The effectiveness of reverse osmosis (RO) membrane systems may be compromised due to fouling, of which biofouling (excessive growth of biomass) is the most troublesome. Effective control of biofouling is essential to improve membrane performance and reduce operating costs. The periodic application of chemical cleaning agents is possibly the most widely practiced method of biofouling control in RO membranes. This research investigated advanced chemical cleaning strategies for biofouling control. The first part of this study concluded that short-term accelerated biofouling studies using lab-scale membrane fouling simulators (MFSs) are a representative and suitable approach for the prediction of long-term biofouling development in membrane systems. Thereon, the superior efficiency of urea as an alternative to conventional chemical cleaning agents was demonstrated (i) at lab-scale using MFSs, (ii) for full-scale industrial spiral-wound membranes and (iii) for multiple cleaning cycles during long-term operation. Periodic chemical cleaning with urea resulted in better restoration of membrane performance, higher biomass inactivation, enhanced biofilm solubilization and removal, disintegration of extracellular polymeric substances (EPS) particularly proteins, and a considerable reduction of key biofilm-forming bacteria. This research presented enhanced chemical cleaning strategies aiming to increase the removal of biofilms, reduce biomass accumulation and its impact on membrane performance, and delay fresh biofilm formation.

Biofouling represents the main problem in membrane filtration systems. Biofouling arises when the biomass growth negatively impacts the membrane performance parameters (i.e. flux decrease and feed channel pressure drop). Most of the available techniques for characterization of biofouling involve membrane autopsies, providing information ex-situ destructively at the end of the process. OCT, is non-invasive imaging technique, able to acquire scans in-situ and non-destructively. The objective of this study was to evaluate the suitability of OCT as in-situ and non-destructive tool to gain a better understanding of biofouling behavior in membrane filtration systems. The OCT was employed to study the fouling behavior in two different membrane configurations: (i) submerged flat sheet membrane and (ii) spacer filled channel. Through the on-line acquisition of OCT scans and the study of the biomass morphology, it was possible to relate the impact of the fouling on the membrane performance. The on-line monitoring of biofilm formation on a flat sheet membrane was conducted in a gravity-driven submerged membrane bioreactor (SMBR) for 43 d. Four different phases were observed linking the variations in permeate flux with changes in biofilm morphology. Furthermore, the biofilm morphology was used in computational fluid dynamics (CFD) simulation to better understand the role of biofilm structure on the filtration mechanisms. The time-resolved OCT analysis was employed to study the biofouling development at the early stage. Membrane coverage and average biofouling layer thickness were found to be linearly correlated with the permeate flux pattern. An integrated characterization methodology was employed to characterize the fouling on a flat sheet membrane, involving the use of OCT as first step followed by membrane autopsies, revealing the presence of a homogeneous layer on the surface. In a spacer filled channel a 3D OCT time series analysis of biomass development under representative conditions for a spiral-wound membrane element was performed. Biomass accumulation was stronger on the feed spacer during the early stage, impacting the feed channel pressure drop more than the permeate flux. OCT biofilm thickness map was presented as new tool to evaluate the biofouling development in membrane filtration systems through the use of a false color scale.

Lubricant-infused surfaces (LIS) are created by modifying chemical and physical properties of surfaces with aim of lowering surfaces energy where designed surface will possess liquid-repelling behaviors under low tilting angles. LIS has great potential to be applied on implantable devices due to it is stable anti-biofouling properties under fluidic environment. However, a few studies have reported that the existing research on implant surface uses complicated methods and high cost fabrication to create LIS on titanium implants. Furthermore, current limitation of LIS coatings for titanium implants lies in the lack of tissue integration and cell interaction. As a result, LIS prevents both bacteria and bone cells from adhering to the interface between implant and natural bone. This unselective blocking is problematic for titanium implants used in orthopaedic surgery when devices are required to possess tissue integration properties to facilitate long term fixation in the human body. The overall objective of this thesis is to apply LIS on titanium surfaces via a chemical modification technique and simultaneously integrate bio-functional features onto LIS to promote osteoblasts adhesion. In this project, chitosan and collagen were used to facilitate cell adhesion. To start with, three methods were used to immobilize chitosan on titanium to obtain the desired bio-functional LIS coatings: (1) LIS on top of (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) crosslinked chitosan; (2) LIS on dip-coated chitosan; (3) LIS generated from GPTMS and Trichloro(1H,1H,2H,2H-perfluorooctyl) silane (TPFS) mixed silanes modified titanium surface followed by chitosan functionalization. Among these modification techniques, method (3) showed optimal anti-biofouling and osseointegration properties. Since collagen is well known for increase of cell interactions, it was used via mixed silanes functionalization method. Finally, the properties were compared with chitosan coated surfaces. During tests, surface wettability was measured, anti-biofouling properties and osseointegration was examined with staphylococcus aureus and SAOS-2 cells, respectively. We found that chitosan modified surfaces using method (3) not only significantly increased cell adhesion in comparison with the other two modification methods, but also dramatically decreased bacterial adhesion compared to collagen coated LIS on titanium. Although collagen has better cell adhesion properties than chitosan, collagen coated surface significantly decreased antibiofouling properties. In conclusion, bio-functional lubricant-infused titanium surfaces created by chemical vapor deposition (CVD) method with mixed silanes is a feasible and straightforward method to immobilize biomaterials and stabilize the lubricant layer on titanium substrates. Chitosan coated LIS on titanium prevents bacterial adhesion and simultaneously promotes targeted cell binding. / Thesis / Master of Applied Science (MASc) / Biofouling is a major issue in implantable titanium devices such as coronary stents, plates and nails, and formation of biofilm on implants can lead to infection and failure of the device. Biofilms formed by bacterial adhesion could be resistant to antibiotics and can provoke a series of inflammatory response. Recent advances in anti-biofouling surface treatment has resulted in designing supper slippery lubricant-infused omniphobic surfaces which are inspired from the Nepenthes pitcher plant. Liquid which is tethered on the surface offers a stable liquid interface, repelling both aqueous and organic liquids meanwhile showing excellent bacteria repellency. Lubricant-infused surfaces (LIS) are resistant towards biofilm formation and produce a stable surface that prevent non-specific adhesion. As a result of this repellent properties, LIS also repels the adhesion of desired biomolecules and cells such as osteoblasts, bone cells and growth factors which are essential factors for bone recovery at the implant-bone interface. Our motivation in this thesis is to create a lubricant-infused coating on titanium surfaces that possesses both bio-functional and blocking features. We designed surfaces that decrease implant infection caused by non-specific adhesion and simultaneously promote targeted binding of biomolecules and cells that will increase osseointegration of the implant to enable long-term fixation.

Tout support immergé dans l’eau est rapidement colonisé par de nombreux organismes micro- et macroscopiques. Ce phénomène séquentiel et complexe appelé biofouling est à l’origine de nombreux préjudices économiques et écologiques, notamment dans le milieu marin. L’interdiction récente de certaines substances toxiques, utilisées comme biocides dans les revêtements antifouling des coques de bateaux notamment, a relancé l’intérêt de rechercher de nouvelles molécules antifouling respectueuses de l’environnement. L’objectif de cette thèse a été de développer et d’amorcer l’étude de la représentativité d’un bio-essai permettant d’évaluer le potentiel antifouling de molécules et de revêtements sur des « biofilms » mono et plurispécifiques in vitro en microplaques grâce à l’utilisation de fluorochromes. Le choix a été fait de se focaliser sur le biofilm primaire car il est envisagé que l’élimination ou la limitation de ce dernier réduisent le biofouling. Cinq souches de bactéries marines pionnières, isolées de la Rade de Toulon et en Bretagne, ont été utilisées afin de comparer l’efficacité anti-adhésion de molécules commerciales et naturelles. Deux dérivés de synthèse de substances naturelles marines (TFA E et Z) ont présenté une activité significative associée à une absence de toxicité sur bactéries, suggérant ainsi un mode d’action anti-adhésion spécifique. En outre, les différences de sensibilité entre souches ont confirmée l’importance de réaliser le bio-essai avec un panel diversifié de bactéries.Afin de voir si les données obtenues en laboratoire reflétaient ce qui se produit dans le milieu naturel, une comparaison entre les résultats du bio-essai en microplaque appliqué à six revêtements et les biofilms qui ont colonisés ces mêmes peintures immergées un mois dans la Rade de Toulon (analysés par cytométrie de flux, microscopie et PCR-DGGE), a été effectuée. Les analyses quantitatives ont suggéré une cohérence entre les deux approches même si l’absence de revêtement d’efficacité intermédiaire et le nombre de systèmes testés limite la portée de nos conclusions / Any surface immersed in water is rapidly colonized by a lot of micro-and macroscopic organisms. Sequential and complex phenomenon known as biofouling, lead to major economic and ecological damages, particularly in the marine environment. The recent ban of toxic substances used as biocides in antifouling coatings for ship hulls notably, has relaunched searching for new molecules antifouling environmentally friendly. The objective of this thesis was to develop and initiate the study of the representativeness of a bioassay allow to assess the potential of molecules and antifouling coatings on "biofilms" mono and multi-species microplate using of fluorochromes. It was decided to focus on the primary biofilm because it is possible that the elimination or limitation of the latter reduce biofouling. Five strains of marine bacteria pioneers, isolated from the Bay of Toulon and Brittany, were used to compare the effectiveness of a settlement of commercial and natural molecules. Two derivatives of natural substances Marine (TFA E and Z) showed significant activity associated with a lack of toxicity in bacteria, suggesting a specific anti-adhesion mechanism. In addition, differences in sensitivity between strains have confirmed the importance of making the bioassay with a various bacteria. To see if the data obtained in the laboratory showed what happens in the natural environment, a comparison between the results of the bioassay in microplate applied to six coatings and biofilms isolated on the same paint immersed for a month in the Bay of Toulon (analyzed by flow cytometry, microscopy and PCR-DGGE) was performed. Quantitative analysis suggested a correlation in between approaches although the absence of effectiency intermediate coating and the number of tested systems limit our conclusions

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.

Sistemas de membranas filtrantes, principalmente os de osmose reversa, estão sendo cada vez mais utilizados em diversos seguimentos de empresas (farmacêutica, tratamento de água, alimentícia e química), devido à diminuição do preço dos elementos filtrantes e da alta qualidade do produto obtido. O biofouling corresponde a um tipo de fouling inevitável, caracterizado pelo crescimento de microrganismos na superfície das membranas e liberação de EPS pelos mesmos; por isso, um melhor conhecimento sobre estas estruturas é necessário. O presente trabalho teve como objetivo caracterizar o biofouling em diferentes membranas de osmose reversa colmatadas de diferentes indústrias pela técnica da autópsia e comparar com resultados obtidos com biofilmes de cultura pura formados em membranas de osmose reversa; além de verificar a influência de biofilmes na deposição de sais e ação de compostos químicos utilizados na limpeza química de membranas nos mesmos. A autópsia dos elementos colmatados mostrou uma grande quantidade de células viáveis porém, com concentrações de carboidratos muito baixas; diferentemente do que ocorreu quando biofilmes de cultura pura isolados destas membranas foram analisados, apresentando correlações fortes entre quantidade de células viáveis e macromoléculas como proteínas e, principalmente, carboidratos. Com relação à influência dos biofilmes na deposição de sais, dois dos quatro biofilmes de cultura pura apresentaram incorporação de bário em sua estrutura (revelado por análises de fluorescência de raios X), esta incorporação, provavelmente, ocorreu por troca iônica e não pela deposição de sulfato de bário. Compostos como hidróxido de sódio (pH = 12) e ácido clorídrico (pH = 2) apresentaram bons resultados na diminuição de células viáveis porém, a recuperação dos microrganismos foi menor com a utilização do ácido. Os compostos EDTA e SDS não foram eficazes na diminuição de viáveis. / Systems of filter membranes, especially reverse osmosis, are being increasingly used in various segments of companies (pharmaceutical, water treatment, food and chemical industries) due to the decrease in the price of the filter elements and high quality of the product. The biofouling corresponds to a type of inevitable fouling characterized by growth of microorganisms on the surface of the membrane and release of EPS by them; so a better understanding of these structures is necessary. This study aimed to characterize the biofouling in different reverse osmosis membranes addressed from different industries by the technique of autopsy and compared with results obtained with pure culture biofilms in reverse osmosis membranes; and to verify the influence of biofilms in the deposition of salts and action of chemical compounds used in chemical cleaning of membranes in them. The autopsy of clogged elements showed a lot of viable cells but with very low carbohydrate concentrations; unlike what occurred when biofilms isolated pure culture of these membranes were analyzed, showing strong correlation between number of viable cells and macromolecules such as proteins and especially carbohydrates. Regarding the influence of biofilms in the deposition of salts, two of the four pure culture biofilms showed barium incorporation in its structure (revealed by fluorescence analysis X-ray), this merger probably occurred by ion exchange and not by deposition barium sulfate. Compounds such as sodium hydroxide (pH = 12) and hydrochloric acid (pH = 2) showed good results in the decrease of viable cells however, the recovery of microorganisms was lower with use of the acid. EDTA and SDS compounds were not effective in reducing viable.

Sistemas de membranas filtrantes, principalmente os de osmose reversa, estão sendo cada vez mais utilizados em diversos seguimentos de empresas (farmacêutica, tratamento de água, alimentícia e química), devido à diminuição do preço dos elementos filtrantes e da alta qualidade do produto obtido. O biofouling corresponde a um tipo de fouling inevitável, caracterizado pelo crescimento de microrganismos na superfície das membranas e liberação de EPS pelos mesmos; por isso, um melhor conhecimento sobre estas estruturas é necessário. O presente trabalho teve como objetivo caracterizar o biofouling em diferentes membranas de osmose reversa colmatadas de diferentes indústrias pela técnica da autópsia e comparar com resultados obtidos com biofilmes de cultura pura formados em membranas de osmose reversa; além de verificar a influência de biofilmes na deposição de sais e ação de compostos químicos utilizados na limpeza química de membranas nos mesmos. A autópsia dos elementos colmatados mostrou uma grande quantidade de células viáveis porém, com concentrações de carboidratos muito baixas; diferentemente do que ocorreu quando biofilmes de cultura pura isolados destas membranas foram analisados, apresentando correlações fortes entre quantidade de células viáveis e macromoléculas como proteínas e, principalmente, carboidratos. Com relação à influência dos biofilmes na deposição de sais, dois dos quatro biofilmes de cultura pura apresentaram incorporação de bário em sua estrutura (revelado por análises de fluorescência de raios X), esta incorporação, provavelmente, ocorreu por troca iônica e não pela deposição de sulfato de bário. Compostos como hidróxido de sódio (pH = 12) e ácido clorídrico (pH = 2) apresentaram bons resultados na diminuição de células viáveis porém, a recuperação dos microrganismos foi menor com a utilização do ácido. Os compostos EDTA e SDS não foram eficazes na diminuição de viáveis. / Systems of filter membranes, especially reverse osmosis, are being increasingly used in various segments of companies (pharmaceutical, water treatment, food and chemical industries) due to the decrease in the price of the filter elements and high quality of the product. The biofouling corresponds to a type of inevitable fouling characterized by growth of microorganisms on the surface of the membrane and release of EPS by them; so a better understanding of these structures is necessary. This study aimed to characterize the biofouling in different reverse osmosis membranes addressed from different industries by the technique of autopsy and compared with results obtained with pure culture biofilms in reverse osmosis membranes; and to verify the influence of biofilms in the deposition of salts and action of chemical compounds used in chemical cleaning of membranes in them. The autopsy of clogged elements showed a lot of viable cells but with very low carbohydrate concentrations; unlike what occurred when biofilms isolated pure culture of these membranes were analyzed, showing strong correlation between number of viable cells and macromolecules such as proteins and especially carbohydrates. Regarding the influence of biofilms in the deposition of salts, two of the four pure culture biofilms showed barium incorporation in its structure (revealed by fluorescence analysis X-ray), this merger probably occurred by ion exchange and not by deposition barium sulfate. Compounds such as sodium hydroxide (pH = 12) and hydrochloric acid (pH = 2) showed good results in the decrease of viable cells however, the recovery of microorganisms was lower with use of the acid. EDTA and SDS compounds were not effective in reducing viable.

Les coquilles d’huitres perlières (Pinctada margaritifera) en élevage sont abondamment colonisées par des peuplements épibiontes (ie biofouling). Ces communautés d’épibiontes représentent des contraintes de gestion coûteuses pour les perliculteurs (manutention, traitements). Leur rôle dans le fonctionnement des élevages, à la fois sur les espèces cultivées et sur l'environnement, est cependant encore très mal connu. La majorité des épibiontes sont des organismes filtreurs, potentiels compétiteurs des huitres perlières pour la ressource. Alors qu’une telle compétition pourrait compromettre la production, les interactions trophiques entre les huitres perlières et les épibiontes ont été très peu étudiées en Polynésie française. Plus largement, l’activité des épibiontes, ajoutée à celle des huitres perlières, pourrait également avoir des conséquences sur le fonctionnement de l’écosystème lagonaire. Au cours de ce travail de thèse, le biofouling a été étudié au travers d’une approche globale, considéré simultanément comme une contrainte pour la perliculture et comme un forçage biologique pour l’écosystème. Plusieurs expérimentations ont été réalisées dans 4 lagons de Polynésie française : Ahe, Mangareva, Rangiroa et Tahiti. Les communautés d’épibiontes ont été décrites, leur influence sur les fonctions physiologiques des huitres perlières (nutrition, croissance, reproduction) évaluée et finalement, leur rôle dans les interactions entre les élevages d’huitres perlières et l'environnement a été quantifié. Alors qu’aucun effet négatif du biofouling n’a été décelé sur la production des huitres perlières, son importance dans les processus à l’échelle de l’écosystème a été démontrée. / Reared pearl oysters support a host of epibiont communities (ie biofouling). Biofouling control results in additional costs for farmers (handling, treatment). However, the impact of epibionts on pearl oysters and on environment remains poorly known. Epibiont communities are dominated by filter-feeder organisms, which may compete for food with pearl oysters. Although such competition could alter the commercial production, very few studies have been conducted concerning the trophic interactions between pearl oysters and epibionts in French Polynesia. Otherwise, epibionts could reinforce the influence already induced by pearl oysters on the ecosystem. During this thesis, the problem of biofouling was addressed using a holistic approach, considering it as a constraint for pearl farming and a biological forcing for the ecosystem. Several experiments have been conducted in 4 lagoons of French Polynesia: Ahe, Mangareva, Rangiroa and Tahiti. Biofouling communities have been described, their impact on pearl oysters (feeding, growth, reproduction) assessed and finally we quantified their influence in the interactions between pearl oysters’ rearing and environment. While no negative impact of biofouling was observed on pearl oysters, its importance on the ecosystem processes have been demonstrated.

Anaerobic membrane bioreactor (AnMBR) serves as a more sustainable form of wastewater treatment. However, biofouling is particularly detrimental to the performanceof AnMBRs. This dissertation focuses on understanding more about the biofouling in nMBR, and to devise strategies to control or make use of these biofoulant layers. First, we aim to investigate the microbial community structure of sludge and biofilm from 13 different AnMBRs. Our findings indicate 20 sludge core genera and 12 biofilm core genera (occurrence ≥ 90% samples) could potentially account for the AnMBR performance. Sloan neutral model analysis indicates the anaerobic microbial consortium between sludge and biofilm is largely affected by stochastic dispersal and migration processes (i.e., neutral assembly), suggesting that the majority of these core genera are not selectively enriched for biofilm formation. Therefore, the second part of this dissertation aims to minimize the growth of the overall bacterial cells attached on the membranes. For this, membranes embedded with zinc oxide (ZnO) and copper oxide (CuO) nanoparticles were examined for their antifouling efficacies. Our findings indicate both CuO and ZnO nanoparticles embedded membranes could delay biofouling formation without significantly triggering the overall expression/abundance of antibiotic resistance genes (ARGs) and metal resistance genes (MRGs) in biofilm. Furthermore, CuO and ZnO nanoparticles could inhibit the expression of quorum sensing associated genes, resulting in lower quorum sensing signal molecules production. Despite the positive results demonstrated from this study as well as those from others, we recognize that no control strategies are likely to achieve total prevention of anaerobic biofouling. Therefore, the last part of this dissertation focuses on exploring the effects of different foulant layers on antibiotic-resistant bacteria (ARB) and ARGs removal. Our findings suggest both ARB and ARGs could be absorbed by membrane foulant. Transmembrane pressures and the foulant layer synergistically affected ARB removal, but the foulant layer is the main factor that contributed to ARG removal through adsorption. Overall, the collective findings could bring new insights to the anaerobic membrane biofouling phenomenon, and offer pragmatic approaches to minimize biofouling without compromising the post-AnMBR effluent quality.

Surfaces submerged in marine environments rapidly get colonized by marine organisms, a process known as biofouling. Fouling costs maritime industries billions of dollars annually. The most common methods of combating marine biofouling are toxin containing antifouling coatings which often have detrimental non-target environmental effects. These effects and proposed bans on harmful substances in antifouling coatings, mandates development of more environmentally friendly antifouling technologies. Of these, foul-release coatings, which minimize attachment and adhesion of fouling organisms (rather than killing them) are promising alternatives. Here I explored the utility of petroleum waxes as novel antifouling/foul-release coatings. I first investigated the responses of propagules (larvae or spores) of six common fouling organisms to wax coatings in the laboratory. A wide variation in the response of these different organisms, and in the different types of response (settlement, adhesion, etc.) by the same organism, was observed, but the most inhibitory coatings were those made from microcrystalline wax and silicone oil. However, in field trials in Sydney Harbour, paraffin waxes had the strongest antifouling performance, with activity up to one year (the trial duration). These waxes also had strong foul-release effects, with fouling that did attach mostly removed by a low pressure water jet. Composition of fouling communities on paraffin waxes differed significantly from other waxes or controls, with little or no hard fouling organisms (barnacles, bivalves) on paraffin. The mechanisms of antifouling and foul-release actions of paraffin waxes appear to be due to changes in surface properties. The surfaces of the paraffin waxes changed noticeably after 4 - 8 weeks immersion in the sea or in seawater aquaria. Antibiotic treatments showed that this change in surface appearance was due to biological (microbial) activity. Bacteria appear to remove the amorphous phase from the surface of the paraffin waxes, revealing an underlying crystalline phase, which is less affected by bacterial action. I suggest that these crystals form a microstructured ?bed of nails? of crystals of varying shapes and sizes which inhibit settlement and reduce adhesion strength of those organisms which do settle.