Search

Invasive non-native species are a major threat to global biodiversity. For at least 15 million years coastal Antarctica has been poorly connected to nearby temperate ecosystems due to physical and physiological barriers. Yet, Antarctica is experiencing significant environmental change and becoming increasingly exposed to ship-borne human activity that crosses the physical barriers. These factors may facilitate the establishment of non-native marine species. This doctoral research adds insight into the risk of non-native marine species being transported to Antarctica via ships' hulls and internal seawater systems, with particular focus on pathways of introduction and species found within those pathways. To begin my research, I assessed the current knowledge of non-native marine species in the Antarctic region: the physical and physiological factors that resist establishment of non-native marine species; changes to resistance under climate change; the role of legislation in limiting marine introductions; and the effect of increasing human activity on vectors and pathways of introduction. Evidence of non-native marine species was limited: up to 2019 just four marine non-native and one cryptogenic species that were likely introduced anthropogenically had been reported free-living in Antarctica or in the sub-Antarctica islands, but no established populations have been reported. An additional six species had been observed in pathways to Antarctica that are potentially at risk of becoming invasive. I estimated there may be approximately 180 vessels and 500+ voyages in Antarctic waters annually. However, these estimates are necessarily speculative because relevant data are not recorded comprehensively. In response to the scarcity of data on ship movements into the Southern Ocean, I obtained data on ship activity in the Southern Ocean from 2014-2018 inclusive and developed a ship traffic network for Antarctic-going vessels. I analysed the ship movements and conducted a spatially-explicit assessment of introduction risk for non-native marine species in all Antarctic waters. I found that vessels connect Antarctica via an extensive network of ship activity to all global regions, and especially South Atlantic and European ports. Ship visits were more than seven times higher to the Antarctic Peninsula and the South Shetland Islands than elsewhere around Antarctica. I found that, while the five recognised 'Antarctic Gateway cities' are important last ports of call, an additional 53 ports had vessels directly departing to Antarctica from 2014-2018. I identified ports outside Antarctica where biosecurity interventions could be most effective and the most vulnerable Antarctic locations where monitoring programmes for high-risk invaders should be established. Biofouling communities within the major pathway to Antarctica from Europe via the South Atlantic, identified in the network analysis, became my next focus. I obtained biofouling samples from the polar research vessel RRS James Clark Ross and found that niche (protected) areas of the hull represent significantly greater colonisation (species richness) and propagule pressure (individual abundance) than exposed areas of the hull. The composition of the biological communities did not differ among exposed and niche areas, but did change significantly among the three surveys conducted. Only six species were found on the ship's hull in Antarctica, but they included a known invasive bryozoan, Tricellaria inopinata, and barnacles that have no counterparts in Antarctica. While the role of hull fouling is recognised as a globally important vector for introductions of non-native marine species, the role of a vessel's internal pipework has been overlooked. I conducted the first comprehensive study of biofouling macrofauna living inside an Antarctic vessel's internal seawater systems, finding breeding communities of Jassa marmorata (Amphipoda) and mytilid mussels throughout the internal pipework system. I found fouling communities that occluded ~9-17% of a pipe's cross-sectional area, increasing running costs for ships. Since ships are constantly pumping their water through their pipework, they are likely to be releasing propagules at all stages of their voyages, including in polar regions. Before I started my research, Antarctic operators and policy-makers were unaware of the total number of vessels that visit Antarctica. Now, I have provided comprehensive insight into the most traversed routes to Antarctica and identified Antarctic locations that are the most likely recipient locations for non-native marine species. I found that non-native species from temperate regions can survive passages through polar areas and that sheltered sections of the hull and internal systems are especially important sites for both propagule and colonisation pressure. Together, these results demonstrate that Antarctica is well connected to worldwide marine ecosystems and that biofouling on ships poses an important and growing introduction risk to Antarctica.

The impact of corrosion and biofouling on offshore wind turbines is considered to be a key issue in terms of operation and maintenance (O&M) which must be better addressed. Early design assumptions for monopile foundations anticipated low, uniform corrosion rates in a sealed compartment that would be completely air- and water-tight. However, operational experience has shown that in practice it is very difficult to maintain a fully sealed compartment, with seawater and oxygen ingress frequently observed within many monopiles across the industry. A key concern is that this situation may accelerate corrosion of the internal surfaces. On the external surfaces, the accumulation of biofouling is known to impede the safe transfer of technicians from vessel to transition piece (TP) and requires frequent cleaning. It is also likely to influence the dynamic behaviour of the foundation due to the added weight and the hydrodynamic loading due to thickness and surface roughness changes. There is sufficient evidence to suggest that the current offshore wind guidelines on biofouling could be improved to optimise the design margins. This thesis investigated the influence of internal monopile corrosion and external biofouling growth on the turbines at Teesside Offshore Wind Farm (owned and operated by EDF Energy). At Teesside, the primary drivers of internal monopile corrosion are identified as temperature, oxygen, pH and tidal variation. The influence of each of these parameters on the corrosion rate of monopile steel were investigated in a series of laboratory experiments and in-situ monopile trials. The experimental study was conducted at EDF laboratories in France using 186 corrosion coupons that were exposed to various treatments simulating internal monopile conditions. At Teesside, 49 coupons were suspended at various internal monopile locations across 5 foundations. In both cases, the weight loss measurement of coupons over time was used to determine the corrosion rates. Results suggest that tidal (wet/dry cycles) low pH and oxygen ingress have the greatest influence on the corrosion degradation of unprotected monopile steel. Internal tidal variations create a particularly aggressive corrosion environment. A decision tree matrix has been developed to predict corrosion rate classification (high/medium/low) under a range of environmental conditions. In parallel, a biofouling assessment was conducted at Teesside Offshore Wind Farm to determine the type and extent of marine growth on the intertidal and submerged zones of turbines. This has enabled a better understanding of the species diversity and community morphology but has also facilitated the development and testing of two sampling methodologies for the intertidal and subsea regions of offshore wind turbines; scrape sampling and remotely operated vehicle (ROV) surveying, respectively. The results of the assessment suggest a zonation pattern of marine growth with depth that is consistent with findings from other offshore wind farms and platforms. A super abundance of the non-native midge species T. japonicas at the intertidal zone has also been observed at other offshore wind farms in Belgium and Denmark, however, this is first evidence of its existence at a UK offshore wind farm. Removal of biofouling from the intertidal zones and jet-washing has now been optimised to coincide with peak settlement periods of mussels and barnacles. Image analysis and 3D mapping was conducted on the subsea ROV video footage to estimate thickness, roughness and added weight of biofouling. This research provides an initial investigation into the effects of internal corrosion and external biofouling on monopile foundations at Teesside Offshore Wind Farm. The methodologies developed for this investigation and the results are critically discussed in the context of asset life assessment and improvements are suggested in further work.

The present thesis addresses the role of shipping as an unintentional and very efficient pathway for spreading aquatic non-native species around the globe, through two major vectors: ballast water and biofouling. The challenge with ballast water is that a myriad of organisms are transported across natural barriers before dispersal, transcending biogeographic regions and this wholesale movement of marine life contributes to the spread of diseases and to the homogenization of coastal habitats. The United Nations nominated the issue as one of the four greatest threats to the oceans, causing extremely severe environmental, economic and public health impacts. This research is primarily focussed on the investigation of portable instruments (fluorometers) developed to support inspections regimes on the efficiency of ballast water management systems required by international regulations and compare them to well-established research tools, e.g. flow cytometry. Viability tests of phytoplankton groups in the size range defined by these regulations in natural assemblies were conducted as well as in treated ballast water samples. An overall good correlation between the measurements taken with the fluorometers and in comparison with the flow cytometry analysis was found. Analysis of treated ballast water samples showed a large variation in the number of viable cells, however indicating the same risk on all occasions for regulatory purposes. In addition, experiments to examine the application of flow cytometry and fluorometry in characterizing natural phytoplankton communities, with special attention to cell size, found relevant results in the context of the size class distribution based on flow cytometry and semi-quantification using chlorophyll as a proxy for cell density. Found results may indicate the need for further refinement of portable fluorometers with filtration steps and in use for compliance issues. Species can also be transported on virtually all of the submerged areas on ships and so antifouling systems are used to reduce fouling. However, with increased regulation of biocides used in antifouling coatings, there is a need to find efficient and sustainable alternatives. In this regard, experiments using low salinity to kill fouling organisms in areas of the ship where it is difficult to coat and therefore tend to accumulate fouling organisms, e.g. ships sea-chest, were conducted. Results showed high levels of mortality in mature biofouling communities exposed to two hour treatment with a salinity of 7 psu. Low salinity treatments can offer an environmentally friendly biosecurity tool for minimising and controlling ships sea-chest biofouling that is simple and would not cause undue delay or costs for the ship. Large quantities of non-native species are transported daily either through ballast water or ships biofouling; however, the rate of establishment of invasive species is unclear and associated to the interplay of varied factors. Moreover, in many cases, it is difficult to disentangle the level of influence of the different vectors and pathways in this transfer. As a result, a general approach to control and minimise the unintentional transfer of non-native species through shipping should consider the adoption of integrated studies where important vectors are considered together as the best way to move forward. In the present case, it means the necessity of having biofouling under control together with ballast water.

There exists a broad range of automotive and marine coatings which cater for aesthetic considerations as well as protecting against a number of potentially deleterious environmental factors. Polyurethanes (PU) paint coatings are particularly widely used in this application. It is also possible to optimise the aesthetic and protective properties of these coatings yet further through the application of an additional paint protection scheme (PPS). Such PPS layers are often siloxane based thin films which are commonly applied due to the particularly demanding performance requirements in this automotive and marine sectors. A range of experimental methods and chemical analysis techniques have been used to study and establish the formulation and baseline performance characteristics of one such, commercially available siloxane based PPS. Orbitrap, gas chromatography (GCMS) and tandem mass (MS/MS) spectroscopy techniques have shown the siloxane based PPS polymers within the present study to contain amino, alkoxy and hydroxyl functionalities, as well as methyl pendants. Atomic force microscopy (AFM), glossmeter measurements, spectrophotometry, water contact angle analysis (WCA) and X-ray photoelectron spectroscopy (XPS) have been used to characterise the effect of the PPS on a polyurethane paint coating. Results show that the existing system deposits: ~20 at.% of a Si-O based coating. This alters the surface wettability, from water contact angles and surface free energy (SFE) values of ~65° and ~56 mN/m, to ~90° and ~31 mN/n respectively. In addition, this coating increases surface gloss from ~64° to ~75° at 60° measurement angle; and decreases surfaces roughness (Ra) from ~60 to ~30 nm. Attempts to modify and enhance the wettability, gloss and stiffness of this existing coating, using a number of polymers and fillers were generally unsuccessful. However, an increase in surfaces stiffness of ~38% was observed through the use of 0.25 wt.% carboxylic functionalised nanodiamond. In recognition of the difficulty in augmenting the existing siloxane PPS coating, an entirely new coating and matrix was developed using an oxygen/argon pretreatment and a fluoroalkyl silane (FAS) coating, with sole emphasis on two critical performance characteristics: superhydrophobicity and anti-biofouling. It was found that the oxygen/argon plasma treatment increased both the surface roughness (Ra) and SFE of the PU paint coating from approximately ~60 to ~320 nm, and, ~52 to ~80 mN/m respectively. It was also found that the plasma process created a multiscale roughened texture through the process of differential ablation between the PU polymer and the barium sulphate solid content, present in the paint as an extender, and other additives. In addition, the process also imparted favourable polar groups into the PU surface from the ionised and radical oxygen species in the plasma. When the FAS coating was subsequently applied to the PU without prior plasma treatment, there was a significant increase in water contact angles. This parameter increased from approximately 60° on untreated PU to around 130° with FAS applied. In this case, the SFE decreased to ~7.5 mN/m and showed 42.0 at.% fluorine present as indicated by XPS. However, subsequently applying the FAS polymer after plasma pretreatment takes advantage of the known synergistic relationship that exists between surface roughness and low surface free energy coatings. The two processes combined to create superhydrophobicity with a surface that exhibited water contact angles up to 153.1°. With this optimised process, the apparent SFE was reduced to 0.84 mN/m with a more highly fluorinated surface present. In this case 47.2 at.% surface fluorine was observed by XPS, with a coating thickness of ~26nm. The coating has also been shown to exhibit excellent resistance to a salt spray environment compared to the siloxane based coating, as well as provide a an improvement in the PU's anti-biofouling capability against staphylococcus epidermidis. In addition to the changes in SFE, the plasma treatments also alters levels of surfaces gloss and colour. After exposure to 600s of plasma gloss levels are shown to reduce from ~50 to ~21 (at 60°), with a small but significant increase in the lightness and yellowness of the surface.

Microorganisms attachment to the surfaces located in the marine water has become a significant problem. Historically, the antifouling properties of the coatings were achieved by using biocides, which had a negative consequence to the marine environment. Currently, alternative environmental friendly methods are required. This thesis aimed to investigate and produce the antifouling coatings that can be used as potential candidates in the marine industry. In this study, a range of novel polymer nanocomposite coatings was fabricated via the method of solvent and tested based on the strategy of microbial adhesion. The composition of the coatings mainly contains polidimethylsiloxane (PDMS) and different nanomaterials. The coatings applied on glass substrate were characterised using X-ray spectroscopy (XRD), scanning electron microscopy (SEM), contact angle measurements, inductively coupled plasma mass spectroscopy (ICP-MS) and atomic force microscopy (AFM). In biofouling assays, attachment of bacteria B. Subtilis and three marine microalgae (Skeletonema sp., Amphora sp., D. Salina) was investigated in laboratory scale. The obtained results suggested that small amount of nanoparticles in the polymer matrix can improve the antifouling settlement behaviour of the coatings. All microalgae attached more on PDMS/SiO2 and control surfaces (glass and PDMS) compared to the coatings containing multiwall carbon nanotubes (MWCNT) and sodium bismuth titanate (NBT). The influence of contact time, surface roughness and surface wettability was also studied. The microbial attachment varied significantly with respect to contact time and surface properties. There was no obvious evidence showing that the wetting properties and the roughness of the coatings have an effect on growth ... [cont.].

Biofouling is the undesired biofilm formation on surfaces at a liquid interface that interferes with the affected substrate’s function. It is a ubiquitous problem in many engineered systems in industry. Biofouling causes contamination, essential damage to materials, and impedances to crucial industrial processes. These adverse effects lead to health hazards, gross increase in energy consumption, and significant decrease in overall productivity, all of which result in higher operational costs and environmentally destructive consequences. Interest in discovering effective alternatives to conventional antimicrobial agents has gained momentum. Current anti-biofouling strategies have significant disadvantages, such as the generation of toxic by-products, indiscriminate corrosion of surrounding materials and the environment, and promotion of resistance development. Alternative methods of controlling biofouling are in high demand because present-day solutions are far from sustainable. Plant secondary metabolites are promising candidates as novel biocides because they are (i) highly effective in killing microbes while being non-toxic to humans at antimicrobially active concentrations, and (ii) safer and non-damaging to the natural environment. Herein, antimicrobial efficacies of five plant-derived compounds were assessed against various species of planktonic bacteria as well as biofilms at various maturity stages. Allyl isothiocyanate (AIT) and cinnamaldehyde (CNAD) displayed the greatest inhibitory effects against all planktonic species tested. The minimum inhibitory concentration is defined as the lowest concentration of a substance that inhibits visible microbial growth, and the MBC is defined as the lowest concentration at which 99.9% of the population is killed. AIT yielded MICs of 156.25 mg/L and MBCs of 156.25 to 312.5 mg/L, and CNAD yielded MICs of 78.125 to 156.25 mg/L and MBCs of 78.125 to 312.5 mg/L. Furthermore, 312.5 mg/L AIT and 625 mg/L CNAD successfully reduced > 80% of biofilm adhesion as compared to negative controls. AIT and CNAD were therefore further evaluated extensively. Hindered by their volatile nature and immiscibility, plant secondary metabolites typically do not reach their maximum antimicrobial capacity due to low bioavailability. Thus, they would benefit from being protected and delivered in nano-sized carriers. In this study, mesoporous silica nanoparticles (MSNs) were evaluated as carriers for AIT and CNAD delivery. In one, employment of MSNs as carriers doubled the antibacterial efficacy of free form AIT and increased kill rate of free form CNAD by six times. Furthermore, free form AIT caused ~70% of 60 day-old biofilm to detach, whereas AIT-loaded MSNs essentially removed all of the biofilm. As for CNAD, its free form had no significant effect, whereas CNAD-loaded MSNs caused ~80% reduction in biofilm biomass. MSNs were further engineered to incorporate lactose pore caps to achieve specific, on-command delivery. These MSNs were designed to respond to external stimuli intelligently, with gatekeepers that degrade only in the vicinity of certain target bacteria that are able to metabolise lactose. Capped AIT-loaded MSNs reduced bacterial viability by ~85% as compared to the negative control, while capped CNAD-loaded versions reduced viability by ~40%. This stimuli-triggered MSN delivery technology would be more sustainable than current methods because resistance development would be lowered, and the delivery vehicles could be recycled and reused. Herein, the complete AIT- or CNAD-loaded, lactose-capped MSNs delivery complex proved to be an effective and environmentally conscientious system for killing unwanted bacteria.

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

This study investigated the effects of Ar/H2O plasma treatment on the surface and bulk properties of polytetrafluoroethylene (PTFE) and polyethylene terephthalate (PET) surgical mesh materials as a method to modify and mitigate biofouling events that reduce their performance. With regards to bulk properties, findings from uniaxial tensile testing of these substrates in mesh and suture form show that plasma treatment can weaken their tensile properties. Increasing treatment duration and surface area to volume ratio were found to be major factors that resulted in further reduction of these properties. With regards to surface properties, the direct application of plasma on these substrates was not found to reduce biofouling in the form of protein adsorption and S. aureus attachment compared to untreated control surfaces. These experiments suggest that the deposition of a subsequent coating after plasma treatment is needed to further control biofouling events and is a future direction worth investigating.

The fundamental understanding and control of the interactions that occur between surfaces and chemicals allows us to design materials with enhanced binding and reactive properties for various industrial, environmental, and clinical applications. However, understanding and optimizing these interactions can also be used to limit the attachment and accumulation of undesirable substances and organisms to surfaces which may otherwise hinder their successful operation. This dissertation describes research on the tuning and optimization of surfaces and operating conditions for different purposes ranging from biological treatment of water and wastewater to the prevention of the undesired attachment of microbial biofilms to functional surfaces. Modification of the surface of granular activated carbon (GAC) using the cationic polymer polydialydimethyl ammonium chloride (polyDADMAC) was studied as a strategy to improve the removal of the persistent environmental contaminant class per- and polyfluoroalkyl substances (PFASs). Specifically, complex water matrices were used in these studies to simulate challenging conditions that are environmentally relevant. Amending the surface with polyDADMAC concentrations as low as 0.00025% enhanced GAC’s adsorption capacity for both short- and long-chained PFASs, even in the presence of competing ions. Regeneration with minimum disruption to the adsorbent’s structure was achieved using low-power ultrasound, supporting the consideration of polyDADMAC-modified GAC was an effective, regenerable adsorbent for real environmentally relevant water conditions. The relationships between the influent nutrient ratios in the context of wastewater treatment and the mechanisms responsible for biofilm formation were investigated. Wastewater treatment is an example of a scenario where biofilm formation may be either desirable or undesirable depending on the treatment system being employed. A comprehensive evaluation of the effect of Carbon/Nitrogen ratio in influent wastewater on biofilm characteristics and relevant mechanisms were studied. Pseudomonas aeruginosa was used as a model organism due to its widely understood biofilm formation pathways, as well as its prevalence in the environment, distribution systems, and in clinical settings. The development of a dual-species biofilm of P. aeruginosa and N. winogradskyi was also influenced by C/N, with increase in the relative abundance of the slower-growing N. winogradskyi above C/N=9. These results indicate that altering operational parameters related to C/N may be relevant for mitigating or promoting biofilm formation and function depending on the desired industrial application or treatment configuration. Despite the benefits of chemically- and biologically mediated surface modifications, microbial adhesion to surfaces can also be detrimental in the context of biofouling, which yields industrially relevant surfaces such as water treatment membranes less efficient or causes adverse patient health outcomes in clinical settings. In this context, a culture-independent biofilm quantification protocol was developed to accurately quantify cellular and extracellular components attached to medically relevant surfaces such as urinary catheters. The developed multipronged approach had validated efficacy as it was verified to accurately quantify biofilms of four pathogenic clinical isolates, two types of silicone catheters in vitro and indwelling catheters in patients. Characterization and assessment of synthesized hydrogels made of a modified chitosan/ silver nanoparticle composites showed the potential of these material for antimicrobial and antifouling purposes. Three synthesis methods were compared in terms of their effects on the physical, mechanical, and antimicrobial capabilities of the hydrogels, and evaluation showed the potential for tuning the synthesis to yield materials with different physical and mechanical properties but equally promising antimicrobial and antifouling potential. This gives rise to the possibility of using these composites in a range of industrially relevant scenarios depending on the desired characteristics for use. The quantitative understanding of factors impacting surface modifications and microbial attachment to surfaces will be valuable for improved water treatment systems as well as to limit or help guide biofilm formation on medically- and industrially relevant surfaces.

Post-surgical adhesions are internal scars that pathologically adhere together adjacent tissues/organs/biomaterials. They pose a tremendous but frequently underestimated burden across many surgical disciplines, being especially prevalent following abdominal surgery. Peritoneal adhesions can cause discomfort, intestinal obstructions, infertility, and increased morbidity/mortality of subsequent surgery. Once formed, treatments for adhesions tend to be risky and ineffective, so prophylactic strategies are desirable. Implantation of meshes, such as in hernia repair, often exacerbates peritoneal adhesions. Knitted polypropylene (PP) meshes are the most common hernioplasty devices, but are notoriously adhesiogenic owing to material and structural characteristics that promote incorporation, such as hydrophobicity and reticular construction. The ideal strategy to prevent mesh adhesions entails adhering a smooth, continuous, hydrophilic barrier material on the mesh visceral face to mitigate tissue attachment processes. Prior studies developed polymerized cyclodextrin (pCD) materials having unique capabilities for sustained, multi-window drug release, and suggested that these hydrophilic polymers passively resist cell attachment. In several animal species, pCD could deliver antibiotics for weeks to successfully resolve mesh infection, another hernioplasty complication for which only suboptimal solutions exist. In the present work, pCD materials were explored toward application as novel adhesion barriers for PP surgical meshes. First, nonthermal plasma activation was assessed as a strategy to improve PP-pCD bonding, as PP is generally unreceptive to coatings. Plasma introduced hydroxyls onto PP, enhancing PP-pCD adherence. Second, protein adsorption, bacterial attachment, and fibroblast viability/attachment upon pCD-coated and bare PP materials were evaluated. These events play roles in mesh adhesion, infection, and biocompatibility. pCD decreased protein adsorption and bacterial attachment to PP, without fibroblast cytotoxicity. Third, effects of PP plasma activation on protein adsorption, fibroblast/bacterial attachment, and mesh mechanical properties were investigated. Regardless of duration, plasma exposure of bare PP reduced protein adsorption and bacterial attachment, and increased fibroblast attachment, but longer treatments progressively embrittled PP mesh. Fourth, preliminary studies in vivo explored effects of pCD barriers on adhesions to PP mesh. These animal experiments suggested that pCD-covered mesh surfaces resisted adhesions, while bare PP meshes did not. Altogether, pCD materials have potential as adhesion barriers that could uniquely combat both mesh adhesions and prosthetic infection.

The demand for efficient and effective water purification processes encompasses a breadth of industries. As such, a multitude of filtration technologies and unique approaches have been developed. Adoption of an appropriate filtration technology depends on the nature of the water to be treated and the desired finished water quality. The aim of this work was to evaluate a select set of novel membrane filtration technologies and approaches for their efficiency and applicability. Processes evaluated include (1) electrofiltration utilizing a novel inorganic membrane, (2) a couple forward osmosis – membrane distillation for brine treatment, and (3) a novel in-situ ultrasonic self-cleaning membrane.The application of an electrical potential across a membrane during filtration results in unique effects, dependent on the feed water parameters, the membrane properties and system design. Of particular interest is the production of electroosmotic flow. Electroosmotic flow is the movement of water through the membrane, induced by an electrical potential. This effect is independent of transmembrane pressure. This phenomenon appears to be particularly outspoken in dilute acidic and basic aqueous solutions in oxidic membrane structures. Electroosmotic flow, and the associate specific energy consumption, was studied for electrofiltration of acidified DI water with a 2 mm thick high purity α-Al2O3 membrane with a porosity of 35%, and a narrow pore size distribution around 700 nm. It was found that at a temperature of 23°C, a pH of 4 and a pressure difference, Δp, of 15 kPa, the membrane flux increased from 3.7×10-9 to 5.2×10-9 m/s (59 to 82 LMH) after application of a voltage, ΔΦ, of 10 V. This 38% increase at pH 4 required a total electrical SECEOF of 1.5 MJ/m3 (0.43 kWh/m3). Since the electro-filtration proper requires a minimal SECminEF of only ~23 kJ/m3 (6 Wh/m3), the observed SECEOF is ascribed almost entirely to electrode losses and ionic and molecular transport resistance. Under the pH 10 condition, the membrane flux decreased from 4.0×10-9 to 3.0×10-9 m/s (63 to 47 LMH) after application of a voltage, ΔΦ, of 10 V, corresponding to a 29% decrease in water flux. At a minimum Δp =1.5 kPa and conditions otherwise the same, the membrane flux increased from 4.9×10-6 to 1×10-5 m/s (18 to 37 LMH) after application of ΔΦ = 10 V. The total electrical SEC, associated with this increase was 1.2 MJ/m3 (0.22 kWh/m3). The energy efficient use of electrofiltration to generate water flux without moving parts, along with reversibility of the flow direction, has immense potential for membrane filtration.Following this, a bench-scale forward osmosis – membrane distillation (FO-MD) system was applied to flue gas desulfurization (FGD) wastewater generated at coal fired power plants (CFPPs) focusing on water recovery, salt rejection, thermal energy demands, and potential for harvesting low-grade waste heat. Using flat sheet cellulose triacetate (CTA) and polytetrafluoroethylene (PTFE) membranes, treatment of synthetic and collected FGD wastewater was evaluated across a range of applicable temperatures (43.3 – 65.5°C) and draw solutions (NaCl, CaCl2, PAA-Na). Highest water fluxes were observed at the highest NaCl and CaCl2 draw solution concentrations (3.4M) and temperatures (65.5°C) evaluated, with FO and MD fluxes reaching 37 and 25 LMH, respectively. The FO-MD system achieved over 99.8% rejection of all surveyed components (Na, K, Ca, Mg, B, Cl-, SO42-), producing permeate with conductivities below 105 μS/cm. An 89% water recovery occurred using a 3.4 M sodium chloride draw solution. While the FO-MD process is capable of treating FGD wastewater, basic osmotic backwashing was insufficient at restoring the FO membrane water flux. Further investigation of membrane fouling and scaling is warranted. Investigation of the required heat for MD indicates that adequate low-grade waste heat sources are available on-site, suggesting the FO-MD process can be an effective, energy efficient and sustainable treatment technology for FGD wastewater.Lastly, membrane filtration of municipal wastewater, often termed a membrane bioreactor (MBR), can obtain a high quality effluent that surpasses conventional treatment capabilities. Yet, activated sludge filtration results in biofilm growth and a build-up of extracellular polymeric substances (EPS) on the membrane surface, reducing filtration efficiency and requiring cleaning. Ultrasound is a potential cleaning method that has been shown to be effective at removing biofilm formations. Utilizing piezoelectric lead zirconate titanate (PZT) membranes, ultrasound was produced in-situ, during filtration of 0.95 mM KCl and 0.05 mM KHCO3 buffered DI water and activated sludge wastewater solutions. Impacts of the membrane poling process, the applied electric field and in-situ ultrasound were studied. Residual oil from poling the PZT membrane resulted in a more hydrophobic membrane with reduced permeability. The application of an 80 Vpp, 45kHz AC signal had no impact on unpoled or poled PZT membranes when filtering the buffered DI feed solution. When applied to filtration of activated sludge wastewater, the 80 Vpp, 45kHz AC signal resulted in a greater retention of 72-hr normalized water flux for the poled PZT membrane, when compared to a non-active poled membrane over 7 days of filtration. Thus, in-situ ultrasound is a potential online fouling prevention technique.As explored, these membrane filtration technologies and approaches result in energy reductions and fouling mitigation. Through continued development, these processes evaluated at bench scale may advance the membrane filtration industry as a whole.

N/A

The commercial microalgal industry consists of three major stages in the development of bioproducts, biomaterials, and biofuels: the growth of microalgae in open ponds or closed photobioreactors, the various harvesting and dewatering processes, and the final product preparation, extraction and/or conversion. Harvesting and dewatering of microalgae accounts for ~30% of the production costs in the industry and there is no economy-of-scale, limiting the impact of this industry to high-value, low-volume products. There are several methods utilized across the industry for the harvesting and dewatering of microalgae, with no universal method identified for all microalgal strains and products. This research focused on crossflow filtration, a relatively new harvesting method with the potential to reduce costs and energy inputs at scales suitable for high-volume products, e.g., animal feed, human food, biofuels, etc. The major fouling effects algae have on membranes are the primary limitations of this method, incurring high maintenance and operating costs. Polyvinylidene fluoride (PVDF) and polyethersulfone (PES) membranes were compared with novel, non-woven carbon nanotube (CNT) membranes to assess the anti-biofouling effects of these materials. Membranes were characterized through contact-angle measurements and permeability assessments in a novel constant-flux crossflow filtration system. The fouling effects on the membranes were assessed using cultures of Chlorella vulgaris and a wild strain of Nannochloropsis through threshold flux (TF) calculations and scanning electron microscopy. In all experiments, CNT membranes had less pore blocking and were more resistant to adhesion by bacteria, microalgae, extracellular organic material, salts, and minerals with less cake layering, suggesting improved fouling resistance when compared to PVDF and PES membranes. TF and permeability experiments demonstrated that CNT membranes exhibited improvements in fouling resistance by 1.6-fold and 1.9-fold for Chlorella and Nannochloropsis cultures, respectively, compared to PVDF membranes. CNT membranes also resulted in 8.7-fold and 7.9-fold improvements in fouling resistance compared to PES membranes for the Chlorella and Nannochloropsis cultures, respectively. Lastly, a techno-economic analysis (TEA) was performed to estimate the production costs for harvesting microalgal biomass using an industrial spiral-wound filtration system. Using this model, TEA evaluations supported that CNT membranes with increased permeability have the potential to reduce production costs.

Given its potent biocidal properties, graphene oxide (GO) holds promise as a building block of anti-microbial surfaces, with numerous potential environmental applications. Nonetheless, the extent to which GO-based coatings decrease bacterial adhesion propensity, a necessary requirement of low-fouling surfaces, remains unclear. AFM-based single-cell force spectroscopy (SCFS) was used to show that coatings comprising GO nanosheets bonded to a hydrophilic polymer brush, mitigate adhesion of Pseudomonas fluorescens cells, while preserving GO’s intrinsic biocidal activity. This work demonstrated the simultaneous biocidal and low-adhesion GO coatings by grafting poly(acrylic acid) (PAA) to polyethersulfone (PES) substrates via self-initiated UV polymerization, followed by edge-tethering of GO to the PAA chains through amine coupling. The chemistry and interfacial properties of the unmodified PES, PAA-modified (PES-PAA), and GO-modified PES (PES-GO) substrates were demonstrated using ATR-FTIR, Raman spectroscopy, contact angle goniometry, and AFM to confirm the presence of PAA and covalently bonded GO on the substrates. Using SCFS, it was shown that peak adhesion force distributions for PES-PAA (with mean adhesion force F ̅Peak = -0.13 nN) and PES-GO (F ̅Peak = -0.11 nN) substrates were skewed towards weaker values compared to the PES control (F ̅Peak = -0.18 nN). The results show that weaker adhesion on PES-GO was due to a higher incidence of non-adhesive (repulsive) forces (45.9% compared to 22.2% over PES-PAA and 32.3% over PES), which result from steric repulsion allowed by the brush-like GO-PAA interface.

Bubbles are commonly found in the world around us, from industrial products to carbonated beverages. This thesis will discuss three processes involving of bubbles, from applications to fundamental phenomena. In the first portion of this thesis, I describe the use of bubbles to prevent the formation of marine biofilms and other colonizing organisms onto built structures, collectively referred to as biofouling. Biofouling detrimentally affects the structures upon which they grow, increasing drag and fuel consumption of moving vessels, reducing performance of acoustic sensors, and enhancing degradation of static structures. With recent international bans placed on common biocidal coatings, there is a demand for environmentally friendly antifouling technologies with strong performance. Bubbles rising along a submerged surface have been shown to inhibit biofouling growth, but little work has been done to determine the primary mechanisms responsible for their antifouling behavior. In this thesis I discuss a combination of field and laboratory experiments as well as a theoretical approach used to gain insight into the dominant mechanisms at play, thus laying a foundation for optimization of this antifouling technique. We find that biofouling is inhibited by shear stresses generated throughout the flow, and the degree of biofouling prevention relates to the distribution of bubbles which locally alters the shear stress. Inspired by the potential for direct interactions between bubbles and biofouling, the second topic of this thesis considers the process by which a bubble dewets, or "sticks to", a solid surface. As a bubble approaches a solid surface, the liquid between the gas and solid begins to drain until it resembles a thin film. Upon rupture of this thin film, the air dewets the surface as a contact line is formed and expands. Previous work regarding this contact line motion assumes viscous effects dominate the spreading dynamics while inertial effects are neglected. Studying the early-time dynamics of dewetting bubbles, we find viscosity to be negligible while inertia and capillarity govern the motion of a newly established contact line, suggesting early stages of dewetting are more rapid than anticipated. In the final portion of this thesis, I discuss the fundamental stability of bubbles in volatile liquids. When a bubble arrives at a free surface, we typically expect the film of the bubble cap to thin over some period of time until it ruptures. Traditionally, the drainage of this film has been considered inevitable with evaporation only hastening the film rupture. Here I show air bubbles at the free surface of liquids which appear to defy traditional drainage rules and can avoid rupture, persisting for hours until dissolution. Using pure, volatile liquids free of any surfactants, we highlight and model a thermocapillary phenomenon in which liquid surrounding the bubble is continuously drawn into the bubble cap, effectively overpowering the drainage effects.

The presence of significant hard and soft biofouling on the hull of a marine vessel can produce increased resistance potentially limiting system performance and leading to added fuel consumption. It has been estimated that the presence of biofouling has led to roughly $2.9 billion in additional operating costs and the resulting excess fuel consumed each year is expected to introduce about 23 million tons of carbon dioxide into the atmosphere. Therefore, it is important to understand how biofouling leads to increased friction drag for flows over marine surfaces with the ultimate aim of reducing their deleterious effects. While a body of research exploring the consequences and means of drag production for hard fouling exists which informs the efforts of ship designers and operators, the effects and drag production mechanisms of soft fouling remain relatively unexplored. The few studies performed on soft biofilm layers show drag increases ranging from ~10—300% in lab scale experiments; ship trials showed that after removal of a biofilm layer from its hull, a frigate required 18% less shaft power to maintain a cruising speed of 25 knots. That such large drag penalties can be produced by low-form, `slimy' surfaces is a surprising result which researchers suggest may be due to additional physical mechanisms different from those of hard biofouling. The primary objective of this dissertation was to disassociate the added drag produced by filamentous biofilm layers into contributions from roughness and compliance effects. Biofilm layers comprised of diatoms and filamentous green algae were grown on smooth acrylic surfaces for nominal incubation times of three, five, and ten weeks in a specially built flow loop. During hydrodynamics trials, biofouled surfaces were installed in a high-aspect ratio, fully developed channel flow facility and exposed to flows ranging from ReH ≈ 5 000 -- 30 000. Measurements of the pressure drop along each fouled panel revealed drag increases spanning ΔCf ≈ 14--364%. The wide range in drag penalty was linked to variations in flow speed, average thickness of the biofilm layers, and the percentage of each surface covered by fouling. These results support a previously proposed scaling correlation which also relates frictional performance of biofilm layers to their thickness and coverage. Empirical formulations were produced that characterized the added drag of stable biofilm layers within ±10% of their measured values. Seven rigid surfaces replicating six biofilm layers were manufactured using highly resolved laser scans of the time-averaged, spatially filtered biofilm surface profiles. Drag penalties of ΔCf ≈ 57--193% were measured for these rigid surfaces and shown to scale with the average trough-to-peak roughness height and downstream spacing between large streamers. An empirical formula characterized the added drag on rigid replicas to within ±15% of measurements. Finally, a simple model was proposed which decomposes the added drag experienced by a biofilm layer into contributions from roughness and compliance effects. Once applied to this model, resistance data show that about half of the added drag experienced by the biofilm layers was due to rough effects. Particle Image Velocimetry measurements captured the mean flow along the surfaces. Results reveal that flow above biofilm layers and rigid replicas largely resemble one another in the outer flow region suggesting that mechanisms underlying the drag increase are confined to a region of flow in the immediate vicinity of the biofilm layers.

Abstract: Biofouling refers to the undesirable accumulation and growth of biological substances on a artificial surface with time. Biofilm on the surfaces occurs due to bacterial aggregation and extracellular polymeric substance (EPS) that acts as the construction material of biofilm. EPS consists of long-chain biomolecules such as polysaccharide, protein, and DNA. An interesting phenomenon in the observation that form filamentous bacterial aggregates in continuous flow regime that is called streamer. In this dissertation, two different modes of failure of bacterial streamers have been investigated and quantified in a microfluidic device in a creeping flow regime. In both analyses, the quantification of streamer deformation and failure behavior was performed by using 200 nm fluorescent polystyrene beads, which firmly embed in the EPS and act as tracers. In the first mode of failure, this bacterial streamers, which form soon after the commencement of flow begin to deviate from an apparently quiescent fully formed state in spite of steady background flow and limited mass accretion indicating significant mechanical nonlinearity. This nonlinear behavior shows distinct phases of deformation with mutually different characteristic times and comes to an end with a distinct localized failure of the streamer. A simplified nonlinear analytical model has been developed to describe the experimentally observed instability phenomena assuming a necking route to instability. The model leads to a power law relation between the critical strain at failure and the fluid velocity scale exhibit excellent qualitative and quantitative agreement with the experimental rupture behavior. The second mode of failure has been investigated and quantified where streamers break due to the growth of voids and cracks in the biomass. This failure occurs in thick bacterial streamers in a microfluidic device with micro-pillars and stands in strong contrast to necking-type instability observed in the thin bacterial streamer. Void/crack growth time-scales could be characterized as short-time scales, and long time-scales and the void/crack propagation showed several instances of fracture-arrest ultimately leading to a catastrophic failure of the entire streamer structure. Amongst the different application domains that bacterial streamers can impact, is the domain of biofouling of membranes. The effect of biofouling in a microfluidic filtration system has been investigated by using a microfluidic filtration device consists of cylindrical microposts with a pore-spacing of 2 µm, thus mimicking a microfiltration membrane system operating in a dead-end mode. The existence of a critical pressure difference above which pronounced streamer formation was observed, which eventually leads to rapid clogging of the device with an accompanying exponential decrease in permeate flow. Moreover, the de-clogging of pores also occurs intermittently, which leads to small time scale fluctuations (O(101 seconds)) superimposed upon the large time-scale (O(102 minutes)) clogging of the system. These de-clogging phenomena leads to a sharp increase in water permeation through the membrane, but deteriorates the water quality as biomass debris is transported in the permeate. It has also been observed that the pH of the feed solution strongly affects biofouling of the microfluidic filtration system.

It is now generally recognized that the dominant state of microorganisms in nature is that of the biofilm, a community of microorganisms that grows, not as a free-swimming community, but in close association with an interface between two phases, be it a liquid and solid surface, liquid and air, or even two non-miscible liquids (such as water and oil). This growth form possesses many unique attributes when compared to its planktonic, free-swimming counter part. Biofilms are composed of cells with diverse metabolic states, are protected from their environment by the extracellular matrix, can differ greatly in conditions (e.g. pH, diffusion of nutrients) within the biofilm compared to the bulk medium. These factors result in biofilms being more resistant to biocide and antibiotic treatment than planktonic cells. This resistance has resulted in the pursuit for new ways to both deter the formation of biofilms and eradicate those that have already been established. This current work takes two approaches, in two very different environments, to accomplish these goals. The first chapters address the fouling of aviation fuels by Pseudomonas aeruginosa biofilms and introduces the use of bacteriophage as a method preventing such fouling. The latter portion of this work introduces a cationic porphyrin with the ability to prevent and remediate Pseudomonas aeruginosa and Staphylococcus aureus biofilms in the presence and absence of photoactivation and begins to suggest mechanisms for this activity. This porphyrin has the potential to be applied across a many fields including medicine and industry. Together these approaches begin to address the challenges posed by biofilms.

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

Biofouling and scaling are two major problems in the operation of reverse osmosis (RO) membranes and other equipment. A variety of control measures are employed in practice, including the use of electromagnetic fields (EMF), which can avoid the use of chemical antifouling agents (e.g. halogen-based biocides) that may be toxic to humans or the environment. This is a fairly recent and controversial technology and, from the available documentation and literature, it is clear that the scientific basis for its purported effectiveness is not yet firmly established. In particular, the various conditions under which EMF technologies are likely to be effective for real world applications have not been established. This thesis reviews and collates the relevant literature on the problem of scaling and biofouling in RO membranes and heat exchanger systems (e.g. cooling towers), with a particular focus on the application of pulsed EMF technologies, including the broad documentation, relevant scientific studies, proposed mechanisms of action and further research directions. This study confirms that a lot more systematic scientific research is needed in order to validate the application and commercialization of EMF technologies as a pretreatment method to control fouling and scaling in various applications including RO membrane systems. Therefore, a number of carefully controlled laboratory experiments have been designed and carried out in order to test the inherent anti-bacterial and anti-scaling claims for two commercially available pulsed electromagnetic field (PEMF) devices, that were demonstrated in this study to operate at ~ 100 kHz but with different waveforms. For example, these commercially available devices are currently being marketed and employed to ostensibly manage biofouling. Since the reliable application and industry acceptance of such technologies requires thorough scientific validation – and this is currently lacking, we have initiated proof-of-principle research in an effort to investigate whether such commercially available PEMF devices can influence the viability (culturability) of planktonic bacteria in a pure aqueous environment. Thus, these two devices were first investigated via a static (i.e. non-flowing) treatment system. ‘Healthy’ Escherichia coli cells, as well as cultures that were physiologically compromised by silver nano-particles, were exposed to the PEMFs from both devices under controlled conditions. Although relatively minor, the observed effects were nevertheless statistically significant and consistent with the hypothesis that PEMF exposure under controlled conditions may result in a decrease in cellular viability and culturability. Notably, it has also been observed that under certain conditions bacterial growth is actually stimulated. These studies were then extended to flow conditions and to include another microorganism, P. fluorescens. Thus, the effect of the electromagnetic fields generated by the two commercial devices on the bacterial culturability of E. coli and P. fluorescens under flow conditions has been contrasted with previous static results. Specifically, for P. fluorescens, one of the two devices showed no significant inhibitory effect under static conditions but showed significant inhibition under several flow conditions (low and high) and for different exposure times. For the other device, static conditions are actually stimulatory to growth. However, under low flow conditions, the effect is inhibitory and, under high flow conditions, is either inhibitory or stimulatory depending on exposure time. Also, the marketing and implementation of commercially available pulsed-electromagnetic field (PEMF) devices to, ostensibly, control scaling in processes such as reverse osmosis (RO) and cooling-tower installations, is based on the notion that such devices enhance the coagulation of inorganic particles such as calcium carbonate. In order to provide a scientific basis for these claims, the precipitation characteristics of calcium carbonate under the influence of the PEMFs from the two devices has also been investigated under controlled conditions. Thus, the rate and profile of calcium carbonate precipitation in the presence and absence of PEMF exposure of parent calcium nitrate and sodium carbonate aqueous solutions were tracked, in parallel, by UV absorption at 350 nm and by turbidity measurements. The morphology of the corresponding crystalline precipitates was also assessed using SEM. From these studies, is apparent that exposure of the parent solutions to the PEMF from one of these devices, but not the other, can influence both the profile of calcium carbonate precipitation and the morphology of the resulting microcrystals, consistent with enhanced particle coagulation. It is evident from these studies that PEMF induced anti-bacterial and anti-scaling effects depend on a wide range of variables such as waveform, extent of flow, type of bacteria and PEMF exposure duration. The effect of other parameters such as frequency, pH, temperature, other dissolved species etc. also need to be considered, but were not addressed in these studies. Our investigations suggest that the uncertainties, if not confusion, in this area are a result of the high level of complexity, due to the aforementioned wide range of possible variables. This can only be addressed by systematically conducting controlled experiments, along the lines of those reported here, in order to properly isolate the effects of all such variables. In particular, it is imperative to define the conditions under which such devices might be commercially viable.

The interactions between humans, the structures we build, and the microorganisms that inhabit these spaces are inescapable. Engineered ecosystems are classified broadly as any ecosystem built or managed by humans. Buildings and other infrastructure may corrode and fail as a result of microbial metabolism. Microbial fouling directly impacts fuel and water distribution systems. Microorganisms inhabiting surfaces in engineered ecosystems may also impact human health. Three engineered ecosystems; landfills, biodiesel storage tanks, and aircraft, were characterized as a part of this dissertation using a combination of small subunit ribosomal RNA sequencing, in situ measurements of microbial activity, cultivation, and laboratory experimentation. Landfills are one end point for the waste produced by humans and are of increasing concern due to the presence of chemicals of emerging concern. In order to better understand the role of microorganisms on the life cycle of landfills, it is important to characterize the microorganisms that inhabit landfill leachate and if the unique geochemical landscape of leachate impacts the microbial community composition. Landfill leachate microbiomes are distinct from many other engineered or natural ecosystems, possibly due to a combination of chemical and geographic parameters at each landfill. One drawback of the landfill leachate study was a lack of sampling events over time and our ability to cultivate microorganisms that may directly impact the operation of an engineered ecosystem. In collaboration with the United States Air Force (USAF) and the Air Force Research Laboratory, we investigated the extent of fuel fouling and material corrosion within B20 biodiesel storage systems at multiple USAF facilities over an eighteen-month survey. Bacterial and fungal communities were largely distinct at each sampled location although the abundant members of the fungal community were found at many sampled tanks. The risk to infrastructure through generalized corrosion was low; however, pitting corrosion was increased when associated with fungal biomass. The filamentous fungi found in underground storage tanks have the ability to degrade components of the fuel and increase the corrosion of metals, representing a risk to infrastructure. Information gathered in the in situ studies and laboratory experimentation described in this dissertation could help operators detect and assess the likelihood of biofouling and corrosion in B20 biodiesel blends. In many engineered ecosystems, including B20 underground storage tanks, the removal or mitigation of microorganisms is desirable. An opportunity arose to test the impact on the microbiome of a C-130H aircraft using a novel means of whole-aircraft decontamination. After 72 hours of decontamination with hot, humid air, the bacterial, archaeal, and eukaryotic community structure was significantly altered. Fewer viable microorganisms were cultivable after decontamination. The use of hot, humid air decontamination appears to be a viable method of decontaminating an entire aircraft. The use of hot, humid air may also be useful in other engineered ecosystems such as the B20 biodiesel storage tanks that contain undesired microorganisms. By using a combination of techniques that compliment one another, we have identified and isolated abundant members of the bacterial and fungal community that contaminate USAF B20, the risk they pose to infrastructure, and a potential means to controlling microbial communities in engineered ecosystems.

Polymers synthesized from renewable plant-based monomers are gaining importance since they reduce reliance on petroleum feedstocks. Cashew nut shell liquid, side-product of cashew nut is an excellent source of naturally derived phenols. Cardanol polymerization is catalyzed by soybean peroxidase has been carried in 2-propanol/phosphate buffer. Reaction proceeds at room temperature, standard pressure and avoids use of toxic organic solvents, such as benzene, a carcinogenic. The enzymatic polymerization route of synthesis is desirable for the environment and contributes to “green polymer chemistry.” In this study, polycardanol is used as a base material for an antifouling coating. This study discusses effects of different additives to study antifouling activities of cardanol-based polymeric coatings to inhibit attachment of Pseudomonas aeruginosa. Polycardanol has been modified with a fluoropolymer and lanthanum strontium ferrite to change surface properties and study its effect on initial attachment of Pseudomonas aeruginosa.

Biofouling, the accumulation of biomolecules and organisms to surfaces underwater, is a major problem to the government because it can result in damaged ship hulls, drag force that slows ships down, and higher cost for extra fuel consumption. Antifouling materials that can resist biofouling have great potential in a wide range of applications from the naval industry to biomedical engineering. Molecular level understanding of the surface structures of the antifouling materials is essential in revealing their antifouling mechanisms, which guides the design of new and effective antifouling materials. In this dissertation, sum frequency generation (SFG) vibrational spectroscopy has been used to probe the surface structures of various antifouling polymers in situ. The surface structures of the materials in water and the interfacial water structures were correlated to antifouling test results. Biocide modified polydimethylsiloxane (PDMS) coatings, amphiphilic polymers, and zwitterionic polymers were investigated. For the biocide modified PDMS coatings, the densely packed alkyl chains of the biocide molecules on the coating surface were found to be critical for antimicrobial activity. SFG spectroscopy also revealed the hydrophobic and hydrophilic surface structures of the amphiphilic polymers in air and in water, respectively, which affect their antifouling/fouling release properties. For zwitterionic materials, strong surface hydration was revealed as their nonfouling mechanism. The hydration of the zwitterionic materials is stronger than that of the poly(ethylene glycol) (PEG) materials in contact with proteins. In addition, zwitterionic materials with different molecular structures responded to pH and salts differently. Biofouling was also investigated as a model for underwater glue. The amino acid, 3,4-dihydroxyphenylalanine (DOPA), has been shown to facilitate mussel protein mixtures to adhere to surfaces underwater. Inspired by mussel adhesive proteins, DOPA containing adhesive polymers have been developed that match the performance of commercial glues. In this dissertation, the structures of a DOPA-containing adhesive polymer at various interfaces were examined and DOPA adhesion was found to be based on both non-covalent interactions and covalent bonding. Further, the interfaces between mussel adhesives and various substrates in water were probed in situ, which revealed surface dehydration as an important biofouling/bio-adhesion mechanism of real marine organisms.

Coastal seawater desalination using reverse osmosis (RO) membranes has the potential to alleviate water stress in arid regions. However, membrane biofouling, caused by bacterial biofilm formation, is a significant challenge for seawater desalination plants. Biofilm formation is regulated by quorum sensing (QS) pathways where bacteria secrete auto-inducer molecules to communicate with neighboring bacteria to activate biofilm formation. This research investigated the role of the QS system and the effect of QS inhibiting (QSIs) compounds on marine biofilm production and membrane biofouling. This study revealed that four different marine bacteria isolated from fouled RO membranes in a desalination plant produced two low molecular weight auto-inducer 1 (AI-1) QS molecules. Vanillin and cinnamaldehyde were then identified as the most effective QSI compounds with reduction of marine biofilm formed by RO membrane biofouling isolates and native uncultured seawater bacterial communities by more than 79% and 70%, respectively in a microtiter plate assay. Further investigation into the anti-biofouling capabilities of vanillin and cinnamaldehyde in a cross-flow membrane bio-monitoring system indicated that vanillin in the bulk fluid (1200 mg/L) significantly reduced extracellular polysaccharides (>40%) and dead cells (>20%) on the RO membrane surface. In order to improve the membrane in-situ anti-biofouling potential, vanillin and cinnamaldehyde were physically adsorbed onto various RO membrane surfaces. The addition of the QSI layer on the RO membrane surface significantly altered the membrane surface contact angle along with a less than 16% reduction in pure water permeability, but there was no significant change in salt rejection compared to unmodified membranes. Under biofouling conditions consisting of four mixed marine bacterial species in a high pressure RO system, QSI modified membranes experienced a minimal loss in permeate flux compared to unmodified membranes. Extracellular polysaccharide production, live cells, and dead cells were significantly suppressed on vanillin and cinnamaldehyde modified membrane surfaces by more than 15%, 58%, and 61%, respectively. These findings indicate that QSIs have the potential to suppress marine biofilm formation and membrane biofouling for seawater desalination.

Surface wettability (or surface hydrophilicity) is of considerable importance in a variety of applications, including membrane separations, lubrication, fibers (e.g., textiles), and biomedical applications. Alteration of surface wettability to the desired level can be of significant benefit in the above applications. Accordingly, the present study focused on a systematic investigation of the modification of surface hydrophilicity via the synthesis of hydrophilic surface tethered polymers. This approach to surface nanostructuring (SNS) was achieved by a two-step process, whereby surface activation is achieved using atmospheric pressure plasma (APP) followed by graft polymerization with a suitable vinyl monomer. The resulting polymer layer consists of chains that are terminally and covalently attached to the underlying surface, being polyamide in the present study. Polyamide (PA) was the selected substrate given the importance of this polymer in various applications (e.g., reverse osmosis (RO) membranes, clothing, body armor, etc.). The degree of surface hydrophilicity imparted to the PA surface was evaluated with respect to the conditions of APP surface activation (i.e., hydrogen, oxygen, and helium as plasma source gases, and exposure time) and graft polymerization (i.e., reaction time, 2-hydroxyethyl methacrylate, acrylamide, acrylic acid, n-vinylpyrrolidone, methacrylic acid, and vinylsulfonic acid monomers, and initial monomer concentration). Helium APP was found to be most effective for the synthesis of tethered polymers on the PA surface leading to an increase in hydrophilicity as quantified by a 15 – 51% reduction in the free energy of hydration (ΔGiw) of the underlying PA substrate. In particular, polymer-water affinity of the nanostructured PA surfaces, as quantified by the polar component of the surface energy, was a factor of 2.2 – 6.5 higher than for the native PA surface. Overall, surface hydrophilicity increased with increasing tethered polymer layer surface roughness, volume, and thickness; the above trend is consistent with the expected corresponding increased water sorption capacity by the grafted water soluble polymers.The hydrophilic polymer brush layer effectiveness in reducing biofouling propensity and improving surface cleaning post-biofouling (i.e., decreasing surface-solute affinity) was demonstrated for SNS-PA thin-film composite (TFC) RO membranes. SNS-PA RO membranes with polyacrylamide (PAAm), poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), and poly(vinylsulfonic acid) (PVSA) brush layers were synthesized, yielding permeability and salt (NaCl) rejection ranges of 4.8 – 6.7 L/m2∙h∙bar and 95.2 – 96.6%, respectively. Performance testing of the SNS-PA-TFC membranes was carried out using secondary wastewater from a municipal wastewater treatment (MWT) plant. Performance tests with the PMAA-SNS-PA and PAAm-SNS-PA membranes (highest and lowest ranking with regard to hydrophilicity, respectively) demonstrated measurable resistance to biofouling. Biofilm layer thickness was up to 4.7 times lower for the above SNS-PA membranes relative to a commercial TFC membrane of similar salt rejection. Moreover, up to 89% of the SNS-PA membrane permeability was recovered after water cleaning, and complete restoration of membrane permeability was attained after chemical (Na2∙EDTA) cleaning. In summary, the present approach for tailor-designing surfaces is effective for wettability control through adjustment of the brush layer topography and chemistry which affect the polymer-water affinity. Such hydrophilic tethered polymer surface layers can reduce the biofouling propensity of surfaces, and in particular, increase the biofouling resistance and improve cleaning efficiency of RO membranes.

Cost-effective purification and desalination of water is a global challenge. Reverse osmosis (RO), the current method of choice, requires high pressure drops across the membranes in order to achieve acceptably high flow rates. Conventional polymer membranes are limited in their performance by a trade-off between water permeability and water/salt selectivity. Biofilm fouling is another critical problem in RO applications. Recent simulations and experiments suggest that properly functionalized carbon nanotubes (CNTs) can be used to construct RO membranes that have high permeation flux as well as complete ion rejection, and that are resistant to biofilm formation. The objective of this research was to combine zwitterion-functionalized carbon nanotubes with traditional thin film polyamide (PA) to fabricate a novel desalination membrane which has both high permeability as well as selectivity. Zwitterion functional groups in CNTs act as molecular gatekeepers at the entrance of the nanotubes to enhance blockage for salt ions. Functionalized CNTs were oriented on a membrane support by high vacuum filtration. These oriented CNTs were sealed by a polyamide film via interfacial polymerization. Cross-sectional image of the nanocomposite membrane taken by scanning electron microscopy (SEM) showed semi-aligned zwitterion-CNTs on top of a porous support covered by a thin PA film with an overall thickness of approximately 250 nm. When the concentration of zwitterion-CNTs in the membrane increased, the nanocomposite membranes experienced significant improvement in permeation flux while the ion rejection increases slightly or remains unchanged. This indicated that the increased water flux is not due to an increase in nonspecific pores in the membrane, but rather due to an additional transport mechanism resulting from the presence of the functionalized CNTs. Significant increase of flux was also observed in separating cations other than sodium. The separation of the PA skin layer dominated the ion rejection mechanism by size exclusion even when the carbon nanotubes were introduced into the polyamide coating. The zwitterion functional groups exposed at the membrane surface also interacted with the feed water to form a strong hydration layer, which results in improved surface biofouling resistance. The adsorption rate of protein foulants on the nanocomposite membrane surface was significantly reduced compared to the control membrane without CNTs, and the adsorbed fouling layer could be easily removed by flushing with water. After washing, the nanocomposite membrane recovered 100% of the decreased water flux whereas the control membrane only recovered 10% of the decreased flux resulting in a permanent loss of 30% in water permeation. We have therefore demonstrated that advanced materials like CNTs can be synthesized with desired functional groups, and can be embedded into traditional RO membranes to simultaneously resolve the challenge of low flux and surface fouling in the current desalination process.

Aquatic biofouling can be a problem issue in the aquaponics industry. The growing of both plants and fish in a linked system provides a unique challenge to growers due to high nutrient loads, which can lead to increased biofilm growth within a system. A new surface technology, named Sharklet™, uses small microscopic ridges to prevent marine biofouling. The surface, named due to its mimicry of shark skin, was designed because of a shark's unique ability to not accrue marine organisms on its skin. Sharklet™ technology was designed to alleviate the problem of aquatic biofouling on maritime ships, but due to cost constraints and user interest, may not be able to solve this issue in freshwater aquaponics systems. In this study, the ability of Sharklet™ to retard biofilm growth in freshwater greenhouse mesocosms was compared to aluminum, fiberglass, plexiglass, PVC, and tile. Sharklet™ performed well in high flow conditions, supporting less biofilm growth than tile and aluminum in non-flow conditions. However, in non-flow conditions it no significant differences were observed. In phone interviews, respondents from the aquaponics and hydroponics community felt that a material like Sharklet™ would be easy enough to install, but had too high of a cost to be effective for the average aquaponics user.

Biofouling in membrane technologies accounts for up to 50% of operational costs; its main effects include flux decline, increased required pressure, expensive pretreatment requirements, cleaning-related production interruptions and accelerated membrane replacing. Despite the efforts, current biofouling control strategies, such as feed water disinfection and chemical cleaning have not entirely solved the problem. Therefore, new approaches are being developed. Since biofouling is a biofilm based phenomena, which starts from an initial reversible bacterial adhesion, followed by irreversible attachment, cell reproduction and finally biofilm formation; it is hypothesized that preventing the initial bacterial adhesion would stop biofouling. This research exploits this idea by creating cross-linked polyvinyl alcohol (PVA) coating films with low bacterial adhesion propensity, which are subsequently embedded with antibacterial cation-exchanged zeolites (LTA), forming antibacterial nanocomposites able to inactivate bacteria from replication. A combinatorial array of PVA films and nanocomposites were prepared with varying degree of polymerization, hydrolysis and cross-linking, as well as, different cross-linking agents, zeolite loadings and antibacterial ion utilized. Then, model bacteria reversible-irreversible adhesion and inactivation rates were analyzed, utilizing a high throughput based assay, in several aquatic matrices. Determined free energy of adhesion and cohesion showed that most PVA films were hydrophilic and had low propensity to bacterial adhesion. Less cross-linked PVA films prepared from less hydrolyzed PVA produced more adhesion resistant films. PVA molecular weight or cross-linking agent did not affect significantly the outcomes. Overall, the bacterial attachments decreased with increasing free energies, but correlations were low because of large adhesions variability. This leaded to concluded that physical heterogeneity of the films, like nanoscale features formation, were significant in the biofouling propensity. The effect of embedded zeolites on bacterial adhesion varied with the type of antibacterial ion and zeolite loads. Nanocomposites with Ag-LTA (10%) or Zn-LTA and the combined AgCuZn-LTA had lower irreversible adhesion than corresponding PVA films. While, Cu-LTA worsened the antiadhesive properties, because of a higher surface roughness and a higher rate of inactivation; that left more dead cells, which are more prone to adhesion, on the nanocomposite surface. Overall, irreversible adhesions correlated more strongly with surface roughness than free energy of adhesion.

The NSF Generation-3 Engineering Research Center for Revolutionizing Metallic Biomaterials was launched in September 2008 and is formed by research groups at three national universities and one research group at the Hannover Medical School in Germany as a global partner. The ERC proposed “to develop the fundamental knowledge and technology needed to advance biocompatible and biodegradable metal-based (especially Mg) implantable systems with feedback control for reconstruction and regeneration”. More specifically these technologies will be used to develop craniofacial and orthopedic applications, cardiovascular and thoracic devices, and responsive biosensors and neural applications. Although metals have been used as internal fixtures to aid healing of fractured bones and tissue for more than 100 years, biodegradable metallic implant materials have gained increasing interest over the past years in the orthopedic and biomedical engineering field, as they exhibit unique properties that could potentially outperform currently used permanent implant materials. Today’s commonly used implant materials for orthopedic applications are stainless steel, titanium alloys and cobalt-chromium-based alloys, and are intended to permanently remain in the body unless they are removed by a secondary surgery. However, these materials have been reported to cause problems such as stress shielding or the release of toxic metal ions through corrosion, which can lead to infections or allergies. To develop biodegradable metallic implant materials, many researchers are focusing on magnesium and its alloys as their unique properties, which include physical and mechanical properties close to bone, make them promising candidates for biodegradable implants. Furthermore, these materials are generally non-toxic, lightweight and corrode rapidly in aqueous environments. During this corrosion, magnesium is oxidized to magnesium ions, as water is reduced to hydrogen and hydroxyl ions. The research presented here is mainly focused on the detection of hydrogen gas to assist in the analysis of the corrosion of magnesium and its alloys in aqueous solutions as well as in in vitro and in vivo systems. Different types of hydrogen sensors and commonly used hydrogen monitoring techniques used during magnesium corrosion are discussed. A novel and simple potentiometric hydrogen sensor was demonstrated and compared to a commercial amperometric hydrogen sensor to monitor dissolved hydrogen during magnesium alloy corrosion. This potentiometric sensor was integrated in an electrochemical corrosion characterization system to monitor the corrosion of magnesium samples in different aqueous solutions. The system was tested with three different aqueous solutions and showed that it added valuable information to common immersion corrosion tests. The corrosion characterization system was then partially transferred to static and dynamic in vitro systems to monitor the corrosion behavior of magnesium samples under cell culture conditions and in the presence of proteins. Through an in vivo study the hydrogen concentration and gas composition of subcutaneous gas cavities formed during magnesium alloy corrosion were measured, disproving a common misbelieve that these cavities only contain hydrogen gas. Finally, it was shown that potentiometric measurements are not as sensitive to biofouling as it would occur within hours after exposure to biological samples (e.g. cell culture media, serum) than voltammetric measurements.

The research presented in this dissertation provides the results of a comprehensive assessment of the water treatment requirements for the City of Sarasota. The City’s drinking water supply originates from two sources: (1) brackish groundwater from the Downtown well field, and (2) Floridan surficial groundwater from the City’s Verna well field. At the time the study was initiated, the City treated the brackish water supply using a reverse osmosis process that relied on sulfuric acid for pH adjustment as a pretreatment method. The Verna supply was aerated at the well field before transfer to the City’s water treatment facility, either for softening using an ion exchange process, or for final blending before supply. For the first phase of the study to evaluate whether the City can operate its brackish groundwater RO process without acid pretreatment, a three-step approach was undertaken that involved: (1) pilot testing the plan to reduce the dependence on acid, (2) implementing the plan on the fullscale system with conservative pH increments, and (3) continuous screening for scale formation potential by means of a “canary” monitoring device. Implementation of the study was successful and the annual savings in operating expenditure to the City is projected to be about $120,000. From the acid elimination study, using the relationship between electrical conductivity in water and total dissolved solids in water samples tested, a dynamic approach to evaluate the performance of the reverse osmosis plant was developed. This trending approach uses the mass transfer coefficient principles of the Homogeneous Solution Diffusion Model. Empirical models iv were also developed to predict mass transfer coefficients for solutes in terms of total dissolved solids and sodium. In the second phase of the study, the use of nanofiltration technology to treat aerated Verna well field water was investigated. The goal was to replace the City’s existing ion exchange process for the removal of hardness and total dissolved solids. Different pretreatment options were evaluated for the nanofiltration pilot to remove colloidal sulfur formed during pre-aeration of the groundwater. Sandfilters and ultrafiltration technology were evaluated as pretreatment. The sandfilter was inadequate as a pre-screen to the nanofiltration pilot. The ultrafiltration pilot (with and without a sandfilter as a pre-screen) proved to be an adequate pretreatment to remove particulates and colloids, especially the sulfur colloids in the surficial groundwater source. The nanofiltration pilot, was shown to be an efficient softening process for the Verna well field water, but it was impacted by biofoulants like algae. The algae growth was downstream of the ultrafiltration process, and so chlorination was used in the feed stream of the ultrafiltration process with dechlorination in the nanofiltration feed stream using excess bisulfite to achieve stable operations. Non-phosphonate based scale inhibitors were also used to reduce the availability of nutrients for biofilm growth on the nanofiltration membranes. The combined ultrafiltration-nanofiltration option for treatment of the highly fouling Verna water samples is feasible with chlorination (to control biofouling) and subsequent dechlorination. Alternatively, the study has shown that the City can also more economically and more reliably use ultrafiltration technology to filter all water from its Verna well field and use its current ion exchange process for removal of excess hardness in the water that it supplies

To address drinking water quality concerns, membrane separation technologies have been developed, resulting in the continuous reduction of their cost and rapid extension of their application possibilities. Despite the remarkable advantages of membrane separation technologies, the drastic reduction of water flow due to membrane fouling and the high cost of membrane replacement pose a significant problem in water separation applications. This research investigated the impact of feed water characteristics (i.e., conductivity and pH), conditioning layer formed on biofilms, and presence and activity level of a biofoulant on the membrane-solute interaction forces (i.e. hydrophobic attraction) and membrane morphology. Experiments were performed on cellulose acetate ultrafiltration (CAUF) membranes (MWCO 20,000 D) in crossflow filtration for up to 53 hours. Fouled membrane characterization from the macro- to nano-scale was effectively carried out using existing and emerging techniques including fluorescence microscopy for cell activity, image analysis for biofilm surface coverage and intensity, ATR-FTIR for biofilm chemical composition, AFM for fouled membrane surface roughness and skewness, and CFM for its relationship to adhesion forces. As the feed water conductivity increased and the membrane surface roughness increased, the magnitude and range of the adhesion force increased and, subsequently, the permeate flux decline increased suggesting that feed water chemistry impacted membrane potential for fouling. Comprehensive biofilm characterization, specifically AFM, revealed that bacterial cells deposited, and then formed a consolidated biofilm, on the low shear rate areas of the membrane surface. And, as expected, the rate of biofilm formation was higher in the presence of a carbon source and active cells. Additional experiments were carried out to determine the contribution of abiotic fouling (conditioning layer) to cell activity and built up resistance on CAUF membranes. Regardless the degree of abiotic fouling, biotic fouling contributed most significantly to permeate flux decline. However, in the presence of active cells, abiotic fouling supported biotic fouling, by acting as a food source. This research used and modified emerging biofilm characterization techniques to better understand the causes of biofilm formation and its impact on the water filtration performance of CAUF membranes given varied feed water characteristics.

Implementation of nanofiltration (NF) and reverse osmosis (RO) processes in treating traditional water sources can provide a steady-state level of removal that eliminates the need for regeneration of ion exchange resins or granular activated carbon. Moreover, RO can help meet future potable water demands through desalination of seawater and brackish waters.The productivity of membrane filtration is severely lowered by fouling, which is caused by the accumulation of foreign substances on the surface and/or within pores of membranes. Microbial fouling, or biofouling, is the growth of microorganisms on the membrane surface and on the feedspacer as present between the envelopes. The fouling of membranes has demanded and continues to demand considerable attention from industry and research communities. Many of these applications use membranes in a spiral wound configuration that contains a feed spacer. The goal of this project was to develop low-biofouling polypropylene (PP) spacers through the functionalization of PP by a spacer arm with metal chelating ligands charged with biocidal metal ions, investigate the use of this metal-charged polypropylene (PP) feedspacers that target biofouling control, and to use some traditional and one novel techniques to autopsy the membranes after filtration to gain a better understanding of the biofouling mechanism and how the modified spacers are affecting it.

Membrane filtration is an effective technique used in water treatment to remove particles, organic pollutants, inorganic compounds, and microorganisms to accomplish a biologically safe and consistently high quality drinking water. One significant challenge to membrane separation technologies is membrane fouling causing pressure drop, flux decline and eventually significant cost of membrane replacement. Specifically, membrane biofouling is considered a major problem due to the capabilities of microorganisms to adapt their growth rate, multiply, and relocate even if they were 99.99% removed from the feed stream. The objective of this research was to determine the impact of metabolic activity of the pure culture of biofoulants on the membrane biofilm metabolic activity, biofilm formation rate, and operational flux decline.In this study, the metabolic activity of Pseudomonas fluorescens in active, inactive, and different growth phases were investigated during cross-flow filtration using a cellulose acetate ultrafiltration (UF) membrane at different sampling times (4, 11, and 24 hours) of filtration. In accordance with previous biofilm studies, ATP was used to determine the metabolical activity of the biomass. Dehydrogenase activity assessment of the membrane biofilm using CTC was also carried out on intact biofilms. Our results showed that after 10-12 hours of filtration, the biofilm ATP levels reach an equilibrium concentration (avg. 8 amol/cell) and do not appear to be related to biofoulant ATP levels from cells harvested in the late exponential growth phase regardless of initial ATP level. However, the bacterial growth phase affected the ATP activity of cells. Membrane biofilms formed from biofoulants in the lag and stationary phase of growth contained similar levels of ATP (avg. 1.8 amol/cell), and the exponential phase cells resulted in significant higher activity. Flux decline does not appear to be related to metabolic activity of the biofoulant or biofilm following 24 hours of filtration. Notably, there was much less (ca. 2.5%) flux decline when the biofoulant cells were inactive. Since metabolic activity determines the substrate conversion rate and the biofilm growth rate, the knowledge of the metabolic activity of the biofoulants and membrane biofilm is essential for understanding the biofilm accumulation mechanism for applying appropriate countermeasures to control membrane biofouling.

The nanoporous PCL membranes were prepared via the combination of thermally- and nonsolvent-induced phase separations. For the phase separation process, nonsolvent has significant effect on pore formation and drug release rate. In nonsolvent-induced phase separation, a large amount of nonsolvent was added to casting solutions in order to improve pore connectivity within the membrane. The use of a Teflon plate for membrane casting can result in uniform nanoporous membranes and consistent lysozyme diffusion. Pore connectivity was improved significantly when coagulation bath temperature was lowered. By using a 5°C water coagulation bath in the wet-process precipitation, the average pore size reduced from 90 nm to 55 nm while increasing the casting solution concentration from 15 wt% to 25 wt% PCL. Thus, by varying the polymer concentration of the casting solution, the lysozyme release rate can be manipulated with precise control. The potential application of nanoporous PCL membranes to achieve the preferable zero-order release rate is demonstrated in this dissertation.Along with achieving the zero-order release rate, the nanoporous PCL membranes also provide immunoprotection for cell-based therapies/devices. Immunoisolation can be achieved by preventing Immunoglobulin G (IgG) from diffusing through the nanoporous PCL membranes. With appropriate pore size, the nanoporous PCL membranes can allow the diffusion of therapeutic agents (lysozyme) and block the diffusion of immune molecules (IgG). The application of the nanoporous PCL membranes to cell-based therapies/devices is also demonstrated in this dissertation.Extensive fibrosis induced by the healing process can be detrimental to the long-term performance of implantable applications. The prevention of fibroblast adhesion to the nanoporous PCL membrane surface is crucial for constant and well controlled drug release. This study shows a novel method to modify the nanoporous PCL membrane surface with poly(ethylene glycol) (PEG) . To achieve this goal, oxygen plasma and PEG(400) monoacrylate were used to graft the PEG onto the membrane surface through covalent bonding. Initially, various plasma treatment conditions were investigated to optimize the PEG-grafting quality and to achieve minimum fibroblast adhesion. After the treatment, water contact angle measurements and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra confirmed that PEG was successfully grafted onto the PCL membrane. X-ray photoelectron spectroscopy (XPS) revealed that different plasma powers and treatment times can change the surface composition of membranes. Cell adhesion and morphology studies indicate that either lower plasma power or shorter treatment time is able to significantly improve resistance to cell adhesion. With the use of appropriate plasma treatment conditions, the effects of grafting density and PEG chain length on reducing fibroblast adhesion were also investigated in this study. PEG-diacrylates were also investigated for their influence on fibroblast adhesion. For PEG-diacrylates, increasing molecular weight can lead to a higher resistance against cell adhesion. However, PEG-diacrylates were not as effective as PEG(400)-monoacrylate for providing the resistance to cell adhesion.

Microbial biofilm formation on surfaces leads to significant losses in terms of energy,equipment damage, product contamination, medical infections, etc. and also raisesserious environmental concerns. To prevent formation of biofilms, a detailedinvestigation into the initial stage of bacterial attachment was conducted using three typesof bacterial species; Pseudomonas aeruginosa PAO1, Escherichia coli and Pseudomonasputida.Several approaches were evaluated and finally a reproducible procedure was adopted tostudy initial bacterial attachment. The procedure primarily involved monitoring andcounting the number of attached cells on the glass walls of the flow chambers, throughwhich a bacterial suspension was circulated and, subsequently, saline was passed forwashing to remove loosely attached cells. Preliminary investigations in terms of fluidflow behaviors, consistency check, and the effect of various factors including theattachment locations within the chamber, on the attachment results were conducted priorto employing the flow chamber systems to study the initial bacterial attachment. Usingthe flow chambers systems, the effects of chamber wall shear, medium pH, chamber, andtwo potential antifoulants, Zosteric acid and Rhamnolipids, on attachments wereexamined.The three bacterial species used showed similar behavior (peaking at different shearstress values) in response to varying shear conditions in their environment. Theantifouling properties of zosteric acid were not convincing enough, however promisingresults were seen while studying rhamnolipids in the case of all three bacterial strains.The effect of other factors like pH, presence of zosteric acid impurities, surfaceconditioning were also explored. These conditions however proved to have no effect onthe initial bacterial attachment but provided useful information for future studies.

ABSTRACT The focus of this study was to understand and evaluate the effect of noradrenaline (NA) on two prominent fouling marine invertebrates, the Eastern Oyster, Crassostrea virginica and the Striped Barnacle, Balanus amphitrite for the purpose of developing a novel fouling deterrence strategy. To understand the effect of NA at a cellular level the immune cells (hemocytes) of C. virginica were chosen as representative molluscan cells. Upon stimulation with 10 micro-molar of noradrenaline ~4% hemocytes of C. virginica labeled positive for the beta-adrenergic receptor (beta-AR). Upon NA stimulation the beta-AR positive cells formed cell-cell synapses and apoptosis was detected in ~50% of the hemocyte population. NA induced apoptosis was followed from the earliest onset to the terminal stages, from the release of cytochrome-c to the DNA degradation. Electric cell substrate impedance measurements suggested that NA stimulation induced cytoskeletal changes in the hemocytes. SDS PAGE and Western analysis corroborated the presence of beta-AR on NA stimulated hemocytes. Mass spectral analysis of the receptor protein revealed that the putative hemocyte beta-AR has a 30% sequence identity to the human beta-AR. Effect of NA on the settling behavior of B. amphitrite cypris larvae was evaluated by challenging the larvae with micromolar concentrations of NA ranging from 30-100 micro-molar. The noted searching behavior of cypris larvae was lost after NA challenge and the larvae failed to cement to the substratum. ~70% of the NA treated larvae failed to settle and cement. NA treatment caused a considerable delay in cyprid-adult metamorphosis. Metamorphosed juvenile barnacles were observed 96 hours following NA treatment, whereas the control cyprids metamorphosed within 24-48 hours. In the cyprids-adult metamorphosis remnants of the cyprid stage were observed up to 48 hours of development. Metamorphosed juvenile barnacles appeared normal from the presence of growth increments and beating of cirri. NA challenge seemed to promote metamorphosis to juveniles forgoing the settling behavior and cementation to the substratum. To assess the applicability of NA as a fouling deterrent, NA molecules were covalently conjugated to HEMA (2-hydroxyethyl methacrylate) and MAA (methacrylic acid) polymer surfaces. Ability of covalently conjugated NA molecules to activate their target adrenoreceptors was assessed by understanding the effect of NA-conjugated polymer surfaces on hemocytes of C. virginica. NA conjugated polymer surfaces induced apoptosis in the hemocytes of C. virginica. Annexin-V assay confirmed the initiation of apoptosis. Cytoskeletal structure of the hemocytes adhering to NA-conjugated polymer surfaces displayed pronounced degradation. Apoptotic blebbing of plasma membrane was also observed using scanning electron microscopy. Control polymer surfaces failed to exert any deleterious effects on the hemocytes. Based on the results obtained in this study a novel fouling deterrence strategy is discussed.

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.

Membrane bioreactors (MBRs) are promising technology for ground based wastewater treatment. Recently, MBRs are also being considered to be used as a component in the integrated water recovery system for long duration manned space missions. For long term manned space travel, the major operational problem for MBRs is membrane biofouling. The current research studied the influence of MBR loading/decanting patterns on membrane biofouling. The central hypothesis of this study was: MBR loading/decanting patterns could lead to different sludge properties resulting in different level of membrane biofouling. To test the central hypothesis, experiments covered the following aspects of MBRs treating synthetic Early Planetary Base Wastewater (EPBW) were carried out: 1) organic removal and nitrification performance; 2) influence of MBR loading/decanting patterns (continuous mode vs. batch mode) on sludge properties; 3) influence of MBR loading/decanting patterns on microbial community structure of the planktonic biomass; 4) influence of MBR loading/decanting patterns on membrane filtration characteristics; and 5) the potential pioneer species that could attach to membrane surface in cross-flow microfiltration. The results of this study suggested that 1) MBRs is a promising process as the preliminary treatment of the synthetic EPBW by showing excellent organic removal and nitrification; 2) MBR loading/decanting patterns impact the chemical/physical properties as well as the microbial community structure of the planktonic (suspended) biomass. Particularly, the physical/chemical properties of the sludge in the MBR with batch mode could result in less membrane fouling; 3) Sludge in the MBR with batch loading/decanting correlated with less membrane fouling in both cross-flow and submerged filtrations; and 4) Specific microbial populations could be pioneers that firmly attach to microfiltration membranes at the initial stage of membrane biofouling. The findings of the current study provided novel information on the treatment of EPBW by using MBR technology that could also be used for the design and operation of MBRs for ground-based high strength wastewater treatment. More importantly, the results of this research suggested that the loading/decanting operation of the bioreactor components of MBRs could lead to different levels of membrane biofouling. Future design and operation of MBRs, for both long duration manned space mission and ground-based applications, should consider the operating condition of the bioreactor to further reduce the cost and enhance the stability of MBRs. As one of the early steps towards the mechanisms of membrane biofouling, molecular analysis suggested that specific microbial populations could be responsible for the initiation of membrane biofouling. This result could be an important connection between engineering and microbiological research for biofilm/biofouling formation.

The objective of this study was to test the hypothesis that the operating conditions of bioreactors influence the structure of the microbial community leading to differences in irreversible membrane biofouling. A traditional membrane bioreactor (MBR) system was divided into two experimental unites. Unit One, the bioreactor component, was used to generate sludges with different properties by adopting different configurations and operating conditions. Unit Two, the membrane flow cell, was used to test biofouling by using the sludges from Unit One. Mixed liquor was removed from Unit One, and membrane biofouling was examined in a membrane flow cell (Unit Two) with microfiltration and ultrafiltration membranes operated at tangential surface velocities of 0.1 m/s and 3.5 m/s. Amplified Ribosomal Deoxyribonucleic acid Restriction Analysis (ARDRA) and 16S rDNA sequence analyses were used to identify predominant bacterial populations within the mixed liquor and on the surface of biofouled microfiltration membranes operated at tangential surface velocities of 3.5 m/s. Community diversity and evenness were calculated to help describe the properties of the microbial community structure. The structure of the bacterial community in the four bioreactors was highly varied during the course of the experiment. The bioreactors with PFR configuration tend to demonstrate a lesser degree of irreversible biofouling. This trend would need to be verified by further membrane filtration analysis. The bioreactors employing membrane filtration to achieve solids separation demonstrated a greater degree of irreversible biofouling as compared to the systems operated with gravity sedimentation, suggesting that the lack of selective pressure by sedimentation in integrated membrane bioreactor systems may produce an increased tendency for biofouling. The predominant bacterial populations identified in the mixed liquor were significantly different as compared to the predominant bacterial populations identified on the surface of biofouled microfiltration membranes suggesting that the presence of certain bacterial populations may produce an increased tendency for biofouling. The results of this study supported our hypothesis and further suggested that future designs for membrane bioreactor systems should consider the relationships among microbial ecology and irreversible biofouling with regard to bioreactor operating conditions.

The marine surface-associated bacterium Pseudoaltermonas tunicata, produces a range of compounds that inhibit fouling organisms, including invertebrate larvae, bacteria, algal spores and fungi. In addition to these antifouling compounds P. tunicata cells produce both a yellow and a purple pigment. The aim of this study was to further characterise the antifouling activities, their regulation and relationship with pigmentation, and the ecological significance of P. tunicata and related organisms. It was discovered that the anti-algal compound was extracellular, heat sensitive, polar and between 3 and 10 kDa in size. The anti-fungal compound was found to be the yellow pigment and active against a wide range of fungal and yeast isolates. Chemical analysis suggests that this compound consists of a carbon ring bound to a fatty-acid side chain. Genetic analysis supports the chemical data for the active compound as a mutant in a gene encoding for a long-chain fatty-acid CoA ligase was deficient for anti-fungal activity. To address the regulation of antifouling compounds and their relationship to pigmentation transposon mutagenesis of P. tunicata was performed. Mutants lacking the yellow pigment displayed a reduced ability to inhibit fouling organisms. Further analysis of these mutants identified genes involved with the synthesis and regulation of synthesis of pigment and antifouling compounds. One of these mutants was disrupted in a gene (wmpR) with similarity to the transcriptional regulators ToxR from Vibrio cholerae and CadC from Escherichia coli. Analysis of global protein expression using two-dimensional gel electrophoresis showed that WmpR is essential for the expression of at least fifteen proteins important for the synthesis of fouling inhibitors. The ecological significance of antifouling bacteria was addressed by assessing the antifouling capabilities of a collection of bacteria isolated from different marine surfaces. Overall, isolates from living surfaces displayed more antifouling traits then strains isolated from non-living surfaces. Five dark-pigmented strains originating from the alga Ulva lactuca were further studied. Phylogenetic and phenotypic analysis revealed that they were all members of the genus Pseudoalteromonas and were closely related to P. tunicata. Two strains represented a novel species within the genus and were taxonomically defined as P. ulvae sp. nov.