Existing Desalination Technologies Research Articles

Recent Advances in Carbon-Based Interfacial Photothermal Converters for Seawater Desalination: A Review

Along with the rapid development of society, freshwater shortages have become a global concern. Although existing desalination technologies have alleviated this pressure to some extent, their long-term environmental impact and energy consumption are still questionable. Therefore, it is necessary to find a new effective way for seawater desalination with cleaner energy. Solar-driven interfacial water evaporation technology has the advantages of environmental protection, energy saving, high evaporation efficiency, low cost, and strong sustainability, and is considered one of the most effective technologies to relieve water resource stress. This review summarized the recent advances in carbon-based interfacial photothermal converters focused on the preparation methods of 2D and 3D photothermal absorbers, the potential ways to enhance the efficiency of photothermal conversion. Finally, this paper proposed the challenges and future trends of interfacial photothermal converters.

Performance of single slope solar stills: A comparative study of conventional and modified stills with nanofluid and reflectors

Nature has naturally desalinated water for centuries through the process of solar heating, where oceanic water transforms into vapor and then returns to Earth as freshwater precipitation. Freshwater is vital for sustaining life, but growing populations, industrial expansion, and increased agricultural production have created a rising demand for it. Desalination has emerged as a potential solution to address water scarcity. Existing desalination technologies fall into two categories: single-phase processes like reverse osmosis and electro-dialysis, and phase-change processes such as distillation and solar stills. While single phase processes provide freshwater, some rely on non-renewable fossil fuels for energy, indirectly contributing to greenhouse gas emissions. Solar distillation, in contrast uses renewable energy from the sun, offers a promising and sustainable alternative for freshwater production. Solar stills employ shallow water basins within enclosed structures, as moisture collects on the interior surface of the glass cover, cooled by natural airflow. In this study, two 250 X 250 mm2 single slope solar stills were designed, one conventional and the other modified with nanofluids and reflectors. The experiment assessed their performance in Hyderabad’s typical climate, with a glass cover slope of 17.45°. Both stills operated with a 1 cm water depth (500 ml) to observe the water distillate output. Readings were recorded for two different nanofluid concentrations (considering 0.08% and 0.1% of Cerium Oxide nanoparticles by volume mixed with water) allowing for a comparison of their cumulative hourly yields and effectiveness in increasing freshwater output.

(Digital Presentation) Electrocatalytic Evaluation of Atomically Dispersed Cobalt on to Boron-Nitrogen Co-Doped Carbon as Chloride Tolerant Cathodes for Desalination Fuel Cells

In recent years, the demand on drinking water escalates the research on desalination technology. Existing desalination technologies utilize fossil fuel driven electricity which gains the researchers attention to develop the use of renewable resources. To address this, we have developed a novel device named desalination fuel cell (DFC), [1] that simultaneously desalinate the feed water and generate electricity by the anodic hydrogen oxidation and cathodic oxygen reduction. The bottleneck of DFC performance largely depends on oxygen reduction reaction (ORR) [2] and requires highly active catalysts. Herein, platinum nanoparticles deposited on activated carbon (Pt/C) is recognized as the state-of-the-art catalysts, however, the scarcity, cost and stability limited the usage in the real application. In addition, the catalyst surface poisoning due to chloride ions (Cl−) from the feed water deteriorates Pt/C catalytic activity in DFC. Therefore, the seek for chloride tolerant and highly active ORR catalysts for DFC are of interest. Several electro-catalysts have been investigated for chloride tolerance ORR activity [3-5]. Very recently, we have reported Fe/N/C as Cl- tolerant ORR catalyst with an on-set potential of 0.84 V vs. RHE in the presence of Cl- ions was on par with that of the state-of-the-art Pt/C in acidic medium [6]. The optimized Fe/N/C catalyst was utilized in DFC cathodes and delivered the highest open circuit voltage of 1.6 V on comparison with Pt/C cathode (1.46 V).The present work describes the synthesis and ORR evaluation of atomically dispersed Co nanoparticles on to boron-nitrogen co-doped carbon catalyst. The catalyst was derived using high temperature pyrolysis of Co and B incorporated zeolitic imidazole framework (ZIF) and systematically evaluated with respect to oxygen reduction activities. The effect of B and Co concentration, and pyrolysis temperature were analyzed using XRD, BET sorption studies, XPS and Raman spectroscopic techniques. Fig. 1a shows transmission electron microscopic image of Co/B/N/C catalyst. It is noteworthy that the black spots indicate the presence of atomically dispersed Co nanoparticles on to carbon support material. Flake-like surface morphology is observed for the catalyst synthesized in the present study (Fig. 1a inset). Fig. 1b shows the comparative ORR linear sweep voltammograms (LSVs) of Co/B/N/C and Pt/C catalysts with and without chloride ions. Notably, almost 140 mV difference in onset potential is observed for Pt/C in the presence of Cl– ions. However, Co/B/N/C catalyst exhibits nearly 10 mV difference in onset potential after the addition of Cl– ions in both acidic and alkaline media. The results show that Co/B/N/C catalyst is tolerance towards Cl– ions in acidic as well as alkaline media.The optimized Co/B/N/C catalyst was utilized as cathode in an indigenous DFC device and the performance was evaluated at room temperature. The DFC device was constructed as three compartments viz., anode, desalination and cathode as shown in the Fig. 2a [6]. In an identical operating condition, the highest OCV of 1.58 V was observed for Co/B/N/C cathode compared with that of Pt/C cathode (1.49 V). Notably, the Pt/C cathode delivered a peak power density of 15.7 mW cm-2 at a load current density of 19.0 mA cm-2. However, Co/B/N/C cathode exhibit a peak power density of 12.1 mW cm-2 at a load current density of 16.5 mA cm-2 (Fig. 2b) which is on-par with the state-of-the-art Pt/C catalyst. Simultaneously, the desalted water concentration was measured using conductivity meter and the results are presented in Fig. 2c. At OCV, the desalted water concentrations were measured to be 0.39 and 0.37 M for Co/B/N/C and Pt/C catalysts, respectively. At 16.5 mA cm-2 load current density, concentration of the desalted water was 0.2 M for Co/B/N/C catalyst and for Pt/C, the concentration at 16.5 mA cm-2 current density was 0.15 M. From the above polarization and concentration profiles, Pt/C shows enhanced performance over in-house synthesized, however, considering non-precious catalyst, the observed results for Co/B/N/C are much appreciable. We are hopeful that the results discussed in this study will provide insights in designing anion tolerant catalyst for the improved DFC performance. Reference Atlas, S. Abu Khalla, M. E. Suss, J. Electrochem. Soc. 2020, 167, 134517.Abdalla, S. Abu Khalla, M. E. Suss, Electrochem. commun. 2021, 132, 107136.Malko, T. Lopes, E. Symianakis, A. R. Kucernak, J. Mater. Chem. A 2016, 4, 142.Mamtani, D. Jain, A. C. Co, U. S. Ozkan, Catal. Lett. 2017, 147, 2903.Tylus, Q. Jia, H. Hafiz, R. J. Allen, B. Barbiellini, A. Bansil, S. Mukerjee, Appl. Catal. B Environ. 2016, 198, 318.A. Asokan, S. Abu-Khalla, S. Abdalla, M. E. Suss, ACS Appl. Energy Mater. 2022, 5, 1743. Figure 1

Design, Modelling and Optimization of a Novel Concentrated Solar Powered (CSP) Flash Desalination System Involving Direct Heating and Pressure Modulation Using Response Surface Methodology (RSM)

The main problem with existing desalination technologies is that they consume high input energy to generate fresh water. Secondly, this energy demand is usually met by conventional sources of energy such as fossil fuels. With limited conventional energy reserves predicted for the future, the focus is on the utilization of renewable sources of energy such as solar, wind, and geothermal energy for powering desalination systems. Such a transformation would make the desalination systems more energy efficient, sustainable, and economical. In this paper, a novel concentrated solar powered (CSP) flash desalination system with direct heating and pressure modulation is presented. A lab-scale prototype was designed, manufactured, and tested for feed water collected from the Arabian Sea and in climatic conditions of Al-Khobar city in Saudi Arabia. The effect of three process parameters, namely, feed water temperature (30–40 °C), feed water flow rate (0.003–0.006 kg/s), and vacuum pressure (0.1–0.3 bar) on distillate production, was investigated. System modelling and optimization were done using Design Expert software and Response Surface Methodology (RSM). The central composite design technique was employed for the optimization of process parameters. The adequacy of the developed distillate production model was verified by ANOVA. The optimum values of feed water temperature, flow rate, and vacuum pressure are reported to be 40 °C, 0.005 kg/s, and 0.1 bar, respectively, resulting in distillate production of 0.001 kg/s.

Mapping of a Novel Zero-Liquid Discharge Desalination System Based on Humidification–Dehumidification onto the Field of Existing Desalination Technologies

It is well-established that increasing demands for fresh water are paving the way for desalination technologies. However, this correlates with an increase in brine production whose treatment and disposal can be complicated and expensive. This paper presents a thermodynamic model to bound the operation and development of a novel Humidification–Dehumidification-based system featuring Zero-Liquid Discharge and off-grid capabilities. The model employs conservation laws to find feasible state points to meet a baseline operation of 10 kg/h of product water separated from a hypersaline feed stream with 100 g/kg salt concentration. The system incurs in a 1039 kWh/m3 energy intensity that can be supplied completely by an electric source or in combination with heating steam. Follow-up sensitivity analysis highlights the robustness of the system in handling variations of 25% in product flowrate and 75% in feed salinity, practically without incurring any additional energy demands. The proposed system operating costs between 72 USD/m3 and 96 USD/m3 are comparable to those of existing brine disposal techniques. Furthermore, an operational map of existing desalination technologies suggests a niche characterized by high recovery rates and high feed salinities that are generally unfulfilled by conventional desalination methods. Overall, the proposed system shows potential for off-grid hypersaline brine treatment. This study sets the stage for future development of physics-based and data-driven predictive models as the proposed system iterates into a pilot plant deployment.

Ferrate-pretreated directional solvent extraction for hydraulic fracturing produced water: Technical and economic feasibility studies

Produced water (PW) generated from hydraulic fracturing operations contains varying amounts of crude oil, sand and dissolved ions, and is typically characterized as hyper-brine. It is often untreatable by existing desalination technologies. This study presents using the directional solvent extraction (DSE) technique to desalinate multiphasic, synthetic produced waters (SPW) using diisopropylamine (DIPA) as the extraction solvent and a ferrate pretreatment method. DSE with ferrate pretreatment achieved an average solvent efficiency of 0.25, 0.13 and 0.03 mL water/g solvent at 1 M, 2 M and 4 M salinity, respectively. The water extraction, turbidity reduction and salinity reduction efficiency were better for DSE with ferrate-pretreatment than compared to DSE alone. DSE's salt rejection rates in the product water were consistently over 95 %, while turbidity reduction was dependent on ferrate dosage used for pretreatment. This process costs an estimated $1.23 per m3 of water extracted from a 4 M brine for a single-pass operation with 95 % heat recoveries.

Desalination technology for energy-efficient and low-cost water production: A bibliometric analysis

Abstract Over the last few decades, steady growth in desalination literature has been observed. However, conducting a quantitative analysis of this literature is still a novelty. This study aimed at carrying out a quantitative analysis of desalination literature published during the last 30 years, using bibliometric and content analysis techniques, based on the Web of Science database. The bibliometric analysis revealed that desalination has received much attention after the year 2000, as 95.4% of literature has been published in two decades after 2000. The text mining analysis showed that the hot themes of desalination research are reverse osmosis optimization, graphene implications, interfacial polymerization, capacitive deionization, carbon nanotube implications, and antifouling techniques. Furthermore, it was observed that many desalination technologies have emerged recently that make it a challenge to choose the right desalination technology for industrialization. Therefore, this study also contributed to identifying the factors that are important for the industrialization of desalination technologies and, based on these identified factors, this study has compared different desalination technologies to unearth the energy-efficient and low production cost technology. Analytical hierarchy process was used for comparing existing desalination technologies based on eight different parameters and it demonstrated that reverse osmosis is the best available technology for desalination.

An ocean thermocline desalination system using the direct spray method

Most of the existing desalination technologies are highly dependent on primary energy, limiting their applications to affluent areas. To address water scarcity in remote areas, it is crucial to exploit the potential of renewable energy sources for desalination. The natural temperature gradient between the surface and deep seabed, i.e., the ocean thermocline, can provide sufficient driving forces for low-temperature thermal desalination. This study presents a thermocline desalination system using the direct spray method. A single-stage spray desalination setup is designed and operated under the temperature ranges that are typical in ocean thermocline. The minimum temperature gradients to drive the system is <5 °C, thus allowing effective integration with thermocline energy. Afterward, thermodynamic and techno-economic analyses are conducted for the thermocline-driven spray desalination system. The major design and operating parameters are observed to have conflicting effects on the water productivity (11–31 m3/day), required heat transfer area (2–4.6 m2 per m3/day of production), and specific energy consumption (2–5.1 kWh/m3). An optimal trade-off of these effects is observed when the system has 2 stages and the cooling water flowrate is 33% higher than the seawater flowrate. Under the optimized conditions, the life-cycle desalination cost ranges from $1–1.5/m3, lower than most decentralized desalination systems operated with solar or ocean thermocline energy.

Commercial Thermal Technologies for Desalination of Water from Renewable Energies: A State of the Art Review

Thermal desalination is yet a reliable technology in the treatment of brackish water and seawater; however, its demanding high energy requirements have lagged it compared to other non-thermal technologies such as reverse osmosis. This review provides an outline of the development and trends of the three most commercially used thermal or phase change technologies worldwide: Multi Effect Distillation (MED), Multi Stage Flash (MSF), and Vapor Compression Distillation (VCD). First, state of water stress suffered by regions with little fresh water availability and existing desalination technologies that could become an alternative solution are shown. The most recent studies published for each commercial thermal technology are presented, focusing on optimizing the desalination process, improving efficiencies, and reducing energy demands. Then, an overview of the use of renewable energy and its potential for integration into both commercial and non-commercial desalination systems is shown. Finally, research trends and their orientation towards hybridization of technologies and use of renewable energies as a relevant alternative to the current problems of brackish water desalination are discussed. This reflective and updated review will help researchers to have a detailed state of the art of the subject and to have a starting point for their research, since current advances and trends on thermal desalination are shown.

A GIS-Based Fit for the Purpose Assessment of Brackish Groundwater Formations as an Alternative to Freshwater Aquifers

A fit for purpose (FFP) framework has been developed to evaluate the suitability of brackish water resources for various competing uses. The suitability or the extent of unsuitability for an intended use is quantified using an overall compatibility index (OCI). The approach is illustrated by applying it to evaluate the feasibility of the Dockum Hydrostratigraphic Unit (Dockum-HSU) as a water supply alternative in the Southern High Plains (SHP) region of Texas. The groundwater in Dockum-HSU is most compatible for hydraulic fracturing uses. While the water does not meet drinking water standards, it can be treated with existing desalination technologies over most of the study area, except perhaps near major population centers. The groundwater from Dockum-HSU is most compatible for cotton production, but not where it is currently grown. It can be a useful supplement to facilitate a smoother transition of corn to sorghum cropping shifts happening in parts of the SHP. Total Dissolved Solids (TDS), Sodium Absorption Ratio (SAR), sodium, sulfate, and radionuclides are major limiting constituents. Dockum-HSU can help reduce the freshwater footprint of the Ogallala Aquifer in the SHP by supporting non-agricultural uses. Greater regional collaboration and more holistic water management practices are however necessary to optimize brackish groundwater use.

Zero thermal input membrane distillation, a zero-waste and sustainable solution for freshwater shortage

The innovative concept of a zero-waste, energy efficient, and therefore sustainable desalination strategy, Zero Thermal Input Membrane Distillation (ZTIMD), is demonstrated to be economically more effective than existing seawater desalination technologies by simulation based on a single-pass Direct Contact Membrane Distillation process using surface seawater as the feed and bottom seawater as the coolant. Thermal energy required for water distillation in the process was satisfied by extracting the enthalpy of the surface seawater using the bottom seawater as the heat sink. Under one of the favorable conditions, the proposed ZTIMD process could produce pure water with a cost of $0.28/m3 at a specific energy consumption of 0.45kWh/m3, which is significantly lower than that of the major existing seawater desalination processes, including the currently dominating technology, Reverse Osmosis ($0.45–2.00/m3). Some major advantages promised by the ZTIMD include (1) With no requirement of external thermal energy input, ZTIMD is an inherently energy-saving process, (2) it is economically competitive to existing desalination technologies, and (3) it is waste-free.

Plasmonic solar desalination

The sustainability of many existing desalination technologies is questionable. Plasmon-mediated solar desalination has now been demonstrated for the first time, using an aluminium structure that absorbs photons spanning the 200 nm to 2,500 nm wavelength range, and is both cheap and 'clean'.

Design Optimization of Shore-Based Low Temperature Thermal Desalination System Utilizing the Ocean Thermal Energy

A model for calculation and optimization of seawater desalination process is presented. In this process, temperature difference between the upper and the lower strata of the ocean is utilized in producing fresh water, by evaporating the warm surface seawater at a reduced pressure and then condensing the generated steam by using the colder seawater drawn from the depth of the ocean to produce distilled water. In order to make the optimization process realistic, the developed model takes into consideration the characteristics of the proposed location such as temperature and density variation with depth, seabed topography, and subsequently the actual lengths of the cold and the warm seawater intake pipes. This article gives details of the process and investigates on the influence of various parameters on its economics. As electricity is the sole source of energy used, the objective function was taken as the specific energy, i.e., the amount of electrical energy required for producing a unit mass of distilled water. Results indicate that distilled water can be produced at a value as low as 5.5 kWh per ton, which makes the process competitive with most of the existing desalination technologies.

Memstill membrane distillation – a future desalination technology

Triggered by the worldwide fresh water scarcity problem and the need for low cost water supply, Memstill is a newly developed membrane-based distillation concept, which has the potential to improve the economy and ecology of existing desalination technologies for seawater and brackish water to a large extent. This technology combines multi-stage flash and multieffect distillation modes into one membrane module. Because a Memstill module houses a continuum of evaporation stages in an almost ideal countercurrent flow process, a high recovery of evaporation heat is possible. The process promises to decrease desalination costs to well below 0.5 USD/m, using low grade waste steam or heat as driving force.

Experimental investigation of an adsorption desalination plant using low-temperature waste heat

Adsorption cycle is a practical and inexpensive method of desalinating the saline and brackish water to produce potable water for both industrial and residential applications. As compared with the commercial desalination methods, the adsorption technology has the unique advantages such as (i) the utilization of the low-temperature waste heat, (ii) low corrosion and fouling rates on the tube materials due to the low-temperature evaporation of saline water, (iii) and it has almost no major moving parts which renders inherently low maintenance cost. In addition, the adsorption cycle offers two important benefits that are not available to the existing desalination technologies; namely, (i) a two-prong phenomenal barrier to any “bio-contamination” during the water generation process as compared with existing methods and (ii) the reduction in global warming due to the utilization of low-temperature waste heat which otherwise would have been purged to the atmosphere. This paper describes an experimental investigation and the specific water yields from a four-bed adsorption desalination plant is presented with respect to major assorted coolant and feed conditions.