Sustainable Desalination Research Articles

Leveraging life cycle assessment and simplex lattice design in optimizing fossil fuel blends for sustainable desalination

This study aims to minimize the environmental impacts of thermal seawater desalination by optimizing the required fossil fuel mixture. Life cycle assessment (LCA) is applied to simulate the environmental impacts for each fuel mixture. To prevent mixture designs inherited collinearly from correlating LCA results, fuel mixtures are first sampled prior to conducting LCA and then later optimized using a regression-based methodology to reduce entailed environmental impacts. Setting the functional unit to 1 m3 of desalinated water induces different reference flows of energy requirements depending on the fuels used. Increasing the level of any fuel type within the fuel mixture scenario will cause a decrease in the level of the other fuel type(s) included. An augmented simplex lattice mixture (ASLM) design is applied to indicate correct experimental conditions and to prevent the correlation due to collinearity inherited from the nature of mixture problems. Regression models are formulated to represent life cycle impact assessment (LCIA) results in a closed form suitable for response surface methodology (RSM) optimization. An overall composite sustainability index (CSI) is a single index calculated by aggregating and normalizing corresponding LCIA responses of different units, ranges, and scales using the geometric mean-based method. The results indicate that marine sediment ecotoxicity (MSE) is the category most adversely affected by multistage flash distillation (MSF). On a nationwide scale, the LCA optimized results scored a 17% reduction in associated environmental impacts, which corresponds to a 4.2% reduction in the county’s carbon footprint and a 62% reduction in MSE while incurring a minor retrofitting cost to desalination facilities. High MSE results due to excessive fossil fuel consumption/burning in MSF should gain as much attention as paid toward global warming potential. High MSE entails the risk of having heavy metals entering the food chain. On the other hand, the geometric mean approach is found to be an effective model to aggregate the LCIA results into a single index while avoiding the subjectivity of the value judgment used in LCIA weighting. This approach serves as a unit-free rescaling method that is robust to outliers or large values examined across different LCIA impacts.

Short Review of Multichannel Membrane Capacitive Deionization: Principle, Current Status, and Future Prospect

Capacitive deionization (CDI) has gained a lot of attention as a promising water desalination technology. Among several CDI architectures, multichannel membrane CDI (MC-MCDI) has recently emerged as one of the most innovative systems to enhance the ion removal capacity. The principal feature of MC-MCDI is the independently controllable electrode channels, providing a favorable environment for the electrodes and enhancing the desalination performance. Furthermore, MC-MCDI has been studied in various operational modes, such as concentration gradient, reverse voltage discharging for semi-continuous process, and increase of mass transfer. Furthermore, the system configuration of MC-MCDI has been benchmarked for the extension of the operation voltage and sustainable desalination. Given the increasing interest in MC-MCDI, a comprehensive review is necessary to provide recent research efforts and prospects for further development of MC-MCDI. Therefore, this review actively addresses the major principle and operational features of MC-MCDI along with conventional CDI for a better understanding of the MC-MCDI system. In addition, the innovative applications of MC-MCDI and their notable improvements are also discussed. Finally, this review briefly mentions the major challenges of MC-MCDI as well as proposes future research directions for further development of MC-MCDI as scientific and industrial desalination technologies.

Towards sustainable desalination industry in Arab region: challenges and opportunities

Towards sustainable desalination industry in Arab region: challenges and opportunities

Examining the commercially available hydrophobic membranes in combined desalination and power generation through permeate gap membrane distillation

Developing robust and sustainable desalination processes with minimum energy consumption in integration with renewable energy sources is on high demand in the current climate. Utilizing membrane-based processes for either freshwater production or power generation has appeared as a promising approach in recent years. This research further examines the potential of utilizing a permeate gap membrane distillation (PGMD) system integrated with a sealed air tank to produce combined freshwater and power (CWP) on the laboratory scale. In this study, different commercial hydrophobic membranes with 0.2 to 0.02 μm pore size ranges have been tested and the laminated membranes have been examined in two mounting orientations.The maximum harvested hydraulic pressure and power density by using a pristine 0.1 μm nominal pore size laminated polytetrafluoroethylene (PTFE) membrane facing the active layer to the feed channel (ALF orientation), were measured at approximately 1.8 bar and 0.47 W/m2, respectively under the defined test condition. Mounting the active layer to the permeate side (ALP orientation), the maximum hydraulic pressure and power density recorded at approximately 3.6 bar and 0.42 W/m2, respectively. The experimental data using the 0.02 μm pore size laminated hydrophobic PTFE membrane showed the same pattern. That is, despite producing higher hydraulic pressure with currently available commercial smaller pore size membrane in the ALP orientation, the generated power density has not increased significantly or may have even reduced. Hence, the development of high compressive resistance membranes with high permeability, low surface energy and narrow pore size distribution characteristics, is vital to be able to propose the CWP process using membrane distillation (MD) systems as a competitive and sustainable desalination technology.

Sustainable Desalination by 3:1 Reduced Graphene Oxide/Titanium Dioxide Nanotubes (rGO/TiONTs) Composite via Capacitive Deionization at Different Sodium Chloride Concentrations.

The capability of novel 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite to desalinate using capacitive deionization (CDI) employing highly concentrated NaCl solutions was tested in this study. Parameters such as material wettability, electrosorption capacity, charge efficiency, energy consumption, and charge-discharge retention were tested at different NaCl initial concentrations—100 ppm, 2000 ppm, 15,000 ppm, and 30,000 ppm. The rGO/TiONTs composite showed good material wettability before and after CDI runs with its contact angles equal to 52.11° and 56.07°, respectively. Its two-hour electrosorption capacity during CDI at 30,000 ppm NaCl influent increased 1.34-fold compared to 100 ppm initial NaCl influent with energy consumption constant at 1.11 kWh per kg with NaCl removed. However, the percentage discharge (concentration-independent) at zero-voltage ranged from 4.9–7.27% only after 30 min of desorption. Repeated charge/discharge at different amperes showed that the slowest charging rate of 0.1 A·g−1 had the highest charging time retention at 60% after 100 cycles. Increased concentration likewise increases charging time retention. With this consistent performance of a CDI system utilizing rGO/TiONTs composite, even at 30,000 ppm and 100 cycles, it can be a sustainable alternative desalination technology, especially if a low charging current with reverse voltage discharge is set for a longer operation.

Bio-inspired gas-entrapping membranes (GEMs) derived from common water-wet materials for green desalination

Widespread stress on global water supplies compels the need for low-cost and sustainable desalination processes. In this regard, desalination through membrane distillation (MD) can harness waste-grade heat or renewable energy. So far, the membranes for MD have been exclusively derived from intrinsically water-repellant materials - mostly perfluorocarbons. However, perfluorocarbons are limiting in terms of operational conditions, and they also introduce economic and environmental concerns. The development of perfluorocarbon-free MD membranes would likely address those challenges. Here, we report on the proof-of-concept for biomimetic gas-entrapping membranes (GEMs) for MD derived from silica and poly(methyl methacrylate) (PMMA) that are water-wet materials. We drew inspiration for our GEM design from the cuticles of springtails and hairs of Halobates germanus, both of which exhibit mushroom-shaped (or reentrant) features. Accordingly, our GEMs comprise arrays of microscale cylindrical pores with reentrant inlets and outlets that can robustly entrap air on submersion in water. Our PMMA-GEMs yielded a vapor flux of J≈ 1 L-m−2-h−1 while separating a solution of ∼0.6 M NaCl at 333 K from deionized water at 288 K under a cross-flow configuration. To our knowledge, this is the first-ever demonstration of MD membranes derived from intrinsically water-wet materials, and these findings suggest that the rational design of membranes towards greener and cheaper desalination processes is possible.

Sustainable desalination process selection: Decision support framework under hybrid information

Desalination technology has been recognized as a promising solution for mitigating the pressure caused by water shortage. In order to help the decision-makers to select the most sustainable desalination process/technology, a multi-criteria decision analysis method under hybrid information was proposed for sustainability ranking of alternative desalination processes. The interval AHP (Analytic Hierarchy Process) method was employed to determine the weights of the evaluation, and the TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) under hybrid information was employed to determine the sustainability ranking of the alternative desalination processes. Comparing with the previous studies about desalination process selection, the proposed method can achieve desalination selection based on the decision-making matrix composed by multiple types of data (i.e. crisp numbers, interval numbers and fuzzy numbers). Accordingly, the challenges of uncertainties and the quantification on the soft criteria can be successfully solved. The results based on the developed model can facilitate the decision-makers to select the most sustainability desalination technology with the considerations of economic, environmental. Technological and social pillars simultaneously. Four alternative desalination processes including multi-stage flash system (MSF), low temperature multi-effect distillation (LT-MED), reverse osmosis (RO), and vapor compression distillation (VCD) were studied by the proposed method in this study, and the closeness degree (CD) of LT-MED which represents its integrated sustainability performance is 0.6984, followed by the CDs of MSF (0.5602), VCD (0.5381) and RO (0.4116), respectively. Thus, the sustainability ranking from the best to the worst is LT-MED, MSF, VCD and RO. The results were validated by the sum weighted method, and sensitivity analysis was also carried out. The results reveal that the selection of LT-MED as the most sustainable is robust.

Performance investigation of MEMSYS vacuum membrane distillation system in single effect and multi-effect mode

With increase in fresh water demand and lack of fresh water resources, the current water scarcity can only be solved with seawater desalination. However, due to high dependence of current desalination technologies on fossil fuels, especially in GCC countries where the share of thermal desalination systems is dominating, the environmental sustainability is at risk. Despite high operational and maintenance cost, electricity operated membrane based reverse osmosis (RO) system provides simple configuration with less capital cost. Therefore, for future sustainable desalination, more innovative and energy efficient methods have to be sought out which will not only have the low operational cost of the thermal desalination systems but they can also have simple design and fabrication cost of membrane based systems. Vacuum membrane distillation (VMD) is a thermal distillation technique that works on the vapor pressure across the hydrophobic membrane. With the introduction of heat recovery scheme within the VMD modules in form of the multi-effect VMD operation, a detailed performance analysis of the VMD system is presented in this study under different operating conditions. The performance of system is investigated on components level with comparison between single effect and multi-effect operation.

A Levelized Cost Analysis for Solar-Energy-Powered Sea Water Desalination in The Emirate of Abu Dhabi

The Emirate of Abu Dhabi heavily relies on seawater desalination for its freshwater needs due to limited available resources. This trend is expected to increase further because of the growing population and economic activity, the rapid decline in limited freshwater reserves, and the aggravating effects of climate change. Seawater desalination in Abu Dhabi is currently done through thermal desalination technologies, such as multi-stage flash (MSF) and multi-effect distillation (MED), coupled with thermal power plants, which is known as co-generation. These thermal desalination methods are together responsible for more than 90% of the desalination capacity in the Emirate. Our analysis indicates that these thermal desalination methods are inefficient regarding energy consumption and harmful to the environment due to CO2 emissions and other dangerous byproducts. The rapid decline in the cost of solar Photovoltaic (PV) systems for energy production and reverse osmosis (RO) technology for desalination makes a combination of these two an ideal option for a sustainable desalination future in the Emirate of Abu Dhabi. A levelized cost of water (LCW) study of a solar PV + RO system indicates that Abu Dhabi is well-positioned to utilize this technological combination for cheap and clean desalination in the coming years. Countries in the Sunbelt region with a limited freshwater capacity similar to Abu Dhabi may also consider the proposed system in this study for sustainable desalination.

Development of a multi-criteria decision making approach for sustainable seawater desalination technologies of medium and large-scale plants: a case study for Saudi Arabia’s vision 2030

The process of selecting sustainable desalination technique for a particular application is extremely challenging as the number of available desalination technologies is overwhelmingly high. Every technique stands suitable for many end-user applications such as industrial, community and household activities. However, specific methodologies for selecting the suitable sustainable desalination technology are limited particularly when assessing the requirements of a country composed of many regions with different requirements such as The Kingdom of Saudi Arabia (KSA) which is planned to increase its production from 6.26 to 8.84 million m3 per day (m3/d) from 2017 to 2030. To overcome this issue, this work presents a development and implementation of modified TOPSIS approach, to account for the aggregation effect of the previous selected technology on the next selection of medium and large-scale desalination plants. Total of eighteen independent criteria have been evaluated; six main domains: environment, economy, technical, social, safety and policies and regulations, each has three sub-domain criteria. Parametric study based on actual and projected data of the case study is conducted for different scenarios in order to select the optimum desalination technologies as a function of several variables known to the decision makers such as, production, energy consumption and type of available fuel. The ultimate assessment criterion was the productivity of one barrel of oil equivalent (m3/boe). The study indicated that one barrel of oil equivalent which produces 29 m3 of desalinated water in 2015, shall be capable of producing 86.1 m3 by the end of 2030, through the process of implementation of more advanced desalination technologies.

Molecular dynamics simulations of water desalination through polymerized fullerite membrane

A water-filtering architecture based on nanoporous membranes is proposed for water desalination. In this paper, we show via molecular dynamics simulations, a polymerized fullerite membrane enables an outstanding water permeability with perfect salt ion rejection. Compared to the conventional reverse osmosis and nanoporous graphene, the water permeability is found to be much higher. A collective motion of hoping single-file water through a nanopore, which is tuned through desalination velocity and temperature, is identified and proved to be of great significance in enhancing water permeability. Single-file water with concerted dipole orientation exhibits faster water permeation through nanopores of polymerized fullerite membrane. It is revealed that larger desalination velocity will bring defects to the dipole orientation of single-file water, resulting in water reorientation through nanopores and lower water permeability. The polymerized fullerite membrane is found to suffer from bending deformation at high hydraulic pressure, leading to pore enlargement and degradation of salt rejection. An optimization scheme is provided to ensure a sustainable desalination performance. These insights shed light on polymerized fullerite as a prospective membrane for water purification and provide theoretical guidelines for achieving fast water permeation through collection motion of single-file water.

Sustainable desalination technologies: Avenues for cooperation in the Indo-Pacific

ABSTRACTDesalination technologies using ocean thermal energy are a sustainable method of producing fresh water, especially for ecologically fragile regions and small island nations. India has tested this technology in the Lakshadweep Islands and has the capability to share it with its Indo-Pacific partners. This paper explores the benefits, market and prospects of sustainable desalination technologies in the Indo-Pacific region. It outlines the possible multilateral platforms that can be used to share this technology and the various challenges that this endeavour faces. The paper concludes that such technology sharing will have a positive impact on regional integration and will strengthen India’s position as a responsible regional power promoting the blue economy.

Contactless steam generation and superheating under one sun illumination

Steam generation using solar energy provides the basis for many sustainable desalination, sanitization, and process heating technologies. Recently, interest has arisen for low-cost floating structures that absorb solar radiation and transfer energy to water via thermal conduction, driving evaporation. However, contact between water and the structure leads to fouling and pins the vapour temperature near the boiling point. Here we demonstrate solar-driven evaporation using a structure not in contact with water. The structure absorbs solar radiation and re-radiates infrared photons, which are directly absorbed by the water within a sub-100 μm penetration depth. Due to the physical separation from the water, fouling is entirely avoided. Due to the thermal separation, the structure is no longer pinned at the boiling point, and is used to superheat the generated steam. We generate steam with temperatures up to 133 °C, demonstrating superheated steam in a non-pressurized system under one sun illumination.

Silver Nanomaterial-Immobilized Desalination Systems for Efficient Removal of Radioactive Iodine Species in Water.

Increasing concerns regarding the adverse effects of radioactive iodine waste have inspired the development of a highly efficient and sustainable desalination process for the treatment of radioactive iodine-contaminated water. Because of the high affinity of silver towards iodine species, silver nanoparticles immobilized on a cellulose acetate membrane (Ag-CAM) and biogenic silver nanoparticles containing the radiation-resistant bacterium Deinococcus radiodurans (Ag-DR) were developed and investigated for desalination performance in removing radioactive iodines from water. A simple filtration of radioactive iodine using Ag-CAM under continuous in-flow conditions (approximately 1.5 mL/s) provided an excellent removal efficiency (>99%) as well as iodide anion-selectivity. In the bioremediation study, the radioactive iodine was rapidly captured by Ag-DR in the presence of high concentration of competing anions in a short time. The results from both procedures can be visualized by using single-photon emission computed tomography (SPECT) scanning. This work presents a promising desalination method for the removal of radioactive iodine and a practical application model for remediating radioelement-contaminated waters.

A multi-criteria decision support system to rank sustainable desalination plant location criteria

Due to globally increased demand of drinkable and usable water, countries are focusing more in building desalination plants. Desalination plant location selection is a strategic decision and decision makers need to deal with multiple criteria that are sometimes conflicting in nature. In addition to technical and operational aspects, sustainability (social, environmental, economical) aspect needs to be considered in desalination plant location decision. The purpose of this paper is to develop a multi-criteria decision support system (DSS) to rank desalination plant location criteria in United Arab Emirates (UAE) by considering social, environmental, economical, technical and operational aspects. Result shows that technical (21.9%) and economical (20.9%) are top two main aspects of desalination plant location criteria. Similarly, waste water discharge (22.2%), life species (13.3%), real cost of water and government subsidy (18%), quality and quantity of fresh water (12.4%), and water supply network (9%) are the top ranked sub-criteria of environmental, social, economic, technical, and operational aspects respectively.

Developments in forward osmosis and membrane distillation for desalination of waters

Membrane technology has become a common separation technology over the past decennia. Membranes are used more and more for the production of drinkable water from groundwater, surface water and wastewater. Membranes are now competitive versus conventional techniques. Desalination is predominantly used to eradicate the problem of water scarcity. The sustainability of all desalination processes depends mainly on the reduction of energy costs (production cost) and the increase in water recovery. Forward osmosis and membrane distillation are emerging technologies for sustainable desalination. Here we review membrane processes of forward osmosis and membrane distillation and the advancements in membrane material and modules. We also discuss the capability of membrane distillation in treating highly concentrated aqueous solutions derived from other desalination processes. Furthermore, the advancements in fabrication of high-performance membrane is reviewed and the performance of different membranes and optimization of membrane distillation process are summarized.

Energy Storage & Desalination

In Gulf Cooperation Council (GCC) countries, about 40% of primary energy is consumed for cogeneration based power and desalination plants. In the past, many studies were focused on renewable energies based desalination processes to accommodate 5 fold increase in demand by 2050 but they were not commercialized due to intermittent nature of renewable energy such as solar and wind. We proposed highly efficient energy storage material, Magnesium oxide (MgO), system integrated with innovative hybrid desalination cycle (MEDAD) for future sustainable desalination water supplies. The condensation of Mg(OH)2 dehydration vapor during day operation with concentrated solar energy and exothermic hydration of MgO at night can produce 24 hour thermal energy for desalination cycle without any interruption. It was showed that, Mg(OH)2 dehydration vapor condensation produce 120C and MgO hydration exothermic reaction produce 140C heat during day and night operation respectively correspond to energy storage of 81kJ/mol and 41kJ/mol. In addition, the hybrid MEDAD cycle can boost water production to more than 2 fold as compared to conventional desalination processes at same operating temperature due to excellent thermodynamic synergy. We believe that the proposed energy storage driven desalination cycle is the most sustainable solution for future water supplies.

Desalination network model driven decision support system: A case study of Saudi Arabia

This study aims to develop a network model driven platform that supports decision-makers to make well-informed decisions for the efficient water supplies, taking Saudi Arabia as a case study. The water/energy network analysis should be able to identify optimal locations for sustainable desalination infrastructure investments, accounting for the existing assets and the current investment plans. The geographical aspect of individual resource production and distribution can be quantitatively handled by a graph-theoretic approach. This study employs a new multicommodity network flow model called the INFINIT (interdependent network flows with induced internal transformation) model, which enables to address water-energy nexus issues and to optimize the flow of multiple resources as well as placement of new water/energy facilities at the individual facility level. The INFINIT model in this study formulates and solves mixed-integer linear programming (MILP) problems to minimize the designated multi-objective functions of the total cost and CO2 emission. As a result of optimization, the Pareto-optimal solutions with different network flow topology and the downselected potential locations for new facilities are obtained. To effectively visualize alternative design and policy scenarios, two ways of visualization of the results are developed: a MATLAB-based graphical user interface and tabletop 3D map projection.

Optimized desalination performance of high voltage flow-electrode capacitive deionization by adding carbon black in flow-electrode

Flow-electrode capacitive deionization (FCDI) is a new desalination technology that delivers sustainable desalination performance. However, higher desalination rate and charge efficiency of FCDI are still desired for practical applications. In this study, voltages greater than 1.23V – the minimum voltage for water electrolysis – were applied to enhance the driving force for ion migration and adsorption in an FCDI so as to achieve higher desalination rates. When the voltage was raised from 0.6 to 4.8V, the desalination rate increased by nearly 7 times but the charge efficiency reduced from 92% to 69.5% due to the occurrence of Faradaic reactions such as water electrolysis. The other major factor that influenced the FCDI's charge efficiency was found to be concentration diffusion of ions between the FCDI's middle chamber and the two electrode chambers. To improve the charge efficiency, carbon black (CB) particles with an average diameter of 12μm were added to the activated carbon flow electrodes at a mixing ratio of 1.5wt%. With that, the FCDI's charge efficiency increased from 83.5% to 96.5% at 2.4V. Electrochemical impedance spectrometry (EIS) analysis indicates that the addition of CB particles significantly reduced the FCDI's internal resistance, thereby leading to enhanced desalination performance.

The Pursuits of Ultimate Membrane Technology including Low Pressure Seawater Reverse Osmosis Membrane developed by “Mega-ton Water System” Project

Reverse osmosis (RO) technology has been widely applied to water treatment such as seawater desalination, and large RO plants are many in operation around the world. Moreover, much larger plants will be required to secure sufcient water resource in the near future because global water shortage and quality problems are still getting more serious. Mega-ton Water System project was carried out for sustainable management of water environment and for low-carbon path to develop advanced key technologies of water treatment. Lowpressure RO membrane for seawater desalination has been studied in the project as a part of the core technologies to realize mega plant that is capable of producing 1,000,000 m3 of freshwater per day. Fundamental and scientifc research for RO membranes based on fne structure analyses by means of transmission electron microscopy with a special technique was conducted, and practical tools for designing new innovative RO membrane were acquired by the structure analyses to quantify the physicochemical and chemical properties of RO membranes. As the result of studying on structural design of RO membrane, low pressure SWRO membrane was obtained to reduce energy consumption compared to conventional ones in the past of SWRO. The vision of the “Mega-ton Water System” is sustainable desalination and reclamation. The missions are: 1) energy reduction (20-30%), 2) water production cost reduction (50%), and 3) low environmental impact (fewer chemical operations). Water cycle in “Mega-ton Water System” is separated into two parts including i) Seawater RO (SWRO) system, and ii) Seawater RO system with PRO system. The main challenge of development goal is the construction of mega-ton-scale system for seawater desalination for half the current cost. Accordingly, we developed the world’s frst low-pressure, multi-stage, high yield RO system, using a low-pressure seawater desalination membrane, and as a result of incorporating into it the elemental technologies gained from research in subthemes, such as highly-efcient pressure energy recovery, low-cost and highly durable plastic piping, pretreatment without the use of chemicals.