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Reverse Osmosis (RO) filtration is capable of producing high quality drinking water with an ultra-low nutrient level. Therefore, a very low bacterial growth potential (BGP). BGP is a key bioassay to evaluate microbial quality and the biological stability of drinking water. Current methods to assess BGP in drinking water need to be adapted to the wide variety of water types due to results could highly vary from each, providing unreliable insights to the biological stability of the assessed water. This study evaluates the application of an FCM-based BGP assay for RO produced chlorinated drinking water. The approach combines (i) the standardization of a quenching agent concentration, (ii) the impact of sample pre-treatment such as filtration and pasteurization on the BGP of RO produced chlorinated water, (iii) the effect of different inoculums (an indigenous community and a mixture with bottled water) on the bacterial growth and their longevity after being stored, (iv) the use of BGP to assess the performance of carbon filters in removing chlorine and (v) the use of BGP to assess the effect of the addition of magnesium on bacterial growth. The results showed that high concentrations of sodium metabisulphite (> 7.5 mg/L) decrease the pH levels of the water,thus, inhibiting bacterial growth. Filtration had a significant effect on BGP values (2.62 x10^5 intact cells/mL) in comparison to pasteurization (9.02 x 10^4 intact cells/mL), when compared to the control. Using a mixture of water types as inoculum might provide a better insight to bacterial growth potential in water due to a higher consumption of nutrients. BGP demonstrated to be a sensitive tool to test the performance of carbonfilters applied to remove chlorine and its applicability to evaluate the biological stability of RO produced chlorinated drinking water. The concentrations of magnesium chloride tested in this study did not have a significant effect on cell numbers.

Yes / Reverse osmosis (RO) has become a common method for treating wastewater and removing several harmful organic compounds because of its relative ease of use and reduced costs. Chlorophenol is a toxic compound for humans and can readily be found in the wastewater of a wide range of industries. Previous research in this area of work has already provided promising results in respect of the performance of an individual spiral wound RO process for removing chlorophenol from wastewater, but the associated removal rates have stayed stubbornly low. The literature has so far confirmed that the efficiency of eliminating chlorophenol from wastewater using a pilot-scale of an individual spiral wound RO process is around 83 %, compared to 97 % for dimethylphenol. This paper explores the potential of an alternative configuration of two-stage/two-pass RO process for improving such low chlorophenol rejection rates via simulation and optimisation. The operational optimisation carried out is enhanced by constraining the total recovery rate to a realistic value by varying the system operating parameters according to the allowable limits of the process. The results indicate that the proposed configuration has the potential to increase the rejection of chlorophenol by 12.4 % while achieving 40 % total water recovery at an energy consumption of 1.949 kWh/m³.

Yes / N-nitrosamine in wastewater treatment processes can contribute to several public health impacts including human carcinogens even at very low concentration. In this work, spiral-wound reverse osmosis (SWRO) process is used to remove N-nitrosamine compounds from wastewater. Effects of operating parameters of the SWRO process on the removal of N-nitrosamine, total water recovery, and specific energy consumption for a SWRO configurations are evaluated via simulation and optimisation. For this purpose, the one-dimensional distributed model developed earlier by the authors is modified by including different mass transfer coefficient correlation, temperature dependent water and solute permeability correlations and energy equations. The model is first validated by estimating a new set of model parameters using eight set of experimental data from the literature and is then used to simulate the process with and without energy recovery device to facilitate deeper insight of the effect of operating conditions on the process performance. The model is then embedded within an optimisation framework and optimisation problems to maximise N-nitrosamine rejections and to minimise specific energy consumption are formulated and solved while the operating conditions are optimized simultaneously.

Yes / Phenol and phenolic derivatives found in different industrial effluents are highly toxic and extremely harmful to human and the aquatic ecosystem. In the past, trickle bed reactor (TBR), reverse osmosis (RO) and other processes have been used to remove phenol from wastewater. However, each of these technologies has limitations in terms of the phenol concentration in the feed water and the efficiency of phenol rejection rate. In this work, an integrated hybrid TBR-RO process for removing high concentration phenol from wastewater is suggested and model-based simulation of the process is presented to evaluate the performance of the process. The models for both TBR and RO processes were independently validated against experimental data from the literature before coupling together to make the hybrid process. The results clearly show that the combined process significantly improves the rejection rate of phenol compared to that obtained via the individual processes.

Yes / Reverse Osmosis (RO) processes are readily used for removing pollutants, such as dimethylphenol from wastewater. A number of operating parameters must be controlled within the process constraints to achieve an efficient removal of such pollutants. Understanding the process dynamics is absolutely essential and is a pre-step for designing any effective controllers for any process. In this work, a detailed distributed two-dimensional dynamic (x and y dimensions and time) model for a spiral-wound RO process is developed extending the 2-D steady state model of the authors published earlier. The model is used to capture the dynamics of the RO process for the removal of dimethylphenol from wastewater. The performance of the 2-D model is compared with that obtained using 1-D dynamic model before the model is being used to investigate the performance of the RO process for a range of operating conditions.

Understanding transport of water molecules and salt ions from a molecular level up to macroscopic length scales is critical to the design of novel materials for many applications, including separations membranes for fuel cell and desalination applications, as well as rechargeable battery technology. This work aims to investigate and develop new models correlating the dynamics and structure of polymeric materials, to the transport of small molecules within them, using a variety of Nuclear Magnetic Resonance (NMR) techniques. We present three studies through which we utilize two chemically similar membranes: hydroxyethyl acrylate-co-ethyl acrylate (HEA-co-EA) and hydroxymethyl methacrylate-co-methyl methacrylate (HEMA-co-MMA), which greatly differ in glass transition temperature, in order to understand the fundamental relationships from polymer chain dynamics and small molecule diffusion. From observations of the micron scale diffusion of these materials we find that the more dynamic, rubbery HEA-co-EA exhibits lower water to salt selectivity than HEMA-co-MMA, and that this difference arises from nanoscale morphology of the materials. From this, we propose a new model for hydrophilic pathways inside polymeric materials consisting of nanometer scale interconnected pathways are interrupted by micron scale arrangements of so-called "dead ends". We also for the first time show the separation of material tortuosity into two regimes, ranging from the nanometer-bulk and micron-bulk length scales. We further separate the contributions of structure from chemical interactions in the chemically similar desalination materials by investigating the local activation energy of diffusion in both materials, as well as aqueous solutions of the hydrophilic monomers analogous to the internal membrane environment. We find that the effects of local geometric confinement are very similar between the two materials, however the intermolecular interactions between water and the hydrophilic monomers, with respect to water transport, are significantly different between the two hydrophilic species. Geometric confinement accounts for a 5 ± 1 kJ/mol increase in diffusive activation energy from solution to membrane for both chemistries, and a 4 ± 1 kJ/mol difference in activation energy is seen between the two chemistries in both solution and membrane form. We propose that the entropic contributions to transport, are strongly impacted by the rigid environment of the HEMA material, and is related to the increased water-salt selectivity, as well as the increasing selectivity with increased ionic size observed compared to the HEA system. Using Dynamic NMR spectroscopy, we further investigate the differences seen in water-monomer intermolecular proton exchange by NMR. We utilize an iterative least-squares solving method to fit our exchange lineshape to a model of an uncoupled, two-site exchange lineshape in order to obtain rate and equilibrium population data from -50 to 70 °C. We find that, similar to the diffusive activation energy, the HEA-water system shows reduced enthalpy and entropy of the transition state compared to HEMA-water, such that there is faster exchange between HEMA and water at all temperatures measured, in addition to more biased populations in the HEA-water system. / Doctor of Philosophy / Understanding transport of water molecules and salt ions from a molecular level up to macroscopic length scales is critical to the design of novel materials for many applications, including separations membranes for fuel cell and desalination applications, as well as rechargeable battery technology. This work aims to investigate and develop new models correlating the dynamics and structure of polymeric materials, to the transport of small molecules within them, using a variety of Nuclear Magnetic Resonance (NMR) techniques. We will present three studies in which we seek to further understand the relationships between a material's physical and chemical properties, with the behavior of small molecules like water absorbed within the material. NMR spectroscopy, while not the standard method for characterizing desalination membranes, allows us to specifically probe direct effects on molecular motion of polymer structure from the microscopic level to the bulk, a feat not easily achieved by any other single technique. The first study presented within focuses on the differences in micrometer scale structure in two near identical sets of materials; differing only in that one is rubbery with flexible polymer chains, and the other is rigid with relatively immobile polymer chains. The second study takes these two materials and investigates them through a different lens, probing the molecular scale differences in water motions imparted by the flexible versus rigid polymer chains. The third and final study looks into the fundamental differences seen in how the two chemistries used to create the polymers in the first two studies interact with water molecules through a different NMR technique. These three studies together represent a series of methods and techniques that can be applied to many other classes of polymer materials, such as those destined for use in fuel cells and rechargeable batteries, in order to better understand the fundamental forces at work in those systems to aid in the design of the next generation's materials.

Over 30% of the world's population does not have access to safe drinking water, and the need for clean water spans further than just for human consumption. Currently, we use freshwater for growing agriculture, raising livestock, generating power, sanitizing waste, mining resources, and fabricating consumer goods. With that being said, the world is beginning to feel pressure from the excessive freshwater withdrawal compared to the current freshwater supply. This water stress is causing a water crisis. Places including Australia, South Africa, and California in the United States, just to name a few, are beginning to run out of fresh water to support daily societal demands. This is a phenomenon that is indiscriminately observed in all ranges of economically and politically developed countries and environments. However, it is important to note that less politically and economically developed countries especially those in arid climates, experience higher water stress than countries without such qualities. With only 2.5% of the world's water being freshwater and 30% of it being accessible as either ground or surface water, freshwater is a scarce resource, especially with the growing population and society's demand for water. Since the remaining 97.5% of water is composed of either brackish or seawater (saline water sources), one way to overcome the water stress would be to convert saline water into freshwater. As a result, various desalination techniques have been developed in the last 80 years that employ either membrane technology or temperature alterations to desalinate either brackish or seawater. One of the fastest growing methods for producing freshwater is reverse osmosis. Reverse osmosis uses an externally applied pressure, in the form of a cross flow back pressure, to overcome the osmotic pressure produced by the saline gradient across a semi-permeable membrane. The semi permeable membrane commercially consists of an interfacially polymerized aromatic polyamide thin film composite with a polysulfone porous backing that allows water to pass through while barring the transport of salt ions. This research focuses on the development of sulfonated poly(arylene ether sulfone) derivatives with differing amounts of sulfonation and with the ions placed at different structural positions. Previously, such materials were tested as potential high performance fuel cell membranes, but they are also of interest as potential high performance water desalination membranes, specifically for reverse osmosis. Two different methods were used to synthesize the sulfonated polysulfone derivatives: direct polymerization and post-modification of a non-sulfonated active polysulfone. The polysulfones from direct polymerization incorporated specialty sulfonated monomers, which were stoichiometrically controlled during the polymerization. Sulfonated polysulfones that were synthesized from post sulfonation incorporated biphenol and hydroquinone monomer units randomly throughout the polysufone backbones. These units could be sulfonated selectively because of their activation towards electrophilic aromatic substitution with sulfuric acid. Each of the polymers were cast into films ranging between 20-100 microns in thickness and tested for water uptake, hydrated uniaxial tensile properties, crossflow water and salt transport properties, and for crosslinked samples, gel fractions. The water uptakes from all the polysulfones were tuned by the degree of sulfonation or disulfonation present in the polymer. This was either controlled via the presence of a sulfonated monomer or a monomer that was active toward electrophilic aromatic substitution after polycondensation of the polysulfone. All polymers exhibited increases in their water uptake as the degree of sulfonation increased. We also observed a decreasing trend in the hydrated mechanical properties of the films for all the high molecular weight linear polymers as the water uptake was increased. The directly polymerized sulfonated polysulfones were found to have high hydrated elastic moduli ranging between 400 and 1000 MPa, while the post sulfonated counterparts (with either hydroquinone or biphenol incorporated in their structures) exhibited elastic moduli ranging between 1000 and 1500 MPa. It is important to note that the structures of the polymers were slightly different from one another because of the technique used to synthesize them. Thus, the increases in hydrated moduli among polymers synthesized via different routes may have influences from differences in chemical structures. Some of the polymers with higher degrees of sulfonation were synthesized as amine terminated oligomers with varying controlled molecular weights. The two targeted molecular weights were 5 and 10 kDa. Those oligomers were then crosslinked with a tetra-functional epoxide agent. The increases in sulfonation allowed for increases in water uptake and in theory, the water throughput through the sulfonated polysulfone membrane. Decreases in hydrated mechanical performance of the crosslinked networks with increasing degrees of sulfonation were also observed, similar to their high molecular weight linear counterparts. The directly polymerized crosslinked networks had salt permeabilities that plateaued at 70% disulfonation for both the 5 and 10 kDa polymers. Thus, we expect disulfonation content greater than 70% would lead to higher water throughput without significant increases in salt transport. / Doctor of Philosophy / A worldwide shortage of freshwater is becoming more problematic by each passing day. The World Health Organization and the United Nation's World Water Assessment Program predict that by 2025, 50-66% of the world's population will be living in a water-stressed area. This includes any area that experiences higher clean water withdrawals than are available. This includes but is not limited to areas that are politically unstable, technologically disadvantaged, resource deficient, located in arid climates, and highly populated. To put this further into perspective, only 2.5% of the available water on earth is freshwater. Freshwater typically has low concentrations of dissolved salts that are safe for human consumption and use. Of the available freshwater, only 30% of it is actually accessible for use through either surface or groundwater reservoirs, making the amount of clean water available for usage already a scarce resource. On the other hand, 97.5% of the world's water is composed of saline water reservoirs in the form of brackish and seawater. Through harnessing, seawater and removing the excess dissolved salt ions, the salt water can be converted to freshwater. Two major methods have been developed to remove the dissolved ions from water through either membrane filtration or thermal phase changes. One of the fastest growing membrane filtration techniques used worldwide is reverse osmosis. Reverse osmosis refers to the use of applied pressure across a semipermeable membrane to desalinate saline water. The semipermeable membrane prevents the migration of salt ions through the membrane while allowing transport of water. This work has focused on developing new polymers that can increase the overall efficiency of water desalination. Different types of high performance sulfonated polysulfone derivative polymers were synthesized and used to make membranes that were subsequently tested for performance. Relationships between the polymer structure, process, and properties were quantified through different analytical techniques. This study showed how the properties of sulfonated polysulfone membranes may be manipulated depending on structural modifications and processing to increase both the material's water throughput and salt rejection.