The growth of environmentally persistent biofilms in cooling towers causes several associated problems, including microbiologically-induced corrosion (MIC) and biofouling. Current chemical control methods are not only ineffective against biofilms and costly to procure, they also have downstream environmental impacts when released untreated, or incur additional treatment costs. Bacteriophages are alternative biofilm control agents that have the potential to be more effective, cheaper to produce and yet have a more benign effect on the environment. In this study, biofilms grown under conditions simulating seawater fed cooling towers were characterized and the differences in growth and community make-up across time and different substrates were assessed. An MIC associated bacterium common in cooling tower water, P. aeruginosa, was chosen. Seven bacteriophage strains found to be effective against the chosen bacterium were isolated from wastewater influent. The relative effectiveness of these strains was measured against P. aeruginosa across different salinities. Separate biofilms fed with P. aeruginosa enriched seawater were characterized and the effectiveness of the isolated strains, singly and in cocktails, against the enriched biofilms was measured.

Biofouling and biocorrosion are due to unwanted deposition of microorganisms on surfaces that are exposed to different types of water. This dissertation focuses on the application of innovative strategies to inhibit biofouling and biocorrosion. Specifically, the strategies examined in this dissertation, namely the use of bacteriophages and quorum quenchers, aim to minimize reliance on the conventional chemical cleaning agents and to reduce chemical-induced hazards on health, safety and environment. First, we analyzed the use of bacteriophages to remove biofoulants on ultrafiltration membrane used in seawater reverse osmosis pretreatment. Our findings revealed that bacteriophages were able to remain active against membrane-associated Pseudomonas aeruginosa at a broad range of temperature, pH and salinity. Bacteriophages were also shown to inhibit biofilm and to reduce transmembrane pressure increment, when applied alone or in combination with chemical agents. Second, this dissertation explores the use of quorum quenchers to inhibit biocorrosion in seawater environment. To do so, we first examined for the presence of quorum sensing system in sulfate reducing bacteria (SRB). Through transcriptomic analysis, we further demonstrate a strong correlation between quorum sensing, biofilm formation and biocorrosion. Therefore, the use of quorum sensing inhibitors was suggested to prevent biofilm formation and biocorrosion caused by SRB in seawater. Through findings from Chapter 2 and 3, we introduced the use of alternative biocidal agents to tackle biofouling and biocorrosion. Compared to quorum quenchers, bacteriophages showed better antibiofilm potential and easier applicability at larger scale. However, bacteriophages alone were insufficient to reduce biofilm formation as phage resistance was observed over long-term experiments. Hence in the last chapter, we further explored the use of bacteriophages to alleviate biofouling that occurred during wastewater treatment process, by combining their infection with UV irradiation. UV was used both for its biocidal effect and to trigger phage infection against bacteria. Our findings indicate that the combined treatment was able to remove mature biofoulants from the membrane. Overall, this dissertation demonstrates the use of bacteriophages and quorum quenchers against biofilm. These two approaches can serve to reduce the amount of chemicals used during cleaning, thus providing a more sustainable way of minimizing biofilm-associated problems.

Le but de ce travail était de mieux comprendre les mécanismes mis en jeu lors de la corrosion marine des structures en acier. Ces mécanismes impliquant l’influence de micro-organismes vivants, et notamment des bactéries sulfurogènes, l’étude a couplé des méthodes physico-chimiques à des techniques de microbiologie et de biologie moléculaire. Dans un premier temps, un système modèle de laboratoire a été élaboré afin d’étudier en détail les interactions entre les bactéries sulfato-réductrices (BSR) et le principal produit de la corrosion électrochimique des aciers en milieu marin, à savoir la rouille verte sulfatée RV(SO42-). Nous avons ainsi pu reproduire une partie des mécanismes mis en jeu, en montrant que les BSR pouvaient se développer en consommant les ions SO42- issus de la rouille verte et générer ainsi la mackinawite FeS observée sur sites. Dans un deuxième temps, l’évolution de la couche composite « rouille/biofilm » se formant sur acier en milieu marin a été suivie pour des temps courts d’immersion, allant de 1 semaine à deux mois. Le suivi simultané des données microbiologiques et physicochimiques a permis de montrer que l’influence des BSR ne se faisait pratiquement pas sentir à ce stade. Cependant, le développement préférentiel de bactéries associées au fer et au soufre au sein de la couche de rouille a pu être mis en évidence. Par ailleurs, très localement, le processus influencé par les BSR a été détecté. Enfin, une étude électrochimique en solutions désaérées simulant l’eau de mer a été confrontée aux résultats de l’analyse physico-chimique et microbiologique d’un coupon immergé 11 ans en milieu portuaire. L’ensemble des résultats montrent que RV(SO42-) se forme également lorsque des conditions anoxiques sont établies à la surface du métal. La formation de RV(SO42-) entre cependant en compétition avec celle de FeS et Fe3O4 suite aux modifications du milieu que peuvent engendrer les micro-organismes. A ces temps d’immersion long, l’influence des bactéries semblent néanmoins s’amoindrir, les micro-organismes tendant à s’éloigner des strates internes de la couche de rouille et donc du métal pour coloniser des zones externes plus riches en substances nutritives. / The aim of this study was to understand the mechanisms involved in marine corrosion of steel structures. These mechanisms are known to be influenced by micro-organisms, in particular by the sulphide-producing bacteria. It was then necessary to couple physico-chemical investigations with techniques of microbiology and molecular biology. In the first part of this work, a laboratory model was designed so as to study the interactions between sulphate-reducing bacteria (SRB) and the main product of the electrochemical corrosion process of iron in seawater, the sulphated green rust, GR(SO42-). We demonstrated that SRB could grow using only the SO42- ions coming from the green rust, thus generating mackinawite FeS as observed in real marine corrosion cases. In the second part, the evolution of the “rust/biofilm” layer that forms on steel in natural seawater was followed for short immersion times, from 1 week to 2 months. The simultaneous monitoring of microbiological and physico-chemical data showed that the influence of SRB was negligible at those early stages. However, the preferential growth of bacteria associated with iron and sulphur could be detected. Moreover, the process influenced by SRB could be detected locally in one case. Finally, in the third part of this work, an electrochemical study of carbon steel in deaerated seawater-like solutions was compared to the results of the physico-chemical and microbiological characterisation of a steel coupon left 11 years in a harbour site. All the results showed that GR(SO42-) was also forming when anoxic conditions were met at the steel surface. The formation of GR(SO42-) however competes with that of FeS and Fe3O4 due to the modifications of the environment induced by micro-organisms. For such long immersion periods, the influence of bacteria seems to decrease. The micro-organisms tend to move away from the inner parts of the rust layer, and then from the metal, to settle the outer parts where more nutrients are available.

L'industrie pétrolière et gazière subie d’importantes pertes économiques en raison de problèmes liés à la corrosion. Parmi ces problèmes, la corrosion induite par les micro-organismes (biocorrosion) fait toujours l’objet de recherche, le mécanisme le plus souvent évoqué et documenté étant lié aux bactéries sulfato-réductrices (BSR). Cependant certaines études ont montré que la biocorrosion pouvait se produire même en absence de BSR dans l'environnement corrosif ; le principal objectif de la thèse était donc de fournir un nouvel éclairage sur la corrosion anaérobie de l'acier au carbone en proposant des mécanismes différents de ceux impliquant les BSR. En premier lieu, l’influence d'une souche électro-active, G. sulfurreducens, sur la protection/corrosion de l'acier C1145 a été étudiée. Lorsque des espèces phosphate sont présentes dans le milieu, la bactérie favorise la formation d’une couche de Fer/Phosphate qui ensuite protège le matériau. En présence d’ammonium, les vitesses de corrosion sont plus élevées mais les bactéries réduisent la dissolution du métal. En deuxième partie, des échantillons de terrain issus des opérations de nettoyage des pipelines des systèmes d’injection ont été analysés d’un point de vue microbiologique et électrochimique. L’analyse moléculaire et l’identification de la communauté bactérienne montre la présence d'espèces sulfurogènes autre que les BSR. Ces bactéries peuvent stimuler la corrosion des métaux par la production d'acides organiques, de CO2 et de différentes espèces soufrées telles que H2S. De surcroît, il a été prouvé que le consortium contenu dans les échantillons de terrain accélérait la corrosion de l'acier au carbone, principalement par la production d'espèces sulfures. / The oil and gas industry is impacted by important economic losses due to corrosion problem. As part of this problem, microbially influenced corrosion (MIC) is still a subject of research. The most often evoked and well acknowledge MIC mechanism is linked to sulphate reducing bacteria (SRB). However, some studies have shown that MIC can occur even when SRB is not present in the corroding environment; in this framework, the main objective of the thesis is to provide new insights on corrosion of carbon steel caused by other mechanisms different to those described with SRB. First, the influence of an electroactive strain, G. sulfurreducens (an iron reducing bacteria, IRB) on the corrosion/protection of steel C1145 was studied. When phosphate species are present in the medium, bacteria promote the formation of an iron phosphate layer (vivianite) that afterwards protects the material. In presence of NH4+, corrosion rates are higher but bacteria decrease the dissolution of the material. In the second part, field samples from pigging operations performed in water injection pipelines were analysed from microbiological and electrochemical corrosion points of view. Molecular analysis and identification of the biofilm community show the presence of sulfidogenic species besides SRB. These bacteria can stimulate metal corrosion through production of organic acids, CO2 and different sulphur species such as H2S. Moreover, it was proved that the consortium contained in field samples accelerated corrosion of carbon steel mainly by production of sulphide species.

Cette thèse s'inscrit dans le cadre du projet européen BIOCOR ITN. Les matériaux métalliques habituellement utilisés dans les circuits de refroidissement de centrales électriques peuvent être affectés par la biocorrosion. L'objectif de ce travail était d'étudier l'influence de l'adsorption de biomolécules sur le comportement électrochimique et la composition chimique de surface de l'alliage 70Cu-30Ni, l'acier inoxydable 304L et le titane en milieu marin. Les interactions entre l'albumine de sérum bovin (BSA), et la surface de ces matériaux ont été étudiées. Ensuite, l'effet des substances polymériques extracellulaires (EPS) (étroitement liées -TB- et faiblement liées -LB- à la surface cellulaire) sur les couches d'oxydes a été évalué. Des mesures électrochimiques (Ecorr vs temps d'immersion, courbes de polarisation et EIS) ont été combinées à des analyses de surface (XPS et ToF-SIMS). En comparaison de l'alliage 70Cu-30Ni en eau de mer artificielle (ASW) statique sans biomolécules, pour lequel une couche duplex épaisse est montrée, la présence de biomolécules conduit à une couche mixte d'oxydes d'épaisseur plus faible. Un modèle est proposé pour analyser les données d'impédance obtenues à Ecorr. Un ralentissement de la réaction anodique par les biomolécules a été montré avec un effet d'inhibition de la corrosion par les LB EPS, dans une moindre mesure par la BSA et aucun effet néfaste en présence de TB EPS. L'effet des TB EPS et de la BSA sur la passivation du Ti dans ASW et de l'acier inoxydable 304L dans une solution sans chlorure a été étudié. Pour les deux matériaux, les couches d'oxydes sont plus protectrices avec la BSA et moins protectrices avec les TB EPS. / This thesis was carried out in the frame of the BIOCOR ITN European project. Metallic materials commonly used in cooling systems of power plants may be affected by biocorrosion. The objective of this work was to study the influence of biomolecules adsorption on the electrochemical behaviour and the surface chemical composition of 70Cu-30Ni alloy, 304L stainless steel and titanium in seawater environments. The interactions between a model protein, the bovine serum albumin (BSA), and the surface of these materials were investigated. After, the influence of tightly bound (TB) and loosely bound (LB) extracellular polymeric substances (EPS) on the oxide layers was evaluated. For that purpose, electrochemical measurements (Ecorr vs time, polarization curves and EIS) were combined to surface analysis (XPS and ToF-SIMS). Comparing to the 70Cu-30Ni alloy in static artificial seawater (ASW) without biomolecules, for which a thick duplex oxide layer is shown, the presence of BSA, TB EPS and LB EPS leads to a mixed oxide layer with a lower thickness. A model is proposed to analyse impedance data obtained at Ecorr. The results show a slow-down of the anodic reaction in the presence of biomolecules with a corrosion inhibition effect by LB EPS, to a lesser extent by BSA and no detrimental effect with TB EPS. On the other hand, the effect of TB EPS and BSA on the passivation behaviour of Ti in ASW and of 304L stainless steel in chloride-free solution was studied. From EIS data, resistivity profiles within oxide films can be plotted. For both materials, oxide layers are more protective with BSA and less protective with TB EPS.

Cette thèse, réalisée en étroite collaboration avec le partenaire industriel RSE S.p.A (Italie), s’inscrit dans le cadre du projet européen BIOCOR ITN. Les alliages de cuivre habituellement utilisés dans les circuits de refroidissement de centrales électriques peuvent être affectés par la biocorrosion induite par la formation d’un biofilm. L’objectif de ce travail était d’étudier the comportement à la corrosion de l’alliage 70Cu-30Ni et d’un laiton contenant 2% d’aluminium en milieu marin, dans des conditions industrielles réelles (expériences sur le terrain) et en laboratoire. L’influence de différents paramètres, tels que la solution (eau de mer naturelle filtrée (FNSW) vs eau de mer artificielle (ASW)), la concentration en biomolécules (biomolécules naturellement présentes dans l’eau de mer vs une protéine modèle, l’albumine de sérum bovin (BSA)), l’hydrodynamique (conditions statiques, sous circulation et agitation, électrode à anneau tournant) et le pH (8,0 ; 6,0 et 3,7), a été évaluée. Sur le terrain, le comportement global à la corrosion et les traitements antifouling ont été suivis en utilisant des techniques électrochimiques (potentiel de corrosion Ecorr vs temps, LPR), gravimétriques (pertes de masse) et génétiques. En laboratoire, des mesures électrochimiques (Ecorr vs temps, courbes de polarisation, spectroscopie d’impédance électrochimique), réalisées pendant les toutes premières étapes de formation des couches d’oxydes (1 h d’immersion), ont été combinées à des analyses de surface par XPS et ToF-SIMS. A partir des expériences sur le terrain, l’analyse microbiologique et moléculaire des biofilms formés sur les deux alliages de cuivre dans l’eau de mer naturelle montre la présence des espèces bactériennes Marinobacter, Alteromonas et Pseudomonas. In the case of Al brass, the single experimental loop illustrates both anodic charge transfer and anodic mass transport. A partir des expériences en laboratoire, des modèles sont proposés pour analyser les données d’impédance obtenues à Ecorr. Dans le cas de 70Cu-30Ni, la boucle HF illustre principalement le transfert de charge anodique (diamètre égal à Rta) ; alors que la boucle BF est liée au transport de matière anodique et au blocage partiel de la surface par CuCl. Dans le cas du laiton, la seule boucle expérimentale illustre à la fois le transfert de charge anodique et le transport de matière anodique. Le comportement électrochimique et la composition chimique de surface de l’alliage 70Cu-30Ni sont similaires dans ASW et dans FNSW statiques, du fait de la faible concentration en biomolécules dans FNSW. En comparaison de l’alliage 70Cu-30Ni dans ASW statique sans biomolécules, pour lequel une couche duplex épaisse (couche externe de Cu2O redéposé et couche interne de nickel oxydé) est montrée, la présence de BSA conduit à une couche mixte d’oxydes de Cu et de Ni d’épaisseur plus faible ; les résultats montrent aussi un ralentissement de la réaction anodique et un faible effet d’inhibition de la corrosion en présence de BSA. Sous circulation et agitation, une couche mixte d’oxydes de Cu et de Ni, de très faible épaisseur, est obtenue. Pour les deux alliages dans FNSW, le courant de corrosion icorr estimé à partir de Rta est indépendant de la vitesse de rotation de l’électrode tournante, du fait de la compensation des effets du potentiel et du transport de matière. Pour 70Cu-30Ni dans FNSW statique, la réaction anodique est ralentie à pH acide (effet cinétique). Pour le laiton, un effet d’inhibition de la corrosion est montré à pH acide, et plus le pH est acide, plus la réaction anodique est lente. Pour 70Cu-30Ni, l’épaisseur de la couche d'oxyde augmente avec la diminution du pH, dans le cas du laiton il est indépendante du pH. La composition chimique de la couche d'oxyde semble avoir un effet sur la quantité de protéines adsorbées et l'épaisseur équivalente calculée de la couche organique est très faible (quelques Å pour 70Cu-30Ni et 1 Å pour laiton). / This thesis was carried out in the frame of the BIOCOR ITN European project, in close collaboration with the industrial partner RSE S.p.A. (Italy). Copper alloys commonly used in cooling systems of power plants may be affected by biocorrosion induced by biofilm formation. The main objective of this work was to study the corrosion behavior of 70Cu-30Ni alloy and aluminum brass in seawater environments, under real industrial conditions (field experiments) and in laboratory. The influence of different parameters, such as the solution (filtered natural seawater (FNSW) vs artificial seawater (ASW)), the concentration of biomolecules (biomolecules naturally present in seawater vs a model protein, the bovine serum albumin (BSA)), hydrodynamics (static conditions, under flow and stirring, rotating ring electrode (RRE)) and pH (8.0, 6.0 and 3.7), was evaluated. In field, the overall corrosion behavior and antifouling treatments were monitored using electrochemical (corrosion potential Ecorr vs time, LPR), gravimetric (weight losses) and genetic techniques. In lab, electrochemical measurements (Ecorr vs time, polarization curves, EIS), performed during the very first steps of oxide layers formation (1 h immersion time), were combined to surface analysis by XPS and ToF-SIMS. From field experiments, microbiological and molecular analysis of biofilms formed on both copper alloys in natural seawater indicates the presence of Marinobacter, Alteromonas and Pseudomonas bacterial species. From lab experiments, models are proposed to analyze impedance data obtained at Ecorr. In the case of 70Cu-30Ni, the HF loop illustrates mainly the anodic charge transfer (diameter equal to Rta); whereas the LF loop is related to the anodic mass transport and partial blocking effect by CuCl. In the case of Al brass, the single experimental loop illustrates both anodic charge transfer and anodic mass transport. Similar electrochemical behavior and surface chemical composition of 70Cu-30Ni alloy are obtained in static ASW and FNSW, due to the low biomolecule concentration in FNSW. Compared to 70Cu-30Ni in static ASW without biomolecules, for which a thick duplex oxide layer (outer redeposited Cu2O layer and inner oxidized nickel layer) is shown, the presence of BSA leads to a mixed Cu and Ni oxide layer with a lower thickness; the results also show a slow-down of the anodic reaction and a small corrosion inhibition effect in the presence of BSA. Under flow and stirring, a very thin mixed Cu and Ni oxide layer is obtained. For both alloys in FNSW, the corrosion current icorr estimated from Rta is independent of the rotation speed of the RRE, due to compensated potential and mass transport effects. For 70Cu-30Ni in static FNSW, the anodic reaction is slown down at acidic pH (kinetic effect). For Al brass, there is a corrosion inhibition effect at acidic pH, and the more acidic the pH, the slower the anodic reaction. In the case of 70Cu-30Ni alloy, the oxide layer thickness increases with decreasing pH, whereas for Al brass it is independent of the pH. The chemical composition of the oxide layer seems to have an effect on the amount of adsorbed proteins and the calculated organic layer equivalent thickness is very low (few Å for 70Cu-30Ni and 1 Å for Al brass).

Magnesium (Mg) and its alloys provide numerous unique benefits as potential resorptive biomaterials and present the very real possibility of replacing current metallic implant materials in a variety of roles. However, considerable research remains before Mg alloys may be accurately screened and used in vivo. Most critically, a more comprehensive understanding of the corrosion of Mg alloys in vitro is needed. This research program critically examined the types of in vitro experiments that may be performed on Mg alloys, investigated the numerous variables that affect Mg biodegradation when undertaking these experiments, explored the electrochemical performance of several biocompatible Mg alloys, and developed a novel process for producing ordered Mg structures. The benefits and drawbacks of a range of in vitro tests were first investigated. The key strengths and weaknesses of each test were identified and recommendations provided for their respective use in the quest to determine Mg alloy biodegradation. The most common variables applicable to all in vitro experiments were then explored in detail, and their effect on the biocorrosion of a number of Mg alloys was determined. Recommendations were then made for the appropriate control of the different experimental variables based on these findings. For the first time, the mechanistic control of Mg biodegradation by the microstructure of biocompatible alloys has been examined. This allows for greater understanding of the reasons for varied corrosion of alloys in bio-electrolytes, and is a step towards the effective design of Mg alloys for different bio-applications. A novel method to produce ordered Mg structures was developed, with relevant processing parameters investigated in light of their effect on biocorrosion and mechanical performance. Overall, the results and findings from this research further our understanding of the potential of Mg alloys as suitable biomaterials, and advance our knowledge of how to proceed towards the goal of using such alloys for biological applications.

Le pont du Larivot, situé à l’embouchure de la rivière Cayenne et de l’océan Atlantique, est une artère routière indispensable au département amazonien de GuyaneFrançaise. Construit en acier au carbone, il a été fermé en 2009 pour cause de rupture d’une pile par corrosion. La corrosion influencée par les micro-organismes (CIM) estun processus naturel largement étudié dans des milieux tempérés soumis aux marées. L’objectif du travail réalisé ici est d’identifier ses marqueurs dans le cas d’un ouvraged’art en milieu amazonien.Des expériences sur site ont été réalisées sur 30 jours, avec un suivi des phénomènes de corrosion par analyses chimiques, électrochimiques, de surface, et biologiques surdifférents niveaux de marée. Elles montrent que le niveau basse mer (correspondant au niveau du fleuve lorsque la mer est au plus bas) présente les vitesses de corrosionles plus importantes (environ 0, 8 mm.an−1). Ces vitesses, une résistance à la corrosion faible, des micro-organismes fortement présents avec une forte concentration enéléments nutritifs (et particulièrement les nitrates) sont les marqueurs d’un phénomène d’ALWC (accelarated low water corrosion). Des essais effectués en conditions stérilesont confirmés la présence de CIM dans le milieu étudié.Une attention particulière a été portée sur le niveau basse mer avec une étude dynamique de la corrosion sur 50 jours. Ainsi, il a été montré que les phénomènes de surfacesont constants (dépôts de même épaisseur, diffusions de Warbrug identiques), mais avec des vitesses déterminées par courbes de polarisation augmentant linéairement (d’équation vcorr = 0, 004t + 0, 091). La présence dès 10 jours d’oxydes et d’hydroxydes de fer et, dès 30 jours, d’oxydes de manganèse et de sulfure de fer a également été mise en évidence.L’étude du bioflim corrosif montre une modification de la composition bactérienne au cours du temps avec un changement des β- vers les α-protéobactéries. Contrairement aux attentes, les procaryotes sulfato-réducteurs PSR (principalement des δ-protéobacteries) sont pratiquement absents du consortium corrosif. En revanche, des sulfato-oxydateurs sont prépondérants, et particulièrement Rheineimera aquamaris, dont le potentiel corrosif a été prouvé pour la première fois en culture pure.Ainsi, la présence de bactéries aérobies (les sulfato-oxydatrices), l’absence de bactéries anaérobies (PSR) et l’augmentation constante des vitesses montrent qu’après 50 jours le processus de corrosion se situe encore dans une des deux premières phases du modèle de Melcher. Pour compléter cette première étude dans un estuaire amazonien, des expériences à plus long terme doivent donc être réalisées en portant une attention sur la zone de marnage. / The Larivot Bridge, located at the mouth of the Cayenne River and the Atlantic Ocean, is a vital road artery of the Amazonian department of French Guiana. Built incarbon steel, it was closed in 2009 for breach of a pile due to corrosion. Corrosion influenced by microorganisms (MIC) is a natural process widely studied in temperatetidal environments. The objective of the work here is to identify markers in the case of a structure in the Amazonian environment.Experiments were carried out in situ for 30 days, with a follow-up of corrosion by chemical, electrochemical and biological analyses at the low water level. They showthat the low water level (corresponding to the level of the river when the tide is at its lowest) display the faster corrosion (about 0.8 mm.an-1). These rate, the low corrosionresistance, the high microorganisms presence with a high concentration of nutrients (especially the nitrate) are markers of a phenomenon of ALWC (accelarated low watercorrosion). Tests performed under sterile conditions have confirmed the presence of MIC in the medium studied.Particular attention was paid to the low water level with a dynamic study of corrosion on 50 days. Thus, it has been shown that surface phenomena are constant (samethickness of deposit, Warbrug diffusions identical), but with rates determined by polarization curves increasing linearly (equation of vcorr = 0.004t + 0.091). The presence at10 days of iron oxides and hydroxides and from 30 days, oxides of manganese and iron sulfide was also highlighted.The study of the corrosive bioflim shows a change in the bacterial composition over time with a change of β- to α-protéobactéries. Contrary to expectation, the sulfatereducingprokaryotes SRP (mostly δ-protéobacteries) are practically absent in the corrosive consortium. Instead, sulfate-oxidiser are paramount, especially Rheineimera Aquamaris,the corrosive potential has been proven for the first time in pure culture.Thus, the presence of aerobic bacteria (sulfate-oxydatrices), the lack of anaerobic bacteria (SRP) and the constant increase in speeds show that after 50 days the corrosionprocess is still located in one of the first two phases Melcher model. To complete this first study in the Amazon estuary, in the longer term experiments must be performedpaying attention to the tidal zone.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-04-01T12:36:05Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) MINHA DISSERTAÇÃO TODA CORRIGIDA PARA ENTREGAR FINALMENTE.pdf: 4033631 bytes, checksum: 08588f757c83774b5bae906b82926ffe (MD5) / Made available in DSpace on 2016-04-01T12:36:05Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) MINHA DISSERTAÇÃO TODA CORRIGIDA PARA ENTREGAR FINALMENTE.pdf: 4033631 bytes, checksum: 08588f757c83774b5bae906b82926ffe (MD5) Previous issue date: 2015-08-18 / CAPEs / O aço é um dos materiais mais comuns utilizados na construção de sistemas de armazenamento e de distribuição de derivados de petróleo. O contato direto entre a superfície metálica e um combustível contaminado com água pode proporcionar condições necessárias para o desenvolvimento de micro-organismos, os quais podem alterar a interface metal/meio, ou reagir diretamente com a superfície do metal, colaborando para sua deterioração química. O uso do óleo Diesel S10 foi estabelecido no mercado em 2013, com o objetivo de disponibilizar combustíveis alternativos que contribuíssem para a redução da emissão de poluentes dos veículos automotores, por possuir baixo teor de enxofre (10ppm). Sendo assim, tem-se a necessidade de desenvolver estudos sobre a contaminação microbiana nestes combustíveis para obter informações quanto à corrosão nos sistemas de armazenamento da indústria do petróleo. O presente trabalho teve como objetivo avaliar o processo de corrosão e biocorrosão do aço carbono ASTM A283, quando exposto ao sistema bifásico óleo Diesel S10/água doce, em condições estáticas, nas proporções de 1:1. Na água doce foram avaliados os parâmetros relacionados ao processo de corrosão e, analisou-se o efeito da biodegradação em diesel, devido ao sinergismo microbiano. Foram realizadas as caracterizações físico-químicas do diesel e da água, além da quantificação dos micro-organismos sésseis e planctônicos nos fluidos estudados, no biofilme e no resíduo depositado no fundo do reator, nos tempos de 0, 30, 60 e 90 dias. A avaliação do processo de corrosão foi realizada por ensaios de perda de massa e por análise da superfície através de Microscopia Ótica (MO), Microscopia Eletrônica de Varredura (MEV) e Espectroscopia de Energia Dispersiva (EDS), análises de Topografia e Rugosidade e Difração de Raio-X (DRX). Os resultados obtidos indicaram que houve corrosão alveolar em algumas regiões dos cupons. A corrosão bacteriana se concentrou principalmente nas superfícies que se encontravam imediatamente abaixo da interface diesel/água, onde houve a formação de produtos de corrosão e a aderência de biofilme. A corrosão localizada foi observada nas áreas imersas em óleo Diesel S10. Através da perda de massa, obteve-se a taxa de corrosão, classificada moderada para os cupons submetidos ao sistema bifásico, e classificada baixa para os cupons imersos em óleo diesel puro. As caracterizações da água mostraram que a composição original do meio foi alterada, devido ao comportamento do processo de corrosão. Não foi detectada atividade microbiana no diesel, que se manteve dentro das especificações ao longo de 90 dias. / The steel is one of the most common materials used in the construction of storage systems and distribution of petroleum products. The direct contact between the metal surface and a fuel contaminated with water can provide necessary conditions for the development of microorganisms, which can change the metal interface/middle, or react directly with the metal surface, contributing to their deterioration. The use of Diesel fuel S10 was established in the market in 2013, with the objective of providing alternative fuels that contribute to the reduction of the emission of pollutants from motor vehicles, it has low sulphur content (10ppm). Therefore, there is a need to develop studies on microbial contamination in these fuels for to get information about storage systems corrosion of oil industry. The present work had as objective to evaluate the corrosion process and biocorrosion of carbon steel ASTM A283, when exposed to the two-phase system Diesel S10/fresh water, under static conditions, in the proportions of 1:1. In fresh water were evaluated the parameters related to the corrosion process and examined the effect of biodegradation on diesel, due to microbial synergism. The physical and chemical characterization of diesel and water, in addition to the quantification of sessile and planktonic microorganisms in fluids studied, in the biofilm and in the residue deposited at the bottom of the reactor, in the time of 0, 30, 60 and 90 days were performed. The evaluation of the corrosion process was conducted out by mass loss and tests for surface analysis by optical microscopy, scanning electron microscopy (SEM) and Energy Dispersive spectroscopy (EDS), Topography and Roughness analyses and x-ray Diffraction (DRX). The results indicated that there was alveolate corrosion in some regions of the coupons. Bacterial corrosion focused mainly on the surfaces that were immediately below the diesel/water interface, where the formation of products of corrosion and biofilm adhesion. Localized corrosion was observed in the areas immersed in Diesel S10. Through the loss of mass, the corrosion rate was classified moderate for the coupons submitted to the two-phase system, and classified low to the coupons immersed in pure diesel oil. The characterizations of the water showed that the original composition of the medium has changed, due to the behavior of corrosion process. Microbial activity was not detected in the diesel, which is maintained within specifications throughout 90 days.

Desulfovibrio alaskensis G20 and other sulfate-reducing bacteria cause significant damage to metal pipelines and other infrastructure through a metabolic pathway that releases toxic hydrogen sulfide into their surroundings. The biocorrosion that results from the release of hydrogen sulfide creates significant economic burden, and can pose health risks for those exposed to this chemical. They are commonly present in the form of biofilms, an extracellular matrix composed of bacterial cells, polysaccharides, proteins, nucleic acids, and other materials. These biofilms are difficult to remove, and they provide protection to the bacteria within from anti-bacterial treatments. Desulfovibrio alaskensis G20 is a strain derived from a wild-type bacterium collected from an oil well corrosion site and is a model organism for understanding biofilm formation of sulfate-reducing bacteria and how these biofilms can be prevented or inhibited by techniques such as cerium oxide nanoparticle coating. To this end, samples of Desulfovibrio alaskensis G20 were grown anaerobically in 24-well and 96-well plates, and the resultant biofilm growth was measured through spectrophotometry. Several different environmental parameters were tested, including temperature, electron donor molecules, basal and enriched growth media, and oxidative stress, revealing several affinities for production of biofilm growth.