Extensive research in recent years has explored numerous new features in the forward osmosis membrane bioreactor (FOMBR) process. However, there is an aspect, which is revolutionary but not yet been ...investigated. In FOMBR, FO membrane shows high rejection for a wide range of soluble contaminants. As a result, hydraulic retention time (HRT) does not correctly reflect the nominal retention of these dissolved contaminants in the bioreactor. This decoupling of contaminants retention time (CRT, i.e. the nominal retention of the dissolved contaminants) from HRT endows FOMBR a potential in significantly reducing the HRT for wastewater treatment. In this work, we report our results in this unexplored treatment potential. Using real municipal wastewater as feed, both a hybrid microfiltration-forward osmosis membrane bioreactor (MF-FOMBR) and a newly developed hybrid biofilm-forward osmosis membrane bioreactor (BF-FOMBR) achieved high removal of organic matter and nitrogen under HRT of down to 2.0 h, with significantly enhanced phosphorus recovery capacities. In the BF-FOMBR, the used of fixed bed biofilm not only obviated the need of additional solid/liquid separation (e.g. MF) to extract the side-stream for salt accumulation control and phosphorus recovery, but effectively quarantined the biomass from the FO membrane. The absence of MF in the side-stream further allowed suspended growth to be continuously removed from the system, which produced a selection pressure for the predominance of attached growth. As a result, a significant reduction in FO membrane fouling (by 24.7–54.5%) was achieved in the BF-FOMBR due to substantially reduced bacteria deposition and colonization.
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•FO membrane decouples CRT from HRT; HRT can thus be significantly reduced.•Both BF-FOMBR and MF-FOMBR achieved high pollutant removal with HRT of 2 h.•Reduced HRT resulted in enhanced phosphorus recovery capacity in both systems.•The use of fixed-bed biofilm overcame the need for MF in side-stream extraction.•The use of biofilm also significantly lowered FO membrane fouling.
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•Long-term removal of 20 antibiotics was analyzed in an MF-FOMBR for real wastewater treatment.•FO rejection ranged over 71.0–100% largely depending on the antibiotics’ ...M.W.•Significant enrichment of antibiotics was observed in the bioreactor.•Most antibiotics are poorly biodegradable (<50%) except β-Lactams and macrolides.•A major proportion (>50%) of the enriched antibiotics ended up in the MF effluent.
A hybrid microfiltration forward osmosis membrane bioreactor (MF-FOMBR) was operated with raw municipal wastewater as feed. The fate and removal behaviors of 20 commonly used antibiotics were investigated. With the influent concentration of 4.1–716.9 ng/L (the most prevalent antibiotics were enrofloxacin, sulfamethazine and cefalexin, followed by amoxicillin, lomefloxacin and ampicillin), the system showed 58.9–100% overall removal of all the antibiotics. Almost all the antibiotics was rejected efficiently (86.1–100%) by the FO membrane, except for sulfonamides and trimethoprim (as low as 71.0%) due to their low molecular weights (M.W., 250.1–278.1 g/mol). However, relatively low biological removal (8.7–45.7%) was observed for most antibiotics, except for macrolides (70.6–90.1%) which was effectively removed via biosorption, and β-Lactams (up to 64.6%) which is readily biodegradable, resulting in their significant accumulation (up to 3.4 folds, with the maximum concentration of 1831.5, 1056.7 and 626.3 ng/L for sulfamethazine, enrofloxacin, and cefalexin, respectively) in the mixed liquor. Different antibiotics showed distinct affinities for sorption to the activated sludge. The solid/liquid partitioning of the antibiotics is governed by their hydrophobicity. All the antibiotics was detected in the draw solution (DS) (with average concentrations of 3.8–100.4 ng/L, and enrofloxacin, amoxicillin and sulfamethazine being the most predominant ones) except macrolides in certain cases, highlighting the need to improve their overall removal via the development and application of denser membranes or integration of necessary physio-chemical treatment. The side-stream MF unit acted as a major exit (>50.1% of total mass) for the poorly biodegradable and poorly adsorbed antibiotics to leave the system, preventing their further contamination of the DS. The enrichment of the antibiotics in the MF effluent would also facilitate their final elimination via subsequent advanced treatments.
In this study, fertilizer drawn forward osmosis (FDFO) process was applied for the treatment of shale gas wastewater. The forward osmosis (FO) experiments with simulated shale gas wastewater and real ...shale gas wastewater were carried out, respectively. The effects of reverse salt diffusion on the inorganic fouling to the membrane surface was systematically investigated. Two commercial FO membranes were selected and the optimized operating conditions were evaluated. It was found that calcium sulfate scaling can be alleviated by optimizing the operating parameters, including increasing flow rate and decreasing temperature. Furthermore, the Aquaporin FO membrane, which has lower reverse salt flux and less surface charge potential, exhibited lower fouling tendency. Under the optimal operating conditions, the effects of reverse salt diffusion on the barium sulfate scaling were also analyzed. The presence of calcium ions can alleviate barium sulfate scaling, while sodium chloride will aggravate the barium sulfate scaling. In addition, the scaling behavior of real shale gas wastewater was further explored. Inorganic scaling phenomenon seriously affected the FO membrane performance and lower pH had beneficial effect on recycling the real shale gas wastewater. The present study provided both theoretical fundamentals and industry applicable practices for implementing FO technology in the treatment and resource recovery of shale gas wastewater.
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•Fertilizer drawn forward osmosis (FDFO) process was implemented to treat shale gas wastewater.•AQP Forward osmosis (FO) membrane shows a lower tendency of inorganic scaling.•Less FO membrane scaling can be achieved by optimizing FO operating parameters.•Calcium ions can alleviate barium sulfate scaling, while sodium chloride will aggravate the barium sulfate scaling.
Forward osmosis (FO) offers the potential for sustainable wastewater reuse and enhance water resource sustainability and resiliency. However, low performance of FO membranes due to the high ...structural parameter and poor fouling resistance limits their widespread implementation. Structural parameter minimization of substrates and modulation of the surface structures of polyamide nanofilms are crucial to achieve enhanced FO performance. Herein, a novel thin-film nanocomposite (TFN) FO membrane supported with Mxene scaffolded alginate hydrogel interlayer is fabricated. It is found that the incorporation of the hydrophilic and high surface energy alginate hydrogel@Mxene interlayer sandwiched between polyamide nanofilms and microporous substrate minimizes the structural parameter by creating abundant tortuous paths leading to minimized internal concentration polarization. Meanwhile, the nanoconfinement effect induced by the interlayer enabled the formation of lumpy network of bubble wrap-like textured polyamide structures on the membranes. Subsequently, the resulting membranes exhibited enhanced water flux of up to 45.6 LMH in PRO mode using 1.0 M NaCl as the draw solution, while the lower surface roughness bestowed the membranes with the minimal fouling propensity which resulted in more than 80% of the water recovery. Additionally, the integration of the fertilizer-drawn forward osmosis process with sludge thickening successfully enabled the dilution of a 2 M KCl fertilizer solution by 2.4 times after 12 h operation, while simultaneously concentrating the sludge from the MLSS of 2000 mg L−1 to 5183 mg L−1. This work provides important insightful concepts to inspire the development of advanced TFN-FO membranes with good overall performance suitable for sustainable water reuse using osmotically driven membrane processes.
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•TFN FO membranes supported on alginate hydrogel@Mxene interlayer are fabricated.•The interconnected network structure of the interlayer lowers structural parameter and minimizes ICP.•The alginate hydrogel@Mxene-TFN FO membrane showed enhanced water flux (45.6 LMH) and good anti-fouling property.•The integration of sludge thickening with the FDFO process is competitive for sustainable water recovery.
Membrane fouling during forward osmosis (FO) seriously affects the service life of the membrane and increases the treatment cost. A facile strategy was developed to mitigate membrane surface fouling ...and simultaneously achieve high pollutants rejection. The amino group on ε-Polylysine (PL) reacted covalently with the active sites (acyl chloride and carboxyl group) on the polyamide (PA), thereby grafting the ε-PL onto the PA active layer of PAN/LiCl supported membrane. Effects of membrane orientation, concentration of draw solution (DS), and pH of feed solution (FS) on pollutants rejection were investigated. Results showed that rejection efficiencies of TOC, Ca, Mg, Sb, Cr, and aniline in wastewater by the 0.5 wt% PL-grafted PAN-1.5LiCl TFC-FO membrane (FO-0.5 PL) attained 93.3%, 96.7%, 99.3%, 98.3%, 99.9%, and 99.8%, respectively. The high rejection efficiencies were mainly attributed to the improvement of the surface hydrophilicity of the grafted membrane, the reduction of the roughness, and the improvement of membrane surface potential. The microbubble-assisted cleaning experiment showed that the flux recovery efficiency of the FO-0.5 PL membrane could reach 98.8%, which is 6% higher than that of the FO-P membrane. The PL-grafted FO membrane simultaneously improves the stability of permeation flux (15.2 L m−2 h−1) and fouling resistance performance of the membrane. This study revealed that the PL grafted method can improve the antifouling performance of the membrane and can be used as a feasible treatment method for printing and dyeing wastewater. The research results provided a new idea for facile preparation and application of FO membranes and had a certain reference value for the development of antifouling FO membrane.
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•A novel type of PL/PAN/LiCl antifouling FO membrane was prepared.•High hydrophilicity (WCA 38°) and IEP with a more positive pH (5.5) were obtained.•Permeability and antifouling properties of the PL-grafted membranes were improved.•High rejection performance for typical pollutants in printing and dyeing wastewater (>93.3%).•Microbubble-assisted cleaning increased the flux recovery rate to 96.6%.
Interests on lithium extraction from the Chinese salt-lake brines have regained momentum due to the growing demand of lithium for application in electric vehicles. Characterized by a high Mg2+/Li+ ...ratio (MLR), the Chinese salt-lake brine has troubled scientists and engineers for decades. Recent progress has shown significant advantages of membrane technologies. This review summarizes the membrane technologies utilized for lithium extraction, including membrane extraction (ME), nanofiltration (NF), lithium ion-sieve (LIS), electrodialysis (ED), and forward osmosis (FO). The fundamental concepts and separation mechanisms of ME and chemical exchange are introduced. Positive NF membranes, ion-selective ED membranes are discussed in detail in terms of materials design for high permselectivity. Maintaining the high selectivity and adsorption capacity are discussed for LIS membranes. Solutions to design single ion-selective separation membranes by hybrid of mobility and affinity are discussed for the urgent lithium extraction problem. Carbon neutral FO is proposed for the concentration of lithium-enriched brines with a focal on a low structure parameter substrate and a high rejection for highly saline brine. The fundamental and engineering strategies for lithium extraction from high MLR brine will be of strong interest for the harvesting of valuable metal resources from complicated brine.
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•Membrane technologies for lithium extraction from high Mg2+/Li+ salt-lake brine are reviewed.•Extraction lithium from salt-lake brine is an integrated process of separation and enrichment.•Equilibrium separation based on affinity is proposed as the highly efficient technology for ion separation and enrichment.•Carbon neutral forward osmosis is proposed for the concentration of lithium-enriched brine.•Hybrid membrane processes are required to transform lithium from brine to lithium chemicals.
Two-dimensional (2D) materials have been demonstrated as promising building blocks of designing high-performance membranes for molecular separation. Nevertheless, it is a big challenge to apply ...2D-material membranes for water desalination. Herein, we proposed a new type of surface-charged MXene (SC-MXene) membrane for water desalination, which was facilely fabricated by laminar stacking of MXene nanosheets and subsequent surface-coating with polyelectrolyte layer. The morphology, physicochemical structure and surface property of the MXene materials and resulted membranes were observed by XPS, SEM, water contact angle test, AFM, IR and XPS. These results demonstrated that coating polyelectrolyte (PEI) successfully tuned the surface charge and enhanced the hydrophilicity without scarifying the laminar structure of MXene membrane. By utilizing the effects of electrostatic interaction and size-sieving, the resulting surface-charged MXene (SC-MXene) membrane exhibited high salt rejection and water permeance during either nanofiltration or forward osmosis process, showing great potential for water desalination.
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•Surface-charged MXene membrane was fabricated via polyelectrolyte coating.•Polyelectrolyte coating tuned surface charge and enhanced hydrophilicity.•Membrane exhibited outstanding water desalination performance in NF or FO process.
Perfluorooctanoic acid (PFOA) is a persistent compound, raising considerable global apprehension due to its resistance to breakdown and detrimental impacts on human health and aquatic environments. ...Pressure-driven membrane technologies treating PFAS-contaminated water are expensive and prone to fouling. This study presented a parametric investigation of the effectiveness of cellulose triacetate membrane in the forward osmosis (FO) membrane for removing PFOA from an aqueous solution. The study examined the influence of membrane orientation modes, feed pH, draw solution composition and concentration, and PFOA concentration on the performance of FO. The experimental results demonstrated that PFOA rejection was 99 % with MgCl2 and slightly >98 % with NaCl draw solutions due to the mechanism of PFOA binding to the membrane surface through Mg2+ ions. This finding highlights the crucial role of the draw solution's composition in PFOA treatment. Laboratory results revealed that membrane rejection of PFOA was 99 % at neutral and acidic pH levels but decreased to 95 % in an alkaline solution at pH 9. The decrease in membrane rejection is attributed to the dissociation of the membrane's functional groups, consequently causing pore swelling. The results were confirmed by calculating the average pore radius of the CTA membrane, which increased from 27.94 nm at pH 5 to 30.70 nm at pH 9. Also, variations in the PFOA concentration from 5 to 100 mg/L did not significantly impact the membrane rejection, indicating the process's capability to handle a wide range of PFOA concentrations. When seawater was the draw solution, the FO membrane rejected 99 % of PFOA concentrations ranging from 5 mg/L to 100 mg/L. The CTA FO treating PFOA-contaminated wastewater from soil remediation achieved a 90 % recovery rate and water flux recovery of 96.5 % after cleaning with DI water at 40 °C, followed by osmotic backwash. The results suggest the potential of using abundant and cost-effective natural solutions in the FO process, all without evident membrane fouling.
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•A parametric study evaluated the feasibility of PFOA treatment using a CTA FO membrane.•Synthetic wastewater and actual wastewater from PFOA-contaminated soil were used as feed solutions.•PFOA rejection was higher at acidic than alkaline pH and MgCl2 than NaCl draw solution.•PFOA rejection remained at 99 % when the PFOA concentration increased from 5 to 100 mg/L.•96 % water flux recovered after membrane backwashing with 40 °C DI water using actual wastewater.
Recently, low-energy forward osmosis (FO) technology has been employed in the lithium concentration stage during the extraction of lithium from brine sources. The interlayer FO membrane is renowned ...for its exceptional structural characteristics; however, challenges remain in selecting suitable interlayer materials and exploring their control mechanisms on amine monomers. As interlayer materials, traditional 3D nanomaterials are prone to detachment, while traditional 2D materials without micropores can increase the transmission resistance of water molecules. This study introduces a novel FO membrane utilizing Zr-BTB nanosheets with 5.4 Å micropores as the interlayer material. Based on detection and simulation calculations, it was found that the increase in steric hindrance and interaction forces jointly slowed the diffusion of amine monomers in the presence of the Zr-BTB interlayer. This results in a thinner separation layer, facilitating water transport. The interlayer also plays crucial roles in preventing defective pore formation in the separation layer and assisting in intercepting salt ions. The Zr-BTB interlayer membrane exhibited a water flux of 29.14 L m−2 h−1 and a reverse salt flux of 0.16 g m−2 h−1, which are superior to those of many FO membranes reported in the field. The prepared membrane also has excellent performance in lithium concentration applications, and its separation mechanism was explored by MD simulations.
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•Zr-BTB nanosheets with micropores are arranged and stacked to form an interlayer.•The presence of an interlayer helps eliminate defective holes in the separation layer.•Spatial hindrance and interaction effects are the main factors that slow down the diffusion rate of MPD.•Zr-BTB interlayer membranes show promising applications in lithium concentration.
