Water Desalination Process Research Articles

Hybrid Ion Exchange Desalination (HIX-Desal) of Impaired Brackish Water Using Pressurized Carbon Dioxide (CO2) as the Source of Energy and Regenerant

Reverse osmosis and electrodialysis are truly the only water desalination processes currently in practice for the entire range of total dissolved solids (TDS) from 400–40,000 mg/L. For high recovery of 80% or more, membrane processes are energy intensive even for a feedwater with a TDS of 1000 mg/L and demand significant pretreatment to avoid precipitation and consequent membrane fouling. In this study, we present for the first time a hybrid ion exchange desalination (HAIX-Desal) process that does not require any semipermeable membrane and can desalinate lean brackish water (TDS ≤ 1500 mg/L) using CO2 as the sole source of energy and chemical regenerant. A hybrid anion exchanger with dispersed ZrO2 nanoparticles (HAIX-NanoZr) and a shell–core weak-acid cation exchange (SC-WAC) resin form the heart of the process. Carbon dioxide or CO2 at 10 atm pressure is the only chemical needed to sustain the process. In contrast to a conventional deionization plant, the anion exchanger, i.e., HAIX-NanoZr, precedes the...

A Review of Solar Energy Collectors: Models and Applications

A current study and discussion in detail about many solar energy collectors of various types, components, classifications and configurations, through the analysis of their performance, is our aim through this review paper. The effects of the geometrical parameters of the solar air collectors as well as the functioning parameters on heat transfer and fluid flow processes were also discussed in detail. The numerical, analytical, and experimental analyses on different models of flat plate solar air collectors with various thermal transfer enhancement strategies were shown in various stages, i.e., modelling, control, measurement, and visualization of airfield, determination of heat transfer, control of friction loss and pressure drop, and evaluation of the thermal performance by the measurement of the augmentation in the temperature of the working fluid at a given solar irradiance and under given flow rate. We concluded this review by identifying the various applications possible for the solar air collectors such as heating and cooling of houses, drying agricultural food materials, and water desalination process.

Determinants of a Pre-Treatment Model in Achieving Economic and Environmental Sustainability in Membrane Desalination

Feedwater pre-treatment plays a significant role in the production performance of water desalination operations. This study aims to formulate a pre-treatment model to evaluate the determinants in achieving economic and environmental sustainability. The research is oriented toward the goal of productivity and performance improvement in the water desalination process. The main objective of this study was to better understand the relationship between feedwater pre-treatment and demineralised water production. The secondary objective was to investigate the effect of an ultrafiltration membrane (UFM) on feedwater production performance. Case studies and literature review are included in this paper. Factors that potentially hinder the efficiency and reduce the load capacity of the desalination process include sand, high levels of ionic bond, biomass and colloid materials. These fouling factors could be eliminated efficiently from the feedwater during pre-treatment. Results demonstrated that the contribution of all inputs to achieve targeted pre-treated water quality (SDI < 3) was significant (p < 0.05) except for activated carbon. Investigations of the pre-treatment process have shown that the silt density index (SDI) is reduced by 45% using a UFM. Higher performance in water desalination was achieved through a higher efficiency in the removal of bacteria, sand, biomass and natural organic materials. Economic analysis showed that overall capacity utilization and operating performance had increased by 11%. This study concludes that quality pre-treatment is essential for achieving higher performance in membrane desalination operations.

A Comprehensive Evaluation Optimal Ground Water Desalination Process with Membranes and Integrated Process Using AHP Method in Qom Province, Iran

A Comprehensive Evaluation Optimal Ground Water Desalination Process with Membranes and Integrated Process Using AHP Method in Qom Province, Iran

Energy Recovery and Process Design in Continuous Flow–Electrode Capacitive Deionization Processes

Flow-electrode capacitive deionization (FCDI) is an electrically driven water desalination process based on the adsorption of ions in pumpable carbon flow-electrodes, also called slurry electrodes, which act as an electrical double-layer capacitor. The pumpability of the electrodes enables a fully continuous operation of FCDI and a whole range of new process designs in contrast to capacitive deionization processes based on static electrodes. In this work, we demonstrate continuous energy recovery of up to 36% of the energy applied during the desalination step during the regeneration of the carbon flow-electrodes. The process performance and energy demand for desalination and pumping of the flow-electrodes are investigated for different FCDI process layouts. The potential of FCDI systems is compared to state-of-the-art desalination methods regarding the energy demand. The energy demand and influence of specific process parameters, such as the applied voltage and the feedwater salinity, are discussed on the...

Influence of electric fields on the efficiency of multilayer graphene membrane.

Multilayer graphene membranes could be considered as an efficient membrane in water desalination processes based on the reverse osmosis (RO) method. In this study, we designed multilayer graphene channels using the molecular dynamics (MD) simulation approach. The effects of different parameters, such as channel width and length, and the pressure on the operation of the designed channels were examined, in the absence and presence of electric fields with various amplitudes and directions. The results indicated that the ion separation and water flow through the channels were modified under the application of the electric fields. Additionally, it has been shown that salt rejection and water flow could be controlled by the channel's structural parameters mentioned above. The obtained results of this study at the molecular level can improve the knowledge of designing membranes for water purification processes. Graphical abstract Using MD method a multilayer graphene membrane was designed to separate Na+ and Cl- ions from a NaCl solution by the aid of external electric field, which can significantly effect the membrane operation.

Multilayer Nanoporous Graphene as a Water Purification Membrane

Porous graphene sheets can be considered as an ultrathin membrane in reverse osmosis water desalination processes. In this paper, employing the molecular dynamics simulation method, the performance of multilayer porous graphene membranes with different pore sizes, layer separation, and layer number were investigated. We found that salt rejection and water flux through the membrane significantly depend on the graphene pore size and number of graphene layers, and controlling these parameters could improve the filtration process. It was shown that our 2-layer designed graphene membranes with the pore radius of 3.3 Å and layer separation of 20 Å, can reject more than 86% of ions. Also, no filtration process had occurred for graphene layer separation less than 5 Å. The results of this study that are described by ion hydration radius and water velocity distributions can be used to improve the knowledge of water desalination at the molecular level, which leads to design more efficient multilayer graphene membranes for water purification.

A novel reduced graphene oxide/carbon nanotube hollow fiber membrane with high forward osmosis performance

Forward osmosis (FO)-based water treatment and desalination processes have attracted increasing attention to address the global water crisis, but its practical application is restricted by the lack of FO membranes with high permeability and selectivity. In this work, an all nanocarbon-based FO membrane was successfully fabricated via constructing reduced graphene oxide (RGO) on a carbon nanotube (CNT) hollow fiber substrate via electrophoretic deposition coupling with chemical reduction processes. Due to the ultra-low friction and well-defined interlayer spacing, the RGO active layer provided high water permeability and ion selectivity. Meanwhile, the high porosity and good wettability ensured the CNT hollow fiber substrate with low internal concentration polarization, and thus increasing water flux. During against DI water feed using 0.5 M NaCl draw solution, the prepared RGO/CNT membrane presented an outstanding water flux of 22.6 LMH, which is 3.3 times higher than that of the commercial membrane. Meanwhile, its reverse salt flux was only 1.6 gMH in comparison to 2.2 gMH for the commercial membrane. These results indicate that the all nanocarbon-based membrane is an alternative membrane for providing clean water in the FO process.

Iron fouling prevention and membrane cleaning during reverse osmosis process

Fouling inhibition is one of the most important challenges in membrane processes. Manifesting under several forms and origins, fouling significantly reduces the performance of membranes during water desalination process. Despite its low concentration, iron is considered as one of the most common inorganic pollutants that generate oxides and hydroxides causing membrane fouling. In the current work, reverse osmosis (RO) membrane fouling caused by iron precipitation was investigated. Herein, the mechanism of iron salt crystallization by oxidation technique was experimentally studied. In addition, the regeneration of a fouled RO membrane by iron precipitation was carried out. Analysis with scanning electron microscopy, infrared (IR) and X-ray diffraction (DRX) spectroscopy has been performed to identify deposits. It was shown that the collected deposit is essentially the lepidocrocite (γ-FeOOH). RO membrane regeneration was carried out using citric acid as a cleaning reagent with a concentration of 0.01%. The efficiency of the treatment was tested through the assessment of the recovery ratio, pressure drop and iron accumulation. In addition, complexation–filtration using citric acid was tested to remove iron during pretreatment step to inhibit membrane fouling. IR and DRX data showed the complex iron citrate (Fe–citrate) was found in the RO retentate, which proves that the complexation–filtration process was clearly efficient.

Optimized fuzzy rule-based energy management for a battery-less PV/wind-BWRO desalination system

Coupling water desalination processes with Renewable Energy Sources (RESs) can be a sustainable and ecological approach to the global water/energy supply crisis. In this regard, small-scale standalone battery-less Brackish Water Reverse Osmosis (BWRO) desalination system powered by a hybrid PV/Wind RES is expected to meet freshwater demand of a small isolated community. One particularity of the proposed architecture deals with the absence of electrochemical storage; only taking benefit of hydraulic storage in water tanks when RE is available. This study puts forward the prime importance of Water/Power flows management optimization. For this purpose, an online Fuzzy Logic-based Energy Management Strategy (FLEMS) is proposed. Firstly, a Hand-Made Fuzzy Inference System (HMFIS) was designed to identify the instantaneous power sharing between the system hydro-mechanical processes (well pumping, water storage and desalination processes). Secondly, an offline genetic algorithm optimization was applied on the HMFIS design in order to optimize the power sharing factor and maximize freshwater production. Then, when applying unknown power profile, the optimized FLEMS demonstrated its performance to improve the system energy efficiency and enhance the brackish water (from 16.7% in autumn to 63% in summer) and freshwater production (to 3.3% during autumn for instance) compared with the HMFIS-based EMS.

Synthesis and dual-objective optimization of industrial combined heat and power plants compromising the water–energy nexus

Water and energy are inextricably linked in various industrial applications. In a Rankine cycle-based combined heat and power plant, water is used as a working fluid for power generation and as a heat carrier. The water used as heat carrier is typically incompletely recovered. Therefore, a considerable amount of make-up water is required. Energy-intensive water treatment technologies are typically used given the strict quality requirements for boiler feed water. Thus, a systematic approach is required for the synthesis and optimization of water desalination and energy conversion processes. In this study, a novel water desalination system that couples thermal membrane distillation and reverse osmosis is proposed. A water–energy integration system that features strong nexus of water and energy is then developed. A dual-objective mathematical model is also formulated for the thermodynamic analysis and optimization of the novel system to minimize fuel and freshwater consumption. Furthermore, a case study is elaborated to validate the proposed novel integration system and optimization methodology. A sensitivity analysis of the key parameters on the performance of the novel system is also conducted. The water consumption objective optimization results show that the freshwater consumption of the proposed novel water–energy integration system is reduced by 54.8% compared with the conventional system. Similarly, the results achieved from minimizing the fuel consumption show that the fuel and freshwater consumptions of the proposed novel water–energy integration system are reduced by 1.7% and 21.0%, respectively, compared with those of the conventional system. The Pareto frontier achieved from the dual-objective optimization offers a trade-off between water and fuel consumption for the proposed water–energy integration system.

Electrochemical Deoxygenation of Aqueous Solutions Using Symmetric Activated Carbon Electrodes in Flow-through Cells

We present a simple electrochemical flow cell using symmetric, unmodified commercially available carbon cloth electrodes that removes 97+% of incoming aqueous dissolved oxygen (DO). The electro-deoxygenation (EDO) cell achieves net O2 removal by leveraging the high overpotential of the oxygen evolution reaction on activated carbon and its propensity to oxidize under anodic polarization in aqueous solution: oxygen is reduced at the cathode via the oxygen reduction reaction (ORR) while water is oxidized and incorporated into surface oxide functional groups at the anode, effectively sequestering dissolved oxygen. The polarized electrodes promote the two-step reduction of DO resulting in some residual hydrogen peroxide in the effluent, which may be beneficial for certain water treatment applications. We modified a cell with Ni cathodes downstream to reduce all H2O2 to water for particularly sensitive applications; in this cell >99% of incoming DO could be removed to sub-10 ppb levels. EDO cells, which currently employ sacrificial anodes, can deaerate 30 L g-1 anode of water at an energy cost of 1 kWh (~$0.10) per 104 L. The technique is versatile, successfully deoxygenating solutions from dilute to seawater concentrations and at flow rates beyond 50 ml min-1 (O2 flux = 10-4 mol s-1 m-2), more than 50x higher throughput DO removal than similar technologies. We demonstrate the utility of an EDO cell as a component in an electrochemical water desalination process; dissolved oxygen removed upstream of a capacitive deionization cell enhances salt adsorption capacity and cell lifetime. Figure 1. (a) Dissolved oxygen removal by an electro-deoxygenation cell stack with six pairs of electrodes (up to t = 1.1 h) and subsequently with an additional H2O2 removal stack (six Ni cathodes and two additional anodes electrically connected in parallel downstream, t > 1.1 h). The device is operated by holding the cathodes, connected in parallel, at an oxygen-reducing potential versus an in situ reference electrode to achieve E c = -0.2 V vs. SHE. The electrolyte is 0.1 M NaCl with an initial flow rate of 50 ml min-1, and the effect of increasing flow to 75 and 100 ml min-1 is shown at t > 4.2 h. (b) Salt removal performance of a capacitive deionization (CDI) cell downstream of our EDO cell; the electrolyte is 10 mM NaCl flowing at 20 ml min-1 and the CDI cell consists of four pairs of carbon cloth electrodes totaling 3.2 g with charging/discharging at V cell = 1.2/0.0 V in a single-pass mode. At t = 24 h, the EDO cell is turned off to highlight its effect on deionization performance. Figure 1

Exergetic Analysis of Flat-Plate Solar Collector used for Desalination by Humidification-dehumidification

AbstractIn the present work, exergy analysis of flat-plate solar collector is presented in details. Flat-plate solar collector is used for heating saline water, which is the first stage of water desalination process by humidification-dehumidification technique. This stage is considered as the most energy intensive stage. Accordingly, it is important to investigate its performance by using exergy analysis. The exergetic efficiency of solar heating system was examined in different ways to determine the most critical parameters that control the solar heating process. A comparison between both traditional energy (based on the first law of thermodynamics) and exergy analyses (based on the second law of thermodynamics) of a flat-plate solar heater type is carried out to show the importance of such exergy analysis and to show the limitations of conventional energy analysis. Exergy analysis gives a comprehensive and detailed behavior of solar heater performance under different conditions.

Preparation of high-efficiency ceramic planar membrane and its application for water desalination

Highly efficient Si3N4 ceramic planar membrane for water desalination process using membrane distillation was prepared by the dual-layer phase inversion tape casting and sintering method. In comparison with typical phase inversion tape casting method, the green tape was formed using Si3N4 slurry on the top and graphite slurry on the bottom. After consuming away the graphite structure, a ceramic membrane consisting of a two-layered structure (skin and finger-like layers) was obtained. The skin layer was relatively tight, and thus could act as a functional layer for separation, while the finger-like layer contained straight open pores with a diameter of 100 μm, acting as a support with low transport resistance. For comparison, typical Si3N4 ceramic membrane was fabricated by phase inversion technique without graphite substrate, resulting in a three-layered structure (skin, finger-like, and sponge layers). After membrane modification from hydrophilic to hydrophobic with polymer derived nanoparticle method, the water desalination performance of the membranes was tested using the sweeping gas membrane distillation (SGMD) with different NaCl feed solutions. With the increase of salt content from 4 to 12 wt%, the water flux decreased slightly while rejection rate maintained over 99.99%. Comparing with typical three-layered Si3N4 membrane, an excellent water flux enhancement of over 83% was resulted and the rejection rate remained over 99.99%.

Isothermal Organic Rankine Cycle (ORC) driving Reverse Osmosis (RO) desalination: Experimental investigation and case study using R245fa working fluid

In many regions of the world, groundwater salinity contributes to the growing fresh water deficit. Desalination of saline water via reverse osmosis (RO) could be driven by Organic Rankine cycle (ORC) engines, exploiting readily available low-grade heat (e.g. solar or waste heat). However, the specific energy consumption (SEC) of conventional ORC-RO systems is quite high, while the ORC efficiency is significantly low at low temperatures. To improve on the efficiency and SEC of brackish ground water desalination processes, a novel isothermal ORC driven batch RO desalination system was experimentally investigated, using R245fa working fluid. Results showed about a half of the energy requirement of conventional ORC-RO desalination systems. A case study indicated that the system can be potentially employed in recovering waste heat from a bakery facility to produce about 0.4 L of fresh water per kg of baked food.

Evaluation of the sustainability of the water desalination process in the semiarid potiguar: Study of the Caatinga Grande Community

Evaluation of the sustainability of the water desalination process in the semiarid potiguar: Study of the Caatinga Grande Community

Modelling and optimization of a utility system considering different water desalination technologies

Water and energy are essential for human life and inextricably linked to each other. Water is used in the processes of energy generation and transportation and energy is also used in the processes of water exploitation and transportation. In a utility plant, water is used as working fluid for power generation and heat carrier. Large amount of fresh water is required in the utility system to compensate for the water loss due to boiler blowdown, cooling tower blowdown, cooling tower water evaporation, and process hot utility utilization. Since the requirement of boiler feed water is strict, the water treatment in the industrial utility plant is quite energy intensive. Thus, the simultaneous design and optimization of water desalination process and energy generation process is significant. In this paper, a novel superstructure of water desalination and energy generation system is proposed. Thermal membrane distillation unit is applied for water desalination together with reverse osmosis unit. A mathematical model is formulated for the thermodynamic analysis and optimization of the novel system. Two objective functions are used to evaluate the design scheme. A case study is elaborated to test the proposed system and developed model.

Design of Chemical Water Auto-control System in Power Plant Based on PLC

To effectively process the chemical waste water in power plant, a set of control system based on PLC upgrading and reform for chemical water is designed in this paper. In the process of treating chemical water, there are many operating procedures, complex technology and scattered positions and many pieces of equipment. With remote I/O control thought in this paper, the hot-standby series of PLC of Schneider is used as lower computer to form a set of chemical water treatment system. The subsystem monitoring screens are concentrated in one central control room to achieve remote monitoring and local/remote control on the whole chemical water system. In reform process, aiming at the regeneration link of chemical water desalination process in power plant, a prioritization scheme of single closed-loop control is put forward and simulated in MATLAB. In simulation result, the concentration of Na+ on cation bed is finally maintained to be 8.3µg/L; electric conductivity of water on anion bed is finally maintained to be 0.5µS/cm. This completely meets the standards of water discharge. In conclusion, the chemical water auto-control system based on PLC can not only achieve real-time detection but also raise the work efficiency of power plant. It has certain reference value to further reform on power plant.

Exergy Analysis of the Optimized MSFD Type of Brackish Water Desalination Process

This paper presents a detailed thermodynamical exergy analysis of an optimized MSF distillation plant based on the latest published thermodynamics properties of water and seawater software of the Massachusetts Institute of Technology by using design and optimized plant operation data. Exergy flow rates are evaluated throughout the plant and the exergy flow diagram is prepared in both cases. The rates of exergy destruction and their percentages are indicated on the diagram so that the locations of each exergy destruction can easily be identified. The study concludes that as a result of an optimization, making the MSFD unit once-through cooling system to recirculating type by using cooling tower system, the unit's exergy destruction pattern changes meaningfully. Besides, in the three exist thermal desalination plants up to 53 percent of feed water, i.e.; 667 m3/h and the same amount of reject water can be conserved. Though, with this modification, the unit steam consumption has been increased up to 13 ton/h, about 50 percent of design. Moreover, the detail of the study showed that the exergy destruction can be reduced more than 39% in the pumps, and 30% in blowdown and around 29% in distillate streams. For brine heater, an enhance as small as 0.37% is also achieved. In the other hand, the rate of destruction of exergy increased around 25% in the cooling process and above 5% in the evaporators.

Optimization of resin wafer electrodeionization for brackish water desalination

Abstract Resin wafer electrodeionization is an energy-efficient technology for brackish water desalination without the use of harmful chemicals. In this study, the performance of resin wafer electrodeionization under different applied voltages and feed flow rates was measured for a feed salt concentration of 3.0 g L−1. The results indicated that a salt removal efficiency of 94% could be achieved. In addition, the removal kinetics of NaCl from the brackish water was studied via a first-order kinetic model. The maximum kinetic rate constant was found to be 0.091 min−1 at a cell voltage of 2.53 V. The kinetic rate constants varied with the applied voltage and feed flow rate to the 1.52 and 0.33 power respectively. Furthermore, the productivity and energy consumption were balanced by using the response surface methodology. The optimized operating conditions should be set at an applied voltage of 2.28 V per cell pair with a feed flow rate of 810 mL min−1, corresponding to a productivity of 55.5 L h−1 m−2 at an energy consumption of 0.66 kWh m−3. Compared with other water desalination processes, resin wafer electrodeionization can offer relatively a higher energy-efficient performance for the brackish water desalination.