The majority of state-of-the-art polymeric membranes for industrial or medical applications are fabricated by phase inversion. Complexation induced phase separation (CIPS)—a surprising variation of this well-known process—allows direct fabrication of hybrid membranes in existing facilities. In the CIPS process, a first step forms the thin metal-rich selective layer of the membrane, and a succeeding step the porous support. Precipitation of the selective layer takes place in the same solvent used to dissolve the polymer and is induced by a small concentration of metal ions. These ions form metal-coordination-based crosslinks leading to the formation of a solid skin floating on top of the liquid polymer film. A subsequent precipitation in a nonsolvent bath leads to the formation of the porous support structure. Forming the dense layer and porous support by different mechanisms while maintaining the simplicity of a phase inversion process, results in unprecedented control over the final structure of the membrane. The thickness and morphology of the dense layer as well as the porosity of the support can be controlled over a wide range by manipulating simple process parameters. CIPS facilitates control over (i) the thickness of the dense layer throughout several orders of magnitude—from less than 15 nm to more than 6 μm, (ii) the type and amount of metal ions loaded in the dense layer, (iii) the morphology of the membrane surface, and (iv) the porosity and structure of the support. The nature of the CIPS process facilitates a precise loading of a high concentration of metal ions that are located in only the top layer of the membrane. Moreover, these metal ions can be converted—during the membrane fabrication process—to nanoparticles or crystals. This simple method opens up fascinating possibilities for the fabrication of metal-rich polymeric membranes with a new set of properties. This dissertation describes the process in depth and explores promising applications: (i) catalytic membranes containing palladium nanoparticles (PdNPs), (ii) antibiofouling tight-UF membranes containing silver chloride (AgCl) crystals, and (iii) palladiumrich PBI hollow fibers for H2 recovery.

Membrane-based filtration technologies have seen rapid inclusion in a variety of industrial processes, especially production of drinking water by desalination. Biological fouling of membranes is a challenge that leads to increased costs from efficiency reductions, membrane damage, and ultimately, membrane replacement over time. Such costs can be mitigated by monitoring and optimizing cleaning processes for better prognosis. A fluorescence-based sensor for early biofouling detection capable of measuring extracellular enzyme activity was developed. The selected fluorogen and fluorogen-substrate were characterized and down selected by in vitro screening for compatibility in seawater and profiled over relevant Red Sea desalination parameters (pH and temperature). ATP measurements are currently regarded as start-of-the-art when assessing biomass accumulation in membrane-based filtration systems Therefore, the fluorescence sensor response was measured for a range of bacterial concentrations and validated using an ATP assay. We demonstrate the efficacy of the proposed approach for the quantitative assessment of bacteria activity in seawater rapidly and sensitively. Following in vitro testing, the method was employed in a lab-scale seawater reverse osmosis (SWRO) system for suitability in monitoring biofouling formation. The sensor successfully measured bacterial biomass accumulation rapidly and non-invasively using exogenously applied fluorogen-substrates. The sensor response was corroborated with real-time in situ non-destructive imaging of the membrane surface. This approach demonstrates the practicality of prototyping an early-detection biofouling sensor in membrane based processes using extracellular enzyme activity as a measure of bacterial abundance.

Water scarcity is an issue faced across the globe that is only expected to worsen in the coming years. We are therefore in need of methods for treating non-traditional sources of water. One promising method is desalination of brackish and seawater via reverse osmosis (RO). RO, however, is limited by biofouling, which is the buildup of organisms at the water-membrane interface. Biofouling causes the RO membrane to clog over time, which increases the energy requirement of the system. Eventually, the RO membrane must be treated, which tends to damage the membrane, reducing its lifespan. Additionally, antifoulant chemicals have the potential to create antimicrobial resistance, especially if they remain undegraded in the concentrate water. Finally, the hazard of chemicals used to treat biofouling must be acknowledged because although unlikely, smaller molecules run the risk of passing through the membrane and negatively impacting humans and the environment. It is, therefore, integral to investigate techniques for prevention of biofouling and removal of mature biofilms that are effective, less damaging to the membrane, and safe for humans and the environment. A common experimental setup is biofilm antimicrobial microdilution susceptibility tests. To acquire meaningful data from these tests, however, appropriate organisms must be tested. Manuscripts 1 investigates, via semi-systematic reviews, the question of what organisms are appropriate to represent the complexity of a biofilm in antimicrobial tests. Ultimately, we recommend utilizing the model biofilm-forming, pioneer organism, Pseudomonas aeruginosa for these studies. Biofouling studies also must present data in a useful manner to the many disciplines that are interested in preventing or removing biofouling. Our goal is to investigate both via antimicrobial microdilution susceptibility tests. In Manuscript 2 we investigate the metrics of each discipline with an interest in anti-biofouling studies. Ultimately we recommend utilizing both crystal violet stain to assess total biomass removal and the LIVE/DEAD BacLight stain to assess cell vitality (including log reduction and MIC, BPC, MBIC, MBC, BBC, and MBEC), to satisfy the metrics of all interested disciplines. Finally, in Manuscript 3 we implement the recommendations from Manuscripts 1-2 for biofilm prevention and biofilm removal antimicrobial microdilution susceptibility tests. In this manuscript, we work with a subset of safer preservatives including, methylisothiazolinone, phenoxyethanol, and sodium benzoate. We found that methylisothiazolinone was the most effective antimicrobial, however, it was not the safest. Additionally, we investigated the relationship between MBIC and BPC, which was found to vary between the preservatives. Ultimately, we have provided recommendations for biofilm antimicrobial susceptibility tests that produce widely applicable and useful metrics, as well as utilized these recommendations to investigate the efficacy of safer antimicrobials. All of this work provides a framework for which even safer and effective novel antimicrobials can be investigated. / Graduate / 2021-07-22

<p> Heavy metals, especially arsenic, have become a hot research topic due to their high toxicity and low removal efficiency in drinking water. Biofouling is one of the main factors affecting the removal efficiency of point-of-use (POU) water filtration systems. However, limited information is available on the effect of biofouling on heavy metal removal by POU systems. The aim of this study was to investigate how biofouling affects the removal efficiency of heavy metals,  especially arsenic, by different POU systems. Daily water use patterns in the U. S. households were simulated under laboratory conditions for the operation of POU systems. Sodium acetate was added to tap water to simulate an assimilable organic carbon source that contributes to biofouling formation and the concentration of sodium acetate gradually increased from 100 μg/L to 400 μg/L.  Sodium meta-arsenate (100 μg/L) was added to tap water to test its removal efficiency by POU  systems. Biofouling development and metal removal efficiency were monitored and correlated.  The results showed that arsenic removal efficiency and biofouling were positively correlated in both the activated carbon (AC) and reverse osmosis (RO) POU systems. Other conditions, such as temperature and flow rate, were negatively correlated with metal removal efficiencies in both systems. Overall, biofouling has been shown to contribute to improved removal efficiency of arsenic by POU, and the promotion effect was more significant in AC systems than in RO systems.  The results may contribute to an improved understanding of the maintenance of POU systems for heavy  metal removal </p>

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

Bugula neritina is a sessile marine bryozoan with a pelagic larval stage. Larvae frequently settle on boat hulls, facilitating the introduction of B. neritina to bays and estuaries worldwide. Adrenergic agonists, such as the vertebrate hormone noradrenaline, inhibit larval settlement in a variety of marine invertebrate species, including B. neritina. Light also inhibits B. neritina larval settlement, yet the underlying mechanisms by which light and adrenergic compounds exert their effects on larvae are not well understood. Octopamine is considered the invertebrate analog of noradrenaline, and may be an endogenous hormone involved in larval settlement pathways. I observed the effects of the adrenergic agonist noradrenaline and the adrenergic antagonist phentolamine on larval settlement, and found that high concentrations of noradrenaline increased larval mortality, inhibited larval attachment, and increased larval swimming behavior. High concentrations of phentolamine also increased larval mortality, but increased larval attachment and decreased larval swimming behavior. I used fluorescent labeling and microscopy to localize sensory system components, and found that larvae possess adrenergic-like receptors, as well as tyrosine hydroxylase-like and octopamine-like immunoreactivity. I also exposed larvae to phentolamine in both dark and light conditions, and found that light significantly inhibited larval attachment, but phentolamine blocked those inhibitory effects. These results suggest that B. neritina larvae possess adrenergic-like receptors, which serve as the binding sites for noradrenaline and phentolamine. These are likely octopamine receptors, and octopamine may be one endogenous compound involved in controlling larval phototaxis and settlement behavior. Light may increase octopamine production, thereby stimulating cilial activity, extending swimming behavior, and preventing larvae from attaching to a substrate. This research sheds light on previously unknown sensory mechanisms in B. neritina larvae, and may aid in the development of new biofouling control strategies.

Barnacles are dominant hard–fouling organisms in marine waters. They attach to substrates by secreting a complex proteinaceous adhesive. Understanding the chemical composition of this multi–protein underwater adhesive and how it is affected by environmental variables, such as oceanic temperatures, is critical for developing nontoxic solutions to control biofouling. Previous experiments in our lab revealed an inverse relationship between critical removal stress (CRS) and temperatures at which barnacles were reared. Further investigations showed that this correlation is not attributed to differences in physical properties such as barnacle size or short–term changes in the viscosity of adhesive. Therefore, the observed effects may be influenced by a physiological response to temperature during initial growth and development. We hypothesized that rearing temperature affects the expression of proteins found in the adhesive matrix. To elucidate the underlying mechanisms responsible for the temperature effect, we analyzed uncured barnacle adhesive using two-dimensional gel electrophoresis (2DGE) and matrix-assisted laser desorption/ionization-tandem time-of-flight (MALDI-TOF/TOF) mass spectrometry (MS). In our analysis, we 1) detected differences in protein expression at two experimental temperatures (15°C and 25°C) and 2) identified several proteins that may serve functional roles in the process of adhesion. Our data are also consistent with a model that the curing process of barnacle adhesive may be analogous to the process of wound healing in animals.

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