No description available.

This work addresses the problem of using seawater for cooling and the associated environmental problems caused by the usage and discharge of biocides. The discharged biocide and its byproducts are toxic to aquatic lives and must be decreased below certain discharge limits on load prior to discharge. The conventional approach has been to add biocide removal units as an end-of-pipe treatment. This work introduces an integrated approach to reducing biocide discharge throughout a set of coordinated strategies for inplant modifications and biocide removal. In particular, process integration tools are used to reduce heating and cooling requirements through the synthesis of a heat-exchange network. Heat integration among process of hot and cold streams is pursued to an economic extent by reconciling cost reduction in utilities versus any additional capital investment of the heat exchangers. Other strategies include maximization of the temperature range for seawater through the process and optimization of biocide dosage. This new approach has the advantage of providing cost savings while reducing the usage and discharge of biocides. A case study is used to illustrate the usefulness of this new approach and the accompanying design techniques.

Ce travail de thèse consiste à combattre le développement microbien des réservoirs de carburant aéronautiques dont le métabolisme entraine la production d’acides organiques susceptibles de corroder les parois métalliques des réservoirs. Des substances biocides sont habituellement utilisées pour éliminer les populations microbiennes. Ces substances peuvent être des composés organiques ou bien de manière plus courante du chrome (VI) sous forme de revêtement à la surface des parois afin de créer une couche passive et d’empêcher la corrosion chimique. Cependant, le chrome appartient à la catégorie des substances cancérogènes, mutagènes et reprotoxiques et se trouve maintenant soumis à restriction par la réglementation européenne Registration, Evaluation and Authorization of Chemicals (REACh). Pour remplacer les systèmes en place, le choix s’est porté sur la préparation de particules polymères pH-sensibles capables de libérer une molécule biocide en présence de microorganismes. De telles particules sont obtenues par copolymérisation par métathèse de cyclo-oléfines (ROMP) de norbornène avec un macromonomère linéaire de polyglycidol α-norbornenyl. Ce dernier permet d’une part la stabilisation des particules et d’autre part la multifonctionnalisation de l’objet par des molécules de biocide. Celles-ci sont introduites sur la chaîne de polyglycidol via un lien imine pH-sensible par substitution des fonctions hydroxyle par des entités dodécylamine. La libération du biocide à un pH inférieur à 7 a été validée ainsi que les capacités de ces particules à lutter contre des microorganismes tel que Hormoconis resinae souche identifiée comme se développant dans les réservoirs d’avions. Dans une dernière étape, les particules fonctionnalisées dodécylamine ont été incorporées dans un revêtement usuel en aéronautique et la capacité des particules à ne pas altérer la résistance du revêtement de base à des conditions de corrosion extrêmes a permis de vérifier leur applicabilité dans ce domaine. / The aim of this Thesis work was to address the issue of microbial contamination inside fuel tanks. Microorganisms induce the chemical corrosion of airplane tank walls due to their production of organic acids. Biocide compounds are typically used to inhibit these microorganisms, either in the form of organic small molecules, or most commonly as chromium-based coatings on the walls to hinder chemical corrosion. Organic biocides need to be replenished regularly, while chromium is a particularly dangerous compound targeted by the European Registration, Evaluation and Authorization of Chemicals (REACh) legislation due to its carcinogenic nature. A replacement approach selected for this project was the development of a smart system of multifunctional polymeric particles synthesized by dispersion ROMP, which can deliver a biocide following an acidic trigger due to the presence of microorganisms. The polymerization utilized a linear α-norbornenyl-polyglycidol macromonomer as a reactive surfactant. The hydroxyl-rich polyglycidol backbone of the macromonomer was beneficial for the conjugation of dodecylamine through a pH-sensitive imine bond and permitted the preparation of highly functionalized bioactive particles. A proof of concept for the pH sensitivity of the system was provided and the antifungal efficacy of the biocide-functionalized macromonomer and particles was verified. The particles were also integrated in a coating formulation to simulate their application on tank walls. The qualities of the original coating were preserved even after prolonged exposure to corrosive conditions, making this system viable for its foreseen application.

The microbial contamination of biomedical devices is a leading cause of hospital- acquired infection. A number of strategies aimed at developing device coatings that are refractory to microbial adhesion, colonisation and biofilm formation have been developed, but the problem remains. The incorporation of biocides into biomedical device surface coatings has shown promising results in preventing the establishment of infection. Current controversy over the possibility that extensive use of biocides could potentially lead to antimicrobial resistance has fuelled the search for new actives with good antimicrobial activity and low cytotoxicity, that maintain marked efficacy after prolonged use. This doctoral thesis aims to evaluate the antimicrobial potential of a novel peptide based on human apolipoprotein E receptor binding region (apoEdpL-W). The spectrum of antimicrobial activity and anti-biofilm efficacy of apoEdpL-W was compared to that of common biocides polyhexamethylene biguanide, triclosan, cetrimide and chlorhexidine. The potential to induce bacterial insusceptibility towards these agents after long-term sub-lethal level exposure was assessed. Initial examination against 18 test microorganisms, commonly associated with device infection, showed that apoEdpL-W displayed broad-range antimicrobial and anti-biofilm efficacy. ApoEdpL-W also maintained marked antibacterial activity after incorporation onto various biomaterial polymers, often used in device surface coatings. Alterations in bacterial susceptibility after prolonged exposure to apoEdpL-W, as well as to the other biocides, were often temporary and partially reverted once the bacteria had been grown in the absence of the antimicrobial agent. The adaption of Staphylococcus aureus to the presence of triclosan resulted in the formation of small colony variants (SVCs) with reduced triclosan susceptibility. Analysis of the physiological characteristics of the triclosan induced SCVs revealed the loss of virulence determinants and potentially reduced pathogenic capability, when compared to the parent strain. The biocompatibility index values of the test actives were determined by the parallel assessment of their antibacterial activity and in vitro cytotoxicity. ApoEdpL-W showed good antibacterial efficacy whilst remaining relatively less toxic to mammalian cells than triclosan or chlorhexidine. We studied the interactions of the test antimicrobials with a preformed phospholipid bilayer using the quartz crystal microbalance device and dual polarisation interferometry, to better understand potential mode of action. Analysis revealed that ApoEdpL-W and PHMB induced the highest level of bilayer disruption, of all the antimicrobials tested. These data suggest that apoEdpL-W demonstrates antibacterial activity; biocompatibility and long-term efficacy on a level that compares favourably to that of currently used biocides. The peptide demonstrates good antimicrobial efficacy when incorporated into a range of biomaterial polymers and shows the potential to be developed as an effective coating for the reduction of device associated infections.

Microbicides are used in consumer products worldwide to enhance their antibacterial potency in disinfection, for antisepsis or as preservatives. With the widespread use of these compounds, concerns have been expressed about their potential to select for reduced susceptibility. Whilst in vitro studies have reported the laboratory generation of bacterial insusceptibility for certain combinations of bacterium and microbicide, true microbicide resistance, which is defined as a change in susceptibility that is likely to affect the outcome of treatment, has not been frequently reported or observed in the environment. Importantly, risk assessments on the use of microbicides have been largely based on laboratory studies whereby pure cultures of bacteria are exposed to microbicides in aqueous solution. In use however, microbicides are formulated with various excipients and bacteria are exposed to them most commonly in complex biofilm communities. Work described in this doctoral thesis evaluates the effects of exposing bacteria to microbicides using exposure conditions intended to increase realism, with the ultimate aim of informing improved risk assessment methods that better reflect deployment of microbicides in the real-world, taking in to account the effects of formulation, growth in multi-species communities and potential reduced competiveness in adapted bacteria. Test bacteria (8 species, 7 genera) were repeatedly exposed to selected microbicides in aqueous solution and in various formulations reflecting their use in the domestic environment, such as general-purpose cleaners and laundry detergents. Minimum inhibitory concentrations, minimum bactericidal concentrations and minimum biofilm eradication concentrations were determined before and after 14 passages (P14) in the presence of microbicides (benzalkonium chloride (BAC), benzisothiazolinone (BIT), chlorhexidine (CHX), didecyldimethyl ammonium chloride (DDAC), Glydant (DMDM-hydantoin), polyhexamethylene biguanide (PHMB), thymol and triclosan) in aqueous solution or in formulation, using a previously validated gradient plating system. Bacteria were subsequently passaged a further 14 times in the absence of any antimicrobial agent to determine the stability of any adaptations (X14). In bacterial isolates that demonstrated marked changes in susceptibility, further phenotypic analysis was conducted to test for any induced alterations in antibiotic susceptibility, planktonic growth rate, biofilm formation, competitive fitness and relative pathogenicity. Exposure of microbial communities was carried out using a previously validated domestic drain biofilm simulator within constant depth film fermenters (CDFF). The CDFFs were exposed to increasing concentrations of BAC in aqueous solution or BAC formulation over a 32-week period. Changes in bacterial community composition and antimicrobial susceptibility distributions were assessed via replica plating onto selective and antimicrobial-containing agars as well as through the use of next generation sequencing technologies via the illumina Miseq platform and QIIME software. The formulation of microbicides significantly increased antibacterial and anti-biofilm potency and reduced the incidence and extent of the development of insusceptibility isolated bacteria (7 non-revertible bacteria in MBCs for microbicides, whilst 2 non-revertible bacteria in MBCs for formulations). In bacteria that develop marked changes in antimicrobial susceptibility after repeated exposure show changes to biofilm growth rates (10 increases and 6 decreases after microbicide exposure; 1 increase and 3 decreases after formulation exposure), as well as alterations in competitive fitness (6 decreases and 19 increases after microbicide exposure; whilst all exposed to formulation had decreased fitness) and virulence (9/13 decreased and 1/13 increased after microbicide exposure; 4/7 decreased and 2/7 increased after formulation exposure). In the multispecies microcosm system, long-term exposure to BAC or BAC formulation induced shifts in bacterial community dynamics and resulted in a decrease in BAC and various antibiotic susceptibilities (1 log10 reduction in the BAC system; 2.5 log10 reduction in the BAC formulation system of viable bacteria). Such shifts in community dynamics after antimicrobial treatment are theorised to be mainly due to clonal expansion of innately insusceptible bacteria (abundance of Achromobacter sp. increased by 39% in BAC system and 10% in BAC formulation system). Understanding the potential selectivity of microbicide-containing formulations is likely to better serve by testing formulations as well as actives in aqueous solutions. This highlights the need to conduct risk assessments of induced microbicide susceptibility changes using conditions that more accurately reflect their deployment.

In conjunction with horizontal drilling, hydraulic fracturing or fracking has enabled the recovery of natural gas from low permeable shale formations. In addition to water, these fracking fluids employ proppants and up to 38 different chemical additives to improve the efficiency of the process. One important class of additives used in hydraulic fracturing is biocides. When applied appropriately, they limit the growth of harmful microorganisms within the well, saving energy producers 4.5 billion dollars each year. However, biocides or their harmful daughter products may return to the surface in produced water, which must then be appropriately stored, treated and disposed of. Little is known about the effect of mineral-fluid interactions on the fate of the biocides employed in hydraulic fracturing. In this study, we employed laboratory experiments to determine changes in the persistence and products of these biocides under controlled environments. While many minerals are present in shale formations, pyrite, FeS2(s) is particularly interesting because of its prevalence and reactivity. The FeII groups on the face of pyrite may be oxidized to form FeIII phases. Both of these surfaces have been shown to be reactive with organic compounds. Chlorinated compounds undergo redox reactions at the pyrite-fluid interface, and sulfur-containing compounds undergo exceptionally strong sorption to both pristine and oxidized pyrite. This mineral may significantly influence the degradation of biocides in the Marcellus Shale. Thus, the overall goal of this study was to understand the effect of pyrite on biocide reactivity in hydraulic fracturing, focusing on the influence of pyrite on specific functional groups. The first specific objective was to demonstrate the effect of pyrite and pyrite reaction products on the degradation of the bromine-containing biocide, DBNPA. On the addition of pyrite to DBNPA, degradation rates of the doubly brominated compound were found to increase significantly. DBNPA is proposed to undergo redox reactions with the pyrite surface, accepting two-electrons from pyrite, and thus becoming reduced. The primary product is the monobrominated analogue of DBNPA, 2-monobromo-3-nitrilopropionamide (or MBNPA). The surface area-normalized first-order initial degradation rate constant was found to be 5.1 L.m-2day-1. It was also determined that the dissolution and oxidation products of pyrite, FeII, S2O32- and SO42- are unlikely to contribute to the reduction of the biocide. Taken together, the results illustrate that a surface reaction with pyrite has the ability to reduce the persistence of DBNPA, and as a consequence change the distribution of its reaction products. The second objective was to quantify the influence of water chemistry and interactions with pyrite on the degradation of the sulfur-containing biocide. Dazomet readily hydrolyzes in water due to the nucleophilic attack of hydroxide (OH-) anions. Thus the half-life of dazomet during the shut-in phase of hydraulic fracturing will decrease with increasing pH: 8.5 hours at pH 4.1 to 3.4 hours at pH 8.2.Dazomet degradation was rapidly accelerated upon exposure to the oxidized pyrite surface, reacting five times faster than hydrolysis in the absence of pyrite at a similar pH. The products measured were identical to those identified on hydrolysis (methyl isothiocyanate and formaldehyde) and no dissolved iron was detected in solutions. This suggests that the dithiocarbamate group in dazomet was able to chemisorb onto the oxidized pyrite surface, shifting the electron density of the molecule which resulted in accelerated hydrolysis of the biocide. The third objective explored the reactivity of various biocide functional groups due to the addition of pyrite. Several elimination mechanisms were identified, and tied to the reactivity of the specific functional group involved. The addition of pyrite led to accelerated degradation of dibromodicyanobutane. This is because the bromine (-Br) group is easily reduced. For methylene bis(thiocyanate), hydrolysis was a noteworthy elimination mechanism since the thiocyanate (-SCN) functionality is a good leaving group. Benzisothiazolinone and methyl isothiazolinone were stable at low pH due to the stabilizing donor-acceptor interactions between the organic biocides’ carbonyl (–C=O) groups and salts in the solution. This body of work has illustrated that pristine pyrite can undergo redox reactions with brominated biocides used in hydraulic fracturing, reducing their persistence and altering the product distribution. This will change the efficacy and the risks associated with the use of these biocides in shales containing pyrite, particularly at lower pH where organic compounds are more stable to hydrolysis. However, at higher pH hydrolysis becomes more important, and additional studies will need to be conducted to investigate the pyrite contribution under these conditions. Conversely, the FeIII surface groups on oxidized pyrite can catalyze the hydrolysis of dazomet and may do so for other labile, sulfur-containing biocides as well. Overall, this research has shown that the physicochemical properties (such as the acid dissociation constant and the standard reduction potential) that govern the environmental reactivity of a molecule can be used to anticipate its reactivity in hydraulic fracturing.

No description available.

La microbiologie est la science qui s'attache à l'étude des microorganismes et de leurs propriétés. Depuis ses débuts au XV II siècle, les méthodes développées par les microbiologistes ont permis de révéler un énorme potentiel de connaissances et d'applications. Dans les dernières décennies, les industriels ont vu un intérêt tout particulier dans ce domaine d'étude. Le besoin de prévenir les contaminations en inhibant le développement microbien, ou au contraire la volonté de l'optimiser pour profiter des capacités de transformations chimiques des microorganismes a fait naître une demande croissante de tests microbiologiques. Le faible rendement des méthodes traditionnelles ne permettant pas de satisfaire à cette demande, la recherche de nouvelles méthodes de test focalise les intérêts. Les outils fluidiques miniaturisés ont d'ores et déjà fait preuve de leur potentiel pour ce type d'application, bien que leur validation vis-à-vis des méthodes classiques manque souvent.Dans ce travail de thèse, nous avons développé des incubateurs miniaturisés et des méthodes de suivi de populations de microorganismes optimisés. L'objectif est d'aborder l'impact de la réduction d'échelle d'incubation sur la croissance par rapport aux dispositifs de culture traditionnel, pour ensuite aboutir à un outil haut-débit pour la caractérisation de biocides. / Microbiology is the part of science linked with the study of microorganisms and their properties. Since its beginnings in the XV IIth century, the methods developped by the microbiologists revealed a huge potential of knowledge and applications.In the last decades, industrials realized the interests of this study areaThe need to prevent contaminations by inhibiting microbial development, or on the contrary the will to improve it to enjoy the chemical transformations capacities of the microorganisms gave birth to an increasing demand for microbiological tests. The poor yield of traditionnal methods does not allow to satisfy this need, and the search for new test methods is thus focalizing interests. Miniaturized fluidic tools have already proven their potential for this kind of applications, and yet, their validation towards traditionnal methods often lacks.In this work, we aim at developping miniaturized cultivation techniques and optimized growth analysis methods, to study the scale reduction impact of incubator's size on growth, in order to end up with a high-throughput tool for biocide caracterization.

Les circuits de refroidissement des centrales nucléaires en bord de rivière sélectionnent par leur mode de fonctionnement des micro-organismes à caractère thermophile, parmi lesquels le micro-organisme pathogène, Legionella pneumophila. Pour lutter contre le développement de ce genre bactérien, un traitement de désinfection de l’eau des circuits de refroidissement à la monochloramine peut être employé. Pour participer à la maitrise des risques sanitaires et environnementaux liés à la modification physico-chimique et microbiologique de l’eau naturelle prélevée, EDF s’est engagé dans une démarche d’amélioration des connaissances sur l’écologie de Legionella pneumophila dans les circuits de refroidissement et des liens que cette espèce bactérienne entretient avec son environnement (physico-chimique et microbiologique) favorisant ou non sa prolifération. Ainsi, la diversité et la dynamique des Legionella pneumophila cultivables ont été déterminées dans les quatre centrales nucléaires en bord de Loire pendant un an et leurs liens avec leur environnement physico-chimique et microbiologique ont été étudiés. Cette étude a mis en évidence une forte diversité des sous-populations de Legionella pneumophila et une apparente dynamique qui semble être liée à l’évolution d’un nombre restreint de sous-populations. Les sous-populations de Legionella pneumophila semblent entretenir des relations souche-spécifiques avec les paramètres biotiques et présenter des sensibilités différentes aux variations physico-chimiques du milieu. La conception des circuits de refroidissement pourrait impacter la communauté de légionelles. L’utilisation de la monochloramine perturbe fortement l’écosystème mais ne sélectionne pas de populations tolérantes au biocide. / The cooling circuits of nuclear power plants, by their mode of operating, can select thermophilic microorganisms including the pathogenic organism Legionella pneumophila. To control the development of this species, a disinfection treatment of water cooling systems with monochloramine can be used. To participate in the management of health and environmental risks associated with the physico-chemical and microbiological modification of water collected from the river, EDF is committed to a process of increasing knowledge about the ecology of Legionella pneumophila in cooling circuits and its links with its environment (physical, chemical and microbiological) supporting or not their proliferation. Thus, diversity and dynamics of culturable Legionella pneumophila were determined in the four nuclear power plants along the Loire for a year and their links with physico-chemical and microbiological parameters were studied. This study revealed a high diversity of Legionella pneumophila subpopulations and their dynamic seems to be related to the evolution of a small number of subpopulations. Legionella subpopulations seem to maintain strain-specific relationships with biotic parameters and present different sensitivities to physico-chemical variations. The design of cooling circuits could impact the Legionella pneumophila community. The use of monochloramine severely disrupts the ecosystem but does not select biocide tolerant subpopulations.

Ce travail de thèse a dans un premier temps permis de mettre en évidence les différentes pratiques de traitement de toiture existantes en France. Après avoir sélectionné la pratique de traitement majoritaire (à savoir le traitement biocide), le protocole d'analyse de la molécule la plus répandue dans les différents produits : le benzalkonium (ou alkyldiméthylbenzylammonium) a été développé. Ce protocole a ensuite été appliqué pour évaluer les niveaux de concentration en biocide dans l'eau de ruissellement de toiture après un traitement. Une double approche a été mise en œuvre : "Suivi sur une durée d'un an des flux de benzalkonium dans les eaux de ruissellement de 12 bancs d'essais exposés en conditions naturelles", évaluation en condition de pluie simulée au laboratoire de différents paramètres (nature du matériau de couverture, dosage du produit et intensité de la pluie) sur les processus d'émission du benzalkonium. Enfin, l'ensemble des données acquises ont permis d'évaluer l'incidence sur la contamination des eaux de ruissellement de toiture après un traitement biocide, à une échelle locale et à l'échelle d'un petit bassin versant résidentiel. Le suivi de la contamination des eaux de ruissellement par bancs d'essais a permis de mettre en évidence une très forte contamination en benzalkonium dans les premiers millimètres de pluie (5 à 27 mg/L), très supérieures aux EC50 disponibles pour les organismes aquatiques (5,9 µg/L) et dépendante de la nature du matériau de toiture utilisé, les tuiles en terre cuite ayant émis moins de biocide que les tuiles en béton. La contamination diminue avec la succession des pluies, mais reste significative plusieurs mois après le traitement. Par ailleurs, l'étude au laboratoire a montré que l'état de surface des tuiles influence beaucoup le lessivage. Ainsi, les tuiles très imperméables en surface ont émis une quantité de benzalkonium proportionnelle à la masse épandue lors du traitement, alors que les tuiles sans traitement de surface ne sont pas sensibles au dosage du produit. A l'échelle locale, des précautions doivent être prise lors d'un traitement de toiture vis-à-vis de la collecte / utilisation des eaux de ruissellement. En effet, les très fortes concentrations en benzalkonium dans les premières pluies suivant le traitement peuvent avoir des impacts sur les végétaux arrosés, sur l'équilibre microbien de la cuve de récupération, voir des effets irritants sur l'homme. Une déconnexion minimale de 3 à 5 mois de la cuve permettrait de limiter les risques. Enfin, sur la base des résultats des bancs d'essais et d'un travail d'enquête sur l'étendue des pratiques de traitement, les concentrations et flux de benzalkonium susceptibles d'être émis dans les eaux pluviales d'un bassin versant résidentiel ont été modélisés. Les résultats mettent en évidence une contamination significative des eaux pluviales, liée essentiellement à la phase particulaire. La masse annuelle de benzalkonium exportée dans les eaux pluviales pourrait être de l'ordre de 0,85 kg / ha imperméabilisé / an / Firstly, this thesis listed the different roof treatment practices in France. Once the major treatment practice selected (biocidal treament), the analytical protocol of the most widely used molecule (benzalkonium or alkyldimethylbenzylammonium) was developed. This protocol has been followed to evaluate the biocide concentration levels in roof runoff after a treatment. A double approach was considered : - Follow up of the benzalkonium flux for one year in runoff using 12 bench tests exposed to natural conditions. - Evaluation of the influence of different parameters (material, product dosage and rain intensity) on benzalkonium emmission processes with simulated rains. Finally, all the data acquired allowed the evaluation of the incidence of biocidal treatments on roof runoff contamination at different scales ( local and residential watershed). The results of the bench tests showed a very high benzalkonium contamination during the millimetres of rain (5 to 27 mg/L), higher than the different EC50s of aquatic organisms ( 5.9 ùg/L). Furthermore, the results showed an influence of the tile material on the release of benzalkonium : clay tiles were less washed off than concrete tiles. The contamination decreased with successive rains, but remained significantly high several months after treatment. Moreover, laboratory studies showed a proportional release of benzalkonium from waterproofed tiles with respect to the biocidal mass spread. On the contrary, tiles without any surface treatment were not sensitive to the product's dosage. On a local scale, precautions have to be taken during treatment with respect to the harvest / reuse of the runoff. Indeed, high benzalkonium concentrations during the first rains may have a potential impact on watered plants, microbial equilibrium in the collection tank and irritating effects on human. A deconnection of the tank for at least three to five months will reduce the risks. Finally, based upon the bench tests results and a survey on roof treatment practices, the benzalkonium concentrations and fluxes were injected in a mathematical model on a watershed scale. The results showed a significant contamination linked to the particles. The annual mass of benzalkonium transferred to the rainwaters could reach 0.85kg / waterproofed ha / year