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Capacitive deionization (CDI) has shown potential in addressing freshwater scarcity. CDI's electrode design is a key to better performance as it determines the extent of water purification. For carbon electrodes, the pore structure is an important factor influencing removal kinetics and ion storage. Herein, porous carbon nanofibers with diameters ranging from 277 to 348 nm were fabricated from blends of polyacrylonitrile (PAN) and cellulose acetate (CA) through electrospinning and carbonization. Surface area and pore properties were adjusted by varying the proportions of the precursors while ensuring no adverse alteration to the products' tangible properties. Enhanced pore structure and specific surface area were evident in the blend-based carbon nanofibers. The blend ratio of 2:8 (CA:PAN) had a high specific surface area of 925.47 m²/g and a pore volume of 0.7884 cm³/g. Correspondingly, a high specific capacitance of 177.5 F/g was attained. Desalination performance was determined in batch mode using 500 mg/L NaCl solution. A salt adsorption capacity of 6.57 mg/g and charge efficiency of 0.46 was obtained for the blend that had 20% CA. The carbon nanofibers demonstrated good desalination stability when used repetitively indicating their excellent potential for practical application. [ABSTRACT FROM AUTHOR]

Membrane technology is extensively used for water treatment including desalination to cope with the present water demands. The membrane performance can be analyzed and improved by various methods. A deep understanding of the molecular-level interaction occurring during membrane water treatment can be achieved by molecular dynamic simulations as it helps to develop a thorough knowledge of the systems and processes that occur in an experiment, which are not directly accessible. Through molecular dynamic simulation, a bridge between the experiment and theories can be formed. In this paper, a review of various molecular dynamic simulations that have been employed in the field of desalination using membrane technology is done. Molecular dynamic simulation of the desalination process has been grouped based on the effects of pressure, pore size, functional groups, salinity, electric field, and nanomaterials on the water flux and ion removal. [ABSTRACT FROM AUTHOR]

Maintaining access to a sustainable water resource is becoming increasingly difficult in the midst of the ongoing global water crisis, emphasizing the importance of investing in alternative resources such as desalinated water. Throughout history, the desalination industry has adapted to the specific needs of an era or different environmental conditions by incorporating cutting-edge technologies. The general theme of this paper is the past, the present, and the future of the desalination industry. As such, this research aims to examine the evolution of the desalination industry over time, understand its current state, and ultimately use this knowledge to highlight some important considerations for its future. This review highlighted the immense influence of the energy market on the prevalence of desalination technology in a given region and/or eras. The information gathered here indicates that other sectors, such as agriculture, may need to rely on this unconventional water supply in the future, but there are certain factors ranging from socioeconomic to environmental concerns that need continued and increased research to facilitate the long-term, sustainable development of this practice. [ABSTRACT FROM AUTHOR]

Desalination of seawater is a promising response to solving the lack of drinkable water. The separation of cations and anions is carried out by inserting a desalination cell in the middle of a novel design of photoelectrocatalytic desalination cell (PEDC). Different parameters were evaluated and optimized for increasing the capability of system to desalt hypersaline water. Ultraviolet illumination (UV) was used as the driving force, exciting coated titanium nanotubes on the anode electrode, producing electron/hole pairs that degraded organic matter. Methylene blue degradation by UV irradiation was performed, owing to a high salt concentration level, and desalinated to produce electrical current. Performance of PEDCs was investigated by salt content, pH, and ion-exchange resin. The results indicated that higher total dissolved solid (TDS) removal occurred in acidic environments in anode chamber whereas the maximum produced electrical current occurred in alkaline environments in the cathode chamber. Also, the higher amount of salt content in the middle chamber resulted in the high TDS removal until the amount of electrical conductivity in the middle chamber reached 190 mS/cm. The TDS removal rates with and without using resins in the middle of the desalination cell after 10 days were 70.69% and 51.37%, respectively. [ABSTRACT FROM AUTHOR]

The importance of membrane technology development in our daily life cannot be overemphasized. Over the past decades, membrane technology has become very popular in providing potable water for mankind. However, old technologies (such as reverse osmosis and ultrafiltration) which are highly energy intensive are still very common in water treatment industries. In this review, the capability of low energy consumption membrane distillation (MD) technology is reviewed with emphasis on material development and energy requirement. We begin by reviewing the history of the MD process, configurations, module types, membrane materials, material fabrication methods, material properties, material modification techniques, application, and energy requirements. Factors which influence the performance of MD -- both design and operating conditions -- are then extensively discussed. Furthermore, we report desalination and wastewater treatment as the hottest areas of application where MD has gained significant interest. Membrane hydrophobicity and fouling resistance are identified as pivotal areas where improvement in MD performance is being sought. We then discuss various industries where MD is presently being applied. We conclude by highlighting the energy requirements of MD and identify solar energy as a renewable energy resource which could meet the energy requirement of MD technology. It is hoped that this review paper will foster interest in and provide insights on material development for membrane distillation application. [ABSTRACT FROM AUTHOR]

In this study, we developed a comprehensive two-dimensional computational fluid dynamics (CFD) model using COMSOL™ Multiphysics to describe and simulate heat transfer, mass transfer and fluid flow in the flat sheet vacuum membrane distillation (VMD) under laminar flow conditions. A combination of Knudsen and Poiseuille flow was applied to study mass transfer across the membrane. The effect of variation of Reynolds number, inlet feed temperature and degree of vacuum on different parameters (mass flux, temperature polarization coefficient-TPC, concentration polarisation, heat transfer coefficient) was studied. There was a positive impact of the Reynolds number (50-200) on mass flux (13.15%), heat transfer coefficient (2.64%) and TPC (1.42%), while CPC decreased by 56.63%. The increment in the heat transfer coefficient was due to fluid mixing on the feed side, while the increment in the TPC was due to a higher temperature gradient across the membrane surfaces. The increment in the feed temperature (323-343 K) resulted in an increase in mass flux by 132.9%, while TPC decreased from 0.98 to 0.90. The degree of vacuum (640-750 mm Hg) increased mass flux and heat transfer coefficient by 72.52 and 425.83%, respectively, while the TPC decreased by 8.81%. The feed temperature was the most sensitive parameter with respect to mass flux. The developed CFD model was validated with in-house experimental results with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Condensation irrigation (CI) combines desalination with subsurface irrigation. Here, solar stills are used to heat and humidity air, which is condensed in underground drainage pipes to irrigate the soil, directly in the root zone. This article describes and evaluates a CI field test at Shahid Chamran University of Ahvaz in Iran. The objective was to gain a deeper understanding of the CI system in the production of drinking and irrigation water and to do a detailed assessment of heat and moisture transfer in the soil. Perforated and unperforated PVC pipes were used in two separate experiments while airflow properties, soil temperature and humidity, and ambient air temperature were monitored. The system produced 6 kg of irrigation water during 8 hours in the 25 m long pipe. When using an unperforated pipe, 4 kg of freshwater was collected at the pipe ending after 8 hours of operation. The preliminary economic analysis of irrigation system indicates a payback time of less than six years. [ABSTRACT FROM AUTHOR]

In this research, the performance of a stepped solar still has been experimentally evaluated. For this purpose, a parabolic trough collector has been used to preheat the saline water entering the solar still. Also, two flat external reflectors have been employed to increase the amount of solar energy received by the steps and the collector of the system. The findings of this research indicate that the use of two flat external reflectors is more effective than using the trough collector. Also, it is more efficient to apply both mechanisms simultaneously than to use them separately. According to the obtained results, the distilled water output of the solar still is 760, 1,560, 2,440 and 2,760 ml/m², respectively, for operating the conventional solar still, using the trough collector, using the two flat external reflectors, and using the collector and reflectors simultaneously. The electrical conductivity due to the presence of salt and chemical substances dissolved in the distilled water discharged from the still is 255, 215, 62 and 38 micro Siemens per centimetre, respectively, for each of the four mentioned cases. These experiments show that by applying the proposed mechanisms, the amount of distilled water can be increased, and its purity can be enhanced. [ABSTRACT FROM AUTHOR]

An accurate prediction of the performance of water treatment desalination plants could directly improve the global socio-economic balance. In this regard, many researchers have been engaged in the various artificial intelligence applied soft computing techniques to predict actual process outcomes. Inspired by the significance of such techniques, an optimized Particle Swarm Optimization based Artificial Neural Network (PSO-ANN) technique has been proposed herewith to predict an accurate performance of the reverse osmosis (RO) based water treatment desalination plants. Literature suggests that the improvements of the soft computing models depend on their modeling parameters. Therefore, we have included an extended list of nine modeling parameters with a systematic indepth investigation to explore their optimal values. Finally, the model’s simulations results (R² 99.1%, Error ¼ 0.006) were found superior to the existing ANN models (R² 98.8%, Error ¼ 0.060), with the same experimental datasets. Additionally, the simulation results recommend that among many parameters considered, the number of hidden layer nodes (n), swarm sizes (SS), and the weight of inertia (ω) play a major role in the model optimization. This study for a more accurate prediction of the plant’s performance shall pave the way for the process design and control engineers to improve the plant efficiency further. [ABSTRACT FROM AUTHOR]

Cellulose triacetate (CTA) is the first-generation forward osmosis (FO) membrane used for desalination. There have been a few chemical modifications of the CTA membrane surface. This has improved membrane hydrophilicity, water flux, and salt rejection compared with unmodified CTA membranes. Chitosan-containing porous materials as composites have resulted in increased pore characteristics. It has motivated the modification of the surface of the commercial CTA forward osmosis (FO) membrane by surface coating with chitosan (CS)-powdered activated carbon (AC) mix. The membrane morphology was characterized by SEM, FTIR-ATR, contact angle measurement and AFM. Operational conditions for FO such as the orientation of the membrane active layer, feed and draw solution flow rates, and type and concentration of draw salt were optimized with the original CTA membrane. The modified membrane exhibited around a two-fold increase in the water flux and reduced reverse salt flux compared with the original CTA membrane. The improved water flux was attributed to the CS-AC coating enhancing water wettability of the membrane surface and the porous AC generating additional water flow channels. Overall, the water flux of the CTA-CS-AC membrane developed in this work was superior to that of CTA and cellulose acetate (CA) membranes reported in the literature. [ABSTRACT FROM AUTHOR]

This study aims to develop efficient desalination equipment that increases the distilled water production rate and enhances heat transfer in the evaporator. It focuses on the impact of equipment geometry and energy storage during the daytime and nocturnal period. In addition, the effects of the energy storage system, which is placed in two specific areas on the yield of the distillation process with and without energy storage, have been studied. The heat exchanger system provides the energy to the water to be treated in the daytime, while the concrete part provides the energy storage in the desalination evaporator at night time. The experimental test results showed that the increase of distilled water through the heating system is very important in comparison to the productivity of the conventional solar still. The obtained results indicate that the use of energy storage increases productivity by 50% in the nocturnal period. Indeed, the daily productivity of the concrete solar still, strongly affected by the heat transfer produced via concrete to the water evaporator, is presented in this study. It was found that the average daily distillate output of concrete solar still with energy storage is more significant than that of a solar still without energy storage. [ABSTRACT FROM AUTHOR]

One of the important approaches in thermal desalination processes is consumed energy reduction. To achieve this aim, three arrangements of humidification–compression (HC) processes are designed. Two single-stage processes and one double-stage HC process are designed and their performances are compared based on desalinated water production, gained output ratio (GOR) and power consumption. An attempt is made to reduce the power consumption and improve the system performance. All three processes are simulated to examine the effect of operation parameters on HC performance. To validate these simulations, the theoretical results are compared with an experimental rig with a humidifier column of 1.5 m height. The results indicate that the simulation values conform to the experimental data. The effect of minimum approach temperature (ΔTmin) on system performance is investigated for three processes subject to constant operating conditions (feed temperature, water mass flow, air mass flow, and pressure ratio). For this purpose, four values of ΔTmin are considered (7.5, 10, 12.5 and 15 0C) for heat exchanger operations. The results indicate that an increase in ΔTmin in all three cases increases desalinated water volume and GOR. Also, the double-stage HC system has higher water production rate (66.08 kg/h) and higher GOR (17.19) compared with its counterparts. [ABSTRACT FROM AUTHOR]

The photothermal material of Ti3C2 was synthesized by etching Ti3AlC2 with hydrofluoric acid. The asprepared Ti3C2 was deposited on a polyvinylidene fluoride (PVDF) membrane via vacuum filtration to form a Ti3C2/PVDF membrane, which was used for seawater desalination in the next step based on interfacial solar heating. The water evaporation rate of the Ti3C2/PVDF membrane could be enhanced to 0.98 kg/m²·h under 2 sun irradiance, which was 2.8 times and 5.4 times higher than that of pure water (0.35 kg/m²·h) and PVDF (0.18 kg/m²·h) respectively. The temperature difference between the two air-water interfaces with and without the Ti3C2/PVDF membrane was as high as 11.8 °C, confirming the interfacial heating behavior. The water evaporation rate under 2 sun irradiance kept mostly in the range of 0.96-0.86 kg/m²·h over 30 days under continuous operation, indicating the high stability of the Ti3C2/PVDF membrane. Finally, it was demonstrated that the typical water-quality indexes of the condensed fresh water were below the limit values of the Standards for Drinking Water Quality in China, WHO, and US EPA. [ABSTRACT FROM AUTHOR]

Quantifying uncertainty over technologies, costs, and prices that stem from site-specific conditions, technological particularities and future projections is an important element in the investment appraisal of desalination facilities. Yet, the majority of economic assessments in the field of desalination plants, so far, use deterministic estimation methods based on 'best guess' estimates and ceteris paribus sensitivity analyses. Aiming to fill this gap, this paper introduces a new approach towards comparing alternative technological options for desalination facilities under uncertainty based on the Levelized Cost of Water (LCOW). The proposed framework combines Monte Carlo simulations with scenario analysis and random-walk-based models to account for the cone of uncertainty of the LCOW. For purely illustrative purposes, five alternative combinations of desalination technologies and energy sources are examined in the State of Kuwait. The findings show that the proposed framework, although it cannot eliminate uncertainty, can assist decision-makers in managing it by framing the range of possible outcomes of the LCOW. In this way, it offers an insight into the accuracy of the estimates and allows the validation of the impact of risks and uncertainties against the acceptable tolerance level. Yet, several issues need to be addressed in future research. [ABSTRACT FROM AUTHOR]

The use of solar energy for increasing the amount of water heating inside the solar still unit provided an important basis for various process designs in this research. Concerning the wide use of solar energy, solar panels have been used for heating water through thermal elements. In the first setup, a cylindrical parabolic collector (CPC) was used together with 300-watt and 500-watt solar panels, the results of which were then compared with each other. Based on the results the system best performed when more powerful solar panels and a longer CPC device were used. In the second setup, solar heating was achieved by direct use of solar still units. According to comparative results between the two experimental setups, the use of direct thermal elements in the solar still unit provided better performance compared with the use of indirect thermal energy. The highest amounts of freshwater were 3.679 kg and 3.945 kg per day in the first and the second setups, respectively. [ABSTRACT FROM AUTHOR]

Water stress and environmental concerns have driven research into the treatment of produced water. In this study, a combination of forward osmosis and photocatalyst system was used for simultaneous salt removal and treatment of produced water. Furthermore, biosurfactant as a novel draw solution and the three types of forward osmosis membranes (cellulose triacetate with and without titanium dioxide (TiO2) and graphene oxide (GO) nanoparticles) were investigated. The morphology and distribution of the TiO2 and TiO2/GO on the membrane surface were assessed by various analyses including field emission scanning electron microscopy, energy dispersive X-ray and contact angle analysis. The results demonstrated that the reverse salt flux was only 0.2 g/m2 h. Moreover, benzene, toluene, ethylbenzene, and xylene (BTEX) removal efficiency in the cellulose triacetate with TiO2 and TiO2/GO membrane under UVC radiation was 62% and 78%, respectively, while the data obtained in visible light reached 80%. The use of TiO2 and TiO2/GO membranes significantly improved the permeability, water flux, photocatalytic degradation of pollutants and desalination of produced water. [ABSTRACT FROM AUTHOR]

Solar steam generation (SSG) has been proposed as one of the most advanced techniques to trigger solar energy desalination of sea water. Although many efforts have been dedicated to develop SSG devices, the efficiency remains relatively low. Previous work was mainly focused on thermal insulation film and light absorption. Attention has seldom been concentrated on device structure. Inspired by the manner of water transportation within flowers, we designed an artificial SSG unit which can effectively speed up the water transpiration from the bulk to the surface. Another advantage of such a device is that steam generation is separated from the bulk salty solution and thereby the solar thermal evaporation can be improved greatly. As demonstrated via the desalination experiment, the mass change and evaporation rate under 1 solar irradiation can reach as high as 2.51 kg/m2 and 1.26 kg/m2·h-1, respectively. Meanwhile, the evaporation efficiency is 74%. These values are much higher than those of traditional SSG devices and bulk water. [ABSTRACT FROM AUTHOR]

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To obtain efficient salt rejection in saline solution treatment, an asymmetric graphene oxide/Al2O3 membrane was prepared by a spin-coating process. According to microstructure measurement, the membrane has a multilayer structure and graphene oxide has been tightly coated on the surface of the Al2O3 membrane interlayer homogeneously. During the treatment of different aqueous salt solutions, the permeation flux and salt rejection of the membrane were investigated. The results show the permeation flux of the membrane is about 1.254 L•m2•h-1•bar-1 and the salt rejection of the membrane reaches 28.66%, 39.24% and 43.52% for 0.01 mol•L-1 NaCl, Cu(NO3)2 and MgSO4, respectively. The mechanism of the salt rejection of the membrane has been explained in this work. All these results indicate the GO/Al2O3 membrane shows great potential in the desalination field. [ABSTRACT FROM AUTHOR]

Southwest coastal Bangladesh has an acute scarcity of safe drinking water. Both the government and non-government organizations are now promoting reverse osmosis based small scale desalination plants (SSDPs) to ensure safe drinking water. The aim of this study was to assess the physico-chemical and bacteriological quality of the desalination plants (DPs) installed in southwest coastal Bangladesh. Water samples were collected from the inlet and outlet of 10 DPs. The product water mostly complied with water quality standards. High levels of total dissolved solids (TDS) and electrical conductivity (EC) in feed water were reduced significantly after the treatment, although 10% and 20% of the product water samples respectively did not comply with the WHO drinking water standards for those parameters. Compliance of product water with the WHO and Bangladesh drinking water standards for chloride, bicarbonate and sodium were found in respectively 80%, 90% and 70% of the samples, although their concentrations in all the feed water samples were higher than both of the standards. About one-third of the DPs did not meet the drinking water standard for sodium, which may be an important health concern for the people consuming this water. Apart from one of the DPs, all of them complied with the standard for faecal coliform and Escherichia coli. Results suggest that proper maintenance of the SSDPs is necessary to ensure safe drinking water for the coastal population of southwest Bangladesh. [ABSTRACT FROM AUTHOR]

The growing scarcity of fresh water has motivated the use of non-conventional and re-used water resources for agriculture by applying some efficient technologies. The desalination technologies for agricultural irrigation play a major role in satisfying growing water demands in water scarce regions. Due to stringent ionic concentration standards for agricultural irrigation water, desalination for agriculture is more energy demanding and additional post-treatment is requisite. Reverse osmosis (RO) has emerged as an efficient technology, but the burning of fossil fuels to fulfil the energy requirements is becoming expensive and emission of greenhouse gases is recognized as harmful to the environment. Thus, efforts should be directed towards cost reduction by integrating renewable energy resources into the process. Many of the bench and pilot scale trials like integrated RO with low energy such as forward osmosis (FO), nanofiltration (NF), microfiltration (MF) and solar energy revealed significant improvements in cost savings. However, all these modern technologies have their own problems which can be overcome by further research and development. This paper aims to review the main benefits and constraints associated with desalination technologies for agriculture. The available water resources, the desired qualities of water for agriculture and the challenges and future of desalination in agriculture are discussed. [ABSTRACT FROM AUTHOR]

Seawater reverse osmosis (SWRO) desalination technology accounted for 78% of annual new contracted desalination capacity from 2006 to 2012, due of its lower electrical power consumption (3-5 kWh/m3) versus thermal desalination technologies (up to 18 kWh/m3), such as multistage flash and multiple effects. However, the existing SWRO desalination process still needs further improvement to lower the energy consumption. Recently, a novel hybrid SWRO desalination system using pressure-retarded osmosis (PRO) technology has been studied, which can recover a large amount of osmotic power from the concentrated brine. In this study, GS Engineering & Construction Corp. (GS E&C) developed an advanced SWRO-PRO process to economically couple this PRO technology with a conventional SWRO desalination process. To investigate the SWRO-PRO process, pilot and demonstration plants, of 20 m3/d and 240 m3/d PRO treatment capacity, were constructed and thin-film composite spiral-wound PRO membrane modules (8 inches) were assessed. The operating parameters of the pilot plants, such as pressure, temperature, and flow rates of the draw solution and the feed solution, were found to be important factors determining the plant energy consumption and operating efficiency. An economic analysis of a large-scale SWRO-PRO hybrid desalination is also described. [ABSTRACT FROM AUTHOR]

During the Millennium Drought in Australia, a wide range of supply-side and demand-side water management strategies were adopted in major southeast Australian cities. This study undertakes a time-series quantification (2001-2014) and comparative analysis of the energy use of the urban water supply systems and sewage systems in Melbourne and Sydney before, during and after the drought, and evaluates the energy implications of the drought and the implemented strategies. In addition, the energy implications of residential water use in Melbourne are estimated. The research highlights that large-scale adoption of water conservation strategies can have different impacts on energy use in different parts of the urban water cycle. In Melbourne, the per capita waterrelated energy use reduction in households related to showering and clothes-washing alone (46% reduction, 580 kWhth/p/yr) was far more substantial than that in the water supply system (32% reduction, 18 kWhth/p/yr). This historical case also demonstrates the importance of balancing supplyand demand-side strategies in managing long-term water security and related energy use. The significant energy saving in water supply systems and households from water conservation can offset the additional energy use from operating energy-intensive supply options such as inter-basin water transfers and seawater desalination during dry years. [ABSTRACT FROM AUTHOR]

In the current work, the diagnosis of a reverse osmosis desalination unit is reported. Over the two last decades, the studied desalination unit was supplying a 1,200 bed hotel. The feed water was driven from a well near the sea. The desalination unit has two stages giving an average recovery equal to 81%. The behaviour of all water streams with respect to aggressiveness and scaling tendency was assessed. The second stage reject water was shown to exhibit a very high scaling behaviour with an instantaneous precipitation in the absence of feed water pH adjustment. The analyses have shown that the produced water was very aggressive. The second stage module autopsy has revealed a sharp decrease in the membrane performances because of mineral as well as organic fouling. The inorganic scale was essentially made of coesite, calcite and kaolinite clay. The presence of silica and clay was attributed to an inadequate pre-treatment process, whereas the presence of calcite crystals at the membrane surface reveals that the chemical inhibition performed at the pre-treatment process without adjusting the pH was not able to prevent calcium carbonate precipitation. A periodic acid wash of the second stage membranes is then necessary to guarantee the desired objectives of this stage. [ABSTRACT FROM AUTHOR]