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Fouling indices have been extensively investigated in membrane applications, for evaluating the feed-water fouling potential and providing guidelines for the pretreatment process. For the past few decades, the silt density index (SDI) has been adopted as the most mature fouling index in many seawater reverse osmosis desalination plants. Recently, a modified fouling index (MFI) has gained attention since it compensates for the defects of the SDI. Its publication by ASTM Standard promoted more settlements in practical applications. To gain insight into the use of a membrane-fouling index, this paper reviewed SDI and MFI applications in laboratory-, pilot-, and plant-scale verifications, under conditions likely to be encountered in seawater desalination. The main focus was on the historical development of the fouling indices from theoretical basis to full-scale applications and the identification of future opportunities to expand their reliability in real applications. In particular, the practical implications associated with plant operation were documented to support an in-depth understanding of the MFI values. [ABSTRACT FROM AUTHOR]

The increasing impact of climate change has worsened drought conditions, leading to a surge in the demand for seawater desalination. However, current seawater reverse osmosis (SWRO) desalination technologies are not energy-efficient for handling the high-salinity, high-temperature, and high-turbidity seawater found in the Arabian Gulf. Therefore, a pilot-scale SWRO desalination plant was established to evaluate the new desalination technologies. The pilot plant tested high-performance SWRO membranes, meshed tube filtration (MTF) as a low-energy pretreatment for the high turbidity induced by algal blooms, and membrane capacitive deionization (MCDI) to improve permeate quality. The high-performance SWRO membrane demonstrated exceptional salt rejection and produced permeate quality in the range of 250–455 mg/L from the feed with salinities of 47,500–53,500 mg/L. MTF was effective in controlling turbidity, and the energy consumption was reduced by 77 % compared to the existing pretreatment process. Furthermore, MCDI exhibited similar levels of energy efficiency as brackish water reverse osmosis and may have the potential for future deployment by enhancing process development. Based on the pilot plant results, it is expected that a 100,000–200,000 m3/d SWRO desalination plant will have a specific energy consumption of 3.11–3.13 kWh/m3 for final product water quality at or below 200 mg/L. [Display omitted] • A pilot-scale SWRO desalination plant was used to investigate low-energy technologies. • Developed SWRO membranes significantly decreased feed TDS under normal pressure. • MTF reduced feed turbidity effectively and consumed lower energy compared to DAF. • MCDI demonstrated potential as a substitute for BWRO in two-pass RO systems. • The SEC of SWRO desalination plants was evaluated as 3.11 kWh/m3 through scale-up. [ABSTRACT FROM AUTHOR]

Abstract Internally staged design (ISD) was introduced as a method to lower front reverse osmosis (RO) element fluxes, yielding operational benefits. Systematic selection of the best ISD combinations has not been conducted as it is dependent on operating conditions (i.e., RO recovery and average flux). This study aimed to optimize seawater reverse osmosis (SWRO) operations using ISD for better product water quality and energy efficiency. A total of 36 ISD combinations were configured with three commercial SWRO membranes and systematically examined under varying operating conditions which were simulations of typical SWRO operation. A Pareto-optimal front, a non-dominated feasible solution set, was created to understand the tradeoff relationship between permeate quality and specific energy consumption while considering all parameters. The Pareto-optimal front was classified into five phases, and an analysis of phase changes provided optimal parameter settings for SWRO operation. However, the occurrence of colloidal fouling altered optimal ISD combinations on the Pareto-optimal front. Particularly, when SWRO membranes were fouled at high-recovery and -flux conditions, ISD combinations employing three different membrane types exhibited superior performance in terms of energy efficiency. With these results, the best SWRO operation was suggested depending on its performance requirements, and the advantages of ISD were further delineated. Graphical abstract fx1 Highlights • SWRO with ISD was optimized to achieve better water quality and energy efficiency. • Efficient SWRO performance control was examined by Pareto-optimal front analysis. • Colloidal fouling changes the best ISD combinations on the Pareto-optimal front. • ISD with three SWRO membrane types is feasible at high-recovery and -flux operations. • The optimal SWRO operation mode is proposed based on its performance requirements. [ABSTRACT FROM AUTHOR]

Membrane-based desalting processes including reverse osmosis (RO), forward osmosis (FO), and membrane distillation (MD) were systematically evaluated for concentrating RO brine. Basic characteristics of membrane processes were first examined. Commercial polyamide RO exhibited higher water and lower salt permeability coefficients than cellulose FO membrane. However, salt rejection by FO seemed to be higher than RO primarily due to the hindrance of reverse draw solute flux. The water flux of MD comparable to RO was obtained when temperature gradient was more than 20–30°C. The applicability of RO, FO, and MD was further tested with real brine obtained from full-scale RO plant processing brackish water. Results demonstrated that water flux was not significantly reduced in MD, while severe flux decline was observed in both RO and FO at high recovery. To elucidate major causes of different flux behaviors, the fouled membrane surfaces were analyzed by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction. Foulant analysis suggested that CaCO3scaling occurred particularly at high water recovery, which was in good agreement with water quality simulation. CaCO3scaling, however, had only small impact on flux behavior in MD. From these findings, MD could be suggested as the best option for concentrating industrial RO brine if low-grade heat (below 50–70°C) is available. [ABSTRACT FROM PUBLISHER]

The use of membrane-based technology has evolved into an important strategy for supplying freshwater from seawater and wastewater to overcome the problems of water scarcity around the world. However, the presence of natural organic matter (NOM), including humic substances affects the performance of the process. Here, we present a systematic report on the mineralization of humic acid (HA), as a model for NOM, in high concentration of salts using the ultraviolet light-activated peroxymonosulfate (UV/PMS) system as a potential alternative for HA elimination during membrane-based seawater desalination and water treatment processes. Effects of various parameters such as PMS concentration, solution type, pH, anions, and anion-cation matrix on HA mineralization were assessed. The results show that 100%, 78% and 58% of HA (2 mg/L TOC) were mineralized with rate constants of 0.085 min−1, 0.0073 min−1, and 0.0041 min−1 after 180 min reaction time at pH 7 when 0.5 mM PMS was used in deionized water, sodium chloride solution (35,000 ppm) and synthetic seawater, respectively. The reduced efficiency under saline conditions was attributed to the presence of anions in the system that acted as sulfate and hydroxyl radicals' scavengers. Furthermore, the safety of the treated synthetic seawater was evaluated by analyzing the residual transformed products. Overall, pretreatment with the UV/PMS system mitigated fouling on the RO membrane. [Display omitted] • The UV/PMS system mineralized humic acid (HA) in high salt concentrations. • Mineralization rate was in the order of DI water > NaCl solution > synthetic seawater. • Anions, particularly Cl − and Br − , retarded mineralization efficiency. • There were no halogenated disinfection byproducts produced. • On the RO membrane, significant fouling mitigation was obtained. [ABSTRACT FROM AUTHOR]

With the world's population growing rapidly, pressure is increasing on the limited fresh water resources. Membrane technology could play a vital role in solving the water scarcity issues through alternative sources such as saline water sources and wastewater reclamation. The current generation of membrane technologies, particularly reverse osmosis (RO), has significantly improved in performance. However, RO desalination is still energy intensive and any effort to improve energy efficiency increases total cost of the product water. Since energy, environment and climate change issues are all inter-related, desalination for large-scale irrigation requires new novel technologies that address the energy issues. Forward osmosis (FO) is an emerging membrane technology. However, FO desalination for potable water is still a challenge because, recovery and regeneration of draw solutes require additional processes and energy. This article focuses on the application of FO desalination for non-potable irrigation where maximum water is required. In this concept of fertiliser drawn FO (FDFO) desalination, fertilisers are used as draw solutions (DS). The diluted draw solution after desalination can be directly applied for fertigation without the need for recovery and regeneration of DS. FDFO desalination can make irrigation water available at comparatively lower energy than the current desalination technologies. As a low energy technology, FDFO can be easily powered by renewable energy sources and therefore suitable for inland and remote applications. This article outlines the concept of FDFO desalination and critically evaluates the scope and limitations of this technology for fertigation, including suggestions on options to overcome some of these limitations. [ABSTRACT FROM AUTHOR]

The dewatering of highly saline (waste)waters by typical osmotic membranes, such as reverse osmosis (RO) or forward osmosis (FO), was significantly improved by a novel process in which an osmotic pressure gradient across the membrane is eliminated or reduced by increasing osmotic pressure in the permeate side. In this work, the concept of an osmotically enhanced dewatering (OED) process was fundamentally analyzed via conceptual modeling and verified experimentally under various hydraulic and osmotic pressure conditions. No or less osmotic gradient across the membrane resulted in higher water recovery than RO. Larger water flux was also produced than FO because the loss of osmotic driving force by internal concentration polarization (ICP) was greatly reduced. For instance, a series of experiments demonstrated that water flux of 1.2 LMH was obtained at low hydraulic pressure of 15 bar when a feed of 2.4 M NaCl was dewatered by the OED process. In addition, membrane characteristics (A, B, S) were optimized by modeling, and further examined experimentally using typical NF and FO membranes. Lastly, less reverse solute diffusion ensured a product of high quality after dewatering, suggesting that this process can be applied to not only highly saline shale gas produced water treatment, but also protein and pharmaceutical enrichment. [ABSTRACT FROM AUTHOR]

Forward osmosis (FO) has great potential for sustainable osmotic dewatering, which can attain several goals including low energy use, high water recovery, and low membrane fouling. However, this technology still involves critical issues that should be explored to achieve successful functioning of osmotic dehydration process, such as feed characteristics, FO membrane performance, and draw solution selection. In this study, the effectiveness of FO for osmotic dehydration was demonstrated by adopting xylose solution as model feed. Aside from current energy intensive evaporation methods, this widely used sweetener needs an advanced and energy-efficient concentration method such as FO. The stable performance showed xylose can be sustainably concentrated with a consistently high dewatering rate, whereas the recovery rate using a pressure-driven membrane system was constrained by the bursting pressure of nanofiltration membrane. Lastly, high-quality of concentrated product can be obtained by selecting a suitable draw solution of which its reversely diffused salts barely affect the xylose solution or are used to enhance the xylose quality. Employing Poly (aspartic acid) sodium salt or sugar-based solutes as draw help to preserve the purity of enriched xylose. These results suggest that FO can provide a feasible solution for food processing which requires product concentration through dewatering while preserving and improving its quality. [ABSTRACT FROM AUTHOR]

A forward osmosis (FO) and reverse osmosis (RO) hybrid process was examined for sustainable direct potable reuse (DPR) of wastewater through integration with seawater desalination. Using real wastewater secondary effluent, feasibility of the FO-RO system for DPR was systematically assessed by investigating fouling behavior and its reversibility and evaluating the quality of produced water. Its technical advantages were further verified by the ease of fouling control. The results for the silt density index (SDI) and the modified fouling index (MFI) clearly demonstrated that FO significantly alleviated the potential of subsequent RO membrane fouling, leading to sustainable RO operation for wastewater reuse. Permeate water flux in FO was significantly recovered by physical cleaning. However, biopolymer-like substances was persistently accumulated on the FO membrane surface even after repeated cleaning, suggesting that pretreatment for removal of such substances causing irreversible fouling are required for long-term operation of the FO-RO process. Lastly, the final product water satisfied all 58 components of the quality standards for drinking water in Korea, confirming that the double barrier provided by the FO and RO membranes was adequate for DPR. [ABSTRACT FROM AUTHOR]

Pressure retarded osmosis (PRO) operated with active layer facing feed solution (AL-FS), in contrary to typical PRO membrane orientation (active layer facing draw solution, AL-DS), has a strong potential for sustainable power generation from salinity gradient energy with low membrane fouling. The feasibility of PRO in AL-FS mode was first examined by verifying less membrane deformation and insignificant shadow effect under pressurized PRO operation. The simulation of such PRO process showed that its low power density due to internal concentration polarization could be improved through reducing structural parameter of the support layer. Fouling experiments using synthetic wastewater clearly demonstrated that severe fouling observed with PRO operation at AL-DS was greatly reduced by switching PRO membrane orientation to AL-FS. Lastly, specific energy consumption of a PRO-RO hybrid process was assessed to be favorable in view of both power density and membrane fouling, suggesting that economically feasible power generation as well as effective water treatment can be achieved by operating PRO in the AL-FS orientation. [ABSTRACT FROM AUTHOR]

In this study, the fouling propensity of a hybrid ceramic membrane bioreactor (CMBR)-reverse osmosis (RO) process was investigated over a prolonged period using real textile wastewater effluent. Additionally, the effectiveness of in-situ ozonation for fouling mitigation was investigated. The results revealed that the CMBR-RO system achieved approximately 99.8 % removal of chemical oxygen demand and 97.4 % removal of total nitrogen. Despite this, soluble extracellular polymeric substances, particularly biopolymers and humics-like substances, remained in the system, resulting in irreversible fouling on the ultrafiltration (UF) membrane. The implementation of in-situ ozonation notably reduced ceramic membrane fouling by enhancing the filterability of larger macromolecules and eliminating inorganic/organic foulants from the membrane surface. Multiple modified fouling indexes were also utilized to evaluate the fouling potential of the RO feed water through size fractionation. It is worth noting that ozonation could pose a potential risk for subsequent RO membrane fouling due to the formation of low molecular weight neutrals, acids, and calcium- or silica- related inorganic-organic complexes. Overall, the integrated CMBR-RO system with in-situ ozonation exhibited excellent performance in producing clean water, achieving nearly 100 % removal of 20 Aromatic Amines. These findings underscore the viability of the CMBR-RO system as a practical and sustainable choice for the reclamation of textile wastewater. [Display omitted] • Biopolymers and humics-like substances led to irreversible fouling • In-situ ozonation significantly improved the filterability of larger macromolecules • LMW molecules induced by ozone poses a potential risk for subsequent RO • The hybrid process removed almost 100% of 20 AAs in final water [ABSTRACT FROM AUTHOR]

Abstract: In order to evaluate the effect of membrane surface properties on the initial stage of biofouling, in the reverse osmosis (RO) membrane process, initial bacterial adhesion and biofilm formation experiments were performed under no filtration condition. In this study, five commercialized polyamide thin-film composite RO membranes (SW30HRLE, SW30HR (Dow FilmTec Co., USA), TM820 (Toray Co., Japan), RE-BE, RE-FE (Woongjin Chemical Co., Korea)) were chosen and their surface properties such as surface charge, roughness, hydrophobicity and surface morphology were measured. For examining initial bacterial adhesion, a flow channel reactor was employed for 3h, while for examining a biofilm formation, the CDC reactor was employed for 48h. Pseudomonas aeruginosa PAO1 tagged with GFP was selected as a model bacterial strain. Major findings in this study indicate that although the initial bacterial cell adhesion in a flow channel reactor indicated more bacterial cells attachment on the membrane surface with higher hydrophobicity, the extent of biofilm grown in CDC reactor for 48h became similar regardless of the difference of the membrane surface properties, indicating that the membrane surface properties become a less important factor affecting the biofilm growth on the membrane surface. This finding will be helpful in improving the understanding of biofouling issue occurring in the real RO membrane system, although practical implication is somewhat limited since this study was performed under no filtration condition. [Copyright &y& Elsevier]

Owing to the significant increase in seawater desalination, seawater exhibiting extreme conditions of high salinity and high temperature cannot be avoided in the production of fresh water. Although seawater reverse osmosis (SWRO) is one of the most energy-saving desalination technologies, it might not be favorable for treating extreme seawater due to the operational limitations associated with the single-stage SWRO configuration. To overcome these limitations, the applicability of two-stage SWRO was examined. The recovery of single-stage SWRO was limited to 31% for stable operation, whereas two-stage SWRO, utilizing pressure exchangers as energy recovery devices, achieved 34% recovery for the same number of pressure vessels. Furthermore, the maximum water fluxes in the front SWRO elements were reduced under the design constraints of the two-stage configuration than that of the single-stage configuration. The two-stage SWRO system was energy-efficient with high recovery; however, under extreme conditions, the permeate quality was similar to that of single-stage SWRO. To improve the applicability of two-stage SWRO, internally staged design (ISD) and split partial second pass (SPSP) can be adopted. ISD can reduce water fluxes in the front elements, increasing system recovery, whereas SPSP design enables the reverse osmosis system to produce high-quality permeate with low additional energy. Unlabelled Image • SWRO performance was evaluated for high-salinity and high-temperature seawater. • Single-stage SWRO suffered from low recovery and high water flux for front elements. • Two-stage SWRO achieved higher recovery and exhibited lower front water flux. • ISD further increased recovery by reducing water fluxes of front elements. • SPSP improved product quality and energy efficiency by treating rear permeate. [ABSTRACT FROM AUTHOR]

Although seawater desalination is becoming an important technology for freshwater production, the presence of a high concentration of bromide in the seawater presents a major challenge. Bromide is one of the major inorganic precursors for the formation of disinfection by-products such as bromate, which is highly regulated due to its toxicity and carcinogenicity. Hence, a significant reduction of bromide ions is required prior to water disinfection. In Australia, all the desalination plants have to operate a two-stage reverse osmosis system to ensure effective bromide removal, which adds significant cost to the desalination system. In this study, a pilot-scale membrane capacitive deionisation (MCDI) was investigated as a potential alternative to the 2nd stage RO in seawater desalination. Moreover, strategies to enhance water recovery in MCDI was also carried out by using lower flow rates and shorter duration during the desorption stage. In order to reduce energy consumption in MCDI, a combined short-circuit and reverse polarity desorption is introduced. The results showed that MCDI can effectively remove bromide and dissolved salt at a much lower energy consumption compared with membrane process and that MCDI can be operated to achieve high water recovery without increasing the total energy consumption. Unlabelled Image • Bromide and TDS removal in pilot-scale MCDI was investigated • Use of lower desorption flow rate can significantly increase water recovery • Shorter desorption time can result in increased water recovery • A combined short-circuit followed by reverse voltage desorption can be effective [ABSTRACT FROM AUTHOR]

While single-stage is the general configuration for seawater reverse osmosis (SWRO), the two-stage design can increase the overall recovery of an SWRO system. Due to its high-recovery operation, the specific energy consumption (SEC) of two-stage SWRO is higher than that of single-stage. Thus, the two-stage configuration has not been extensively applied in the current desalination market. In contrast, recent studies have reported that the two-stage design can lower the SEC of SWRO compared to that of single-stage. However, the analyses were biased towards SEC, and the practical design aspects (e.g., permeate quality, water flux, and design ratios) were not systemically considered. Thus, this study examines the applicability of a two-stage SWRO system with a capacity of 100,000 m3/d that employs 1200 pressure vessels (PVs). Two-stage SWRO actually consumed a greater amount of energy than that of single-stage for typical SWRO recovery with the same number of PVs. In contrast, single- and two-stage SWRO produced permeate similar in quality, while the two-stage exhibited superior water-flux distribution along the PVs. Additionally, optimal ratios of permeate flow rate and number of PVs were determined by energy recovery devices type, where the ratio of 1:2 was selected for the reverse osmosis system with a pressure exchanger and 2:1 for that with a Pelton turbine. Considering SEC and other operational aspects, the use of two-stage SWRO was feasible at a 50–70% recovery rate. Image 1 • Two-stage SWRO is fundamentally analyzed and optimized for seawater desalination. • SEC of two-stage SWRO is higher than that of single-stage in typical recovery. • Water quality of single- and two-stage SWRO is similar at the same average flux. • Optimal ratios of permeate flow rate and number of PVs vary depending on ERD types. • Two-stage SWRO is more energy-efficient at a high recovery rate (e.g., 50–70%). [ABSTRACT FROM AUTHOR]

• Cold-cathode X-ray irradiation was newly applied to control fouling prior to RO process in SGPW treatment. • The feasibility of this novel X-ray technology was improved by developing CNT film emitter. • Its advantages include better energy efficiency, less heat generation, and easy dose control. • Aliphatic hydrocarbon (oil) caused severe fouling in the RO process during SGPW treatment. • New X-ray irradiation effectively reduced fouling with a low dose and energy consumption. For a more sustainable and environmental-friendly management of shale gas produced water (SGPW), it is essential to customize and optimize the treatment options since the characteristics of SGPW vary both spatially and temporally. However, fundamental studies on the foulants of SGPW and their control methods are lacking, particularly in connection with the RO-based process, which has been adopted increasingly in SGPW treatment. This study fundamentally evaluated the feasibility of novel cold-cathode X-ray irradiation as an additional fouling control process prior to the RO process using actual SGPW extracted from the Sichuan shale region (China) for the first time in literature. The foulants incapable of being removed by conventional pre-treatments (e.g., dissolved air flotation (DAF) and ultrafiltration (UF) membrane) induced organic fouling in the RO stage, and they were identified eventually as aliphatic hydrocarbon (oil) components. The fouling mechanism was deduced to be the formation of coalesced hydrocarbon layer on the RO membrane surface. In order to target these identified oily substances surgically, the novel cold-cathode X-ray irradiation process was employed since this technology offers much better energy efficiency compared to the existing thermionic X-ray irradiation. Our work demonstrated that the cold-cathode X-ray irradiation could efficiently remove the aliphatic hydrocarbon in the pre-treatment stage. This new X-ray irradiation process was optimized further with respect to energy consumption by investigating the effect of tube current and voltage. Our experimental observations suggest that the cold-cathode X-ray irradiation process could be an energy-efficient alternative for the treatment of organic-rich (oily) industrial wastewaters such as SGPW. [ABSTRACT FROM AUTHOR]

Membrane fouling is an inevitable phenomenon and common issue in Reverse Osmosis (RO) membrane systems used for water reclamation. Severe membrane fouling in RO system could consequently increases the operation cost as it requires frequent membrane chemical cleaning process thus consuming more chemical agents and shorten lifespan of RO membrane module. In this study, potential foulants of RO membranes that are used at Sydney's urban wastewater recycling facility which treated for domestic and commercial wastewaters, were investigated via membrane autopsy method. The three-year-old spiral wound RO membrane modules were taken from the site for membrane autopsy and to investigate major fouling factors as well as in-depth study of fouling mechanisms throughout various characterization methods. Additionally, a flux recovery rate of fouled RO membranes via the chemical cleaning was also examined using different kind of chemical cleaning agents to find a most effective chemical cleaning combination. • Three-year-old RO membranes in WWTP were conducted membrane autopsy. • Membrane fouling factors were investigated using various analysis methods. • Effective chemical cleaning condition was found via variety use of cleaning agents. • Organic fouling on the membrane was predominant by protein and polysaccharides. • Mg and Na were the primary components of the foulants on the membrane. [ABSTRACT FROM AUTHOR]

Ultrapure water (UPW) is essential in the semiconductor industry for rinsing and cleaning products. With the growing demand for UPW, various feed water sources such as tap water, surface water, and wastewater are utilized to produce UPW. However, these feed water sources contain various low molecular weight organic matters (LMWOMs), which can adversely affect the quality of semiconductors when present in treated UPW. Therefore, achieving the complete removal of LMWOMs is crucial in the UPW production process. However, the current reverse osmosis (RO) and vacuum ultraviolet (VUV) processes employed for UPW production have limitations in achieving complete LMWOM removal. Therefore, this study is conducted to investigate the mechanisms of LMWOM removal in RO and the performance of VUV for high-quality UPW production. Six LMWOMs found in the semiconductor industry were tested for lab- and pilot-scale experiments. The result showed that size exclusion is the main mechanism of LMWOM removal in the RO process. However, methanol, ethanol, and urea were not efficiently removed by RO membranes. In addition, a lab-scale VUV experiment was performed under accelerated conditions to examine the oxidation mechanism of LMWOM. The LMWOM with low reactivity to hydroxyl radicals, such as tetramethylammonium hydroxide (TMAH) and urea, were not removed perfectly within 60 min and 180 min, respectively. Furthermore, a pilot-scale VUV experiment was performed to examine the oxidation of LMWOM under real UPW production conditions. Despite observing a correlation in the pseudo-first-order rate constants between the lab-scale and pilot-scale experiments, the removal of TMAH and urea was still not achieved even with a lamp power of 320 W. As urea was not completely removed by either RO or VUV, strategies for UPW production using current water sources are discussed to develop future UPW technologies. [Display omitted] • The fate of six LMWOMs was analyzed in RO and VUV processes for UPW production. • Size exclusion is the most dominant mechanism for the removal of LMWOMs in RO. • High reactivity with hydroxyl radicals is key to the removal of LMWOMs through VUV. • Pilot-scale VUV results correlate with lab-scale VUV experiments in real UPW conditions. • Urea is the most problematic LMWOM in the UPW process for the semiconductor industry. [ABSTRACT FROM AUTHOR]

Managing shale gas produced water (SGPW) is one of the greatest challenges for shale gas industry due to its high salinity and water volume. Osmotically enhanced dewatering (OED) has great potential for treating SGPW because of its higher water recovery and lower energy consumption. This study systematically investigated the effects of operating conditions on OED performance through numerical simulation of membrane modules. The simulation results first showed that OED achieved higher water recovery over forward osmosis (FO) due to less internal concentration polarization (ICP). Water recovery could be higher with decreasing feed flow fraction, increasing normalized membrane area, and increasing hydraulic driving force fraction. It was also demonstrated that OED-RO hybrid process was able to yield more water with similar energy efficiency as one-stage RO, for SGPW of 28.5 g/L total dissolved solids (TDS) under realistic conditions considering inefficiency associated with pump and energy recovery device (ERD). Lastly, to validate our findings, OED experiments were performed with pre-treated real SGPW as a feed solution, and exhibited good agreement with the simulation results. Specifically, water recovery was achieved up to 67% with a high rejection rate of over 97% for most ions at a hydraulic pressure of 30 bar. Our modeled and experimental observations suggest that the OED-RO process can be an energy-efficient process in concentrating high salinity wastewater. [ABSTRACT FROM AUTHOR]

Most Australian surface and ground waters have relatively high concentration of bromide between 400 and 8000 μg/L and even higher concentration in seawater between 60,000–78,000 μg/L. Although bromide is not regulated, even at low concentrations of 50–100 μg/L, it can lead to the formation of several types of harmful disinfection by-products (DBPs) during the disinfection process. One of the major concerns with brominated DBPs is the formation of bromate (BrO 3 − ), a serious carcinogen that is formed when water containing a high concentration of bromide is disinfected. As a result, bromate is highly regulated in Australian water standards with the maximum concentration of 20 μg/L in the drinking water. Since seawater reverse osmosis (SWRO) desalination plays an important role in augmenting fresh water supplies in Australia, SWRO plants in Australia usually adopt 2nd pass brackish water reverse osmosis (BWRO) for effective bromide removal, which is not only energy-intensive to operate but also has higher capital cost. In this study, we evaluated the feasibility of membrane capacitive deionisation (MCDI) as one of the alternatives to the 2nd pass BWRO for effective bromide removal in a more energy efficient way. [ABSTRACT FROM AUTHOR]

The fertilizer-drawn forward osmosis (FDFO) was investigated for treating coal seam gas (CSG) produced water to generate nutrient rich solution for irrigation. Its performance was evaluated and compared with reverse osmosis (RO) in terms of specific energy consumption (SEC) and nutrient concentrations in the final product water. The RO-FDFO hybrid process was developed to further improve FDFO. The results showed that FDFO has the lowest SEC followed by the RO-FDFO and RO processes. The final nutrient concentration simulation demonstrated that the RO-FDFO hybrid process has lower final concentration, higher maximum recovery and lower nutrient loss than the stand alone FDFO process. Therefore, it was suggested that the RO-FDFO is the most effective treatment option for CSG produced water as well as favourable nutrient supply. Lastly, membrane fouling mechanism was examined in CSG RO brine treatment by FDFO, and the strategies for controlling fouling were critically evaluated. KNO 3 exhibited the highest flux decline corresponding to the highest reverse salt flux, while the most severe membrane scaling was observed with calcium nitrate, primarily due to the reverse transport of calcium ions. To control membrane fouling in FDFO process, both physical flushing and chemical cleaning were examined. Membrane cleaning with citric acid of 5% resulted in a complete flux recovery. [ABSTRACT FROM AUTHOR]

Environmental and economic impacts of the fertilizer drawn forward osmosis (FDFO) and nanofiltration (NF) hybrid system were conducted and compared with conventional reverse osmosis (RO) hybrid scenarios using microfiltration (MF) or ultrafiltration (UF) as a pre-treatment process. The results showed that the FDFO-NF hybrid system using thin film composite forward osmosis (TFC) FO membrane has less environmental impact than conventional RO hybrid systems due to lower consumption of energy and cleaning chemicals. The energy requirement for the treatment of mine impaired water by the FDFO-NF hybrid system was 1.08 kWh/m 3 , which is 13.6% less energy than an MF-RO and 21% less than UF-RO under similar initial feed solution. In a closed-loop system, the FDFO-NF hybrid system using a TFC FO membrane with an optimum NF recovery rate of 84% had the lowest unit operating expenditure of AUD $0.41/m 3 . Besides, given the current relatively high price and low flux performance of the cellulose triacetate and TFC FO membranes, the FDFO-NF hybrid system still holds opportunities to reduce operating expenditure further. Optimizing NF recovery rates and improving the water flux of the membrane would decrease the unit OPEX costs, although the TFC FO membrane would be less sensitive to this effect. [ABSTRACT FROM AUTHOR]

Recently, a modified fouling index (MFI) is published on ASTM, and thus, is expected to become a standard method for evaluating fouling potential, as a supplement to silt density index (SDI). Employing membranes with smaller pore size in MFI measurements has been continuously suggested in many previous studies. However, there was a lack of practical studies verifying the usefulness of MFI. In this study, the applicability of multiple MFIs (i.e., MFI 0.45 , MFI-UF 100 kDa and MFI-UF 10 kDa ) were evaluated at a full-scale UF/RO seawater desalination plant located in the Middle East. For a year, MFIs were measured with RO feed water and the results were correlated with increments in differential pressure (DP) of RO process. Regression analysis was conducted in order to find out whether the fouling index could predict RO performance deterioration. The observed MFIs clearly showed correlation with DP variation, while SDI and water quality parameters (e.g. turbidity and UV 254 ) exhibited relatively low accordance. Particularly, MFI-UF 100 kDa was the most sensitive, indicating that colloidal fouling is the main cause of fouling in SWRO desalination. The regression results were reconfirmed through specific events where feed water quality was severely changed due to red tide or ship movement at intake. These events provided unconventional feed water characteristics, but similar trend was observed that MFI-UF 100 kDa was most sensitive. The application of MFI in an actual plant provided valuable contribution for the further advancement of MFI measurements. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) process using a thin-film composite (TFC) membrane is a current leading technology for water desalination. The polyamide permselective layer of the TFC membrane enables salt retention and water permeation, with the ultimate goal of minimizing the permselective layer thickness for maximum energy efficiency. Yet this drive towards reducing the permselective layer thickness is greatly handicapped by the interfacial polymerization (IP) approach used to fabricate TFC membranes. We present layered interfacial polymerization (LIP) as a new paradigm for fabricating TFC membranes with unprecedented nanoscale control in the permselective layer thickness and smoothness, coupled with the advantage of industrial scale manufacturability. Membranes fabricated using LIP demonstrated high NaCl rejection necessary for water desalination, with water permeance ≈ 86% and permselectivity ≈ 450% greater than that of the membranes prepared using conventional IP and comparable water permeance and permselectivity ≈ 17% higher than that of commercial RO membranes. In addition, the unique smooth morphology of the LIP-assembled membrane surface enabled to mitigate the membrane fouling compared to the characteristic rough surface of the conventional IP-assembled membrane. [ABSTRACT FROM AUTHOR]

We report a fabrication method of polyamide (PA) thin film composite reverse osmosis membranes, so-called support-free interfacial polymerization (SFIP). In contrast to conventional interfacial polymerization (IP) where a PA layer is formed in-situ on top of a support, in this SFIP method the PA layer is first formed at the interface without a support, followed by attachment onto a support. Enhancing the chemical adhesion between the PA layer and a polyacrylonitrile support through the chemical modification on the support leads to the fabrication of defect-free membranes which outperform the conventional IP-assembled membranes. Importantly, SFIP allows for the precise characterization of the PA layer and the PA-support interface by easily isolating each membrane component. SFIP produces a thinner and smoother PA structure with a more wettable and less negatively charged surface than its IP-assembled counterparts, presumably due to uniform and promoted amine diffusion during film formation. Furthermore, it was found that the bottom surface of the SFIP-assembled PA has a porous structure with higher hydrophilicity and a marginally lower negative charge than its opposite surface. The SFIP method provides a versatile platform to study the fundamental membrane structure-performance relationship and to develop high performance membranes. [ABSTRACT FROM AUTHOR]

Various industrial activities generate highly acidic wastewaters, posing a particular concern due to their large volume, environmental impact, and limited disposal options. Nanofiltration (NF) has the potential to provide energy-, cost-, and space-effective solutions for wastewater treatment at industrial sites. However, conventional thin-film composite NF membranes degrade under acid exposures, largely limiting their applications in industrial wastewater treatment. Development of chemically robust NF membranes that are stable during operation with highly acidic feed streams has been a subject of active research and industrial interest. In this critical review, we first provide a comprehensive survey for the broad spectrum of industrial processes that yield acidic wastewaters. We then conduct in-depth analyses for short- and long-term rejection performances and stabilities of commercial NF membranes, especially under low solution pH conditions. Several key mechanisms responsible for the degradation of semi-aromatic polyamide networks by acid-catalyzed hydrolysis are discussed to highlight the limitation of commercially available NF membranes. Finally, we describe a wide variety of technical strategies to fabricate acid-resistant NF membranes, focusing on the key mechanism to enhance acid stability. We conclude by providing useful insights to guide the future directions for academic studies as well as industrial applications of acid-resistant NF membranes. [Display omitted] • Performances of NF/RO membranes under acidic conditions were analyzed. • Fundamental mechanisms of acid-catalyzed degradation were described. • Recent fabrication strategies for acid-resistance NF membranes were discussed. • Future directions for acid-resistance NF membrane applications were proposed. [ABSTRACT FROM AUTHOR]

Harmful algal blooms (HABs) are a major barrier to the stable and efficient operation of seawater reverse osmosis (SWRO) desalination plants. Although the intensity varies regionally, the occurrence of HABs impairs plant operation through severe particulate, organic, and biological fouling of both pretreatment and RO systems. As a result, considerable effort has been put into developing and optimizing pre-treatment techniques to mitigate these problems. This study reviews the historical changes and current status of pretreatment applications based on >110 datasets for large SWRO desalination plants. Chronological analysis underscores the increasing trend in the operation of dissolved air flotation and ultrafiltration systems since severe HABs in the Middle East from 2008 to 2009. The impact of HAB characteristics on system performance was also analyzed, and the efficiency of current pretreatment systems for the removal of HABs was evaluated, along with proposals for operational guidelines. Finally, future strategies for i) intelligent monitoring and prediction of HABs, ii) improvement of unit processes for the removal of algal organic matter, and iii) utilization of algal biomass to alleviate environmental impact were systematically delineated for smarter, safer, and greener operation of future SWRO desalination plants in response to the occurrence of HABs. [Display omitted] • Review on the impact of harmful algal blooms (HABs) on seawater desalination • Analysis of >110 datasets of full-scale SWRO desalination plants • Historical trends and current practice of pretreatment applications • Guidelines for pretreatment operation under HABs occurrences • Future operational directions for smarter, safer and greener desalination practice [ABSTRACT FROM AUTHOR]

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]

The performance of pressure retarded osmosis (PRO) membrane, characterized by water and solute permeability ( A and B ) and the structural parameter ( S ), was analyzed by a new method designed to simulate the PRO process more closely. Compared to conventional approaches to membrane characterization using reverse osmosis (RO)/forward osmosis (FO), the newly developed method using a single PRO experiment better predicted PRO process performance, particularly when high pressure was applied on the draw side. It was clearly demonstrated that apparent B value increased with increasing draw pressure. This characterization method was also used to evaluate PRO membrane performance in the presence of organic matter, such as alginate or xanthan, in draw solutions. Organic matter in draw solutions reduced the apparent B value, which could result in less draw solute loss in PRO processes. Our experimental observations clearly suggested that PRO membrane processes should be analyzed and predicted by methods like the one presented which simulate actual PRO operating conditions, particularly the hydraulic pressure applied to draw solutions. [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]

[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]

Abstract: A numerical model for predicting the flux decline due to colloidal fouling was developed for a forward osmosis (FO) membrane system. We derived the kinetic equation of the cake layer growth based on a first-order reaction and control volume approach. Based on the model simulation, it was found that the deposited particles on a membrane surface are proportional to the feed concentration and the permeate flux. Moreover, the simulation result reveals that the cake-enhanced osmotic pressure (CEOP) is a key factor diminishing the permeate flux for large colloidal foulants. For small colloidal foulants, the hydraulic resistance of the cake layer is dominant in flux decline at the beginning of the fouling and CEOP increasingly become significant as fouling progresses. The effects of the reverse draw solute permeation on the flux decline were also simulated. Interestingly, the increased reverse draw solute permeation obtained by increasing the solute permeability showed little effect on the flux decline. Contrarily, variation of the diffusivity significantly influenced the flux decline. Consequently, the numerical model developed in this paper suggests that the selection of draw solute for an FO membrane process should be carefully regarded, along with the fouling mechanism. [Copyright &y& Elsevier]

Abstract: The physical and chemical factors affecting boron solute flux behavior and membrane transport mechanisms in forward osmosis (FO) have been systematically investigated. Boron solute flux behavior in FO was further compared with that in reverse osmosis (RO) by employing identical plate-and-frame cells and membranes under the same filtration conditions. The influence of draw solution pH, draw solution type, and membrane orientation on boron solute flux was examined for FO, and the effects of water flux, cross-flow velocity, feed water boron concentration, and solution pH on boron solute flux were examined for both FO and RO. Results show that reverse salt diffusion, a unique feature of FO, is a key mechanism governing boron solute flux in FO. Boron solute flux through the FO membrane was inversely proportional to the degree of reverse salt diffusion by draw solution. The higher boron rejection observed in FO compared to RO is also attributed to reverse salt diffusion in FO. It is also shown that membrane orientation in FO plays an important role, affecting boron solute flux due to different degrees of internal concentration polarization. In both FO and RO, boron solute flux increased with increasing water flux. However, the influence of water flux on boron solute flux was less significant in FO than RO. Furthermore, boron solute flux decreased with increasing feed water pH due to the conversion of the neutral boric acid to borate anions. The findings provide new insight into the mechanisms and factors controlling boron solute transport in FO. [Copyright &y& Elsevier]

Abstract: The surface characteristics of reverse osmosis membranes and their relation to membrane fouling are systematically investigated by measuring membrane dynamic hysteresis based on the Wilhelmy plate method. Dynamic hysteresis represents the difference between the forces applied to a membrane surface when it is advanced into and withdrawn from a liquid or solution. Our results demonstrate that the chemical surface heterogeneity of various RO membranes could be quantified by measuring their dynamic hysteresis. The chemical heterogeneity was mostly related to the distribution of surface charge rather than average zeta potential. There was a remarkable correlation between the chemical surface heterogeneity and membrane dynamic hysteresis. It was clearly shown that dynamic hysteresis varied substantially with respect to the solution chemistry of test solutions. The dynamic hysteresis of RO membranes measured in the presence of organic foulants was further related to the flux-decline rate determined from bench-scale fouling experiments. It was found that higher flux-decline rate was obtained for RO membranes with larger dynamic hysteresis. Based on the results in this study, it is demonstrated that dynamic hysteresis measurements can be a promising tool for characterizing membrane surfaces as well as assessing membrane fouling. [ABSTRACT FROM AUTHOR]

Abstract: Fouling behaviors during forward osmosis (FO) and reverse osmosis (RO) are compared. Alginate, humic acid, and bovine serum albumin (BSA) are used as model organic foulants, and two suspensions of silica colloids of different sizes are chosen as model particulate foulants. To allow meaningful comparison of fouling behavior, identical hydrodynamic operating conditions (i.e., initial permeate flux and cross-flow velocity) and feed water chemistries (i.e., pH, ionic strength, and calcium concentration) are employed during FO and RO fouling runs. The observed flux-decline behavior in FO changed dramatically with the type of organic foulant, size of colloidal foulant, and the type of the draw solution employed to generate the osmotic driving force. Based on these experimental data and the systematic comparisons of fouling behaviors of FO and RO, we provide new insights into the mechanisms governing FO fouling. In FO, reverse diffusion of salt from the draw solution to the feed side exacerbates the cake-enhanced osmotic pressure within the fouling layer. The elevated osmotic pressure near the membrane surface on the feed side leads to a substantial drop in the net osmotic driving force and, thus, significant decline of permeate flux. Our results further suggest that the structure (i.e., thickness and compactness) of the fouling layers of FO and RO is quite different. By varying the cross-flow velocity during the organic fouling runs, we were able to examine the fouling reversibility in FO and RO. The permeate flux during organic fouling in FO recovered almost completely with increasing cross-flow velocity, while no noticeable change was observed for the RO system. Our results suggest that organic fouling in FO could be controlled effectively by optimizing the hydrodynamics in the feed stream without employing chemical cleaning. [ABSTRACT FROM AUTHOR]

Abstract: A new approach to evaluate the fouling potential of feed waters for reverse osmosis (RO) and nanofiltration (NF) practices was systematically investigated. A multiple membrane array system (MMAS) was developed, in which microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes were connected in series. This system was designed to separate the target foulants in the feed water and evaluate the fouling potential of a targeted foulant. More specifically, particulate, colloids, and organic matters were separated by MF, UF, and NF membranes in a consecutive manner, and the modified fouling index (MFI) was measured during each separation. The resulting three MFI values are Particle-MFI, Colloid-MFI, and Organic-MFI, and presented schematically in a triangle manner. The results demonstrated that fouling potentials of various feed waters (e.g., seawaters pretreated by various pretreatment options as well as raw seawater) evaluated by the MMAS were much more accurate and informative compared to those predicted by conventional silt density index (SDI) and single MFI. The fouling potentials determined by the MMAS precisely reflected changes in feed water quality by different pretreatment options (i.e., sand filtration, microfiltration, and ultrafiltration), while SDI measurements were not sensitive enough to detect these variations. It was also shown that the fouling potentials evaluated by the MMAS were well correlated with the actual flux-decline rates determined by lab-scale RO fouling experiments simulating seawater desalination, suggesting that the MMAS could provide a better way to predict fouling potential and guidance to select proper pretreatment processes. [ABSTRACT FROM AUTHOR]

Abstract: A membrane fouling index such as the silt density index (SDI) and modified fouling index (MFI) is an important parameter in design and operation of reverse osmosis (RO) and nanofiltration (NF) membrane processes for desalination. Nevertheless, SDI and MFI often fail to predict actual membrane fouling due to their limited capability to measure fouling potential by colloidal deposition and organic adsorption. In this study, a novel method to determine fouling index was attempted using a set of different membrane filters for better prediction of RO/NF fouling potential. Three MF/UF membranes were used for MFI tests in order to increase sensitivity to fouling potential of particles, hydrophobic organics, and sub-micron colloids. The fouling indices determined using different membrane filters were compared with RO filtration results. Experimental results indicated that fouling indices using different test membranes showed variable results for untreated and pretreated waters. Nevertheless, no single method was sufficient for accurate measurement of fouling potential. Accordingly, a new fouling index (CFI: combined fouling index) was developed by combining various fouling indices. The CFI exhibited good agreement with experimental data compared with other fouling indices such as SDI, MFI, and MFI–UF. [Copyright &y& Elsevier]

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]

Abstract: A series of reverse osmosis (RO) membrane filtration experiments was performed systematically in order to investigate the effects of various hydrodynamic and physicochemical operational parameters on a cake layer formation in colloidal and particulate suspensions. Bench-scale fouling experiments with a thin-film composite RO membrane were performed at various combinations of trans-membrane pressure (TMP), cross-flow velocity (CFV), particle size, pH, and ionic strength. In this study, silica particles with two different mean diameters of 0.1 and 3.0 μm were used as model colloids. Membrane filtration experiments with colloidal suspensions under various hydrodynamic operating conditions resulted that more significant permeate flux decline was observed as TMP increased and CFV decreased, which was attributed to the higher accumulative mass of particles on the membrane surface. Results of fouling experiments under various physicochemical operating conditions demonstrated that the rate of flux decline decreased significantly with an increase of the ionic strength as well as particle size, while the flux decline rate did not vary when solution pH changed. The experimentally measured cake layer thickness increased with a decrease in particle size and solution ionic strength. Furthermore, the model estimation of cake layer thickness by using a cake filtration theory based on the hydraulic resistance of membrane and cake layer was performed under various ionic strength conditions. The primary model parameters including accumulated mass and specific cake resistance were calculated from the cake layer resistance. This result indicated that the formation of cake layer could be closely related with solution water chemistry. The model estimated cake layer thickness values were in good agreement with the experimentally measured values. [Copyright &y& Elsevier]

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]

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]

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]

Seawater is receiving consideration as an infinite water source in the current era of water shortage. The application of seawater reverse osmosis (SWRO) to prepare seawater for human use is increasing exponentially owing to its high energy efficiency among desalination technologies. However, SWRO is still energy-intensive, and thus needs to be improved further to become more environmentally sound (i.e., producing less CO 2). To tackle such a challenge, this study was conducted to propose strategies to lower the specific energy consumption (SEC) of the SWRO process. From the results of extensive review and theoretical analysis, three directions were proposed for improving the energy efficiency of the SWRO process: i) minimize the irreversible work of the high-pressure pump, ii) decrease the osmotic pressure of the feed, and iii) recover osmotic energy from reverse osmosis (RO) concentrate. After the feasibility of each approach was identified by assessing the theoretical minimum energy and the maximum available margin, strategies for each direction were presented with a technical description, then critically evaluated by considering their practical application. Because this paper includes theoretical perspectives for energy savings in SWRO, it provides comprehensive ideas for lowering the SEC of SWRO desalination plants in the future. Image 1 • Three improvement axes for low-energy reverse osmosis were analyzed theoretically. • Maximum margin and obtainable energy reduction in each axis were calculated. • Minimizing irreversibility is effective, but operating issues are challenging. • Decreasing osmotic pressure can be effective only with additional low-saline water. • Recovering osmotic energy may be effective, but needs to be further developed. [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]