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The fouling potential of transparent exopolymer particles (TEP) was evaluated to reveal its role in the biofouling mechanism of reverse osmosis (RO) membrane process. A methodology to determine the fouling potential of TEP was systematically developed based on cake filtration theory. The resulting cake fouling index of TEP (CFI TEP ) was then correlated to initial bacterial deposition observed in RO biofouling tests. Alginic acid was employed to simulate TEP and Pseudomonas aeruginosa PA14 was inoculated for biofouling test. The results showed that the fouling propensity of TEP could be assessed by cake fouling potential of particulate TEP (>0.45 μm). Furthermore, the analysis of biofouled RO membranes indicated that bacterial deposition on RO membranes was enhanced significantly with increasing the cake fouling potential of TEP (i.e., CFI TEP ). This work demonstrated the importance of TEP at the initial stage of biofilm formation, suggesting TEP control by pretreatment for mitigating biofouling in RO applications. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) and industrial processes are driving the demand for CO 2 stripping from water. Membrane contactors are considered a favorable solution to the conventional challenges of CO 2 stripping from water, such as inefficiency and high space occupancy. However, the factors affecting membrane contactor performance have not been systemically investigated in the context of efficient CO 2 stripping. This study analyzed the factors affecting the membrane contactors for the CO 2 stripping process based on experiments and theoretical modeling. The factors are classified according to advection (e.g., liquid flow rate), diffusion (e.g., vacuum pressure and pH), and membrane (e.g., long-term operation and arrangement). A high liquid flow rate increased the CO 2 stripping flux, whereas it decreased the CO 2 removal efficiency. At vacuum pressure, CO 2 stripping depended on the vacuum pressure but it was not effective in the air-combination mode. It is also important to maintain pH 5 as pH significantly affects the diffusion. In the long-term experiment, membrane fouling and pore swelling were not observed to cause performance degradation. Further, parallel and series designs for membrane contactors were compared, the parallel design exhibits superior CO 2 stripping performance. This study provides strategies for using membrane contactors for efficient CO 2 stripping. [Display omitted] • Membrane contactors for CO 2 stripping investigated by experiments and modeling. • Liquid flow rate controlled to enhance advection in the CO 2 stripping process. • Effect of pH condition and vacuum pressure examined for effective diffusion. • A long-term experiment used to analyze membrane performance degradation. • Different membrane arrangements compared to improve CO 2 stripping performance. [ABSTRACT FROM AUTHOR]

Membrane distillation (MD) demonstrates enormous potential to treat high salinity water due to its unique rejection mechanism; however, fouling and wetting continue to be major technical challenges in high recovery conditions due to the concentration of contaminants. Electrical repulsion with electrically conductive membranes shows promise to address fouling and wetting, as it prevents contaminants from accessing the membrane surface. Improvements to electrical conductivity and hydrophobicity occurred using a multi-layered single-wall carbon nanotube (SWCNT) coating on a polyvinylidene fluoride (PVDF) membrane without MD performance degradation. These results were identified by analyzing cyclic voltammetry, electrochemical impedance spectroscopy, and direct contact angle. An experimental and theoretical evaluation on the feasibility of using electrical repulsion with the SWCNT/PVDF membrane to address the fouling and wetting of the MD was carried out. This evaluation was undertaken using a series of fouling/wetting experiments and repulsive force calculations. The results confirmed that fouling and wetting in the MD process were effectively mitigated by electrical repulsion with the SWCNT/PVDF membrane, allowing more than twice the operation time without any performance degradation; this was despite the low applied voltage and long-term operational conditions. The experimental observations demonstrated that electrical repulsion with the SWCNT/PVDF membrane potentially facilitates sustainable MD operations with high recovery conditions. [Display omitted] • Electric repulsion with SWCNT modification was investigated. • SWCNT modification increased hydrophobicity and conductivity of MD membrane. • Electric repulsion has effectively mitigated fouling and wetting with low voltage applied. • Fouling and wetting mitigation mechanism was examined by calculating repulsive force. • SWCNT/polyvinylidene fluoride membrane was stable in long-term with low voltage. [ABSTRACT FROM AUTHOR]

This study elucidates the physicochemical mechanisms of monovalent and multivalent inorganic scaling and suggests an optimal cleaning strategy for efficient membrane distillation (MD) operation. Three distinct stages of MD inorganic scaling were clearly identified by i) experimentally measuring transient flux, ii) rejection behavior resulted from the deposition of a scale, and iii) SEM-EDX analysis of the membrane. During stage 1, no scale was found over the membrane surface showing almost stable water flux and permeate conductivity. In stage 2, the onset of inorganic scaling resulted in the deposition of scaling on some parts of the membrane surface, partially covering the membrane pores, which lead to a sudden reduction in the water flux despite a steady solute rejection. However, as scaling expands into the pore in final stage 3, the permeate conductivity increased, indicating a reduction in rejection. Then, the pores were completely blocked, and the water flux reached almost zero. To simulate this scaling formation more fundamentally, the saturation index (SI) and supersaturation (S) concepts were introduced. The type and timing of scaling were successfully predicted by the SI value, and the amount of scaling was accurately estimated by the S value. Moreover, through the analysis of this physicochemical mechanism of inorganic scaling, an optimal cleaning strategy for sustainable MD operation was proposed. [Display omitted] • The physicochemical mechanism of inorganic scaling was identified as three distinct stages. • The scaling formation on MD performance was confirmed at each stage. • The scaling formation was simulated by using supersaturation (S) concepts. • The type and timing of scaling were predicted by the proposed saturation index. • A cleaning strategy and fouling mechanism for sustainable MD operation were elucidated. [ABSTRACT FROM AUTHOR]

Due to the shortage of freshwater around the world, seawater is becoming an important water source. However, seawater contains a high concentration of bromide that can form harmful disinfection by-products during water disinfection. Therefore, the current seawater reverse osmosis (SWRO) has to adopt two-pass reverse osmosis (RO) configuration for effective bromide removal, increasing the overall desalination cost. In this study, a bromide selective composite electrode was developed for membrane capacitive deionisation (MCDI). The composite electrode was developed by coating a mixture of bromide selective resin and anion exchange polymer on the surface of the commercial activated carbon electrode, and its performance was compared to that of conventional carbon electrode. The results demonstrated that the composite electrode has ten times better bromide selectivity than the conventional carbon electrode. The study shows the potential application of MCDI for the selective removal of target ions from water sources and the potential for resource recovery through basic modification of commercial electrode. [Display omitted] • Bromide selective electrode was prepared using bromide selective resin for MCDI application. • Electrode showed significant bromide selectivity from a mixture of multiple anions. • Commercial carbon electrode can be modified to improve ion-selectivity. • MCDI can be a useful technology for target ion removal and resource recovery. [ABSTRACT FROM AUTHOR]

Transparent exopolymer particles (TEPs), often massively produced from algal blooms, are considered one of the most difficult foulants in membrane-based desalination processes and contribute significantly to membrane biofouling. This study explored the potential application of a UV-activated peroxymonosulfate (UV/PMS) system for the mineralization of TEP using alginate as a model. The effects of salinity in the form of chloride ions on the removal of organics were investigated, and the reaction mechanisms were postulated. In addition, the scavenging effect of the co-presence of cations and anions with chloride ions was examined. The results indicated that 100% TEP mineralization could be achieved in freshwater when a PMS concentration above 0.25 mM was added. However, the presence of chloride retarded the removal efficiency by approximately 25%, with more severe retardation observed in the presence of chloride with bromide. This was ascribed to the generation of less reactive and more selective halogen species. Furthermore, approximately 44% organic mineralization was observed when this system was applied to seawater, implying its feasibility as a pretreatment unit in membrane-based desalination. [Display omitted] • TEP removal by UV/PMS was fundamentally investigated using alginate. • UV/PMS can completely mineralize TEP in freshwater. • TEP mineralization was retarded slightly by chloride, but significantly by bromide. • Reactive bromine species have lesser reactivity compared to reactive chlorine species. • UV/PMS can be a feasible pretreatment to control TEP in SWRO desalination. [ABSTRACT FROM AUTHOR]

[Display omitted] • The TOrC rejection mechanisms of polyamide RO/NF membranes were elucidated. • Solute properties that affect the TOrC rejection of RO/NF membranes were analyzed. • Comprehensive correlational analysis identified the best size-exclusion indicator. • The role of specific interactions in TOrC rejection was extensively identified. • Advanced membranes developed to improve TOrC removal performance were outlined. Trace organic compounds (TOrCs) have emerged as a critical concern for securing high-quality and safe water resources. Advanced water treatment using reverse osmosis (RO) and nanofiltration (NF) membranes has proven to be a promising technology for removing TOrCs. In this context, identifying the TOrC rejection mechanisms of RO/NF membranes is of paramount importance for the effective design of membrane processes and materials to improve the efficiency of TOrC treatment. However, the characteristic TOrC removal mechanisms of RO/NF membranes remain unclear, presumably due to the vast differences in the membrane structures and the limited number of TOrCs that have been investigated in past studies. Hence, the present article comprehensively reviews, analyzes and elucidates TOrC rejection mechanisms by characterizing key rejection-governing solute parameters for fully-aromatic polyamide-based tight RO/NF membranes (MWCO ≤ 200 Da) using the published rejection data for a large number of TOrCs (>300). We found that size exclusion and adsorption (and subsequent partitioning) via specific interactions play a dominant role in TOrC rejection by elucidating the key rejection-governing solute characteristics. In addition, this paper outlines up-to-date research on the fabrication of advanced membranes designed to improve TOrC removal performance. Based on this review, we propose future directions for reliably predicting and effectively enhancing the TOrC separation performance of RO/NF membranes. [ABSTRACT FROM AUTHOR]

Analytical technologies for polymeric membranes, including positron annihilation lifetime spectroscopy (PALS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), were employed to understand the origin and harmful effects of thin film composite (TFC) reverse osmosis (RO) membrane compaction. Although no variation in water flux exceeding 10% from the initial flux was observed under all compaction pressures, the hydraulic pressure induced by the high-pressure pump caused a rapid contraction of the free volume and thickness of the TFC RO membrane. In particular, due to the viscoelastic polymer properties of the active layer, a reduction of approximately 15% free volume and 48% thickness was observed at a compaction pressure of 60 bar. Consequently, the analytical procedures can provide a better understanding of membrane compaction during pressurized membrane processes and strategic development to reduce the harmful effects of membrane compaction. [Display omitted] • TFC RO membrane compaction was fundamentally analyzed by PALS and ToF-SIMS. • Compaction at high applied pressures reduced water permeability in the RO membrane. • The greatest effect of compaction was observed in the active layer of RO membrane. • The applied high pressure reduced the free volume and thickness of the active layer. • Proposed analyses could estimate the harmful effects on the RO membrane compaction. [ABSTRACT FROM AUTHOR]

Flow-electrode capacitive deionization (FCDI) is a new electrochemical-based desalination technology that addresses the limitations of preceding CDI processes through the use of a stationary carbon electrode and ion-exchange membrane. As with conventional CDI configurations, non-Faradaic reactions (i.e., ion electrosorption) of the electric double layer model is the principal ion separation mechanism of FCDI. This technology also offers the unique ability for continuous ion/salt separation by circumventing constraints with electrode saturation. This paper reviews recent advances in FCDI, discusses the feasibility and applicability of this technique, and suggests potential niche applications for saline water/wastewater treatment and resource recovery. Additionally, it also critically discusses factors that deteriorate FCDI performance, operating conditions, process energy efficiency, and optimization of the electrode, electrolyte, and cell design. The insights from this review will shed light on directions for future FCDI research and inform the implementation of FCDI technology. Unlabelled Image • Comprehensive review of recent advances in flow-electrode capacitive deionization (FCDI) • FCDI process optimization to improve desalination efficiency • Critical energy analysis in comparison with existing desalination technologies • FCDI in desalination, softening, nutrient recovery, and toxic metal removal • Future research directions for expanding practical application of FCDI [ABSTRACT FROM AUTHOR]

A high-performance and durable thin-film composite (TFC) pressure retarded osmosis (PRO) membrane was fabricated using a polyvinyl alcohol (PVA)-coated polyethylene (PAPE) support via toluene-assisted interfacial polymerization (TIP). The PVA coating uniformly hydrophilized the extremely thin (~8 μm) polyethylene (PE) support with a highly porous structure while marginally deforming the support structure, resulting in a very low structural parameter (~235 μm). The TIP process produced a polyamide selective layer with remarkably higher water permeability (~8.78 L m−2 h−1 bar−1) than those of commercial HTI membranes (0.56–1.40 L m−2 h−1 bar−1). Furthermore, despite its extreme thinness, the PAPE-supported TFC (PAPE-TFC) membrane had higher mechanical properties than the commercial membranes owing to the superior mechanical strength of its PE support. Hence, the PAPE-TFC membrane achieved an unprecedentedly high power density of ~35.7 W m−2 at an applied pressure of 20 bar using a deionized water feed solution and a 1.0 M NaCl draw solution, which significantly outperformed commercial and any other reported lab-made PRO membranes. The mechanically robust PAPE-TFC membrane also enabled stable long-term PRO operation under high pressure conditions. Image 1 • PRO membranes were fabricated using polyvinyl alcohol-coated PE (PAPE) supports. • The very thin and highly porous structure of hydrophilic PAPE supports lowered ICP. • Toluene-assisted interfacial polymerization formed a highly permeable PA layer. • The prepared PAPE-TFC membrane showed an unprecedentedly high maximum power density. • The PAPE-TFC membrane had excellent mechanical strength and long-term stability. [ABSTRACT FROM AUTHOR]

An osmotic dilution process of hybrid forward osmosis (FO) and reverse osmosis (RO) was applied at pilot-scale to integrate wastewater treatment with seawater desalination in a municipal wastewater treatment plant. The aim of this study is to expand the understanding of multiple FO fouling indexes (i.e., MFI-UF and ORI) to not only obtain insight on fouling characteristics of the FO process but also optimize the operation of the osmotic dilution process. The correlation between the fouling indexes and performance of the FO membrane (i.e., transmembrane inlet pressure (TMIP), differential pressure (DP)) was first validated based on the operation data from the seven-month pilot run. MFI-UF was then selected for measuring the fouling potential according to the pretreatment process (or source water), whereas ORI was obtained for optimizing the cleaning protocol of the FO process to support the stable operation of the FO plant. The sensitivity analysis of the seasonal effect verified the correlation between MFI-UF and FO performance. The results of this study are expected to provide practical insight and technical guidelines to FO based plant engineers/operators. Image 1 • Applicability of multiple FO fouling indexes was validated at pilot scale. • Long-term performance was assessed by adopting different pretreatment strategies. • A close relationship between MFI-UF and FO ΔDP was observed. • ORI was able to predict the FO TMIP precisely. • MFI-UF and ORI can be applied as plant–assistance criteria for FO process. [ABSTRACT FROM AUTHOR]

In this study, the impacts of three feed spacer design parameters; thickness, porosity and architecture, on the cleaning efficiency of ultrafiltration (UF) membranes were studied, both in backwash and relaxation cleaning modes, using sodium alginate solution dosed with CaCl 2 as the process feed. Both commercial, net-type spacers and 3D-printed spacers based on triply periodic minimal surfaces (TPMS) architectures were utilized in the study. Increased spacer thickness and porosity were found to increase the cleaning resistance of the membrane, while TPMS spacers were found to yield a lower cleaning resistance than net-type spacers, even with the latter being thicker. The root causes of these observations were analyzed based on resistance analysis of the fouling layer on the membranes. To do that, overall, residual, reversible and irreversible fouling resistances were quantified at the end of a 20-cleaning cycle test. Statistical correlations were then established between these resistances and spacer properties. The results showed that the consequential impacts of spacer design on the shear stresses, created by the feed flow on the fouling layer, underscore the observed fouling mechanism and the consequent cleaning efficiency. The spacer design can impact these shear stresses through its hydraulic diameter and spacer-membrane contact area. When the spacer design leads to lower shear stresses, a cake filtration mechanism prevails, a more irreversible fouling occurs and more challenging cleaning becomes. A recently published work on combined intermediate pore blockage and cake filtration model for fouling was used to construe these observations. • Impacts of spacer properties on membrane backwash and relaxation is assessed. • Net-type spacers and triply periodic minimal surface (TPMS) spacers studied. • Statistical correlation between spacer design and fouling resistances determined. • Effect of spacer architecture on pore blockage and irreversible fouling evaluated. • Relationship between spacer design and fouling mechanism established. [ABSTRACT FROM AUTHOR]

Despite significant advances in reverse osmosis (RO) applications, membrane fouling is an inevitable problem that reduces the quantity and quality of produced water and is associated with reducing the energy efficiency of the entire system. The aim of this study was to expand our understanding of the modified fouling index (MFI), which is a reliable tool used to provide insight into the fouling characteristics of the RO process in advance. The applicability of MFI to predict RO membrane performance was verified using a 50 m3/day pilot-scale ultrapure water (UPW) production plant study. The correlation between MFI and RO membrane performance (i.e., ∆(differential pressure)) was well validated based on seven months of pilot operation data. MFI-UF flux-10kDa was selected as a proxy for the fouling potential measurement according to the target process (or source water) to support the stable operation of UPW plant applications. Case studies including sensitivity analyses and electrochemical deionization (EDI) concentrate reclamation have verified the intimate correlation between the MFI and RO performance. The results from the current study are expected to provide practical insight and technical guidelines for RO-based plant engineers/operators. Unlabelled Image • MFI-UF was applied, for the first time, as a diagnostic tool for UPW production. • Fouling potential measured by MFI-UF was closely related to the quality of RO permeate. • MFI-UF flux-10kDa performed well for fouling potential simulation in UPW system. • MFI-UF flux-10kDa showed intimate correlation with RO ΔDP after 1 day operation. • This work provides practical insight and technical guidelines for RO based plant. [ABSTRACT FROM AUTHOR]

In this study, we report on a solar membrane distillation (MD) system with a 5-stack Ti/MgF 2 solar absorber adapted as a heat source under actual weather conditions. The 5-stack Ti/MgF 2 solar absorber showed light absorption of 85% over the wavelength range from 0.3 to 2.5 μm. This consequently induced greater heat and a two-fold greater water heating capability up to 80 °C for water in a closed water tank without insulation under a 1-sun illumination. The enhanced solar absorption of the Ti/MgF 2 solar absorber showed a 12% improvement in permeate flux of the integrated MD system compared with a system without a solar absorber. Under actual weather conditions, the solar DCMD system with the Ti/MgF 2 solar absorber successfully produced distillate water in the range of 0.51–4.78 L/m2·day depending on weather conditions. Despite unfavorable solar irradiance conditions in autumn, the integrated DCMD system with the Ti/MgF 2 solar absorber proved superior to a conventional commercial evacuated-tube solar collector in terms of daily production of distillate water and solar energy requirements for certain amounts of distillate. Unlabelled Image • A solar DCMD system with a 5-stack Ti/MgF 2 solar absorber was performed. • A Ti/MgF 2 solar absorber exhibited enhanced solar-thermal performance. • Distillate water successfully produced under actual weather conditions. • Compatibility to commercial solar collector was evaluated. [ABSTRACT FROM AUTHOR]

A new meshed tube filtration (MTF) process was developed and assessed as a low energy-consuming pretreatment process that withstands algal blooms (i.e., red tide). This process can potentially replace the dissolved air flotation (DAF) process in typical seawater reverse osmosis (SWRO) desalination plants. Two marine microalgae species, namely C. polykrikoides and T. suecica , were first cultivated and then utilized to simulate algal bloom conditions in the lab-scale filtration experiments. The algal matter was coagulated and circulated by aeration in the MTF system that was filled with cylindrical polypropylene meshed tubes with ciliary ends and had the ability to capture coagulated algae in an effective manner. The efficiency of the MTF process to remove algal cells was significantly enhanced by optimizing the coagulant dose and the aeration rate. In order to further verify the MTF performance, DAF experiments were conducted, under similar conditions, for the comparison of algal removal effectiveness and energy consumption rates. The results showed high removal rates of algal cells as well as turbidity for MTF, although only a limited reduction of algal organic matter (AOM) was observed. When DAF was operated at energy consumption levels equivalent to MTF, its algae removal rate was lower than that of MTF. Furthermore, under optimal operating conditions, MTF consumed approximately one-third of the energy needed for DAF operation, mainly due to the fact that MTF requires less aeration. For future improvements in the AOM removal process, an energy-efficient pretreatment process could be realized for SWRO desalination facilities facing potential algal blooms. Unlabelled Image • Novel meshed tube filtration (MTF) was developed for algal bloom control in SWRO. • C. polykrikoides and T. suecica were tested as model marine microalgae species. • Coagulant dose and aeration rate were optimized for enhancing algal removal by MTF. • Turbidity and cell removal rates of MTF were comparable to dissolved air flotation. • MTF required only 33–39% of the energy needed for dissolved air flotation. [ABSTRACT FROM AUTHOR]

A NO 3 −—selective carbon electrode coated with an anion-selective polymer with polystyrenic macroporous nitrate—selective A520E resin particles (in chloride form; particle size: 300–1200 μm) was fabricated for desalination of municipal wastewater and NO 3 − recovery during membrane capacitive deionization (MCI). Several issues, such as electrosorption/regeneration efficiency, selectivity of NO 3 −, and removal from real wastewater, were addressed to demonstrate the suitability of coated electrodes. The NO 3 −—selective electrode induced better electrosorption than the conventional MCDI, whereas its salt adsorption capacity was lower than that of the ion-exchange (IX) layer only coated one. The mole fraction of NO 3 − adsorption kept increased even after saturation by replacing Cl− adsorbed on the resin coating layer. However, the desorption efficiency of NO 3 − was retarded as it was exchanged with Cl− and temporarily intercepted in the resin of the IX layer, during ion migration towards the bulk brine solution. 81.5% of NO 3 − was removed with better NO 3 − selectivity from real municipal wastewater, and a high concentration of NO 3 − brine was obtained through successive operation. However, the poorly selective NO 3 − desorption, which limits its enrichment due to the reverse ionic-strength gradient induced by the high concentration brine, needs to be mitigated to prove its effective recovery. Unlabelled Image • A NO 3 —selective electrode was developed for enhanced NO 3 − recovery. • The AC electrode was coated with an IX polymer solution containing A520E resins. • The coated electrode kept collecting NO 3 − even after the electrode reached saturation. • The selective resins embedded in the coating layer increased electric resistance. • NO 3 − was shortly trapped at the IX layer and slowly repelled from the electrode. [ABSTRACT FROM AUTHOR]

Seawater reverse osmosis (SWRO) is usually combined with brackish reverse osmosis (BWRO) to improve the water quality in seawater desalination; however, this configuration often results in high energy consumption. Consequently, membrane capacitive deionization (MCDI) has been suggested as a lower energy alternative technology, but cyclic operation within the cell (i.e., discontinuous operation of ad/desorption) is a main disadvantage. On the other hand, flow electrode capacitive deionization (FCDI) can be continuously operated by using a flow electrode. In this study, the feasibility of a SWRO-FCDI system was examined by using a suitable electrolyte in the flow electrode: seawater or SWRO concentrate. In addition, by employing a selective ion exchange membrane (IEM), the FCDI was able to selectively remove monovalent ions rather than divalent ions, unlike BWRO, thus producing a final product water containing divalent ions, which is more suitable for corrosion control in the subsequent pipe distribution systems. As a result, the remineralization process can be minimized. To test the SWRO-FCDI concept, actual SWRO permeate was first treated in a single mode with an electrolyte comprising real seawater in a flow electrode, and the feasibility of long-term operation was proven by batch-mode, which allowed the optimization of the FCDI active area. Unlabelled Image • The feasibility of a SWRO-FCDI system for low-energy desalination was examined. • Simulated seawater and SWRO concentrate were tested as electrolytes in FCDI. • FCDI removed divalent ions over monovalent ions with 30% higher efficiency. • Actual SWRO permeate was treated by FCDI using with a real seawater electrolyte. • In the batch mode, over 95% removal efficiency was achieved at a 1.3 kWh/m3. [ABSTRACT FROM AUTHOR]

In this study, the FO/crystallization/RO hybrid process was analyzed comprehensively, including experimentation, modeling, and energy and cost estimation, to examine and improve its feasibility to seawater desalination. A new operating strategy by heating the FO process to 45 °C was suggested, and a detailed process design was conducted. A comparative analysis with the conventional seawater reverse osmosis (SWRO) process was performed in terms of specific energy consumption (SEC) and specific water cost (SWC). The hybrid process can produce fresh water with SWC of 0.6964 $/m3, electrical SEC of 2.71 kWh/m3, and thermal SEC of 14.684 kWh/m3. Compared to the conventional SWRO process (SWC of 0.6890 $/m3 and electrical SEC of 2.674 kWh/m3), the hybrid process can produce water with comparable cost and energy consumption. An economic feasibility study that utilized the waste heat and the developed FO technology was also carried out to investigate future developments of the hybrid process. The SWC can be reduced to 0.6435 $/m3 with free waste heat energy. The permeate water quality of the hybrid process was about half that of the conventional SWRO process on molar basis. The results revealed that the FO/crystallization/RO hybrid process can be utilized as a competitive process for seawater desalination with high recovery and high water quality. Image 1 • New operation mode of FO/crystallization/RO hybrid process suggested. • Applicability of FO/crystallization/RO hybrid process experimentally confirmed. • This hybrid process confirmed as cost-competitive for seawater desalination. • Utilizing waste heat, water produced at 7% lower cost than that with SWRO. • Permeate water quality approximately half of the conventional SWRO on molar basis. [ABSTRACT FROM AUTHOR]

• Critical review of energy consumption of seawater reverse osmosis plants. • Collection of more than 70 datasets for large-size seawater reverse osmosis plants. • Investigation of trends in the application of seawater reverse osmosis plants. • Analysis of factors associated with energy consumption of seawater reverse osmosis. • Future directions to reduce energy consumption of seawater reverse osmosis plants. High specific energy consumption (SEC) is the main barrier for the expansion of seawater reverse osmosis (SWRO). Therefore, the main objective of current SWRO research is to lower the SEC of SWRO plants. However, SEC of SWRO plants has not been systemically explored or analyzed, despite the need for information to develop appropriate strategies to reduce SEC. Therefore, this study aims to review and analyze SWRO plants for a comprehensive understanding of their SEC. First, trends in SWRO application are investigated using more than 70 datasets on large-scale SWRO. The analysis explains the increasing number of large-size SWRO plants, the SEC reduction by isobaric energy recovery devices (ERDs), and the use of different SWRO configurations to meet the energy and quality requirements. Factors associated with SEC (i.e. , feed conditions, target conditions, and equipment efficiency) are also analyzed. High salinity increases energy demand, whereas the temperature effect on energy consumption is not entirely clear. High-efficiency ERDs and pumps can reduce SEC, but overall SEC cannot be explained by these factors alone. SEC is also affected by target water quality and quantity. Moreover, specific SWRO designs can improve the system to efficiently achieve the established goals. Furthermore, future directions to develop low-energy SWRO plants are discussed. [ABSTRACT FROM AUTHOR]

Flow-electrode capacitive deionization (FCDI) is a promising technology for sustainable water treatment. However, studies on the process have thus far been limited to lab-scale conditions and select fields of application. Such limitation is induced by several shortcomings, one of which is the absence of a comprehensive process model that accurately predicts the operational performance and the energy consumption of FCDI. In this study, a simulation model is newly proposed with initial validation based on experimental data and is then utilized to elucidate the performance and the specific energy consumption (SEC) of FCDI under multiple source water conditions ranging from near-groundwater to high salinity brine. Further, simulated pilot-scale FCDI system was compared with actual brackish water reverse osmosis (BWRO) and seawater reverse osmosis (SWRO) plant data with regard to SEC to determine the feasibility of FCDI as an alternative to the conventional membrane processes. Analysis showed that FCDI is competent for operation against brackish water solutions under all possible operational conditions with respect to the BWRO. Moreover, its distinction can be extended to the SWRO for seawater conditions through optimization of its total effective membrane area via scale-up. Accordingly, future directions for the advancement of FCDI was suggested to ultimately prompt the commercialization of the FCDI process.