Seawater Desalination Process Research Articles

Study of microbial desalination cell performance with different saline streams: Analysis of current efficiency and freshwater production

Microbial desalination cell (MDC) is a sustainable and energy-self-sufficient technology that simultaneously treats wastewater, produces electric energy, and desalinates water in a single device. The optimal desalination process depends on the potential generated in the system, which is mainly limited by cathode reaction, high external load values used, initial salinity of saline stream, or other conditions such as anolyte buffer concentration. As transport processes (i.e., migration and diffusion) in the device overlap under such conditions, it is difficult to identify the factors that affect desalination performance. Most of the existing MDC studies have used oxygen reduction (at neutral pH) as a cathode reaction limiting the performance. The removal of the cathode reaction limitation could help to clarify the operation of the MDC and identify different transport phenomena and their influence on the performance (current efficiency, freshwater production, and salt removal rate). This study presents a systematic analysis of a laboratory-scale MDC (cross-section 100 cm2, batch mode) behaviour under different initial saline concentrations from slightly brackish water (1.3 g L−1 NaCl) to seawater (40 g L−1 NaCl) without limitation in the desalination process (i.e., using a low value of external resistance and potassium ferricyanide as a liquid catholyte). For each initial salinity, the parameters of wastewater treatment capacity, energy and freshwater production are discussed and compared with the literature. The values of freshwater production between 0.5 and 10.6 L m−2 h−1 for each initial saline concentration in the saline compartment are achieved with optimal current efficiency values (80–100%). Additionally, the influence of anolyte buffer capacity on current density in the MDC system (from 0.8 to 1.2 mA cm−2) is analysed. Furthermore, the behaviour of the system during a seawater desalination process is discussed in terms of treatment capacity and Coulombic efficiency. This study could help understand the performance of these systems in possible natural saline scenarios where MDC technology can be implemented in the future.

Techno-economic assessment of forward osmosis as a pretreatment process for mitigation of scaling in multi-stage flash seawater desalination process

Thermal desalination processes suffer from the formation of scalants on the heat exchangers of the evaporator unit which negatively affect the process efficiency. This study evaluated the technical and economic feasibility of a pilot-scale forward osmosis (FO) process for the pretreatment of seawater to remove scaling ions before the multi-stage flash (MSF) process. A commercial hollow fiber FO membrane module was used in the pilot plant. The FO pilot plant used real seawater as feed solution and real MSF brine as draw solution. A maximum recovery rate of 27.7 % was achieved using a pressure gradient of 1.0 bar with the feed solution flowing through the membrane bore side and the draw solution flowing through the shell side with a temperature of 40 °C for both feed and draw streams. The FO membrane showed high rejection for scaling ions, where the rejection rate was almost 99 %, 96 %, and 92 % for sulfate, calcium, and magnesium, respectively. The specific power consumption of the FO process was about 0.01 kWh/m3. It was found that the water production cost for the FO process was almost 0.48 $/m3. The sensitivity analysis shows that the water production cost is highly sensitive to the water flux, especially at the lower range of water flux and high membrane cost. FO pretreatment provides a promising and economical solution for mitigating the scaling issue in MSF desalination plants.

Life cycle assessment of reverse osmosis for high-salinity seawater desalination process: Potable and industrial water production

Seawater desalination is applied worldwide as a solution to water supply, especially for countries with limited water resources. The industry sector is the primary water user in varying qualities for different purposes. Desalination of seawater is increasingly implemented in the Persian Gulf region, but the environmental impacts have not been adequately assessed. This study assessed the life cycle environmental impacts of potable and industrial grade water with the most detailed inventory, including the impact of the brine rejected to the sea and solid wastes using SimaPro software. The 18 ReCiPe midpoint H impact categories, three endpoint damage categories, and the single score have also been specified. The seawater reverse osmosis powered by fossil fuels was studied to produce potable and industrial water. Electricity has the highest contribution to most of the studied impact categories. The sensitivity analysis showed that a 10% decrease in electricity consumption could reduce fossil resource scarcity and global warming by about 5% for potable and industrial water. The single total score for Sea water reverse osmosis (SWRO) potable and industrial water production are 98.83 and 168.54 mPt, respectively, mainly related to the human health damage category. The cumulative energy demand assessment showed that non-renewable biomass and renewable (wind, solar and geothermal) have the least energy intensity, respectively. To the best of our knowledge, the life cycle assessment of SWRO industrial water production has not been performed before. The current study would be a baseline for further comparisons. The potable water production results agree with the other studies despite having a much more detailed inventory.

Structural design of the electrospun nanofibrous membrane for membrane distillation application: a review.

Although membrane distillation (MD) is a promising technology for water desalination and industrial wastewater treatment, the MD process is not widely applied in the global water industry due to the lack of a suitable membrane for the MD process. The design and appropriate manufacture are the most important factors for MD membrane optimization. The well-designed porous structure, superhydrophobic surface, and pore-wetting prevention of the membrane are vital properties of the MD membrane. Nowadays, electrospinning that is capable of manufacturing membranes with superhydrophobic or omni phobic properties is considered a promising technology. Electrospun nanofibrous membranes (ENMs) possess the characteristics of cylindrical morphology, re-entrant structure, and easy-shaping for a specific purpose, benefiting the membrane design and modification. Based on that, this review investigates the current state and future progress of the superhydrophobic, multi-layer, and omniphobic ENMs manufactured with various structural designs for seawater desalination and wastewater purification. We expect that this paper will provide some recommendations and guidance for further fabrication research and the configuration design of ENMs in the MD process for seawater desalination and wastewater purification.

Using Seawater Reverse Osmosis (SWRO) Technology in Seawater Desalination Processes

Water is one of the basic needs for human life, including for people living on the coast. It is difficult to get clean water for consumption because most coastal areas are affected by sea conditions that have high salinity. In order to be consumed, the saline water must be desalinated. Desalination is a process to convert saline water into fresh water. One such desalination technology is using reverse osmosis (RO). The purpose of this study was to determine the process of desalination of seawater into freshwater using the seawater reverse osmosis (SWRO) method. The method used in this research is observation, which is to see directly the stages of the desalination process of seawater into fresh water. The data was obtained in the form of primary data from observations and secondary data from the literature to support primary data. Analysis of the data used in the form of descriptive analysis by describing each stage carried out in the SWRO process. The results showed that the seawater desalination process using SWRO technology had 14 stages. These stages include; intake, raw water pump, raw water reservoir, UF feed pump, Automatic screen, ultrafiltration, UF water reservoir, RO feed pump, HPP & booster, RO membrane, RO water reservoir, permeate pump, chlorine analyzer, product water. In developed and developing countries, SWRO units have been widely used, because by processing seawater into freshwater, there are many benefits for the life cycle and it is environmentally friendly. It also maintains underground fresh water so that it can provide plant life, and trees that provide us with clean oxygen for our lives.

Deep reinforcement learning based coastal seawater desalination via a pitching paddle wave energy converter

Wave energy has the potential to become a significant contributor to the future seawater desalination thanks to its high-power density. However, the intermittent characteristics of wave energy are the main issues to be overcome in the seawater desalination process. In this paper, a spiral wave energy converter (WEC) powered desalination system is proposed by utilizing a bottom flanged pitching spiral pump based WEC to directly convert the pressurized seawater into freshwater. The dynamic model of the spiral WEC powered desalination system is established. In order to mitigate the uncertainties and fluctuations in the fresh water supply, a deep reinforcement learning (DRL) control of the WEC is also designed for smoothing freshwater production, and a prioritized experience replay mechanism is employed for improving training efficiency. The test results indicate that the freshwater flowrate can be maintained at the desired value of 1200 m3/day by using the trained DRL control and the DRL training process converges to the stable value of around −18.

Biofouling of reverse osmosis membranes: assessment by surface-enhanced Raman spectroscopy and microscopic imaging

The decline in the performance of spiral-wound reverse osmosis (SWRO) membranes is frequently due to biofouling. This study focus on qualitative and quantitative diagnosis of SWRO membrane biofouling. Bacterial counts on the different surfaces of the fouled membranes were carried out. Surface enhanced Raman spectroscopy (SERS) was performed to highlight clogging materials as well as their natures and identity. The topography of the fouled membranes and the structures of biofilms were visualized by fluorescence microscopy (FM) and scanning electron microscopy (SEM). The results indicated the presence of bacteria in the different SWRO membrane areas. Those strongly adhered were significantly higher than those weakly. It varied between 26 × 105 and 262 × 105 CFU m−2. However, SERS mapping showed different fouling levels and the thickness of the fouling layer was 5 µm. Microscopic imaging revealed biotic and abiotic deposits. These data can together allow better management of the seawater desalination process.

Evaluation of Solar Energy Powered Seawater Desalination Processes: A Review

Solar energy, amongst all renewable energies, has attracted inexhaustible attention all over the world as a supplier of sustainable energy. The energy requirement of major seawater desalination processes such as multistage flash (MSF), multi-effect distillation (MED) and reverse osmosis (RO) are fulfilled by burning fossil fuels, which impact the environment significantly due to the emission of greenhouse gases. The integration of solar energy systems into seawater desalination processes is an attractive and alternative solution to fossil fuels. This study aims to (i) assess the progress of solar energy systems including concentrated solar power (CSP) and photovoltaic (PV) to power both thermal and membrane seawater desalination processes including MSF, MED, and RO and (ii) evaluate the economic considerations and associated challenges with recommendations for further improvements. Thus, several studies on a different combination of seawater desalination processes of solar energy systems are reviewed and analysed concerning specific energy consumption and freshwater production cost. It is observed that although solar energy systems have the potential of reducing carbon footprint significantly, the cost of water production still favours the use of fossil fuels. Further research and development on solar energy systems are required to make their use in desalination economically viable. Alternatively, the carbon tax on the use of fossil fuels may persuade desalination industries to adopt renewable energy such as solar.

Thermo-economic assessment of forward osmosis as pretreatment to boost the performance and sustainability of multi-effect distillation for seawater desalination

This work presents the thermodynamic and techno-economic assessment of a forward osmosis – multi-effect distillation (FO-MED) system able to improve the thermal performance of the MED seawater desalination process and reduce its environmental impact. Energy, exergy and techno-economic analyses have been carried out to identify the best boundary conditions that enhance the process efficiency and water cost, predicting the scale formation with the Ryznar index. Results show that using FO pretreatment in a 100 m3/d MED plant of 8 effects at 65 °C allows increasing the heating steam temperature up to 100 °C and the number of effects to 16 without increasing the risk of scaling. This results in 44 % reduction of the specific thermal energy consumption and 21 % decrease in the specific heat transfer area. The volume of saline water rejected to the sea is reduced 40 % and the water footprint 36 %. The exergy analysis reveals that the MED is the component with the highest exergy destruction. Finally, the levelized cost of water of the FO-MED is higher (7.6 $/m3) than the standalone MED process (4.6 $/m3). If high-performing and cost-effective membranes are used, the product cost could be reduced 33 % (5.1 $/m3).

Gas/liquid two-phase flow with perforated hollow filament spacer to enhance the filtration performance in spiral wound membrane module

In brackish water and seawater desalination process, flat sheet and spiral wound membrane modules are commonly used to remove particulate pollutants and/or inorganic ions. In these membrane modules, feed spacer is used to construct the flow channel, enhance the flow field and corresponding filtration performance. However, two negative effects also occur for the spacer. One is the high pressure drop due to flow around the filament. The other is the stagnant zone near the filament, which results in localized fouling. In this paper, a new perforated hollow filament spacer was proposed. Gas/liquid two-phase flow was used to mitigate the membrane fouling. Filtration experiments were performed by microfiltration of SiC suspension. Results showed that compared with conventional spacer, the hollow filament spacer can improve the steady permeate flux by 56 %, with lower pressure drop. Particle deposition on membrane surface was effectively retarded, without localized fouling observed. Gas/liquid Flow patterns in the membrane channel were studied with high-speed photography. With the increase of Gas/liquid ratio, the flow pattern changes from bubble flow, slug flow to churn flow. The best filtration improvement performance was obtained with slug flow pattern. This hollow filament spacer is expected to mitigate the membrane fouling and improve permeate flux in the membrane-based desalination process.

Energy-efficient electrolytic H2 production and high-value added H2-acid-base co-electrosynthesis modes enabled by a Ni2P catalyst in a diaphragm cell

Reducing the energy consumption and increasing the additional value of water electrolysis to produce H2 is currently a hot research topic. In this work, we introduce two kinds of promising water electrolysis modes in a diaphragm electrolytic cell for H2 production. When considering the energy consumption, a urea-assisted amphoteric water splitting system was built. This system just needs an ultralow voltage of 0.88 V to attain the current density of 10 mA cm−2 with high durability, which leads to a large decrease of energy consumption of 48.55% compared to alkaline water splitting system by the introduction of electrochemical neutralization energy and thermodynamically-favorable urea oxidation reaction. When considering the additional value, a H2-acid-base co-electrosynthesis system was proposed inspired by the chlor-alkali and electrochemical seawater desalination processes. In this system, only K2SO4 electrolytes are needed, and acid-base chemicals and H2 could be generated at a voltage of 2.32 V (10 mA cm−2).

Energy and environmental performance of a new solar boiler with heat recovery for seawater desalination

This study proposes a new seawater desalination process using concentrated solar energy. Compared with conventional desalination technologies, the proposed process produces tap water with high energy efficiency and a lower environmental impact. The proposed process is based on a new type of solar boiler using solar energy concentrated via a “beam-down” optical system. To improve the productivity, the steam produced is used to feed an adapted multiple-effect distillation (MED) system. A complete process model from seawater and sun to tap water is proposed, coupling an in-house Python program for the solar boiler component and ProSim software for the MED component. Ancillary calculations concerning the pretreatment, post-treatment, and sizing of the components are performed using a spreadsheet program. The environmental impacts of the tap water production by the proposed system are evaluated using the life cycle assessment method. The theoretical feasibility of the proposed process is demonstrated by modeling a reference case, with an estimated annual productivity of 10,000 m3 of tap water. According to the calculation, the energy performance is estimated at 1.57 kWh of electricity and 117.7 kWh of solar energy per cubic meter of tap water produced. An estimated land area of 3845 m2 is required for the solar field. The life cycle assessment indicates that the performance of the proposed process is significantly improved compared with conventional MED, with an 84% reduction in the total impact according to the ReCiPe endpoint method. In addition, the proposed system displays a competitive environmental performance compared with reverse osmosis. The emissions of the new process are estimated at 2.36 kg CO2-eq per cubic meter of tap water produced versus 3.67 kg CO2-eq and 2.97 kg CO2-eq for low- and high-performance reverse osmosis, respectively.

Comprehensive simulation to uncover the ideal properties of a hollow fiber forward osmosis membrane module for the seawater desalination process

Desalination with forward osmosis (FO) membranes is an attractive method, achieving an efficiency superior to that of reverse osmosis (RO), which has been improved for many decades, is difficult. Although many FO membranes have been developed, there are no guidelines in membrane development to make FO highly efficient. This paper quantitatively investigates whether FO desalination can be potentially superior to RO desalination, and, where so, we uncover the range of required membrane properties. The results show that it is difficult for the FO method with current hollow fiber modules to exhibit process performance superior to that of the present RO method with spiral-type membranes. However, if the water permeability of such membranes can be increased threefold, then the energy consumption of FO desalination can be reduced to 70 % of that of RO desalination. Thus, this study proposes guidelines regarding membrane properties, such as support layer thickness, water permeability, and rejection performance, which will be required when FO membranes are further advanced in the future.

PERFORMA DESALINASI AIR LAUT TENAGA SURYA TIPE WICK METODE KAPILER

How to get clean water using the seawater desalination process into pure water in coastal communities. Basin is a sea water desalination tool in the form of a tub or bowl to hold sea water. The basin used in this study was shaped like a tub using a cover made of glass with a thickness of 0.003 m, a slope of 25o and consisted of two types of basins in which one consisted of three levels and the other two levels. From the test results with the variation of the cover glass distance and level variations in the basin showed that the productivity of pure water at the distance of the glass cover 0.105 m basin three levels more is 416 ml while at the distance of the glass cover 0.11 m the productivity of pure water in the basin was two levels more which is 450 ml. The most pure water productivity found in the distance of 0.11 m cover glass, either a three-level basin or a two-level basin with a total pure water productivity of 667 ml. Whereas in the variation in the number of levels in the basin, pure water productivity found in the two-level basin, 450 ml with a desalination efficiency of 26.07%.

Ultraviolet light-activated peroxymonosulfate (UV/PMS) system for humic acid mineralization: Effects of ionic matrix and feasible application in seawater reverse osmosis desalination

The use of membrane-based technology has evolved into an important strategy for supplying freshwater from seawater and wastewater to overcome the problems of water scarcity around the world. However, the presence of natural organic matter (NOM), including humic substances affects the performance of the process. Here, we present a systematic report on the mineralization of humic acid (HA), as a model for NOM, in high concentration of salts using the ultraviolet light-activated peroxymonosulfate (UV/PMS) system as a potential alternative for HA elimination during membrane-based seawater desalination and water treatment processes. Effects of various parameters such as PMS concentration, solution type, pH, anions, and anion-cation matrix on HA mineralization were assessed. The results show that 100%, 78% and 58% of HA (2 mg/L TOC) were mineralized with rate constants of 0.085 min−1, 0.0073 min−1, and 0.0041 min−1 after 180 min reaction time at pH 7 when 0.5 mM PMS was used in deionized water, sodium chloride solution (35,000 ppm) and synthetic seawater, respectively. The reduced efficiency under saline conditions was attributed to the presence of anions in the system that acted as sulfate and hydroxyl radicals’ scavengers. Furthermore, the safety of the treated synthetic seawater was evaluated by analyzing the residual transformed products. Overall, pretreatment with the UV/PMS system mitigated fouling on the RO membrane.

Analisis Pengaruh Variasi Massa Material Arang Terhadap Proses Desalinasi Air Laut Tenaga Surya

Desalination is the process of distilling seawater using a heat source from solar energy to obtain fresh water. Therefore, one of the methods used to increase the results of the seawater desalination process is to make a tool using solar energy and charcoal material. This research was conducted to determine the effect of using charcoal material on the seawater desalination process. The use of charcoal material is expected to increase the absorption of heat energy and accelerate the evaporation process of seawater. In this study, the highest efficiency was obtained in basin I with a mass of 500 grams of charcoal, namely 5.393% with 70 ml of water produced, followed by basin IV without using charcoal material with an efficiency of 6.116% with fresh water produced of 60 ml, followed by basin IV. II with a mass of 400 grams of charcoal obtained an efficiency of 1.585% with 59 ml of water produced. And in basin III the efficiency and fresh water produced is less, namely 0.004% and the water produced is 41 ml

Flexible MXene-based Janus porous fibrous membranes for sustainable solar-driven desalination and emulsions separation

Sustainable solar energy driven seawater desalination technology is currently deemed as a promising pathway to overcome the shortage of freshwater resources, but solar water evaporation material suffers from serious salt-fouling, low freshwater yield, and poor long-term performance in seawater. Herein, a Janus photothermal porous fibrous membrane, composed of hydrophobic MXene/Poly(dimethylsiloxane) coatings and a hydrophilic polylactic acid/TiO2 nanofluids porous fibrous membrane, was prepared. During the solar-driven seawater desalination process, the hydrophilic fibrous membrane, functioned as salt-rejection barrier, induced by TiO2 nanofluids and transport seawater to the surface through its microporous channels; the MXene/PDMS coatings acted as a photothermal layer and generated localized heat at the water-vapor interface upon light irradiation. The solar-thermal test results show that, the Janus porous fibrous membrane displays stable solar-thermal conversion efficiency of 60%, freshwater yield of 1 kg m-2 h-1 and low ion concentration (≤1 ppm) under 1 sun irradiation in direct contact mode, which is superior to other literatures reported. With synergistic effect of TiO2 nanofluids and MXene, the Janus fibrous membrane exhibits a high salt rejection rate of 99.95%, and antibacterial activity as high as of 100%. Notably, benefiting from opposite wettability of Janus porous fibrous membrane, the as-prepared membranes also display excellent separation flux and high separation accuracy (>99.95%) in various surfactant-stabilized oil/water emulsions. It is anticipated that this versatility of Janus porous fibrous membrane has excellent photothermal conversion capability and separation properties, making it have great application potential in using sustainable solar energy to collect freshwater from seawater, medical service wastewater and other application in environmental protection.

Effects of the soaking-related parameters in a combined freezing-based seawater desalination process.

A combined freezing, soaking, and centrifugal desalination (FSCD) process was employed to desalt seawater taken from Bohai Bay. The seawater was frozen into two kinds of sea water ice having different texture and size using either commercial refrigerator or experimental setup. For both kinds of ice samples, the influences of soaking-related parameters on the desalination effect were studied. For most ice samples treated with FSCD process, the salt removal efficiencies are higher than 90%. The purity of ice product increases as increasing soaking time and at higher initial soaking liquid temperature, while the ice yield rate decreases. At the same ice yield rate, the salt removal efficiency for ice flakes is higher than that for crushed ice samples, whereas when the raw seawater of 27°C is used as soaking liquid, FSCD process is not feasible due to too lower ice yield rate.

Surface-engineered sulfonation of ion-selective nanofiltration membrane with robust scaling resistance for seawater desalination

Inorganic fouling is one of the most critical issues in the seawater desalination process; it significantly deteriorates the desalination performance of the current seawater reverse osmosis (SWRO) membranes. Conventional nanofiltration (NF) membranes, which act as the pretreatment medium, are unable to effectively fractionate the scaling ions, Ca 2+ and SO 4 2− , resulting in fouling transfer from SWRO to the NF membranes. To address this issue, a new class of nanofiltration membranes was proposed and designed by surface engineering a custom-made sulfonated polyamide thin-film composite. Specifically, a new functional monomer, 4-aminobenzenesulfonic acid (ABSA), was chemically grafted onto a membrane surface via carbodiimide crosslinking chemistry. Due to the intentional optimization of mean pore sizes and surface charges, the as-prepared NF membranes (named BM-ABSA) exhibited extremely low Ca 2+ rejections (6.1 ± 0.4%) and moderate SO 4 2− rejections (57.5 ± 0.1%), corresponding to a higher ion selectivity (9.5) toward seawater compared to that of the benchmark commercial NF270 membrane (1.5). More importantly, the replacement of carboxylate groups in the substrate membrane matrix with the sulfonate groups considerably lowered the probability of the Ca–COOH chelation effect, which, in turn, facilitated steady NF-pretreatment processes without significant fouling. The subsequent SWRO process, using the BM-ABSA membrane-pretreated permeate as the feed solution, also proceeded well over a short-term operation with limited gypsum fouling. Overall, this study highlighted the effective inhibition of scaling by sulfonated NF membranes in the pretreatment process, validating their potential application for robust and efficient seawater desalination. • ABSA was chemically grafted onto the surface of NF membrane through EDC/NHS coupling reaction. • BM-ABSA-5 membrane showed a high ion-ion selectivity toward Ca 2+ and SO 4 2− . • The anti-scaling mechanism of –SO 3 H groups was investigated by molecular dynamics simulation. • Gypsum scaling on NF membrane and RO membrane was both inhibited in the hybrid NF-RO process for seawater desalination.

A Novel Ocean Thermal Energy Driven System for Sustainable Power and Fresh Water Supply.

The ocean thermal energy conversion (OTEC) is a potential substitute for traditional power plants in tropical islands and coastal regions. However, the OTEC power generation cycle has low thermal efficiency and the integrated utilization is imperative, in which an OTEC coupled with seawater desalination is the most attractive option. Membrane distillation (MD) has distinct advantages making itself a competitive process for seawater desalination, especially the feature that the drained warm seawater from the OTEC power plant can be recycled, improving the integrated output of the OTEC system. In this study, an innovative OTEC system coupling a power generation sub-cycle (PGC) and a water production sub-cycle (WPC) was proposed, composed of the upstream organic Rankine cycle and the downstream membrane distillation modules. The mass, energy and exergy balance of the individual equipment, the sub-cycles and the whole system were performed by constructing the corresponding balance models. The thermal dynamic parameters were calculated, and the performance of power generation and water production was predicted. The results showed that by coupling with the MD desalination, the thermal efficiency of the OTEC system can be greatly improved from 2.19% to 25.38% while the exergy efficiency changed little. For a 100 kW OTEC power generation cycle, the water production rate approached 58.874 t/d. In addition, the economic analysis based on the electricity and water sale was carried out, and the profit can be improved by extra water production, especially in the Hawaii and Rainbow Beach by nearly 20%.