FO Membrane Research Articles

Water and nutrient recovery by a novel moving sponge – Anaerobic osmotic membrane bioreactor – Membrane distillation (AnOMBR-MD) closed-loop system

For the first time, a novel sponge-based moving bed-anaerobic osmosis membrane bioreactor/membrane distillation (AnOMBR/MD) system using mixed Na3PO4/EDTA–2Na as the draw solution was employed to treat wastewater for enhanced water flux and reduced membrane fouling. Results indicated that the moving sponge-AnOMBR/MD system obtained a stable water flux of 4.01 L/m2 h and less membrane fouling for a period lasting 45 days. Continuous moving sponge around the FO module is the main mechanism for minimizing membrane fouling during the 45-day AnOMBR operation. The proposed system’s nutrient removal was almost 100%, thus showing the superiority of simultaneous FO and MD membranes. Nutrient recovery from the MF permeate was best when solution pH was controlled to 9.5, whereby 17.4% (wt/wt) of phosphorus was contained in precipitated components. Moreover, diluted draw solute following AnOMBR was effectively regenerated using the MD process with water flux above 2.48 L/m2 h and salt rejection > 99.99%.

Behaviour of Aquaporin Forward Osmosis Flat Sheet Membranes during the Concentration of Calcium-Containing Liquids.

This study aims to examine the scaling and performance of flat sheet aquaporin FO membranes in the presence of calcium salts. Experiments showed that the application of calcium sulphate (CaSO4) resulted in an 8–78% decline in the water flux. An increase in the cross-flow velocity from 3 to 12 cm/s reduced the decline in the flux by 16%. The deposition of salt crystals on the membrane surface led to the alteration in the membrane’s intrinsic properties. Microscopy, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and X-Ray fluorescence (XRF) analyses confirmed measurements of the zeta potential and contact angle. The use of a three-salt mixture yielded severe scaling as compared with the application of calcium sulphate dehydrate (CaSO4 × 2H2O), i.e., a result of two different crystallisation mechanisms. We found that the amount of sodium chloride (NaCl), saturation index, cross-flow velocity, and flow regime all play an important role in the scaling of aquaporin FO flat sheet membranes.

Customized thin and loose cake layer to mitigate membrane fouling in an electro-assisted anaerobic forward osmosis membrane bioreactor (AnOMEBR)

Anaerobic forward osmosis membrane bioreactor (AnOMBR) is a potential wastewater treatment technology, due to its low energy consumption and high effluent quality. However, membrane fouling is still a considerable problem which causes dwindling of water flux and shortening the membrane lifetime. In this study, electro-assisted anaerobic forward osmosis membrane bioreactor (AnOMEBR) was developed to treat wastewater and mitigate membrane fouling, in which the conductive FO membrane was used both as the separation unit and cathode. The formation, development and alleviation of membrane fouling in AnOMEBR were investigated. The results showed that the soluble microbial products (SMP) content and the proteins/polysaccharides (PN/PS) value in AnOMEBR were 26% and 15% lower than that in AnOMBR, respectively. The absolute value of Zeta of sludge mixture in AnOMEBR was 1.2 times that of the AnOMBR. The increase in the interaction between the membrane surface and the negatively charged foulants could inhibit the adsorption of foulants on membrane surface in the initial stage of membrane fouling. The strong interaction among foulants further affected the composition, structure and thickness of the cake layer on the FO membrane surface. AnOMEBR with a shorter hydraulic retention time, a higher organic loading rate and a lower osmotic pressure difference, could still obtain a lower flux decline rate of 0.063 LMH/h, which was 35.7% lower than AnOMBR. The wastewater treatment capacity of AnOMEBR was nearly 1.5 times that of the AnOMBR. This work provides an efficient strategy for mitigating membrane fouling and improving wastewater treatment capacity.

Effect of Spacer Configuration on the Characteristics of FO Membranes: Alteration of Permeation Characteristics by Membrane Deformation and Concentration Polarization.

Membrane deformation is a significant problem in osmotically driven membrane processes, as it restricts practical operating conditions and reduces overall process performance due to unfavorable alteration of membrane permeation characteristics. In this respect, a spacer plays a crucial role, as it dictates the form and extent of membrane deformation in association with concentration polarization (CP), which is also influenced by spacer-induced hydrodynamic behavior near the membrane surface. These two roles of spacers on membrane permeation characteristics are inherently inseparable with the coexistence of hydraulic and osmotic pressures. Here, we suggest a novel analytical method to differentially quantify the proportions of effective osmotic pressure drop caused by membrane deformation and CP. Furthermore, we tested two different FO membranes with three different spacer configurations to define and discuss different forms of membrane deformation and their effects on membrane permeation characteristics. The differential analysis revealed the effect of spacer configuration on effective osmotic pressure drop in membrane deformation (up to ∼201% of variation) is much greater than that in CP (up to ∼20.1% of variation). In addition, a combined configuration of a feed spacer and tricot spacer demonstrated its ability of mitigating membrane deformation with lower selectivity loss and channel pressure drop under pressurization.

Novel Thermal Desalination Brine Reject-Sewage Effluent Salinity Gradient for Power Generation and Dilution of Brine Reject

Salinity gradient resource presents an essential role for power generated in the process of pressure-retarded osmosis (PRO). Researchers proposed several designs for coupling the PRO process with the desalination plants, particularly reverse osmosis technology for low-cost desalination but there is no study available yet on the utilization of the concentrated brine reject from a thermal desalination plant. This study evaluates the feasibility of power generation in the PRO process using thermal plant brine reject-tertiary sewage effluent (TSE) salinity gradient resource. Power generation in the PRO process was determined for several commercially available FO membranes. Water flux in Oasys Forward Osmosis membrane was more than 31 L/m2h while the average water flux in the Oasys module was 17 L/m2h. The specific power generation was higher in the thin film composite (TFC) membranes compared to the cellulose triacetate (CTA) membranes. The specific power generation for the Oasys membrane was 0.194 kWh/m3, which is 41% of the maximum Gibbs energy of the brine reject-TSE salinity gradient. However, the Hydration Technology Innovation CTA membrane extracted only 0.133 kWh/m3 or 28% of Gibbs free energy of mixing for brine reject-TSE salinity gradient. The study reveals the potential of the brine reject-TSE salinity gradient resource for power generation and the dilution of brine reject.

Evaluating the performance of inorganic draw solution concentrations in an anaerobic forward osmosis membrane bioreactor for real municipal sewage treatment

Sewage can become a valuable source if its treatment is re-oriented for recovery. An anaerobic forward osmosis membrane bioreactor (AnOMBR) was developed for real municipal sewage treatment to investigate performance, biogas production, flux change and mixed liquor characteristics. The AnOMBR had a good treatment capacity with removal ratio of chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus more than 96%, 88%, 89% and almost 100%. Although high DS concentration increased the initial flux, it caused rapid decline and poor recoverability of FO membrane flux. Low DS concentration led to too long hydraulic retention time, thus resulting in a low reactor efficiency. Additionally, it was observed that salt, protein, polysaccharide and humic acid were all accumulated in the reactor, which was not conducive to stable long-term operation. Based on the characteristics of membrane fouling, salt accumulation and AnOMBR performance, the optimal DS of 1 M NaCl solution was selected.

Impact of Hydrodynamics on the First Stages of Biofilm Formation in Forward Osmosis with Spacers.

Initial deposition of bacteria is a critical stage during biofilm formation and biofouling development in membrane systems used in the water industry. However, the effects of hydrodynamic conditions on spatiotemporal deposition patterns of bacteria during the initial stages of biofilm formation remain unclear. Large field epifluorescence microscopy enabled in situ and real-time tracking of Bacillus subtilis in a forward osmosis system with spacers during the first 4 h of biofilm formation. This study quantitatively compares the spatiotemporal deposition patterns between different hydrodynamic conditions: high and low permeate water flux (6 or 30 L m-2 h-1) as well as high and low crossflow velocity (1 or 14 cm s-1). Low crossflow velocity and high permeate water flux maximized bacterial attachment to the membrane surface, which was 60 times greater (6 × 103 cells mm-2) than at high crossflow velocity and low permeate water flux (<100 cells mm-2). Imaging at 30 s intervals revealed three phases (i.e., lag, exponential, and linear) in the development of deposition over time. Quantification of spatial deposition patterns showed that an increase in the ratio of permeate water flux to crossflow velocity led to a homogeneous deposition, while a decrease had the opposite effect. The insights of this research indicate that an appropriate choice of hydrodynamic conditions can minimize bacteria accumulation prior to biofilm formation in new and cleaned FO membrane systems treating water of high fouling propensity.

Forward osmosis–membrane distillation hybrid system for desalination using mixed trivalent draw solution

Finding suitable draw solutions is still a major problem when developing FO technologies. This study represents the first time a mixed trivalent draw solution containing of EDTA–2Na and Na3PO4 was systemically studied for FO performance. The objective here was to achieve simultaneously low reverse salt flux and high water flux. The FO results showed that the mixed trivalent draw solution-based 0.3 M EDTA–2Na and 0.55 M Na3PO4 underwent higher water flux (Jw = 9.17 L/m2⋅h) than that of pure 0.85 M EDTA-2Na (Jw = 7.02 L/m2⋅h) due to its lower viscosity. Additionally, the specific reverse salt flux caused by mixing 0.3 M EDTA–2Na with 0.55 M Na3PO4 draw solution was only 0.053 g/L using DI water as the feed solution. Donnan equilibrium force and formed complexation of [EDTANa]3-, [HPO4Na]- with the FO membrane are believed to constitute the main mechanism for minimizing salt leakage from the mixed draw solution. Moreover, the FO desalination process utilizing the mixed trivalent draw solution achieved water fluxes of 6.12 L/m2⋅h with brackish water (TDS = 5000 mg/L) and 3.10 L/m2⋅h with seawater (TDS = 35,000 mg/L) as the feed solution. Lastly, diluted mixed trivalent draw solution following the FO process was effectively separated using the MD process with salt rejection >99.99% at a mild feed temperature of 55 °C.

The role of polyvinyl butyral additive in forming desirable pore structure for thin film composite forward osmosis membrane

A thin-film composite forward osmosis (TFC-FO) membrane was developed by combining a new substrate consisting of cellulose acetate butyrate (CAB) and polyvinyl butyral (PVB) with the conventional polyamide active layer. The incorporation of the PVB additive (0–4 wt%) was to improve the hydrophilicity and alter the pore formation mechanism of the substrate to reduce the internal concentration polarization (ICP) effect in FO. The results showed that promising structural parameters of the CAB/PVB substrate such as A value (1.08 L m−2 h−1 bar−1) and S value (363.5 μm) could be obtained for the M2 substrate with 2 wt% PVB, due to the combined effect of finger-like pores and high porosity with high pore connectivity. The evaluation of the TFC-FO membranes showed that the water flux of the TFC-M2 was up to 27.5 L m−2 h−1 with 1 M NaCl draw solution in active-layer facing draw solution (AL-DS) mode, which was 40% and 130% flux enhancement compared to the reported commercial CTA and pure CAB control TFC membrane, respectively, with lower specific salt flux Js/Jw (0.35 g/L). The fouling experiments using model feed containing BSA foulant showed that the TFC-M2 was almost unaffected (98%) by the dilutive ICP effect in the active-layer facing feed solution (AL-FS) mode; while it also exhibited the highest flux recovery of 88% in the AL-DS mode. Overall, the total mass transfer resistance Rt of the TFC-M2 was the lowest compared to all as-prepared TFC-FO membranes, indicating the key role of the PVB additive in tuning the CAB substrate structure for designing high performance FO membranes.

A Novel RO/FO Hybrid Seawater Desalination System and Its Software Implementation

Seawater reverse osmosis (SWRO) desalination technology is being widely used in coastal countries to meet the supply demand of fresh water for living and industry using. Despite major advancements in SWRO technology, the desalination industry is still facing significant practical issues. Generation of higher volumes of pretreatment sludge and low overall water recovery are the two of the major issues. A novel hybrid reverse osmosis-forward osmosis (RO/FO) system is proposed to overcome the above two drawbacks. Mass balance calculations based on laboratory experiments have been used to predict increased water recovery and reduced pretreatment sludge volume arising from large scale (340,000 m3/day of intake) and small scale (15,000 m3/day of intake) hybrid SWRO desalination plants. After that, we developed a software for the RO/FO hybrid system in MATLAB, and different water flux values were studied to verify the system. It was packaged into executable files and it can run smoothly on computers without MATLAB installed. By setting different operating parameters in the RO/FO system software interface, the percentage reduction of pretreatment sludge volume, increase in overall RO water recovery, FO membrane area required and dilution in RO reject can be estimated quickly in a variety of different options.

Calcium carbonate scaling in forward osmosis for textile reverse osmosis concentrate treatment

The reverse osmosis concentrate (ROC) of textile wastewater produced in the process of the reverse osmosis usually has a high concentration of salts and organic matters, and is hard to be biodegraded. In this study, forward osmosis process was used for reusing ROC of real textile wastewater, and the effect of sodium chloride (NaCl) and ammonium bicarbonate (NH4HCO3) on the water flux and the recovery of ROC were then investigated. The results showed that the water recovery could reach 90 % when 2 M NaCl was used as DS. The calcium carbonate (CaCO3) scaling could be both observed using NaCl and NH4HCO3 as DS. Compared to the DS of NaCl, the CaCO3 precipitation occurred much earlier when NH4HCO3 was used as DS. Due to the reverse diffusion of HCO3−, the concentration of Ca2+ in the concentrated ROC was significantly lower than 3 mg/L. Although the FO membrane was covered by CaCO3 scaling, the water flux was slightly affected by it. In addition, the water flux showed no difference through four cycles of FO tests during which the FO membrane was not cleaned after each cycle of test. This finding provided the possibility of applying FO process for the near-zero liquid discharge of textile wastewater.

Moving from lab to pilot scale in forward osmosis for pesticides rejection using aquaporin membranes

Often FO experiments are carried out with the prevalent FO lab-scale setup using a moderate-sized flat sheet membrane. This necessitates spending funds on providing FO apparatuses and using higher area of FO membranes associated with a larger amount of chemicals to evaluate the performance of the FO process in rejection of compounds of interest. In this paper, we used two different FO setups, a typical lab-scale system using flat sheet aquaporin membrane as well as a small pilot-scale setup using hollow fiber aquaporin membrane, to remove three pesticides from water: 2–6 Dichloro-benzamide (BAM), 2-methyl-4-chlorophenoxyaceticacid (MCPA), and 2-(4-Chloro-2-methylphenoxy)propionic acid (MCPP). The obtained rejection data of BAM was compared to our previous study on aquaporin FO membrane using a tiny FO system to investigate the effect of going from a tiny lab-scale to a pilot-scale setup. The diffusion-controlled rejection of BAM was found to be 93–94% using the standard lab-scale flat sheet membrane system while that was 98.7% using the pilot-scale hollow fiber membrane which is in accordance to our preliminary result of >97% with the tiny system. This study confirms the hypothesis that we can employ a very small piece of membrane and accurately use it to estimate the rejection performance of a pilot-scale FO membrane system. This finding allows for a cost-effective and quick test of a large number of molecules by most importantly, the use of a tiny piece of FO membrane. Moreover, both systems, in particular, the hollow fiber setup demonstrated an excellent rejection capability for the charged phenoxy acid herbicides by having rejection values of 99.2% for both MCPA and MCPP.

Feasibility of concentrating textile wastewater using a hybrid forward osmosis-membrane distillation (FO-MD) process: Performance and economic evaluation

The forward osmosis-membrane distillation (FO-MD) hybrid process has shown great promise in achieving zero liquid discharge in the textile industry, recovering valuable dye molecules while producing large amounts of clean water. However, the progress of this technology seems to have stagnated with the direct coupling of commercial asymmetric FO and MD membranes, because water management in the system is found to be rather complicated owing to the processing of the different membranes. Herein, we propose, for the first time, an FO-MD hybrid process using a custom-made self-standing and symmetric membrane and a hydrophobic polytetrafluoroethylene membrane in the FO and MD units, respectively. Three types of operation modes were investigated to systematically study the process performance in the concentration treatment of model textile wastewater; two commercial FO membranes were also tested for comparison. Owing to its low fouling propensity and lack of an internal concentration polarization effect, the water transfer rate of our symmetric FO membrane quickly reaches equilibrium with that in the MD unit, resulting in continuous and stable operation. Consequently, the hybrid process using the symmetric FO membrane was found to consume the least energy, as indicated by its lowest total cost in both lab- and large-scale systems. Overall, our study provides a new strategy for using a symmetric FO membrane in the FO-MD hybrid process and highlights its great potential for use in the treatment of textile wastewater.

Direct preparation of dialysate from tap water via osmotic dilution

Preparation of dialysate for hemodialysis (or dialysis) requires dilution of the dialysis concentrate with purified water. Present practice contains two steps: first to purify water, and then water is transported to clinic to mix with the dialysate concentrate before treatment. As a new forward osmosis dialysis hybrid process, based on osmotic dilution, is evaluated for decentralized health care systems. A commercial cellulose triacetate (CTA) and a tailor-made thin film composite (TFC) polyamide FO membranes were examined. The rejection of salts in tap water by the FO membranes was investigated, and the real rejections of various ions as a function of permeate flux were well described by using a irreversible thermodynamic model. The hollow fiber TFC FO membrane showed higher water flux and lower reverse salt flux than the CTA membrane in diluting process. Both steric hindrance and electrostatic repulsion explained the rejection behavior of the membranes to the ions. Higher rejections of anions were obtained than cations, which was attributed to the anions selection characteristics of the membranes. No obvious foulings or scalings were observed in a relatively long time osmotic dilution process over 5 repeated cycles. The stable, high efficient osmotic dilution process in hemodialysis holds a strong promise in reducing the consumption of purified water or even eliminating the water purification step. This work provides a potentially new platform hemodialysis which can be portable and implementable away from major hospitals and major clinics.

Forward osmosis membrane bioreactor using Bacillus and membrane distillation hybrid system for treating dairy wastewater

ABSTRACT Wastewater recycling is one of the best ways to alleviate water scarcity and water/wastewater pollution. The dairy industry is the largest industrial food wastewater source in many countries. In this study, we used a forward osmosis membrane bioreactor (FOMBR) and membrane distillation (MD) hybrid system to recycle dairy wastewater. And we developed a new Bacillus-FOMBR inoculated with salt-tolerant Bacillus sludge to protect against the negative effects of accumulated salt on sludge characteristics, microbial community and treatment effectiveness, and to alleviate membrane biofouling. A laboratory-scale FOMBR-MD experiment was operated for 40 days and water flux, salinity change, sludge characteristics, microbial community, nutrient removal efficiency, and FO membrane fouling were investigated. The Bacillus-FOMBR showed a small decrease in biomass concentration, and the hybrid system removed almost 100% of the contaminants. High-throughput sequencing analysis indicated that Pirellula and Hyphomicrobium species dominated the Bacillus-FOMBR, which are obliged to perform heterotrophic nitrification and aerobic denitrification. These nitrogen-removing bacteria ensured high nitrogen removal efficiency of the bioreactor. The total nitrogen (TN) concentration in the bioreactor increased and then decreased, which did not continuously increase as occurred in conventional FOMBRs. The TN removal efficiency of the bioreactor was mostly above 40% and the highest reached 79%. Besides, the Bacillus-FOMBR suffered little membrane biofouling because of the quorum quenching effect of the Bacillus species. We speculate that the Bacillus-FOMBR has potential to treat high-salt wastewater and high strength ammonia-nitrogen wastewater.

A novel synthetic thin-film nanocomposite forward osmosis membrane modified by graphene oxide and polyethylene glycol for heavy metals removal from aqueous solutions

This study presents the synthesis of a novel thin-film nanocomposite forward osmosis (TFN-FO) membrane and its structural properties and performance; heavy metals removal behavior was further assessed in synthetic and industrial wastewater samples. The novel lab-fabricated TFN-FO membranes included a support layer (SL) constructed by the incorporation of different concentrations (0–8 wt%) of polyethylene glycol 400, polysulfone, and 1-methyl, 2-pyrrolidone via the phase inversion process and an active layer (AL) formed through incorporating different weight ratios (0–0.012 wt%) of graphene oxide (GO), 1, 3-Phenylenediamine and 1, 3, 5-benzene trichloride into the polyamide layer via the interfacial polymerization reaction. Compared with traditional TFC membranes, the TFN-FO membranes exhibited higher hydrophilicity, porosity, water permeability, water flux and salt rejection and lower reverse salt flux, specific reverse salt flux and internal concentration polarization (ICP). The water flux in the TFN membrane (34.3 LMH) increased by 174% and 129%, compared to the TFC membrane (12.5 LMH) and commercial FO membrane (15 LMH), respectively. The rejection rates of TFN FO membranes regarding Pb, Cd, and Cr were 99.9, 99.7 and 98.3%, respectively. The breakthrough time of heavy metals exceeded 14.5 h and 96% concerning flux recovery ratio. The modified FO membranes revealed excellent improvement in membrane structure, FO performances and separation properties.

Enzyme-aided forward osmosis (E-FO) process to enhance removal of micropollutants from water resources

Membrane filtration has proven its advantages in removing micropollutants from water. However, concentrated micropollutants in feed solutions still pose a high risk to environments and may contaminate the permeate. Here, a proof-of-concept of enzyme-aided forward osmosis (E-FO) process was demonstrated. In E-FO process, degradation and rejection of micropollutants occurred simultaneously, providing a detoxified feed solution and a cleaner permeate. A lab-made polyketone-based thin film composite membrane with high flux and high micropollutants rejection was explored as FO membrane. Laccase and 2, 4, 6-trichlorophenol (TCP) was employed as a model enzyme and micropollutant, respectively. Compared with a single enzyme catalysis, E-FO process showed a higher degradation efficiency owing to enzyme condensation during filtration. Compared with a single FO process including 0.051 mM TCP in feed solution, E-FO process adding 0.8 μM laccase showed 7.4 and 10.7 times lower TCP permeation and membrane adsorption when operated for 10 h. An enzyme-aided reverse osmosis (E-RO) process can produce clean water with similar quality as that of E-FO, however, suffers from membrane fouling. This work provides an insight in facile coupling of efficient enzyme catalysis with low fouling FO process for high quality water production from contaminated water resources.

The effects of naturally occurring operation factors on the removal mechanism of major algae metabolized materials in forward osmosis process

Abstract This research investigated the removal mechanism of algae metabolized materials (geosmin, 2-methylisoborneol (2-MIB), and microcystin-leucine arginine (MC-LR)) according to the naturally occurring operation factors such as temperature (10, 20 and 30 °C), transmembrane temperature (20 °C: 10 vs. 30, 30 vs. 10 °C) difference and valance of reverse salt flux (RSF) in forward osmosis membrane. Algae metabolized materials had high removal efficiency (94–99%) at all experimental conditions. According to the temperature difference, the absorption percentage of geosmin and 2-MIB on the FO membrane was 76, 75% and 75, 55%, respectively. However, adsorption percentage of toxin (MC-LR) materials were observed to be 11 and 85%, respectively. Temperature-dependent parameters such as water and solute viscosity & diffusivity, membrane intrinsic properties, have effects on the removal mechanism and rate. Consequently, the results from this research provide meaningful information on not only the removal of algae metabolized materials like micropollutants but also the water treatment process with consideration of the temperature conditions (temperature difference).

Understanding the organic micropollutants transport mechanisms in the fertilizer-drawn forward osmosis process

We systematically investigated the transport mechanisms of organic micropollutants (OMPs) in a fertilizer-drawn forward osmosis (FDFO) membrane process. Four representative OMPs, i.e., atenolol, atrazine, primidone, and caffeine, were chosen for their different molecular weights and structural characteristics. All the FDFO experiments were conducted with the membrane active layer on the feed solution (FS) side using three different fertilizer draw solutions (DS): potassium chloride (KCl), monoammonium phosphate (MAP), and diammonium phosphate (DAP) due to their different properties (i.e., osmotic pressure, diffusivity, viscosity and solution pH). Using KCl as the DS resulted in both the highest water flux and the highest reverse solute flux (RSF), while MAP and DAP resulted in similar water fluxes with varying RSF. The pH of the FS increased with DAP as the DS due to the reverse diffusion of NH4+ ions from the DS toward the FS, while for MAP and DAP DS, the pH of the FS was not impacted. The OMPs transport behavior (OMPs flux) was evaluated and compared with a simulated OMPs flux obtained via the pore-hindrance transport model to identify the effects of the OMPs structural properties. When MAP was used as DS, the OMPs flux was dominantly influenced by the physicochemical properties (i.e., hydrophobicity and surface charge). Those OMPs with positive charge and more hydrophobic, exhibited higher forward OMP fluxes. With DAP as the DS, the more hydrated FO membrane (caused by increased pH) as well as the enhanced RSF hindered OMPs transport through the FO membrane. With KCl as DS, the structural properties of the OMPs were dominant factors in the OMPs flux, however the higher RSF of the KCl draw solute may likely hamper the OMPs transport through the membrane especially those with higher MW (e.g., atenolol). The pore-hindrance model can be instrumental in understanding the effects of the hydrodynamic properties and the surface properties on the OMPs transport behaviors.

Cost-oriented optimization of osmotic dilution based on concentration-dependent hydraulic pressure

Osmotic dilution (OD) has been integrated with mainstream seawater reverse osmosis (SWRO) desalination technology to eliminate the worry about the draw solution regeneration and simultaneously lower the desalination cost. In this study, we further optimize the OD design with regard to mitigated water flux decline by introducing the concentration-dependent hydraulic pressure and developing one module-level techno-economic model. Analysis of the module-scale model firstly indicates that simply increasing the flowrate ratio of the feed solution stream to the draw solution stream is not economically applicable to mitigate the inherent water flux behavior in OD, potentially highlighting the significance of concentration-dependent hydraulic pressure. Accordingly, one-stage or multi-stage pressure-assisted forward osmosis (PAFO) followed by OD is evaluated its techno-economic advantage compared to the original OD process, respectively. Simulation results show that, for applied commercial FO membrane, OD combined with one-stage PAFO is the optimal design that balances the mitigated water flux decline with maximum saving and strongly depends on the permeate flow. But, future improved FO membranes necessitate the systematic exploration due to the fact that the optimal OD design is also affected by the membrane transport parameters. Therefore, this work can provide a protocol to optimize the OD design in seawater desalination.