Saline Water Desalination Research Articles

Implementation of Brackish Groundwater Desalination Using Wind-Generated Electricity: A Case Study of the Energy-Water Nexus in Texas

Growing populations and periodic drought conditions have exacerbated water stress in many areas worldwide. In response, some municipalities have considered desalination of saline water as a freshwater supply. Unfortunately, desalination requires a sizeable energy investment. However, renewable energy technologies can be paired with desalination to mitigate concern over the environmental impacts of increased energy use. At the same time, desalination can be operated in an intermittent way to match the variable availability of renewable resources. Integrating wind power and brackish groundwater desalination generates a high-value product (drinking water) from low-value resources (saline water and wind power without storage). This paper presents a geographically-resolved performance and economic method that estimates the energy requirements and profitability of an integrated wind-powered reverse osmosis facility treating brackish groundwater. It is based on a model that incorporates prevailing natural and market conditions such as average wind speeds, total dissolved solids content, brackish well depth, desalination treatment capacity, capital and operation costs of wind and desalination facilities, brine disposal costs, and electricity and water prices into its calculation. The model is illustrated using conditions in Texas (where there are counties with significant co-location of wind and brackish water resources). Results from this case study indicate that integrating wind turbines and brackish water reverse osmosis (BWRO) systems is economically favorable in a few municipal locations in West Texas.

A lanthanum chelate possessing an open-channel framework with water nanotubes: properties and desalination

A new type of thermally stable chelate {La(H2O)4[La(1,3-pdta)(H2O)]3}n · 12nH2O (1) [1,3-H4pdtaCH2[CH2N(CH2CO2H)2]2] with an open-channel shows significant and unusual solvent transport properties and demonstrates a use for low-pressure desalination, which is constructed by cheap and available lanthanum salt and 1,3-propanediaminetetraacetate. The chelate could be converted reversibly to its trihydrate {La(H2O)4[La(1,3-pdta)(H2O)]3}n · 3nH2O (1a), dehydrated product {La(H2O)4[La(1,3-pdta)(H2O)]3}n (1b) and ethanol adduct {La(H2O)4[La(1,3-pdta)(H2O)]3}n · 3nH2O · 3nEtOH (1c). The latter nano-confined ethanol shows a remarkable downfield shift (Δδ = 6.0 ppm) for the methylene group in the solid 13C NMR spectrum compared with that of the free EtOH. Crystal 1 with a regular hexagonal appearance can be used directly for saline water desalination on a small-scale at an ambient temperature, demonstrating a low energy consumption and environmentally friendly method. This is attributed to the 10.0 Å hydrophobic open-channel containing water nanotubes (WNTs, Φ = 4.2 Å). The nano-confined WNTs can be removed at a low temperature (45 °C).

Desalination of seawater ion complexes by MFI-type zeolite membranes: Temperature and long term stability

Ceramic membranes made from zeolites possess the nanoporous structure required for desalination of saline water including seawater. In this research, an α-Al2O3 supported MFI-type silicalite membrane was synthesised by the direct in-situ crystallisation method via a single hydrothermal treatment in an autoclave under autogenous pressure. Desalination performance of the prepared silicalite membrane was carried out with a seawater solution (0.3wt% TDS (total dissolved solids)) over a long period of around 180 days at a constant pressure of 700kPa at various temperatures. The prepared silicalite membrane achieved a high rejection (>93%) for all major seawater ions including Na+ (except for K+, 83%) at an applied pressure of 700kPa and room temperature (22°C), but showed a continuous decrease in ion rejection when increasing the temperature from 22°C and 90°C. Permeation flux of the zeolite membrane significantly increased with increasing in temperature. Upon closer observation of the major cations, size selective diffusion in the zeolite membrane was observed over the temperatures tested. Larger ions Ca2+ and Mg2+ were less responsive to temperature than smaller ions Na+ and K+. No changes in membrane structure were observed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) after 180 days seawater exposure. However, energy-dispersive X-ray spectroscopy (EDS) mapping on the surface of the membrane revealed a small quantity of tightly bound divalent cations present in the structure, which appear to have penetrated the zeolite, accelerated by temperature. They were suspected to have altered the permstructure, explaining why original high rejections at room temperature were not reversed after heat exposure. The work has shown that zeolite membranes can desalinate seawater, but other unusual effects such as ion selective diffusion as a function of temperature indicate a unique property for desalination membrane materials.

Development of a computer simulation program of feed-and-bleed ion-exchange membrane electrodialysis for saline water desalination

A computer simulation program is developed to predict the desalinating performance of a constant voltage feed-and-bleed electrodialysis process, inputting membrane characteristics, electrodialyzer specifications and electrodialytic conditions. A salt solution is supplied to a one-stage or a two-stage process to produce drinking water. Energy consumption for ion transport and limiting cell voltage in both processes are equivalent. In order to operate the two-stage process effectively, the cell pair number in the first stage should be the same to that in the second stage. Current density in the two-stage process becomes larger than that in the one-stage process because salt concentration in the first stage in the two-stage process is increased. Thus, the cell pair number integrated in the two-stage process is reduced compared to that in the one-stage process for producing the same amount of drinking water. Water recovery of the two-stage process is larger than that in the one-stage process because the cell pair number (thus solution feed to concentrating cells in the two-stage process) is reduced compared to that in the one-stage process.

Preparation, characterization, biological activity, and transport study of polystyrene based calcium–barium phosphate composite membrane

Calcium–barium phosphate (CBP) composite membrane with 25% polystyrene was prepared by co-precipitation method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR), and Thermogravimetric analysis (TGA) were used to characterize the membrane. The membrane was found to be crystalline in nature with consistent arrangement of particles and no indication of visible cracks. The electrical potentials measured across the composite membrane in contact with univalent electrolytes (KCl, NaCl and LiCl), have been found to increase with decrease in concentrations. Thus the membrane was found to be cation-selective. Transport properties of developed membranes may be utilized for the efficient desalination of saline water and more importantly demineralization process. The antibacterial study of this composite membrane shows good results for killing the disease causing bacteria along with waste water treatment.

Economic feasibility evaluation of solar distillation systems based on the equivalent cost of environmental degradation and high-grade energy savings

Solar distillation systems have been found economically feasible in desalination of saline water. It is a simple and cost-effective low-carbon technology. Free of cost, non-polluting, non-exhaustible solar energy is used to produce distilled water inside a solar still. In this article, the usual economic analysis model has been modified by incorporating the factor of equivalent cost of environmental degradation and high-grade energy savings for solar stills. The unit cost of desalination of saline water is estimated to be US$ 0.034/L corresponding to 30.42% energy efficiency of a passive solar still. It decreases to US$ 0.024/L using the modified model. Double-slope passive solar stills desalinate at a lowest cost of US$ 0.007/L. Due to higher capital cost of active solar stills, the unit cost of desalination of saline water is higher even if productivity is more. Effects of variation of energy efficiency, useful life, capital cost, etc. are also studied. The payback periods of the passive solar still are found to be in the range of 1.1 to 7.6 years if the selling price of distilled water decreases from US$ 0.18 to 0.04/L.

A New-Generation Asymmetric Multi-Bore Hollow Fiber Membrane for Sustainable Water Production via Vacuum Membrane Distillation

Due to the growing demand for potable water, the capacities for wastewater reclamation and saline water desalination have been increasing. More concerns are raised on the poor efficiency of removing certain contaminants by the current water purification technologies. Recent studies demonstrated superior separation performance of the vacuum membrane distillation (VMD) technology for the rejection of trace contaminants such as boron, dye, endocrine-disruptive chemical, and chloro-compound. However, the absence of suitable membranes with excellent wetting resistance and high permeation flux has severely hindered the VMD application as an effective water production process. This work presents a new generation multibore hollow fiber (MBF) membrane with excellent mechanical durability developed for VMD. Its micromorphology was uniquely designed with a tight surface and a fully porous matrix to maximize both high wetting resistance and permeation flux. Credit to the multibore configuration, a 65% improvement was obtained on the antiwetting property. Using a synthetic seawater feed, the new membrane with optimized fabrication condition exhibits a high flux and the salt rejection is consistently greater than 99.99%. In addition, a comparison of 7-bore and 6-bore MBF membranes was performed to investigate the optimum geometry design. The newly designed MBF membrane not only demonstrates its suitability for VMD but also makes VMD come true as an efficient process for water production.

Development of a computer simulation program of batch ion-exchange membrane electrodialysis for saline water desalination

A computer simulation program of batch ion-exchange membrane electrodialysis is developed for saline water desalination. For proceeding with the computation, the relationships between the salt concentration in desalting cells, cell voltage and the five electrodialysis parameters are expressed by the equations using the continuous electrodialysis program. A salt solution is supplied to the batch electrodialysis process, and the performance changes with time are computed with an instantaneous open/shut feed operation of a solution taking salt concentration and cell voltage as parameters. A salt solution is supplied to a one-stage and a two-stage batch electrodialysis process and the performance of drinking water production is calculated. From cell pair number and energy consumption, the multi-stage operation is economically disadvantageous compared to the single-stage operation. Limiting current density of an electrodialyzer is expressed by the function including temperature and computed.

Improving water desalination by hydraulically coupling an osmotic microbial fuel cell with a microbial desalination cell

A system consisting of two membrane-based bioelectrochemical reactors was developed to treat artificial wastewater and desalinate saline water. In this system, an osmotic microbial fuel cell (OsMFC) containing a forward-osmosis (FO) membrane was hydraulically coupled with a microbial desalination cell (MDC) that had ion exchange membranes. The coupled system significantly improved desalination efficiency through both dilution (in the OsMFC) and salt removal (in the MDC), and achieved more organic removal than an individual MDC. It was found that the high-power operation mode was more suitable for the OsMFC than the open-circuit mode and the high-current mode, because of good desalination performance (95.9% conductivity reduction in the coupled system) and energy production (0.160kWh/m3 treated saline water). When the active layer of the FO membrane was facing the feed solution, more water flux was obtained than the reversal membrane orientation. The coupled system achieved high reduction of conductivity (>85%) from the salt solution containing 10–50g NaCl/L. The acidified water was more advantageous as a catholyte for the MDC because of the superior desalination performance. These results have collectively demonstrated the feasibility of a membrane-based bioelectrochemical system for simultaneous wastewater treatment and saline water desalination.

Desalination of an industrial saline water with conventional and bipolar membrane electrodialysis

The removal of salts from industrial effluents by sustainable techniques is of great interest to many companies. In this study, an industrial saline water, mainly composed of NaCl and KCl, was treated with conventional electrodialysis (ED) and bipolar membrane electrodialysis (EDBM) on lab-scale. The saline water also contained significant amounts of sulfate and calcium, which may give rise to various types of scaling. A partial desalination (target was a removal of 50% of the chlorides) was easily achieved with both ED and EDBM. By using ED, a concentrate containing circa 2M of chlorides was obtained. The formation of scaling was avoided by using monovalent selective anion- and cation-exchange membranes, which was particularly necessary to avoid CaSO4 scaling. A further improvement was obtained by applying EDBM, which yielded an acid and a base stream with a concentration of around 2M, with a relatively good purity. From the initial lab-scale study it was concluded that both ED and EDBM are technologically feasible to desalinate the saline water. In a second phase, the ED scenario was scaled up in a pilot scale study, which demonstrated that the ED pilot plant was operated in a stable way during a long-term experiment.

Synthetic polymer composite membrane for the desalination of saline water

Development of desalination technologies has been identified as vital to fulfilling future water demand. In this research, composite membrane with polyvinyl alcohol (PVA) as separating layer material while cellulose acetate (CA) and polyethylene glycol (PEG) as supporting layer material were used. In the present research work, the synthesis and characterization of a multilayer PVA/CA/PEG membrane was attempted where membrane performance and applicability were investigated for reverse osmosis desalination of different feed concentrations of groundwater, brackish, highly saline, and also extremely saline water (seawater). Values of both salt rejection and water flux were assessed as a measure of membrane efficiency. In addition to suitable application of the prepared synthetic membranes, the antimicrobial sustainability was also evaluated where prospective function against gram-positive and gram-negative bacteria was depicted. It can be concluded by this work that multilayer PVA/CA/PEG membrane performed excellently for the desalination of groundwater, brackish, highly saline, and also extremely saline water. The flux reduction was reduced significantly when PEG was incorporated in the composite membrane. The importance of structural differences for antimicrobial activity of the prepared membranes has been studied with the use of gram-negative and gram-positive bacteria. Antimicrobial efficiency improves with the use of PEG and membranes with smaller pore sizes.

Opportunities for solar water desalination worldwide: Review

Abstract Water desalination is increasingly becoming a competitive solution for providing drinking-water in many countries around the world. The desalination of saline water has been recognized as one of the most sustainable and new water resource alternative. It plays a crucial role in the socio-economic development for many communities and industrial sectors. Currently there are more than 14,000 desalination plants in operation worldwide producing several billion gallons of water per day. Fifty-seven percent are in the Middle East and Gulf region where large scale conventional heat and power plants are installed. However, since they are operated using fossil fuels, they are becoming expensive to operate and the pollution and greenhouse gas emissions they produce are increasingly recognized as harmful to the environment. Moreover, such plants are not economically viable in remote areas, even in coastal regions where seawater is abundant. Many areas often experience a shortage of fossil fuels and inadequate and unreliable electricity supply. The integration of renewable energy resources in desalination and water purification is becoming more viable as costs of conventional systems increase, commitments to reducing greenhouse gas emissions are implemented and targets for exploiting renewable energy are set. Thus, solar energy could provide a sustainable alternative to drive the desalination plants, especially in countries which lie on the solar belt such as Africa, the Middle East, India, and China. This paper explores the challenges and opportunities of solar water desalination worldwide. It presents an extensive review of water desalination and solar desalination technologies that have been developed in recent years and the state-of-the-art for most important efforts in the field of desalination by using solar energy, including the economic and environmental aspects.

Desalination of saline water with single and combined adsorbents

abstract Due to high expenses of energy, desalination of saline waters by low-cost methods is important. To investigate the ability of five adsorbents (peat, activated carbon, zeolite, anionic resin, and cationic resin) in single and combined forms to remove salinity ions from aqueous solutions, 21 treatments were prepared for a batch experiment. This study was conducted using 1 g of each adsorbent in 50 cc of saline drainage water with total dissolved solids of 13.32 g L−1. The ratios of adsorbents in 1 g of each combined adsorbents were the same. Study results showed that among the single adsorbents, peat and activated carbon with adsorption of 255.5 and 253.7 mg of salinity ions had the highest and lowest adsorption rate, respectively. Zeolite, anionic resin, and cationic resin had the same adsorption rate of salinity ions. Between two and three combined adsorbents, all treatments containing cationic resin had the highest adsorption rate. All adsorbents adsorbed anions about 1.7 times of cations. The main finding of this study was that the highest salinity adsorption occurred in combination of cationic resin with peat, zeolite, activated carbon, and anionic resin. Therefore, application of cationic resin with another adsorbent is much more effective in adsorption of salinity ions as compared to single form or combination of three adsorbents.

Numerical simulation of flashing process in MSF flash chamber

abstract Multistage flash (MSF) technology is widely used in saline water desalination particularly in Middle East and North Africa and Gulf Cooperation Council countries. Enhancement in the thermal performance of this technology in different plant sections and processes including the brine flashing process is still promising. This study addresses the optimal position of jumping plate (weir) location and its number inside the MSF chamber. The optimization exercise has been carried out in terms of maximum flashing vapor production and lower pressure drop using commercial computational fluid dynamics software ANSYS CFX 12.1. The Eulerian–Eulerian (free surface flow) two-phase model was adopted while a k–ϵ model was used a turbulent flow model. The theoretical model was verified by comparing the predicated results with those obtained from the reference case study. The maximum deviation between both results was found to be within 8.3%. Prediction of velocity vectors, phase volume fraction, and temperature pro...

Long term experience in the operation of nanofiltration pretreatment unit for seawater desalination at SWCC SWRO plant

Saline Water Conversion Corporation is the pioneer in developing applications and operation of nanofiltration (NF) pretreatment for seawater desalination which was developed by its research arm, namely, the Saline Water Desalination Research Institute. Initial work on a pilot plant scale, resulted in its application in one of the commercial seawater reverse osmosis (SWRO) plants at Ummlujj currently in operation since September 2000. During this long term of operation of NF–SWRO system, a number of improvements were made on the system operation based on operational experiences as well as research, which ultimately resulted in smooth operation of the same. This long-term operation revealed that it is possible to operate NF at 65% recovery at pH = 6 utilizing only low feed pressure of <25 bar. This led to increase in SWRO production by 42%. Also, no chemical cleaning or membrane replacement was required for SWRO membranes. These achievements make the NF–SWRO process economically attractive and feasible. This paper provides an overview of long-term operation of NF–SWRO plant as well as different research programs which were undertaken and results obtained following the application of the same. Major obstacles in the smooth operation of the NF pretreatment and future direction of improvement and research to be adopted are also addressed.

Theoretical and experimental studies of flux enhancement with roughened surface in direct contact membrane distillation desalination

A new design of direct contact membrane distillation (DCMD) using roughened-surface flow channel for enhancement of heat transfer was proposed for increasing the pure water productivity in saline water desalination. The roughened surface was fabricated using siphonic-blasting with aluminum oxide (Al2O3) sand grains and arc spraying for Ni film coating. Experimental study has demonstrated its feasibility and up to 37% of performance enhancement was obtained for the experimental system. A mathematical model considering heat and mass transfer mechanisms has been developed and incorporated with experimental data for evolving a correlation for a heat transfer coefficient correction factor. The correlation is expressed as relative roughness and can be used for predicting the heat transfer coefficient for roughened-surface channels. Considering the tradeoff between the flux enhancements at the expense of energy consumption, an optimized level of roughness can be determined.

Fabrication of Polyvinyl Alcohol/Cellulose Acetate (PVA/CA/PEG)Antibacterial Membrane for Potential Water Purification Application

In the first part of the present research work, the synthesis and characterization of a multilayer PVA/CA/PEG membrane was attempted. Where membrane performance and applicability was investigated for reverse osmosis (RO) desalination of saline water. For this purposes, various synthetic membranes were prepared and characterized for the desalination process. Reverse osmosis parameters of different multilayer composite membranes were evaluated compared to a reference membrane of a desalination station in Egypt. Values of both salt rejection and water flux were assessed as a measure of membrane efficiency. In the present work, selected samples of CA/PEG and PVA/CA/PEG were engaged as membranes for the reverse osmosis process of different feed concentrations of groundwater, brackish, highly saline and also extremely saline water (sea water). Feed and permeate concentrations were determined by conductivity measurements. In addition, to suitable application of the prepared synthetic membranes, the antimicrobial sustainability was also evaluated where prospective function against gram +ve and gram -ve was depicted.

Ion-exchange membrane electrodialysis program and its application to multi-stage continuous saline water desalination

The first part of this article describes the program of a one-stage continuous electrodialysis process operating at a constant current mode. The full continuous electrodialysis program is developed and explained definitely by arranging equations systematically with the following supplementary steps. For preventing scale formation in concentrating cells, salt solutions supplied to the desalting cells are also fed to the concentrating cells. Influence of temperature to the performance of the electrodialyzer is taken into account. Pressure drop in the electrodialyzer is evaluated by incorporating the functions of hydrodynamic diameters of desalting and concentrating cells and slots. An electric current screening effect of a spacer is determined by the volume ratio of spacer rods in a desalting and concentrating cell.In the second part of this article, saline water is desalinated with the multi-stage electrodialysis program by operating the process at a constant concentration mode. Changing salt concentration of a feeding solution in each stage incrementally, the performances of the electrodialyzer such as; ion and solution flux across a membrane pair; cell voltage; current density; salt concentration in concentrating cells; energy consumption; water recovery; limiting current density; pressure drop in the cells and slots are computed in each stage. Energy consumption, water recovery, pressure drop and membrane area are computed in the total stages to produce drinking water.

Desalination efficiency of a novel bipolar membrane based on functionalized polysulfone

Over the last few years, membrane technology has witnessed significant advances in the fabrication of ion-exchange membranes which have been used in various industrial processes such as desalination of saline water by electrodialysis and recovery of acid and alkali from solutions. In the present paper, we fabricated a functionalized polysulfone based bipolar membrane with PVA as the intermediate layer. The structure and characteristic properties of the membrane was studied by FTIR, 1H NMR, TGA and SEM. The membrane performance was evaluated using lab made bipolar membrane electrodialysis stack. Using sea water at a run time of 480min and 0.05N electrolytes, the process efficiency for the production of acid and alkali were 0.6M and 0.7M respectively for the synthesized membrane as compared with 0.4M and 0.5M respectively for the commercial membrane. The prepared membrane showed a current efficiency and energy consumption of 63% and 0.129kWh, respectively as against 45% and 0.14kWh as observed in the case of the procured membrane. The transport number of co-ions, conductivity of the solution and change in potential with respect to time at constant current density of about 5mA/cm2 were also recorded and compared for both the membranes.

A novel concept of energy reuse from high concentration photovoltaic thermal (HCPVT) system for desalination

This manuscript presents the reuse of waste heat recovered from high concentration photovoltaic thermal (HCPVT) systems for saline and brackish water desalination. The goal of such a photovoltaic thermal system is to achieve a dual output, i.e. co-generation of both electricity and fresh water that is applicable for isolated inland or coastal regions with high solar irradiation. This concept involves; i) waste heat recovery at a temperature of ~75–80°C from a low thermal resistance multi PV chip receiver package, ii) thermal energy storage and iii) desalination with the membrane distillation technique (MD). For optimization of the overall yield, we are using a multi-effect membrane distillation (MEMD) system which reaches a similar efficiency improvement per added effect like a multi-effect distillation (MED) plant. A semi-empirical prediction model was developed to describe the MEMD desalination system under steady state conditions. Experimental investigations were carried out with the MEMD system and the results were compared with the model. The model predicted the experimental data with +/−15% accuracy. In summary, the HCPVT–MEMD desalination concept is able to convert ~85% of the solar irradiation into useful energy, an initiative to produce electricity and potable water with renewable solar energy.