Wastewater reclamation and reuse have been increasingly practiced as sustainable strategies to meet water demands, particularly in regions threatened by water shortages. However, one of the biggest challenges for reusing wastewater effluents (WEs) as irrigation water is to remove emerging organic contaminants such as persistent and potentially bioaccumulated per- and polyfluoroalkyl substances (PFAS), whose presence may result in adverse impacts on crops, soils, aqueous ecosystems, and human health. Photocatalysis is an effective and promising technique to remediate PFAS in aqueous media. This dissertation aims to: i) Develop a novel, environmental-friendly, and low-cost treatment process for PFAS removal and degradation for water reuse; ii) Optimize the experimental conditions and investigate the removal mechanisms of PFAS with different structures in this novel process; iii) Scale up this treatment process and apply it to treatment of WEs in a point-of-use (POU) system. First, ultraviolet (UV) C /nanoscale zero-valent iron (nZVI, Fe0 nanoparticles (NPs)) system is used for the first time to induce PFAS photocatalytic removal from aqueous solution. Oxidative and/or reductive degradation of three representative PFAS - perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorooctane sulfonate (PFOS) was achieved using Fe0 NPs under UVC light both with and without presence of oxygen. However, no PFAS removal was observed either under visible light and in the dark, and much lower PFAS degradation was achieved under UVA light. Higher degradation and defluorination efficiencies were obtained for longer chain PFNA compared to PFOA, and higher degradation and defluorination of PFAS were achieved without presence of O2 compared to with O2. The degradation of PFOA and PFOS followed first order reaction kinetics with the highest efficiencies achieved of 97.6, >99.9, and 98.5% without presence of O2 for PFOA, PFNA, and PFOS, respectively. The degradation efficiencies increased with the increase of nZVI concentrations in the range of 1-100 mg/L. The degradation efficiency of PFOA using bare Fe0 NPs was higher than that using 1% PVP-coated Fe0 NPs in the initial 6 h. Second, the removal mechanism of PFAS in UVC/Fe0 NPs system was obtained by testing the concentrations of iron ions (Fe2+/Fe3+), intermediate products, and reactive oxygen species (ROS, e.g., ·O2- and ·OH) generated, and conducting ROS quenching experiments. The proposed degradation pathway of PFCAs (PFNA and PFOA) was initiated from PFOA/PFNA oxidation by transferring an electron of the carboxylate terminal group of PFOA/PFNA to the Fe(III)-carboxylate complex, then followed by decarboxylation−hydroxylation−elimination−hydrolysis (DHEH) pathway and the accompanying CO2 and F− release. The generated shorter chain PFCAs also underwent degradation with time in the system. This proposed degradation pathway was confirmed by the formation of shorter chain PFCAs, e.g. PFHpA, PFHxA, PFPeA, and PFBA, F- ions, and rapid consumption of Fe3+. For PFOS, besides H/F exchange pathway and chain-shortening (DHEH pathway) to form short chain PFAS during PFCA degradation, desulfonation to form PFOA followed by PFOA degradation also happened. These pathways were suggested by the formation of intermediates — trace amount of shorter chain PFCAs, 6:2 FTS, PFHpS, and F- ions. ·O2- and ·OH were not involved in PFOA degradation in the UVC/Fe0 NPs system with presence of O2, while they may be involved in PFOS degradation, e.g., desulfonation to form PFOA, which were suggested by the results of quenching experiments. And introducing H2O2 into the UVC/Fe0 NPs system resulted in lower PFOA degradation efficiency and defluorination efficiency, which also indicated that ·OH may not be involved in PFOA degradation. Hydrated electrons e-aq that can be involved in desulfonation, defluorination, and C-C bond scission processes were likely quenched by the presence of oxygen to reduce the degradation and defluorination efficiencies; plus, presence of Fe0 NPs may promote the generation of hydrated electrons. Last, UVC/Fe0 NPs system was used to degrade PFAS from WEs in both bench scale and in a scale up POU system. The degradation efficiencies of PFAS in WEs from both wastewater treatment plants (WWTP) were lower than that in deionized water, likely reflecting the complex compositions in the environmental media. Optimal degradation efficiencies of 90±1%, 88±1%, and 46±2% were obtained for PFNA, PFOS, and PFOA, respectively, each starting from 0.5 µg/L using bare Fe0 at pH 3.0 after 2 h. PFAS removal and bacterial inactivation were achieved simultaneously in the POU system using Fe0 NPs without and with rGO support under UVC irradiation in WEs, although the PFAS levels were still above the regulation levels for discard. These pilot tests provided more data and experiences for the real applications of UVC/Fe0 NP system to PFAS contaminated wastewater or other water matrix treatment. Overall, this research demonstrated a cost-effective and environment-friendly method — UVC/Fe0 NPs method for PFAS (i.e., PFOA, PFNA, and PFOS) degradation from WEs for water reuse both with and without presence of oxygen. The possible degradation mechanisms of PFAS with different structures were obtained by testing the concentrations of iron ions, intermediate products, and reactive oxygen species (ROS) involved in the reactions. The developed technology can be potentially applied to treat other environmental media (e.g., groundwater, landfill leachate) that are contaminated by PFAS from previous anthropogenic activities.

El presente trabajo analiza una propuesta de reutilización de agua proveniente del concreto fresco retornado a las plantas de premezclado. Esta propuesta es dada mediante productos floculantes, los cuales ayudarán a la clarificación del agua concentrada en las pozas de las industrias de premezclado. Asimismo, el agua recuperada tendrá similares características que el agua convencional utilizada, y que posteriormente ingresará al nuevo diseño de concreto, en donde aportará en un 5% en la resistencia del concreto adicional. Por otro lado, se analizó la posibilidad de reutilizar los finos acumulados en el fondo de las pozas, pero estos no aportan resistencia al concreto ya que presenta el cemento ya hidratado; sin embargo, se puede utilizar para otros propósitos. Se realizó un análisis cualitativo y cuantitativo de la incidencia económica, ambiental y legal; en el estudio de aguas de lavado se han analizado parámetros básicos (densidad por pesada diferencial, pH mediante pHmetría, composición química) de tres muestras procedentes de distintas plantas de premezclado para evaluar la calidad de los vertidos. Se proponen soluciones aplicables y mejoras tecnológicas en el proceso de lavado de mixers con el fin de disminuir el volumen de los sólidos arrastrados, sin que ello perturbe el medio ambiente, y posibilitando un ahorro del agua. Por último, con el floculante elegido y los resultados obtenidos se analizará la optimización económica que produce este método para la limpieza de mixers de concreto premezclado. / The present work analyzes a proposal for the reuse of water from fresh concrete returned to the ready-mix plants. This proposal is given through flocculating products, which will help clarify the concentrated water in the pools of the premixing industries. Likewise, the recovered water will have similar characteristics to the conventional water used, and which will subsequently enter the new concrete design, where it will contribute 5% in the strength of the additional concrete. On the other hand, the possibility of reusing the fines accumulated at the bottom of the ponds was analyzed, but these do not provide resistance to the concrete since the cement already hydrated; however, it can be used for other purposes. A qualitative and quantitative analysis of the economic, environmental and legal incidence was carried out; In the study of washing water, basic parameters (density by differential weighing, pH by pH metry, chemical composition) of three samples from different premixing plants have been analyzed to evaluate the quality of the discharges. Applicable solutions and technological improvements are proposed in the mixer washing process in order to reduce the volume of entrained solids, without disturbing the environment, and making it possible to save water. Finally, with the chosen flocculant and the results obtained, the economic optimization produced by this method for cleaning ready-mix concrete mixers will be analyzed. / Tesis

Water is an essential and indispensable component is the pulp- and paper production industry.The increase in energy costs, stricter environmental regulations and water resource shortageshave caused a reduction of the water footprint in the industry as well as an increase in waterrecycling and water circuit closure. Reducing water usage requires an understanding of wherecontaminants originate, as well as which streams are critical to the process and how they impactmill operation. The recirculation of water can cause contaminant accumulation; therefore millsemploy technologies for water treatment in the internal water cycles, the so-called ‘kidneys’.Application of membrane technology is one such option which can improve the recycled waterquality and reduce contaminant buildup.The present study was carried out on a lab-scale for the treatment of a tissue mill effluent usingmembrane separation. A combination of pretreatment methods and various membranes werecompared with regards to separation, flux and fouling. The AlfaLaval M20 device was to treatwastewater samples sent from the mill, where the permeate was recirculated to the feed tank.COD and TOC levels are compared with regards to determining the separation efficiency. Thepermeate flux was measured over the two-hour filtration period, as well as flux recovery todetermine fouling levels. Additionally, some economic aspects of the process are discussed.This study suggests the potential application of a combination of flocculation or centrifugationpretreatment, with reverse osmosis membranes for recycling water to replace freshwater intake.The results also indicate the possibility of using ultrafiltration as kidneys to decreasecontamination buildup for further water loop closure.

Reverse osmosis (RO) is widely used for water reuse and desalination. Although RO membranes are known for their high salt rejection and practical permeate flux, their performance can be impaired by fouling, and their removal of some disinfection byproducts and their precursors (e.g., bromide, N-Nitrosodimethylamine [NDMA]) does not meet drinking water standards. RO membrane modifications have been widely studied to overcome these limitations. In this research, RO membranes were grafted with cationic polymers to induce a positive charge on the RO membrane surface. This modification aimed at enhancing the rejection of negatively charged bromide ions by removing them from solution by binding them to the membrane surface. The results showed that the modified (positively charged) RO membranes achieved lower rejection (82% rejection) for bromide ions compared to the unmodified ones (94.5% rejection). This behavior was likely a result of increased concentration polarization of the bromide ions at the membrane surface and/or increase in porosity of the modified membranes. Calculations based on the film theory indicate that the concentration of bromide ions at the surface of the modified membrane was 1371 ppm compared to 1307 ppm at the surface of the unmodified membrane. Evidently, the polymer attraction energy was not sufficient to keep the bromide ions attached to the membrane surface and prevent their diffusion across the membrane. Although the goal of the modification in the current study (i.e., enhancing removal of bromide ions) was not met, the permeate flux of the modified membrane was improved compared to the unmodified one. The literature suggests that increasing flux after modification is likely a result of increase in membrane pore size and hydrophilicity. In addition to the experimental work conducted in this study, a multi-criteria decision analysis was performed to prioritize research on surface modifications of reverse osmosis membranes. It was found that surface modifications have been mainly focused on reducing membrane fouling and to a much lower extent on removal of disinfection byproducts and their precursors. The RO membrane modification alternatives for fouling reduction and N-Nitrosodimethylamine (NDMA) removal were ranked based on multiple criteria using the Analytical Hierarchy Process (AHP) and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). This multi-criteria decision analysis process resulted in the identification of the top five promising modifications to reduce fouling and improve NDMA rejection. Grafting and coating the RO membranes with complex polymeric salts were the highest ranked modification approaches to reduce fouling. Heat-treatment of RO membranes achieved the highest NDMA rejection (98%); however, this technique was the second highest ranked modification approach for NDMA removal because it scored lower for other evaluation criteria.

The number of regions undergoing water scarcity, where the quantity of available water is not enough to meet human demand, is expected to increase in the future. Water reuse measures have been widely implemented to face these situations as a means of increasing the supply of water resources. Thus, ‘water scarcity – water reuse’ (WS-WR) situations will likely become more common. In these cases, water resources management to secure enough water supply is key. Risk and sustainability concepts have been consolidated as guiding discourses that also support the management of water resources. In particular, in the case of WS-WR situations, they can guide decision-makers towards reducing the risk of water scarcity and striving for the implementation of sustainable water reuse measures. In particular, the use of risk and sustainability assessments helps to deal with various social, economic, and environmental requirements and constraints. However, there is still the call for a more comprehensive and integrated assessments. This dissertation aims at providing new ideas for the integration of risk and sustainability in the case of WS-WR situations. Three objectives guide this research: (A) to develop a conceptual assessment framework to support decision-making concerning sustainable water reuse in regions facing risk of water scarcity; (B) to advance the conceptual framework interrelating existing risk and sustainability assessment methodologies and indicators in the context of decision support; and (C) to test the conceptual and methodological framework using a case study in Latin America. Each objective is associated with a research question: (RQ1) How is decision-making regarding water reuse understood and supported towards reducing the risk of water scarcity sustainably – and how can it be represented in a conceptual assessment framework?; (RQ2) How can a conceptual framework for assessing water reuse as sustainable water scarcity risk reduction measures be operationalised through a methodological framework?; and (RQ3) What are the findings from testing the framework in a case study – and what can be incorporated into the framework? Each objective and its respective research question was addressed as a separate step of the research approach, comprising the development of an integrated Risk and Sustainability Assessment (RSA) Framework for WS-WR situations, its operationalisation and testing. The research approach followed a deductive to inductive rationale relying on qualitative and quantitative methods. The outputs of this research are three scientific publications that build this cumulative dissertation (two published and one submitted for revision). The development of the conceptual framework followed three steps: (i) defining the concepts of ‘water scarcity’, ‘water reuse’, ‘risk’ and ‘risk assessment’, ‘sustainability’ and ‘sustainability assessment’, and ‘decision-making’; (ii) integrating these concepts by interpreting water scarcity from a risk perspective and water reuse from a sustainability perspective, and relating assessments with decision-making; and (iii) structuring the RSA Framework, following a risk assessment and framing it by the social, economic, and environmental dimensions of sustainability. Results allowed defining decision-making in WS-WR situations as a four-step cyclic process that can be supported by an integrated RSA that comprises an analysis (descriptive and objective) and evaluation (subjective). The methodological aspects for the operationalisation of the RSA conceptual framework focused mainly on developing an analytical concept to support an adequate derivation of the information required in an integrated RSA for WS-WR situations. The resulting concept is based on (i) understanding the WS-WR situation as a Coupled Human and Natural System (CHANS) and identifying the main biophysical elements (endpoints); (ii) translating the CHANS endpoints into an information system via a Multi-Layer (ML) approach using generic descriptors and specific indicators; and (iii) identifying and characterising interlinkages between the indicators via a Lane-Based (LB) approach. Additional methodological aspects related to the evaluation include the use of indicator-based multi-criteria decision-making methods that include the weighting and aggregation of these indicators, as well as the selection of threshold values as evaluation criteria. The testing of the integrated RSA Framework was carried out in Cerrillos de Tamaya, Chile. It involved an ex-post RSA of a water reuse measure implemented in 2018 to face the local water scarcity situation. The testing included (i) describing the case study location and adapting the RSA Framework to fit the local context; (ii) translating the case study’s CHANS via the ML approach and identifying and characterising interlinkages via the LB approach; and (iii) evaluating the degree of risk of water scarcity and sustainability of water reuse via the distance-based method TOPSIS. The results of the testing provided feedback for the RSA Framework. These mainly referred to the influence of the conceptualisation behind the indicators and their use, and the methodological challenges for integrating risk and sustainability evaluation. Further recommendations to the RSA framework are: the inclusion of interlinkage directionality; the use of existing system dynamics modelling approaches (e.g., CLD, SFD); the development of an established database of indicators; the automation of the interlinkages analysis (LB approach); and advance the use of scenarios for sustainability evaluation for better coupling with risk evaluation methods. Overall this research provides evidence of (a) the conceptual integration of risk and sustainability discourses under one decision support framework for the case of WS-WR situations; (b) the use of a system thinking approach for interpreting the WS-WR situation; (c) the relevance of indicators as a means of representing the situation; (d) the interlinkage of social, economic, environmental information; (e) the benefits of the use of conceptual maps; (f) gaps in the process of measuring the effect of water reuse on water scarcity levels via indicators; (g) the gap between a simulation-based risk assessment and a snapshot-focused sustainability assessment that hinders an operational integration; (h) the possibility of the RSA framework to bridge a system thinking view with a traditional assessment-based decision-making view.:Acknowledgements Abstract Contents List of Figures List of Tables Acronyms and Abbreviations Symbols Chapter 1 - Introduction 1.1 Background and problem statement 1.1.1 Water resources for water security 1.1.2 Risk and sustainability discourses for water-related decision-making 1.1.3 Problem statement and research focus 1.2 Objectives and research questions 1.3 Research approach and structure of the document 1.3.1 Research approach 1.3.2 Structure of the document 1.4 Chapter references Chapter 2 - Conceptual Framework 2.1 Introduction 2.2 Developing the conceptual framework 2.2.1 Definition and interpretation of the subject at stake 2.2.2 Identification and definition of key concepts 2.2.3 Construction of the conceptual framework 2.3 Results and discussion 2.3.1 Defining and interpreting the ‘water scarcity – water reuse’ situation 2.3.2 Identifying and defining key concepts 2.3.3 Construction of the integrated RSA Framework 2.4 Conclusions and outlook 2.5 Acknowledgements 2.6 Chapter references Chapter 3 - Methodological Aspects 3.1 Introduction 3.2 RSA Framework for a WS-WR situation 3.3 Systems thinking in a WS-WR situation 3.3.1 Identifying elements of a WS-WR situation and its interpretation as a system 3.3.2 Translation of the CHANS into an information system 3.4 Characterisation and interlinkage of indicators 3.4.1 Type and number of indicators 3.4.2 Type and number of interlinkages 3.4.3 Indicator connectivity 3.4.4 Structuring via a lane-based approach 3.5 RSA analytical concept and exemplification 3.5.1 RSA analytical concept 3.5.2 Exemplification of the analyitical concept 3.6 Discussion 3.6.1 Translating the CHANS into an information system 3.6.2 Supporting decision-making via the analytical concept 3.7 Conclusions 3.8 Acknowledgements 3.9 Chapter references Chapter 4 - Framework Testing 4.1 Introduction 4.2 Approach 4.2.1 RSA Framework 4.2.2 Case study site 4.3 Results 4.3.1 Analysis 4.3.2 Evaluation 4.3.3 General results for the case 4.4 Discussion 4.4.1 Analysis 4.4.2 Evaluation 4.4.3 Overall discussion on the testing of the RSA Framework 4.5 Conclusions 4.6 Acknowledgements 4.7 Chapter References Chapter 5 - Synthesis 5.1 Conceptual aspects 5.2 Methodological aspects 5.3 Testing aspects 5.4 Placing the RSA Framework in a broader context 5.5 Chapter References Chapter 6 - Conclusions and Outlook Annexes Annex A - Literature review: Found records Annex B - Example list of endpoints, descriptors, indicators, and attributes Annex C - Technique for Order Preference by Similarly to Ideal Solution (TOPSIS) Annex D - Translation into the Information System (from endpoints to attributes) Annex E - Interlinkages Identification Matrix Annex F - List of Most Interlinked Indicators (MII) Annex G - List of indicators, scores, and thresholds

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Providing sustainable access to water and energy is among the grand engineering challenges in the 21st century. Notably, many pressing issues at the water-energy nexus can be addressed by effective ion separations, such as desalination, nutrient recovery from wastewater, and extraction of energy-related elements from unconventional sources. One tool for such separations is ion-exchange membranes (IEMs), which are charged polymeric thin films. However, conventional IEMs face several performance constraints and fail to achieve ion-specific selectivity. This thesis aims to advance the potential of IEMs for separations at the water-energy nexus. Present-day IEM processes, e.g., electrodialysis (ED) desalination and reverse electrodialysis (RED) power generation, commonly employ the membranes as charge-permselective barriers, transporting oppositely-charged counterions while retaining like-charged co-ions. However, the increase in charge permselectivity is accompanied by a decrease in ionic conductivity, which forms a conductivity-permselectivity tradeoff and crucially limits separation efficiency. This work models IEM conductivity and permselectivity as functions of intrinsic membrane chemical and structural properties, simulating the performance of IEMs in a range of ED and RED operations (Chapter 2). Bulk solution concentration is identified as an external cause for the tradeoff, which confines current IEM applications to sub-seawater salinities. The structure-property-performance analyses reveal membrane water sorption as an intrinsic determinant of the tradeoff, while indicating that increasing ion-exchange capacity and reducing thickness can yield highly selective and conductive IEMs. To depart from this tradeoff, nanocomposite cation-exchange membranes (CEMs) with percolating 1-D sulfonated carbon nanotube (sCNT) network are fabricated (Chapter 3). Membrane conductivity is raised with greater sCNT blending in the polymer matrix (increasing by ≈30% with 20 w/w% incorporation of sCNT), while permselectivity is effectively unchanged (within 2% variation). Further characterization displays sCNT percolation beyond 10 w/w% blending, attributing the conductivity improvement to the interconnected sCNT network. The results imply the potential to advance the conductivity-permselectivity tradeoff with rationally designed nanostructures. Next, this thesis moves from the conventional charge-discriminating selectivity to ion-specific selectivity (Chapter 4), which is urgently needed but underdeveloped due to insufficient understanding of the fundamental transport phenomena. Here, a transport framework is presented to describe counterion migration mobility using an analytical expression based on first principles. The two governing mechanisms are: spatial effect of available fractional volume for ion transport and electrostatic interaction between mobile ions and fixed charges. Mobilities of counterions with different valencies are experimentally characterized, showing high regression R²s with the mobility model. The influence of membrane swelling caused by different counterions is further accounted for, while the frictional effect of electrostatic interaction is quantitatively linked to fixed charged density and dielectric constant of membranes. Additionally, the anion-exchange membrane (AEM) exhibits a weaker electrostatic effect compared to CEMs, which is attributed to the steric hindrance of the quaternary ammonium functional groups. Last, the membrane-level knowledge is extended to two process-level applications, coupling desalination with sustainable energy and desalinating hypersaline brines. This thesis presents a novel low-grade-heat-driven desalination process (Chapter 5), using CEM and AEM Donnan dialysis (DD) stepwise to remove salt ions, e.g. Na+ and Cl-, with a receiver solution of thermally-recoverable solute NH₄HCO₃. NH₄HCO₃ in the streams is later recycled by low-grade heat. The concept is experimentally validated by desalinating brackish water (100mM NaCl) to freshwater salinity (< 17mM). DD desalination of larger ranges of feed and receiver concentrations was then demonstrated, and module-scale analysis quantified the improvements of countercurrent operation to desalination efficiency. Another challenge in water management is the desalination of hypersaline brines. While demand is rapidly increasing, the wider application of hypersaline desalination is held back by considerable technical obstacles. Here, theoretical analyses are carried out to assess the potential of hypersaline ED desalination (Chapter 6). We show that desalination performance is impacted by the interrelated charge-discriminating selectivity and ion-water selectivity of IEMs. The work demonstrates lower energy costs of ED compared to thermal processes, when desalinating 1.0-1.5 M NaCl, and identifies three key performance-determining tradeoffs: conductivity-permselectivity, conductivity-water resistivity, and energy cost-volume reduction factor. To enable highly efficient hypersaline ED, ultra-low swelling IEMs need to be developed. Overall, this work advances mechanistic understanding, membrane development, and process design of IEMs. The thesis contributes insights to breaking conductivity-permselectivity performance constraints and developing highly valued ion-specific selectivity. The informed membrane fabrication and process design provide access to unconventional water sources with less energy input. The findings of the thesis will enable the systematic development of more ion separation processes to address challenges at the water-energy nexus.

The hypothesis tested in this study is that the application of ozone to reuse aquaculture water provides more favorable conditions for hybrid striped bass at production levels. Evaluation of water quality in fish culture systems being treated with ozone was made during a production trial (1200 fish/14,OOO 1). Originally, a control and four ozonated systems with doses of 3, 13, 25, and 45 g O3/kg feed/day supported fish for experimentation but, due to mechanical failure, only the control, the 13 and 25 g O3/kg feed/day treatments completed the full 35 week study. On an equal feeding basis, concentrations of dissolved organic carbon (DOC), carbonaceous biochemical oxygen demand (CBODs), and chemical oxygen demand (COD) were lowest in the most heavily ozonated systems. Ozone increased the biodegradation of DOC. Total suspended solids, particle size and distributions were impacted by ozone's flocculating properties. The percentages of particles in the smallest size range, 5-20 microns, were greater in the control system than the ozonated systems during weeks of equal feeding rates. When feeding rates differed, the control system maintained a larger number total particles per kilogram of feed administered. The pH of the ozonated systems was lower than the control which favored the ionized (less toxic) form of ammonia. Enhanced biodegradation of organics in the ozonated systems may have increased carbon dioxide production and caused a decline in pH. Greater nitrification in the ozonated systems may have also decreased the pH. Higher total ammonia nitrogen (TAN) levels were produced in the control on an equal feeding basis. Average weekly TAN t unionized ammonia (NH3), nitrite and nitrate concentrations remained at acceptable levels across treatments and throughout the production trial. Overall, the major indication of improved system conditions due to ozone treatment was that fish raised in the ozonated systems fed steadily throughout the growth trial while the control system's culture experienced periods of reduced feeding. / Master of Science

Current treatment of wastewater can effectively remove the contaminants; however, the effluent is still not widely reused because of some undesired substances like pathogens and trace organic chemicals. To promote water reuse, membrane-based technologies have emerged as a robust and more efficient alternative to current treatment practice. Among these membrane processes, forward osmosis (FO) utilizes an osmotic pressure gradient across a semi-permeable membrane to reclaim high-quality water. Still, several key challenges remain to be addressed towards broader FO application, including energy-intensive draw regeneration to yield product water and salinity buildup in the feed solution. To bypass energy-intensive draw regeneration, commercial solid fertilizers was utilized as a regeneration-free draw solute (DS), harvesting fresh water towards direct agricultural irrigation. However, using nutrient-rich fertilizers as DS resulted in an elevated reverse solute flux (RSF). This RSF, known as the cross-membrane diffusion of DS to the feed solution, led to deteriorated solute buildup on the feed side, reduced osmotic driving force, increased fouling propensity, and higher operation cost. To effectively mitigate solute buildup while achieving energy-efficient water reclamation, a parallel electrodialysis (ED) device was integrated to FO for DS recovery in the feed solution. The salinity in the feed solution was consistently controlled below 1 mS cm-1 via the hybrid FO-ED system. Considering solute buildup is merely a consequence of RSF, direct control of RSF was further investigated via operational strategy (i.e., an electrolysis-assisted FO) and membrane modification (i.e., surface coating of zwitterion-functionalized carbon nanotubes). Significantly reduced RSF (> 50% reduction) was obtained in both approaches with minor energy/material investment. With two major bottlenecks being properly addressed for energy-efficient water reclamation, FO was further integrated with a microbial electrolysis cell (MEC) to achieve integrated nutrient-energy-water recovery from high-strength wastewater (i.e., the digestor centrate). The abovementioned research projects are among the earliest efforts to address multiple key challenges of FO during practical application, serving as a cornerstone to facilitate the transformation of current water/wastewater treatment plant to resource recovery hub in order to ensure global food-energy-water security. / Doctor of Philosophy / Exploring alternative water supply, for instance via reusing wastewater, will be essential to deal with the global water crisis. Current wastewater treatment can effectively remove the contaminants; however, the treated wastewater is still not widely reused due to the possible presence of residual contaminants. In recent years, membrane-based technologies have emerged as a promising treatment process to produce clean water. Among all available membrane technologies, forward osmosis (FO) takes advantage of the osmotic pressure difference across a special membrane to extract fresh water from a low-salinity FEED solution (for example, wastewater) to a high-salinity DRAW solution. The reclaimed fresh water can be reused for other applications. Still, the FO process is facing several critical challenges for broader applications. The first challenge is that additional energy is required to separate clean water from the diluted DRAW solution, leading to notably increased energy consumption for the FO process. To bypass this energy-intensive separation, commercial solid fertilizers was utilized as a separation-free DRAW solution for FO process. Once the clean water is extracted to the DRAW solution (fertilizer), the diluted fertilizer solution together with the fresh water can be directly used for agricultural irrigation. The second challenge is that, when fertilizer is applied as the DRAW solution, nutrient rich fertilizers can penetrate the FO membrane and escape to the FEED solution (wastewater). This phenomenon is known as the reverse solute flux (RSF). RSF can result in many adverse effects, such as wastewater contamination and increased operational cost. To prevent this, we used an additional device named electrodialysis to effectively recapture the “escaped” fertilizers in the FEED solution. Besides this indirect approach to recover escaped fertilizers, we also investigated direct approaches to control RSF, including operational strategy and membrane modification. With two major challenges being properly addressed for energy-efficient water reclamation, FO was further combined with a microbial electrolysis cell (MEC) to achieve multiple resource recovery from wastewater, including water, nutrient, and energy components. The above mentioned research projects are among the earliest efforts to address multiple key challenges of FO during water and resource recovery from wastewater to ensure global food-energy-water security.

As demand for alternative water sources intensifies, increased use of reclaimed water is important to help achieve water sustainability. In addition to treatment, the manner in which reclaimed water is distributed is a key consideration as it governs the water quality at the point of use. In this work, simulated reclaimed water distribution systems (SRWDSs) were operated for more than two years to examine the role of system design, biofiltration, residual disinfectant type (i.e., chlorine, chloramine, no residual) and temperature on important aspects of chemistry and microbial regrowth under laboratory-controlled conditions. Turbidity decreased to 0.78 NTU after biofiltration and chlorinated treatments from 10.0-12.6 NTU for conditions with chloramine and no residuals. SRWDSs were susceptible to sediment accumulation, which occupied 0.83-3.2% of the volume of the first pipe segment (1 day of hydraulic residence time), compared to 0.32-0.45% volume in the corresponding chlorinated SRWDSs. The mass of accumulated sediment positively correlated (R2 = 0.82) with influent turbidity. Contrary to experiences with potable water systems, chlorine was found to be more persistent and better at maintaining biological stability in the SRWDSs than chloramine, especially at the higher temperatures >22°C common to many water scarce regions. The severe nitrification at the warmer temperatures rapidly depleted chloramine residuals, decreased dissolved oxygen, and caused elevated levels of nitrifiers and heterotrophic cell counts. A metagenomic taxonomic survey revealed high levels of gene markers of nitrifiers in the biofilm samples at 22°C for the chloraminated system. Non-metric multidimensional scaling analysis confirmed distinct taxonomic and functional microbial profiles between the chlorine and chloramine SRWDSs. Reflecting on multiyear experiences operating two different SRWDSs reactor designs, including thin tubes (0.32-cm diameter) and pipe reactors (10.2-cm), illustrated strengths and weaknesses of both approaches in recreating key aspects of biochemical changes in reclaimed water distribution systems. It is clear that approaches deemed successful with drinking water distribution systems may not always directly transfer to simulating reclaimed distribution systems, or to proactively managing full-scale reclaimed systems that have long periods of stagnation and where minimally-treated wastewater with high levels of nutrients and turbidity are used. / Doctor of Philosophy / Increasing water scarcity is creating an impetus for creating more sustainable water supplies. Wastewater effluent is increasingly viewed as in important resource that can reduce both water and energy demand. Reclaiming moderately to minimally-treated secondary wastewater effluent for non-potable reuse (NPR) applications; such as agricultural irrigation, landscaping, and toilet flushing, helps reduce demand for higher quality potable water sources. NPR presently accounts for more than 50% of total reuse and is projected to become increasingly important. While NPR is attractive, important knowledge gaps remain in terms of managing water quality and safety as it is transported through distribution pipes to the point of use. A comprehensive literature review revealed that NPR distribution systems are distinct from conventional drinking water distribution systems (DWDSs) and that it is doubtful if our current understanding of DWDSs would directly transfer to NPR systems. Unlike drinking water systems, NPR systems are currently unregulated at the national level and corresponding state-to-state regulations vary widely. The levels of water treatment can vary from simply distributing untreated effluent from wastewater treatment plants to very high-level treatment with membranes that produces water of equal or even higher quality than many existing tap waters. A common treatment train for minimally-treated NPR involves biologically activated carbon (BAC) filtration and the use of disinfectants (e.g., chlorine or chloramine) to control microbial water quality to the point of use. Prior studies from DWDSs have demonstrated water quality degradation in terms of disinfectant loss, bacterial growth, and aesthetic problems, with the settling of trace particulate matter producing sediment within pipe distribution systems. In particular, accumulated sediment can become a hotspot for water quality deterioration. Considering that minimally-treated reclaimed water can have much higher levels of particulate matter and nutrients than drinking water, it was predicted that NPR distribution systems could suffer from faster water quality degradation than corresponding drinking water systems, especially at the warmer temperatures common in water-scarce regions. This work was the first multi-year attempt to examine the effects of disinfectant (i.e. free chlorine, chloramine, no residual), BAC filtration versus no filtration, water age (up to 5-d versus 28-min), and temperature (14°C, 22°C, 30°C) in different types of lab-scale reactors. Two simulated reclaimed water distribution systems (SRWDSs) including 4-in. diameter Pipe SRWDSs versus 1/8-in. diameter Tube SRWDSs, were designed to study key aspects of full-scale NPR systems and were operated for more than two years to study chemical and microbial changes as distributed water traveled through the two systems. The Pipe SRWDSs were designed to assess the impacts on final water quality after long-term operation that allowed sediment to slowly accumulate, whereas the complementary Tube SRWDS design did not allow sediment to accumulate and only held the water for 28 minutes. Water was sampled regularly to track the trends of key water quality parameters, including disinfectant residuals, dissolved oxygen, nitrogen compounds involved in nitrification reactions, and various types of bacteria of interest. Sequencing of the biological genetic materials on selected samples was conducted to understand the types of bacteria present and their functions under the different circumstances. High levels of sediment were found to accumulate near the beginning of the Pipe SRWDSs, which caused loss of oxygen and disinfectants at the bottom of the pipes. Chlorine was more persistent and better at preventing bacteria growth as water traveled through the distribution system. In contrast, a type of bacteria that used ammonia as a nutrient (i.e., nitrifying bacteria) were observed in the pipes with chloramine (i.e., ammonia plus chlorine) as the disinfectant. The nitrifying bacteria caused rapid depletion of chloramine residuals, especially at temperatures above 22°C. At 30°C both chlorine and chloramine were almost immediately consumed in the pipe reactors. Nitrification is known to trigger water quality problems in chloraminated DWDSs, and we expect that chloraminated RWDSs would be even more susceptible to nitrification and associated water quality degradation issues in Compare the Tube SRWDSs to the Pipe SRWDSs, aside from heavy accumulations of sediment in the pipes versus no sediment in the thin tubes, the tubes clogged repeatedly from formation of thick biofoulants in the systems treated with no disinfectant and chloramine, whereas they remained relatively free of biofoulants and clogging in the tubes with chlorine. Even in just 28 minutes, it took water to move from the start to the end of the tube, both chlorine and chloramine were almost completely consumed in the tubes, due to the unrealistically high pipe surface area to the small flow volume inherent to this reactor design. As NPR becomes increasingly common to help achieve water sustainability, it will be important to deploy laboratory simulations, that are capable of testing and revealing key chemical and microbial processes that affect the operation of these systems and water safety at the point of use. The insights from this first long-term effort of simulating RWDSs highlight some unique characteristics and challenges of RWDSs, and reveals key concepts to help guide future research.