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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]

In this study, a novel strategy for scaling control in forward osmosis (FO) by employing an antiscalant-blended draw solution is newly suggested. To evaluate its validity, an antiscalant-blended draw solution containing a mixture of NaCl and poly (aspartic acid sodium salt) (PAspNa) was examined by conducting FO experiments under gypsum scaling at various operating modes. Compared with a draw solution composed only of NaCl, the PAspNa-blended draw solution exhibited comparable water flux but significantly lower reverse solute flux. Gypsum fouling tests demonstrated that reversely flowed polymeric anions from the blended draw solution could effectively control membrane scaling, with a scaling inhibition efficiency comparable to that of the direct addition of PAspNa to the feed solution. Sodium hexametaphosphate (SHMP) was also assessed as another scale inhibiting chemical to verify this novel concept. Similar advantages were clearly observed with the SHMP-blended draw solution. The overall results demonstrated that this new scaling control strategy in FO could be extended to various antiscalants that are optimized for specific mineral scales, and thus potentially commercialized in real-world industrial applications, which is vulnerable to membrane scaling. [ABSTRACT FROM AUTHOR]

The effects of discharged brine from desalination plants, particularly brine containing algal toxins during harmful agal bloom (HAB) occurrence, are a major concern for marine life and, as a result, human health. Therefore, removing algal toxins from desalination brine is critical for safeguarding both human health and the marine environment. The present work examined the mineralization of domoic acid (DA), an algal toxin, in highly concentrated seawater for the first time using an ultraviolet light activated peroxymonosulfate (UV/PMS) system. Mineralization efficiencies, effects of various anion concentrations, and reaction by-products were investigated. The presence of anions such as chloride, bromide, and bicarbonate reduces the mineralization efficiency of the UV/PMS system, with bromide being the most detrimental. Although DA can be effectively degraded in synthetic seawater (35,000 ppm), total mineralization is not possible within 180 min of reaction time, with only 38.4 %, 44.8 %, and 41 % TOC removal in pH 3, 5, and 7, respectively, when 1 mM of PMS was used. Analyses of treated hypersaline seawater using ultra-high-resolution liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and ion chromatography revealed that DA was completely degraded in synthetic seawater and that, in the presence of algal organic matter, no toxic by-product was generated during the detoxification process. Overall, the UV/PMS system has the potential to be an effective treatment strategy for algal toxins in seawater during HAB events in the SWRO desalination process. [Display omitted] • Domoic acid (DA) mineralization efficiency by UV/PMS system was investigated. • DA can be effectively removed in deionized water and synthetic seawater. • Anions affected the mineralization efficiency with the most detrimental being Br −> Cl −>HCO 3 −. • No halogenation byproducts, chlorates, or bromates were detected after treating DA in hypersaline seawater. [ABSTRACT FROM AUTHOR]

Abstract: Fouling potentials caused by particulate matters are generally evaluated by fouling index, such as SDI and MFI, widely used in RO membrane practices. However, these fouling indices failed to predict the effect of nano-colloidal sizes on flux decline, implying that colloidal fouling is too complex to be analyzed by simple fouling index. Thus, in this study, nano-colloidal fouling mechanism in seawater reverse osmosis (SWRO) desalination was fundamentally investigated by employing new approach. Specifically, the specific cake resistance of colloidal foulants was first determined by a novel method, cake resistance simulator-modified fouling index nanofiltration (MFI-NFCRS), which was conducted under operating pressure and solute environment similar to those of real SWRO desalination. Then colloidal deposition and resulting cake-enhanced osmotic pressure (CEOP) were quantitatively assessed by fitting RO experimental data to the calculations from the CEOP model. The results clearly demonstrated that the flux decline caused colloidal deposition in the SWRO process depended greatly on the CEOP. The newly developed methodology including MFI-NFCRS is expected to contribute significantly to better understand nano-colloidal fouling mechanisms and to accurately predict their fouling potentials in the SWRO desalination. [Copyright &y& Elsevier]

Abstract: Forward osmosis (FO) has gained significant research interest due to the wide range of potential applications in desalination and wastewater reuse. However, the FO process being concentration (osmosis) driven has its own intrinsic limitations. Net transfer of water across the membrane occurs until the point of osmotic equilibrium between the draw solution (DS) and the feed solution (FS). Without external intervention, it is impossible to dilute the DS beyond the point of osmotic equilibrium. In this study, the concept of osmotic equilibrium in the FO process is introduced by simulating conditions in a plate-and-frame FO membrane module using established mass transport models. The simulations evaluated the influence of various operating parameters on process performance, assessed in terms of water flux, feed recovery rate and the final concentration of the diluted DS. The counter-current crossflow mode of operation has been observed to be advantageous because it can achieve higher module average water flux, higher feed water recovery rates and higher DS final dilution. Based on the osmotic equilibrium concept and mass balance analysis, a modified equation for the water extraction capacity of a draw solute has been proposed. This study underscores the need for process optimisation for large-scale FO operations. [Copyright &y& Elsevier]

Abstract: The concept of fertiliser drawn forward osmosis (FDFO) desalination lies in the premise that fertilisers that serve as draw solutions (DS) add value to the FDFO product water for fertigation. However, because FDFO desalination is concentration based, the process cannot continue beyond the concentration equilibrium, one of the major limitations of the forward osmosis (FO) process. This results in final FDFO product water that, unless subjected to substantial dilution with fresh water, exceeds the acceptable nutrient concentrations for direct fertigation. In this study, nanofiltration (NF) has been assessed as an integrated process to FDFO desalination, either as a pre-treatment or post-treatment, to reduce the nutrient concentrations in the final product water and thereby allow direct use of the product water for fertigation without further dilution. NF as pre-treatment or post-treatment was found effective in reducing the nutrient concentrations using brackish groundwater (BGW) sources with relatively low total dissolved solid (TDS). However, when using higher TDS BGW sources, the product water still required further dilution or post-treatment before fertigation. NF as post-treatment was found to be more advantageous both in terms of reduced nutrient concentrations in the final product water and energy consumption. [Copyright &y& Elsevier]

Abstract: An increase in the chemical oxygen demand (COD) has been noticed in most Korean reservoirs. Therefore, this research systematically investigated the causes of organic accumulation. Samples of soil affecting the quality of water of reservoirs were collected at various sources and analyzed for their organic characteristics. The COD to biochemical oxygen demand (BOD) ratio was used as the key parameter in the evaluation of non-biodegradable (NBD) organic accumulation in the reservoirs. Soil samples containing plant roots were agitated, with the supernatant showing COD/BOD ratios of less than 2.8, while those of the composted tree leaves were greater than 5.0, suggesting that humic substances produced in forest areas are a major cause of NBD organic accumulation in reservoirs. In addition, the organic fractionation of the leachate from leaching tests showed that of the various types of hydrophobic natural organic matter (NOM), the larger molecular weight humic acid makes a greater contribution than fulvic acid to the increase in the NBD COD in Korean reservoirs. [Copyright &y& Elsevier]

Abstract: Copper scales formed over 6-months during exposure to ground, surface and saline waters were characterized by EDS, XRD and XPS. Scale color and hardness were light red–brown–black/hard for high alkalinity and blue–green/soft for high SO4 or Cl waters. Cl was present in surface or saline copper scales. The Cu/Cu2O ratio decreased with time indicating an e transfer copper corrosion mechanism. Cu2O, CuO, and Cu(OH)2 dominated the top 0.5–1A° scale indicating continuous corrosion. Cu2O oxidation to CuO increased with alkalinity, and depended on time and pH. Total copper release was predicted using a Cu(OH)2 model. [Copyright &y& Elsevier]

Abstract: This paper describes the characterization and evaluation of various RO/NF membranes for the treatment of seasonally brackish surface water with high organic contents (TOC ≈21 mg/L). Twenty commercially available RO and NF membranes were initially evaluated by performing controlled bench-scale flat-sheet tests and surface characterization. Based on the results, four low pressure RO membranes were selected for use in the pilot study. The surface characterization revealed that each of four selected membranes had unique surface characteristics to minimize membrane fouling. Specifically, the LFC1 membrane featured a neutral or low negative surface to minimize electrostatic interactions with charged foulants. The X20 showed a highly negatively charged surface, and thus, was expected to perform well with feed waters containing negatively charged organics and colloids. The BW30FR1 exhibited a relatively neutral and hydrophilic surface, which could be beneficial for lessening organic and/or biofouling. The SG membrane had a smooth surface that made it quite resistant to fouling, particularly for colloidal deposition. In the large-scale pilot study using single element, all of the four membranes experienced a gradual increase in specific flux over time, indicating no fouling occurred during the pilot study. The deterioration of permeate water quality such as TDS was also observed over time, suggesting that the integrity of the membranes might be compromised by the monochloramine used for biofouling control. [Copyright &y& Elsevier]

Abstract: PbO, PbCO3, and Pb3(OH)2(CO3)2 were identified as primary corrosion products on lead coupons following three months of exposure to finished RO, surface and ground water by XRD and XPS. Based on these results, a Pb3(OH)2(CO3)2 solid phase equilibrium model was used as a function of water quality, was modified using diffusion theory and accurately predicted lead release for a majority of field observations. SEM photographs revealed sulfate and chloride affected the surface structure of corrosion scales and lead release. [Copyright &y& Elsevier]

Abstract: The impacts of distribution water quality changes caused by blending different source waters on lead release from corrosion loops containing small lead coupons were investigated in a pilot distribution study. The 1-year pilot study demonstrated that lead release to drinking water increased as chlorides increased and sulfates decreased. Silica and calcium inhibited lead release to a lesser degree than sulfates. An additional 3-month field study isolated and verified the effects of chlorides and sulfates on lead release. Lead release decreased with increasing pH and increasing alkalinity during the 1-year pilot study; however, the effects of pH and alkalinity on lead release, were not clearly elucidated due to confounding effects. A statistical model was developed using nonlinear regression, which showed that lead release increased with increasing chlorides, alkalinity and temperature, and decreased with increasing pH and sulfates. The model indicated that primary treatment processes such as enhanced coagulation and RO (reverse osmosis membrane) were related to lead release by water quality. Chlorides are high in RO-finished water and increase lead release, while sulfates are high following enhanced coagulation and decrease lead release. [Copyright &y& Elsevier]

Abstract: Interior scales on PVC, lined ductile iron (LDI), unlined cast iron (UCI) and galvanized steel (G) were analyzed by XRD, RMS, and XPS after contact with varying water quality for 1 year. FeCO3, α-FeOOH, β-FeOOH, γ-Fe2O3, Fe3O4 were identified as primary UCI corrosion products. No FeCO3 was found on G. The order of Fe release was UCI>G⩾LDI>PVC. For UCI, Fe release decreased as % Fe3O4 increased and as % Fe2O3 decreased in scale. Soluble Fe and FeCO3 transformation indicated FeCO3 solid was controlling Fe release. FeCO3 model and pilot data showed Fe increased as alkalinity and pH decreased. [Copyright &y& Elsevier]

Abstract: A series of filtration experiments was performed systematically to investigate physical and chemical factors affecting the efficiency of backwashing during microfiltration of colloidal suspensions. In this study, all experiments were conducted in dead-end filtration mode utilizing an outside-in, hollow-fiber module with a nominal pore size of 0.1 μm. Silica particles (mean diameter = 0.14 μm) were used as model colloids. Using a flux decline model based on the Happel''s cell for the hydraulic resistance of the particle layer, the cake structure was determined from experimental fouling data and then correlated to backwash efficiency. Modeling of experimental data revealed no noticeable changes in cake layer structure when feed particle concentration and operating pressure increased. Specifically, the packing density of the cake layer (1-cake porosity) in the cake layer ranged from 0.66 to 0.67, which corresponds well to random packing density. However, the particle packing density increased drastically with ionic strength. The results of backwashing experiments demonstrated that the efficiency of backwashing decreased significantly with increasing solution ionic strength, while backwash efficiency did not vary when particle concentration and operating pressure increased. This finding suggests that backwash efficiency is closely related to the structure of the cake layer formed during particle filtration. More densely packed cake layers were formed under high ionic strength, and consequently less flux was recovered per given backwash volume during backwashing. [Copyright &y& Elsevier]

Performance of a two-stage full-scale reverse osmosis (RO) process for a desalination plant in Florida was simulated with a mathematical model based on the principles of membrane transport and mass conservation. In this model, water flux at any point along the filtration channel is calculated locally according to the basic transport theory of RO membranes. The changes in cross-flow velocity and salt concentration along the filtration channel were determined using mass balance principles of water and salt. Simulations of the plant performance were compared with the in-plant observation data over a period of more than 300 days. The results showed that the model could adequately describe the performance of the full-scale RO process based on a few module and operating parameters. The study also revealed that salt rejection of a RO membrane changed with feed salt concentration. The osmotic pressure coefficient that fits best with performance of this plant was substantially lower than the value determined with the "rule of thumb" (i.e., osmotic pressure in psi ≈ 0.01 × total dissolved solids in mg/L) and had to be determined specifically for the particular feed water being processed. [ABSTRACT FROM AUTHOR]

The internal concentration polymerization (ICP) phenomenon may hinder the flux of forward osmosis (FO) membranes. The mitigation of ICP can be achieved by employing a porous support layer structure. Nevertheless, conventional interfacial polymerization (IP) methods encounter challenges in establishing a dense selective layer upon a highly porous support layer. In this study, the support-free assembled molecular layer-by-layer (SF-mLbL) was suggested to manufacture the thin-film composite (TFC) membrane by combining the separately fabricated polyamide (PA) selective layer with a tunable thickness and the highly porous support layer. The SF-mLbL (8 wt%) membrane had a higher water flux and selectivity (43.52 ± 0.89 LMH/0.15 ± 0.01 g L−1) than those (10.34 ± 0.48 LMH/0.75 ± 0.02 g L−1 and 7.41 ± 0.18 LMH/0.81 ± 0.01 g L−1) of IP-PA and commercial cellulose triacetate membranes as 0.5 M NaCl draw solution in FO mode. Consequently, the SF-mLbL membranes exhibited significant improvement in the FO process with well-balanced permselectivity. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In this study, the feasibility of forward osmosis (FO) hybridized with membrane distillation (MD) was systematically investigated for treating flue gas desulfurization (FGD) wastewater. FO experiments were conducted using raw FGD wastewater obtained from a coal-fired power plant in Korea. Severe membrane fouling in FO was observed since FGD wastewater contained various components (i.e., particles, colloids, organics, and ions). The combined fouling layer by particulates and scales was identified via scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). Therefore, fouling control strategies were suggested and evaluated. Microfiltration (MF) pre-treatment was effective in removing particulates and mitigating the initial fouling. Antiscalant-blended draw solution (DS) could inhibit the formation of membrane scaling. With such fouling control schemes, FO achieved the highest recovery rate compared to other desalting processes (i.e., RO and MD), suggesting that FO is suitable for treating wastewater with high fouling potential and high TDS. Finally, the diluted DS was recovered by MD. MD could re-concentrate the diluted DS up to 50% recovery rate with no significant flux decline. Rapid flux decline was then observed due to membrane scaling. Thus, appropriate antiscalants in DS should be considered to inhibit scaling formation in FO and MD simultaneously. Graphical abstract Image 1 Highlights • Developed FO-MD hybrid to treat FGD wastewater with high fouling potential. • Severe fouling, including CaSO 4 scaling, was observed in FO. • MF pretreatment and antiscalant-blended DS controlled FO fouling effectively. • FO with fouling control achieved the highest recovery compared to RO and MD. • Antiscalant should be developed for the scaling control in both FO and MD. [ABSTRACT FROM AUTHOR]

Since ultraviolet light emitting diodes (UV-LEDs) have emerged as an alternative light source for UV disinfection systems, enhancement of reactor performance is a demanding challenge to promote its practical application in water treatment process. This study explored the underlying mechanism of the inefficiency observed in flow-through mode UV disinfection tests to improve the light utilization of UV-LED applications. In particular, the disinfection performance of UV-LED reactors was evaluated using two different flow channel types, reservoir and pathway systems, in order to elucidate the impact of physical circumstances on germicidal efficiency as the light profile was adjusted. Overall, a significant reduction in germicidal efficiency was observed when exposure time was prolonged or a mixing chamber was integrated. Zeta analysis revealed that the repulsion rate between microorganisms decreased with UV fluence transfer, and that change might cause the shielding effect of UV delivery to target microorganisms. In line with the above findings, the reduction in efficiency intensified when opportunities for microbial collision increased. Thus, UV induced microbial aggregation was implicated as being a disinfection hindering factor, exerting its effect through uneven UV illumination. Ultimately, the results refuted the prevailing belief that UV has a cumulative effect. We found that the reservoir system achieved worse performance than the pathway system despite it providing 15 times higher UV fluence: the differences in germicidal efficiency were 1-log, 1.4-log and 1.7-log in the cases of P.aeruginosa , E.coli and S.aureus , respectively. [ABSTRACT FROM AUTHOR]

As a promising industrial application of forward osmosis (FO), an FO-based concentration system for precious metal recovery from printed circuit board (PCB) wastewater has been newly suggested. This novel FO concentration process utilizes a dilution-needed waste solution possessing high conductivity as a draw solution, and thus an external supply of draw solution as well as a re-concentration process for the diluted draw solution are not required. An electroless (E’less) nickel (Ni) plating solution was evaluated as dilution-needed waste stream-based draw solution, and the test results confirmed that the selected Ni solution could produce an acceptable FO performance, i.e., water flux of 39.4 LMH (active layer facing draw solution (AL-DS) mode with deionized feed solution). From a series of FO experiments conducted with a palladium (Pd) catalyst as a concentration-needed feed solution, the Pd solution was effectively concentrated under an active layer facing feed solution (AL-FS) mode with a slight impact from Pd scaling. The modeling prediction based on our experimental results showed that theoretically Pd can be concentrated 17.2-times-high. The overall performance of our Pd concentration tests indicated that the FO process is promising for concentrating Pd, thereby improving the efficiency of its recycling. The newly proposed system, a recovery-free FO driven by a waste stream, offers attractive economic advantages including (1) zero cost for the supply and re-concentration of the draw solution and (2) enhanced energy efficiency in the precious metal recycling process. [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]

Shale gas produced water (SGPW) treatment imposes greater technical challenges because of its high concentration of various contaminants. Membrane distillation crystallization (MDC) has a great potential to manage SGPW since it is capable of recovering both water and minerals at high rates, up to near a zero liquid discharge (ZLD) condition. To evaluate the feasibility of MDC for SGPW treatment, MDC performance indicators, such as water recovery rate, solid production rate (SPR) and specific energy consumption (SEC), were systematically investigated, to our knowledge for the first time, by using actual SGPW from Eagle Ford Shale (USA). The main operating parameters including feed cross-flow velocity (CFV) and crystallization temperature (T Cr ) were optimized by performing a series of MDC experiments. The results reported that water and minerals were effectively recovered with 84% of recovery rate and 2.72 kg/m 2 day of SPR under respective optimal operating conditions. Furthermore, the scale mechanism was firstly identified as limiting factor for MDC performance degradation. Lastly, SEC of MDC was estimated to be as low as 28.2 kWh/m 3 under ideal optimal operating conditions. Our experimental observations demonstrated that MDC could sustainably and effectively recover water and mineral with low energy consumption from SGPW by optimizing operating condition. [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]

Forward osmosis (FO) has attracted growing interest in both academic research and industrial development due to its fundamental and technical advantages. One of the key challenges that needs to be addressed to further advance this technology is the identification of an ideal membrane. However, the reliable methodology for characterizing FO membrane performance parameters has not yet been standardized, and thus various methods have been utilized to evaluate FO membrane performance. The RO-FO based method is the most widely used protocol, but it has fundamental problems in the measurement of intrinsic parameters. Non-pressurized methods have newly been suggested as another approach to evaluate FO membranes but they also have shown certain limitations, such as inaccurate performance prediction of pressure-applied FO processes. The development of a standard and reliable characterization method for FO membranes is an important step to enable the standardization of the results from different research works and to facilitate data exchange and interpretation. Process-optimized standardization method, which can accurately measure the intrinsic characteristics of the different osmosis processes, thus should be investigated in more detail through further research. [ABSTRACT FROM AUTHOR]

Pressure assisted osmosis (PAO) has been recently suggested as a way to overcome the current limitations of forward osmosis (FO), since water flux can be increased by additional hydraulic driving force. To validate its feasibility more fundamentally, the effect of hydraulic pressure combined with osmotically driven FO process was evaluated experimentally, and compared with theoretical modeling. Four different FO and NF membranes were selected and their performance characteristics were determined by both RO- and FO-based methods, since PAO is a simultaneous osmotic- and pressure-driven membrane process. The degree of enhancing water flux and reducing reverse solute flux (RSF) in the PAO process clearly differed according to the membrane type and their performance parameters. Modeling PAO performance, using the values of A, B, and S determined from both RO- and FO-based methods, often failed to exactly match experimental observations, particularly for thin film composite (TFC) FO membranes, suggesting that PAO membrane performance parameters are apparently pressure-dependent. Discernible compaction in the support layer of TFC FO membranes was identified and confirmed by FO tests at different operating modes and SEM analysis, partially explaining large variations in S values under pressurized PAO operation and thus resulting large deviation from theoretical predictions. [ABSTRACT FROM AUTHOR]

This study presents simulation of a closed-loop forward osmosis (FO)-nanofiltration (NF) hybrid system using fertiliser draw solution (DS) based on thermodynamic mass balance in a full-scale system neglecting the non-idealities such as finite membrane area that may exist in a real process. The simulation shows that the DS input parameters such as initial concentrations and its flow rates cannot be arbitrarily selected for a plant with defined volume output. For a fixed FO-NF plant capacity and feed concentration, the required initial DS flow rate varies inversely with the initial DS concentration or vice-versa. The net DS mass flow rate, a parameter constant for a fixed plant capacity but that increases linearly with the plant capacity and feed concentration, is the most important operational parameter of a closed-loop system. Increasing either of them or both increases the mass flow rate to the system directly affecting the final concentration of the diluted DS with direct energy implications to the NF process. Besides, the initial DS concentration and flow rates are also limited by the optimum recovery rates at which NF process can be operated which otherwise also have direct implications to the NF energy. This simulation also presents quantitative analysis of the reverse diffusion of fertiliser nutrients towards feed brine and the gradual accumulation of feed solutes within the closed system. [ABSTRACT FROM AUTHOR]

Ultrasound was used to improve a forward osmosis (FO) sludge dewatering process for the control of fouling by deposited sludge flocs. FO was able to concentrate activated sludge from a real-scale wastewater reclamation plant. However, the flux decline indicated a severe fouling phenomenon. To mitigate this FO fouling, ultrasound radiation using a novel cell configuration was applied. However, the application of continuous radiation unexpectedly resulted in more severe fouling. Fluorescence excitation-emission matrix (FEEM) spectroscopy showed that longer ultrasound radiation applications caused high organic release from sludge flocs. Confocal scanning laser microscopy (CLSM) clearly identified a thicker organic fouling layer on the FO membrane surface. Ultrasound cleaning was optimized for radiation length and improved by the integration of flushing. Specifically, the combination of ultrasound and flushing caused a flux loss recovery of 70% or more. This work demonstrated the possibility of ultrasound cleaning as a fouling control method for FO sludge dewatering applications. [ABSTRACT FROM AUTHOR]

To advance cost-effective strategies for developing flat-sheet ceramic microfiltration membranes, the feasibility of using waste mineral-based materials as a ceramic membrane in engineered membrane bioreactor systems (MBRs) for treating low-strength domestic wastewater was evaluated. The ceramic membrane support layers that had effectively been fabricated with pyrophyllite and alumina were sintered at 1350 °C, and subsequently coated with alumina powder suspension to achieve a narrow pore size distribution. Membrane surface properties were characterized to understand the membrane fouling phenomenon in ceramic MBRs (CMBRs). Consistently high organic removal efficiency could be achieved under all investigated hydraulic retention times (HRTs) in the CMBRs. The physico-chemical sludge properties were measured to evaluate design parameters affecting membrane fouling for the CMBR. We further evaluated the performance of pyrophyllite-alumina composite ceramic membranes in a pilot-scale CMBR plant, with 1 m 3 /d capacity that was constructed at an actual water resource recovery facility (WRRF), to improve nitrogen removal and produce high quality effluent through a combined process of modified Ludzack-Ettinger (MLE) and CMBR (MLE/CMBR). The MLE/CMBR was operated successfully up to 20 LMH, with the final effluent chemical oxygen demand (COD) being maintained below 16.3 mg/L. [ABSTRACT FROM AUTHOR]

In this study, a newly developed capacitive deionization (MCDI) integrated with a monovalent cation permselective exchange membrane was evaluated for selective removal of monovalent and divalent cations. A variety of solution chemistries including cation composition, total dissolved solids (TDS), and feedwater pH were investigated. The removal selectivity was worsened when TDS concentration increased and pH decreased. Based on the experimental observations in this study, the optimum operating conditions (i.e., time, voltage, and flow rate) were recommended for maximum selectivity. The energy consumption of MCDI process was compared with NF process by collecting NF plant data from the previous literature. It was found that the MCDI process was more effective for selective removal of monovalent cations, and used less energy than the NF process under optimum conditions. Based on the results, a novel concept of employing MCDI process producing Ca 2+ -rich water as a post-treatment integrated with typical NF/LPRO softening process was proposed for preventing the corrosion in the pipe distribution system. [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]

The demand for ultrapure water (UPW) has been increased over the past decades. UPW production now occupies an almost equivalent position with seawater desalination in the world water market, fulfilling the demands of various industrial purposes. As an extremely low level of contaminants is required, the typical UPW production system combines 5 to10 purification technologies including ultrafiltration (UF), reverse osmosis (RO) and ion exchanger (IX). In recent years, RO has been at the forefront of this elaborate process as the majority of impurity rejections is carried out with it. This study provides a comprehensive review of the rising role of RO to satisfy the technical requirements in the UPW sector, with an emphasis on electronic industrial applications. The major transitions in recent UPW production are first reviewed: 1) ever-increasing water quality demand, 2) introduction of electrochemical processes into the water polishing stage and 3) UPW waste reclamation, all of which emphasize the enhanced responsibility of RO for producing cleaner permeate. Additionally, the noteworthy insights of RO technologies for the purpose of UPW are summarized, specifically focusing on RO configurations appropriate for UPW, scaling mitigation techniques for high recovery operation, and cleaning methods for maintenance. Lastly, this review concludes with future research directions for UPW production systems to achieve successful implementation. [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]

Pressure retarded osmosis (PRO) harnesses salinity gradient energy through the mixing of freshwater and saltwater, addressing the demand for sustainable energy sources. PRO typically utilizes river water or secondary wastewater as the feed solution, paired with seawater reverse osmosis (SWRO) brine as the draw solution. However, the limited availability of low-saline water presents a significant obstacle to energy generation. Therefore, the feasibility of a high-pressure PRO process utilizing seawater as the feed solution and hypersaline water as the draw solution was assessed to generate sustainable blue energy. Seawater has the potential to achieve the maximum extractable Gibbs-free energy through high-pressure PRO by maximizing the feed/draw ratio. The performance of the high-pressure PRO was theoretically evaluated, resulting in a tenfold increase in specific energy production compared to conventional SWRO-PRO due to the higher feed/draw ratio. However, high hydraulic pressure increased the membrane structural parameter and further reduced water flux and power density due to significant internal concentration polarization. Nevertheless, the high-pressure PRO process can achieve a power density exceeding 84 W/m2 when the structural parameter remains below 100 μm. The implications of the high-pressure PRO were further discussed to advance the concept of a blue circular economy, enhance environmental resilience, and promote sustainability. [Display omitted] • Feasibility of high-pressure PRO was investigated using seawater/hypersaline water. • Higher feed/draw ratio boosted energy production in the PRO process. • Seawater was assessed as a feed for high-pressure PRO for blue energy generation. • High-pressure operation raised the structural parameter reducing power density. • High-pressure PRO achieved >80 W/m2 at structural parameter <100 μm. [ABSTRACT FROM AUTHOR]

This study proposes two integrated electrochemical methods for the reuse of flue-gas desulfurization wastewater (FGDW): photoelectrochemical oxidation (PECO) using a self-doped black TiO 2 nanotube array (Black-TNA) catalyst and flow-electrode capacitive deionization (FCDI). The electrocatalytic activity and oxidative performance of the Black-TNA annealed at 600 °C were superior to those of the conventional Blue-TNA, as determined via Mott-Schottky and cyclic voltammetry plots. Furthermore, the removal of organic pollutants via PECO under sulfate-based conditions using the Black-TNA showed exceptional degradative results. Subsequently, FGDW was introduced to the FCDI system to evaluate its feasibility as a flow-electrode electrolytic solution in comparison with other synthetic electrolytes (NaCl, Na 2 SO 4 , and NaCl/Na 2 SO 4 composite), and was confirmed for its feasibility. Thus, the integrated PECO-FCDI system was demonstrated to be an effective means of removing organic pollutants and salts without the use of additional chemicals. [Display omitted] • Electrically-driven oxidation and desalination using FGDW • Novel black-TiO 2 nanotube array electrode for persulfate activation • Organic degradation via photoelectrochemical oxidation (PECO) using sulfate radicals • Flow-electrode capacitive deionization (FCDI) adopting FGDW as flow-electrode • Feasibility of a hybrid PECO-FCDI process for real FGDW treatment [ABSTRACT FROM AUTHOR]

Brine management systems are imperative for sustainable water supply and for securing valuable resources from desalination plants. The utilization of membrane brine concentrators has recently been focused on because of their high energy and cost efficiencies compared with those of thermal brine concentrators. In this paper, we investigated the recent candidates of membrane concentrators in terms of their future potential in brine management systems and categorized the types of utilized membranes into two groups: single solution passing (SSP)-type membranes and double solution passing (DSP)-type membranes. The current membrane technologies for manufacturing these types of membranes were critically analyzed, and future directions for membrane development towards efficient brine management systems were suggested. SSP-type membranes and their accompanying systems should be durable at pressures higher than 230 bar to utilize membrane brine concentrators. On the other hand, DSP-type membranes should exhibit high-pressure durability (higher than 40 bar) and low structure parameters (less than 50 μm). This study examines the current status of membrane systems and presents the technical specifications of membranes required for membrane brine management systems. [Display omitted] • Brine management systems using membrane concentrators are summarized and analyzed. • Two types of membranes are classified in the applications of membrane concentrators. • The required specifications of membranes are determined for membrane concentrators. • Future directions for membrane development are suggested towards brine management. [ABSTRACT FROM AUTHOR]

A series of MFI (modified fouling index) measurements were performed to evaluate and predict organic fouling potential and mechanism in seawater reverse osmosis (SWRO) desalination, by employing a multiple membrane array system (MMAS) in which microfiltration (MF), loose and tight ultrafiltration (UF) membranes were configured in a consecutive manner to determine the MFIs of particles, colloids, and organics. The results suggested that organic fractions manifested by colloid-MFI should be removed to control organic fouling effectively, as the organic fraction with MW ranging from 30 to 300 kDa led to the most severe fouling in RO experiments. The variations in fouling potential according to solution conditions (i.e., pH and Ca 2 + ) were also more accurately evaluated using multiple MFIs than with conventional SDI. This work demonstrated that the current fouling index, relying on a single membrane, could be improved by utilizing multiple membranes with different characteristics (e.g., pore size and hydrophobicity) to assess the fouling behavior of specific organic fractions. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membrane has been increasingly applied for brackish water treatment and often integrated to conventional water treatment consisting of coagulation, sedimentation, and filtration (CSF) processes. In this study, the corrosion potential of NF treated water was examined in lab-scale corrosion loop tests, and the optimum design of NF process blended with CSF treated water was proposed for iron pipe corrosion prevention. Severe iron corrosion was observed when exposed to NF treated water, which was manifested by more negative values of Langelier saturation index (LSI), mainly due to high removal of hardness (Ca 2 + ) and alkalinity (HCO 3 − ). Thus it was suggested that high corrosion potential by NF could be controlled by blending with CSF treated water. SEM, XRD, and XRF analyses clearly identified reduced corrosion, evidenced by less iron oxyhydroxides and more calcium carbonate on iron pipe surface, with decreasing NF treated water in blending. NF process simulation also demonstrated the improved stability of blended waters by decreasing flux and increasing recovery. Lastly, the LSI model reflecting blending ratio and NF membrane performance was newly developed for the design and operation of NF blending systems in order to lower the corrosion risk of pipe distribution systems through optimizing NF operating conditions. [ABSTRACT FROM AUTHOR]

A novel method to determine reverse draw and forward feed solute fluxes in forward osmosis (FO) membrane was developed to analyze FO performance more accurately. Specifically, apparent draw solute permeability (B d ) and feed solute permeability (B f ) were proposed, instead of relying on single solute permeability (B). Our results clearly demonstrated that both draw and feed fluxes were not well predicted with the solute permeability (B) measured by RO mode experiment, typically employed in FO membrane characterization. In this study, the draw and feed solute permeabilities were evaluated independently by the experimental protocols which simulated actual FO operation more closely. Much better agreement between experimental observations and theoretical predictions was obtained when both B d and B f were applied for the analysis of draw and feed solute fluxes, respectively. Thus, the utilization of apparent draw and feed solute permeabilities provides more precise assessment of draw solute loss and permeate water quality, which are very important for FO membrane process design and operation. [ABSTRACT FROM AUTHOR]

In this study, we investigate the performance of a capacitive deionization system using a flow-electrode composed of biochar prepared via pyrolysis at 700 °C in combination with activated carbon. Furthermore, we introduce lead, one of the leading heavy metals known, as a model pollutant to further assess the potential applicability of the system. By comparing the adsorption of multiple ions (i.e., sodium, chloride, lead) using activated carbon alone and in combination with the synthesized biochar under homogeneous conditions, enhancement in system performance by approximately 1.83-fold is indicated using the composite flow-electrode. The distinction of biochar was based on its superior electrical efficiency, with higher mass loading leading to further reduction in solution and charge transfer resistances by 80.8 and 98.7%, respectively, and thus the improvement in system deionization. Accordingly, adopting the optimum operational conditions (applied voltage of 0.9 V, and flow-electrode composition of AC35 B10), the FCDI process achieves outstanding performance in desalination and the further removal of heavy-metal lead ions. To the best of our knowledge, this study is the first to apply biochar as a new innovative flow-electrode material in an FCDI system. [Display omitted] • Integration of biochar for a potent novel flow-electrode of the FCDI process • Enhanced system current efficiency owing to the low impedance of biochar • Superior remediation of lead based on the surface affinity of biochar • Successful treatment of toxic lead-laden saline water via the biochar integrated FCDI [ABSTRACT FROM AUTHOR]

Abstract: Fertiliser-drawn forward osmosis (FDFO) desalination has been recently studied as one feasible application of forward osmosis (FO) for irrigation. In this study, the potential of membrane scaling in the FDFO process has been investigated during the desalination of brackish groundwater (BGW). While most fertilisers containing monovalent ions did not result in any scaling when used as an FO draw solution (DS), diammonium phosphate (DAP or (NH4)2HPO4) resulted in significant scaling, which contributed to severe flux decline. Membrane autopsy using scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD) analysis indicated that the reverse diffusion of DAP from the DS to the feed solution was primarily responsible for scale formation during the FDFO process. Physical cleaning of the membrane with deionised water at varying crossflow velocities was employed to evaluate the reversibility of membrane scaling and the extent of flux recovery. For the membrane scaled using DAP as DS, 80–90% of the original flux was recovered when the crossflow velocity for physical cleaning was the same as the crossflow velocity during FDFO desalination. However, when a higher crossflow velocity or Reynolds number was used, the flux was recovered almost completely, irrespective of the DS concentration used. This study underscores the importance of selecting a suitable fertiliser for FDFO desalination of brackish groundwater to avoid membrane scaling and severe flux decline. [Copyright &y& Elsevier]

Fouling behavior along the length of membrane module was systematically investigated by performing simple modeling and lab-scale experiments of forward osmosis (FO) membrane process. The flux distribution model developed in this study showed a good agreement with experimental results, validating the robustness of the model. This model demonstrated, as expected, that the permeate flux decreased along the membrane channel due to decreasing osmotic pressure differential across the FO membrane. A series of fouling experiments were conducted under the draw and feed solutions at various recoveries simulated by the model. The simulated fouling experiments revealed that higher organic (alginate) fouling and thus more flux decline were observed at the last section of a membrane channel, as foulants in feed solution became more concentrated. Furthermore, the water flux in FO process declined more severely as the recovery increased due to more foulants transported to membrane surface with elevated solute concentrations at higher recovery, which created favorable solution environments for organic adsorption. The fouling reversibility also decreased at the last section of the membrane channel, suggesting that fouling distribution on FO membrane along the module should be carefully examined to improve overall cleaning efficiency. Lastly, it was found that such fouling distribution observed with co-current flow operation became less pronounced in counter-current flow operation of FO membrane process. [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: A hybrid system that combines forward osmosis with a reverse osmosis seawater desalination process could reduce both energy requirements and environmental impacts by osmotic dilution of the seawater and concentrated brine with an impaired low salinity stream, such as treated wastewater effluent. In this study, we investigate the membrane fouling behavior in forward osmosis under conditions simulating the osmotic dilution process and the use of hydrodynamic methods without the use of cleaning chemicals, to control membrane fouling. Fouling runs with seawater or SWRO brine draw solution and deionized (DI) water feed solution showed insignificant water flux decline, which implies negligible effect of particulate and organic matter in the seawater/brine on fouling of the FO membrane support layer. Fouling of the membrane active layer was evaluated by using an enriched synthetic wastewater effluent containing a mixture of inorganic and organic foulants, focusing on the impact of permeate drag force on fouling layer formation. Our results demonstrate that higher permeate water flux causes an increase in concentration build-up of foulants at the membrane surface, thereby forming a dense inorganic/organic combined fouling layer during FO fouling runs. We also examined three hydrodynamic methods for minimizing FO membrane fouling in the osmotic dilution process: (1) applying shear force on the membrane surface by increasing the cross-flow velocity, (2) using a feed-channel spacer to induce turbulence, and (3) employing pulsed flow to remove foulants from the membrane surface. Our results show that these hydrodynamic methods substantially reduce fouling and flux decline rate. [Copyright &y& Elsevier]

[Display omitted] • Rapid degradation of organic pollutants via electrochemical oxidation on BDD anode. • Toxic chlorine oxyanions formed during electrolysis due to high current density. • Optimization of FCDI operation based on process performance and energy consumption. • Successful treatment of organic-rich high salinity water via hybrid ECO-FCDI system. This study aimed to assess the application of an electrochemical oxidation (ECO) and flow-electrode capacitive deionization (FCDI) sequential hybrid process for the treatment of high-concentration ions, organic pollutants (i.e., humic acid, alginate, benzoic acid, phenol, and 4-chlorophenol), and marine algae. The ECO system led to the rapid generation of reactive chlorine species (RCS) via anodic oxidation of the boron-doped diamond (BDD) electrode under optimum current in the NaCl-based feed solution, which caused the reduction of total organic carbon (TOC) and the degradation of algae cells. However, the formation of undesirable by-products (i.e., toxic perchlorate) was triggered by direct electrolysis. Concurrently, the optimal operational conditions of the FCDI system were evaluated based on the monitoring of process performance according to various parameters (i.e., applied voltage, electrode mass loading, electrolyte concentration in the flow electrode, feed solution concentration, and adsorption/desorption phase operation). Finally, the superiority of the ECO–FCDI hybrid process was confirmed and clearly demonstrated via the effective decomposition of organic compounds and the complete removal of toxic perchlorate by-product together with the effect of deionization. To the best of our knowledge, this work is the first to develop and apply the ECO–FCDI integrated process for the removal of a broad spectrum of pollutants (including both organics and ions) and to attain successful desalination. [ABSTRACT FROM AUTHOR]

Membrane processes have attracted considerable attention in the field of water treatment because of their excellent compactness, convenient operation and management, and relatively low energy consumption. However, fouling is a significant technical challenge. Electrically conductive membrane (ECM) technology has recently emerged as a promising alternative owing to its novel and effective mechanisms and outstanding fouling control efficiency. However, because ECM technology is still in the early stages of research, its maturity is low, and fundamental research on the mechanism is insufficient. In this critical review, the mechanisms of the ECM for fouling control were systematically elucidated and categorized as electrochemical oxidation and reduction, electrostatic interactions, and electrolysis. Subsequently, an extensive and comprehensive literature survey of ECM applications was conducted. The current state of the application and performance of ECM technology was evaluated. The operation and modification strategies of ECM research are discussed based on an accurate understanding and evaluation of the fundamental mechanisms and level of actual application of ECM technology for fouling control. Consequently, topics for future academic research and practical applications of the ECM are proposed. [Display omitted] • Fundamental mechanisms of ECM for fouling control are described and categorized. • Performances of ECM application to membrane processes are analyzed. • Recent operation and modification strategies of ECM are discussed. • Future directions for ECM research and applications are proposed. [ABSTRACT FROM AUTHOR]

In this study, a novel ZIF-8/CNT flow-electrode material was synthesized to be adopted in a flow-electrode capacitive deionization (FCDI) process for high selective recovery of lithium. Based on the presence of the CNT additive and innate active sites of the ZIF-8, the composite material exhibited superior physico- and electrochemical characteristics as compared to the conventional activated carbon (AC). Specifically, the intrinsic system and charge transfer resistances of ZIF-8/CNT were 0.70 and 1.95 % those of AC, which confirmed its exceptional conductance. Moreover, the pore aperture of ZIF-8/CNT was identified to be highly analogous to the size of a hydrated lithium ion, which was principal in securing exceptional lithium selectivity. Likewise, the FCDI operation with the ZIF-8/CNT flow-electrode was observed for superior deionization performance at 2.3-fold that of AC for all target lithium, sodium, nickel, and manganese ions. Especially, lithium selectivity in relation to sodium, nickel and manganese ions was also confirmed, at an average of 6.8-fold that of AC. Conclusively, operation of a three-stage system for the simultaneous capture and recovery of lithium exhibited successful deionization of the target composite solution at a removal of 89.1 %, and subsequent extraction of lithium at a recovery of 76.4 % that of its initial concentration and in the form of lithium hydroxide. [Display omitted] • Synthesis of ZIF-8/CNT as a novel flow-electrode material for FCDI • Enhanced electrochemical efficiency owing to lower intrinsic and charge transfer resistances • Superior lithium selectivity of ZIF-8/CNT based on its distinctive pore aperture • Successful simultaneous capture and recovery of lithium via operation of a three-stage system [ABSTRACT FROM AUTHOR]

Chemical absorption is widely employed to capture carbon dioxide (CO 2) for addressing climate change. While monoethanolamine (MEA) currently dominates as an absorption solvent, utilizing ammonia-rich wastewater offers advantages such as reduced costs, high absorption capacity, and the generation of ammonium carbamate. This study proposes an innovative fertilizer-drawn forward osmosis (FDFO)-membrane contactor (MC) hybrid system for economically and sustainably mitigating CO 2 emissions using ammonia-rich wastewater. First, ammonia-lean synthetic wastewater was concentrated through an FDFO system, using three fertilizers (KCl, monoammonium phosphate, and diammonium phosphate) as draw solutions. While KCl achieved a 45% ammonia dilution, diammonium phosphate yielded the highest concentration approximately 49%. Also, MCs were assessed for CO 2 absorption under various operational conditions. Increased liquid concentration and flow rates improved CO 2 capture efficiency, whereas higher CO 2 flow rates and concentrations resulted in an adverse effect. Furthermore, a simulation study of a hybrid FDFO-MC system was conducted to evaluate the feasibility and potential of the system. The results indicated that the FDFO-MC hybrid system has the potential to efficiently remove CO 2 if sufficient concentration and flow rate of ammonia-rich solution was secured at the FDFO outlet. This innovation addresses CO 2 emissions and wastewater challenges, adhering to circular economy principles. [Display omitted] • A new hybrid system was proposed for CO 2 capture using ammonia-rich wastewater. • The FDFO process for ammonia concentration was evaluated using three fertilizers. • DAP draw solution exhibited the highest ammonia concentration rate of 49%. • The CO 2 removal was enhanced by pH increase and ammonia solution concentration. • The optimized FDFO-MC integration could improve CO 2 removal efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Forward osmosis (FO) is a novel and emerging low energy technology for desalination. It will be particularly more attractive, if the draw solution separation and recovery are not necessary after FO process. The application of this new concept is briefly described here in this paper for the desalination of saline water for irrigation, using fertilizer as a draw agent. Instead of separating the draw solution from desalinated water, the diluted fertilizer draw solution can be directly applied for fertigation. We report the results on the commonly used chemical fertilizers as FO draw solution. Based on the currently available FO technology, about nine different commonly used fertilizers were finally screened from a comprehensive list of fertilizers and, their performances were assessed in terms of pure water flux and reverse draw solute flux. These results indicate that, most soluble fertilizers can generate osmotic potential much higher than the sea water. The draw solutions of KCl, NaNO3 and KNO3 performed best in terms of water flux while NH4H2PO4, (NH4)2HPO4, Ca(NO3)2 and (NH4)2SO4 had the lowest reverse solute flux. Initial estimation indicates that, 1kg of fertilizer can extract water ranging from 11 to 29L from sea water. [Copyright &y& Elsevier]

Abstract: The influence of pH and calcium ion concentrations on the organic fouling of reverse osmosis (RO) membranes was investigated under two distinguished ionic strengths representing surface water (i.e., 10mM) and seawater conditions (i.e., 600mM). Variations in flux decline with respect to the feed water pH and calcium concentrations under these ionic environments were compared. Organic foulants deposited on the membrane surface were collected and characterized in terms of specific UVA (SUVA) and fluorescence excitation and emission matrix (FEEM) in conjunction with XAD-8/4 resin fractionation. Flux-decline curves obtained by various feed water pH and calcium concentrations under the low ionic strength condition were quite different with each other, while flux-decline curves obtained at the seawater-level ionic strength was almost identical regardless of variations in the feed water pH and calcium concentration. SUVA and FEEM results showed that the characteristics of organic matters attached on the membrane surface at high ionic strengths were significantly different from those at low ionic strengths. SUVA values and FEEM images indicated that organic foulants at the seawater-level ionic strength were mostly hydrophobic. Consequently, enhanced hydrophobic interaction dominantly controlled the rate and the extent of organic fouling at seawater-level ionic strength where the impacts of feed water pH and calcium were significantly masked. [Copyright &y& Elsevier]

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]

Abstract: Fouled RO membranes from a real water treatment plant were analyzed biochemically to investigate the role of quorum sensing in controlling the rate and the extent of biofilm formation on the membrane surface. The results showed that 60% of bacterial species found on the fouled membrane surface contribute to biofilm formation through the active intraspecies as well as interspecies communication. It was confirmed that N-acylated homoserine lactones (AHL) produced from microorganisms involved in the quorum sensing transferred bacterial signal. In addition, flow field-flow fractionation (Fl-FFF) analyses demonstrated that most microorganisms contributing to biofilm formation through quorum sensing exhibited favorable adsorption on the membrane surfaces. The skewness values of these microorganisms were noticeably greater than those of organic macromolecules (i.e., natural organic matter) and particles. The study suggests that biochemical control of interfering quorum sensing could be an effective alternative to control biofilm formation and, thus, the reduction in biofouling of RO membranes. [Copyright &y& Elsevier]