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In this article to tackle the main concerns of today's world as fossil fuel shortage, environmental impacts of fossil fuels like global warming and atmosphere pollution as well as water scarcity, a novel power plant is designed. In this regard, the proposed plant comprises of biomass gasification unit, photovoltaic thermal collectors, a proton exchange membrane hydrogen production unit, as well as a reverse osmosis water purification plant. The plant is named as (biomass-fired combined cycle with photovoltaic, thermal collectors, hydrogen production, and reverse osmosis) BCPVHR and to assess its performance, energy, exergy, exergoeconomic, and environmental analyses are performed. The varying parameters are compressor pressure ratio and gas turbine inlet temperature. These two parameters' impact on energy efficiency, exergy efficiency, net generated power, fresh water production, total unit product cost as well and environmental index are assessed. The results are useful for adjusting the compressor pressure ratio and gas turbine inlet temperature. Please note that this plant is designed to be used completely or partially in sports facilities and can be a valuable endeavor for managing sports facilities to use renewable energy in their construction. Meanwhile, based on the priories of products different values of parameters can be used. Increasing the compressor pressure ratio raises the total unit product cost and the environmental index until 11.5 decreases and later increases. Increasing the gas turbine inlet temperature decreases the both total unit product cost and environmental index which reach 65 $/GJ and 65 kg/kWh, respectively. • A novel power plant is designed. • Plant comprises of biomass gasification unit and photovoltaic. • Plant uses proton exchange membrane for hydrogen production. • System uses reverse osmosis for water purification. • Energy, exergy, exergoeconomic, and environmental analyses are performed. [ABSTRACT FROM AUTHOR]

In this study, the wastewater treated by the membrane bioreactor (MBR) process at the wastewater treatment plant of ITOB Organized Industrial Zone was used as the feed solution for further desalination by nanofiltration (NF90) and reverse osmosis (BW30) membranes. The effect of chemical cleaning to control the membrane fouling during long-term repeated uses of both NF and RO membranes were investigated. The water permeability values were obtained using deionized water as the feed solution after five cycles of desalination-membrane cleaning-permeability tests. Water permeability values changed from 3.93 L/m2·h·bar to 1.35 L/m2·h·bar for BW30 and 7.76 L/m2·h·bar to 2.65 L/m2·h·bar for NF90. The permeability tests were also carried out by using MBR effluent as the feed solution for better evaluation of fouling effects for MBR treated wastewater on desalination performance of NF and RO membranes. An optimal cleaning strategy was suggested throughout the study. Unlabelled Image • Effects of fouling on permeate flux of NF and RO processes are investigated. • Mini-pilot scale long-term membrane tests were performed. • An efficient membrane chemical cleaning strategy was established to control fouling. [ABSTRACT FROM AUTHOR]

Membranes with suitable nanopores and tunable charge characteristics are highly desired for their good application prospects in specific membrane-based separations. This study focused on the synthesis of polyamide (PA) composite membranes with tunable pore size and perm-selectivity. Trimellitic anhydride chloride (TAC) with an anhydride group, was introduced as the co-reactant of trimesoyl chloride (TMC) to form PA film via interfacial polymerization with m -phenylenediamine on the surface of the polysulfone substrate membrane. Due to the chemistry character difference (the number of functional group and acylation activity) between TMC and TAC, the structure and physico-chemistry properties of the PA film could be tailored through the control of TAC concentration. As a result, the nanopore radius of the membrane varied from <0.32 to 1.14 nm, along with the improved water permeability from 2.3 to 9.8 L m−2 h−1 bar−1 and selectivity of Na 2 SO 4 /NaCl from 2.2 to 4.9. This study provided a facile and effective approach for the fabrication of tailor-made membrane with tunable nanopore and ion selectivity designed at a molecular level. • PA-TFC membranes were fabricated with mixed organic phase monomers of TMC and TAC with an anhydride group. • The pore size (from RO to NF range) and charge of the membrane were tailored through varying the TAC content. • Enhanced perm-selectivity could be attained by the control of TAC content. [ABSTRACT FROM AUTHOR]

Wastewater reclamation and reuse became essential to meet the more restrictive discharge limits and to overcome the water scarcity issue. Industrial wastewaters treated by membrane bioreactor (MBR) systems generally include high amounts of salinity, nutrients as nitrogen and phosphorus, heavy metals, hardness, etc. which in most cases, do not fit with discharge and reuse limits. Membrane processes like nanofiltration (NF) and reverse osmosis (RO) are widely adopted for secondary effluent treatment producing high-quality water. Since untreated brine can damage the environment, this work focused on reduction of amount of concentrate by working in membrane-in-series configuration. Tests with two membrane-in-series (NF90 + NF90, BW30 + BW30, BW30 + NF270 combinations) were performed as the concentrate stream of the first one was fed to the second one. Water recoveries were over 80% in each experiment. Water fluxes of 44.0, 41.4 and 73.4 L/m2.h were obtained with NF90 + NF90, BW30 + BW30, BW30 + NF270 combinations, respectively. Also, salinity rejections represented by electrical conductivity were 92.9%, 97.4% and 42.9% for NF90 + NF90, BW30 + BW30, BW30 + NF270 configurations, respectively. Permeates of BW30 + BW30 and NF90 + NF90 combinations seem to be useable for agricultural irrigation although soil permeability is an important issue, not only ion concentrations and salinity of water used. • Three different membrane pairs were tested for concentrate reduction in desalination of MBR effluent. • Product waters of NF90 + NF90 and BW30 + BW30 were useful for irrigation. • Water recoovery was over 80% with no significant flux drop. [ABSTRACT FROM AUTHOR]

We present a multi-objective analysis of the optimization of seawater reverse osmosis (RO) desalination systems, considering economic, power requirement, and exergo-economic factors. Exergy flow for each stream and exergy destruction for each equipment in the RO network is included in the model. The exergo-economic unit cost (EUC) for the final product is considered as an objective function. An enhanced version of the augmented epsilon constraint method, AUGMECON2, is utilized to solve the multi-objective optimization problem, which allows for lexicographic optimization for other objectives if alternative optimum solutions exist. Redundant iterations are avoided through the use of the bypass coefficient. Results show that the Pareto solutions for permeate split design are located below the normal design. Fixed cost dominates the exergo-economic unit cost. The power cost has the greatest share of water cost, while pass 1 has the greatest share of exergy destruction. The throttling valves and blending of different salinity streams (final product mixer and first pressurization stage mixer) could cause non-negligible exergy destruction. The fixed cost for each equipment, exergy rate, and EUC for each flow rate are analyzed, in order to provide insights into the system. Unlabelled Image • Economic, energy, exergo-economic analysis are considered simultaneously. • Redundant iterations of MOO problems are avoided by bypass coefficient. • Fixed cost dominates exergo-economic unit cost. • Exergo-economic analysis is performed to get an insight view of the system. • Blending of different salinity streams causes non-negligible exergy destruction. [ABSTRACT FROM AUTHOR]

Brackish water (BW) desalination represents an untapped potential for augmenting water resources by the reliable technology of reverse osmosis (RO). There is a significant economic incentive to operate the process at the highest possible water recovery. A high recovery has the important advantage of reducing the amount of concentrate waste stream whose safe disposal is of significant environmental concerns. The degree of RO water recovery possible with a given raw water is dictated by the scaling problem. To overcome this hindrance, a variety of processes have been developed for conditioning the concentrate emanating from the primary RO unit for additional permeate production by a secondary RO unit. This paper provides a critical review of the treatment technologies that enable intensification of the water recovery in BWRO desalination by the intermediate concentrate demineralization techniques. The principles of each technique as well as its strength, weaknesses, technology readiness level, and economics are discussed. Extensive application of ICD technologies requires overcoming challenges such as lowering energy demand and total cost and reducing membrane scaling and use of chemicals. • Current and emerging intermediate concentrate demineralization (ICD) technologies are reviewed. • High recovery BW desalination is achieved by applying ICD technologies between consecutive RO stages. • Selection of ICD technology depends on water quality, treatment capacity and costs. • Challenges and future perspectives of these ICD technologies are discussed. [ABSTRACT FROM AUTHOR]

Renewable energy driven desalination has been proven to be a sustainable, economic and environmental friendly solution for the water deficiency problems in remote areas. However, one of the most important issues is the determination of the optimal configuration so that the system meets the water load at the minimum cost. In this paper, five different configurations of a sea water desalination system powered by photovoltaics were examined at autonomous mode. Αn island in Cyclades, Aegean sea, Greece, was used as a typical case study for the installation of such systems. Then, a comparison among the different configurations was realized in order to determine the optimum technical and economic system, by minimizing the total system installation and operation cost for 20 years lifetime, which then compared in economic terms with the water transportation practice. The present study shows that the application of a photovoltaic powered seawater reverse osmosis desalination unit that incorporates water storage, a small capacity battery bank and an energy management system, is technically feasible to produce fresh water. According to the optimal sizing results, the implementation of an energy management system designed on the basis of Fuzzy Cognitive Maps presents the lowest cost and lowest power losses. • Various energy management systems have been implemented and tested for a PV-SWRO desalination system. • A technical and economic evaluation of alternative configurations for a PV-SWRO desalination plant has been performed. • An autonomous PV-SWRO desalination plant with an EMS based on FCM is technically feasible and economically a sustainable. [ABSTRACT FROM AUTHOR]

On the West Coast of South Africa, there is an abundance of brackish groundwater. Reverse Osmosis membrane systems are used to make the borehole water fresh. Unfortunately, the salts that are removed from the water, precipitates on the membrane surface, thus, decreasing the overall process efficiency. In this study, the use of Zn2+ ions as an anti-scalant was investigated in terms of feasibility in the treatment of brackish water influent. Experimental tests were conducted on a bench scale unit, followed with a pilot plant thereafter. Three commercial membranes were exposed to natural groundwater scaling. The first, commercial anti-scalant treatment, second, anti-scalant treatment with Zn2+ ions and the third, untreated. The results, after a period of close to 5 months, showed that the flux of the membranes treated with commercial (32.78 L·m−2·h−1) and zinc (30.80 L·m−2·h−1) ions anti-scalant was higher than the untreated membrane flux (25.56 L·m−2·h−1), which decreased continuously. Unlabelled Image • Maximum concentration of Zn ions generated in the electrolytic was obtained at a potential difference of 2 volts. • The use of Zn2+ improved anti-scaling capacity of the membrane when treating brackish water • Scaling of the membrane in the pilot plant was minimized with the use of commercial anti-scalant as well as Zn ions. • SEM and OM analyses showed that deposits on the membrane surface were minimized with the use of both anti-scalants tested [ABSTRACT FROM AUTHOR]

Membrane recycling by oxidative treatment is one alternative to minimize the impacts of the disposal of end-of-life (EoL) reverse osmosis (RO) membranes. In parallel, iron (Fe) and manganese (Mn) contamination in surface and groundwater is increasing. This study aims to develop recycled membranes that retain dissolved Fe and Mn from water for supply purposes. EoL RO membranes were recycled with sodium hypochlorite (NaClO, 10–12%) solution at exposure dose between 4000−80,000 ppm∙h to produce a recycled membrane with high flowrate and high Fe and Mn rejection. EoL RO treated by 40,000 ppm·h showed water permeability of 54.30 L∙h−1∙m−2∙bar−1 and Fe and Mn rejection of 99% and 65%, respectively. Potability for Mn (> 98%) was enhanced by integrating pre-oxidation stage with NaClO (5 mg∙L−1 of Cl- and pH 8) to the recycled membrane process. Recycled module performance was evaluated for water treatment from Paraopeba River on pilot scale, in continuous operation (51 h) and pressure of 1 bar. At pilot scale, recycled membrane obtained a water permeability of 40.33 L∙h−1∙m−2∙bar−1, like a moderately open ultrafiltration membrane. Fe and Mn removals were > 99% and > 90%, respectively, with high color and turbidity removal efficiency. Membrane recycling cost was predicted to be US$ 4.08/m², and the capital (CapEX) and operating (OpEX) expenditures for the single-household system was US$ 671.18 and US$ 22.52 to m3·day−1 of treated water. Therefore, the recycled membrane was shown to be efficient in removing dissolved Fe and Mn, and it is promising for decentralized water treatment. [Display omitted] • Recycling by oxidative treatment mitigate the disposal of end-of-life RO membrane. • Recycled membranes remove Fe and Mn from surface water for water supply purposes. • Recycled membranes can be used in decentralized water treatment systems. [ABSTRACT FROM AUTHOR]

Abstract A new concept to concentrate seawater up to 200 g/kg for producing vacuum salt using a reverse osmosis (RO) system hybridized with an electrodialysis (ED) system is presented. The RO system operates up to pressures of 120 bar and concentrates seawater up to 120 g/kg with the ED system concentrating RO brine to 200 g/kg. A parametric analysis to minimize the specific cost of brine concentration was conducted. Parameters varied were: the degree of RO-ED hybridization, ED current density, electricity prices and water prices. Optimal hybrid RO-ED designs reduced brine concentration costs by 33–70 % over standalone ED systems, with revenue generated from water co-production further subsidizing costs by 1–6 %. Optimizing ED current density reduced costs the most. Including a crystallizer, the total reduction in production cost over a standalone ED-crystallizer system was 19–55 % , with the production cost for a typical case being $111/tonne-salt. The proposed RO-ED-crystallizer (REC) systems were found to be techno-economically feasible in Cyprus, Japan, Kuwait, Saudi Arabia, and the USA. At a road transportation distance of 735 km, REC based seawater vacuum salt was competitive with conventional vacuum salt. REC systems may open up the potential of small-scale decentralized salt production. [ABSTRACT FROM AUTHOR]

Abstract In this investigation, a polygeneration scheme integrating local desalination units with CCHP systems, providing cold, heat and power for Kish twin towers as well as providing a portion of the fresh water demand of the island, is proposed and evaluated in terms of energy, environment, and economy aspects. The proposed system is compared to the conventional CCHP and desalination system adopting the separate production system as the reference. Here, two types of desalination technologies, namely multi-effect distillation (MED) and reverse osmosis (RO) processes, are used to provide desalinated water. A genetic algorithm is implemented to determine the optimal operating parameters. It results in that in the polygeneration system the yearly average power generation efficiency, the annual primary energy saving ratio (APESR) and the annual total cost saving ratio (ATCSR) of the whole system increase by 3.45%, 9.73%, and 6.49%, respectively, compared to the conventional system. Using the MED process can increase the ATCSR from 9.8% to 16.0%, depending on the fresh water market price. Moreover, the carbon dioxide emission (CDE) decreases by 1460.5 tons each year, compared to the reference. It is also indicated that 93.87% of the MED input heat can be recovered for domestic hot water (DHW) provision. Highlights • The integration of local desalination and CCHP units has been investigated. • The effects of the combination on the performance of each unit have been evaluated. • A new way for integrating the MED unit with the CCHP system has been optimized. • The integration mainly improves the part-load performance of the CCHP system. • Adopting MED process can considerably improve energy and economic performance of the whole system. [ABSTRACT FROM AUTHOR]

Abstract Two dimensional (2 D) layered materials with special properties provide opportunities to design energy-efficient membranes for water desalination. A negatively charged layered graphene analogue, molybdenum disulfide (MoS 2) was synthesized through liquid exfoliation. A novel thin film nanocomposite (TFN) reverse osmosis (RO) membrane was successfully fabricated with prepared laminar MoS 2 as fillers in the organic phase through interfacial polymerization of m -phenylenediamine and trimesoyl chloride monomers. The laminar MoS 2 nanosheets were observed by transmission electron microscopy (TEM), and the nanosheets were dispersed in the polyamide (PA) matrix as well as on the membrane surface. The properties of the resultant TFN membranes were effectively modified by taking the advantage of two dimensional features, i.e., the negative charge and the hydrophilic sites of layered MoS 2. Compared to a classical TFC membrane, the MoS 2 incorporated TFN membranes were found to have an increased salt rejection and higher water flux. Moreover, 0.01 wt% MoS 2 -TFN membrane showed a superior fouling resistance against proteins as foulants. The antifouling behavior of this TFN membrane was observed by field-emission scanning electron microscopy (FE-SEM). Stability tests demonstrated that there was a loss of MoS 2 in the initial 2 h filtration, but the process is stable in the long-term. Graphical abstract Unlabelled Image Highlights • Negatively charged layered MoS 2 was prepared through liquid exfoliation. • Laminar MoS 2 nanosheets were successfully incorporated in the polyamide matrix and modified the membrane surface. • MoS 2 -TFN RO membrane showed decreased selective layer thickness, increased surface hydrophilicity and surface roughness. • MoS 2 -TFN RO membrane exhibited high perm-selectivity and improved fouling resistance. [ABSTRACT FROM AUTHOR]

Abstract As water shortage has increasingly become a serious global problem, desalination using seawater reverse osmosis (SWRO) is considered as a sustainable source of potable water sources. However, a major issue on the SWRO desalination plant is the generation of brine that has potential adverse impact due to its high salt concentration. Accordingly, it is necessary to develop technologies that allow environmentally friendly and economically viable management of SWRO brines. This paper gives an overview of recent research works and technologies to treat SWRO brines for its beneficial use. The treatment processes have been classified into two different groups according to their final purpose: 1) technologies for producing fresh water and 2) technologies for recovering energy. Topics in this paper includes membrane distillation (MD), forward osmosis (FO), pressure-retarded osmosis (PRO), reverse electrodialysis (RED) as emerging tools for beneficial use of SWRO brine. In addition, a new approach to simultaneously recover water and energy from SWRO brine is introduced as a case study to provide insight into improving the sustainability of seawater desalination. Highlights • This manuscript describes the pilots (SWRO-PRO and SWRO-MD) built under the project of Global MVP (GMVP). • SWRO-PRO pilot plant (240 m3/d) based on spiral wound module incorporated the energy recovery device inside the pilot so as to monitor the energy saving. • MD pilot plant (400 m3/d) using hollow-fiber membrame/module unlike other pilot plants. [ABSTRACT FROM AUTHOR]

Abstract Several fouling indexes, such as silt density index (SDI), have been applied in the reverse osmosis (RO) process to predict the fouling tendency, design the pretreatment process, and optimize the cleaning cycles. However, the forward osmosis (FO) process has no reliable method, as yet, that relates fouling with its performance. This study utilized the concept of fouling reversibility to develop a fouling index for the FO process simulation. The osmotically driven reversibility index (ORI) was determined by measuring the flux recovery after the physical cleaning or flushing cycle. The protocols of ORI measurement were developed systematically by determining the proper operation mode, cross-flow velocity for physical cleaning, and draw solution type and concentration. The applicability of ORI was examined by investigating the FO process in treating secondary effluents from various full-scale wastewater treatment plants. The results demonstrated that the normalized final flux by fouling in FO was closely correlated to the ORI measurements with high statistical reliability (R2 = 0.84). After conducting a long-term stable FO operation, it is deduced that the ORI is a useful evaluation parameter for continuous FO and its cleaning cycles in which periodic flushing is normally utilized to exploit and enhance the fouling reversibility of FO. Graphical abstract fx1 Highlights • An osmotically-driven reversibility index (ORI) was developed for FO process. • ORI simulates FO fouling reversibility and its operational protocol was constructed. • High correlation of ORI and FO fouling was obtained using various real wastewaters. • ORI is a useful evaluation parameter for continuous FO and its cleaning cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Introduction of the environmental impacts index on RO system. • Choosing the optimum configuration and ORC fluid from 4E+D point of view. • The benefit of low grade heat losses to reduce the environmental impacts of RO. • Water-Energy-Environmental nexus. Abstract This paper presents the concentration disposal index (CDI) concept extension for increasing the Water–Energy-Environmental nexus and reducing the environmental impacts of RO system brine. This non-dimensional index introduces the difference between the density of brine flow and raw water tank in recovery. This concept is utilized in main engine system of the ship. Different configurations of Organic Rankine Cycle (ORC) and working fluids are studied at the outlet of high temperature thermal source (280 °C), based on Energy analysis (1E), Exergy (2E), Economic (3E) and environmental impacts (4E) in order to produce desalinated water (4E+D). The output power from ORC is used as the driver of RO high pressure pump. Based on the waste heat in system, the sources are used for preheating of RO system pump inlet water. These sources are: Lubricating oil, air cooler and jacket cooler and ORC condenser. The key parameters in optimization are: (1) the ORC configuration choice, (2) the working fluid of Rankine cycle based on thermal source, (3) the RO system optimum design, (4) the membrane selection among the DOW company membranes, (5) the pinch and approach temperatures of the Waste Heat Recovery (WHR), (6) the reduction of environmental impacts of RO brines, (7) the selection of Energy Recovery Device (ERD). Determination of these parameters is done according to system optimization by genetic algorithm (GA). In order to consider the CDI function impact, once the system is considered with two objectives based on exergy efficiency of the entire cycle and the unit product cost (UPC) and then is considered by three objectives; the two mentioned ones and the CDI function. The results of these two optimizations indicate that, utilizing CDI reduces the ultimate concentration of the brine and increases the buoyancy force for faster mixture. In three-objective optimization, the ORC configuration is chosen with the recuperator, the R245ca working fluid, the two-stage RO system and the SW30XLE-400i membrane for both of stages. [ABSTRACT FROM AUTHOR]

Abstract Recent progress in reverse osmosis (RO) technology is not limited to RO membrane materials, module designs and RO process optimization. It involves prior feed treatment which directly impacts RO system performance. The ongoing challenges of membrane fouling in RO membranes can be addressed by increasing the operational efficiency through the use of correct pretreatment options which can mitigate organic and inorganic fouling by selectively rejecting contaminants prior to reaching the RO unit. Highly polluted water resources have put critical stress on the existing conventional pretreatment techniques, whereby membrane pretreatment has emerged as a promising alternative. This paper provides an overview of the development and current trends in conventional and non-conventional RO pretreatment techniques whereby the techniques are critically reviewed to inform readers of potential improvements in such areas. This paper addresses the major drawbacks of conventional pretreatment methods which have necessitated the use of membrane pretreatment techniques. Special attention is given to microfiltration, ultrafiltration and nanofiltration methods and their development in terms of advanced membrane materials based on ceramics and self-cleaning membranes. Studies from laboratory scale standalone systems, pilot scale and large scale integrated systems for performance, cost and ecological analysis have been reviewed to familiarize readers with the many factors which need to be analyzed for selection of the appropriate pretreatment method(s). The critical review in this paper will help researchers focus more on the areas which have room for further development for cost-effective and advanced RO pretreatment techniques. Highlights • Reverse osmosis (RO) pretreatment continues to be one of the most challenging aspects of RO plants. • Membrane pretreatment capital and operational cost is higher than conventional pretreatment. • Membrane pretreatment water production cost is smaller than conventional ones due to improved permeate quality. • Ultrafiltration system with minimal prior pretreatment can reduce the cost of the overall RO process. • Integrated pretreatment systems incorporating nanofiltration saved up to 25–30% energy. [ABSTRACT FROM AUTHOR]

Abstract In the context of decentralised brackish water treatment in development applications, the influence of water quality on membrane separation was investigated with real waters. High ionic strength (low net driving pressure) on fluoride (F) retention by nanofiltration (NF) and reverse osmosis (RO) was investigated over a wide pH range (2–12). Further, the influence of pH on the permeation of natural organic matter (NOM) fractions, in particular low molecular weight (LMW) neutrals, was elucidated. Natural and semi-natural waters from Tanzania with similar F concentrations of about 50 mg L−1 but varying NOM and inorganic carbon (IC) concentration were filtered with an NF and RO, namely NF270 and BW30. F retention by NF270 for the feed water with highest ionic strength and IC concentration was lower and attributed to charge screening. This parameter further reduced at high pH due to co-ions (F− and CO 3 2−) interactions and combined (synergistic) effect of high salt concentration and pH on F. High NOM resulted in higher membrane zeta potential in comparison with low NOM natural water. However, there was no significant difference in F retention due to the fact that F retention enhancement was annulled by deposit formation on the membrane. The fraction of NOM found in NF/RO permeates was dominated by LMW neutrals. This was attributed to their size and uncharged nature, while their higher concentration at low pH remains unexplained. More humic substances (HS) of higher molecularity and aromaticity permeated the NF270 when compared with BW30, which can be explained with the different membrane molecular weight cut off (MWCO). The study highlights the complexity of treating tropical natural waters with elevated F and NOM concentrations. In order to develop appropriate membrane systems that will achieve optimal F and NOM removal, the influence of water quality parameters such as pH, NOM content, ionic strength and IC concentration requires understanding. Seasonal variation of water quality as well as operational fluctuations, which occur in particular when such treatment processes are operated with renewable energy, will require such challenges to be addressed. Further, given the high permeability of low molecular weight (LMW) organics significant permeate side fouling may be expected. Highlights • Real tropical waters with different IS, IC, NOM but similar F content treated by NF/RO. • At high IS & pH, F retention decreases due to IC speciation, pH and salt effect. • No enhancement effect of high NOM on F retention was observed. • A discrepancy between permeate NOM measured by TOC analyser and LC−OCD was observed. • According to LC−OCD results, LMW neutrals accounted for 60–90% of permeate NOM. [ABSTRACT FROM AUTHOR]

Abstract One possible contender to replace conventional reverse osmosis schemes is an energy solution where inexhaustible resources work together with a reverse osmosis plant. Based on the experience of an existing wind-powered desalination scheme run for more than 15 years by Soslaires Canarias S.L., the final objective of this paper is to propose improvements to the scheme so as to achieve a reduction in the cost of water (through restrained capital expenses) for the sake of greater feasibility and efficiency. The cost of the scheme is evaluated assuming a combined use of a reverse osmosis desalination plant and wind energy, using, for this purpose, the (exclusive) information provided by the industrial partner. Results showed that by carrying out the actions suggested in this paper, this scheme would be able to reduce its cost of water (COW) by about 0.022 EUR per cubic meter for the current LCOE of wind turbine technology in the study area (about 6 c€/kWh for the southeast of the island of Gran Canaria, Spain). This would mean that with an additional total capital investment cost of 196 000 € (from the current scheme of Soslaires Canarias S.L.), and supposing an average membrane life expectancy of 10 years for the current state-of-the-art membranes, a net present value of 74 360.95 €, a profitability index of 1.3794, and a 224.4881% internal rate of return would be achieved. Graphical abstract Typical cost structure for RO seawater desalination. Image 1 Highlights • Several configurations of desalination plants based RES have been simulated. • Cost of water has been considered as the central element of the evaluation. • In case of carrying out the actions suggested COW would be reduced. [ABSTRACT FROM AUTHOR]

Abstract As potable reuse guidelines and regulations continue to develop, the presence of N -nitrosamines is a primary concern because of their associated health concerns. In this study, bench-, pilot-, and full-scale tests were conducted to focus on the occurrence and treatment of N -nitrosomorpholine (NMOR) in United States (U.S.) potable reuse systems. Out of twelve U.S. wastewater effluents collected, ambient NMOR was detected in eleven (average = 20 ± 18 ng/L); in contrast, only two of the thirteen surface water and stormwater samples had NMOR. Across all of these samples maximum formation potential by chloramination produced an average increase of 3.6 ± 1.8 ng/L. This result underscores the need to understand the sources of NMOR as it is not likely a disinfection byproduct and it is not known to be commercially produced within the U.S. At the pilot-scale, three potable reuse systems were evaluated for ambient NMOR with oxidation (i.e., chlorination and ozonation), biofiltration, and granular activated carbon (GAC). Both pre-oxidation and biofiltration were ineffective at mitigating NMOR during long-term pilot plant operation (at least eight-months). GAC adsorbers were the only pilot-scale treatment to remove NMOR; however, complete breakthrough occurred rapidly from <2000 to 10,000 bed volumes. For comparison, a full-scale reverse osmosis (RO) potable reuse system was monitored for a year and confirmed that RO effectively removes NMOR. Systematic bench-scale UV-advanced oxidation experiments were undertaken to assess the mitigation potential for NMOR. At a fluence dose of 325 ± 10 mJ/cm2 , UV alone degraded 90% of the NMOR present. The addition of 5 mg/L hydrogen peroxide did not significantly decrease the UV dose required for one-log removal. These data illustrate that efficient NMOR removal from potable reuse systems is limited to RO or UV treatment. Highlights • Surface waters and wastewaters typically did not form NMOR under chloramination. • Ozone-BAC did not significantly remove NMOR during pilot-plant operation. • Limited sorption of NMOR was observed during GAC pilot-plant operation. • Low pressure UV removed NMOR at doses lower than those required for NDMA. • Significant removal of NMOR in potable reuse is limited to RO or UV treatment. [ABSTRACT FROM AUTHOR]

Abstract The robustness of reverse osmosis (RO) against polar organic micropollutants (MPs) was investigated in pilot-scale drinking water treatment. Experiments were carried in hypoxic conditions to treat a raw anaerobic riverbank filtrate spiked with a mixture of thirty model compounds. The chemicals were selected from scientific literature data based on their relevance for the quality of freshwater systems, RO permeate and drinking water. MPs passage and the influence of permeate flux were evaluated with a typical low-pressure RO membrane and quantified by liquid chromatography coupled to high-resolution mass spectrometry. A strong inverse correlation between size and passage of neutral hydrophilic compounds was observed. This correlation was weaker for moderately hydrophobic MPs. Anionic MPs displayed nearly no passage due to electrostatic repulsion with the negatively charged membrane surface, whereas breakthrough of small cationic MPs could be observed. The passage figures observed for the investigated set of MPs ranged from less than 1%–25%. Statistical analysis was performed to evaluate the relationship between physicochemical properties and passage. The effects of permeate flux were more pronounced for small neutral MPs, which displayed a higher passage after a pressure drop. Graphical abstract Image 1 Highlights • Strong size-passage correlation for neutral hydrophilic organics (log D <2). • Weaker size-passage correlation for moderately hydrophobic organics (log D >2). • Passage of cationic organics was higher than that of anions of comparable size. • Low permeate flux resulted in increased passage of small neutral polar organics. • Higher salt and organic passage observed for at least 5 h following a pressure drop. [ABSTRACT FROM AUTHOR]

Abstract Potable water production is an essential but energy intensive process and usually requires many chemicals. Furthermore, small-scale plants are not yet available because of the problems associated with downscaling the thermal evaporation or reverse osmosis processes. Freeze crystallization is an alternative, especially for the self-sufficiency of potable water in remote areas. The use of a crystallizer and a separate press in combination with a perforated pressing mold has shown that the desalination of saltwater can be achieved by pressing the ice only; no additional washing step is necessary. A pressing force of 37.4 kN (100 bar) and a holding time of 180 s were found to be sufficient. Therefore, these parameters were used to design a single-step plant, which also showed good results in the case of ion expulsion. Nonetheless, the variation in the test parameters showed their influence on crystal growth and crystal purity and demonstrated the need to find the optimal design parameters for future continuously operating systems. Highlights • Development of a single-step plant continuously producing potable water • Small-scale plant for self-sufficient supply in remote areas • Comparison of Nusselt correlations for a scraped surface crystallizer • Prove of pressing as post-treatment step for freeze desalination [ABSTRACT FROM AUTHOR]

Abstract Due to the improved dilution of draw streams, employing pressure-assisted forward osmosis (PAFO) to the hybrid system of forward osmosis (FO) followed by reverse osmosis (RO) for seawater desalination has been expected to reduce the overall economics. However, replacing FO with PAFO causes an additional energy cost in the seawater dilution step which inevitably leads to a question that PAFO-RO hybrid is truly an economically beneficial option. More importantly, though serial connection of FO elements improves the dilution of initial draw water, this economic benefit is also compensated with the additional membrane. To rationalize its overall performance and economic benefit, thorough performance and economic evaluations were conducted based on actual pilot-scale PAFO operations for serial connection of up to three 8040 FO elements. The results showed the FO-RO hybrid is not an economically feasible option unless a significant unit FO element cost cut-down is guaranteed. Meanwhile, PAFO-RO showed benefits with regards to target RO recovery and unit FO element cost, particularly when two FO elements are serially connected (SE2). It was found that PAFO-RO, indeed, has higher economic potential than FO-RO. A graphical overlapping method suggested in this work can help determine optimal serial configuration and operating conditions of PAFO-RO. Graphical abstract Unlabelled Image Highlights • Significant impact of initial draw flowrate and hydraulic pressure on the PAFO-RO economics • Hydraulic pressure dependence of FO membrane element performance • Drastic pressure-drop in the draw channel of the last element in serial configuration • Target RO recovery and unit FO element cost in PAFO-RO hybrid are important for economics [ABSTRACT FROM AUTHOR]

Abstract The coupling of thermal (multi stage flash, MSF) and membrane processes (reverse osmosis, RO) in desalination systems has been widely presented in the literature to achieve an improvement of performance compared to an individual process. However, very little study has been made to the combined multi effect distillation (MED) and reverse osmosis (RO) processes. Therefore, this research investigates several design options of MED with thermal vapor compression (MED_TVC) coupled with RO system. To achieve this aim, detailed mathematical models for the two processes are developed, which are independently validated against the literature. Then, the integrated model is used to investigate the performance of several configurations of the MED_TVC and RO processes in the hybrid system. The performance indicators include the fresh water productivity, energy consumption, fresh water purity, and recovery ratio. Basically, the sensitivity analysis for each configuration is conducted with respect to seawater conditions and steam supply variation. Most importantly, placing the RO membrane process upstream in the hybrid system generates the overall best configuration in terms of the quantity and quality of fresh water produced. This is attributed to acquiring the best recovery ratio and lower energy consumption over a wide range of seawater salinity. Highlights • Detailed mathematical models for MED-RO hybrid process are developed. • The performance of different superstructures of the hybrid process is simulated. • Sensitivity analysis aids to detect the best structure based on performance factors. • Hybrid configuration with RO upstream achieves the best performance indicators. [ABSTRACT FROM AUTHOR]

Abstract A hybrid system consisting of RO (reverse osmosis) and SE (Stirling engine) was proposed to utilize the moderate temperature heat for the brackish water desalination. The performance of two configurations was systematically investigated. Config. II employs ERD (energy recovery device) to harvest the residual pressure energy in outlet feed solution for the pre-pressurization of inlet feed solution while Config. I does not. Impacts of substance temperature in the SE heater and RO hydraulic pressure difference on the fresh water recovery ability and energy consumption were investigated. Results indicated that Config. I presents the highest recovery rate of 17.3% while Config. II gets the largest fresh water production of 34.2 L/h. As to the energy consumption, a lowest specific energy consumption of 2.5 kW · h / m 3 and specific thermal energy consumption of 35.9 MJ/m 3 were achieved in Config. II, which exhibits much more effectively compared to those obtained in Config. I. Furthermore, the performance comparison under the ideal and non-ideal SE models was also conducted. Highlights • High flow rate can reduce the osmotic pressure difference aside membrane. • High hydraulic pressure difference is beneficial for system performance. • Energy recovery device reduces the specific thermal energy consumption by 52%. • Energy consumption can be reduced up to 35% with a more efficient Stirling engine. [ABSTRACT FROM AUTHOR]

Abstract Multi-Stage-Flash (MSF) Distillation is a large scale sea water desalination plants that are widely used in Gulf area. Most installations of MSF plants are operated in cogeneration with a power plant. Also, MSF plants can be combined with other desalination technologies such as Nano filtration and Reverse osmosis (RO) in new installation. However, the new MSF plants are recommended, where large amounts of cheap or waste energy are available (e.g. conventional power plants). Also, the plant location is playing an important role for economic operation due to cold or hot weather conditions. The present study is applied on the seawater multi-stage flash (MSF) desalination plant that is currently under operation in Al-Khafji operations plant located in Saudi Arabia (KSA). The plant contains 20 evaporator stages at capacity of 600,000 gallon per day (GPD). The presented operating data has been collected during a visit of the plant. The objective is to present field results of this MSF plant operation in order to measure and evaluate the performance at 70% and 100% capacity during summer (case-1) and winter (case-2) operation. Then, the plant overall performance indicators are presented to compare between the studied two cases in terms of specific cooling water flowrates and performance ratio. Finally, the seasonal performance variation of the plant is included. The results showed that, for the same plant output, the main cooling water flow rates is decreased from 47.1% to 20.1% for case-1 and case-2 respectively, which in turns directly reduces the pumping power by the same ratio. Consequently, running the large scale thermal desalination MSF plant in cold regions is more economic than hot regions for pumping power energy saving considerations. This is to be considered in future large scale desalination plants. [ABSTRACT FROM AUTHOR]

Abstract Ensuring the biological stability of drinking water is essential for modern drinking water supply. To understand and manage the biological stability, it is critical that the bacterial growth in drinking water can be measured. Nowadays, advance treatment technologies, such as reverse osmosis (RO), are increasingly applied in drinking water purification where the produced water is characterized by low levels of nutrients and cell counts. The challenge is, therefore, how to measure the low bacterial growth potential (BGP) of such ultra-pure water using the available methods which were originally developed for conventionally treated drinking water. In this study, we proposed a protocol to assess BGP of ultra-pure drinking water produced by RO and post-treatment (including remineralization). Natural bacterial consortium from conventional drinking water was added to all water samples during this study to ensure the presence of a wide range of bacterial strains. The method development included developing an ultra-pure blank with high reproducibility to lower the detection limit of the BGP method (50 ± 20 × 103 intact cells/mL) compared with conventional blanks such as bottled spring water, deep groundwater treated by aeration and slow sand filtrate of surface water supply. The ultra-low blank consists of RO permeate after adjusting its pH and essential mineral content under controlled laboratory conditions to ensure carbon limitation. Regarding the test protocol, inoculum concentrations of >10 × 103 intact cells/mL may have a significant contribution to the measured low levels of BGP. Pasteurization of water samples before measuring BGP is necessary to ensure reliable bacterial growth curves. The optimized method was used to assess BGP of ultra-pure drinking water produced by RO membranes and post-treatment (including remineralization), where the BGP has decreased more than 6-fold to a level of 90 ± 20 × 103 intact cells/mL compared with conventionally treated water (630 ± 70 × 103 intact cells/mL). Graphical abstract Image 1 Highlights • The detection limit of bacterial growth potential method was significantly lowered. • Inoculum has a significant influence on bacterial growth potential measurements. • Pasteurization is necessary before measuring bacterial growth potential. • RO permeate has lower bacterial growth potential than conventional drinking water. [ABSTRACT FROM AUTHOR]

Abstract This work addresses the comparison of seawater desalination by the RO-PRO hybrid system with open-loop and closed-loop configurations regarding normalized specific energy consumption (NSEC) using a model-based optimization approach. The NSECs in both configurations are minimized by solving a constrained nonlinear optimization model so that the comparison is addressed based on their best conditions. The underlying impacts of membrane area, pretreatment energy of feed water, feed water concentration and internal concentration polarization on system performances are systemically investigated. It is shown that the optimization program gives priority to the closed-loop configuration due to its advantages in energy-saving and cost reduction at an adequate membrane area (γ tot ≥ 1.0) and low water recovery (Y ≤ 0.5). It highlights the significance of an essential prerequisite γ tot , min > π 0 Y /(σ ∆π PRO ¯) for the operation of a closed-loop configuration. Nevertheless, the analysis of internal concentration polarization effect further indicates that the closed-loop configuration may be vulnerable to the variation of operating and feed conditions and the degradation of membrane in practice. Graphical abstract Unlabelled Image Highlights • Open-loop and closed-loop RO-PRO systems are compared using a model-based optimization approach. • The coupled behaviour among membrane properties, operating conditions, and feed conditions are revealed. • Closed-loop system is advantageous in terms of energy-saving and cost reduction at γ tot ≥ 1.0 and Y ≤ 0.5. • There is a prerequisite γ tot , min > π 0 Y /(σ ∆π PRO ¯) for the operation of closed-loop system. [ABSTRACT FROM AUTHOR]

Abstract In remote areas, the vital need is production of drinking water and the provision of electrical energy for housing. Often the only sources of energy are based on renewable energies with storage to create a local micro-network. This paper investigates the optimal design of embodied energy for water treatment by reverse osmosis, coming from brackish water (6 g/l) and with a double storage that is done in a drinking water tank and in batteries for electricity. Taking account wind and photovoltaic potentials in such system for assessing its performance implies its simulation over long periods of time. This can drastically increase the CPU time cost related to the design step, especially if the system energy management and sizing are sequentially optimized into a two-level optimization process. In order to solve this problem and accelerate the system simulation, meta-models are used for representing the system constraints and objectives. These meta-models are built by the design of experiments method. From realistic data, the results of this paper show that the contribution of the meta-models divides by two or three the design time by obtaining values of the sizing parameters close to the dynamic simulator depicting the real operation of the whole system. Highlights • To propose a methodology for optimal sizing of a freshwater and electricity production system, for an isolated site, from renewable energies and a double storage in a battery and in the water tanks (brackish and freshwater). • This approach is applied to the total life cycle of the embodied energy (EE) and not of cost (the EE models are given in the paper). • The motor pump and reverse osmosis unit are modeled with a single parameter that depends on the flow rate per day (to limit the number of parameters to be optimized to facilitate the convergence of the optimization algorithm). • To compare the optimization results obtained with a dynamic simulator taking into account the meteorological data over one year with meta-models obtained by design of experiments. • The obtaining of these meta-models is one of the main highlights of this paper (obtaining the database, the equation forms of the meta-models,...). [ABSTRACT FROM AUTHOR]

Abstract Desalting brines from Reverse Osmosis (RO) plants is one of the most promising applications of Membrane Distillation (MD) systems. The development of accurate models to predict MD system performances plays a significant role in the design of this kind of industrial applications. In this paper, a commercial-scale Permeate-Gap Membrane Distillation (PGMD) module was modelled by means of two different approaches: Response Surface Methodology (RSM) and Artificial Neural Networks (ANN). Condenser inlet temperature, evaporator inlet temperature, feed flow rate and feed water salt concentration were selected as inputs of the model, while permeate flux and Specific Thermal Energy Consumption (STEC) were chosen as responses. The prediction abilities of both RSM and ANN models were compared with further experimental data by using the Analysis of Variance (ANOVA) and the Root Mean Squared Error (RMSE). The results show that the ANN model is able to predict in a more precise way the behaviour of the module for the whole range of input variables. Thus, ANN model was used to find the optimal operating conditions, for the module operating at feed water salinity of 70 and 105 g/L, concentrations that can be reached when desalting RO brines. Highlights • Commercial-scale permeate-gap membrane distillation evaluated for high salinity • Prediction models based on RSM and ANN have been developed from the experimental data. • A comparison between the two modelling tools is provided. • 3D response surfaces showing the influence of the feed salinity are presented. • The operation of MD pilot unit for desalting RO brines is optimized. [ABSTRACT FROM AUTHOR]

In the current paper, a suggested process of coupled ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) to produce isotonic solution (IS) and drinking water from coastal well water was investigated. Due to its high fouling potential, the feed water was pretreated using UF. Results showed that UF eliminates almost the totality of natural organic matter (NOM), and a relatively high portion of calcium (calcium rejection ∼75%) due to the complex Ca-NOM formed. To understand the fouling mechanism, previously developed mathematical models and equations were adopted. It was shown that the fouling mechanism for UF fits the blocking pores model. For NF, the extended model using cross-flow mode showed a slight difference compared to UF (No compression cake phase). It was concluded that, with some experimental precautions, fouling mechanism of the NF membrane used is internal pore blocking mechanism. Due to its attractive quality, the brine of NF was used to produce drinking water by RO treatment. The energy consumption of the UF-NF-RO system was investigated for different operating conditions. Finally, the permeate of the UF-NF process was compared to a commercialized IS. It was found that the two solutions revealed a remarkable similarity. However, a specific post-treatment should be added to the process to accomplish the pharmaceutical exigencies of IS. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is a thermal separation process which possesses a hydrophobic, microporous membrane as vapor space. A high potential application for MD is the concentration of hypersaline brines, such as e.g. reverse osmosis retentate or other saline effluents to be concentrated to a near saturation level with a Zero Liquid Discharge process chain. In order to further commercialize MD for these target applications, adapted MD module designs are required along with strategies for the mitigation of membrane wetting phenomena. This work presents the experimental results of pilot operation with an adapted Air Gap Membrane Distillation (AGMD) module for hypersaline brine concentration within a range of 0–240 g NaCl /kg solution. Key performance indicators such as flux, GOR and thermal efficiency are analyzed. A new strategy for wetting mitigation by active draining of the air gap channel by low pressure air blowing is tested and analyzed. Only small reductions in flux and GOR of 1.2% and 4.1% respectively, are caused by air sparging into the air gap channel. Wetting phenomena are significantly reduced by avoiding stagnant distillate in the air gap making the air blower a seemingly worth- while additional system component. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is an electrochemical ion removal technique that could offer a lower energy or more selective alternative to reverse osmosis for water treatment applications. Over a dozen CDI cell architectures have been developed, but few studies have directly compared these designs for performance metrics such as ion adsorption rate and energy efficiency. Two of the most popular cell architectures include flow-by CDI, in which a feed stream flows parallel to two charged porous electrodes, and flow-through electrode CDI, in which the feed stream flows perpendicular to the electrodes. In this study, flow-by and flow-through CDI architectures were compared using commercially available electrode materials. Experimentally observed salt adsorption capacity (SAC), average salt adsorption rate (ASAR), and charge efficiency (Λ) was then compared to theoretical models over a range of voltage conditions (0.2–1.2 V), charge cycle times (1–60 min), and flow rates (10–30 mL min - 1 ). Cell architecture affected the SAC, ASAR, Λ, electrode stability, and oxidation rates for a given electrode material. Flow-by CDI tended to have higher SAC and better charge efficiency than flow-through CDI, yet flow-through CDI demonstrated a higher ASAR, particularly for shorter half-cycle times. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) is considered as a key technology for desalination applications. It shows indeed numerous advantages compared to reverse osmosis and other desalination processes (e.g. thermal driving force, no osmotic pressure effect on membrane fluxes). Nevertheless, this technology still presents some issues, most notably due to pore wetting effects. This study proposes the use of a thin, self-standing dense membrane in place of microporous materials as a solution to avoid wetting in MD for water desalination. In a first step, a membrane contactor model is developed based on mass and energy balances and the simulations are validated using experimental results obtained on hollow fiber modules with microporous membranes. A comparative performance analysis is then achieved between a porous and a dense membrane module. A parametric study on the influence of dense membrane thickness and water permeability shows that a two fold increase in water flux, without significant impact on energy efficiency, is potentially achievable with thin and permeable dense materials compared to microporous membranes. Guidelines for the design of high-performance dense membrane modules for MD are finally proposed. [ABSTRACT FROM AUTHOR]

Osmotic microbial fuel cells (OsMFCs) combine the merits of microbial fuel cell (MFC) and forward osmosis (FO) for simultaneous contaminant removal, electricity generation, and high-quality water extraction. As an FO based technology, reverse solute flux (RSF) is one of the key challenges for its operation. Herein, RSF was converted into a positive effect on the system performance by using NaHCO 3 solution as a draw solution (DS)/catholyte. It was found that reverse-fluxed NaHCO 3 helped buffer the anolyte pH and thus enhance electricity generation, compared to the OsMFC using the NaCl DS/catholyte. At the same concentration, the NaHCO 3 DS/catholyte achieved a higher Coulomb production of 1349.2 ± 80.3 C and higher anolyte pH of 6.48 ± 0.19 than those of the NaCl DS/catholyte. At the same conductivity, the NaHCO 3 DS/catholyte exhibited better electricity generation performance with a comparable recovered water volume of 417.7 ± 13.7 mL to that of the NaCl DS/catholyte. As the NaHCO 3 concentration increased from 0.1 M to 0.75 M, the OsMFC electricity generation was enhanced due to the increased RSF from 19.2 ± 2.3 to 210.8 ± 17.5 mmol m −2 h −1 . In the anode, 92.0 ± 0.8% to 97.1 ± 0.9% of reverse-fluxed NaHCO 3 was used to neutralize protons. These results have demonstrated a new strategy that uses the bicarbonate migration driven by both a concentration gradient and electricity generation to successfully raise the alkalinity of the anolyte towards enhancing electricity generation. [ABSTRACT FROM AUTHOR]

Nineteen evolutionary algorithms, including single and hybrid optimization algorithms, are used for determining the optimum size of a hybrid renewable energy system (HRES) that is comprised of a wind turbine, a photovoltaic panel, a battery bank, and a reverse osmosis desalination unit. The main source electrical power for the reverse-osmosis desalination unit for producing fresh water is solar and wind energy, and batteries are used as back up units. Integer and continuous variables in the HRES optimization model for a remote area of Iran are considered. The optimization aims to meet the load continuously while minimizing the HRES life cycle cost subject to relevant constraints. Also, to ensure reliability, the reliability index is assessed for the loss of power supply probability. In order to achieve optimal performance, various versions well-known optimization approaches are used: particle swarm optimization, bee swarm optimization, harmony search, simulated annealing, chaotic search, and tabu search algorithm. The results show that hybrid optimization techniques provide the best performance among the considered evolutionary algorithms and that using the HRES reduces system costs and increases system reliability in general and for increasing fresh water availability. [ABSTRACT FROM AUTHOR]

Reclamation and reuse of oil and gas (O&G) waste streams is being considered as an option to alleviate stress on freshwater supplies. While limited treatment is necessary to reuse O&G wastewater (e.g., produced water (PW)) for subsequent hydraulic fracturing, high removal of organic matter and total dissolved solids (TDS) is needed to enable broader reuse (e.g., irrigation, stream flow augmentation). This study focused on the use of closed circuit desalination with nanofiltration (NF) and reverse osmosis (RO) to remove TDS and organic matter from pretreated PW. The performance and fouling propensity of three commercial NF and RO membranes was compared during the concentration of ~900 feed batches (440 h). Up to 99.6% TDS and 89% dissolved organic carbon (DOC) was removed, producing high quality permeate. Membrane characterization revealed minimal scaling and organic fouling of the three membranes, suggesting that closed circuit desalination (CCD) might be a promising method to facilitate reuse of PW. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) is increasingly becoming the dominant strategy for seawater desalination owing to its excellent desalination performance over the past few decades. It produces a considerable amount of concentrated brine, which is a threat to marine ecosystems accompanying freshwater production. Electrodialysis has been demonstrated to be a feasible process for brine treatment. In this work, a novel process called Selectrodialysis with Bipolar Membranes (BMSED) was firstly proposed for treating concentrated brine. BMSED uses bipolar membranes and monovalent selective ion exchange membranes inside the ED stack and thus combines the selectrodialysis (SED) and bipolar membrane electrodialysis (BMED) processes into a single step. BMSED can desalinate concentrated brine, selectively regenerate monovalent ions and produce acids/bases in a single route. The feasibility of the process was investigated by using different commercial membranes. The factors, including the current density and brine concentrations, were investigated. The results indicated that brine was successfully treated by using BMSED and that a HCl and NaOH solution (up to an approximate 2 mol/L concentration) with high purity was eventually produced. Therefore, BMSED is a pertinent environmentally and economically friendly process for RO concentrated brine management. [ABSTRACT FROM AUTHOR]

Although pristine graphene oxide (GO)-based membranes have previously demonstrated promising molecular separation due to their well-defined interlayer spacing, their applications in water processing operations remain limited due to the natural swelling tendency of GO in the aqueous phase which decreases separation ability. In this work, pristine GO laminate has been successfully integrated into a highly crosslinked network to produce membranes with anti-swelling behaviour and excellent desalination capability. The process of free-radical polymerisation in aqueous conditions of a GO suspension enables the formation of a GO-polymer network without covalent bonding between GO and polymer, leading to a combination of mechanical robustness, remarkable water transport properties, and an anti-swelling tendency suitable for the high-pressure operation required for reverse osmosis (RO) membrane process. The resulting GO-polymer membrane was not swollen during RO operation while it was stable under a harsh oxidising environment. It also demonstrated water flux of 33.5 L m −2 h −1 with 98.5% NaCl rejection at 10 bar when prepared by high-vacuum filtration and subsequent polymerisation of the precursor solution on to a mesoporous substrate. This methodology makes large-scalable membrane fabrication very feasible. [ABSTRACT FROM AUTHOR]

In this study, dewatered construction water was used for the first time as the feed solution in a combined pretreatment-forward osmosis process to dilute seawater (i.e. draw solution) for further desalination. It was found that at a feed solution and a draw solution flow rate of 2.2 L min −1 gave the optimum membrane flux with minimal fouling effects. The addition of a spacer in the membrane feed side was effective at low flow rates (0.8 and 1.5 L min −1 ). The feed solution was then pretreated using two methods: settling and multimedia filtration and used in the forward osmosis unit at a low flow rate of 0.8 L min −1 using a spacer at the feed side. Results revealed a significant increase in the forward osmosis membrane flux by 64.3% when multimedia filtration was carried out with a flux reduction of 7.7%. While the settling method achieved only 13.5% increase in the permeate flux and 12.5% flux reduction. The multimedia filtration process removed most of the particles that would cause fouling which resulted in an elevated and more consistent membrane flux. Results also showed that the water flux was 1.3 times higher when the membrane's active layer was facing the draw solution than when it was facing the feed solution. Cost analysis showed that forward osmosis treatment of dewatered construction water was 7.88 $.day −1 and it was slightly cheaper when the forward osmosis operates in the pressure retarded osmosis mode. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) for the treatment of concentrated brines has been limited in part by membrane fouling, resulting in subsequent flux decline and membrane wetting. This study provides new insight into the identification of fouling and scaling mechanisms and pretreatment strategies for mitigating flux decline with MD treatment of water reuse reverse osmosis concentrate (ROC). Bench-scale direct contact MD experiments were performed with untreated and pretreated ROC. Biological activated carbon (BAC), chemical water softening, or fluidized bed crystallization reactor coupled with ion exchange (FBCR-IX) were selected as pretreatment strategies to isolate the effects of organic fouling and calcium scaling. Organic and inorganic compounds were analyzed by high-performance liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS). Calcium ions were found to be the major contributor to flux decline despite the high organic content in the ROC. Minimal organic fouling is likely because the organic matter in the ROC is hydrophilic, limiting hydrophobic-hydrophobic interactions between the organics and the membrane. Furthermore, the water flux declined by 63 % after removing organic compounds by BAC pretreatment, with 60 % of the calcium mass precipitating from the solution. Whereas, the water flux remained constant after removing multivalent ions with fluidized bed crystallization. Cleaning the membrane by acid washing and temperature reversal recovered 73 % and 12 % of the water flux, respectively. The analyses outlined in this study can assist in selecting appropriate fouling and scaling mitigation strategies for water reuse ROC and a wide range of feed solutions used in MD applications. [Display omitted] • Fouling and scaling by concentrated reclaimed wastewater were investigated in MD. • Scaling was the main cause of water flux decline from concentrated reclaimed wastewater. • Calcium removal was an effective pretreatment for maintaining a high water flux. • A novel method to assess the hydrophobicity of natural organic matter is proposed. • The natural organic matter in concentrated reclaimed wastewater was hydrophilic. [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]

Desalinated seawater containing bromide ion (Br − ) blended with drinking water may produce brominated disinfection byproducts (Br-DBPs) during chlorination, which would pose a potential threat to human health when incorporated into the municipal water supply system. This study investigated the formation and speciation of twenty-one DBPs during chlorination in two desalinated seawater blends, i.e., treated drinking water blended with reverse osmosis (RO) permeate and post-treatment (PT) product water. After chlorination, the number and concentrations of DBPs formed in the desalinated seawater obviously enhanced, with chlorinated DBPs (Cl-DBPs) dominating. Sixteen DBPs were found in both RO and PT blends samples during chlorination, in which haloacetic acids (HAAs) had the highest concentration, followed by trihalomethanes (THMs) and halogen acetonitriles (HANs). When the volume of desalinated seawater in the blends was increased, the transformation from Cl-DBPs to Br-DBPs was observed for THMs and HANs, indicating that Br − was more easily incorporated into THMs and HANs than HAAs. Additionally, more Br − participated in the DBPs formation per unit dissolved organic carbon and Br-DBPs/DBPs increased, when the blended ratio of the desalinated seawater increased. The DBP-associated toxicity in the blends was estimated based on the toxicity-weighted concentration with Br-HANs as the predominant contributor, followed by Cl-HAAs. [ABSTRACT FROM AUTHOR]

In this study, the influence of reverse draw solute permeation on the rejection and prediction of NO 3 − and NH 4 + by forward osmosis (FO) were investigated. The rejection of NO 3 − and NH 4 + were experimentally compared between FO mode (active layer facing the feed water) and RO mode (hydraulic pressure applied). Under similar water fluxes, the rejection ratio of NO 3 − by HTI-ES membrane was much higher during RO than it was during FO, while the opposite was true for HTI-TFC membrane. For both membranes, the rejection of NH 4 + was higher during RO than that it was in FO. Rejection was mathematically predicted by using the solution–diffusion model with the permeability obtained from the diffusion cell. The predicted NH 4 + rejection for the HTI-TFC membrane matched well with the experimental rejection ratios. However, the model greatly overestimated the rejection ratios of NO 3 − by HTI-ES membrane and underestimated the rejection of NH 4 + by HTI-ES membrane and NO 3 − by HTI-TFC membrane. The electrostatic equilibrium at the interface and electrostatic gradient across the membrane may differ between RO, FO and diffusion cell mode, which should be considered in future FO models. [ABSTRACT FROM AUTHOR]

Increasing the surface porosity of a support membrane has been proposed as an effective way to improve the water permeability of thin-film composite (TFC) reverse osmosis (RO) membranes by reducing the diffusion pathway in the active layer. In this work, we prepared a highly porous microstructured (HPμS) support membrane with a suitable mechanical strength to enhance the water permeability of an RO membrane. The HPμS support membrane was prepared by increasing the thermodynamic instability of a 10 wt% polymer solution and thereby facilitating rapid desolvation. The rapid desolvation formed the narrow and regularly arranged pore structure in the sublayer, and we proposed the mechanism for the sublayer structure formation based on analyses of the thermodynamic properties of such a binary system. Owing to the narrow and regular structure, the HPμS support membranes showed the exceptional mechanical strength, which was comparable to the strength of support membranes used for conventional RO membranes. Also, the HPμS support membranes successfully endowed an in-house RO membrane with the performance (water permeability of 4.68 L m −2  h −1  bar −1 and NaCl rejection of 98.3%) surpassing commercial RO membranes and thin-film nanocomposite membranes recently reported in the literature. [ABSTRACT FROM AUTHOR]

In this paper, two studies are carried out related to the performance simulation and analysis of a wind-powered seawater reverse osmosis (SWRO) desalination plant prototype installed on the island of Gran Canaria (Spain). Three machine learning techniques (artificial neural networks, support vector machines and random forests) were implemented to predict the performance (pressure, feed flow rate and permeate flow rate, and permeate conductivity) of the SWRO desalination plant. Subsequently, plant operation was analysed in two different operating modes: a) constant pressure and flow rate through connection with a wind-battery microgrid, b) variable pressure and flow rate as a function of the power supplied by a stand-alone wind microgrid without energy storage. The paper supports two main outcomes. First, support vector machines and random forests are significantly (5% significance level) better predictors of the plant's performances than neural networks. Second, over one year, the operating mode that considers variable pressure and flow rate operates more continuously (higher operating frequencies and lower stop/start frequencies) than the constant pressure and flow rate alternative; however 1.2 times less permeate with 1.08 higher conductivity is produced on an annual basis. [ABSTRACT FROM AUTHOR]

This paper deals with an assessment of solar thermal-powered desalination technologies in order to identify key issues for developing market opportunities. The topic of selecting the best solar desalination solution is analysed, case by case, considering different scenes: i) Rural communities with limited fresh water demand; ii) Regions with high demands of both, water and electricity and iii) Intermediate water demands. Detailed analyses of solar thermal-driven desalination – i.e. distillation and Reverse Osmosis (RO) - in comparison to solar PV/RO are presented. The quantitative assessment performed highlights that membrane distillation systems, when fully developed, will have market opportunities at very small-capacity seawater desalination systems. Besides that, dish concentrators coupled to micro gas turbines in case of limited water demand is a promising option. A single unit could produce about 10 m 3 /h of fresh water from seawater and several units could be coupled to drive the same desalination plant. Moreover, the only stand-alone systems with market opportunities for intermediate water production are based on reverse osmosis driven by parabolic troughs or linear Fresnel concentrators by means of organic Rankine Cycles. Finally, water demands over 25,000 m 3 /d require both, a solar power plant and a reverse osmosis desalination plant. [ABSTRACT FROM AUTHOR]

Freshwater scarcity and insufficient sanitation are global urgent problems, affecting billions of people. In this review paper, the process of desalination powered by wave power has been investigated as a potential sustainable solution to water shortage. The different desalination techniques suitable for this type of combined system, i.e. reverse osmosis, electrodialysis and mechanical vapor compression, have been outlined, as well as the different wave energy converters possible to power the desalination process, i.e. oscillating water columns, oscillating bodies (wave activated bodies) and overtopping systems. Some necessary considerations for this type of project are identified. The different wave power/desalination projects and how they have proceeded are presented. The most common design of a wave energy and desalination system includes a wave activated body to pressurize seawater; the seawater flows through a reverse osmosis membrane, resulting in freshwater. Some successful (freshwater producing) wave energy/desalination projects were identified: Delbuoy, the oscillating water column in Vizhinjam, CETO Freshwater, SAROS and Odyssée. It is concluded that wave power and desalination can be combined in a sustainable and autonomous system, generating freshwater from the ocean waves. However, questions regarding cost of produced water, variations in power production due to intermittency and environmental effects still remain. [ABSTRACT FROM AUTHOR]

Many remote communities lack access to reliable clean water and electricity, leading to the development of renewable powered desalination systems. To reduce costs of energy storage, many of these systems operate intermittently. However, the impact of intermittent operation on membrane fouling is still not well understood. This article presents an experimental investigation of the effect intermittent operation characteristic of renewable powered desalination systems has on membrane performance. Three operating conditions were investigated: use of anti-scalant or no anti-scalant; intermittent or continuous operation; and rinsing with 8 L of lab-grade clean water prior to shut-down or no rinsing. The results show intermittent operation increases the rate of membrane scaling. However, maintenance with rinsing prior to shut-down maintains higher membrane permeability than without rinsing. Membrane autopsy using scanning electron microscopy showed the fewest scale deposits for intermittent operation with anti-scalant and rinsing. On the sixth day of operation, the average normalized permeability declined to 87 ± 9% for intermittent operation with anti-scalant and with rinse. All other operating conditions declined to nearly zero with the exception of continuous operation with anti-scalant, which declined to 30 ± 4%. These experimental results will be used in future work to develop robust design algorithms for renewable powered desalination systems. [ABSTRACT FROM AUTHOR]

The security of recycled water quality in potable reuse can be enhanced by improving the credibility of reverse osmosis (RO) treatment for the removal of trace organic chemicals (TOrCs). This study evaluated the potential of online monitoring of N -nitrosodimethylamine (NDMA) before and after RO treatment as a surrogate indicator for TOrC removal by RO. This pilot-scale study monitored NDMA concentrations in RO feedwater (ultrafiltration-treated wastewater) and RO permeate every 22 min using novel online NDMA analyzers—high-performance liquid chromatography followed by photochemical reaction and chemiluminescence detection. NDMA rejection by RO varied considerably in response to changes in operating conditions (permeate flux and feedwater temperature). A high linear correlation between NDMA rejection and the rejection of six other TOrCs was observed. The linear correlation was also identified for an RO membrane damaged with chlorine. The correlation between another potential surrogate indicator (conductivity rejection) and TOrC rejection was relatively low. NDMA, which is the smallest compound among regulated TOrCs, revealed rejections lower than the other TOrCs, indicating that NDMA rejection can be a conservative surrogate indicator capable of predicting changes in TOrC removal. [ABSTRACT FROM AUTHOR]