Forward Osmosis Hollow Fiber Membranes Research Articles

Response to discussion of “Comprehensive simulation to uncover the ideal properties of a hollow fiber forward osmosis membrane module for the seawater desalination process”

Response to discussion of “Comprehensive simulation to uncover the ideal properties of a hollow fiber forward osmosis membrane module for the seawater desalination process”

Optimisation of multi-component inorganic salt composition as draw solute for preparation of concentrated tea extract using forward osmosis process

This work aims to identify an appropriate food-grade multi-component draw solute composition with enhanced permeate flux and reduced reverse solute flux. This study also highlights the role of the membrane in an efficient FO process. The osmotic properties of selected mixed-salt solutions of magnesium chloride, sodium chloride, sodium sulphate, and potassium chloride were investigated. Based on osmotic pressure, three multi-solute draw solute (DS) compositions were selected for preparation of concentrated tea extract using forward osmosis process. The role of membrane in the efficient membrane process was evaluated by comparing two commercially available hollow fibre forward osmosis membrane. Compared to salts with monovalent ions (such as NaCl and KCl), the SSF of the divalent ions salts (such as MgCl2 and Na2SO4) is reduced by 57.42% due to their larger hydrated radius. The optimised multi-component draw solute performance was compared with single-salt draw solute by maintaining almost the same osmotic pressure. The results of the lab-scale experimental studies revealed that compared to single salt DS (Jw = 17.66 L m−2 h−1 and specific salt flux, SSF = 1.53 g L−1), the identified multi-component DS provides an enhanced permeate flux (16.91 L m−2h−1) with significantly reduced SSF (0.86 g L−1).

Techno-economic assessment of forward osmosis as a pretreatment process for mitigation of scaling in multi-stage flash seawater desalination process

Thermal desalination processes suffer from the formation of scalants on the heat exchangers of the evaporator unit which negatively affect the process efficiency. This study evaluated the technical and economic feasibility of a pilot-scale forward osmosis (FO) process for the pretreatment of seawater to remove scaling ions before the multi-stage flash (MSF) process. A commercial hollow fiber FO membrane module was used in the pilot plant. The FO pilot plant used real seawater as feed solution and real MSF brine as draw solution. A maximum recovery rate of 27.7 % was achieved using a pressure gradient of 1.0 bar with the feed solution flowing through the membrane bore side and the draw solution flowing through the shell side with a temperature of 40 °C for both feed and draw streams. The FO membrane showed high rejection for scaling ions, where the rejection rate was almost 99 %, 96 %, and 92 % for sulfate, calcium, and magnesium, respectively. The specific power consumption of the FO process was about 0.01 kWh/m3. It was found that the water production cost for the FO process was almost 0.48 $/m3. The sensitivity analysis shows that the water production cost is highly sensitive to the water flux, especially at the lower range of water flux and high membrane cost. FO pretreatment provides a promising and economical solution for mitigating the scaling issue in MSF desalination plants.

Fabrication and characterization of inner selective antibiofouling forward osmosis hollow fiber membranes for simultaneous wastewater treatment and desalination

Forward osmosis (FO) hollow-fiber membranes were prepared by in situ thin layer assembly of polyethyleneimine (PEI) on antifouling PES-based porous nanocomposite membranes during membrane formation by spinning and phase inversion, via incorporation of surface-modified silver nanoparticles (NPs) in the dope solution and addition of PEI in the bore liquid; after cross-linking with glutaraldehyde the FO selective layer was obtained at the lumen surface while the shell surface had ultrafilter (UF) properties. This design enabled the utilization of the FO membranes in active layer facing draw solution (DS) orientation to employ maximum effective osmotic pressure, while the UF layer in combination with the antibacterial NPs was supposed to reduce fouling by the wastewater used as feed solution (FS). The quality of the active layer assembly was characterized using atomic force microscopy and scanning electron microscopy analyses, as well as salt rejection, structural parameter (S), and molecular weight cut-off (MWCO) measurements. The separation performance of these membranes was evaluated in an osmotic membrane bioreactor (OMBR) system, showing for the best FO nanocomposite membranes less than 10% fouling and flux reduction over 5 cycles of operation over a total period of 5 days. The best-suited membrane showed promising separation performance in the OMBR system by providing 43.4 LMH water flux and only around 0.2 g/l specific reverse salt flux (SRSF) with 1 M NaCl and DI water serving as DS and feed, respectively. This study focused also on distinctive performance criteria in combined FO and OMBR systems, such as the membrane’s potential in a pretreatment step of brine streams (used as DS) to provide proper feed composition for RO units and introduced a new specific performance index (SPI) for better characterization of FO membranes which summarizes all essential characteristics of the membrane application, instead of using existing structural parameter equations for membrane characterization. The best-suited FO membrane offered an SPI of 778.2 gl−1 m−2 h−1, meaning 778.2 g/l reduction of TDS in DS per unit membrane surface area per hour.

Comprehensive simulation to uncover the ideal properties of a hollow fiber forward osmosis membrane module for the seawater desalination process

Desalination with forward osmosis (FO) membranes is an attractive method, achieving an efficiency superior to that of reverse osmosis (RO), which has been improved for many decades, is difficult. Although many FO membranes have been developed, there are no guidelines in membrane development to make FO highly efficient. This paper quantitatively investigates whether FO desalination can be potentially superior to RO desalination, and, where so, we uncover the range of required membrane properties. The results show that it is difficult for the FO method with current hollow fiber modules to exhibit process performance superior to that of the present RO method with spiral-type membranes. However, if the water permeability of such membranes can be increased threefold, then the energy consumption of FO desalination can be reduced to 70 % of that of RO desalination. Thus, this study proposes guidelines regarding membrane properties, such as support layer thickness, water permeability, and rejection performance, which will be required when FO membranes are further advanced in the future.

Enhancing selectivity of novel outer-selective hollow fiber forward osmosis membrane by polymer nanostructures

An ideal forward osmosis (FO) membrane module for osmotic membrane bioreactor (OMBR) application would have high packing density, low reverse solute flux and low fouling propensity. Recently, an outer-selective hollow fiber forward osmosis (HFFO) membrane has been developed to simultaneously improve packing density and reduce fouling propensity. However, a high reverse solute flux of the HFFO membrane still generates a salinity build-up in the reactor and remains the main challenge of this technology. To tackle this problem, we successfully improved the selectivity of an outer-selective HFFO membrane by incorporating a prior developed formulation based on Pluronic® nanostructures containing water selective proteins into the active layer of the membrane. The assimilation of these nanostructures in the membrane resulted in a significant decrease of the specific reverse solute flux from 0.36 ± 0.01 gL-1 to 0.12 ± 0.02 gL-1 with no significant decrease in water flux. Also, urea was selected as a challenging solute to investigate the selectivity of the developed membranes. In comparison with the pristine membranes, membranes containing nanostructures presented a superior rejection of urea from 87.7 ± 2.0 % to 95.2 ± 0.9 %. The developed membranes are able to be used for future OMBR application tests to prove feasibility of the process. Thus, this study can lead to the development of new membranes suitable for efficient and long-term operation in OMBR configurations. Additionally, the nanostructures investigated here can be used for different thin-film composite membranes as an additive to improve membrane selectivity.

Ecological Risk Evaluation and Removal of Emerging Pollutants in Urban Wastewater by a Hollow Fiber Forward Osmosis Membrane

Forward osmosis (FO) is a promising technology for the treatment of urban wastewater. FO can produce high-quality effluents and preconcentrate urban wastewater for subsequent anaerobic treatment. This membrane technology makes it possible to eliminate the pollutants present in urban wastewater, which can cause adverse effects in the ecosystem even at low concentrations. In this study, a 0.6 m2 hollow fiber aquaporin forward osmosis membrane was used for the treatment of urban wastewater from the Valladolid wastewater treatment plant (WWTP). A total of 51 Contaminants of Emerging Concern (CECs) were investigated, of which 18 were found in the target urban wastewater. They were quantified, and their ecotoxicological risk impact was evaluated. Different salts with different concentrations were tested as draw solutions to evaluate the membrane performances when working with pretreated urban wastewater. NaCl was found to be the most appropriate salt since it leads to higher permeate fluxes and lower reverse saline fluxes. The membrane can eliminate or significantly reduce the pollutants present in the studied urban wastewater, producing water without ecotoxicological risk or essentially free of pollutants. In all cases, good recovery was achieved, which increased with molecular weight, although chemical and electrostatic interactions also played a role.

Investigation of thin-film composite hollow fiber forward osmosis membrane for osmotic concentration: A pilot-scale study

Investigation of thin-film composite hollow fiber forward osmosis membrane for osmotic concentration: A pilot-scale study

Transport mechanisms behind enhanced solute rejection in forward osmosis compared to reverse osmosis mode

Forward osmosis (FO) as emerging technology for water treatment was reported to exhibit higher solute rejections compared to reverse osmosis (RO). In this work, the rejection of two uncharged organic compounds (nicotinamide, caffeine) were investigated the first time in low-pressure reverse osmosis (LPRO) mode and FO under similar process conditions utilizing the same hollow fiber forward osmosis membrane modules. FO consistently showed higher rejection than LPRO mode for both nicotinamide (FO: 94.8%, LPRO: 85.5%) and caffeine (FO: 99.9%, LPRO: 99.2%). To elucidate the influence of draw solute on the rejection, different salts (NaCl, MgCl2, MgSO4), concentrations, and draw flow rates were investigated. A rise in draw concentration increased rejection in FO for all salts (RNaCl:94.1→97.2%,RMgCl2:94.5→97.5%,RMgSO4:90.0→94.7%) indicating an enhancement of rejection due to the presence of salt on the permeate side of the membrane. Two theories are proposed: While the resistance for feed solute transport could be increased due to the counter-directed reverse solute flux and the presence of salt in the support layer, the driving force for feed solute diffusion might be lowered due the presence of an ionic compound on the permeate side of the membrane.

Forward osmosis system design and optimization using a commercial cellulose triacetate hollow fibre membrane module for energy efficient desalination

This study is aimed at developing system mathematical design models to simulate and optimize a full scale forward osmosis (FO) for a hollow fibre membrane module for energy efficient desalination. Experimental data from a commercial outer selective CTA hollow fibre FO membrane module was used for validation. Less than 10% difference between the simulation and experimental results were observed which validated the reliability of the models. Simulation and design were performed for a 1000 m3/day FO plant using 0.6 M NaCl as draw solution (DS) (~seawater) and 0.02 M NaCl feed solution (FS) (~MBR effluent) to produce 0.25, 0.2 and 0.15 M NaCl diluted seawater to reduce the energy consumption of downstream pressure driven desalination process. A single element parallel module arrangement was found more suitable for this commercial hollow fibre membrane element. Finally, the numerical simulations revealed that to achieve 0.25, 0.20 and 0.15 M final DS concentrations, the optimum number of modules required were 370, 435 and 555 respectively considering membrane cost and energy consumption. The FO system using the commercial CTA hollow fibre module was found more energy efficient than a commercial TFC spiral wound membrane module.

Sugarcane juice concentration using a novel aquaporin hollow fiber forward osmosis membrane

In this work, the performance of a commercially available aquaporin HFFO membrane was studied for concentrating the sugarcane juice by adopting appropriate UF pretreatment technique. The influences of draw and feed solution flowrates, draw concentration and its direction of flow such as co-current or counter-current on water and reverse solute flux was evaluated in batch mode. The specific reverse solute flux for counter-current mode was found to be less compared to co-current mode of operation. Improved draw solution (NaCl) flowrate increased the water flux with reduced specific reverse solute flux. The FS concentration ratio was 1.65 within 12 min of batch FO operation by using 100 g L−1 draw solution. Membrane fouling was studied systematically with appropriate membrane cleaning strategy. The effect of UF clarified and raw sugarcane juice on FO membrane fouling was calculated and it was found that raw sugarcane juice led to severe membrane fouling that reduced water permeability after 60 min of operation. The membrane fouled by UF clarified juice was able to regenerate by DI water wash for 30 min, however in the case of membrane fouled by raw juice, an additional 0.1 M NaOH wash was required.

Study of the rejection of contaminants of emerging concern by a biomimetic aquaporin hollow fiber forward osmosis membrane

Forward osmosis (FO) plays an increasingly important role in membrane processes because of its advantages compared to traditional pressure-driven membrane processes. There are different types of water-selective FO membranes. In this study, a biomimetic hollow fiber module comprising an active layer of polyamide thin film composite (TFC) with integrated aquaporin proteins and an effective area of 0.6 m2 is used to study the rejection of 24 Contaminants of Emerging Concern (CECs). The rejections obtained for all the contaminants studied were higher than 93 % and for 19 of them rejections of up to 99 % were reached. It was observed that although all the tested compounds showed rejections very close to 100 %, they were not completely recovered in the feed solution which makes the retention within the membrane an important factor to be considered. Hence, two membrane rinses were necessary after each membrane operation to completely recover each contaminant. The results were analyzed considering the physicochemical properties (molecular weight, charge and hydrophobicity) of the contaminants.

Removal of Emerging Pollutants in Urban Wastewater Through Their Concentration by Hollow Fiber Forward Osmosis Membrane

Removal of Emerging Pollutants in Urban Wastewater Through Their Concentration by Hollow Fiber Forward Osmosis Membrane

Pilot-scale investigation of flowrate and temperature influence on the performance of hollow fiber forward osmosis membrane in osmotic concentration process

Forward osmosis (FO) relying on the osmotic pressure difference across semi-permeable membrane draws permeate by the effect of saline draw solution (DS) turning diluted and leaving the feed solution (FS) concentrated. However, the energy intensive step of DS recovery makes FO a challenging process. The energy benefit of FO emerges when recovery step is obviated and FO is applied as an osmotic concentration (OC) process. OC implementations for volume reduction are still at bench-scale and the investigation at larger scale is among the breakthroughs. In this paper, the performance of hollow fiber (HF) membrane in pilot-scale OC process for reducing volume of feed was investigated. The impact of operating conditions such as flowrates and temperature was evaluated. FS and DS flowrates of 1.35 and 0.35 L.min-1 respectively are optimum conditions with 75% feed recovery and 1.90 LMH water flux. Reverse solute flux increased at higher flowrates. Results indicated the role of high DS flowrate and temperature in improving the performance. DS flowrate of 0.35 L.min-1 at constant FS flow of 1.10 L.min-1 and 27 °C was most suitable for achieving 84.5% feed recovery and 1.82 LMH water flux. Above all, the long-term performance of OC pilot-plant was demonstrated through 48 h of continuous operation where stable flux trend at an average water flux of 1.66 LMH was successfully achieved. Lastly, the permeability coefficients of HF membrane were enhanced at higher temperature.

Effect of Additives on the Performance of PPBES Composite Forward Osmosis Hollow Fiber Membranes.

A polyamide composite forward osmosis (FO) hollow fiber membrane was successfully prepared with a novel copoly(phthalazinone biphenyl ether sulfone) (PPBES) polymer. Effects of different additives including ethylene glycol methyl ether (EGME) and lithium chloride anhydrous (LiCl) in the dope solution on the morphologies and properties of PPBES support membranes and composite FO hollow fiber membranes were investigated. With the increase of EGME content in the dope solution, the water flux of PPBES support membranes and FO hollow fiber membranes decreased. When LiCl was added into the dope solution, the water flux of FO hollow fiber membranes improved significantly with the increase of LiCl content. Additionally, the FO performance of the PPBES membrane was further optimized by adding triethylamine (TEA) in the interfacial polymerization (IP) process. In comparison with other FO membranes, the novel PPBES composite FO hollow fiber membrane displayed a remarkably high water flux of 45.3 L/m2 h and a low specific reverse salt flux of 0.15 g/L.

Effect of the support layer morphological structure on the performance of forward osmosis hollow fiber membranes

A thin-film polyamide layer was synthesized on three different hollow-fiber support layers, each of which possess different morphological structures (i.e., sponge-like structures (SM-1), finger-like macrovoid close to the outer surface (SM-2), and middle-partitioned finger-like structures (SM-3)). In this work, we found that forward osmosis (FO) performance of thin-film composite (TFC) membranes could be significantly affected by their sub-layer morphology. During FO tests, SM-1 showed the highest water permeability of 0.742 LMH/bar followed by SM-3 and SM-2. In addition, SM-1 exhibited the lowest solute permeability of 0.039 LMH, followed by SM-2 and SM-3. To more systematically evaluate the effect of the support layer structures on the performance of TFC FO membranes, the structural parameters (S) of the membranes were estimated using the dusty gas model (DGM) prior to interfacial polymerization on the support layers. The S values of the support layers obtained from the DGM method are in accord with the FO membrane performance. Although the conventional S parameter determination method showed relatively similar values with the DGM method, the overall trend corresponds, confirming that the smaller S value is related to a smaller internal concentration polarization decrease. Moreover, this study clearly demonstrates that the support layer needs to be considered alongside the active layer of TFC FO membranes, and that a sponge-like support layer can be a better option for high-performance FO TFC membranes.

Evaluating the Feasibility of Forward Osmosis in Diluting RO Concentrate Using Pretreatment Backwash Water.

Forward osmosis (FO) is an excellent membrane process to dilute seawater (SW) reverse osmosis (RO) concentrate for either to increase the water recovery or for safe disposal. However, the low fluxes through FO membranes as well the biofouling/scaling of FO membranes are bottlenecks of this process requiring larger membrane area and membranes with anti-fouling properties. This study evaluates the performance of hollow fibre and flat sheet membranes with respect to flux and biofouling. Ferric hydroxide sludge was used as impaired water mimicking the backwash water of a filter that is generally employed as pretreatment in a SWRO plant and RO concentrate was used as draw solution for the studies. Synthetic salts are also used as draw solutions to compare the flux produced. The study found that cellulose triacetate (CTA) flat sheet FO membrane produced higher flux (3–6 L m−2 h−1) compared to that produced by polyamide (PA) hollow fibre FO membrane (less than 2.5 L m−2 h−1) under the same experimental conditions. Therefore, long-term studies conducted on the flat sheet FO membranes showed that fouling due to ferric hydroxide sludge did not allow the water flux to increase more than 3.15 L m−2 h−1.

Fabrication of nanocomposite forward osmosis hollow fiber membrane for low reverse salt flux by modification of active layer via co-extrusion with graphene oxide

Fabrication of nanocomposite forward osmosis hollow fiber membrane for low reverse salt flux by modification of active layer via co-extrusion with graphene oxide

Role of Operating Conditions in a Pilot Scale Investigation of Hollow Fiber Forward Osmosis Membrane Modules

Role of Operating Conditions in a Pilot Scale Investigation of Hollow Fiber Forward Osmosis Membrane Modules

Energy efficiency of hollow fibre membrane module in the forward osmosis seawater desalination process

This study provided new insights regarding the energy efficiency of hollow fibre forward osmosis modules for seawater desalination; and as a consequence an approach was developed to improve the process performance. Previous analysis overlooked the relationship between the energy efficiency and operating modes of the hollow fibre forward osmosis membrane when the process was scaled-up. In this study, the module length and operating parameters were incorporated in the design of an energy-efficient forward osmosis system. The minimum specific power consumption for seawater desalination was calculated at the thermodynamic limits. Two FO operating modes: (1) draw solution in the lumen and (2) feed solution in the lumen, were evaluated in terms of the desalination energy requirements at a minimum draw solution flow rate. The results revealed that the operating mode of the forward osmosis membrane was important in terms of reducing the desalination energy. In addition, the length of the forward osmosis module was also a significant factor and surprisingly increasing the length of the forward osmosis module was not always advantageous in improving the performance. The study outcomes also showed that seawater desalination by the forward osmosis process was less energy efficient at low and high osmotic draw solution concentration and performed better at 1.2–1.4 M sodium chloride draw solution concentrations. The findings of this study provided a platform to the manufacturers and operators of hollow fibre forward osmosis membrane to improve the energy efficiency of the desalination process.