Thompson, Stephanie Eleanor Mary. "Cell biology of settlement and adhesion processes of biofouling algae." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/194/.

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Abstract (sommario):

The aim of the research presented in this thesis was to investigate the cell biology behind the settlement and adhesion processes of biofouling algae. Using the fluorescent dye FM 1-43 in Ulva zoospores to follow membrane recycling, rapid mass membrane retrieval of FM 1-43-labelled plasma membrane was found to occur to an endosomal compartment during settlement. Biolistic delivery of dextran Oregon Green BAPTA-1 and Texas Red enabled ratiometric imaging with a 5-fold greater response to Ca\(^{2+}\)-ionophores than AM-ester Ca\(^{2+}\) indicators. During settlement, zoospores exhibited both localised and diffuse increases in cytosolic calcium implying a role in secretion of the adhesive. Secretion of redox-active substrates was detected using amperometry when settled spores were mechano-stimulated. Secretory events were similar to those seen in bovine chromaffin cells with the presence of foot signals in the recordings implying a role for a ‘fusion pore’ in exocytosis. Using DAF-FM DA nitric oxide (NO) production in Seminavis robusta was found to be 4-fold greater on a surface to which the cells adhered weakly than on a surface to which they attached more strongly. Increased NO reduced attachment strength and it is thought that NO may play a signalling and/or regulatory role in diatom adhesion.

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26

Schimanski, Kate Bridget. "The importance of selective filters on vessel biofouling invasion processes." Thesis, University of Canterbury. School of Biological Sciences, 2015. http://hdl.handle.net/10092/11299.

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Abstract (sommario):

The spread of exotic species is considered to be one of the most significant threats to ecosystems and emphasises the need for appropriate management interventions. The majority of marine non-indigenous species (NIS) are believed to have been introduced via ship biofouling and their domestic spread continues to take place via this mechanism. In some countries, biosecurity systems have been developed to prevent the introduction of NIS through biofouling. However, implementing biosecurity strategies is difficult due to the challenges around identifying high-risk vectors. Reliable predictors of risk have remained elusive, in part due to a lack of scientific knowledge. Nonetheless, invasion ecology is an active scientific field that aims to build this knowledge. Propagule pressure is of particular interest in invasion ecology as it describes the quantity and quality of the propagules introduced into a recipient region and is considered to be an important determinant in the successful establishment of NIS. Environmental history affects health and reproductive output of an organism and, therefore, it is beneficial to examine this experimentally in the context of biofouling and propagule pressure. The aim of this thesis was to examine how voyage characteristics influence biofouling recruitment, survivorship, growth, reproduction and offspring performance through the ship invasion pathway. This was to provide fundamental knowledge to assist managers with identifying high-risk vessels that are likely to facilitate the introduction or domestic spread of NIS, and to understand the processes affecting biofouling organisms during long-distance dispersal events. Chapter One provides an introduction to the issues addressed in this thesis. Each data chapter (Chapters Two – Five) then focused on a stage of the invasion process and included field experiments using a model organism, Bugula neritina. Finally, Chapter Six provides a summary of key findings, discussion and the implications to biosecurity management. Throughout this thesis, the effect of donor port residency period on the success of recruits was highlighted. Chapter Two focused on recruitment in the donor region. As expected, recruitment increased with residency period. Importantly, recruitment occurred every day on vulnerable surfaces, therefore, periods as short as only a few days are able to entrain recruits to a vessel hull. The study presented in Chapter Three showed that there was high survivorship of B. neritina recruits during 12 translocation scenarios tested. In particular, the juvenile short-residency recruits (1-8 days) survived voyages of 8 days at a speed of 18 knots; the longest and fastest voyage simulated. Interestingly, variation in voyage speed and voyage duration had no effect on the survivorship of recruits, but did have legacy effects on post-voyage growth. Again, B. neritina which recruited over very short residency periods of 1 day continued to perform well after translocation and had the highest level of reproductive output after the voyage scenarios (Chapter Four). Recruits that were older (32-days) and reproductively mature at the commencement of the scenarios failed to release any propagules. Even though the number of ‘at sea’ and ‘port residency’ days were equal, reproductive output was higher after short and frequent voyages than after long and infrequent voyages. Finally, the study presented in Chapter Five examined transgenerational effects of B. nertina. Results showed that although the environmental history of the parent colony had a carry-over effect on offspring performance, it was the offspring environment that was a stronger determinant of success (measured by reproductive output and growth). Although cross-vector spread is possible (i.e. parent and offspring both fouling an active vessel), offspring released from a hull fouling parent into a recipient environment will perform better. In combination, these studies have provided new insights into NIS transport via vessel biofouling. Although shipping pathways are dynamic and complex, these results suggest that juvenile stages that recruit over short residency periods and are then translocated on short voyages, may pose a higher risk for NIS introduction than originally assumed. This has implications for marine biosecurity management as short residency periods are common and short, frequent voyages are typical of domestic vessel movements which are largely unmanaged.

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27

Parker, Emily M. "Surface active polymers as anti-infective and anti-biofouling materials." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:54e462df-b64c-499c-94ce-55d624be9a69.

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This thesis is concerned with the chemical modification of polymers in the preparation of a library of materials which exhibit altered surface properties as a result of the surface chemical functionality, with particular emphasis on the development of materials that control biofouling and are antibacterial. Chemical modification of crosslinked polystyrene, in film and microsphere form, was carried out by carbene insertion followed by diazonium coupling. This provided access to a collection of materials with varying surface chemistry, whilst the bulk properties of the polystyrene substrates were maintained. Synthesis of the diaryldiazo and the diazonium salts used to perform the surface modifications is described, as well as the preparation and characterisation of the materials. Analysis of the ability of the materials to adsorb and bind the protein bovine serum albumin (BSA) is presented with data obtained from two methods of observation. Quartz Crystal Microbalance with Dissipation (QCM-D) and a protein assay based on the change in optical density of a BSA/PBS solution are used to demonstrate how the specific surface chemistry of the materials influences the ability to adsorb and bind protein. The behaviour of the materials was time dependent and was rationalised with respect to the surface water contact angle and the calculated parameters polar surface area and % polar surface area of the functional groups added to the surfaces. Finally, penicillin loaded materials were prepared and their antibacterial activity was tested against E. coli and S. aureus, demonstrating that the antibiotic is still active from within the polystyrene scaffold.

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28

Powell, Lydia Charlotte. "The biofouling of reverse osmosis membranes : from characterisation to control." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa42695.

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Abstract (sommario):

Membrane technology can be utilised for the high purification and desalination of water. However membrane filtration processes are commonly impeded by membrane fouling, which can lead to flux decline and an overall reduction in separation efficiency within the process. Therefore the aim of this research study was a comprehensive investigation of the issue of biofouling on industrial RO membranes through molecular biology techniques, characterisation of surface charge of foulant bacteria and RO membrane surface and AFM imaging and force measurements on clean and fouled membranes for the determination of adhesion force and micromechanical properties. The laboratories within Gwangju Institute of Science and Technology, South Korea and Swansea University, Wales were equipped for the scope of this research work. Research focused on the extraction of microbial DNA obtained from fouling layers on the surface of Reverse Osmosis Membranes obtained from the Fujairah Water and Power Plant, UAE. The use of the culture independent method of the molecular technique based on the 16S rDNA sequence and constructed gene libraries, was then used to determine the bacterial species that caused significant fouling on the RO membrane. Four bacterial species isolated from the fouling layer from the RO membrane were characterised in terms of electrophoretic mobility and zeta potential to determine the cell surface charge within various industrial relevant environments for the elucidation of cell adhesion mechanisms to the membrane surface. AFM images of virgin and fouled membranes were obtained and analysed to reveal the roughness of the surface which could influence fouling and the surface charge of the membranes were measured through the method of streaming potential at various industrial relevant environments to further elucidate the mechanisms of cell adhesion to the membrane surface. Force measurements were performed to reveal the adhesion force and elasticity values of virgin, process fouled and purposely fouled with the four bacterial isolates, to determine process behaviour in various environmental conditions. Through this research and future work, it is hoped that a rational strategy for economic and effective cleaning processes will be developed which will maintain efficient membrane operation and prolong membrane life, thus enabling the reduction of operating costs of such processes.

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29

Hausman, Richard. "Development of Low-Biofouling Polypropylene Feed Spacers for Reverse Osmosis." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1320891800.

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30

Seth, Duvall S. "A Study in Biofouling Prevention and Removal via Acoustic Cavitation." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1554854930764174.

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31

Ramsden-Lister, Eleanor. "Risk-based corrosion and biofouling management for tidal stream devices." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/7181/.

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32

Brain, Stephen. "Monitoring microbial biofilms." Thesis, London South Bank University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337401.

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33

Hou, Huiyi, and 侯慧仪. "Marine biofouling organisms respond to multiple stressors in a changing climate." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/194551.

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Abstract (sommario):

The marine environment is likely to experience profound climate change in the coming 100 years and beyond. Ocean acidification (OA) is one of the climate change issues attracting the attention of researchers all over the world. The decreasing pH of the oceans might threaten marine biofouling organisms. However, climate change is not only involved with ocean acidification (OA) but the change of other environmental variables, such as temperature and salinity. These environmental factors act as multiple stressors and synergistically affect shell-forming biofoulers, in which, the calcium carbonate skeleton structure plays an important role of protection. Previous studies regarding the response of marine biofoulers to the environmental stressors were generally summarized in this article. Then a calcifying biofouling tube worm, Hydroides elegans, were reared from larval stage to early juvenile stage under control and treatment conditions to examine the combined effects of temperature (24, 30°C), pH (8.1, 7.7) and salinity (34, 27ppt). Juvenile growth and chemical composition (Mg/Ca and Sr/Ca) of their calcareous tubes were tested and used as assessment of effects of the three environmental stressors. The experiment revealed that H. elegans was robust to the environmental change because juvenile development positively responded to temperature and the interaction between temperature and salinity. Other combinations did not exert significant effect. The results suggest the need of further study of proteomics and transcriptomics to reveal the mechanisms of calcification as well as long-term studies to examine the energy costs of adaptation. In addition, the non-significant chemical composition (Mg/Ca and Sr/Ca) of the tube of this organism suggest a need of further exploration of the same animal but not only focus on three factors but the seawater chemical composition as well. published_or_final_version Environmental Management Master Master of Science in Environmental Management

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34

Cowle, Matthew. "Assessing the impact of biofouling on the hydraulic efficiency of pipelines." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/72134/.

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Abstract (sommario):

Pipeline distribution systems account for the vast majority of the physical infrastructure in the water industry. Their effective management represents the primary challenge to the industry, from both an operational and public health standpoint. Biofouling has a ubiquitous presence within these systems, and it can significantly impede their efficiency, through an increase in boundary shear caused by characteristic changes in surface roughness dynamics. Nonetheless, conventional pipeline design practices fail to take into account such effects, partially because research findings that could contribute to upgraded and optimised design practices appear inconsistent in the literature. The overall aim of this study was to improve the current scientific understanding of biofouling within water and wastewater pipelines; for the purpose of instigating a step-change in pipeline design theory by incorporating biofouling, thereby enabling future pipelines to be as sustainable as possible. The nature of the problem, necessitated the need for a multidisciplinary approach, based upon engineering and microbiological principles and techniques. The primary focus of this study was to investigate the impact of biofouling on surface roughness, mean flow structure and sediment transport within wastewater systems. To this effect biofilms were incubated with a synthetic wastewater on a High Density Polyethylene pipe, within a purpose built pipeline facility for 20 days, at three steady-state flow regimes, including the average freestream velocities of 0.60, 0.75 and 1.00 m/s. The physico-chemical properties of the synthetic wastewater were purposely designed to be equivalent to the properties associated with actual wastewater found within typical European sewers. The impact of biofouling on flow hydrodynamics was comprehensively identified using a series of static pressure tappings and a traversable Pitot probe. Molecular and image analysis was also undertaken to support the observations derived from the aforementioned measurements, particularly with regards to the structural composition and mechanical stability of the biofouled surfaces. The study has confirmed that the presence of a low-form gelatinous biofilm can cause a significant increase in frictional resistance and equivalent roughness, with increases in friction factor of up to 85% measured over the non-fouled values. The reported increases in frictional resistance resulted in a reduction in flow rate of up to 22% and increased the pipe’s self-cleansing requirements. The structural distribution of a biofilm was shown to play a key role in its overall frictional capacity and strength, which in turn was found to be a function of the biofilms conditioning shear. In particular, it was found that a biofilm conditioned at higher shear will have less of an impact on a pipe’s overall frictional resistance, although, will be stronger and more difficult to remove than a biofilm conditioned at lower shear. The biofilm’s impact on frictional resistance was found to be further compounded by the fact that traditional frictional relationships and their derivatives are not applicable to biofouled surfaces in their current manifestation. In particular, the von Kármán constant, which is an integral aspect of the Colebrook-White equation is non-universal and dependent on Reynolds Number for biofouled surfaces. It was found that the most suitable manner to deal with the dynamic and case-specific nature of a biofouled surface was to quantify it using a series of dynamic roughness expressions, the formulation of which were the culmination of this study, and should be the focus for further research. The influence of different plastic based pipe materials and flow regimes on biofilm development within drinking water distribution systems was also briefly investigated using a series of flow cell bioreactors and molecular analysis techniques. Keywords: Biofilm; biofouling; pipe; hydraulic efficiency; equivalent roughness; von Kármán constant; Colebrook-White equation; drainage network; wastewater; drinking water.

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35

ZHANG, KAI. "REDUCING BIOFOULING IN MEMBRANE BIOREACTORS TREATING SYNTHETIC EARLY PLANETARY BASE WASTEWATER." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1189560153.

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36

Sprick, Conor G. "FUNCTIONALIZATION OF SILVER NANOPARTICLES ON MEMBRANES AND ITS INFLUENCE ON BIOFOULING." UKnowledge, 2017. http://uknowledge.uky.edu/cme_etds/77.

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Abstract (sommario):

Ultrafiltration (UF) processes are often used as pretreatment before more retentive/costly processes, such as nanofiltration and reverse osmosis. This study shows the results of low-biofouling nanocomposite membranes, loaded with casein-coated silver nanoparticles (casein-Ag-NPs). Membranes were cast and imbedded with Ag-NPs using two approaches, physical blending of Ag-NPs in the dope solution (PAg-NP/CA membranes) and chemical attachment of Ag-NPs to cast membranes (CAg-NP/CA membranes), to determine their biofouling control properties. The functionalization of Ag-NPs onto the CA membranes was achieved via attachment with functionalized thiol groups with the use of glycidyl methacrylate (GMA) and cysteamine chemistries. The immobilization chemistry successfully prevented leaching of silver nanoparticles during cross-flow studies. Pseudomonas fluorescens Migula in brackish water was used for short-term dead-end filtration, where CA and CAg-NP/CA membranes displayed lower flux declines as compared to PAg-NP/CA membranes. In subsequent long-term biofouling studies, also with Pseudomonas fluorescens Migula in brackish water with addition of sodium acetate, chemically-attached Ag-NPs led to a significant reduction in the accumulation of bacterial cells, likely due to the more dispersed nanoparticles across the surface. Therefore, a method was developed to chemically immobilize Ag-NPs to membranes without losing Ag-NP’s antimicrobial properties.

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37

Schumacher, James Frederick. "Control of marine biofouling and medical biofilm formation with engineered topography." [Gainesville, Fla.] : University of Florida, 2007. http://purl.fcla.edu/fcla/etd/UFE0021311.

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38

Othmani, Ahlem. "Médiation chimique entre l’algue brune méditerranéenne Taonia atomaria et la communauté bactérienne associée à sa surface." Thesis, Toulon, 2014. http://www.theses.fr/2014TOUL0001/document.

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Abstract (sommario):

Dans le milieu marin, toute surface immergée est rapidement colonisée par des bactéries, puis par d’autres micro-organismes, conduisant à la formation de structures tridimensionnelles complexes appelées biofilms. Cette étape est généralement suivie par l’installation de macro-colonisateurs. Néanmoins, un certain nombre d’organismes marins, tels que les macro-algues, présentent des surfaces peu épiphytées à l’échelle macroscopique. Des algues méditerranéennes (Taonia atomaria et Dictyota spp.) ont été sélectionnées dans le cadre de ces travaux de thèse pour leur capacité à conserver leur surface peu colonisée. Cependant, des observations de leurs surfaces par microscopie ont montré l’existence de biofilms diversifiés à la surface de leurs thalles. Le but de cette thèse est de mieux comprendre les mécanismes de médiation chimique entre ces algues et les bactéries associées à leur surface. La première partie de ce travail a été consacrée à l’étude du rôle de molécules d’origine algale vis-à-vis de l’adhésion de bactéries marines. Pour cela, la composition chimique totale des algues sélectionnées a été analysée conduisant à l’isolement et à la caractérisation structurale de 12 molécules, dont trois se sont révélées être originales. L’activité anti-adhésion de la majorité de ces composés a ensuite été évaluée : le 1-O-octadecenoylglycérol s’est avéré être le produit le plus actif (20 µM < CE50 <55 µM). La deuxième partie a été dédiée plus particulièrement à l’étude du métabolome de surface de T. atomaria dans le but d’évaluer son implication dans les interactions écologiques entre l’algue et les bactéries associées à sa surface. Un protocole d’obtention et d’analyse spécifique des extraits surfaciques a tout d’abord été développé. Ce protocole est basé sur le trempage des thalles dans des solvants organiques et un contrôle de l’intégrité des cellules membranaires des algues y est associé. L’échantillonnage a été effectué mensuellement à Carqueiranne (Nord-ouest de la Méditerranée, France) durant la période allant de février à juillet 2013. Les résultats obtenus montrent qu’un sesquiterpène est exprimé majoritairement à la surface de l’algue. Il a été démontré que ce composé inhibe l’adhésion de souches bactériennes de référence tout en restant inactif vis-à-vis de celles isolées à la surface de l’algue. Une telle spécificité n’a pas été observée ni dans le cas de biocides commerciaux, ni pour les autres métabolites produits par T. atomaria. Dans un second temps, un suivi saisonnier des extraits de surface ainsi que des communautés bactériennes associées a été effectué par métabolomique (LC-MS) et DGGE, respectivement. Des fluctuations saisonnières de ces deux paramètres ont été reportées sans mettre en évidence de corrélation évidente entre eux. La présence de la molécule majeure de surface durant tout le suivi saisonnier a été notée ainsi que sa capacité à diffuser dans l’eau de mer. Enfin, l’étude de l’implication potentielle des bactéries associées à T. atomaria dans le contrôle du biofilm a été entreprise en évaluant l’activité de leurs extraits vis-à-vis de l’adhésion de souches de référence. En conclusion, nous émettons l'hypothèse que T. atomaria pourraient contrôler partiellement le biofilm associé à sa surface en faisant intervenir des métabolites spécifiques In the marine environment, all submerged surfaces are rapidly colonized by bacteria and other microorganisms, resulting in the formation of complex three-dimensional structures called biofilms. This step could be followed by the attachment of macro-colonizers. Nevertheless, a number of marine organisms, such as macro-algae, appeared to be relatively free of epibionts at a macroscopic scale. In this study, several Mediterranean algae (Taonia atomaria and Dictyota spp.) were selected for their ability to keep their surface free of biofouling. However, microscopic techniques allowed the observation of a diversified biofilm on the surface of their thalli. The purpose of this work was to understand how this alga could interact with its associated bacteria using a chemical ecological approach. The first part of this work deals with studying the anti-adhesion properties of algal molecules against a range of marine bacteria. For this, the whole chemical composition of the two algae was analyzed leading to the isolation and structural characterization of 12 molecules from which three were found to be new. The anti-adhesion activity of some of these compounds was then evaluated: 1-O-octadecenoylglycerol proved to be the most active product (20 µM < EC50 <55 µM). The second part of this study was dedicated to the study of the surface metabolome of T. atomaria in order to assess its involvement in the ecological interactions between the alga and its associated bacteria. A specific extraction protocol was optimized for the surface compounds using a dipping technique in organic solvents associated with the integrity control of algal cell membrane. Sampling was carried out monthly at Carqueiranne (N W Mediterranean Sea, France) between February and July 2013. The results showed the presence of a major molecule in accordance with a sesquiterpenic structure. Anti-adhesion capacity against reference bacterial strains was noticed for this compound, while it remained inactive against strains isolated from the algal surface. This specificity was not observed for commercial biocides and the other molecules purified from crude algal extracts of T. atomaria. Then, changes in surface extracts and associated bacterial surface communities were monitored using metabolomics (LC-MS) and DGGE, respectively. Seasonal fluctuations for the two parameters could be reported without any evident correlation between them. The occurrence of the major molecule throughout the seasonal monitoring was also noticed and its capacity to diffuse in the marine environment was shown. Finally, the study of the potential involvement of the associated bacteria in the biofilm control was conducted by evaluating the anti-adhesion activity of their crude extracts against reference strains. In conclusion, we hypothesize that T. atomaria could control at least partially the biofilm at its surface using specific metabolites

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39

Chen, Ming-Jen. "Mechanical strength and destruction of biofilms in pipes." Thesis, University of Birmingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368475.

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40

Gunn, N. "Marine biofilm development on titanium with particular reference to seawater heat exchange systems." Thesis, University of Portsmouth, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234641.

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41

Proud, Sarah Victoria. "Tributyltin pollution and the bioindicator Nucella lapillus : population recovery and community level responses." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260333.

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Abstract (sommario):

The detrimental effects of tributyltin (TBT) have been recorded on many marine organisms. As a result the UK Government imposed a partial ban on the use of organotin antifouling paints on boats less than 25 m in length, in 1987. In 1988 the Isle of Man Government followed suit introducing a licensing procedure restricting all uses of organotins. At concentrations less than 0.5 ng Sn/I female Nucella lap/Nus develop imposex - the superimposition of male sexual characteristics. To date there have been few studies measuring the recovery of Nucella populations after the introduction of restrictions. This study produces evidence of the extent of recovery in Nucella populations from sites in the south-west of England and on the Isle of Man. The recovery observed was measured by decreasing values of relative penis size, vas deferens sequence and the percentage of sterile adult females in the population. Following the 1987 ban the recovery of Nucella populations in the south-west has shown a linear response allowing predictions to be made for the time scale of complete recovery. In addition concentrations of TBT in the water and tissues of selected indicator organisms also showed decreases. Around the Isle of Man the illegal use of TBT paints was identified and later discouraged by the Marine Administration which was followed by a reduction in TBT concentrations in the water at sites around the Isle of Man. Levels of imposex in dogwhelk populations around the Isle of Man have decreased. Although effects of TBT on Nuce/la have been well documented at the cellular and individual level, the knock on effects on the community have not been investigated. Manipulative field experiments were used to demonstrate the role of Nucella lapd/us in structuring shore communities to allow predictions of the effect of TBT to be made. Rather than using the traditional approach of fences and cages, dogwhelks were removed by hand on regular visits to experimental sites creating treatments with reduced abundances of dogwhelks akin to shores affected by TBT. The role of Nucel/a was examined at different stages of a cycle existing on moderately exposed Manx shores where Fucus vesiculosus and Semibe/anus balanoides fluctuate in abundance. The removal of dogwhelks increased the abundance of Semibalanus ba/anoides on the shore and as a result likelihood of algal escapes from grazing by Patella vulgate also increased. In addition the removal of Nucela increased the size and longevity of newly established Fucus vesiculosus clumps. In a factorial experiment the role of Patella vulgate and Nucella lapillus were examined simultaneously. Nuce/la was found to have an significant effect but less than that of Patella. The presence of Nucella did, however, mediate the effect of Patella. In addition Nucella was found to have a direct effect on the level of Semibalanus balanoides settlement in the field with the number of barnacles settling in cleared areas being reduced on areas which had been previously occupied by Nucella.

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42

Rogne, Eva. "Characterization of biofouling in membrane nanofiltration (NF) systems by molecular biological techniques." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14322.

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43

Xiao, Linlin [Verfasser], and Michael [Akademischer Betreuer] Grunze. "Influence of Surface Topography on Marine Biofouling / Linlin Xiao ; Betreuer: Michael Grunze." Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1177888726/34.

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44

Yang, Rong Ph D. Massachusetts Institute of Technology. "Prevention of biofouling in seawater desalination via initiated chemical vapor deposition (iCVD)." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91066.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014. Cataloged from PDF version of thesis. Includes bibliographical references. Biofouling, the undesirable settlement and growth of organisms, occurs immediately when a clean surface is immersed in natural seawater. It is a universal problem and the bottleneck for seawater desalination, which reduces both the yield and the quality of desalted water. Mitigation of fouling in a desalination operation is an on-going challenge due to the delicate nature of desalination membranes, the vast diversity of fouling organisms, and the additional cross-membrane transport resistance exerted by an extra layer of coating. This thesis focuses on benign interface engineering methods and ultra-thin zwitterionic coating synthesis to bridge this gap in surface modification strategies. The direct application of ultra-thin coatings on commercial membranes with intact membrane performance has been enabled by a room-temperature vapor treatment called initiated chemical vapor deposition (iCVD). Diffusion-limited reaction conditions have shown to significantly improve the surface concentration of the antifouling zwitterionic moieties, which is crucial to the fouling resistance of modified membranes. Robustness of the ultra-thin coating is enhanced through cross-linking and covalent attachment between the membrane and the film. The resulting durability of the antifouling coating and its resistance to oxidative reagents lead to an unprecedented synergistic effect that is critical to longterm fouling resistance, which provides unique insight into the adhesion of microbial foulant and promises to lower the price of freshwater in water-scarce countries, where desalination may serve as the only viable means to provide the water supply necessary to sustain agriculture, support personal consumption, and promote economic development. by Rong Yang. Ph. D.

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45

Meseguer, Hernández Eloy. "ESTUDIO DEL BIOFOULING ASOCIADO A CULTIVOS MARINOS "OFFSHORE" EN EL MEDITERRÁNEO ESPAÑOL." Doctoral thesis, Universitat Politècnica de València, 2017. http://hdl.handle.net/10251/85679.

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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

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46

Gittens, Jeanette Elizabeth. "Development of a functionalized coating for inhibition of marine corrosion and biofouling." Thesis, Sheffield Hallam University, 2011. http://shura.shu.ac.uk/19691/.

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The financial loss incurred by corrosion of metals in the marine environment has led to a need to develop effective, economic and environmentally friendly methods of protection. Traditional methods of counteracting the development of surface biofilms and biofouling within aqueous environments have involved implementing chemical biocides, often with a deleterious effect on non-target organisms. Sol gel coating technology offers a convenient route for immobilizing functional additives, such as inhibitors or, in the case of this study, biologically active microorganisms. Paenibacillus polymyxa biofilms inhibit the corrosion of metal substrates and this strain has the advantage of forming endospores can withstand the solvent and acid concentrations required in sol-gel formulation. Encapsulation of viable P. polymyxa endospores within the sol-gel matrix allowed germination on exposure to nutrients, when germinating endospores and vegetative cells were seen after fluorescence microscopy to be distributed throughout the coating. Laboratory electrochemical impedance tests were used to characterize the corrosion behaviour of the endospore-containing (biotic) sol-gel coating in comparison to an abiotic (no endospores) sol-gel only coating and one containing non-viable (killed) endospores. The technology enabled manipulation of the sol-gel formulation and the method of application to produce biotic sol-gel with enhanced corrosion inhibition properties on aluminium alloy. Field trials in a marine environment confirmed the corrosion protecting properties of the biotic coating and that the biotic coatings inhibited macroscopic biofouling for at least 29 weeks relative to the controls without encapsulated live endospores. Production of polymyxin by the encapsulated bacteria, which was proposed as a mechanism by which they inhibit MIC, was less than 1 mug per ml and below the threshold of detection by liquid chromatography mass spectrometry and antimicrobial bioassay. Microcosm experiments were used to study differences in the corrosion of abiotic and biotic coatings in the presence of a corrosion-causing sulphate-reducing bacterium. Scanning electrochemical microscopy was developed as a technique to study electrochemical processes on the coating surface and showed differences in the distribution of copper ions on the surface of abiotic and biotic coatings. The results of the experimental work in this thesis show the potential of encapsulating metabolically active bacterial cells within a sol-gel coating on metals for the control of marine corrosion and biofouling.

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Graziani, Lorenzo. "Nano-engineered brick surfaces for biofouling prevention: experimental results and analytical modelling." Doctoral thesis, Università Politecnica delle Marche, 2015. http://hdl.handle.net/11566/242914.

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Le facciate degli edifici sono inevitabilmente soggette al deterioramento causato dalla colonizzazione di microorganismi quali batteri, alghe, cianobatteri, funghi, licheni, etc. Oltre ai tradizionali metodi manutentivi, si stanno sviluppando rivestimenti innovativi con caratteristiche sfavorevoli allo sviluppo di macchie biologiche. In questa direzione, si sta sviluppando l’applicazione di nanotecnologie, in particolare nano-rivestimenti fotocatalitici. Il materiale più diffuso in questo settore è il biossido di titanio (TiO2) grazie alla sua non-tossicità, stabilità foto-chimica e basso costo. La ricerca ha l’obiettivo di studiare l’efficienza del TiO2 contro la bio-incrostazione algale su superfici in laterizio. La ricerca si concentra sull’abilità del TiO2 di limitare l’adesione delle cellule algali sotto l’azione dei raggi UV e in condizioni di luce visibile. Inoltre, vengono analizzate le relazioni tra il substrato e l’efficienza fotocatalitica, principalmente la rugosità e la porosità. L’attività sperimentale consiste nel sottoporre campioni di laterizio a cicli di bagnatura/asciugatura con una sospensione algale, in condizioni climatiche controllate. La bio-incostrazione è stata valutata nel tempo attraverso l’analisi digitale dell’immagine e misure colorimetriche. I risultati hanno evidenziato che il TiO2 ha l’abilità di inibire l’attecchimento delle cellule algali e in alcuni casi è in grado di arrestare del tutto la crescita dei microorganismi. L’efficienza è strettamente legata alla porosità e alla rugosità del substrato. Infine, l’addizione di nano-particelle di Ag e Cu alla soluzione di TiO2 non ha evidenziato miglioramenti significativi. La ricerca, partendo dai dati sperimentali, ha sviluppato un modello analitico basato sulla legge di Avrami. Il modello ha dimostrato un’ottima accuratezza nel riprodurre i risultati sperimentali e può essere potenzialmente applicato per la predizione del processo di bio-incrostazione su reali facciate in laterizio. Building façades, including brick façades, are inevitably subjected to the deterioration caused by the colonization of microorganisms. These microorganisms may be bacteria, algae, cyanobacteria, fungi, lichens and other. Algae and cyanobacteria are the first colonizers, which pave the way for the implantation and growth of other microorganisms systems. Beyond traditional intervention methods, innovative coatings with unfavourable intrinsic parameters to the development of biological stains are now developing. In this direction, the use of nanotechnology, especially the use of photocatalytic nanocoating, has recently raised. The most diffuse material in nanocoating applications is titanium dioxide (TiO2) because of its non-toxicity, photochemical stability and low cost. This research aims to study the efficiency of TiO2 toward algal biofouling when it is applied on brick elements. The research focuses on the ability of TiO2 to limit the adhesion of algal cells under both UV and visible radiation. Moreover, it studies the effect of substrata properties, mainly roughness and porosity, on the biocide effect of TiO2. Experimental activity, at the base of this research, consists to subject brick specimens to wet&dry cycles with algae suspension, under monitored climatic conditions. Biofouling was measured through time by digital image analysis and colorimetric measurements. Results show that TiO2 was able to inhibit the algal adhesion, in some cases, it is able to completely stop the growth of microorganisms. The efficiency of TiO2 is strictly related to physical properties of substrata like porosity and roughness. The addition of other noble metal (Ag, Cu) to the TiO2 solution seems to produce no significant improvement. This research extends experimental results to numerical modelling by applying the Avrami's law. The model shown to be adequate to reproduce laboratory tests and it has the potential to be applied for biofouling prediction on real building façades.

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48

Huang, Yi-Li. "Potential roles of bacterial quorum sensing and biofilm formation in the biofouling process /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?AMCE%202007%20HUANG.

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49

Thomé, Isabel [Verfasser], and Michael [Akademischer Betreuer] Grunze. "Influence of surface conditioning and morphology on biofouling / Isabel Thome ; Betreuer: Michael Grunze." Heidelberg : Universitätsbibliothek Heidelberg, 2013. http://d-nb.info/1177249596/34.

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50

Wong, Felicia Wong Yen Myan. "The influence of physical attributes of surface topographies in relation to marine biofouling." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/38837/.

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Abstract (sommario):

Solid surfaces that spend long periods of time in aquatic environments are susceptible to the accumulation of marine fouling organisms and this phenomenon is known as marine biofouling. This is a natural process which has significant impacts on marine industries. Research to develop new antifouling solutions focuses on the development of non-toxic solutions that can deter biofouling. A non-toxic antifouling approach that has gained interest in recent years is to modify the surface’s structure to disrupt organism settlement (Kirschner and Brennan 2012; Magin et al. 2010; Myan et al. 2013). Many studies determined that uniform arrays of single layered, micro-topographies are effective at deterring the initial settlement of fouling organisms. In contrast, most studies that tested uniform arrays of single layered, macro-topographies concluded that these topographies are not suitable for antifouling applications. Both single layered, micro-topographies and single layered, macro-topographies were determined to have limitations at mitigating biofouling. This resulted in the interest to develop hierarchical topographies. Hierarchical topographies are surfaces that consist of features that are varied in size and shape. It was suggested that the diverse nature of hierarchical topographies might be able to deter biofouling from a wider array of organisms. This research fabricated and tested a wide range of topographies (uniform, non-uniform, micro, macro, hierarchical, etc.) in a field study. A field study was preferred over lab experiments because results will reflect the antifouling efficacy of the surfaces in a marine environment. These results will indicate the topographies’ viability and future potential for industrial applications. Antifouling efficiency was evaluated by measuring fouling resistance (during the field test) and fouling removal (after the field test) of all topographies. Physical attributes (pattern geometry, pattern size, and surface roughness) of topographies were characterised with Scanning Electron Microscopy (SEM) and Laser Scanning Confocal Microscopy (LSCM). Statistical analysis was carried out to evaluate the significance of the topographies’ physical attributes on the antifouling efficiency of the topographies. The research hypotheses predicted that topography size, geometry and surface roughness will affect the topographies’ ability to resist biofouling. All patterned surfaces were predicted to have a higher resistance to biofouling in comparison to un-patterned control surfaces (i.e. smooth surfaces). The possibility that hierarchical topographies would have better fouling resistance properties than micro-topographies was considered as well. Hierarchical topographies and micro-topographies were also hypothesised to demonstrate better resistance to biofouling than macro-topographies. Topographies with straight ridges and hierarchical shapes were predicted to be more fouling resistant than sandpaper surfaces. Topographies with average roughness (RSa) that were less than 100µm were assumed to exhibit better antifouling efficacy in comparison to topographies with average roughness greater than 100µm. Results showed that pattern size and pattern geometry affects the antifouling efficiency of topographies. Unexpectedly, surface roughness did not show strong correlations with the fouling resistance of the topographies. With the exception of Sandpaper 50 and Sandpaper 1mm samples, all topographies were more fouling resistant than the control samples (i.e. smooth surfaces). Among the 16 topographies, sandpaper 1mm samples demonstrated the worst defence against biofouling. The mean total fouling coverage on these samples after 10 weeks of tests was 98.7%. Straight, single layer ridges demonstrated the best resistance to total fouling during the field test. Barnacle and polychaete settlement trends were affected by the size and geometry of single layer, single sized topographies. After 10 weeks, the mean total fouling coverage on these ridges was only 37.5%. The field test also showed that the topography with the best prolonged resistance to fouling was the 1mm straight ridges. The combination of structured surfaces and a low modulus material is likely to have contributed to the fouling removal properties of all topographies. Lastly, results from the field study also showed that hierarchical topographies do not necessarily have better antifouling properties than single layer, single sized topographies. The field study demonstrated that the physical attributes of topographies contributed to their antifouling efficiency. It has been suggested that the physical characteristics of topographies induces hydrodynamic variations that affects the surfaces’ antifouling properties. However, it is difficult to observe these changes in lab experiments or through field studies because these variations take place at a very small scale. Recent research has applied Computational Fluid Dynamics (CFD) to numerically simulate and analyse flow characteristics in the surrounding areas of antifouling topographies. As a continuation from the field study, the next study in this research applied CFD to analyse flow characteristics over several topographies that were tested in the field study. This was to determine if the settlement trends exhibited by organisms in the field study could have been affected by hydrodynamic variations that were induced by the presence of the topographies. The CFD analysis showed that rotational vortices formed between topography patterns. These vortices could have aided in the accumulation of biofouling material on all topographies during the field test. The analysis also showed that the topographies’ resistance to fouling could be attributed to high shear stress and strain rate zones at the peaks of the topographies. Comparisons between CFD and field test results indicate that higher stresses and strain rate zones around the topographies are likely to lead to a surface’s better resistance to marine biofouling. This is likely because high shear stress and strain rate zones could have disrupted organism motility and made the surface less conducive for settlement.

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