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Abstract In a conventional HDH system, a constant feed of seawater is required to run the system. As a result of extracting freshwater from the saline water, it is rejected at higher salinity, thus it cannot be recirculated as a feed again. The aim of this study is to come up with a zero-brine discharge system that eliminates the continuous need for the supply of source and sink in the conventional system. Based on the fact that earth's atmosphere holds a vast amount of water that can be considered as a reliable freshwater resource, especially in coastal areas. A water-from-air system is proposed in this study. The proposed system configuration comprises of two parts, a basic HDH system that uses a liquid desiccant solution instead of saline water and a desiccant-based air dryer. The liquid desiccant leaves the HDH part at a higher concentration due to the extraction of freshwater. It then enters the air dryer where it is diluted by absorbing water vapor from the ambient air. This diluted desiccant is directed to the HDH part to close the desiccant loop. In this study, Lithium chloride is used as the working fluid of the proposed system. Mathematical modeling of heat and mass transfer processes between the air and desiccant in the humidifier and dehumidifier is developed to predict the performance of the desalination system. The proposed system produces about 8 kg of freshwater per hour. Highlights • The objective is to eliminate the supply of source and sink reservoir in an HDH system. • The proposed system consists of an HDH system that uses liquid desiccant solution and an air dryer. • The system consists of two loops, one for the desiccant solution and other for the HDH system. • A mathematical model for the air and desiccant in the humidifier and dehumidifier is developed. • The proposed system produces 8 kg of fresh water per hour. [ABSTRACT FROM AUTHOR]

Abstract Due in part to increased water demand and uncertainty around the availability of existing freshwater resources, there is interest in expanding the use of seawater desalination in the U.S. In order for greater adoption to occur, existing barriers need to be mitigated. One of these barriers is the energy consumption of seawater desalination. This paper reviews the existing energy requirements for membrane and thermal-based seawater desalination systems to produce potable water. Through literature review, it identifies the commercially-available option with the lowest energy intensity and the thermodynamic minimum energy requirement for each unit operation of the system. The paper then estimates the energy requirements to expand seawater desalination capacity to meet the potable water needs of water-stressed regions in the U.S. The results show that supplying 10% of the potable water demand for these regions located within 250 miles of a coastline using the lowest energy-intensity seawater desalination system commercially available would require <0.1% of 2018 U.S. electricity consumption. This increases to approximately 0.5% if all public water for these same regions is supplied via desalinated seawater. These estimates of the energy implications of broader adoption provide an initial comparison to current U.S. electricity consumption. Highlights • The energy intensity of seawater desalination systems is reviewed. • The energy for greater adoption of seawater desalination in the U.S. is projected. • A comparison is made to current overall U.S. electric consumption. [ABSTRACT FROM AUTHOR]

Abstract Microbial desalination cells (MDCs) are known among the bioelectrochemical systems for their green and cost-effective application in salt removal. However, the low efficiency of desalination compared to other chemical and membrane-based methods still holding this technology in laboratory and requiring further research and development (R&D) to establish actual plants. This study focused on integrating different applicable functions in one setup to promote applying MDCs in actual scale. In this research, the behavior of the MDC upon applying different salt concentrations in the desalination chamber was studied. Moreover, salt, sulphate and organic matter removal in acetate and sulphate-fed MDCs (A.MDC and S.MDC) were investigated. 10, 20 and 35 g/l of salt were successfully removed by using MDC technology. Sulphate removal of 72% was achieved within the S.MDC setup while similar current productions were observed in both A.MDC and S.MDC. Higher COD removal (88%) was recorded in S.MDC compared to 65% in A.MDC. Furthermore, the microbial communities were characterized and Rubrivivax was identified as the dominant genus in A.MDC while Desulfobulbus , Geobacter and Desulfovibrio were the most abundant genera in S.MDC setup. Highlights • Different concentrations of saline water were successfully removed in MDC. • Two types of acetate and sulphate-fed MDCs were enriched. • High salt and sulphate removal were simultaneously achieved in MDC. • Microbial morphology and community of two MDC types were discussed. [ABSTRACT FROM AUTHOR]

Electrodialysis desalination (ED) is an efficient process to desalinate brackish water and to minimize brine salinities to the level of seawater salinity. From the many models reported in the literature, some are simple but have a limited accuracy while others are complicated with a good accuracy. In this context, we explore the improvement of a fundamentally ‘lumped’ model by considering the voltage drop at the interfaces between membranes and solutions (which is the so-called Donnan potential) while conserving the model simplicity. The present model is developed by accounting for an electrical resistance of the Donnan potential in the total cell pair resistance. The results are presented in terms of total membrane area, flow path length, number of stacks and specific energy consumption. The results show that the improvement resulting from involving the Donnan potential was substantial for a high difference between the feed and product salinities as well as for low salinities (<500 ppm) of the product water and low flow velocities (<0.05 m/s). In general, the inclusion of Donnan potential improved the results from 4.4% up to 39.2% based on the studied cases. [ABSTRACT FROM AUTHOR]

Among non-conventional water resources, desalination (from seawater or brackish aquifers) has emerged as a feasible option to deal with water shortage in arid and semi-arid areas. At the University of Alicante (UA, SE Spain), water availability is lacking and groundwater quality is poor. To ensure water availability, the UA built a small reverse osmose (RO) desalination plant (450 m 3 /day) to water the green areas and an urban park on the campus. The costs of a small private desalination plant, landscape irrigation, and the full cost of water, were assessed. This assessment considered the benefits made by new green areas existing in an urban space and citizens’ willingness to pay (WTP) for its preservation based on the contingent valuation method (CVM). The results indicated that the final desalinated brackish water cost was 0.29 €/m 3 and, according to the WTP results, the value that derived from the social benefits provided by the leisure area was 0.51 €/m 3 , being the final cost of water 0.22 €/m 3 . Consequently, the use of brackish water for irrigation has a high social value that should be considered when evaluating desalination-related projects. [ABSTRACT FROM AUTHOR]

The inhibition impact of aromatic nitro compounds on the corrosion of heat exchanger tubing material (titanium tubes) in MSF desalination plants in acid cleaning solution (1.0 M sulfuric acid) was explored. Corroborative results between chemical and electrochemical (EIS) methods have been reported. FTIR and SEM analysis were further used to characterize the morphology and the nature of the film adsorbed on the titanium surface. The study informed that the maximum corrosion rate of titanium (0.260 mg cm −2  h −1 ) was obtained in 1.0 M sulfuric acid at 298 K. Aromatic nitro compounds act as effective corrosion inhibitors for titanium in acid cleaning solution. The efficiency of these compounds boosts with concentration and diminishes with temperature. The aromatic nitro compounds exhibit a maximum inhibition efficiency of 73.0% (NI), 82.6% (NII) and 94.6% (NIII) at 600 ppm. They form a good protective layer on titanium surface through their adsorption. The adsorption of aromatic nitro compounds on titanium surface obeys Langmuir model. The performance of these compounds decreases in sequence: (NI) < (NII) < (NIII). [ABSTRACT FROM AUTHOR]

Improving the concentration ratio to reduce the emission of concentrated brine is required in some desalination plants. However, scaling problem will be aggravated with higher concentration. In this study, scaling tendency was analyzed according to two indexes including the Langelier Saturation Index and the Ryznar Stability Index. Four kinds of inhibitors were analyzed. Their inhibition performance under the condition of high concentration ratio in MED system was studied by both static jar tests and experiments on a small-scale falling film evaporation apparatus. Results indicate that severe scaling problems would occur when high concentration ratio encounters high temperature. Under the experimental condition, for which the temperature was 70 °C and the concentration ratio was 2.5, the alkaline scales were calcium carbonate. No magnesium hydroxide was formed. Calcium sulfate began to appear and increase when the concentration ratio exceeded 2. All inhibitors showed controlling effect on scale formation. Inhibitor A with its main constituents of HPAA and polymaleic acid showed the best inhibition performance. Better inhibition performance was achieved with higher inhibitor dosage, but no obvious improvement was observed when inhibitor dosage exceeded 5.5 ppm. The present study is helpful to the MED system under the condition of high concentration ratio. [ABSTRACT FROM AUTHOR]

The paper analyses the extrapolation of the results obtained in a pilot plant to a full-scale seawater desalination plant. A technological system was implemented in the pre-treatment line of Las Palmas III seawater reverse osmosis (RO) desalination plant with a capacity of 36,000 m 3 /d. This system is aimed to control membrane fouling. It consists in the non-dosing of sodium hypochlorite or another biocide to seawater in order to minimize RO membrane biofouling. The pH regulation at 6.5 controls the scaling and the 12.5 ppm dosage of FeCl 3 as a coagulant maximizes the coagulation efficiency of colloidal particles and controls the fouling process. [ABSTRACT FROM AUTHOR]

Ring opening reaction was used to prepare novel anionic surfactant as CaSO 4 .2H 2 O scale and mild steel (MS) corrosion inhibitor. The prepared surfactant was designed as Hexa-anionic surfactant, and named; Sodium(2Z,16Z)-8,11-bis((Z)-3-carboxylatoacryloyl)-5,14-bis(2-((4dodecylphenyl)sulfonamido)ethyl)-4,15-dioxo-5,8,11,14-tetraazaoctadeca-2,16-dienedioate. The Hexa-anionic surfactant was characterized by FTIR, and 1 HNMR. Platinum ring method was used to study surface active properties of the investigated surfactant. The anti-scale property of Hexa-anionic surfactant was evaluated according to a static test method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), and X-ray diffraction (XRD) were used to examine CaSO 4 ·2H 2 O crystal morphology. The high anti-scale performance of Hexa-anionic surfactant was related to its chelating, adsorption, and dispersion abilities. The scale inhibition ( SI %) reached the maximum 100% at concentration 7 ppm. Also, the inhibition performance of the insight surfactant for MS corrosion in synthetic water was tested by electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques, accompanied with surface analysis techniques. The obtained results indicated a good corrosion mitigation action of the investigated surfactant. SEM, and EDX show the formation of Hexa-anionic surfactant's adsorbed layer on the MS surface. The adsorption of Hexa-anionic surfactant at MS followed Langmuir adsorption isotherm. Quantum calculations confirmed the experimental data. [ABSTRACT FROM AUTHOR]

Based on the internal relationship of thermodynamic and structure parameters of the low-temperature multi-effect evaporation (LT-MEE) desalination plant, calculation of the temperature difference distribution in a typical horizontal-tube falling film evaporator was carried out. Results show that the reduction of effective temperature difference caused by various thermodynamic losses occupies a large proportion of the apparent temperature difference in horizontal-tube falling film evaporator. The distribution of effective heat transfer temperature difference is extremely un-uniform in tube bundle. Under some conditions, the local effective temperature difference in the evaporator could be zero, and reverse heat transfer might even appear. Through the analysis of the thermodynamic losses in a desalination plant, the heat transfer critical point and the effective heat transfer critical point are proposed for better guiding the thermal design of multi-effect evaporation desalination plant. [ABSTRACT FROM AUTHOR]

Electrodialysis desalination plants, for brackish water, are designed based on different parameters such as feed concentration, current density, and stack construction. Among the various model assumptions, the constancy of the equivalent conductivity of the diluate and concentrate streams is considered a prominent one. In this paper, this assumption is relaxed at different levels and closed-form solutions are obtained to ascertain its effects. It is shown that previously published results can be replicated. Also, a comparison between the lumped and staged model shows that using the inlet flow rate in the lumped model instead of the product flow rate provides more accurate results. Further analysis reveals a non-dimensional number, termed the electrodialytic Biot number, which is the ratio of the total to exit concentration based average cell pair volume resistance. It was found to be physically equivalent to the number of stacks. This provided a clear criterion as to when the lumped model should be used. Specifically, as long as the electrodialytic Biot number is (less than or) equal to 1, the lumped model should be used, otherwise the staged model is a more appropriate choice. It also provides direction for future research. A design chart is also developed to facilitate the calculation procedure. [ABSTRACT FROM AUTHOR]

Fouled BWRO membrane elements from a full-scale desalination plant were characterized by collecting performance data and through a membrane autopsy in order to identify the fouling characteristics and behavior associated with feed water inorganic composition and operating conditions. This is the first time that membranes of a desalination plant have been autopsied with a data collection along 11 years of operation. The investigated membrane elements were taken after 11 years of operation. The BWRO desalination plant had a production capacity of 15 m 3 d - 1 with a recovery of 60% approximately. It was fed from a groundwater well having cartridge filters and antiscalant dosing as a pre-treatment. It is a two stages desalination plant with the BW30-400 membrane element. Chemical and structural characterization was performed by visual inspection, qualitative analysis test and by scanning electron microscopy with energy dispersive X-ray (SEM-EDX). The fouling layer consisted of a biofilm detected in the first elements of the RO system. Biofilm comprising diatoms on all membrane elements were found. Inorganic foulants mainly consisted of calcium carbonate and aluminosilicates. The results highlight that it is possible to preserve BWRO membrane elements in service for up to 11 years using a correct conventional pretreatment with this kind of foulants. However, the membrane resistant increased more than twice over the operating period. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a promising desalination technology for treatment of high salinity shale gas produced water. Techno-economic assessment (TEA) is necessary for evaluating the economic feasibility of MD for produced water treatment as compared to other shale gas produced water management strategies. A detailed TEA for a hypothetical 0.5 million gallons per day (MGD) direct contact MD (DCMD) that concentrates produced water from 10% (100,000 mg/L) Total Dissolved Solids (TDS) to 30% salinity is presented in this study. The model is developed based on a combination of experimental results, ASPEN Plus process model, best available engineering knowledge, and cost estimates. Analysis reveals that thermal energy cost for MD operation contributes the most to total cost of treating produced water in an MD plant. Additionally, the results of sensitivity analysis reveal that feed TDS level and thermal energy price have a significant impact on total cost of treating produced water. We also explore the implications of utilizing waste heat on the economics of the MD technology for produced water treatment. The results reveal that the total cost of treating produced water using MD is $5.70/m 3 feed which decreases significantly to $0.74/m 3 feed when MD is integrated with a source of waste heat. [ABSTRACT FROM AUTHOR]

For the purpose of managing the operation of a small-scale prototype of a sea water reverse osmosis desalination plant installed on the island of Gran Canaria (Spain) and enabling it to function with fluctuating power input, artificial neural network (ANN) models were incorporated into its control system. The ANN models were developed to generate feed flow and operating pressure setpoints (with the restriction of having to maintain the permeate recovery rate within a certain range) after taking into account not only the available electrical power but also the temperature and conductivity of the feedwater. It is concluded that the ANN models that were used after training and validation were able to successfully manage the random and widely varying available electrical power. The statistical hypothesis testing that was also performed showed no significant statistical differences (at 5% level) between the errors (both MAE and MAPE) committed when adapting power consumption of the plant to the available electrical power in the various operational tests using different feedwater characteristics. [ABSTRACT FROM AUTHOR]

In recent years, natural gas (NG)- and liquefied natural gas (LNG)-based power generation options have been considered as a potential alternative to grid electricity at desalination plants to reliably meet the increasing energy demand and reduce the associated environmental impacts. This study comparatively evaluated on a life cycle basis the economic and environmental cost-benefits of LNG/NG for self-generation of power with those of the grid electricity supply. The analysis conducted showed that for desalination plant sizes of 75–570 ML/day, the LNG-based onsite power generation option is 20–30% more economical than the alternative connection to the grid. However, the life cycle cost (LCC) of the LNG-based onsite power generation system is from 43% to up to 86% higher than the NG-based counterpart for desalination plant sizes that increase progressively from 10 to 570 ML/day. A sensitivity analysis conducted on two conceptual mid-range capacity seawater desalination plants showed that variations in the electric tariff rate, fuel cost, plant efficiency, and economic parameters affect the LCC of various power supply options. The study also showed that when the grid electricity with a cleaner mix (i.e., low emission factor) is available, this option results in lower GHG emissions than the LNG/NG power source alternatives. [ABSTRACT FROM AUTHOR]

In a conventional economic analysis, the availability of system is considered as a constant value. However, some factors such as increasing components' failure rate due to degradation, reducing failure rates by replacement or repairing, and stops in operation because of overhauls change the availability during the lifetime of a system. Furthermore, due to overhauls and degradation, maintenance costs are not identical in different years. This paper presents a new approach for economic analysis of thermal systems in which change in the availability of system during its lifetime is considered. A combined gas turbine cycle and desalination is studied. The instantaneous availability of system is calculated using state space method with time-varying failure rates and considering overhauls. Then, the average availability of producing electricity and fresh water in each year of lifetime is applied to the economic analysis. In addition, maintenance costs are calculated according to the overhauls and the number of components repairs in each year. Finally, some economic indicators are compared in two cases of variable and constant availability, using the life cycle cost analysis method. Considering time-varying availability, increase in payback period is observed by 9 months and reduction in net present value by about $18 million. [ABSTRACT FROM AUTHOR]

Exergetic efficiency characterizes the performance of a system or a system component from the second-law of Thermodynamics viewpoint. Although this parameter can be used in the comparison of the operation of similar components working under similar conditions, there are not many articles in the literature dealing with this purpose. In this paper, a desalination plant located in Gran Canaria (Canary Islands, Spain) is considered. Different configurations are possible in the ten reverse osmosis production lines of the plant, depending on the procedure used for the energy recovery, the number of reverse osmosis stages, the technologies applied to the intake and filtration processes, or the components involved in feed water pressurization. Using real data, the exergetic efficiency is assessed as a performance evaluation tool. Through the comparison of the exergetic efficiency of similar devices, though different production lines, the components with operation defects that should be repaired are identified: the most inefficient pelton turbines, intake pumps, high pressure pumps, booster pumps, reverse osmosis membrane modules, and pressure exchanger modules. This way, exergetic efficiency can be successfully used to control and to improve the operation of the plant. [ABSTRACT FROM AUTHOR]

The current study is focused on carrying out exergo-economic analysis of a seawater reverse osmosis (SWRO) desalination plant. The main objective is to compare the performance as well as the product cost of an existing SWRO plant, including post-treatment and distribution sections, for four different retrofit options made by coupling high-efficiency pressure exchangers (PXs) in place of conventional energy recovery turbines. For this purpose, first- and second-law analysis is carried out to estimate the energy requirements and second-law efficiency for each retrofit option. Finally, the product cost is compared by performing an exergo-economic analysis using appropriate seawater properties for the calculations. The analysis revealed that, by introducing a PX, the specific energy consumption (SEC) can be reduced by about 24%; thus, increasing the second-law efficiency. Besides this, it is also demonstrated that the addition of post-treatment and distribution sections enhances the product cost by almost 20%. Furthermore, the study suggested that using a booster pump with a PX (as used in retrofit # 3) is best suited for enhancing the plant capacity compared to retrofit # 4 in which a PX is used in place of the pump. It has the least product water cost among all the options discussed. [ABSTRACT FROM AUTHOR]

Extreme flash evaporation occurs when superheated liquid is sprayed into a low pressure zone. This method has high potential to improve the performance of thermally-driven desalination plants. To enable a more in-depth understanding on flash evaporation of a superheated feed water spray, a theoretical model has been developed with key considerations given to droplet motion and droplet size distribution. The model has been validated against 14 experimental data sets from literature sources to within 12% discrepancy. This model is capable of accurately predicting the water productivity and thermal efficiency of existing spray evaporator under specific operating conditions. Employing this model, the effect of several design parameters on system performance was investigated. Key results revealed that smaller droplet enabled faster evaporation process while higher initial droplet velocity promoted water productivity. Thermal utilization marginally changes with the degree of superheat, which renders a quick design calculation of the brine temperature without the need for iterations. [ABSTRACT FROM AUTHOR]

This study focuses on determining exergy destruction in a MSF Desalination plant located in Yanbu Saudi Arabia. A non-iterative code in MATLAB is developed to perform mass, energy, and exergy balances around the plant at normal load of distillate production (~ 159 kg/s) at 22.9 °C in the winter and at peak load (~ 200 kg/s) at 35.2 °C in the summer. Exergy flowrates are calculated and exergy destruction around each of the equipment is estimated. An exergy diagram is prepared to indicate equipment with highest exergy destruction. As expected the major exergy destruction occurs at the Heat Recovery Section (74.9%). The simulation results indicate that as the number of stages increase from 25 to 31 the percent exergy destruction drops from 74.9% to 69.2%. The second law efficiency of the plant is 3.22% and 2.84% at normal and peak load respectively. This efficiency is quite low and several measures can be done to improve it by decreasing inlet exergy to the plant and controlling exergy losses during process operation. Two variations in MSF designs i.e., Once Through (MSF-OT) and Brine Mixing (MSF-M) are considered. It is found that the design of MSF-M is a viable option to minimize exergy losses. [ABSTRACT FROM AUTHOR]

Extensive pilot plant experimental studies for a period of one year were carried out to study the impact of climatic conditions on the operational performance of an innovative Fresnel solar collecting system. The solar measurements revealed that the total yearly Direct Normal Irradiance (DNI) on the tested site amounts to 1132 kWh/m 2 . The thermal collector efficiency, which depends on climatic conditions such as solar insolation, ambient temperature, receiver temperature as well as heat losses, ranges from 60% to 80%. The cost effectiveness when the tested Fresnel solar collection system with solar multiple of 1.0 (limited to day time operation) is combined with a commercial thermal desalination plant is compared with one completely run by fossil fuel. The breakeven fuel cost whereby the levelized cost of water of the two cases will be equal is yielded at a fuel cost of $92/bbl. When the tested Fresnel solar collection system is run at a location with a relatively high annual DNI level (1937 kWh/m 2 ), the fuel breakeven cost falls to $52/bbl. This study also revealed that combining a Fresnel solar collection system with an MED thermal desalination plant under specific climatic conditions is considered more cost effective when operated without thermal energy storage. [ABSTRACT FROM AUTHOR]

Solar energy is turning to one of the important types of clean energies, due to its availability, and its potential for wide range of applications. In this work, a new passive solar desalination system is introduced, which benefits from excellences of twin-glass evacuated tube collectors. For the first time, the evacuated tube collector is not only used as the solar thermal collector, but also as a basin to heat the water. Hence, the thermal resistance between the collector and basin is virtually eliminated. Results show a considerable increase in the rate of desalinated water production and the maximum production reaches up to 0.83 kg/(m 2 ·h). It was observed that the maximum rate of the production occurs when the tube is in inclination angle of 35°, and filled 80% with water. Moreover, it is seen that filling the tube with a stainless steel wool can enhance the production rate up to 1.01 kg/(m 2 ·h). It was observed that optimum inclination angle is 35°, which is the latitude of location of the experiments. Moreover, a theoretical model is presented in order to evaluate the system's efficiency in quasi-steady state conditions. [ABSTRACT FROM AUTHOR]

Discharge from the desalination plants of Kuwait returns brines of high salinity to the Gulf that contain other contaminants, such as chlorine or chromium, impacting the environment of the coastal region. Conversely, wastewater discharges to the Gulf have low salinity but may drive eutrophication of coastal waters. Pressure retarded osmosis (PRO) is a promising source of renewable energy and an emerging membrane-based technology for recovering energy from concentration differences between water streams. The proposed work examines the feasibility of using PRO to generate energy from wastewater and desalination plants in Kuwait by calculating the power density using a PRO zero-dimensional model. The model accounts for concentration polarization (CP) and salt leakage (B ′ ) effects to produce realistic results. The effects of CP and (B ′ )on the power density at varying applied pressures and varying concentration differences between the feed and draw solutions are studied. Case studies on the potential re-use of treated wastewater effluent (TWE) and brine reject streams from three wastewater treatment plants (WWTPs) in Kuwait are discussed and compared to determine the maximum power generated from each of the WWTPs. The power densities generated from wastewater treatment (WWT) plants in Al-Jahra city, Um Al-Haiman city and Al-Riqqa were studied. The power density from Al-Haiman WWTP (18.73 W/m 2 ) is the highest compared to those of the other two WWTPs. The limits of the zero-dimensional model are also presented in this study. The PRO power density (W) was studied as a function of hydraulic pressure (ΔP) at different feed and draw solution concentrations. At higher draw solution concentrations (85 g/L NaCl), the power densities were higher. This increase in power density values was attributed to the higher driving forces acting in the system. Concentration polarization (CP) and salt leakage (B ′ ) reduce the driving forces across the membrane. The power density values (W) were smallest in the presence of both CP and(B ′ ). The effects of CP and (B ′ ) vary depending on the concentrations of the draw and feed solutions. [ABSTRACT FROM AUTHOR]

Hydraulic turbocharger is a common energy recovery device used in reverse osmosis water desalination plants to recover the stored energy in brine. Also, it can be used to control the pressure variation due to the change of plant operating conditions. The aim of the current work is to apply the computational fluid dynamics (CFD) to investigate the balance between the hydraulic turbocharger turbine and pump sections. The effect of changing the rotor speed and the effect of auxiliary line size and valve opening on the performance of the hydraulic turbocharger are also investigated. In addition, the effect of these changes on the plant specific energy consumption (SEC) is discussed. The results of the current work present the variation of the hydraulic turbocharger performance with the rotor speed. It also shows that increasing the turbine auxiliary line diameter reduces the turbine inlet pressure. The CFD results show that opening the auxiliary line reduces the turbine inlet pressure which reduces the rotor speed and the pump boosting pressure. [ABSTRACT FROM AUTHOR]

Fouling and scaling is one of the major challenges in membrane distillation process. This study investigates the utilizing of thermal rejected brine produced from multi-stage flash distillation (MSF) to minimize fouling and scaling on membranes in direct contact membrane distillation (DCMD) settings. The effect of operating parameters on permeate flux and the extent of scaling during long time operation was considered and compared when real seawater and reject thermal brine were used. The deposit morphology of scaling was observed using different analytical methods, including scanning electron microscopy and contact angle measurement. Thermal brine showed enhanced performance in terms of flux and scaling compared to seawater. It was found that flux is reduced by 8% compared to 12–20% when the feed to the DCMD was brine was used as compared to seawater. In addition, thermal brine feed showed better anti-fouling behavior compared to the fresh seawater which contains different organic and inorganic contaminants. Furthermore, utilizing waste heat contained in the thermal brine to raise the temperature of the feed was advantageous in increasing the energy efficiency of DCMD process. [ABSTRACT FROM AUTHOR]

This work presents the results of the techno-economic analysis of a proposed 100 m 3 day − 1 desalination plant based on existing plate and frame MD technology coupled with a static solar collector field as main heat supply. The experimental results of one commercial and two pre-commercial MD modules characterized previously under real operational conditions were used. Three different cost-effective solar technologies (evacuated tube collectors (ETCs), flat plate collectors (FPCs) and compound parabolic collectors (CPCs)) were considered for the analysis and the results were compared to a fossil source. For the dimensioning of the solar field, meteorological data from Almeria (South-Spain) where the experimental campaign took place were selected. A thorough economical assessment was performed to calculate the cost of water (WPC) for the different considered scenarios. The best results obtained show a WPC in the range of 10–11.30 € m − 3 for the combination of the most efficient MD module and solar collector. The fossil-driven option showed a similar (i.e. 7.19 € m − 3 ) yet lower WPC. Although the MD technology here analyzed is in an early stage of development, the results obtained suggest solar MD can be already competitive with PV-RO and PV-ER according to reported data for similar capacities (~ 100 m 3 day − 1 ). [ABSTRACT FROM AUTHOR]

In this paper, authors breakdown the specific energy consumption for seawater and brackish water desalination in an attempt to quantify the value of high permeability membranes on specific energy consumption for desalination. The trends from the analysis presented in this paper show that in both seawater and brackish desalination we are approaching thermodynamic limitations. The Gibbs free energy of mixing accounts for almost half of the specific energy consumption for seawater desalination and for brackish water desalination system losses and frictional losses account for major share of energy consumption. It is also shown that in both seawater and brackish water desalination, just high permeability membranes will not give substantial returns. Spacers, membranes, module designs and system are all areas that need to improve to make any significant enhancement in energy efficiency of reverse osmosis desalination. [ABSTRACT FROM AUTHOR]

A new RO system for large-scaled SWRO plant has been developed in the project named “Mega-ton Water System” with private–public cooperation in Japan. The characteristic of the newly developed RO system to increase the recovery rate is to use the short vessel that contains 2–4 elements for the first stage, and to use relatively long vessel for the second stage after inter-booster pump in order to reduce the pressure and the flux of the lead element The new RO system used by low pressure new SWRO element studied by this project is capable of the high recovery rate (under 65%) and allows the scale of the intake and pretreatment equipment to reduce compared to conventional system. Considering also to new isobaric ERD that has been developed in this project, the energy consumption was estimated and compared the results with that of conventional system. It is suggested that the reduction of energy consumption is to be about 20% compared with a conventional system. [ABSTRACT FROM AUTHOR]

Seawater desalination is an increasingly common means to meet the demand for freshwater. Resulting wastewater discharges can, however, impact biota of the surrounding environment. Concern exists that interactive effects specific to the outputs of each desalination plant may result in unique impacts difficult to predict by studying existing plants or assessing the effects of individual chemicals found in waste streams. Given this, we highlight an alternative approach to assess potential toxicity of desalination outfalls. Specifically, we review three recent case studies from Australia in which simulated whole effluents were used in toxicity assessments before desalination plants were constructed. This approach enabled potential toxic effects of wastewater to be considered before the plants became operational and, in one case, even facilitated consideration of potential effects of different treatment processes and suppliers. As in many whole effluent toxicity assessments, the time required for testing and restricted range of species considered were limitations. Given the benefits of this method, however, the use of simulated whole effluents is a development that could facilitate an improved capacity to forecast impacts of proposed desalination plants. [ABSTRACT FROM AUTHOR]

Conventional processes involved in water treatment, either in water treatment plants or reverse osmosis desalination plants, have encountered several obstacles that have severely affected their performances and efficiencies. Pollution of natural water resources, increasing demand and overuse of clean water have all put critical stress on currently available conventional water treatment/desalination plants. Due to these problems, integrated/hybrid membrane processes have attracted much interest. An integrated/hybrid membrane system is a process which combines a membrane filtration unit (microfiltration/ultrafiltration/nanofiltration) with other processes such as coagulation, adsorption and ion exchange. Alternatively, it can be a combination of different membranes in the same system with a conventional process. The purpose of this paper is to review the applicability of integrated/hybrid membrane systems in water treatment plants and reverse osmosis desalination plants. The literature shows that many benefits and marked improvements could be achieved with integrated/hybrid membrane processes, such as enhanced quality of the water produced, energy savings, environmental friendliness, and reductions in the capital and operating costs of the plants. The implications of the integrated membrane system prove that it has huge potential to be widely applied and can lead to a breakthrough in solving the problem of water scarcity. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the formation and the behavior of halogenated byproducts (regulated THMs and HAAs, as well as nitrogenous, brominated and iodinated DBPs including the emerging iodo-THMs) along the treatment train of full-scale desalination plants. One thermal multi-stage flash distillation (MSF) plant and two reverse osmosis (RO) plants located on the Red Sea coast of Saudi Arabia. DBPs formed during the prechlorination step were efficiently removed along the treatment processes (MSF or RO). Desalination plants fed with good seawater quality and using intermittent chlorine injection did not show high DBP formation and discharge. One RO plant with a lower raw water quality and using continuous chlorination at the intake formed more DBPs. In this plant, some non-regulated DBPs (e.g., dibromoacetonitrile and iodo-THMs) reached the product water in low concentrations (< 1.5 μg/L). Regulated THMs and HAAs were far below their maximum contamination levels set by the US Environmental Protection Agency. Substantial amounts of DBPs are disposed to the sea; low concentrations of DBPs were indeed detected in the water on shore of the desalination plants. [ABSTRACT FROM AUTHOR]

Energy and cost effective pretreatment of seawater is essential for any desalination plant to convert seawater into clean water successfully. This study shows a way to pretreat seawater without excessive input of electrical energy or high pressure; it uses a bioelectrochemical cell with two chambers, divided by an anion exchange membrane (AEM). When bacteria attached on the anode produce current using organic matter as a source of fuel, hydroxyl ions can be generated in the cathode chamber, which can increase the alkalinity of the catholyte (seawater); scale-forming ions such as Ca 2 + and Mg 2 + in seawater can be removed by forming precipitates in the cathode chamber. Our results show that 84% of Ca 2 + and 37% of Mg 2 + in seawater can be effectively removed while treating wastewater in the anode chamber. These results indicate a new method to pretreat seawater without external energy input since the cell accomplishes selective removal of divalent cations using an electrochemical cathode reaction. This study provides evidence that this new method can be a viable option for membrane based seawater pretreatment and desalination processes to significantly mitigate scale problems of membranes. [ABSTRACT FROM AUTHOR]

Abstract: As of today, the Multi Stage Flash (MSF) evaporator capacity has reached to 20 MIGD of desalinated water using traditional brine recycle and cross tube bundle configuration. However, on the way of scaling-up evaporator unit production beyond 20 MIGD, there are some technical barriers and economical aspects that need to be considered. This work presents a techno-economic comparison between long tube (LT) and cross tube (CT) bundles of MSF evaporator for a unit production of equal and greater than 20 MIGD. Process calculations showed that the heat transfer surface area of MSF-LT is 25% lower than that of MSF-CT. This is mainly owing to an enhancement in heat transfer process. The pumping power in LT evaporator decreases by 8% due to the lower friction loss. For a large size project of 100 MIGD, the saving in the total capital investment of MSF-LT evaporator is 15% lower than that of MSF-CT. The operating cost is the same. A novel layout of MSF-LT configuration is proposed in which the stages are arranged in triple decks to reduce the footprint up to 51%. The novel configuration enables a significant reduction in the water box size and numbers. [Copyright &y& Elsevier]

Abstract: This paper presents a hybrid solar desalination system consisting of a humidification–dehumidification unit and single stage flashing evaporation unit. The hybrid solar desalination system was studied numerically. The heat and mass transfer and flow field are modeled theoretically in two dimensions using the finite difference scheme. For different operating and weather conditions, the fresh water productivity and salinity are computed. The model is developed to investigate the steady-state behavior of each component of the system. Six main parameters that have influence on the system productivity are studied; feed water mass flow rate of SSF unit, feed water mass flow rate of HDH unit, cooling water mass flow rate of SSF unit, cooling water mass flow rate of HDH unit, air mass flow rate and inlet cooling water temperature. The results show that, the studied hybrid desalination system gives a significant operational compatibility between the air humidification–dehumidification method and flash evaporation desalination with daily water production up to 11.14kg/m2/day. The efficiency of the system is measured by the gained output ratio (GOR) with day time. The gained output ratio (GOR) of the system reaches 4.5. The effect of the water and the air solar heaters collecting areas on the system productivity is measured. The trend of air solar heater collecting area variation showed a pronounced increase in the fresh water productivity than that of the water solar heater collecting area variation. [Copyright &y& Elsevier]

Abstract: The paper deals with the parametric simulation for design and optimization purposes of a heat integrated geothermal desalination plant for domestic use of fresh water, focusing on the appealing multi-effect distillation (MED) process to handle water shortage in remote locations with low-temperature geothermal potential. Several innovations are introduced in the simulation, such as a loop for the geothermal heat transfer, the use of desalinated water in the geothermal well, and the introduction of a heat integration train to preheat seawater. Heat integration helps manage oscillations in the plant operating conditions caused by inevitable seasonal climate variations, and the parametric simulation enables early reliable economic assessments on capital investment, and the forecast of practical benefits. Despite the generality of the proposed approach, for the sake of clarity and quantitative analyses, the study is contextualized to the water shortage in Isola di Pantelleria, and the plant layout is optimized accounting for the flexible water supply of popular tourist destinations. [Copyright &y& Elsevier]

Abstract: Lithium (Li) procurement is becoming a matter of importance worldwide. I propose a new method for recovering Li from seawater by electrodialysis, wherein Li selectively permeates from the anode side to the cathode side through an organic membrane impregnated with an ionic liquid (PP13-TFSI). Measurements of the ion concentration at the cathode side as a function of dialysis duration showed that the Li concentration increased to 5.94% after 2h with an applied electric voltage of 2V. Moreover, the other ions in the seawater did not permeate the membrane. With both ends of the impregnated membrane covered with a Nafion 324 overcoat to prevent outflow of the ionic liquid, the Li concentration increased to 22.2%. This new recovery method shows good energy efficiency and is easily scalable and thus is suitable for use in seawater desalination plants. [Copyright &y& Elsevier]

Abstract: This study proposes a systematic approach of analysis and optimization of the multi-effect distillation-thermal vapor compression (MED-TVC) desalination system. The effect of input variables, such as temperature difference, motive steam mass flow rate, and preheated feed water temperature was investigated using response surface methodology (RSM) and partial least squares (PLS) technique. Mathematical and economical models with exergy analysis were used for total annual cost (TAC), gain output ratio (GOR) and fresh water flow rate (Q). Multi-objective optimization (MOO) to minimize TAC and maximize GOR and Q was performed using a genetic algorithm (GA) based on an artificial neural network (ANN) model. Best Pareto optimal solution selected from the Pareto sets showed that the MED-TVC system with 6 effects is the best system among the systems with 3, 4, 5 and 6 effects, which has a minimum value of unit product cost (UPC) and maximum values of GOR and Q. The system with 6 effects under the optimum operation conditions can save 14%, 12.5%, 2% in cost and reduces the amount of steam used for the production of 1m3 of fresh water by 50%, 34% and 18% as compared to systems with 3, 4 and 5 effects, respectively. [Copyright &y& Elsevier]

Abstract: Membrane-based processes and thermal desalination plants are two alternatives to overcome the problem of fresh water supply by means of seawater desalination. In this work the combination of two types of desalination technologies, a reverse osmosis network (RON) and a forward-feed multi-effect distillation (FF-MED), in a hybrid plant is considered as a structural optimization problem. Deterministic mixed-integer non-linear programming techniques (MINLP) are used to rigorously optimize operational parameters and process structure simultaneously. A generalized superstructure for the hybrid desalination plant is constructed and conceptual design considerations are used to reduce its complexity. A mathematical model for the whole plant and an economical objective function are provided. The resulting model is highly nonlinear and non-convex. A stepwise optimization strategy is proposed, including a specialized initialization scheme to robustly compute good initial solutions with a minimum of user interaction. Results for various specifications illustrate the application of the proposed optimization model. The performance of the suggested method is compared to that obtained with the global solver BARON. [Copyright &y& Elsevier]

Abstract: This work examines the economic and environmental performance of seawater desalination plants that integrate reverse osmosis, Rankine cycles and solar collectors. The design of these facilities is formulated as a multi-objective mixed-integer nonlinear programming model (MINLP) that considers the simultaneous minimization of cost and environmental impact given a certain water demand to be fulfilled. The environmental performance is quantified in terms of contribution to global warming, which is holistically determined following life cycle assessment (LCA) principles. A case study that considers weather data of Tarragona (Spain) is used as benchmark to illustrate the capabilities of the approach presented. Using our rigorous modeling and optimization approach, we show that coupling seawater desalination with solar collectors can lead to significant environmental savings at a small increment in cost. Our systematic tool is aimed at guiding decision-makers towards the adoption of more sustainable technological alternatives for seawater desalination. [Copyright &y& Elsevier]

Abstract: Nuevo Canal de Cartagena (Spain) desalination plants discharge hypersaline effluent through a submarine outfall pipeline, creating a negatively buoyant brine jet. Many near-field mixing models are used in the prediction and management of brine discharges, but they have rarely been compared with field salinity measurements obtained directly inside the brine jet. Two divers obtained these field measurements and compared them with CORMIX1, CORJET, MEDVSA and UM3 mixing zone model predictions. In general, each model was quite conservative in its results, except UM3, whose prediction presented the best approximation to measured data. It is concluded that direct field measurements should be essential when testing the accuracy of current models or developing new near-field mixing models. [Copyright &y& Elsevier]

Abstract: The present study deals with the multi-objective optimization for designing a combined gas turbine and multi stage flash desalination plant. In optimization approach, the exergetic, economic and environmental aspects have been considered, simultaneously. In order to achieve the optimal design, Multi-objective genetic algorithm (MOGA) is applied as a suitable optimization technique. The thermoenvironomic objective function is obtained by integrating the environmental impacts and thermoeconomic objective. By applying the optimization approach, this objective function is minimized, whereas system exergy efficiency is maximized. Moreover, equipment reliability using the state-space and the continuous Markov method is incorporated in optimization results to improve the products'' cost values. The optimization results show that the cost of products and environmental cost impact are reduced by 13.4% and 53.4%, respectively, whereas a 14.8% increase happens in total exergy efficiency. Therefore, improvement in all objectives has been achieved using the optimization process, although the power and water productions have not changed much. Additionally, the sensitivity analysis shows the relationship between the fuel cost, pollution damage cost and the objective functions. [Copyright &y& Elsevier]

Abstract: In this paper, a new method for exergy analysis of humidification–dehumidification (HD) desalination systems is presented. It is based on the principle that there are exergy losses wherever the driving forces exist. A methodology was developed for investigating various parametric effects on exergy losses. The method involved developing a sink and source model as well as basic relations in the system. Results showed that the mass transfer phenomenon does not have any effect on the total exergy losses of the HD systems. Heater was the largest irreversibility resource. Flow rate of the Un-heated fluid and the maximum temperature of the system had key roles in the total exergy losses. An optimum point for the water-heated HD desalination system is also introduced. Finally, some comparisons are proposed between the water-heated and the air-heated HD desalination systems. [Copyright &y& Elsevier]

Abstract: Integrated power and desalination plants (IPDP) may provide a key solution for the pressing freshwater deficit and energy problems in many regions of the world. The current study investigates the potential of low-temperature multi-effect distillation (LT-MED) and thermal vapor compression multi-effect distillation (TVC-MED) coupled with a concentrating solar power (CSP) plant, taking also into account a reverse osmosis (RO) unit connected to the same power plant. The thermodynamic performance of the proposed schemes of IPDP has been evaluated by the assessment of the net output thermal capacity and the net power cycle efficiency of the different configurations, together with the estimation of the size of the solar field required to provide the corresponding thermal capacity. The results show that the combination with LT-MED is more efficient thermodynamically than with TVC-MED. Also, the CSP plant coupled with TVC-MED is more cost-effective than the independent processes because it requires a smaller solar field. The integration of a MED plant reduces the cooling requirements of a CSP power plant but the CSP+RO combination has a better thermodynamic efficiency. However, the difference with respect to CSP+LT-MED is small, so the latter can be more convenient in some cases. [Copyright &y& Elsevier]

Abstract: Seawater desalination has become an important and ever-increasing industry which faces up the environmental situation of water scarcity present in some Mediterranean countries and in the Canary Islands (Spain). This activity presents several environmental drawbacks and negative impacts on marine ecosystems, originated mainly by the discharge into the sea of the generated brine. This emphasizes the need of introducing, in the short-term, new management proposals for this particular case which should be both economically viable and effective, not only for new setting up plants, but also for those already installed. As an alternative to brine disposal, an adequate system has been proposed and developed for the reuse of this saline waste coming from reverse osmosis desalination plants in the chlor-alkali industry by NaCl electrolysis in membrane cells. In this paper, the various treatment phases, necessary for the adaptation of this residue as an alternative raw material resource in the chlor-alkali manufacturing industry, are described. This study has been adapted to Pozo Izquierdo Reverse Osmosis Desalination Plant, in Gran Canaria. This new and different residue reuse as raw material supposes the production and exploitation of new chemical resources, as for example: chlorine, hydrogen gas, and caustic soda. [Copyright &y& Elsevier]

Abstract: Aim of this work is to model, optimize and characterize the design of a direct contact condenser utilizing spherical phase change material (PCM) elements as a packing medium in a solar driven humidification–dehumidification (HDH) desalination plant. Assuming local thermal non-equilibrium and departing from the continuous solid phase model, a simplified one-dimensional heat and mass transfer model has been developed and solved using interpenetration continua approach with volume averaging technique. The model has been validated against experimental data and was then used for further parametric analysis. Comparison with measurements showed good agreement with less than 3% of the fresh water production rate. The thermal behavior of the new condenser equipment is discussed and analyzed. Fundamental variables and critical parameters affecting the system performance such as the effect of condenser geometrical aspect ratio, packing size, air to water mass flow rate ratio, PCM thermal properties, and the effect of different types of packing media were studied. A system parameters analysis and characteristic guidelines for the optimum parameters and operation conditions have been obtained and will be presented thoroughly. Comparative performance of the system is clearly documented using PCM and Non-PCM packing elements. [Copyright &y& Elsevier]

Abstract: The desalting of seawater has been a vital issue in several countries around the world in which water shortage is a serious problem. Through the process of designing desalination systems, with consideration of energy crisis, amount of energy consumption is a very important economical factor. In multi-effect distillation systems with thermal vapor compression (MED–TVC), thermo-compressor plays a main role in energy consumption. The geometry and operating conditions of thermo-compressor can have a significant influence on energy consumption. In this research, the influence of changing the suction position of thermo-compressor on the amount of energy consumption of the plant is analyzed. Results of the study showed that variation in suction pressure of thermo-compressor has considerable effects on the entrainment ratio. However, in order to have the maximum entrainment ratio and consequently reduce energy consumption, integration of MED–TVC with MED desalination must be optimized into the position of thermo-compressor suction. It was found that changing the suction location of thermo-compressor from the last effect to the middle effects or increasing the suction pressure has a valuable role in decreasing the energy consumption of the system. Results showed that the optimum value of compression ratio of thermo-compressor is between 2 and 2.5. [Copyright &y& Elsevier]

Abstract: This paper deals with the effects of equipment reliability consideration to thermoeconomic analysis of a combined power and multi stage flash water desalination plant. Exergy and thermoeconomic models of the considered process units are developed and presented in this work. An economic model of the system is developed according to the Total Revenue Requirement (TRR) method. This application can be very useful, either for the plant management in order to achieve a cost-effective operation, or for a better plant design. Equipment reliability using the state-space and the continuous Markov method is incorporated in thermoeconomic analysis to improve the cost values. The results show that the power and water costs with reliability consideration increased 4.1% and 6.4%, respectively. Additionally, the sensitivity analysis shows the relationship between the production cost and the system availability which can help the designer to decide how to improve the profit or competitiveness. [Copyright &y& Elsevier]

Abstract: This study provides geochemical data with the aim of assisting in the proper managing of groundwater resources and so avoiding negative impacts on the aquifers. The area covers the coastal aquifer of Cabo de Gata, which supplies a new desalination plant. Groundwater samples, to different depths, were characterized to identify the main processes occurring in the system, as well as to establish their relationship with seawater. Major and minor elements, and their ionic ratios distinguish two groups of samples: G1) samples containing between 7 and 70% seawater, with SO4 2−/Cl− and Br/Cl− ratios that decrease with salinity; G2) water containing between 99 and 112% of seawater, SO4 2−/Cl− similar to that of seawater (0.12) and a Br/Cl− ratio that increases with salinity. Different scenarios were simulated using PHREEQC geochemical code: a) conservative seawater–freshwater mixing, b) modified freshwater–seawater mixing, c) freshwater-modified seawater mixing and d) modified freshwater–modified seawater mixing. Modeling results indicate that the processes that best match the groundwater samples are different for the two groups identified. Water in group 1 is best simulated by a mix of modified freshwater (by water–rock interaction processes) with seawater, and group 2 by mixing a modified (evaporated) seawater with freshwater. [Copyright &y& Elsevier]

Abstract: An approximate cost of desalinated water treatment has been calculated to reduce the concentration of boron. The study is based on experimental data obtained in pilot plants working continuously with real water from a previous RO desalination. The results of the analysis should be taken as approximate, since on one hand experimentation in the pilot plant should be extrapolated to an industrial plant and on the other hand some of the costs included are estimates or theoretical. However, the analysis allows us to know the parameters that most contribute to the final cost of treated water. The results obtained were compared with different membranes and different commercial resins. The cost for the removal of boron at levels below the detection limit can be between 0.2 and 3.2cent€/m3 higher when membranes are used than when using resins. This is due mainly to the cost of reagents necessary to raise the pH. If the boron concentration is to be reduced to 0.5mg/L, then the differences are reduced and the membrane process is the more economical. The cost of membrane treatment is between 0.1 and 1.2cent€/m3 less than treatment with resins. [Copyright &y& Elsevier]

Abstract: An approach to real-time analysis of mineral scale formation on reverse osmosis (RO) membranes was developed using an ex-situ direct observation membrane monitor (MeMo). The purpose of such monitoring is to signal the onset of mineral scaling and provide quantitative information in order to appropriately initiate system cleaning/scale dissolution. The above is enabled by setting the MeMo operating conditions (cross flow velocity and transmembrane pressure) to closely match the conditions in the monitored membrane plant (e.g., in the tail RO element) in order to mimic the surface scaling processes taking place inside the monitored RO plant element. Mineral scale in the MeMo system is monitored by comparison of consecutive images of the membrane surface for the purpose of determining the evolution of the fractional coverage by mineral salt crystals and the corresponding crystal count in the monitored region. Through online image analysis, once crystal growth is determined to be above a prescribed threshold, one can then initiate any number of cleaning protocols. Through early detection of membrane scaling (i.e., before permeate flux decline is observed), enabled by the present monitoring approach, the system operator can prevent irreversible membrane damage and loss of system productivity. [Copyright &y& Elsevier]