Development Of Desalination Technologies Research Articles

Neural networks for predicting air gap membrane distillation performance

The hollow fiber air gap membrane distillation (AGMD) has recently attracted tremendous attention for desalination and wastewater treatment due to its high packing density, low conductive heat loss, and latent heat recovery capability. Utilizing fast and accurate modeling tools to predict MD performance can result in the further development of desalination technologies. However, simple and time-saving prediction models to assess the AGMD performance were not abundant. Herein, AGMD performance, including permeate flux (J) and gained output ratio (GOR) was predicted through multiple linear regression (MLR) model, back propagation neural network (BP ANN) and radial basis function neural network (RBF ANN) under different hot temperatures (Th), coolant temperatures (Tc), feed flow rates (F), and feed concentration (c). A total of 30 sets of data were used to train the proposed models, the other 10 external validation datasets not used for training the models were applied to validate the prediction accuracy. The results depicted that RBF ANN (SPREAD = 30, N = 30) showed greatest prediction performance (R2 = 0.99–1) compared with BP ANN and MLR models (R2 = 0.98–0.99; R2 = 0.89–0.97). The computing time consumption of RBF ANN was higher than BP ANN. According to the Mean impact value (MIV) analysis, Th had the strongest effect on J and GOR. Increasing Th and decreasing c both had positive impacts on J and GOR, but increasing Tc or F resulted in a trade-off influence. A genetic algorithm (GA) was employed to optimize J and GOR simultaneously, the optimum J and GOR could reach 6.00 kg/m2·h and 7.70 respectively. In this study, the three prediction models proved their abilities to predict AGMD performance and further provide guidance in the actual membrane distillation water treatment process.

Synthesis and application of NiO-ZrO2@g-C3N4 nanocomposite for high-performance hybrid capacitive deionisation

The desalination of saline water from the ocean and estuaries provides about 65 % of the global freshwater supply. Desalination technology development is dependent on a reliable and cost-effective electrode material. This research is focused on the synthesis and application of NiO-ZrO2@g-C3N4 nanocomposite for the desalination of saline water by the hybrid capacitive method. NiO-ZrO2@g-C3N4 was synthesized by a solid-state reaction. It was then used to modify the activated carbon electrode. This was applied as an electrode in a CDI cell for the desalination of saline water. The highest ion adsorption capacity recorded is 24.45 mg/g at 1.2 V applied voltage and an electrolyte concentration of 800 mg/L, while the optimum salt recovery efficiency was recorded at 42.7 % with the 300mb/L solution. The specific capacitance of the NiO-ZrO2@g-C3N4 composite is 550F/g at a scan rate of 10 mV/s in a 1.0 M KCl solution, and that of g-C3N4 is 300F/g at a scan rate of 10 mV/s, in a 1.0 M KCl solution. The NiO-ZrO2@g-C3N4 composite also displayed excellent electrochemical stability after nine cycles of adsorption/desorption measurements. The result implies that NiO-ZrO2@g-C3N4 is an ideal electrode material for application in desalination by the hybrid capacitive deionisation method.

Long side-chain type partially cross-linked poly(vinylidene fluoride-co-hexafluoropropylene) anion exchange membranes for desalination via electrodialysis

Surplus demand for freshwater gained considerable attention towards the development of desalination technologies, of those electrodialysis proved to be able to brackish water desalination. Herein, this article clearly explains the synthesis of poly(vinylidene fluoride-co-hexafluoropropylene) based anion exchange membranes (AEMs) for electrodialysis. Prepared series of AEMs is analyzed for stabilities and ion transport behavior to assess their suitability in electrodialysis. TEM and AFM imaging are used to get further insights about hydrophilic-hydrophobic phase separation and ionic domain clustering, which is critical for the amplification in electrochemical properties. Optimized membrane (AEM-1.0) exhibited notable electrochemical properties with water uptake of 44.3%, ion exchange capacity of 1.56 meq g−1, and ionic conductivity of 21.1 mS cm−1. Relatively high transport number (0.94) and limiting current density (43.7 A m−2) of AEM-1.0 membrane enables a broad window for faster electrodialytic desalination at a higher operating potential. Further, 1.05 kWh kg−1 energy consumption and 87.33% energy efficiency are realized for optimized AEM-1.0 membranes, which proves its efficiency to be employed in electrodialysis for brackish water desalination.

State-of-the-art of R&D on seawater desalination technology

Fresh water deficit has been an increasingly critical global environmental issue, and seawater desalination is considered as the most effective and promising solution, which promotes the development of different desalination technologies. In order to provide a comprehensive knowledge about the development of desalination technologies, state-of-the-art of research and development on the application of desalination technologies is reviewed in this paper. At first, the overview of desalination technologies is briefly introduced, including the definition of desalination, the evaluation index of water quality and the resulting classification of water resources, the overview of desalination industry, the usages of freshwater produced by desalination, and the sources of raw water. Besides, conventional desalination methods are categorized into physical method and chemical method according to whether there is new substance generated in the desalination process. In the following section conventional desalination methods are reviewed from the perspectives of basic processes and principles, the performances and technical characteristics. However, the shortcomings of conventional desalination technologies mainly lie in high energy consumption and complex treatment process, such as the decrease of heat transfer coefficient caused by the scaling and fouling generated on the solid heat transfer walls for multi-stage flash (MSF) and multiple effect distillation (MED), and rigorous pre-treatment and low recovery factor for reverse osmosis (RO). With the aims of overcoming these disadvantages and thus decreasing the energy consumption, different improvements have been put forward and new desalination methods have been developed. Therefore, the development of desalination technology is then exhaustively analyzed and forecasted in the following four aspects: improvement for the existing technology, combination of different technologies, desalination technology in combination with new energy, and development of new desalination technologies utilizing unemployed physical phenomena. The improvements mainly focus on the shortcomings of MSF, MED and RO, which are the current major large-scale industrial desalination technologies. The combination of different technologies can integrate their respective advantages to improve the desalination performance and decrease the energy consumption and the cost. The limitations of the decrease of traditional fossil energy and its increasing cost can be broken through the combination with solar, wind, geothermal, ocean and nuclear energies, which is also regarded as a potential solution for climate change. The newly developed desalination technologies have the advantages of lower energy consumption and cost, but most of which are still in lab-scale and need further improvement. Due to the important role in the assessment of the desalination efficient, special attention is paid to the analysis of energy consumption of each desalination technology.

Water scarcity and solar desalination systems in the Eastern Mediterranean region: a case of Northern Cyprus

Water is definitely physically scarce in the Middle East and North Africa (MENA) and the Mediterranean region with less than 1000 m3/capita/year. Water scarcity in these regions is a function of both water supply and water demand as both applies in most of the countries. Using the Falkenmark indicator the Mediterranean region will see increased deterioration in the availability of renewable water. The severe impacts of the non-availability of renewable water in these regions are cushioned by the development of desalination technology. Selection of the appropriate desalination technology, use of renewable energy and a proper method of dealing with high salinity wastewater discharge are very important measures necessary to mitigate the negative impacts of desalination activity, reduce desalination costs and make desalination sustainable and reliable. This work reviews the nature of water scarcity in the Eastern Mediterranean region and advances in solar desalination using the Northern part of Cyprus as a case study.

Analysis and evaluation of various energy technologies in seawater desalination

Abstract At present, in addition to fossil energy and other conventional energy, the application of clean energy resources like wind energy, solar energy and nuclear energy in seawater desalination is rising around the word. It represents the future direction of desalination technology development, meeting the need of a resource-saving and environmentally-friendly society. And the technology has a great prospect of applying in regions in serious shortage of fresh water and energy. This paper concludes the advantages and disadvantages of various schemes by analyzing and comparing seawater desalination technologies of various energy. By analyzing five aspects including technological factor, environmental factor, social factor, economic factor and management factor, this paper proposes an evaluation indicators system of the application of energy technologies in seawater desalination. Evaluate the alternative schemes of the coupling of an island’s seawater desalination project and energy technologies by fuzzy...

Synthetic polymer composite membrane for the desalination of saline water

Abstract 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 per...

Directional solvent for membrane-free water desalination—A molecular level study

Development of desalination technologies has been identified as vital to fulfilling future water demand. In this paper, we use molecular simulation to demonstrate that decanoic acid can dissolve water but reject salt, and itself is insoluble in water. We have recently demonstrated that the directional properties of decanoic acid together with the temperature dependence of water solubility in decanoic acid can be utilized to design a desalination process which extracts water molecules, using the decanoic acid as a directional solvent, from saline source at a higher-than-ambient temperature, and precipitate out the water from the solvent at a lower temperature to recover pure water. Such a desalination process is membrane-free and can make use of low temperature heat sources. Solubility properties between water and decanoic acid are characterized through free energy calculations, and water-decanoic acid interdiffusion processes are studied by molecular dynamics simulations. This work also exemplifies an approach to characterize other possible directional solvents.

Desalination: The recent development path

Desalination nowadays is a mature techno-economic application. This technological achievement started early, immediately after World War II, by scientists and engineers, the desalination pioneers, who established the desalination applications of today. The authors attempt to present here the most important historic features from the early times up to the present day. This paper is dedicated to all those who, through their many years of hard work, achieved by means of R & D on one hand, the development of desalination technologies, and on the other hand, promoted, by bringing people in contact to exchange ideas, the development and application of desalination and related fields. It is a historical description based on experienced memories and historical references.

Concentration of brines from RO desalination plants by natural evaporation

Development of desalination technologies in recent years, specially in the case of reverse osmosis process, enables now the massive production of water with a moderate cost, providing flexible solutions to different necessities within the fields of population supply, industry and agriculture. The great development of reverse osmosis (RO) technology has been a consequence of several factors such as energy consumption reduction and membrane cost decrease. Nevertheless, one of the problems of RO desalination plants is the generation of a concentrate effluent (brine) that must be properly managed. In the case of seawater desalination plants the brine is usually discharge to the sea since they are placed near it. However, in the case of brackish water desalination, brine management can be specially critic if the plants are placed far from the coast and far from any public channel or water-treatment plant where discharge the brine. The best option in this case is to concentrate the brine by reverse osmosis up to the technical limit of the process (around 70 g/L of salinity), and after that continue concentrating by means of evaporation until getting a solid waste that can be valued or directly managed by an authorised company. The aim of this work is to asses the viability of using natural evaporation (without heat supply) opposite to conventional evaporation for concentrating brines from brackish desalination plants. The main purpose of applying natural evaporation is to reduce the energy consumption of the treatment and the associated costs.

Portable water purification system integrated to a heat transformer

Water is a natural resource essential for life and for most economic activities developed on earth. Population growth and lack of water in some regions of the world has led humans to design and implement new technologies to use water in an efficient way. Water quality requirements in the industrial sphere are higher everyday. Development of desalination technology through a water purification system integrated to heat pumps has taken more than two decades. Absorption heat pumps use low quality energy in a waste heat form and a small quantity of high quality energy. This characteristic has made possible using these systems in quite a few places. The following work presents the results of the experimental tests applied to a portable water purification system integrated to a heat transformer (TTAPPA), where the low quality waste heat is simulated and LiBr-water is used as a working solution.

Portable water purification system integrated to a heat transformer

Water is a natural resource essential for life and for most economic activities developed on earth. Population growth and lack of water in some regions of the world has led humans to design and implement new technologies to use water in an efficient way. Water quality requirements in the industrial sphere are higher everyday. Development of desalination technology through a water purification system integrated to heat pumps has taken more than two decades. Absorption heat pumps use low quality energy in a waste heat form and a small quantity of high quality energy. This characteristic has made possible using these systems in quite a few places. The following work presents the results of the experimental tests applied to a portable water purification system integrated to a heat transformer (TTAPPA), where the low quality waste heat is simulated and LiBr-water is used as a working solution.

The use of modelling and reuse techniques in the development of water management systems in basins with limited water resources

Drawing on experiences in New South Wales from 1950 to 1980 in modeling and re-use techniques in the development of desalination technology and its application in fresh water production for potable use, the paper describes how Australia realized its responsibilities in developing participative and sustainable approaches to land use and water resources management. An analysis of the lessons from the operation of the Bayswater zero-discharge power station significantly contributed to the debate on sustainable approaches, highlighting that no management policy of a water basin can be implemented without a model based on reliable data from all sectors (including the environment), and no management model can be implemented without the participation of all stakeholders. These ideals were reflected in the conception and establishment of the Murray-Darling Basin Commission. The Commission succeeded in bringing together all major stakeholders in this huge basin, though it took more than 15 years to do so. While widely recognized as one of the most advanced and successful experiences in integrated management of a drainage basin, it has still not achieved the reversal of many unsustainable agricultural practices, giving a clear indication of the difficulties and time required for producing sustainable solutions.