Water Desalination Process Research Articles

Renewable energy integration in water desalination: State-of-the-art review and comparative analysis

This paper offers a comprehensive overview of advanced water desalination systems powered by renewable energy sources, specifically focusing on developments in the past decade. Solar energy is particularly emphasized as a pivotal resource for powering diverse desalination methods, including membrane distillation, reverse osmosis, humidification-dehumidification, forward osmosis, and hybrid systems. The primary objectives of this study encompass evaluating current advancements in renewable energy systems, especially solar energy, for driving water desalination processes. Furthermore, the study aims to identify gaps in research, challenges, and recommendations within these processes, and to assess the performance and refinement potential of hybrid desalination systems. Through a comprehensive analysis of various investigations, integrated effectiveness and cost-efficiency are examined, focusing on practical energy utilization. Notably, the analysis reveals the potential of hybrid desalination systems to reduce energy consumption. For instance, the hybridization of forward osmosis with membrane distillation showcases a significant energy ratio decrease from 0.89 to 0.64. Moreover, the combination of humidification-dehumidification with reverse osmosis is shown to reduce energy usage while enhancing freshwater output by up to 38% compared to standalone reverse osmosis. However, challenges persist, such as the need for improved integration of hybrid systems with concentrated solar collectors like photovoltaic thermal and concentrated photovoltaic thermal technologies.

Smart dynamic hybrid membranes with self-cleaning capability

The growing freshwater scarcity has caused increased use of membrane desalination of seawater as a relatively sustainable technology that promises to provide long-term solution for the increasingly water-stressed world. However, the currently used membranes for desalination on an industrial scale are inevitably prone to fouling that results in decreased flux and necessity for periodic chemical cleaning, and incur unacceptably high energy cost while also leaving an environmental footprint with unforeseeable long-term consequences. This extant problem requires an immediate shift to smart separation approaches with self-cleaning capability for enhanced efficiency and prolonged operational lifetime. Here, we describe a conceptually innovative approach to the design of smart membranes where a dynamic functionality is added to the surface layer of otherwise static membranes by incorporating stimuli-responsive organic crystals. We demonstrate a gating effect in the resulting smart dynamic membranes, whereby mechanical instability caused by rapid mechanical response of the crystals to heating slightly above room temperature activates the membrane and effectively removes the foulants, thereby increasing the mass transfer and extending its operational lifetime. The approach proposed here sets a platform for the development of a variety of energy-efficient hybrid membranes for water desalination and other separation processes that are devoid of fouling issues and circumvents the necessity of chemical cleaning operations.

Thermal analysis of integrated hydrate-based desalination system with intermediate fluid type LNG vaporizer

With a growing population, excessive industrial activities, and limited freshwater resources, water scarcity is considered a prime global risk. Desalination of seawater is essential to overcome former challenges, however, energy-intensive water desalination processes have pushed the water community towards sustainable and economical seawater desalination techniques. This study presents a hydrate-based desalination (HyDesal) system where liquefied natural gas (LNG) is suggested to be used as a source of cooling energy and hydrate former. The study's novel use of an intermediate fluid type LNG vaporizer (IFV) is a prime objective. Detailed analysis of the complex heat transfer processes of the LNG vaporizer is conducted to estimate the thermal performance of the LNG vaporizer using a model based on the heat transfer analysis of each of the three sub-components of the IFV. The analysis for each sub-component is coupled as a set of linear equations in matrix form. An algorithm was also designed and developed to assess the thermal parameters of the IFV in an iterative procedure. The former algorithm is suggested to evaluate the performance of the complex heat transfer processes of the IFV. Furthermore, the effect of various operating parameters of the LNG vaporizer on its performance is investigated. Besides, a general thermal analysis of the suggested hydrate-based desalination system is investigated. Design parameters of the desalination system, such as the required mass flow rate of the seawater, mass flow rate of the hydrate former, and operating conditions are evaluated. In addition, a statistical thermodynamics model (modified van der Waals and Platteeuw) was also employed to trace the hydrate phase boundary in the presence and absence of inhibitors. The coupled thermodynamic model provides an accurate update of process T or P conditions along with fractional cage occupancies.

Transient solidification and melting numerical simulation of lauric acid PCM filled stepped solar still basin used in water desalination process

It is crucial to produce potable water from salt water in arid places using a stepped solar still desalination process. This work presents the temperature distribution and phase transformation of lauric acid PCM in inclined stepped solar still desalination system. A second-order finite volume method is employed for discretizing the two-dimensional geometry, while energy, continuity, and momentum equations are solved and then coupled using the second-order PRESTO algorithm. The solidification and melting CFD models have been used to capture the melting stages of lauric acid PCM. Four steps with an inclination of 30° to ground and two different cases with saline water levels of 10 mm and 40 mm have been reported. The results reveal that the temperature and mass fraction of lauric acid PCM strongly depends on the saline water level at each step, the number of steps, the angle of inclination, and the location of the solar still step. The maximum percentage increase in PCM melting fraction is 50%, and a PCM temperature rise of 4 °C is observed in the case of SWL-max compared to SWL-min. The total enthalpy of lauric acid PCM is increased by 30% for the SWL-max water level compared to the SWL-min water level.

Simulation and optimisation of a medium scale reverse osmosis brackish water desalination system under variable feed quality: Energy saving and maintenance opportunity

In this work, we considered model-based simulation and optimisation of a medium scale brackish water desalination process. The mathematical model is validated using actual multistage RO plant data of Al- Hashemite University (Jordan). Using the validated model, the sensitivity of different operating parameters such as pump pressure, brackish water flow rate and seasonal water temperature (covering the whole year) on the performance indicators such as productivity, product salinity and specific energy consumption of the process is conducted. For a given feed flow rate and pump pressure, winter season produces less freshwater that in summer in line with the assumption that winter water demand is less than that in summer.With the soaring energy prices globally, any opportunity for the reduction of energy is not only desirable from the economic point of view but is an absolute necessity to meet the net zero carbon emission pledge by many nations, as globally most desalination plants use fossil fuel as the main source of energy. Therefore, the second part of this paper attempts to minimise the specific energy consumption of the RO system using model-based optimisation technique. The study resulted not only 19 % reduction in specific energy but also 4.46 % increase in productivity in a particular season of the year. For fixed product demand, this opens the opportunity for scheduling cleaning and maintenance of the RO process without having to consider full system shutdown.

Evaluation of Drinking Water Quality and Treatment from Coolers in Public Places in Madinah City, Saudi Arabia

The aim of this work is to prevent the public drinking from water coolers, by using an auto-detection process, if the quality of water is low. Therefore, the proposed water treatment management system for allows the activation of dispensers to provide the best-quality water coolers. The objective is to investigate the quality of the drinking water from coolers in public places in Madinah and to provide clean, safe, and healthy drinking water for the general public. The methodology consisted of performing different analyses, tests, and water treatments, such as physicochemical analyses of the water samples, measurements of the different concentrations of anions, measurements of the concentrations of heavy metals, and bacteriological tests of the water samples. Therefore, 66 water samples were tested, and the experimental values were compared with the reference values given by the World Health Organization (WHO) and Saudi Standards, Metrology, and Quality Organization (SASO) for drinking water. The tests revealed that the physicochemical parameters (pH, EC, TDS, and TH) of different water sources (95.5%) were in accordance with the SASO and WHO values. In addition, all the analyzed water samples (100%) contained permissible levels of nitrates, sulfates, nitrites, and free residual chlorine, as indicated by the results. However, 68.2% of the samples studied had fluoride concentrations below the standard limits. Furthermore, heavy metals such as lead, iron, and others were tested for all water coolers. The measured findings indicated that just one cooler exceeded the permissible limit of 0.3 mg/L for Fe, and the biological contamination testing revealed that 4.5% of the coolers were infected with coliforms. Finally, this research suggests that water coolers should be regularly maintained. Additionally, using the best design for the water desalination process is very important to give the best drinking water quality.

Appraisal of community awareness of water conservation and the importance of greywater as one of the solutions to reduce water wastage in the Kingdom of Saudi Arabia

The Kingdom of Saudi Arabia depends mainly on desalinating seawater for its potable water needs due to the scarcity of natural water resources such as rainwater, rivers and lakes. With the high cost involved in the water desalination process and the state bearing a high percentage of these costs, it becomes a great necessity for the general community to be aware of the importance of water conservation. Reusing grey water in agriculture, industry, or even for potable water production has become an acceptable solution in many countries. Greywater reclamation and reuse have long been considered a favored strategy to overcome severe water scarcity in arid countries such as Saudi Arabia. However, the success of greywater reuse is highly dependent on end users accepting its consumption. This study aims to measure Saudi society’s awareness of the importance of water conservation and their knowledge and acceptance of the use of greywater. A comprehensive questionnaire was developed and distributed to 733 participants, of different age groups and qualifications, from different regions in the Kingdom of Saudi Arabia. The results reveal that there is a clear lack of knowledge about water scarcity in Saudi Arabia as well as the potential use of greywater among the participants. According to the results, the majority of participants welcome the use of greywater for domestic purposes if it is economical. Finally, the paper recommends that more efforts be made to create awareness about the importance of greywater in the country and water conservation. Due to the lack of detailed research on greywater reuse and the extent to which Saudi society accepts this idea, this research becomes relevant in the present context

Appraisal of community awareness of water conservation and the importance of greywater as one of the solutions to reduce water wastage in the Kingdom of Saudi Arabia

The Kingdom of Saudi Arabia depends mainly on desalinating seawater for its potable water needs due to the scarcity of natural water resources such as rainwater, rivers and lakes. With the high cost involved in the water desalination process and the state bearing a high percentage of these costs, it becomes a great necessity for the general community to be aware of the importance of water conservation. Reusing grey water in agriculture, industry, or even for potable water production has become an acceptable solution in many countries. Greywater reclamation and reuse have long been considered a favored strategy to overcome severe water scarcity in arid countries such as Saudi Arabia. However, the success of greywater reuse is highly dependent on end users accepting its consumption. This study aims to measure Saudi society’s awareness of the importance of water conservation and their knowledge and acceptance of the use of greywater. A comprehensive questionnaire was developed and distributed to 733 participants, of different age groups and qualifications, from different regions in the Kingdom of Saudi Arabia. The results reveal that there is a clear lack of knowledge about water scarcity in Saudi Arabia as well as the potential use of greywater among the participants. According to the results, the majority of participants welcome the use of greywater for domestic purposes if it is economical. Finally, the paper recommends that more efforts be made to create awareness about the importance of greywater in the country and water conservation. Due to the lack of detailed research on greywater reuse and the extent to which Saudi society accepts this idea, this research becomes relevant in the present context

Ratchet-Based Ion Pumps for Selective Ion Separations

A computational study shows that a flashing ratchet mechanism can separate equally charged ions based on diffusion coefficients and thus benefit the energy efficiency of water desalination and lithium extraction processes.

Sandstone groundwater salinization modelling using physicochemical variables in Southern Saudi Arabia: Application of novel data intelligent algorithms

Reliable modelling and simulation of groundwater management are crucial for sustainable development. Groundwater salinization is considered challenging and has recently led to the development of several emerging advancements and technologies, which grant a feasible solution to integrated water management and desalination processes. For this purpose, Electrical Conductivity (EC) as the early Salinization sign is modelled using various computational techniques, namely, Least Square-boost (LSQ-Boost), Gaussian Process regression (GPR), support vector regression (SVR) and stepwise linear regression (SWLR). The experiment data from sandstone aquifers include parameters from the physical, chemical and hydrogeochemical aspects. Four different input combinations (C1-C4) were developed using linear and ranking nonlinear feature selection and validated modelling results weres assessed by mean square error (MSE), mean absolute error (MAE), root means square error (RMSE), Nash-Sutcliffe efficiency (NSE), and correlation coefficient (R). The analysis also considers the effect of multicollinearity, and the variables affected, such as TDS (mg/L), were not included in the first three combinations. The novel GPR proved superior to other models, with GPR-C1 justified quantitatively (MSE = 0.0255, MAE = 25260.49 and RMSE = 0.1595) in the verification phase. Other intelligent models (SVR, LSQ-Boost) depicted promising for C3 and C4 combinations with more than 88–90% predictive accuracy. The explored novel GPR algorithm offered an excellent and reliable EC prediction tool. The study also suggested using direct correlated positive variables, including hydrochemical and topographic factors, in modelling groundwater salinization. This would lead to more effective water-resources-related planning and decision making.

Energy Storage for Water Desalination Systems Based on Renewable Energy Resources

Recently, water desalination (WD) has been required for the supply of drinking water in a number of countries. Various technologies of WD utilize considerable thermal and/or electrical energies for removing undesirable salts. Desalination systems now rely on renewable energy resources (RERs) such as geothermal, solar, tidal, wind power, etc. The intermittent nature and changeable intensity constrain the wide applications of renewable energy, so the combination of energy storage systems (ESSs) with WD in many locations has been introduced. Thermal energy storage (TES) needs a convenient medium for storing and hence reuses energy. The present work provides a good background on the methods and technologies of WD. Furthermore, the concepts of both thermal and electrical energy storage are presented. In addition, a detailed review of employing ESSs in various WD processes driven by RERs is presented. The integration of energy storage with water desalination systems (WDSs) based on renewable energy has a much better capability, economically and environmentally, compared with conventional desalination systems. The ESSs are required to guarantee a constant supply of fresh water over the day.

Liquefied‐chitin polyurethane foam construction of high‐efficiency solar evaporator for seawater purification

AbstractAs key platforms for efficient photothermal conversion and water evaporation in solar water desalination processes, the design of photothermal interface materials have become an important topic. In this study, we designed an interfacial solar evaporator with liquefied‐chitin PU foams as the base material. In this structure, polyaniline and polypyrrole convert solar energy in thermal energy. After the in‐situ generation of hydrogel in the polyurethane foam to reduce the evaporation enthalpy of water and rapid evaporation of water. Liquefied‐chitin make a PU foam with low thermal conductivity, reduce the heat loss of the water. Notably, the excellent antibacterial property of liquefied‐chitin PU foam can make the photothermal material less likely to grow bacteria in the water and affect the photothermal evaporation efficiency. The water evaporation rates of PANi/PAM and PPy/PAM reached 2.18 and 2.38 kg m−2 h−1 under 1 solar irradiation, with photothermal conversion efficiencies of 136.9% and 149.4%, respectively. This study provides a simple method for converting polymers‐based foam into efficient solar thermal materials for solar‐driven desalination‐related applications.

Biowaste materials derived activated carbon (BMDAC) electrodes for removal of pollutant ions using capacitive deionization: A mini review

Capacitive deionization (CDI) is water desalination process used to remove pollutant ions and water purification. In present review contains current status biowaste material derived activated carbon (BMDAC) electrodes for pollutant ion removal using CDI. This review systematically present the fundamental about CDI, application of CDI, discusses the numerous BMDAC material, comparative tabulation on current status removal of pollutants ion using BMDAC electrodes by CDI and a future scope in present area.

Fabrication of novel thin-film nanocomposite polyamide membrane by the interlayer approach: A review

Thin-film nanocomposite (TFN) membrane based on polyamide (PA) chemistry was widely applied for water purification and desalination process due to the improved water permeance. It remains a great challenge to significantly enhance rejection because of the non-selective defects caused by the aggregation of nanomaterials in the PA layer. Novel interlayer-based TFN (iTFN) membrane containing nanomaterial interlayer between the porous substrate and PA layer is the promising candidate to improve PA integrity and thus overcome the ubiquitous trade-off between permeability and selectivity. The nanomaterial interlayer not only promotes the subsequent interfacial polymerization (IP) but also provides improved pathways for water transport, which leads to simultaneous improvement in membrane permeability and selectivity. This review systematically categorizes nanomaterial interlayers into three types according to construction methods, namely, direct deposition, in situ growth and functional group-anchored in situ assembly (FAISA). The mechanism of interlayer modulating IP process and PA structure, as well as the effects on water transport, are comprehensively analyzed. Encouraging results reveal that using MOFs interlayer prepared by FAISA is the most promising way to break the trade-off in manufacturing reverse osmosis membranes. Finally, challenges and future efforts are presented for advancing iTFN membranes.

Phosphate-decorated Ni3Fe-LDHs@CoPx nanoarray for near-neutral seawater splitting

Direct seawater splitting technique can produce clean hydrogen energy without a complicated water desalination process. However, the oxygen evolution reaction (OER) confronts with selectivity challenge in competing with chlorine evolution and severe corrosion issues of the electrode. In this work, phosphate-decorated Ni3Fe-layered double hydroxides grown on cobalt phosphide nanoarray with both high intrinsic activity and 100 % selectivity towards seawater oxidation in a near neutral electrolyte is reported. The as-prepared electrode shows a low overpotential of 370 mV@10 mA cm−2 with high durability in near-neutral seawater oxidation for 350 h. The phosphate layer on the catalyst surface contributes to the enhanced selectivity by weakening the adsorption of Cl–, and thus avoiding the competing chlorine evolution. Meanwhile, the phosphate layer with a strong proton accepting ability can resist the local pH change on the electrode surface in the neutral electrolyte, affording highly stable seawater splitting for prolonged operations in neutral seawater electrolyte.

GEOTHERMAL ENERGY: AN ALTERNATIVE TO THE WATER–ENERGY DILEMMA IN NORTHEASTERN BRAZIL

This paper proposes geothermal energy as an alternative solution to the water–energy dilemma in the northeastern region of Brazil (NEB). The main application of this study was to provide a theoretical basis to support a different approach to policies minimizing water scarcity and ensuring sustainability. The analysis developed in this study compares the levelized cost of electricity (LCOE) for many different energy sources. The novelty of this study is the use of geothermal energy in the context of the Brazilian Northeast, focusing on water desalination processes, which are expensive in terms of energy. Therefore, this study is highly important because it offers the potential of addressing the energy/economic barrier related to water desalination in environments with economically viable geothermal energy. This is the case in Northeast Brazil with potential for reuse of abandoned oil wells. In the form of enhanced geothermal systems (EGS), geothermal energy is a competitive energy source compared to other sources in the Brazilian Energy Matrix, especially when considering factors in addition to the economic benefits. In the form of EGS, geothermal energy is a suitable option for addressing water scarcity in the northeast region in a sustainable and low-emission manner. This is a strategic opportunity for NEB in the context of energy production and freshwater production through desalination.

Current challenges in hydrate‐based desalination: Kinetic and thermodynamic perspective

AbstractWater scarcity is becoming a severe problem worldwide due to inadequate freshwater resources and swift population growth. Seawater desalination is one of the vital approaches to meet the demand for freshwater. However, energy and associated costs with conventional seawater desalination techniques are incentivizing non‐conventional water desalination processes. Water desalination using gas hydrates formation is one of the emerging non‐conventional processes. In this perspective article, recent advances in hydrate‐based seawater desalination (HBSD) have been critically analyzed to outline a future path towards a clean and efficient hydrate‐based desalination process. It provides a detailed comparison of various processes developed over decades, and measured desalination efficiencies with their process details. Moreover, the current challenges, limitations, and future perspectives of hydrate‐based desalination are also discussed. The study also recapitulates the thermodynamics and kinetics aspects of the hydrate‐based desalination process. In addition, various factors controlling the desalination efficiencies, such as control of the separation of hydrate crystals, salt deposition on hydrate particles, and hydrate morphology, were thoroughly investigated with their proposed process designs. The kinetics of hydrate formation is also assessed, with the possibility of a zero‐induction regime and its consequent impact on hydrate morphology. The current capabilities of the thermodynamics models (Gibbs energy minimization + electrolyte equation of state) were discussed using various commercially available software. Additionally, the role of hydrate promotors is also discussed, which can reduce the higher cost associated with the hydrate‐based desalination process.

Automation of membrane capacitive deionization process using reinforcement learning

Capacitive deionization (CDI) is an alternative desalination technology that uses electrochemical ion separation. Although several attempts have been made to maximize the energy efficiency and productivity of CDI with conventional control methods, it is difficult to optimize the CDI processes because of the complex correlation between the operational conditions and the composition of feed water. To address these challenges, we applied deep reinforcement learning (DRL) to automatically control the membrane capacitive deionization (MCDI) process, which is one of the representative CDI processes, to accomplish high energy efficiency while desalinating water. In the DRL model, the numerical model is combined as the environment that provides states according to the actions. The feed water conditions, that is, the input state of the DRL, were assumed to have a random salt concentration and constant foulant concentration. The model was constructed to minimize energy consumption and maximize desalted water volume per cycle. After training of 1,000 episodes, the DRL model achieved a 22.07% reduction in specific energy consumption (from 0.054 to 0.042 kWh m−3) and 11.60% increase in water desalted water volume per cycle (from 1.96×10−5 to 2.19×10−5 m3), achieving the desired degree of desalination, compared to the first episode. This improved performance was because the trained model selected the optimized operating conditions of current, voltage, and the number and intensity of flushing. Furthermore, it was possible to train the model depending on demand by modifying the reward function of the DRL model. The fundamental principle described in this study for applying the DRL model in MCDI operations can be the cornerstone of a fully automated water desalination process.

Redox flow desalination for tetramethylammonium hydroxide removal and recovery from semiconductor wastewater

As part of humankind’s path towards more sustainable water technologies, redox flow desalination (RFD) has emerged as a promising technology due to its high energy efficiency and easy operation. So far, RFD research has focused on removing and recovering inorganic salts such as lithium-ions, heavy metal ions, or phosphate and nitrate ions. Thus, the potential of RFD in water desalination and resource recovery processes has not been fully demonstrated. Therefore, this study aimed to assess RFD for the valorization of tetramethylammonium hydroxide (TMAH) as value-added organic compounds from wastewater beyond inorganic elements, which is widely being used as an etching solvent, photoresist developer, and surfactant in semiconductor and display industries. By applying a low cell voltage (<1.2 V), a reversible redox reaction allowed a continuous removal of TMAH from the wastewater stream and a simultaneous recovery for reuse as a form of tetramethylammonium cation. The TMAH removal rate was approximately 4.3 mM/g/h with a 40% recovery ratio. With various operational conditions (i.e., TMAH concentration, cell voltage, and flow rate), our system exhibited a high potential for the valorization of TMAH with 60% reduction in capital cost compared to conventional desalination processes.

Identifying greenhouse gas emission reduction potentials through large-scale photovoltaic-driven seawater desalination

To widely promote freshwater production through seawater desalination, renewable energy is expected to replace traditional fossil energy to drive seawater desalination. Based on the input list of components and materials, this study attempts to quantify greenhouse gas (GHG) emissions of photovoltaic-driven seawater desalination projects through replacing traditional thermal power plants and evaluate GHG emission reduction potentials by comparing the thermal- and photovoltaic-driven seawater desalination projects. The GHG emission of photovoltaic-driven seawater desalination project could be reduced by 94.97 % compared with the thermal-driven seawater desalination project, and the GHG emission per unit water production is reduced by 9.8 kg CO2-eq/ton, which could greatly reduce GHG emissions in the whole life cycle. In addition, it is estimated that the large-scale implementation of photovoltaic power stations in LT-MED seawater desalination project can reduce GHG emissions from 1.61E+05 to 3.86E+06 t CO2-eq per year. Through the payback period assessment, the combination of photovoltaic power stations and thermal power plants to drive the seawater desalination project can offset the GHG emission of 7.94E+03 t CO2-eq, and the payback period of photovoltaic-driven seawater desalination project is estimated to be 0.33 years. Using renewable energy instead of traditional thermal energy can reduce the fossil fuel combustion and GHG emissions during the water desalination process, which provides essential references for the low-carbon transition and energy saving in seawater desalination projects in China's coastal areas.