Energy Consumption Of Desalination Research Articles

Hybrid vacuum membrane distillation-multi effect distillation (VMD-MED) system for reducing specific energy consumption in desalination

This study focuses on the integration of vacuum membrane distillation into the multi-effect distillation (VMD-MED) system, incorporating heat recovery mechanisms to augment fresh water productivity and minimize the specific thermal energy consumption of the desalination process when compared to stand-alone vacuum membrane desalination systems. The hybrid system was devised by integrating the experimental output of VMD (permeate flux and hot brine) as heat source to MED. Two hybrid systems were investigated in this study: VMD/MED, wherein the heated brine from VMD served as a heat source for MED, facilitating the recovery of sensible heat from VMD; and VMD-HR/MED, where the latent heat of VMD vapor during condensation was utilized to pre-heat the feed water for MED. Based on the performance parameters, it was concluded that the VMD-HR/MED hybrid system outperformed both the stand-alone VMD and VMD/MED hybrid system in terms of efficiency. The latent heat recovery from the condenser of VMD in VMD-HR/MED hybrid system reduces the specific thermal energy consumption (STEC) to 38.42 kWh/m3, however, it enhanced the gain-output-ratio (GOR) and productivity of the system. Additionally, a rise in GOR and a simultaneous decrease in STEC were observed with increasing feed flow rates and vacuum pressure.

Porous carbon flow-electrode derived from modified MOF-5 for capacitive deionization

Flow electrode capacitance deionization technology (FCDI) has drawn an increasing interest as a new strategy for desalination. In this paper, we demonstrated the possibility of porous carbon flow-electrode derived from modified MOF-5 by graphene oxide (C-MOF@G) for capacitive deionization. After adding graphene oxide (GO) as a supporting frame, the prepared C-MOF@G with porous structure remarkably enhanced the specific surface area as high as 933.72 m2/g, which was approximately 3.1 times than that of common MOF-5 derived carbon (C-MOF) in the absence of GO. The complex pore structure was conductive to strengthening ion migration and diffusion. This result exhibited a distinct contrast with commercial activated carbon (AC). At an applied voltage of 1.2 V, a flow rate of 20 mL/min, a carbon content of 4 % and 1 g/L NaCl, C-MOF@G exhibited the remarkable desalination rate of 68.4 μg/cm2/min, accounting for the values being 1.8 and 8.7 times than that for C-MOF and AC. Meanwhile, the desalination energy consumption and efficiency kept relatively stable after the five continuous desalinations cycling. Then this modified MOF-5 derived carbon as flow-electrode will provide a new candidate for the FCDI system, which makes the desalination process much more economical and efficient in the future.

Cyclodextrin-based pervaporation membranes for low-temperature seawater desalination

Water scarcity significantly promotes the development of membrane technology for seawater desalination; however, the energy consumption of desalination is often enormous. Novel membranes that operated under low temperature are especially attractive for more economic and sustainable water supply. Here, in this work, cyclodextrin-based pervaporation (PV) membranes are fabricated for low-temperature seawater desalination. A molecular-level regulation strategy is developed to fabricate PV desalination membranes by tuning the hydrophilicity and inter-polymer chain distance. Cyclodextrin (CD)-based zwitterions with different molecular size, as the crosslinkers, are used to design a series of PV membranes with different inter-polymer chain distances and hydrophilicity, thus exhibiting diverse PV capabilities. HPAN/CD-Py membrane with the shortest inter-polymer chain distance but the highest hydrophilicity, shows the optimal desalination performance, with a flux of 15.0 kg m−2 h−1 and salt rejection of 99.98% in treating seawater solution at low-temperature of 25 °C. In addition, the seawater rejection remained steady at a high level with a stable flux and high rejection (99.98%) during the 120 h operation. Our proposed strategy may provide a meaningful instruction to PV membranes, which is promising for seawater or high-salinity water purification.

Experimental and theoretical work on reverse osmosis - Dual stage pressure retarded osmosis hybrid system

Two-pass reverse osmosis desalination is a common process to treat high-salinity feed solution and provides a low-salinity permeate solution. This study investigated the significance of the energy generated by the dual-stage pressure retarded osmosis (DSPRO) from the reverse osmosis (RO) brine stream. The main components of the DSPRO-RO hybrid system are RO, pressure retarded osmosis (PRO), and energy recovery device, and their models are determined. Dymola software, using Modelica modelling language, was utilized for solving the hybrid system models. Two different flowsheets were built; the first included a two-pass RO, while the second is a hybrid of a two-pass RO (2RO)-DSPRO system. Seawater salinities of 40 and 45 g/L were the RO feed solution, and 1 g/L tertiary treated wastewater was the feed solution of the DSPRO process. The net specific energy consumption was calculated for the 2RO and 2RO-DSPRO systems for 40 and 45 g/L salinities. At a 47 % recovery rate and 40 g/L seawater salinity, the 2RO-DSPRO system was 14.7 % more energy efficient than the 2RO system. The corresponding energy saving at a 47 % recovery rate and 45 g/L seawater salinity was 17.5 %. The desalination energy for the 2RO system was between 3.25 and 3.49 kWh/m3, and for the 2RO-DSPRO system was between 2.91 and 2.97 kWh/m3. The results demonstrate the great potential of integrating the 2RO with the DSPRO to reduce desalination's energy consumption and environmental impacts.

Life Cycle Assessment for Tertiary Wastewater Treatment and Reuse versus Seawater Desalination

Wastewater reuse is now indispensable for meeting the increasing water demand, particularly under conditions of alarming water scarcity, which is now already affecting every continent. The objective of this study is to apply life cycle assessment (LCA) to evaluate the environmental impact and missed opportunity of treating municipal wastewater to tertiary quality and compare it to conventional seawater desalination in the Gulf Corporation Council (GCC) countries, namely: Multistage flash distillation (MSF), multi-effect distillation (MED) and seawater reverse osmosis (SWRO). The study follows the ISO 14040/44 standards and uses a functional unit of 1 Mm3 of tertiary treated effluent (TTE). The modeling concept adopts the cradle-to-gate consequential paradigm. The life cycle inventory is based on fielded data collection, reports, literature and Ecoinvent database processes. The scope includes: infrastructure, grid, materials, energy requirements, chemical additives and sludge disposal; for primary, secondary and tertiary treatment. The life cycle impact assessment is applied on both the characterized and normalized levels using the ReCiPe method. Compared to distillation, TTE exhibits an average reduction of 94% in fossil depletion. For climate change and particulate matter, an average reduction of 79% and 73% can be realized respectively. The large difference is due to energy consumption in desalination, despite that fact that the energy considered is only the allocated portion to distillation in the cogeneration total, using exergy specific power consumption.

Desalination Technology in South Korea: A Comprehensive Review of Technology Trends and Future Outlook.

Due to advances in desalination technology, desalination has been considered as a practical method to meet the increasing global fresh water demand. This paper explores the status of the desalination industry and research work in South Korea. Desalination plant designs, statistics, and the roadmap for desalination research were analyzed. To reduce energy consumption in desalination, seawater reverse osmosis (SWRO) has been intensively investigated. Recently, alternative desalination technologies, including forward osmosis, pressure-retarded osmosis, membrane distillation, capacitive deionization, renewable-energy-powered desalination, and desalination batteries have also been actively studied. Related major consortium-based desalination research projects and their pilot plants suggest insights into lowering the energy consumption of desalination and mitigation of the environmental impact of SWRO brine as well. Finally, considerations concerning further development are suggested based on the current status of desalination technology in South Korea.

The optimized flow-electrode capacitive deionization (FCDI) performance by ZIF-8 derived nanoporous carbon polyhedron

• Nanoporous carbon polyhedron (NCP) with high specific surface was prepared as flow-electrode. • A high salt removal rate of 20.98 μg cm −2 min −1 was obtained in FCDI system. • The increased NCP content can improve the desalination performance. • Desalination performance of NCP can keep stable even after long-time cycles. Flow-electrode capacitive deionization (FCDI) has developed as a promising technology to realize the highly efficient and low-energy-consumed desalination process. To deliver better desalination performance, the flow-electrode with high capacitance and low resistance is essential. As for the traditional AC flow-electrode, although it is low-cost and wide-applied, the relatively low capacitance and poor conductivity are the limitations for its further development. Here, we propose a novel flow-electrode material, nanoporous carbon polyhedron (NCP), which was prepared by ZIF-8 followed by carbonization and activation process and have a higher surface area and larger specific capacitance than AC. The desalination experiments showed that the current density of FCDI system based on NCP is about 2.5 times larger than that of AC, exhibiting a higher desalination rate of 20.98 μg cm −2 min −1 for NCP. Moreover, the desalination energy consumption and efficiency can keep relatively stable after the long-time continuous desalination cycling. This current research may be significant for the future promising application of high-performance FCDI system.

Aquatech's AI partnership addresses desalination's energy consumption

Aquatech International is partnering with Pani Energy, a Canadian artificial intelligence (AI) analytics solution provider for water applications, to reduce the energy and cost associated with desalination.

Wetting-resistant photothermal nanocomposite membranes for direct solar membrane distillation

Efficient use of solar energy for desalination is one strategy to solve the world's water scarcity issues. In this work, a dual functional, omniphobic−photothermal nanocomposite membrane was developed to achieve wetting resistance and low energy consumption in desalination by direct solar membrane distillation (DSMD). The membrane was prepared by forming a hierarchical structure of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FAS17) modified carbon black (CB) nanoparticles (NPs) on a polyvinylidene fluoride (PVDF) membrane surface. The fluorinated CB NPs absorbed sun light to provide localized heating for DSMD, which increased membrane flux by 25% upon simulated solar irradiation at one sun unit. The utilization efficiency of solar energy in the DSMD process, 75.4%, is more than one order of magnitude higher than the energy efficiency of the conventional direct contact membrane distillation process. Furthermore, the re-entrant structure formed by the CB NPs together with the hydrophobic FAS17 coating led to low surface energy and hence omniphobicity, increasing the contact angle of the 80 vol% ethanol-in-water from 0 to 94.2°. As a result, the dual functional membrane exhibited much higher resistance to wetting by surfactants. Whereas the pristine PVDF membrane was wetted by 0.2 mM SDS, SDS had no effect on the dual function membrane over the whole SDS concentration range tested (0.1–0.4 mM). The photothermal activity, improved thermal efficiency, and strong wetting resistance make the dual functional omniphobic−photothermal membrane an excellent membrane material for the DSMD process.

Reduced titania nanorods and Ni–Mo–S catalysts for photoelectrocatalytic water treatment and hydrogen production coupled with desalination

This study presents a ternary hybrid solar desalination process coupled with photoelectrocatalytic water treatment and H2 production in a single device. The desalination of brackish water in the desalination cell is initiated via photoinduced charge generation with a thermochemically reduced TiO2 nanorod array photoanode. The chlorides transferred to the neighboring anolyte at ion-transport efficiency of ∼100% are photoelectrochemically transformed into reactive chlorine species responsible for the decomposition of urea into nitrate in the anolyte. Simultaneously, the H2 production with a Ni–Mo–S (Ni2S3/MoS2) composite catalyst grown onto porous Ni substrate is achieved at Faradaic efficiency of ∼90% in the catholyte concentrated with desalted Na+. Regardless of the operation condition, the H2 energy contributes to the reduction in the energy consumption for desalination by 25%–30%. The overall ternary hybrid process is understood systematically, and the physiochemical properties and electrochemical behavior of the Ni–Mo–S catalysts are examined.

Design, modelling and optimisation of a batch reverse osmosis (RO) desalination system using a free piston for brackish water treatment

Batch RO is a concept for achieving the minimum possible energy consumption in desalination, even at high recoveries. We present a batch RO design that operates cyclically in two alternating phases. The system uses a free piston, housed in a pressure vessel, to transfer pressure from the feed fluid to the recirculating fluid. No complete design procedure for this configuration currently exists. To fill this gap, we present a systematic model based on justified assumptions. The specific energy consumption (SEC) is broken down into contributions from the feed pump, recirculating pump, and auxiliary loads. The calculation of feed pump SEC includes three non-ideal correction factors: concentration polarisation, longitudinal concentration gradient, and salt retention. The model requires only the solution of explicit algebraic equations, without need of specialised numerical techniques, and is implemented in a simple 3-step procedure. The model is applied to an example involving desalination of brackish water using an 8-inch spiral-wound RO module. The design parameters are explored and optimised in a sensitivity analysis. The results show that the optimised batch RO at 80% recovery can produce fresh water with low-energy consumption, achieving 2nd law efficiency of 33.2% compared to 10–15% for conventional brackish water RO.

Response to comments on “comparison of energy consumption in desalination by capacitive deionization and reverse osmosis”

Response to comments on “comparison of energy consumption in desalination by capacitive deionization and reverse osmosis”

Comments on “Comparison of energy consumption in desalination by capacitive deionization and reverse osmosis”

Comments on “Comparison of energy consumption in desalination by capacitive deionization and reverse osmosis”

Comparison of energy consumption in desalination by capacitive deionization and reverse osmosis

Capacitive deionization (CDI), which is based on the electrosorption of ions by porous electrodes, is an emerging technology for brackish water desalination. Understanding the key drivers of energy consumption in CDI and benchmarking CDI with reverse osmosis (RO), the current state-of-the-art for brackish and seawater desalination, is crucial to guide the future development of desalination technologies. In this study, we develop system-scale models to analyze the energy consumption and energy efficiency of CDI and RO over a wide range of material properties and operating conditions. Using our models, we explore how the energetic performance of CDI and RO compare as a function of feed salinity, water recovery, salt rejection, and average water flux, which is normalized by electrode and membrane area in CDI and RO, respectively. Our analysis shows that RO is significantly more energy efficient than CDI, particularly when targeting higher salinity feed streams and higher salt rejection values. For brackish water with a salt concentration of 2000 mg L−1, achieving 50% water recovery and 75% salt rejection, with an average water flux of 10 L m−2 h−1 using CDI requires a specific energy consumption of 0.85 kWh m−3, more than eight times that of RO (0.09 kWh m−3). Importantly, our results also indicate that current efforts to improve electrode materials can only marginally reduce the energy consumption of CDI. We conclude with a discussion highlighting other important factors, such as capital cost, electrode stability, and membrane fouling, which affect the efficacy of CDI and RO for low-salinity desalination.

Tuning roughness features of thin film composite polyamide membranes for simultaneously enhanced permeability, selectivity and anti-fouling performance

Thin film composite (TFC) polyamide membranes set the golden standard for reverse osmosis technology, but tuning their permeability and selectivity remains a major challenge because of the inherent permeability-selectivity trade-off. Creating nano-sized voids within the polyamide rejection layer can tune the membrane roughness and increase its effective filtration area to improve the water permeability. Here we prepare nano-foamed polyamide rejection layers by adding sodium bicarbonate into the aqueous solution of amine monomers. We show a systematic evolution of the roughness structure of polyamide membranes, with increasingly leaf-like and belt-like features appearing under enhanced nano-foaming conditions. These nano-foamed features can result in remarkable improvements in both water permeability and salt rejection and reduce membrane fouling propensity at the same time. Our study paves a new research direction for designing future generation of desalination membranes, which holds vast potential to reduce the cost and energy consumption of desalination while achieving improved product water quality.

Techno-economic evaluation of various RO+PRO and RO+FO integrated processes

Pressure retarded osmosis (PRO) and forward osmosis (FO) have been proposed to integrate with seawater reverse osmosis (RO) in order to reduce the overall energy consumption of desalination. However, their economic advantages in comparison to conventional RO have not been validated. This study aims to use well-developed mass transfer and economic models to investigate the technical and economic feasibilities of four potential RO and PRO/FO hybrid processes. They are (1) RO and open-loop PRO (referred to as RO+oPRO) to harvest the osmotic energy using energy recovery devices (ERDs), (2) RO and closed-loop PRO (RO+cPRO) to harvest the osmotic energy and recycle the pressurized and diluted brine as seawater feed to RO, (3) RO and FO post-dilution (RO+FO) to dilute and recycle the RO brine, and (4) seawater feed pre-dilution by FO before entering RO (FO+RO) to reduce the RO operating pressure. RO+oPRO takes advantage of the osmotic energy and reduces the RO operating expenditure (OpEx), but requires huge additional capital expenditure (CapEx) that renders it uneconomical. RO+cPRO reduces both OpEx and CapEx because it eliminates the need of additional ERDs and downsizes the seawater intake, pretreatment and brine discharge units. RO+FO achieves the same CapEx saving as RO+cPRO but at an increased OpEx. FO+RO dilutes the seawater, reduces the RO operating pressure and significantly lowers OpEx, especially at a high RO recovery. Based on the analysis, we believe that RO+cPRO and FO+RO are the two most economical and promising processes to reduce both OpEx and CapEx of seawater desalination.

Coupling desalination and energy storage with redox flow electrodes.

Both freshwater shortage and energy crisis are global issues. Herein, we present a double-function system of faradaic desalination and a redox flow battery consisting of VCl3|NaI redox flow electrodes and a feed stream. The system has a nominal cell potential (E0 = +0.79 V). During the discharge process, the salt ions in the feed are extracted by the redox reaction of the flow electrodes, which is indicated by salt removal. Stable and reversible salt removal capacity and electricity can be achieved up to 30 cycles. The energy consumption is as low as 10.27 kJ mol-1 salt. The energy efficiency is as high as 50% in the current aqueous redox flow battery. With energy recovery, the desalination energy consumption decreases greatly to 5.38 kJ mol-1; this is the lowest reported value to date. This "redox flow battery desalination generator" can be operated in a voltage range of 0.3-1.1 V. Our research provides a novel method for obtaining energy-saving desalination and redox flow batteries.

Energy consumption for desalination — A comparison of forward osmosis with reverse osmosis, and the potential for perfect membranes

Reverse osmosis (RO) is now the most ubiquitous technology for desalination, with numerous seawater RO plants being built in water-stressed countries to complement existing water resources. Despite the development of highly permeable RO membranes, energy consumption remains a major contributor to total cost. Forward osmosis (FO) is receiving much attention as a potentially lower energy alternative to RO. However, the draw solution (DS) recovery step in FO requires significant energy consumption. The present study is a modelling approach, simulating FO and RO desalination under various process conditions and process flow schemes using the Aspen Plus environment. Results suggest that there is practically no difference in specific energy consumption (SEC) between standalone RO, and FO with nanofiltration (NF) DS recovery; this can be generalised for any pressure-driven membrane process used for the DS recovery stage in a hybrid FO process. Furthermore, even if any or all of the membranes considered, FO, RO or NF, were perfect (i.e. had infinite permeance and 100% rejection), it would not change the SEC significantly. Hence, any advantage possessed by the FO with NF recovery process derives from the lower fouling propensity of FO, which may reduce or eliminate the need for pre-treatment and chemical cleaning.

Energy Issues in Desalination Processes

Water, energy, and environmental issues are closely related. New water techniques consume energy, and innovative renewable energy techniques using biofuels and biodiesel consume an incredible amount of water. Different desalination techniques that consume different energy levels from different sources are in use today. Some people, environmentalists, decision makers, and even scientists, mainly in nonscientific publications, consider energy consumption in desalination to be too high and are seeking new ways of reducing it, which often involves increasing capital investment. Efforts should be directed at reducing not only energy consumption but also total water cost. A competent grasp of thermodynamics and heat and mass transfer theory, as well as a proper understanding of current desalination processes, is essential for ensuring beneficial improvements in desalination processes. Thermodynamics sets the absolute minimum limit of the work energy required to separate water from a salt solution. Unavoidable irreversibilities augment the actual energy consumption, yet modern desalination techniques have succeeded in considerably narrowing the gap between actual and limiting energy levels. The implication of this smaller gap is that only marginal energy reductions are possible. The current energy consumption of different desalination processes is reviewed in this paper. A comparison with other common energy-consuming ventures leads to some interesting conclusions.

Zeroing in on ZLD Technologies for Inland Desalination

Many communities need affordable inland desalination to meet increasing water demands by making brackish water sources available for use in supplementing existing water supplies or to control the salinity of current sources. Most desalination technologies generate two streams, a desalinated product water stream and the saline byproduct referred to as concentrate. Management of the concentrate stream, typically 15‐30% of the feed flow, presents the greatest challenge to implementing desalination. This research demonstrated the novel use of existing technologies to reduce the cost and energy consumption for desalination with zero liquid discharge (ZLD) of concentrate. Test results indicated treatment of the concentrate for further recovery by a second application of reverse osmosis could lead to significant reductions in desalination costs and energy consumption to achieve ZLD. The approach described here could cut ZLD costs by 50‐70% and reduce energy consumption by 60‐75% compared with established methods currently in use.