In recent decades, there has been increasing concern about water contaminated by chemicals of emerging concern (CECs), a.k.a., trace organic micropollutants or emerging contaminants. Recent advances in analytical procedures enable detection of compounds like pharmaceuticals & personal care products (PhPCPs), hormones, endocrine disrupting compounds (EDCs), disinfection by-products (DBPs) and synthetic organic chemicals (SOCs). Many members of these compound classes are carcinogen or mutagens. A number of conventional and advanced methods have been evaluated (individually and in combination) for removal of CECs from water sources, including enhanced coagulation, activated carbon, activated sludge, membrane bioreactors, riverbank filtration, nanofiltration (NF), reverse osmosis (RO), and advanced oxidation processes. NF and RO membranes can achieve very high removals of many CECs; however, removal of a specific solute by a given membrane can vary widely at different water treatment plants. It has been proposed that different membrane performances were due to variations in water chemistry (i.e., pH, TDS, hardness, etc.), but it was not specified as to why the water chemistry so profoundly influences observed CEC removal. This study attempts to relate how water chemistry affects NF and RO membrane performance by elucidating structural changes in the membrane barrier layer solely due to background water chemistry - using model membranes, and well controlled laboratory studies using different solutes and electrolytes. A recently proposed NF/RO structure-performance model used to fit experimental data suggests that NF/RO membranes become looser (i.e, lower rejection of trace organics and high water permeability) with increasing water ionic strength, pH and divalent content.

The objective and focus of this study is to fully understand trace organic pollutant transport through NF/RO membranes. An extension of the classical solution-diffusion model had been developed that relates transport through NF/RO membranes directly to membrane structure descriptors (i.e., effective barrier layer pore size, porosity and thickness, etc.). In general, model predictions agreed well with experimental data suggesting the model captures the phenomenological behavior of commercial NF/RO membranes for separations relevant to modern water treatment objectives. The model also provides new mechanistic insights about the "effective structure" of NF/RO composite membranes and how trace organic solutes are rejected. These results suggest it is possible and important to fine-tune the surface energy of membrane and membrane structure (pore size, porosity, thickness) to achieve high membrane selectivity for certain solute.

The effects of feed solution ionic strength, pH and divalent cation content on NF/RO membrane structure and performance were elucidated experimentally and fitted with the newly developed model. Generally, water permeabilities of all three membranes decreased with ionic strength and divalent cation content, but increased with pH. For RO membranes, neutral solute rejection decreased with pH and divalent cation content, but increased with ionic strength and the salt rejection remained independent with water chemistry except for very low pH of 3; for a NF membrane, solute rejection was more sensitive to water chemistry and neutral solute rejection decreased with ionic strength, pH, but increased with divalent cation content. Ultimately, these new insights may be useful in selection of already commercial or design of new NF/RO membranes for removal of chemicals of emerging concern in water treatment.

Four different organic solute removals by six different commercial NF/RO membranes in laboratory re-created groundwater matrix were experimentally determined. SWRO membranes exhibited excellent removal efficiency (> 90%) for both NDMA and 1,4-dioxane in groundwater, while NF membranes showed inefficient separation. Correlation studies suggested that both size exclusion and thermodynamic partitioning play important roles in trace organics removal and a partition coefficient, which combines both steric effects and solute-membrane interactions, can be employed to predict organic solute rejection by NF/RO membranes.

Since the majority of biofouling occurs on the surface of the polymeric membranes, key interfacial interactions between a membrane surface and a biofoulant play a pivotal role in biofouling phenomena. In thermodynamic perspective, biofouling can be interpreted as adhesion of two different entities, a biofoulant and a membrane, through a media, (herein, water), to be a combined column. Therefore, adhesion accompanies a structural change of interfaces existing in the aqueous system. This interface-transitive nature of biofouling phenomena leads that surface tension-based theories are adopted in the fundamental understanding of the membrane biofouling. Among those theories, the van Oss approach has been considered prominent because of its satisfactory prediction for experimental results of biofouling tests. According to van Oss approach, in aqueous media, Lewis acid-base interaction occurs between the electron-acceptor in hydrogen atoms of water and lone pairs of atoms of a solid, basically having an analogous concept with hydrogen-bonding. The membrane surface with polar properties is able to hold water molecules and form a hydration cell layer on its surface, which may impede the access of biofoulant to the membrane surface. Because the biofoulant also has the electron-donating and accepting potentials, other interfacial interactions also occur in biofoulant-water and biofoulant–membrane surface. Therefore, better thermodynamic understanding on the biofouling phenomena need a perspective that ponders the three different but deeply interconnected interfacial interactions existing in membrane-water, water-biofoulant and biofoulant-membrane. The purpose of this dissertation is to investigate the biofouling phenomena in the molecular basis that can qualitatively and quantitatively evaluate the roles of physicochemical properties of water, membranes and biofoulants in biofoulant-membrane interaction for aqueous system.

First, this study investigated the water-membrane interaction in terms of surface tension properties of a membrane and their discrete interactions with water in Chapter 2. This chapter simulated the available surface tension parameters of polymeric porous membranes using different presumptions on polar properties of water and evaluates the effect of each surface tension parameter of a membrane on water-membrane interactions. The simulated libraries of surface tension parameters revealed that polymeric porous membranes highly tend to fall into a category of electron-donor monopolar or semi-monopolar solids. The high electron-accepticity of water emphasized the role of electron-doicity of a membrane in the interfacial interaction between a membrane and water and caused the polar adhesion between electron-donor sites of a membrane and electron-acceptor sites of water to be a major interaction component than other components. The high Lewis acidity of water highlighted the role of electron-donicity of a membrane in its wettability as well. A higher electron-donicity of a membrane has little impact on the total surface tension of the membrane surface, but successfully favors the electron-acceptor sites of water forming a significantly lower surface tension of the water-membrane interface and thus a greater affinity between the membrane and water.

Chapter 3 investigated the effects of water-solids interactions on biofouling phenomena and explored fining key physicochemical properties of a membrane for biofouling resistance. The high electron-accepticity of water emphasized the importance of electron-donicity of a membrane and a biofoulant in their interfacial interaction through water and drove acid-base interaction to be a major interaction component in the interfacial interactions between membranes and a biofoulant. The surfaces of various biofoulants were characterized with highly variable electron-donicities and the biofoulant with lower electron donicity can be more vulnerable to biofouling due to the inferior hydration energy formed on the surface of the biofoulant. The inferior hydration energy by a low electron-donicity of a biofoulant can be compensated by an enhanced electron-donicity of a membrane; this fact leads to propose a standard of an electron-donicity demand for a membrane to have a positive energy barrier against a given biofoulant. Experimental results of a microbial adhesion test and biofouling tests qualitatively correlated well with tendencies of electron-donicities of the test membranes, proving an electron-donicity of a membrane to be a reasonable indicator for the anti-biofouling property of the membrane.

Chapter 4 attempted to impart membranes with hydrophilic and anti-biofouling properties by grafting hydrophilic polymers to the surface. Photoactive perfluorophenyl azides (PFPAs) were utilized to generate highly reactive nitrenes (when exposed to UV light) that can covalently bind to the membranes’ surfaces. Three different types of small molecule PFPA derivatives were applied and the experimental data directed us to modify the UF membrane surfaces with water-soluble small molecules to maintain the membranes’ high permeability. The effects of small molecule PFPA derivatives on surface tension characteristics of a polymeric membrane were analyzed by van Oss method. Modeling data indicated that the electron-donicity of membranes plays an essential role in foulant adhesion forces. The analyzed physicochemical properties of the modified membranes were compared to the experimental results of a biofouling test with alginate solution. The modified membranes with higher electron-donicity exhibit outstanding foul-resistance against sodium alginate, a model foulant, during operation.

Water scarcity, water-stress, and drought are becoming common terms to describe the world we live in. In order to augment the world's depleting fresh water supply, methods to treat non-traditional water sources to become potable water are being explored. Reverse osmosis is a very promising technology to desalinate seawater, brackish water and even waste water into fresh product water. Forward osmosis (FO) is a developing technology that is currently used to concentrate fruit juices and provide nutrient juices using impaired water sources. Furthermore, FO is also explored as a potential for low energy desalination. However, much research needs to be done to understand how to improve membrane performance, especially for FO applications.

The goal of this research was understand whether membranes with high hydrophilicity and large macrovoids will lower internal concentration polarization in FO membranes and increase water permeability and selectivity. Polyaniline (PANi) was used a model material due to its hydrophilicity and tunable pore structure to develop this understanding between membrane structure and performance. First, a review of current membrane materials for RO and FO was provided, along with an overview of membrane formation techniques, and previous research on polyaniline used in membrane filtration. A computational fluid dynamics model study revealed that the base thickness of the membrane dictates the upper bound of a composite membrane. With the same polymer volume, distributing the polymer as an undulating film will always have higher permeability due to the creation of shorter diffusive path lengths. This research showed that the interplay between support membrane and thin film are vast. Then, phase-inverted PANi membranes along with membranes blended with polysulfone were coated with polyamide thin film by interfacial polymerization. Due to the hydrophilicity of PANi, it was found that more water was taken up than the amine during the immersion step, requiring changes in the amine concentration to increase diffusivity into the reaction zone. Through this study, it was found that the membrane structural parameter was not representative of the porous substructure, but rather of the mass transfer limitations of the membrane. As a result, FO membranes were made by phase inversion of pure PANi without thin film coating, and post-treated by wet-curing, acid and base to alter its performance and skin-layer morphology. By post-treating a membrane with camphor-sulfonic acid, enhanced performance was achieved due to denser skin layer and increased pore volume. This study provided an overview of the relationship between composite membrane structure and performance in finding that: 1) support membrane changes flux distribution, 2) thin film polymer distribution can change performance, 3) support membrane dictates thin film formation, and 4) phase inverted membrane skin layer dictates performance.

Salinity gradient power (SGP), the controlled mixing of streams with different salinity, is a potential route for clean and renewable base-load power generation. The two most popular forms of SGP production, pressure retarded osmosis (PRO) and reverse electrodialysis (RED), have received renewed research interest in recent years. While previous modeling work has focused on the application of simple mathematical models to these processes, in order to accurately predict process performance on scale-up, robust models must be developed. The objective and focus of this dissertation is to understand through mathematical modeling the practical performance that can be achieved in PRO and RED as the technology transitions from the laboratory scale to full-scale implementation.

First, the thermodynamics of mixing are discussed for both PRO and RED, with the intrinsic differences highlighted for each process. Using simple thermodynamic models, the integration of PRO and RED with reverse osmosis (RO) is discussed as a method for reducing the specific energy consumption (SEC) of seawater desalination. This "osmotic energy recovery" (OER) is evaluated in a seawaterRO plant that includes state-of-the-art RO membranes, plantdesigns, operating conditions, and hydraulic energy recovery (HER) technology. Weassume the use of treated wastewater effluent as the OERdilute feed, which may not be available in suitable quality or quantity to allow operation of the coupled process. A two-stage OER configuration could reduce the SEC of seawater RO plants to well below the theoretical minimum work of separation for state-of- the-art RO-HER configurations with a breakeven OER capital expenditure (CAPEX) equivalent to 42% of typical RO-HER plant cost suggesting significant cost savings may also be realized. At present, there is no commercially viable OER technology; hence, the feasibility of using OER at seawater RO plants remains speculative, however attractive.

In order to probe scale up characteristics of SGP, a process model has been developed for PRO accounting for full-scale system losses such as viscous dissipation, external mass transfer and equipment efficiency. Also, an existing model for RED is adapted to account for analogous full-scale systems losses. We project practical power densities and process efficiencies. The projected power density for PRO (using best available membranes) is much lower than generally predicted by extrapolation of experimental data. For example, a power density of 5 W/m2 extrapolated from laboratory experiments actually yielded negative power at full-scale. Hydraulic energy recovery device (HER) efficiency doubles the maximum power density for HER efficiency increase from 90% to 99%. Furthermore, the operating pressure, load voltage, and crossflow velocities typically applied in laboratory studies appear much too high to be practical in full-scale PRO and RED systems. RED systems should be designed with relatively short lengths compared to PRO. For both processes, energy efficiency does not occur at thermodynamic equilibrium due to hydraulic losses. Finally, maximum power density appears an inadequate parameter for assessing full-scale PRO/RED process feasibility because both processes could produce the same maximum power density, but different power outputs and efficiencies with different system sizes.

While there has been a significant amount of laboratory work focused on improving membrane performance in PRO, there has been little emphasis on developing novel PRO process configurations that might dramatically improve overall process performance. Here, we introduce a novel PRO configuration and apply the developed process model in order to evaluate the performance of the process. This "staged" configuration has the potential to dramatically improve the performance of PRO with up to 33% higher water flux over the standard PRO configuration. In this new arrangement, intermodule hydroturbines are placed strategically in order to modulate the applied pressure over the length of the system. The additional hydroturbines match the applied pressure to the optimum flux condition over each segment and substantially increase the total water recovery. The impact on energy efficiency is significant for some mixing regimes, with seawater-river water and brine-river water mixing corresponding to efficiency increases from 31% to 44% and 34% to 50%, respectively, versus the standard PRO configuration. Of course, performance improvements must be considered in light of the increased capital costs arising from the additional hydroturbines.

Finally, the PRO process model is integrated with cost data in order to determine the change in energy production cost with system size. Since existing cost correlations from the literature are often outdated, new correlations have been developed for each plant component by contacting suppliers and manufacturers. Linking these correlations with power output data, energy cost has been evaluated under different operating conditions and with membrane properties. The results suggest that there is still significant room for improvement in membrane design in order to further reduce the cost of PRO. Furthermore, from an economic perspective, brine-river water mixing appears to be a much more promising mixing regime than seawater-river mixing.

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.

Nanotechnology is being used to enhance conventional ceramic and polymeric water treatment membrane materials through various avenues. Among the numerous concepts proposed, the most promising to date include zeolitic and catalytic nanoparticle coated ceramic membranes, hybrid inorganic-organic nanocomposite membranes, and bio-inspired membranes such as hybrid protein-polymer biomimetic membranes, aligned nanotube membranes, and isoporous block copolymer membranes. Zeolitic and catalytic membranes appear reasonably far from commercial reality and offer small to moderate performance enhancements. Overall, bio-inspired membranes are farthest from commercial reality, but offer the most promise for performance enhancements; however, nanocomposite membranes offering significant performance enhancements are already commercially available.

Isoporous block copolymer membranes represent a fully-polymeric analog to the ordered structure associated with bio-inspired materials and are able to be produced through conventional fabrication methods. These membranes represent a possible route towards more precise particle and macromolecular separations, which are of interest across many industries. Herein, membranes with vertically-aligned nanopores are formed from a poly(isoprene-b-styrene-b-4 vinyl pyridine) triblock terpolymer via a hybrid self-assembly/nonsolvent induced phase separation process. Polymer concentration, solvent composition, and evaporation time in the fabrication process were varied to tailor ordering of the selective layer and produce enhanced water permeability. Water permeability was doubled through the optimization process, while maintaining the surface morphology and, thus, the resulting selectivity of the membrane. This was achieved by increasing volatile solvent concentration, thereby decreasing the evaporation period required for self-assembly. Fine-tuning was required, however, since overly-rapid evaporation did not yield the desired pore structure. Transport models, used to relate the in-situ structure to the performance of these materials, revealed narrowing of pores and blocking by the dense region below. It was shown that these vertically aligned nanoporous membranes compare favorably with commercial ultrafiltration membranes formed by conventional phase inversion and track-etching processes, which suggests there is practical value in further developing and optimizing these materials for specific industrial separations.

Thermo-chemical bioresource recovery technologies present an opportunity to reduce environmental impacts and improve economic performance of municipal biosolids management operations. In this study, a uniform grading framework was established and findings from techno-economic and lifecycle assessments of wastewater biosolids management processes were synthesized into harmonized system boundaries to evaluate their environmental and commercial viability. It was found that while conventional wastewater biosolids management practices such as anaerobic digestion, landfilling, land application, and incineration are commercially mature, they pose significant environmental concerns and large economic burdens on municipalities. Furthermore, state-of-the-art thermochemical bioresource recovery technologies such as hydrothermal liquefaction, gasification, and pyrolysis showed potential to provide economic and environmental benefit through the recovery of carbon and nutrients in wastewater biosolids as biofuels, fertilizers, and other niche products that lessen demand for fossil-based resources and provide additional sources of revenue for wastewater utilities. Hydrothermal liquefaction paired with existing wastewater infrastructure was found to provide the greatest economic and environmental benefit.

Across the globe millions of people lack access to clean drinking water. This has led to widespread distrust of water resources, including tap water. One way to ensure the quality of drinking water and re-establish public trust is by implementing smart water monitoring technologies that can be utilized by operators and consumers. The work presented in this paper encompasses the design and testing of a wireless sensor network for point of use water quality monitoring. The final prototype allows for remote data monitoring and lays the foundations for further work to use the data acquired by the system for uses such as contamination detection and predictive modeling of water quality.