Central Arizona Project water was treated using slow sand filtration (SSF) and reverse osmosis (RO) in series. Additional desalination water was recovered from RO brine using the vibratory shear-enhanced processing (VSEP®; New Logic, Inc.). SSF removed 90% of the turbidity in raw CAP water. SSF decreased total organic carbon by almost 20%. After a little more than a year of continuous operation, performance of the RO system declined noticeably, as indicated by a rapid decrease in membrane permeation coefficient and an increase in salt flux. Foulant scrapings contained both clay material and large amounts of unidentified organics. Alternative hypotheses regarding major sources of membrane foulants are discussed in this study.Water lost as brine was reduced from 20% to 2-4% via post-RO VSEP treatment. Estimated costs were compared to those of a no-VSEP option in which disposal of the entire RO brine flow was required. The total annualized cost of brine treatment was fairly insensitive to recovery during VSEP treatment in the range 80-90%, and the period of VSEP operation between cleanings in the range 25-40 hrs. These values define a fairly broad window for near optimal VSEP operation under the conditions of the study. The cost of VSEP treatment to minimize brine loss was estimated at $394- $430 per acre foot ($1.21 - $1.32 per 1000 gal) of 15 MGD CAP water treated. For a hypothetical 3 MGD RO brine flow, the use of VSEP to recover water and reduce the volume of brine for disposal results in a savings of more than $5M/year relative to the no-VSEP brine disposal alternative.

abstract: The horizontal desalination units belonging to the humidification-dehumidification family purify water using air as a carrier gas. The temperature required for separation can vary from ambient to 99 °C so waste heat, fuel combustion, or solar collectors can drive the process. A unit in which air flows horizontally affords several advantages over similar vertical “Dewvaporation” towers (as an example), including ease of construction and potentially increased efficiency. The objective was to build and test horizontal units and identify areas of potential efficiency improvements. The desalination units consisted of: 1.) A series of aligned, corrugated, polypropylene sheets covered on the outside with absorbent, water-wettable cloth. 2.) A basin that caught saline water flowing downward from the absorbent cloth. 3.) Ten pumps to cycle the basin water back onto the cloth. 4.) An air blower on the front of the unit that drove air horizontally across the cloth, increasing the humidity of the air. 5.) A steam generator on the back of the unit producing steam that mixed with the incoming air to increase the temperature and humidity. 6) A steam box that caused the air to mix with the steam and return to flow inside the corrugations in the plastic sheets, creating a countercurrent heat exchanger as the exiting air transferred its heat to the incoming air and causing purified water to condense from the cooling, oversaturated air. The tested unit produced distillate at a rate of 0.87 gallons per hour with 13 parts per million total dissolved solids and an energy reuse factor of 2.5. Recommendations include the implementation of a continuous longitudinal pump design, a modification of the basin to accommodate top and bottom unit center dividers, increase in insulation coverage, and optimization of air flow rate. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2015

The Lawrence Livermore National Laboratory (LLNL), in Berkley, California, developed a laboratory scale non-membrane electrosorption process known as Capacitive Deionization Technology™ (CDT™) for the continuous removal of ionic impurities in water. A saline solution flows through an unrestricted capacitor type module consisting of numerous pairs of high-surface area (carbon-aerogel) electrodes. The electrode material (carbon aerogel) contains a high specific surface area (400 – 1 100 m2/g), and a very low electrical resistivety (< 40 m<font face="symbol">W</font>.cm). Anions and cations in solution are electrosorbed by the electric field upon polarization of each electrode pair by a direct current (1,4 Volt DC) power source. Testing conducted on a laboratory scale unit at LLNL has proved that CDT™ has the potential to be an alternative desalination technology (Farmer5 et al., 1995). The primary objective of this research was to continue, where the laboratory scale research ended. Thus taking CDT™ from a laboratory scale technology to an industrial scale process, by developing and evaluating an industrial CDT™ prototype system. First, a process was developed to manufacture a cost effective industrial sized CDT™ module. During this process various manufacturing techniques were evaluated to produce an optimum prototype. As part of the developmental process the prototype was tested and water treatment efficiency results were first compared to results obtained on the laboratory scale module and secondly to established desalination technologies like reverse osmosis, electrodialysis, and distillation. Due to the wide variety of potential saline feed water sources, research for this dissertation focused on brackish water applications (which includes wastewater reuse applications). After establishing a cost effective small-scale model of a potential industrial manufacturing process, the prototype was tested with regard to water treatment efficiency. Test results on brackish type waters (1 000 mg/l), indicated that the industrial CDT™ prototype had an energy requirement of 0,594 kWh/1000 liters. Research results compared well to the laboratory scale energy consumptions of 0,1 kWh/1000 liters (Farmer5 et al, 1995) and to the best available existing brackish water membrane based desalination systems with energy requirements of 1,3 to 2,03 kWh/1 000 liters (AWWA, 1999). The thermodynamic minimum energy required (due to osmotic pressure) to desalinate a 0,1% or 1 000 mg/l sodium chloride solution, is 0,0234 kWh/1 000 liters. Development and evaluation results indicated that CDT™ industrial modules could be manufactured cost effectively on a large scale and that such units have the potential to be very competitive with existing technologies with regards to overall operational and maintenance costs. Therefore Capacitive Deionization Technology™ can be viewed as a potential alternative to membrane technologies in the future. Regardless of the benefits to the potable water industry, CDT™ have the potential to incur a dramatic step reduction in the operational costs of desalination plants, which will make desalination a more viable alternative technology for large-scale agricultural and industrial uses. / Dissertation (MEng (Waterutilization))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

This study investigates the operation of dual media filter DMF during ambient and simulated algal bloom conditions, and the role of coagulation and dissolved air flotation (DAF) in mitigating the adverse effects of algal blooms on DMF performance. The study also highlights which AOM concentration as a function of biopolymer is critical to organic fouling in DMF pretreatment for Red Sea water desalination with RO. On the other hand, the present study has carried out another experiment on AOM fouling in comparison with bacterial organic matter (BOM) and humic organic matter (HOM) using two different pore sizes of UF ceramic membranes, 5 and 50 kDa. The main aim of this comparison is to examine fouling behavior and mechanism and removal efficiency. The study revealed that AOM can induce organic fouling in DMF during simulated algal bloom conditions at biopolymer concentrations as low as 0.2 mg C/L. DMF performance was strongly affected by AOM concentration as observed by flow rate decline through time. Liquid chromatography – organic carbon detection (LC-OCD) analysis showed higher removal rates of biopolymers than lower molecular weight fractions (i.e., humic substances, building blocks and low molecular weight neutrals) for all pretreatment scenarios. The study also indicated that while DMF performance was enhanced with coagulation and sedimentation, the most significant improvement in performance was observed for DMF operation preceded by coagulation and DAF. Hydraulic performance of DMF correlated well with biopolymers removal, with removal rates of 72%, 53% and 39%, for coagulation/DAF, coagulation/sedimentation, and no coagulation, respectively. For UF ceramic membranes, results showed that more TEP/organics were removed by the 5 kDa membranes compared to the 50 kDa membrane, which is accounted for lower MWCO. The UF 5 kDa membrane also showed low fouling formation than 50 kDa membrane for all of three types of organic matter tested. Analysis of the fouled membranes by SEM images showed that fouling was dominated by cake layer formation for the 5 kDa membrane while pore blockage followed by cake layer formation is apparent for the 50 kDa membrane.

This research was undertaken to improve the understanding of structure-property-performance relationships in crosslinked polyamide (PA) thin-film composite (TFC) membranes as characterized by liquid and gas permeation studies. The ultrathin PA selective layer formed by interfacial polymerization between meta-phenylene diamine and trimesoyl chloride was confirmed to contain dense polymer matrix regions and defective regions in both dry and hydrated states. The first part of this research studied the effect of non-selective convection through defective regions on water flux and solute flux in pressure-assisted forward osmosis (PAFO). Through systematic comparison with cellulose triacetate (CTA) and PEBAX-coated PA-TFC membranes, the existence of defects in pristine, hydrated PA-TFC membranes was verified, and their effects were quantified by experimental and modeling methods. In the membrane orientation of selective layer facing the draw solution, water flux increases of up to 10-fold were observed to result from application of low hydraulic pressure (1.25 bar). Convective water flux through the defects was low (< 1% of total water flux for PA-TFC membranes) and of little consequence in practical FO or reverse osmosis (RO) applications. However, it effectively mitigated the concentration polarization in PAFO and therefore greatly increased the diffusive flux through the dense regions. The second part of this research characterized the structures of the PA material and the PA selective layer by gas adsorption and gas permeation measurements. Gas adsorption isotherms (N2 at 77K, CO2 at 273K) confirmed the microporous nature of PA in comparison with dense CTA and polysulfone materials. Gas permeation through the commercial PA-TFC membranes tested occurred primarily in the defective regions, resulting in Knudsen gas selectivity for various gas pairs. Applying a Nafion coating layer effectively plugged the defects and allowed gas permeation through the dense PA regions, which significantly decreased gas permeance and increased gas selectivity. Specifically, high He and H2 selectivity against CO2 suggests the potential applications of this membrane in He recovery and CO2 capture in pre-combustion. Finally, the dense PA matrix was modified with two types of novel nanofiller to improve desalination performance in RO. A series of dense, nano-sized (1-3 nm) polyhedral oligomeric silsesquioxanes (POSS) with different functional groups were systematically incorporated into the PA matrix by physical blending or chemical fixation. The free volume of the PA matrix increased with addition of POSS, leading to water flux increases of up to 67 %, while maintaining high NaCl rejections. The effects of adding microporous, hydrophobic zeolitic imidazolate framework-8 (ZIF-8) nanoparticles into PA are presented in the last chapter. A 162 % water flux increase was achieved without decreasing NaCl rejection. This interesting result can be attributed to a less crosslinked PA structure and to the intrinsic desalination properties of ZIF-8.

The Kingdom of Saudi Arabia is dependent on desalination of seawater to provide new water supplies for the future. Desalination is expensive and it is very important to reduce the cost and lower the energy consumption. Most seawater reverse osmosis facilities use open-ocean intakes, which require extensive pre-treatment processes to remove particulate and biological materials that cause operating problems. An alternative intake is the subsurface system which utilizes the concept of riverbank filtration using wells or galleries and provides natural filtration to improve the quality of feedwater before it enters the desalination plant. This reduces operating cost and lowers energy consumption. Research was focused on evaluating gallery-type intakes (beach and seabed galleries) that could be used along the Northern Red Sea shoreline to provide a better quality feedwater for desalination. The geological characteristics of the visited sites were favorable for the development of seabed filter systems (offshore), but not for beach gallery intakes. The low wave energy along the shoreline and the presence of mud or rocky coasts made beach galleries infeasible. One of the potentially favorable sites for a seabed filter was located in the nearshore area at King Abdullah Economic City (KAEC). This site has a predominantly sandy offshore bottom with shallow water depths, and a low tide range. In addition, the bottom is always covered with water and contains soft limestone unit below the sand mantle that could be easy excavated to facilitate the construction of a seabed filter. About 50 sediment samples were collected from the site and laboratory measurements were performed on them. Grain size distribution, porosity and hydraulic conductivity measurements were performed on the sediment samples. In addition, six statistical methods were used to estimate the hydraulic conductivity values. Based on results of lab measurements, field observations, tide ranges and sediment types, it is concluded that the geological conditions and characteristics of KAEC site are feasible for design and construction of a seabed filtration system. A conservatively designed cell with dimensions of 100 by 50 m would produce about 25,000 m3/day of filtered seawater and seven cells could support a 60,000 m3/day (permeate) seawater RO plant.

It goes without saying that water scarcity is a widespread and increasingly pressing global challenge. One of the methods which can mitigate water shortage is to increase freshwater production via desalination of saline waters. Seawater and saline aquifer sources represent 97.5% of all water on Earth. Hence, treating even a small portion of saline water could significantly reduce water shortage. Although reverse osmosis is one of the state-of-the-art pressure-driven membrane desalination technologies, it is incapable of desalinating high-salinity streams due to the very high osmotic pressure to overcome. Membrane distillation (MD) is one of the emerging methods, which has attracted much attention for desalinating highly saline brines. MD is a thermally driven process in which only vapor molecules pass through the pores of a microporous hydrophobic membrane. This process, however, has not been fully commercialized due to a number of challenges, including “pore wetting”. Pore wetting refers to the presence of liquid, instead of just water vapor, inside the membrane pores, which may cause a decrease in MD flux and/or deterioration of distillate quality. Herein, a comprehensive review on pore wetting is presented, and then this phenomenon is investigated from four aspects. In the first phase of this project, a theoretical model is presented according to which the pore size distribution of membrane, a parameter affecting pore wetting risk, is estimated by employing only a few experimental data points in accordance with the wet/dry method, reducing the number of data required to be recorded largely. In the next phase, an equation is presented for the estimation of liquid entry pressure (LEP), a membrane parameter closely related to pore wetting, using computational fluid dynamics (CFD) tools and genetic programming (GP) as an intelligent technique. This equation can estimate LEP in closer agreement to experimental values in comparison to the Young-Laplace equation. In the third phase, movement of liquid-gas interface inside the membrane pore is tracked using a well-founded model, and consequently, the pressure and velocity at the interface and the required time for replacement are studied. Finally, in the last phase, a model is developed for pore wetting in vacuum MD, considering heat and mass balances at the vapor-liquid interface. This model assumes that heat only enters the pore inlet and is removed due to liquid vaporization at the vapor-liquid interface, with heat transfer through the pore wall neglected. This model shows that partial pore wetting is possible since the vapor-liquid interface might remain within the pore at the steady-state condition. Further, this model can predict the decrease in temperature from the pore inlet to the vapor-liquid interface, a phenomenon that has been reported in the literature without any proof.

Thermal desalination technology especially, multi-effect distillation MED is of great importance to oil producing countries such as those in the gulf region owing to its efficacy in processing seawater with the minimum pre-treatment of the feed and cheap energy input available from waste heat. One of the main drawback of the current MED processes is the susceptibility of scaling when operate above 70 ºC. This limitation deprives the technology to be energy efficient and reduce its optimal productivity. An optimized pre-treatment of the seawater feed by NF membranes can enhance its efficiency significantly. In this work, the possibility of applying a tailored feed quality using thermodynamic speciation chemistry of the feed water and prediction of the scale propensity based on the Saturation Index of the scale minerals was investigated. Different NF membranes with different properties were used and compared experimentally with each other and theoretically with predictions that are based the saturation index. Moreover, new generation of the polymeric antiscalants promoted by the main manufacturers of the inhibitors industry to control scale formation has been investigated. In addition, as part of planned work for future studies, design and construction of a pilot scale based on NF membrane process was carried out and meant to be a potential extension of this work.

The criticality of desalination plants, which greatly rely on Industrial Control Systems (ICS), has heightened due to the scarcity of clean water. This reliance greatly emphasizes the necessity of securing these systems, alongside implementing a robust risk assessment protocol. To address these challenges and the existing limitations in prevalent risk assessment methodologies, this thesis proposes a risk assessment approach for ICS within desalination facilities. The proposed strategy integrates Bayesian Networks (BNs) and Dynamic Programming (DP). The thesis develops BNs into multilevel Bayesian Networks (MBNs), a form that effectively handles system complexity, aids inference, and dynamically modifies risk profiles. These networks account for the interactions and dynamic behaviors of system components,providing a level of responsiveness often missing in traditional methods. A standout feature of this approach is its consideration of the potential attackers’perspective, often neglected but critical for a comprehensive risk assessment and the development of solid defense strategies. DP supplements this approach by simplifying complex problems and and identifying the most optimal paths for potential attacks. Therefore, this thesis contributes greatly to enhancing the safety of critical infrastructures like water desalination plants, addressing key deficiencies in existing safety precautions.

Las angiospermas marinas son organismos esenciales para los ecosistemas costeros de zonas templadas. Sostienen una amplia diversidad biológica, regulan la dinámica sedimentaria costera y capturan grandes cantidades de carbono atmosférico. Sin embargo, a pesar de los servicios ecosistémicos que proporcionan, se encuentran amenazadas por actividades humanas y, especialmente, por la contaminación marina. Para conservar las praderas de angiospermas marinas es necesario desarrollar herramientas de seguimiento a todos los niveles de organización biológica que permitan detectar el estrés fisiológico para prevenir la regresión de estos valiosos hábitats, o de determinar la magnitud de estos procesos a gran escala. Es por ello que se plantea esta tesis con el objetivo de determinar el grado de afección de los vertidos de salmuera procedente de plantas desaladoras, además de su interacción con otros estresores ambientales, desde la escala molecular (expresión de genes) hasta la poblacional (cobertura de las praderas). Estos análisis podrán permitir la selección de biomarcadores específicos que sirvan como indicadores de alerta temprana de estrés y puedan permitir la toma de medidas de gestión para conservar. Los capítulos 2 y 3 de la tesis mostraron, por un lado, una estabilidad general de las praderas someras de la angiosperma marina Posidonia oceanica en la provincia de Alicante y, por otro, una grave regresión de la pradera en la bahía de la ciudad de Alicante. Esto se debe a la coexistencia de diversos impactos ambientales en esa zona que son responsables de esta pérdida de cobertura (619 hectáreas desde 1984), a pesar de la estabilidad general de estas praderas a mayor escala. De esta forma se puede determinar que los procesos de declive de estos ecosistemas no se produce de forma global y generalizada sino a escala local y, por tanto, las herramientas de gestión deben enfocarse en una menor escala espacial y atendiendo a los estresores específicos de cada zona. En el capítulo 4 se sometió a la angiosperma marina Zostera chilensis (endémica del Pacífico sudamericano) a incrementos de salinidad (+3 y +6 practical salinity units, psu) con sales artificiales para determinar su respuesta y tolerancia a potencial vertido de salmuera. La planta mostró una reducción fotoquímica una producción de peróxido de hidrógeno y una sobreexpresón de genes relativos a la osmorregulación y el estrés oxidativo. La respuesta etabólica fue similar a ambos incrementos de salinidad, pero la mayor producción de peróxido y de enfriamiento no fotoquímico a +6 psu parecen indicar que esta salinidad está por encima del umbral de tolerancia de la planta, y por tanto que podría ser vulnerable a un in. En los capítulos 5, 6 y 7 se aplicaron distintos incrementos de salinidad a P. oceanica (desde +2 hasta +6 psu) con salmuera real de una planta desaladora, tanto en condiciones de laboratorio como de terreno (frente a vertido de una planta desaladora) y midiendo respuestas metabólicas tanto en hojas como en meristemos apicales. La salmuera mostró incrementar ciertos indicadores de estrés comparado con sales artificiales y la producción de peróxido de hidrógeno, la peroxidación de lípidos y la expresión de genes relacionados con el estrés osmótico y oxidativo fueron superiores en condiciones naturales (terreno). Además las respuestas fueron más claras en los meristemos apicales en comparación con las hojas. Todos estos resultados indican que los vertidos de salmuera en interacción con los factores naturales ambientales pueden genera un mayor estrés metabólico y fisiológico, que además se puede medir más claramente en los meritemos que en las hojas. El uso de biomarcadores moleculares y bioquímicos en praderas expuestas a vertidos de salmuera, puede permitir la detección temprana de estrés y la potencial interacción con otros factores ambientales (naturales o antrópicos) que puedan comprometer la fisiología y la supervivencia de la planta. Por tanto estos indicadores tienen el potencial de usarse, en combinación con indicadores fenológicos o poblacionales, en planes de seguimiento para medir el grado de afección de un estresor. En esta tesis se proponen una serie de biomarcadores específicos al estrés generado por la salmuera con el fin de desarrollar medidas de gestión costera específicas a escala local que puedan detectar el impacto ambiental y prevenir la degradación de estos ecosistemas marinos. / Tesis financiada por la convocatoria UAFPU98 del programa propio del Vicerrectorado de Investigación de la Universidad de Alicante.