Biofouling represents the main problem in membrane filtration systems. Biofouling arises when the biomass growth negatively impacts the membrane performance parameters (i.e. flux decrease and feed channel pressure drop). Most of the available techniques for characterization of biofouling involve membrane autopsies, providing information ex-situ destructively at the end of the process. OCT, is non-invasive imaging technique, able to acquire scans in-situ and non-destructively. The objective of this study was to evaluate the suitability of OCT as in-situ and non-destructive tool to gain a better understanding of biofouling behavior in membrane filtration systems. The OCT was employed to study the fouling behavior in two different membrane configurations: (i) submerged flat sheet membrane and (ii) spacer filled channel. Through the on-line acquisition of OCT scans and the study of the biomass morphology, it was possible to relate the impact of the fouling on the membrane performance. The on-line monitoring of biofilm formation on a flat sheet membrane was conducted in a gravity-driven submerged membrane bioreactor (SMBR) for 43 d. Four different phases were observed linking the variations in permeate flux with changes in biofilm morphology. Furthermore, the biofilm morphology was used in computational fluid dynamics (CFD) simulation to better understand the role of biofilm structure on the filtration mechanisms. The time-resolved OCT analysis was employed to study the biofouling development at the early stage. Membrane coverage and average biofouling layer thickness were found to be linearly correlated with the permeate flux pattern. An integrated characterization methodology was employed to characterize the fouling on a flat sheet membrane, involving the use of OCT as first step followed by membrane autopsies, revealing the presence of a homogeneous layer on the surface. In a spacer filled channel a 3D OCT time series analysis of biomass development under representative conditions for a spiral-wound membrane element was performed. Biomass accumulation was stronger on the feed spacer during the early stage, impacting the feed channel pressure drop more than the permeate flux. OCT biofilm thickness map was presented as new tool to evaluate the biofouling development in membrane filtration systems through the use of a false color scale.

Alongside the proliferation of large water infrastructure projects such as dams and storage reservoirs, the pursuit of desalination materialized at a moment when an unwavering belief in the power of technology to shape the future existed, when international scientific collaboration increased, and when political concerns about water as a limited resource accelerated. Its potential as a new, untapped source of fresh water for municipal, agricultural, and industrial purposes carried promises of modernization and development, and especially appealed to governments looking to develop, diversify, and decentralize sources of supply. Yet, while initially hailed as a cheaper and more flexible alternative to centralized infrastructure, desalination ended up requiring the same major investments in capital and energy. It also portended a set of similar environmental impacts. By the early 1970s, the pursuit of desalination ground to a halt owing to government cutbacks and a lack of institutional support, as priorities changed from finding new sources of fresh water to protecting already-existing water sources from contamination. This dissertation presents a multilayered view of desalination thought and practice in the 1950s and 1960s: national, intergovernmental, and transnational. A loosely allied group of scientists, politicians, and officials firmly believed in the potential of desalination, and constituted examples of the midcentury “hydronaut”: a person who considered existing water scarcity as one of the most important impediments to future economic growth and prosperity, and approached the quest for water with a sharp sense of mission. Throughout the 1950s and 1960s, hydronauts in the United States, the Netherlands, Tunisia, Chile, the United Kingdom, and within the United Nations system considered desalination as a new and innovative strategy to achieve interrelated policy objectives, all with the ultimate goal of creating a new source of fresh water free of the impediments created by water variability and availability, and able to compete with more conventional sources of supply. While not as successful or visible as the proliferation of dams, the pursuit of desalination in the 1950s and 1960s nonetheless illustrates that the hydraulic paradigm took hold in different and multiple forms. As governments, stakeholders, and development partners looked to confront water-related challenges from the supply side, and aimed to maximize the efficient use of water resources through new technological interventions, desalination offered an alternative means to transmit ideas about national identity, development strategies, economic progress, technological prowess, and the material realities of water itself. By uncovering how several countries and international organizations imagined the potential of desalination, and tried to jumpstart its widespread adoption, “Pipe Parity” complicates and adds additional layers to understandings of the development era. / 2027-06-30T00:00:00Z

No / Multi Stage Flash (MSF) desalination plants are a sustainable source of fresh water in arid regions. Modelling plays an important role in simulation, optimisation and control of MSF processes. In this work an MSF process model is developed, using gPROMS modelling tool. Accurate estimation of Temperature Elevation (TE) due to salinity is important in developing reliable process model. Here, instead of using empirical correlations from literature, a Neural Network based correlation is used to determine the TE. This correlation is embedded in the gPROMS based process model. We obtained a good agreement between the results reported by Rosso et. al. (1996) and those predicted by our model. Effects of seawater temperature (Tseawater) and steam temperature (Tsteam) on the performance of the MSF process are also studied and reported.

yes / Boron is a vital element for growth of creations, but excessive exposure can cause detrimental effects to plants, animals, and possibly humans. Reverse Osmosis (RO) technique is widely used for seawater desalination as well as for waste water treatment. The aim of this study is to identify how different operating parameters such as pH, temperature and pressure can affect boron concentrations at the end of RO processes. For this purpose, a mathematical model for boron rejection is developed based on solution-diffusion model which can describe solvent and solute transport mechanism through the membranes. After a wide and thorough research, empirical correlations developed in the past are filtered, adopted and calibrated in order to faction with reliability as part of the solution-diffusion model of this work. The model is validated against a number of experimental results from the literature and is used in further simulations to get a deeper insight of the RO process. The general findings of the boron rejection model are supporting the case that with increasing pH and operating pressure of the feed water, the boron rejection increases and with increasing feed water temperature the boron rejection decreases.

Global increases in water demand and decreases in both the quantity and quality of fresh water resources have served as the major driving forces to develop sustainable use of water resources. One viable alternative is to explore non-traditional (impaired quality) water sources such as wastewater and seawater. The current paradigm for wastewater treatment is based on technologies that are energy intensive and fail to recover the potential resources (water and energy) in wastewater. Also, conventional desalination technologies like reverse osmosis (RO) are energy intensive. Therefore, there is a need for the development of sustainable wastewater treatment and desalination technologies for practical applications. Processes based on microbial electrochemical technologies (METs) such as microbial fuel cells (MFCs), microbial electrolysis cells (MECs) and microbial desalination cells (MDCs) hold promise for the treatment of wastewater with recovery of the inherent energy, and MDCs could be used for both desalination of seawater and energy recovery. METs use anaerobic bacteria, referred to as exoelectrogens, that are capable of transferring electrons exogenously to convert soluble organic matter present in the wastewater directly into an electrical current to produce electrical power (MFC and MDC) or biogas (MEC). In my dissertation, I investigated the three types of METs mentioned above to: 1) have a better insight on the effect of 4 oxygen intrusion on the microbial community structure and performance of air-cathode MFCs; 2) improve the desalination efficiency of air-cathode MDCs using ion exchange resins (IXRs); and 3) enrich for extremophilic exoelectrogens from the Red Sea brine pool using MECs. The findings from these studies can shape further research aimed at developing more efficient air-cathode MFCs for practical applications, a more efficient integrated IXRMDC configuration that can be used as a pre-treatment to RO, and exploring extreme environments as a source of extremophilic exoelectrogens for niche-specific applications of METs.

Yes / Multistage Flash (MSF) desalination process is still a dominant process, especially in the Gulf region, to produce high quality freshwater. Although there has been energy price surge in recent years, MSF process will continue to operate in that region for some foreseeable future. The key challenge is how to make such processes still profitable. Understanding the dynamics of any processes under uncertainty and disturbances is very important to make a process operationally feasible and profitable. The main aim of this work is to understand the dynamics of industrial scale MSF process using high fidelity and reliable process model. For this purpose, a detailed dynamic model for the MSF process incorporating key and new features is developed and validated against the actual data of a large-scale seawater desalination plant. The model is then used to study the behaviour of large scale MSF processes for disturbances in steam temperature, feed temperature and the recycle brine flow rate. The simulation results show that the last stage requires a longer time to settle compared to the preceding stages. In addition, steam temperature shows insignificant influence on the performance ratio compared to the inlet seawater temperature and recycle brine flow rate. Furthermore, it is found that the productivity of plant can increase in the winter compared to that in the summer. However, this benefit comes at the expense of increased steam consumption in the winter, resulting in a low performance ratio.

The present research work caters to two important needs of rural India: i) desalination of subsoil/coastal brackish water and ii) basic refrigeration for short term preservations of agro-produce, medicines etc. Fortunately, such places are blessed with abundant solar insolation and/or low grade thermal energy (< 100°C) is available which may be tapped for this purpose instead of relying solely on grid electricity. Both the objectives of desalination and cooling are realized by evaporating brackish water at a low pressure (~1 kPa) and thermally compressing the water vapour to a higher pressure before condensing it. Adsorption route is chosen for compression where silica gel is the adsorbent and water to be desalinated as the refrigerant. The objective of this study is to develop a laboratory prototype of a two-stage adsorption cooling cum desalination system driven by low grade heat source. The entire system is air-cooled which is necessitated by non-availability of heat exchange grade cooling water. Initially various experimental and theoretical studies are carried out for characterizing silica gel + water pair which is fundamental to the system design. RD type silica gel is used in this study due to its high uptake capabilities. The uptakes for this adsorption pair at various pressure and temperature conditions are measured using a specially designed isothermal adsorber cell connected to an evaporator. Subsequently, a modelling study of adsorption kinetics is performed for a monolayer of silica gel in order to estimate the adsorption time scale. This time scale is used as an input for the scaling analysis of columnar packed silica gel bed. The scaling analysis showed that the thermal diffusion time scale limits the adsorption process. It also showed that for a given thermal length scale, the bed has a unique vapour flow length scale beyond which the adsorption phenomenon gets limited due to pressure drop. The scaling results are validated by simulation studies. A shell-and-tube heat exchanger is chosen for the adsorber which closely mimics the columnar silica gel packing studied in scaling analysis. The heat exchanger is designed for radial entry of vapour. A modelling study is performed on ANSYS® Fluent platform for optimising the tube pitch by minimising the overall thermal capacitance of the bed. The shell diameter is determined for this tube pitch based on the vapour flow length criterion established through scaling. To experimentally study the effect of pressure drop on bed performance, the radial entry of vapour is closed for 1 bed/stage (out of the 4 beds/stage) enforcing the vapour to flow along the longer axial dimension. The system is generously instrumented for precise measurements and control over the various experimental parameters. For the functioning of the adsorber system, various vapour valves and water (heat transfer fluid) valves need to be operated in a cyclical and synchronized manner. Individual components are fitted with pressure, temperature and water flow sensors. The entire operation and data acquisition for the adsorption system has been automated using National Instruments® (NI) PXIe controller executing an in-house developed code written on NI Labview® platform. To simulate solar/waste heat input, multiple electrical heaters are used in this study and a constant temperature bath is used to simulate the cooling load at the evaporator. Prior to conducting experiments a 4-bed lumped dynamic model is developed based on the design data of the system to simulate the two-stage system performance for various input conditions. The study helped to optimise the performance of a two-stage system. The study also compares the two-stage and single-stage system performance for various ambient temperatures (25–40°C). The study revealed that for pressure lifts higher than 5 kPa a two-stage system is preferable. A detailed experimental study is conducted on the developed prototype by operating it in various conditions namely 2, 3 and 4–bed modes for single and two-stage operations; with 1.0–1.7 kPa evaporator pressures, half cycle time varying between 1200–3000s and source temperature in the range of 75–85°C. The system is operated indoors during summer conditions wherein the ambient temperature is found to be 36±1°C which is significantly higher than the design point of 25°C. This resulted in lower than expected throughput; however, the system performance variation is qualitatively similar to as predicted by the lumped model. A comparison between the experimental and simulated bed temperature revealed that the thermal wave during the switching of hot/cold water plays a significant role causing a large deviation from the simulation results. A comparative study is carried out between the beds with radial vapour flow to that with axial flow and the results validate the scaling criterion. Experimental results also depict that two-stage operation is favourable when the pressure lift required is larger than 5 kPa. Such large pressure lift is encountered when air-cooling is used in a tropical country like India.

Approximately 35% of the population of the Navajo Nation does not have direct access to the electric grid and public water supply. Tribal members haul their potable and livestock water from public water systems that are located great distances from their homes. The Navajo Nation Solar Desalination Research Pilot Demonstration Project is designed to provide residents affordable livestock water. The same technology can later be adopted to provide potable water. The project has deployed an off-grid, prototype water purification unit at a demonstration site north of Leupp, AZ utilizing membrane distillation (MD) technology. A second prototype for the same purposes utilizing nanofiltration (NF) membrane technology has been designed, built, and operated at The University of Arizona. Through experimentation I confirmed information provided the manufacturer of the NF membrane, calculated the production rate to be 636 gallons per day, and calculated the cost of desalinated water to be $0.003 per gallon. Both systems use solar energy to desalinate brackish ground water and the second prototype will later be deployed at the same site for side-by-side comparison. A critical part of the project is the development of technology transfer methods that will help the community take ownership of the project. To accomplish this goal I have written a comprehensive manual that will be given to the Navajo Department of Water Resources. The demonstration site will act as an applied research site for investigation, demonstration, and training related to sustainable water and energy systems designed to address the needs of remote, rural communities in arid and semi-arid regions. The aim is to inform a regional plan for Southwestern Navajo Nation Chapters to address chronic water and energy shortages, demonstrate renewable energy application for water treatment of brackish ground water, evaluate trade-offs in energy and water supplies, and foster community development. The research and demonstration site has been developed by an interdisciplinary and collaborative effort between the Bureau of Reclamation, Apex Applied Technology, Inc., and The University of Arizona.

Negatively buoyant jets are turbulent flows that are frequently employed by the desalination industry to disperse reject brines into oceanic environments. Although such brines are characterised by elevated concentrations of the same elemental components as the discharge environment contains, there is significant potential for marine ecosystem damage if this waste is not diluted properly. Numerous workers have analysed the dilution and spatial characteristics of negatively buoyant jets, but published data demonstrates notable inconsistencies. An important reason for these discrepancies is the variety of bottom-boundary conditions employed. This complicates comparison with predictions by integral models typically employed for discharge design, as these generally have not been developed with consideration to boundary interaction. In the present study, negatively buoyant jet experimental data is collected where bottom boundary distances are sufficiently large to avoid boundary influence at the point where the discharge returns to its source height (the return point). Near-field centreline dilution data is measured under still ambient conditions, for the source inclinations of 15–75°. Considerable attention is paid to experimental data quality, and all relevant issues are mitigated where possible. In order to ensure the boundary has no influence, source heights in this study range between 2.33 d F0 and 8.07 d F0. A variety of time-averaged and temporal statistics are calculated, and these statistics are compared with published experimental data and predictions by integral models. Normalised trajectory and dilution data from the source through to the return point collapses well at each inclination. The attention to signal quality and the self-consistency of derived experimental results in this study suggest a high level of accuracy, and large distances to the bottom boundary ensure that results are not confused by boundary interaction. Data for dilution rate at the return point supports the use of higher source inclinations (60° and 75°) to maximise dilution capability. A new ‘forced jet’ model is developed that incorporates the concept of a reducing buoyancy flux as the flow rises to maximum height. While this model is not applicable above source inclinations of 60°, predictions at other inclinations are reasonable. Dilution predictions are notably improved when compared to those from existing integral models. Finally, CFD simulations of negatively buoyant jets are conducted using the k-ε turbulence model. Despite the sophistication of this model, the quality of spatial and dilution bulk flow predictions at the centreline maximum height are no better than those obtained from the forced jet model or analytical solutions of Kikkert et al. (2007).

Water scarcity and high irradiance overlap in the southwestern United States. This thesis explores solar energy as a method to power desalination in the Southwest. Ten solar desalination plants were modeled using photovoltaic reverse osmosis and concentrated solar thermal multi-effect distillation. Seawater and brackish water were considered, as well as liquid and zero liquid discharge plants. Using borrowed capital amortization, levelized energy costs were estimated to be 0.067 $/kWh-electric for photovoltaic systems and 0.009 $/kWh-heat for thermal systems. Photovoltaic reverse osmosis with liquid plant waste showed the best short-term financials while optimal long-term solar desalination methods were shown to be arbitrary, limited by solar conversion and desalination thermodynamics. A conceptualization and proof of desalination minimum work is presented. This study concludes that solar desalination cost remains higher than conservation, but has considerable potential as a new source of water in the Southwest, filling the gap between overdraft and renewable supply.