Large-scale Seawater Desalination Research Articles

Anion-Counterion Strategy toward Organic Cocrystal Engineering for Near-Infrared Photothermal Conversion and Solar-Driven Water Evaporation.

An anion-counterion strategy is proposed to construct organic mono-radical charge-transfer cocrystals for near-infrared photothermal conversion and solar-driven water evaporation. Ionic compounds with halogen anions as the counterions serve as electron donors, providing the necessary electrons for efficient charge transfer with unchanged skeleton atoms and structures as well as the broad red-shifted absorption (200-2000 nm) and unprecedented photothermal conversion efficiency (~90.5 %@808 nm) for the cocrystals. Based on these cocrystals, an excellent solar-driven interfacial water evaporation rate up to 6.1±1.1 kg ⋅ m-2 ⋅ h-1 under 1 sun is recorded due to the comprehensive evaporation effect from the cocrystal loading in polyurethane foams and chimney addition, such performance is superior to the reported results on charge-transfer cocrystals or other materials for solar-driven interfacial evaporation. This prototype exhibits the great potential of cocrystals prepared by the one-step mechanochemistry method in practical large-scale seawater desalination applications.

Feasibility Analysis of Building Large-Scale Seawater Desalination Project in Haiyang, Shandong Province

Feasibility Analysis of Building Large-Scale Seawater Desalination Project in Haiyang, Shandong Province

Bio-inspired selective filtration of sphagnum for efficient solar driven purification of high salinity seawater

Solar-driven interfacial evaporation has emerged as an efficient and sustainable way to generate freshwater from seawater to address the crisis of drinkable water. Though rational designs of photothermal materials and structures are essential to the interfacial solar evaporation process, the salt accumulation remains a challenge to the long-term operation of seawater desalination. Here, we report a high-yield and low-cost natural sphagnum as solar steam generator with ultra-fast water transportation, unique microstructure to prevent salting out, and high evaporation rates. The carbonized sphagnum based photothermal evaporator exhibits a strong broad-band light absorption (>97.0 %). During the solar steam generation, a high evaporation rate of 3.53 kg m−2 h−1 was achieved under 1.0 sun illumination. More significantly, the 3D sphagnum evaporator shows excellent selective filtration of salt ions and cycling stability in actual sea water even high salinity solution (10 wt.% NaCl) for 7 days. This work provides an environmentally friendly and cost-effective photothermal material for large-scale seawater desalination, and treatment of waste water with high ions concentration.

Dynamic modelling and simulation of industrial scale multistage flash desalination process

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.

Rapid Synthesis of Oxygen-Deficient MoO3–x-rGO Composites for Synergistic Photothermal Seawater Desalination and Photocatalytic Sterilization

The development of efficient photothermal desalination devices is of great significance in solving the problem of freshwater shortage. The design and preparation of efficient photothermal materials with a broad light absorption range have been extensively studied. However, the performance of photothermal catalysts for synergistic purification of complex seawater is still facing significant challenges. Therefore, we report the rapid preparation of MoO3–x-rGO composites with synergistic photothermal and photocatalytic performance by the solid-phase microwave thermal shock method. The superhot spots created on the surface of microwave-reduced rGO induce the formation of MoO3–x with oxygen vacancies. Due to the localized surface plasmon resonance (LSPR) effect, the near-infrared photothermal and photocatalytic properties of MoO3–x-rGO catalysts are greatly improved. When the optimal composite catalyst (GMW-3) is illuminated by one sunlight, the seawater evaporation rate and photothermal conversion efficiency can reach 1.58 kg m–2 h–1 and 87.2%, respectively. Meanwhile, the GMW-3 composite evaporator shows excellent antibacterial performance under the synergistic effect of photothermal and photocatalysis during the evaporation process. These findings expand a new insight and platform to design efficient catalysts for large-scale seawater desalination and purification.

Desalination and Transboundary Water Conflict and Cooperation: A Mixed-Method Empirical Approach

The impact of the adoption of desalination on relations between parties in transboundary settings is unclear. The previous literature has indicated that the effect of desalination on conflict and cooperation is an empirical matter. By reducing scarcity and variability, the adoption of desalination is likely to reduce the potential for conflict, though it may also create new conflicts, for instance, over water of marginal quality or over issues of equity. Its effect on cooperation is even more ambiguous, as it both offers parties more flexibility, which is likely to increase cooperation, but can be implemented unilaterally, which may reduce the need for cooperation. The little empirical work that has been published investigating these impacts has been largely based on anecdotal evidence or individual case studies. This paper presents a more systematic look at these impacts, using a mixed-method (quantitative and qualitative) analysis of interstate interactions before and after the adoption of large-scale seawater desalination. The results support the contention that while desalination has the potential to reduce conflict and increase cooperation, the impact of desalination on hydropolitics cannot be assumed a priori. Rather, it is largely context-dependent, and as such, it should not be viewed as a technological fix for transboundary water relations.

Can Large-Scale Offshore Membrane Desalination Cost-Effectively and Ecologically Address Water Scarcity in the Middle East?

The Middle East will face tremendous water scarcity by 2050, which can only be mitigated by large-scale reverse osmosis seawater desalination. However, the coastal land in the region is rare and costly, so outsourcing the desalination facility to artificial islands could become a realistic scenario. This study investigated the ecological and economic challenges and possible advantages of that water supply option by analysing conceptual alternatives for offshore membrane-based desalination plants of up to 600 MCM/y capacity. Key environmental impacts and mitigation strategies were identified, and a detailed economic analysis was conducted to compare the new approach to state-of-the-art. The economic analysis included calculating the cost of water production (WPC) and discussing the differences between offshore alternatives and a conventional onshore desalination plant. In addition, the study investigated the impact of a changing energy mix and potential carbon tax levels on the WPC until 2050. The results indicate that offshore desalination plants have ecological advantages compared to onshore desalination plants. Furthermore, the construction cost for the artificial islands has a much lower effect on the WPC than energy cost. In contrast, the impact of potential carbon tax levels on the WPC is significant. The specific construction cost ranges between 287 $/m2 and 1507 $/m2 depending on the artificial island type and distance to the shoreline, resulting in a WPC between 0.51 $/m3 and 0.59 $/m3. This work is the first to discuss the environmental and economic effects of locating large-scale seawater desalination plants on artificial islands.

Resilience through disasters – The reinstatement and subsequent restart of the Sydney Desalination Plant

Large scale seawater desalination was implemented across Australia by supplying all mainland state capital cities as a result of the millennium drought (1997-2009) in order to diversify and increase the resilience of municipal water supplies. In the state of New South Wales (NSW), construction began on the Sydney Desalination Plant (the Plant) in 2007 and following its completion in 2010 it operated for two years through a process proving period. By 2012 the millennium drought had broken, and the Plant entered a care and maintenance mode (termed Water Security Mode, or WSM) from June 2012. The Plant operates under rules set by the NSW Government through its Metropolitan Water Plan which outlines the primary role as a drought response asset, with provision also to provide emergency response. At around the same time, the NSW Government entered in to a 50-year lease of the Plant to a private company, Sydney Desalination Plant Pty Limited (SDP) in June 2012, that was backed by a 50-year water supply contract with Sydney Water Corporation. The Plant has since been operated by SDP. The NSW Government approach to the resilience of water supply to the greater Sydney region has progressed in recent times, with the 2004 Metropolitan Water Plan undertaking a detailed investigation into the feasibility of not just desalination, but also groundwater and recycled water options to improve system resilience, largely in response to the Millennium Drought. This approach was further reinforced by the 2006 Metropolitan Water Plan, which detailed the progress of planning of a desalination plant in Sydney, and its importance in overall system resilience. The Plant is located in Kurnell, NSW, and has a nameplate capacity of 250 million litres/day (MLD) and the provision for expansion of up to 500 MLD with inlet/outlet seawater tunnels, delivery pipeline and land already sized accordingly.

Temporal reverse osmotic salt filtration mechanism of multi-layered porous graphene

Reverse osmosis (RO) technology is currently the most progressive, energy-saving and efficient membrane separation technology . Meanwhile, graphene becomes a promising candidate for fabricating the RO membranes in water desalination due to its high salt rejection and water flux. The concept of “temporal selectivity” is first proposed in our previous work in terms of the time difference between the penetration time of an ion passing through the pore and the tangential slipping time for the ion sliding across the pore. Nevertheless, the temporal selectivity mechanism of multilayered graphene membrane remains ambiguous. In this paper, the RO process of saltwater through porous graphene column RO membrane is studied by using molecular dynamics (MD) simulations method, and the effects of rotating angular velocity and the thickness of RO membrane on desalination performance of seawater are considered first. The MD results show that the salt rejection increases with the rotation speed of porous membrane increasing while the water flux initially increases and then decreases . Meanwhile, the interfacial slip velocity increases linearly with angular velocity increasing. On the other hand, the increasing thickness of porous graphene membrane can enhance the selectivity and reduce the permeability of water molecules. As expected, the tri-layered porous graphene RO membrane can achieve high salt rejection at low interfacial slip velocity. In order to ensure high selectivity and energy conservation and efficient, the pore structure of the porous graphene RO membrane is optimized. The results show that the optimized nanopores can increase the water flux significantly, whereas the salt rejection is not changed appreciably. It is found that the pore size of the innermost layer membrane near the feed region has the most significant effect on the water flux. The water flux increases sharply with the increase of pore diameter and the salt rejection remains totally higher than 80%. Moreover, the RO membrane with a special Type 3 structure exhibits excellent performance in seawater desalination, specifically, the ultrahigh water flux reaches 20029 L·cm<sup>–2</sup>·d<sup>–1</sup> and the super salt rejection arrives at 94%. The research results further clarify and verify the mechanism of the temporal selectivity in RO process, and improve the water flux under the condition of the same membrane thickness by designing gradient hole. The findings can conduce to the in-depth theoretical understanding of porous graphene-based membranes and designing and developing the large-scale seawater desalination devices and water filtration equipment.

Enabling the use of seawater for hydrogen gas production in water electrolyzers

Hydrogen gas will play an increasingly critical role in developing a carbon-neutral energy infrastructure, but it will need to be produced by water splitting using renewable electricity sources. A recent study by Veroneau and Nocera in Proceedings of the National Academy of Sciences (PNAS) suggests an electrolyzer that produces desalinated water from abundant seawater by using forward osmosis.

Large-scale desalination based on parabolic trough collectors and double-effect absorption heat pumps

This paper focuses on an analysis of the current situation of distillation and reverse osmosis technologies and their relationship with renewable energies, to the extent that there is a strong trend in the use of distillation and reverse osmosis technologies. Large-scale seawater desalination using renewable energy is not developed, so a detailed study of the combination of renewable energy facilities, reverse osmosis, and distillation systems are needed to be effective and competitive compared to the use nonrenewable energy. Solar multiple is a very important parameter in the solar thermal industry. This is in the range of 1.5 – 3 and depends on the relationship between storage and plant power. This parameter is important because it reflects a balance between the cost of the parabolic trough collectors and the total of the solar thermal plant. If the same criterion is followed, with a thermal gap of 100 °C, chosen for the parabolic trough collectors sizing, the solar multiple in the system object of this article, has a value higher than 3. The proposed system employs renewable energies for reducing the downtime of the desalination plants, doing possible that the desalination plants being competitive in sites with poor quality solar radiation.

Risk evaluation of large-scale seawater desalination projects based on an integrated fuzzy comprehensive evaluation and analytic hierarchy process method

Desalination projects play a vital role in the water supply of coastal regions with scarce water resources. The risks associated with desalination projects are worth investigating, especially for large-scale projects. This paper presents the risk identification and evaluation processes of large-scale desalination projects. Two levels of risk indicators are identified and the first-level risks include water intake and outfall risk, processing risk, financial risk and circumstance risk. With the identified risk indicators, an integrated fuzzy comprehensive evaluation (FCE) and analytic hierarchy process (AHP) method is introduced to conduct quantitative risk evaluations for large-scale desalination projects. Twenty experts in desalination-related fields are invited to vote to determine the weighting vectors for the FCE through the AHP. They also participate in deciding the membership matrixes in the FCE for three practical desalination projects. The evaluation results indicate that the overall risks of all the considered projects are at the “Very low” level. Finally, to diminish the potential risks, several instructions and recommendations are suggested that depend on the evaluation outcomes. It is expected that the current risk evaluation research will make remarkable contributions to the risk management and control of large-scale desalination projects and further promote the development of the desalination industry.

An assessment of energy storage options for large-scale PV-RO desalination in the extended Mediterranean region

Seawater desalination is already a largely adopted option to cope with the scarcity of natural water resources, but the increasing concerns about water availability in the future make it even more attractive. Because desalination is a highly energy-demanding process, its coupling with renewable energy sources is an essential step for the sustainable production of desalinated water at large scales. In this work we analyze the potential to deploy large-scale seawater desalination using reverse osmosis (RO) under the hypothesis that all the required energy is provided by photovoltaic (PV) production. A simulation over the extended Mediterranean area shows that securing desalinated water for up to about 200 million people in the region is technically possible using PV only, and the benefits of energy storage in batteries and/or water reservoirs are usually higher than its costs. This suggests that water management policies could consider desalination more broadly and encourage PV-based RO, as a possible win-win and cost-effective strategy to improve water and energy resources security.

Preparation of low-fouling reverse-osmosis membranes on an Al2O3 carrier for desalination exploratory research

The surface of an α-Al2O3 carrier for semi-permeable zeolite membranes was modified with copper via an electroless plating process. Following hydrothermal synthesis, dense and highly organized zeolite membranes were obtained. Membrane thickness was confined to the nanoscale following layer-by-layer self-assembly of polyelectrolytes with opposite charges. This controllable and low-cost preparation method could drastically reduce the cost of fabricating reverse osmosis membranes, which is highly significant for the realization of large-scale seawater desalination through reverse osmosis. Understanding the influences of interactions between various ions and the zeolite pores, inter-crystalline gaps, membrane structure and surface chemical properties, transmembrane pressure, and temperature on the desalination process will help provide a theoretical basis and reference point for the development of reverse osmosis membranes.

Nuclear desalination in Iran, current status and perspectives

Nuclear power can be categorized as a clean energy source for producing electricity and supplying the required energy to a desalination plant, promising less atmospheric emission in comparison to fossil fuels. Considering the fact that fresh water-related issues are acute in many countries of the world, the utilization of desalination technologies seems to be the key solution to these problems. Desalination processes are known to be “energy-intensive”, emphasizing the potential advantages of its integration to a nuclear power plant in mediumto large-scale seawater desalination projects. The demand for electricity and fresh water in Iran compels the country to search for a feasible option. We suggest nuclear desalination as a suitable alternative, in which the recovered heat can be used in thermal desalination systems. In this article, the status of currently operating desalination plants and future developments are described. Several possible schemes for coupling nuclear power plant and fossil fuel-based plants with desalination technologies are suggested and some thermo-economic analysis (based on the specific characteristics of the country) are presented. Results of calculations reveal some advantages of nuclear desalination complex and its competitiveness with other options. It should be noted that the research has been conducted by cooperation of two SPbPU PhD students with Iranian citizenship.

Assembling the water factory: Seawater desalination and the techno-politics of water privatisation in the San Diego–Tijuana metropolitan region

This paper is about the peculiar particularities of the dual trends towards urban water privatization and commodification. It uses as its analytical entry point the extraordinary emergence of large-scale seawater desalination, delivered through public-private partnerships, as an alternative municipal water supply for the San Diego–Tijuana metropolitan region. The paper engages and extends Karen Bakker’s work on water as an ‘uncooperative commodity’. Interrogating the neoliberalization of water through desalination, it is argued, requires reference to the socio-technical relations drawn together under the ‘desalination assemblage’. Such water treatment technologies –and the social relations that flow through them– are, in other words, efficacious in the market-disciplining of water. The paper presents an understanding of privatization and commodification as diffuse, and as unfolding through multiple and contradictory materially heterogeneous relationships. Drawing on both urban political ecology (UPE) and assemblage thinking, the paper calls for a more constructive dialogue between different concepts of socio-material relationality. The empirical case studies of two large seawater desalination plants (one in Southern California, one in Baja California) and the re-configuring relations of public/private water governance associated with these projects, provides a pertinent imperative for greater attention to be paid to contingency and heterogeneity in our understanding of the ecology of capitalism.

Leveraging Sustainable Irrigated Agriculture via Desalination: Evidence from a Macro-Data Case Study in Israel

Israel has been a global frontrunner in (a) irrigation water application efficiency; (b) utilization of non-conventional (recycled and brackish) water supplies containing salts for irrigation; and recently (c) large-scale seawater desalination to provide water. Irrigation with water high in salts in many dry regions has been shown to be non-sustainable, mostly due to contamination of soils, subsoils, and groundwater resulting from the application and leaching of salts. We hypothesized that the move to desalination would reverse prior problematic trends of salinization and provide a path to sustainable irrigated agriculture in Israel and similar environments. To investigate effects of desalination in Israel on the status of salinity trends, we evaluated citrus leaf sodium, chloride, and magnesium in the years since the onset of large-scale national desalination in 2008 and examined fresh produce in the country for sodium and magnesium. We found remarkable reversal of previous trends until 2006, when salinity was found to rise consistently, in the recent data showing decreases of 20, 34, and 30% for Na, Cl, and Mg, respectively. A tendency for Israeli produce to be high in concentrations of salts compared to international standards was also reversed following large-scale desalination. Sodium in Israeli fresh produce is no longer much higher than that expected in equivalent sources in the USA while magnesium is lower in Israel fruits and vegetables compared to USDA standards. We present these results and trends to support the argument that desalination can allow and promote sustainable irrigated agriculture in the world’s dry areas.

Performance test of a sea water multi-stage flash distillation plant: Case study

Multi-Stage-Flash (MSF) Distillation is a large scale sea water desalination plants that are widely used in Gulf area. Most installations of MSF plants are operated in cogeneration with a power plant. Also, MSF plants can be combined with other desalination technologies such as Nano filtration and Reverse osmosis (RO) in new installation. However, the new MSF plants are recommended, where large amounts of cheap or waste energy are available (e.g. conventional power plants). Also, the plant location is playing an important role for economic operation due to cold or hot weather conditions.The present study is applied on the seawater multi-stage flash (MSF) desalination plant that is currently under operation in Al-Khafji operations plant located in Saudi Arabia (KSA). The plant contains 20 evaporator stages at capacity of 600,000 gallon per day (GPD). The presented operating data has been collected during a visit of the plant. Theobjectiveis to presentfieldresults of this MSF plant operation in order to measure and evaluate the performance at 70% and 100% capacity during summer (case-1) and winter (case-2) operation. Then, the plant overall performance indicators are presented to compare between the studied two cases in terms of specific cooling water flowrates and performance ratio. Finally, the seasonal performance variation of the plant is included. The results showed that, for the same plant output, the main cooling water flow rates is decreased from 47.1% to 20.1% for case-1 and case-2 respectively, which in turns directly reduces the pumping power by the same ratio. Consequently, running the large scale thermal desalination MSF plant in cold regions is more economic than hot regions for pumping power energy saving considerations. This is to be considered in future large scale desalination plants.

Modeling of flat-sheet and spiral-wound nanofiltration configurations and its application in seawater nanofiltration

The Donnan Steric Pore Model with dielectric exclusion (DSPM-DE) is implemented over flat-sheet and spiral-wound leaves to develop a comprehensive model for nanofiltration modules. This model allows the user to gain insight into the physics of the nanofiltration process by allowing one to adjust and investigate effects of membrane charge, pore radius, and other membrane characteristics. The study shows how operating conditions such as feed flow rate and pressure affect the recovery ratio and solute rejection across the membrane. A comparison is made between the results for the flat-sheet and spiral-wound configurations. The comparison showed that for the spiral-wound leaf, the maximum values of transmembrane pressure, flux and velocity occur at the feed entrance (near the permeate exit), and the lowest value of these quantities are at the diametrically opposite corner. This is in contrast to the flat-sheet leaf, where all the quantities vary only in the feed flow direction. However it is found that the extent of variation of these quantities along the permeate flow direction in the spiral-wound membrane is negligibly small in most cases. Also, for identical geometries and operating conditions, the flat-sheet and spiral-wound configurations give similar results. Thus the computationally expensive and complex spiral-wound model can be replaced by the flat-sheet model for a variety of purposes. In addition, the model was utilized to predict the performance of a seawater nanofiltration system which has been validated with the data obtained from a large-scale seawater desalination plant, thereby establishing a reliable model for desalination using nanofiltration.

Energy Management and Coordinated Control Strategies of Isolated Micro-Grid with Wind Turbines and Seawater Desalination Devices

The combined operation of large-scale off-grid wind turbines and energy-intensive seawater desalination devices will be one of the directions of the cleaner freshwater producing technology in the future. This paper discussed the operation modes and control strategies of isolated micro-grid with wind power, energy storage and seawater desalination equipments based on load characteristics of seawater desalination devices and operating characteristics of wind power, put forward energy management and coordinated control strategies to enhance the economical efficiency and stability of the system. Finally, a digital-analog simulation platform was build based on PXI+cRIO. The real-time simulations for various operating modes of this isolated micro-grid system verified the feasibility of the proposed strategies.