Forward Osmosis Membrane Fouling Research Articles

An electrochemical impedance spectroscopy study on ion-fouling of forward osmosis membranes

Forward osmosis (FO) has been rapidly developed and employed in the industrial and environmental wastewater treatment, whose performance is affected profoundly by membrane fouling. Electrochemical impedance spectroscopy (EIS), as a nondestructive and low-cost evaluation technique, has been increasingly used for the characterization of membrane structures and membrane fouling. However, monitoring ion fouling of FO membranes is difficult with EIS due to the weak signal. In this work, the ion-fouling of various FO membranes was successfully characterized by EIS and the inductance variation was firstly utilized to interpret the degree of FO membrane fouling. Multi-walled carbon nanotubes (MWCNTs) and polydopamine (PDA) were modified onto the thin film nanofibrous composite membrane (#FO-0) as anti-fouling modification (#FO-MWCNTs and #FO-PDA), respectively. The structural measurements of #FO-0, #FO-MWCNTs, and #FO-PDA were achieved by a two-electrode EIS system. Then the ion fouling of FO membranes was monitored by a four-electrode EIS system. Through the equivalent circuit fitting, the correlation between the inductance variation and the membrane fouling was established. The FO experiments further validated the effectiveness of the proposed EIS method. The results indicate that inductance as a detection index is expected to be a convenient tool for studying the ion-fouling phenomenon in the FO process.

Determination of the critical draw solution concentration for anaerobic microfiltration osmotic membrane bioreactors

Anaerobic microfiltration osmotic membrane bioreactors (AnMF-OMBRs) have the advantages of resource recovery such as energy, water, and nutrients, but they have some drawbacks of low flux and severe membrane fouling. The concentration of draw solution (DS) is effective on the flux and fouling of FO membrane, and microbial inhibition. The aim of this study is to determine the critical DS concentration in AnMF-OMBR and up-flow anaerobic sludge blanket microfiltration osmotic membrane bioreactor (UASB MF-OMBR) systems operated with DS concentrations of 0.47, 1, and 1.5 M. The analytical hierarchical process (AHP) was applied to determine the critical DS concentration considering the criteria of forward osmosis (FO) performance, anaerobic performance, water recovery, microbial inhibition and operation time. The results demonstrated that the DS concentration of 0.47 M showed a better system performance, by causing less membrane fouling and microbial inhibition than that of the 1 and 1.5 M, and higher methane yield was obtained with 0.47 M in both bioreactors. The membrane autopsy analyses verified that the membrane fouling was severe with increasing DS concentration. Microbial community structure was affected by salinity build-up, high free ammonia (FA), and low organic loading rate (OLR). The relative abundance of Synergistota, a syntrophic acetate oxidizer, showed a parallel trend with Methanobacterium, a hydrogenotrophic methanogen in the conditions of high FA and salinity build-up due to the FO operation. Consequently, the critical DS concentration was determined as 0.47 M MgCl2.

Sodium hypochlorite-assisted osmotic backwashing for mitigating forward osmosis membrane fouling during pre-concentrating wastewater

Forward osmosis (FO) membrane has drawn substantial attention to pre-concentrating organic matter in wastewater for biogas production. However, membrane fouling control is an ongoing challenge for the feasibility of the FO system. Although chemical cleaning using a caustic solution (e.g., solution pH = 11) can remove organic foulants on the polyamide-based membranes, it can damage cellulose triacetate (CTA)-based FO membrane due to hydrolysis. This study assessed the efficacy of sodium hypochlorite (NaClO)-assisted osmotic backwashing to mitigate CTA-based FO membrane fouling during pre-concentrating primary wastewater effluent. The cleaning strategy employing a low concentration of NaClO achieved a higher restoration of water flux than conventional hydraulic flushing and sole osmotic backwashing. The water flux after NaClO-assisted osmotic backwashing (NaClO concentrations = 10–80 mg/L) reached 97–102%. Irreversible foulants on the membrane surface were fully removed by NaClO concentration from 20 to 80 mg/L. During four filtration cycles using a 40 mg-NaClO/L cleaning solution, the reverse salt flux increased from 4.3 to 6.3 g/m2h. This indicates that for a long-term operation, applying lower concentrations of NaClO (e.g., 20 mg/L) may be needed to avoid the changes in reverse salt flux. This study suggests that FO membranes during pre-concentrating primary wastewater effluent can be stably operated with NaClO-assisted osmotic backwashing.

Enhanced anti-fouling of forward osmosis membrane by pulsatile flow operation in textile wastewater treatment

Although osmotically driven membrane processes have exhibited great potential in a variety of applications, forward osmosis (FO) is still facing some critical challenges like membrane fouling, economics and design of draw solute. Current methods include pretreatment and membrane modification have proposed to solve fouling problem, however, these methods are still constrained by complex operational procedures and large use of chemicals. Herein, pulsatile flow, a simply-operated and chemical-free method, was employed to alleviate FO membrane fouling. Effects of pulse frequencies on membrane performance were investigated. Results showed that pulsation could effectively improve water flux and mitigate fouling. In particular, water flux of 5 Hz was 1.36 times higher than steady flow at 0 Hz, and no obvious fouling covered on membrane surface under 5 Hz. Computational Fluid Dynamics (CFD) simulation showed that the flow field on the membrane surface was evenly distributed by pulse, and cross-flow velocity changed regularly from 0.123 to 0.057 m/s in feed channel. Mechanism analysis illustrated effective transient shear stress, pulse induced membrane swing and reduced solute buildup were responsible to improve membrane flux and reduce membrane fouling. This work provides a reference for the further combination and application of pulsatile flow assisted FO to treat wastewater.

A novel fouling control strategy for forward osmosis membrane during sludge thickening via self-forming protective layer

Severe membrane fouling significantly limited forward osmosis (FO) process for sludge thickening (FST). Here, a novel antifouling strategy by loading a self-forming protective layer on FO membrane surface was proposed in this study. The protective layer was coated on FO membrane surface via a short-term FO process using activated sludge as the feed solution. Results indicated that the self-forming protective layer made FO membrane surface more negatively charged and more hydrophilic. As for the control FO (C-FO) membrane, the water flux decreased approximately 66% of the initial flux in Cycle 2 of FST process and thus resulting in the sludge concentration only increased to 40 g/L. In contrast, the flux decline rate of modified FO (M−FO) membrane was about 22%, and the corresponding sludge concentration still rose to 50 g/L. It suggested that the M−FO membrane with a protective layer had a better sludge thickening efficiency and a lower flux decline during sludge thickening compared to the C-FO membrane. Furthermore, less deposited foulants and better fouling reversibility were observed for M−FO membrane after two cycles of sludge thickening, implying that the protective layer effectively mitigated FO membrane fouling during sludge thickening. This phenomenon could be attributed to the excellent barrier effect of the protective layer and the enhanced surface hydrophilicity and negative charge, which improved the antifouling performance of the FO membrane. The findings of this study were conducive to better understanding of FO membrane fouling mechanisms and further development of fouling mitigation strategy via a protective layer.

Fouling evolution of extracellular polymeric substances in forward osmosis based microalgae dewatering

Membrane fouling was still a challenge for the potential application of forward osmosis (FO) in algae dewatering. In this study, the fouling behaviors of Chlorella vulgaris and Scenedesmus obliquus were compared in the FO membrane filtration process, and the roles of their soluble-extracellular polymeric substances (sEPS) and bound-EPS (bEPS) in fouling performance were investigated. The results showed that fouling behaviors could be divided into two stages including a quickly dropped and later a stable process. The bEPS of both species presented the highest flux decline (about 40.0%) by comparison with their sEPS, cells and broth. This performance was consistent with the largest dissolved organic carbon losses in feed solutions, and the highest interfacial free energy analyzed by the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory. The chemical characterizations of algal foulants further showed that the severe fouling performance was also consistent with a proper ratio of carbohydrates and proteins contents in the cake layer, as well as the higher low molecular weight (LMW) components. Compared with the bEPS, the sEPS was crucial for the membrane fouling of S. obliquus, and an evolution of the membrane fouling structure was found in both species at the later filtration stage. This work clearly revealed the fundamental mechanism of FO membrane fouling caused by real microalgal suspension, and it will improve our understanding of the evolutionary fouling performances of algal EPS.

Effect of ferrous-activated calcium peroxide oxidation on forward osmosis treatment of algae-laden water: Membrane fouling mitigation and mechanism

Forward osmosis (FO) is a high-efficiency and low-energy consumption way for algae-laden water treatment, whereas membrane fouling is still an unavoidable problem in its practical application. In this work, a strategy of ferrous-activated calcium peroxide (Fe(II)/CaO2) was proposed to control FO membrane fouling in the purification of algae-laden water. With the treatment of Fe(II)/CaO2, the aggregation of algal contaminants was promoted, the cell viability and integrity were well preserved, and the fluorescent organics were efficiently removed. With respect to the fouling of FO membrane, the flux decline was generally alleviated, and the flux recovery was promoted to varying degrees under different process conditions. It could be revealed through the extended Derjaguin-Landau-Verwey-Overbeek theory that the adhesion of contaminants and membrane surfaces was reduced by Fe(II)/CaO2 treatment. The interface morphologies and functional groups of membrane verified that Fe(II)/CaO2 could mitigate the fouling by reducing the amount of algal contaminants adhering to the FO membrane. The co-coagulation of in-situ Fe(III) together with Ca(OH)2, as well as the oxidation of •OH were the main mechanisms for fouling mitigation. In sum, the Fe(II)/CaO2 process could effectively improve the efficiency of FO for algae-laden water treatment, and has broad application prospects.

Synergistic effects of microplastics and organic foulants on the performance of forward osmosis membranes

Microplastics (MPs) are emerging contaminants that are abundantly present in the influent and effluent of wastewater treatment plants (WWTPs). Forward osmosis (FO) is an advanced treatment technology with potential applications in WWTPs. The presence of MPs in WWTP effluents can contribute to FO fouling and performance deterioration. This study focuses on FO membrane fouling by MPs of different sizes, and the interactional impacts of MPs and Humic acid (HA) (as the most common organic foulant in WWTPs) on FO membrane performance. The synergistic effect of combined MPs and HA fouling is shown to cause higher flux decline for FO membranes than that of HA or MPs alone. Reverse salt flux increased in the presence of MPs, and decreased when HA was present. Further, full flux recovery was obtained for all fouled membranes after hydraulic cleaning. This indicates the efficiency of FO systems for treating wastewater with high fouling potential. This study highlights the necessity of considering MPs in studying fouling behaviour, and for mitigation strategies of membranes used in WWT. The fundamentals created here can be further extended to other membrane-assisted separation processes.

Novel insights on fouling mechanism of forward osmosis membrane during deep thickening waste activated sludge

Application of forward osmosis (FO) membrane for sludge thickening (FO-MST process) has aroused growing interests owing to its high rejection, low footprint and low energy consumption. However, severe FO membrane fouling at an increasing sludge concentration condition remains a main obstacle for causing water flux decline and sludge thickening efficiency reduction. Here, fouling behaviors and mechanisms of FO membrane in the FO-MST process were comprehensively investigated by analyzing surface morphology, foulants composition, fouling layer structure and fouling reversibility of FO membrane at different sludge concentrations. Results indicated that the FO-MST process successfully achieved deeply thickening waste activated sludge from mixed liquor suspended solids (MLSS) concentration of approximately 5–50 g/L. And sludge concentration had a significant impact on FO membrane fouling in the FO-MST process. According to the tendency of sludge concentration in the FO-MST process, FO membrane fouling could be divided into three stages. At the first stage (i.e., MLSS concentration less than 15 g/L), only few sludge flocs and organic foulants deposited onto the FO membrane surface and inorganic scaling was the dominant fouling type. At the second stage (i.e., MLSS concentration ranged 15–30 g/L), the amount of foulants especially organic foulants and biofoulants significantly increased on the FO membrane surface and formed a loose fouling layer. In the first two stages, the flux decline was not significant. At the last stage (i.e., MLSS concentration ranged 30–50 g/L), more and more microorganisms and organic foulants deposited on the FO membrane surface. Meanwhile, the subsequent foulants kept compacting the former foulants that were already on the membrane surface, resulting in the formation of a dense fouling layer and a significant flux decline of FO membrane. Our finding is helpful for better understanding FO membrane fouling at an extreme sludge condition and for searching for some FO membrane fouling mitigations in the FO-MST process.

Research on Influencing Factors and Cleaning Effect of Forward Osmosis Membrane Fouling

Research on Influencing Factors and Cleaning Effect of Forward Osmosis Membrane Fouling

Molecular level insights into the dynamic evolution of forward osmosis fouling via thermodynamic modeling and quantum chemistry calculation: Effect of protein/polysaccharide ratios

While forward osmosis (FO) shows broad application prospects in wastewater reuse and desalination, it is still hindered by membrane fouling issues. From the perspective of molecular structure and energy, this work investigated the effects of protein (PN)/polysaccharide (PS) ratios of organic foulants on the dynamic evolution of membrane fouling in FO. Fouling tests showed two interesting membrane fouling phenomena: Ⅰ) when PN content increased from 0.2 to 0.8 g/L with fixed PS content of 0.2 g/L, membrane fouling decreased for filtration of the same volume of foulants; Ⅱ) with the increase of filtration volume, the membrane fouling caused by 1:1 PN/PS foulants increased almost linearly, while the membrane fouling caused by 4:1 PN/PS foulants increased significantly at first, and then rapidly reached a stable fouling state. Thermodynamic analyses and quantum chemical calculations revealed that the attractive interaction energy between 1:1 PN/PS foulants and membrane was 1.90 times greater than that for 4:1 PN/PS foulants, and the protein and polysaccharide molecules with a ratio of 1:1 were more likely to form a tight cross-linked structure. Furthermore, the reverse solute diffusion significantly reduced the electrostatic repulsion energy among the polymer chains for 4:1 PN/PS foulants, which induced the transformation of foulant morphology from gel to floc and reduced the adhesion energy to membrane surface by 61%. As a result, in the later fouling stage, few 4:1 PN/PS foulants were newly attached to the membrane, leading to a pseudo-stable flux. Based on the aforementioned findings, this study reveals a unified thermodynamic framework for the effects of the PN/PS ratios of organic foulants on the dynamic evolution of FO membrane fouling. The proposed mechanism is beneficial in formulating “tailored” fouling mitigation strategies and elucidating the appropriate application fields for FO technology.

Robust mitigation of FO membrane fouling by coagulation-floatation process: Role of microbubbles

Forward osmosis (FO) membrane fouling is a big obstacle in real textile wastewater treatment. Herein, a series of pretreatments include coagulation (C), microbubbles (Mbs) and their combination process (Mbs + C) were used to alleviate membrane fouling. Their different effects on flux and rejection rate of FO membrane were also investigated. Satisfactory removal efficiencies for UV254, dissolved organic carbon (DOC), chemical oxygen demand (COD) and antimony (Sb) of 48.27, 47.80, 40.70 and 41.87% were obtained at the optimum polyaluminum chloride (PAC) dosage of 300 mg L−1 and combined treatment time of 15 min. Compared with C alone, combined Mbs + C resulted in smaller flux decrease (~40%) and higher rejection rate (>98%) of FO membrane. This result confirmed the positive effect of Mbs on the combined processes. Fluorescence excitation-emission matrices coupled with parallel factor (EEM-PARAFAC), gel permeation chromatography (GPC) and gas chromatography mass spectrometry (GC–MS) measurements were further carried out to investigate the mitigation effect of pretreatments on membrane fouling. Results exhibited Mbs + C can significantly remove tryptophan-like substance and aliphatic alcohols due to enhanced coagulation-floatation property and oxidation of hydroxyl radicals. This study provides useful insights for fouling mitigation through Mbs and coagulation in actual FO process when dealing with textile wastewater.

Water reclamation and microbial community investigation: Treatment of tetramethylammonium hydroxide wastewater through an anaerobic osmotic membrane bioreactor hybrid system

Tetramethylammonium hydroxide (TMAH) is a toxic photoresist developer used in the photolithography process in thin-film transistor liquid crystal display (TFT-LCD) production, and it can be removed through anaerobic treatment. TMAH cannot be released into the environment because of its higher toxicity. A tight membrane, such as a forward osmosis (FO) membrane, together with an anaerobic biological process can ensure that no TMAH is released into the environment. Thus, for the first time, an anaerobic osmotic membrane bioreactor (AnOMBR) hybrid system was developed in this study to treat a low-strength TMAH wastewater and to simultaneously investigate its microbial community. Microfiltration extraction was used to mitigate the salinity accumulation, and a periodically physical water cleaning was utilized to mitigate the FO membrane fouling. The diluted draw solute (MgSO4) was reconcentrated and reused by a membrane distillation (MD) process in the AnOMBR to achieve 99.99% TMAH removal in this AnOMBR-MD hybrid system, thereby ensuring that no TMAH is released into the natural environment. Moreover, the membrane fouling in the feed and draw sides were analyzed through the fluorescence excitation-emission matrix (FEEM) spectrophotometry to confirm that the humic acid-like materials were the primary membrane fouling components in this AnOMBR. Additionally, 16S rRNA metagenomics analysis indicated that Methanosaeta was the predominant contributor to methanogenesis and proliferated during the long-term operation. The methane yield was increased from 0.2 to 0.26 L CH4/g COD when the methanogen species acclimatized to the saline system.

Preparation of electrically enhanced forward osmosis (FO) membrane by two-dimensional MXenes for organic fouling mitigation

In this work, a conductive thin film composite forward osmosis (TFC-FO) membrane was firstly prepared via vacuum filtering MXenes nanolayer on the outer surface of polyethersulfone membrane followed by interfacial polymerization in the other side. Moreover, its feasibility of mitigating organic fouling under electric field was evaluated. Results indicated that the addition of MXenes greatly reduced the electric resistance of membrane from 2.1 × 1012 Ω to 46.8 Ω, enhanced the membrane porosity and promoted the membrane performance in terms of the ratio of water flux to reverse salt flux. The modified TFC-FO membrane presented the optimal performance with 0.47 g/m2 loading amount of MXenes. Organic fouling experiments using sodium alginate (SA) and bovine serum albumin (BSA) as representative demonstrated that the introduction of MXenes could effectively enhance the anti-fouling ability of TFC-FO membrane under the electric field of 2 V. The interelectron repulsion hindered organic foulants attaching into membrane surface and thus effectively alleviated the membrane fouling. More importantly, the modified TFC-FO membrane showed good stability during the fouling experiment of 10 h. In all, our work proved that introducing MXenes into the porous layer of support is feasible to alleviate organic fouling of FO membrane.

Forward osmosis treatment of algal-rich water: Characteristics and mechanism of membrane fouling

Membrane fouling is an inevitable problem in forward osmosis (FO) treatment of algal-rich water (ARW). Natural ARW has a complex composition. Therefore, the coexisting components (Ca2+, natural organic humic acid [HA], and inorganic particulate kaolinite) in the influence of ARW on FO membrane fouling were studied. The analysis of extended Derjaguin–Landau–Verwey–Overbeek theory and the confocal laser scanning microscopy revealed that the addition of coexisting components increased the attraction between pollutants and membranes, as well as among pollutants to varying degrees, and promoted the development of membrane fouling. Furthermore, Ca2+ and HA aggravated irreversible membrane fouling. All coexisting components changed the distribution and thickness of the fouling layer, and the addition of Ca2+ increased the content of extracellular organic matter (proteins and polysaccharides). The present results enhance the understanding of the mechanism through which natural ingredients affect microalgal membrane fouling and provide a basis for membrane fouling control to treat ARW.

Real-time monitoring of forward osmosis membrane fouling in wastewater reuse process performed with a deep learning model

Monitoring fouling behavior for better understanding and control has recently gained increasing attention. However, there is no practical method for observing membrane fouling in real time, especially in the forward osmosis (FO) process. In this article, we used the optical coherence tomography (OCT) technique to conduct real-time monitoring of the membrane fouling layer in the FO process. Fouling tendency of the FO membrane was observed at four distinguished stages for 21 days using a regular membrane cleaning method. In this method, chemical cleaning, which extracts two to three times as much organic matter (OM) as physical cleaning, was used as an effective method. Real-time OCT image observations indicated that a thin, dense, and flat fouling layer was formed (initial stage). On the other hand, a fouling layer with a thick and rough surface was formed later (final stage). A deep learning convolutional neural network model was developed to predict membrane fouling characteristics based on a dataset of real-time fouling images. The model results show a very high correlation between the predicted data and the actual data. R2 equals 0.90, 0.86, 0.92, and 0.90 for the thickness, porosity, roughness, and density of the fouling layer, respectively. As a promising approach, real-time monitoring of fouling layers on the surface of FO membranes and the prediction of fouling layer characteristics using deep learning models can characterize and control membrane fouling in FO and other membrane processes.

UV/H2O2-assisted forward osmosis system for extended filtration, alleviated fouling, and low-strength landfill leachate concentrate

The forward osmosis (FO) membrane process is a good option for treating complex wastewater, such as landfill leachate, owing to its high rejection. However, organic membrane fouling and the generation of high-strength concentrate hamper efficient and environmentally friendly operation. To overcome these limitations, an integrated FO system combined with UV/H2O2 oxidation is proposed in this paper. Changes in the heterogeneous organic composition of the leachate were tracked along the treatment processes via size exclusion chromatography and excitation emission matrix combined with parallel factor analysis, which allowed us to pinpoint the organic fractions responsible for FO membrane fouling and evaluate their removal efficiency. Three fluorescent components, including tryptophan-like (C1), fulvic-like (C2), and humic-like (C3) components, were identified in the landfill leachate. A separate UV/H2O2 oxidation system led to selective removal of the organic leachate fractions, causing membrane fouling by ~80% along with the overall removal of bulk leachate by ~45%. Compared to traditional FO, the integrated system resulted in improved filtered volume (by 40%), decreased overall membrane resistance (by 30%), complete flux recovery after physical cleaning, and 50% reduction of organic carbon in the membrane concentrate. Moreover, the concentrate from the integrated FO system was characterized by a much lower abundance of large molecules, which is beneficial for the reclamation of concentrate due to its high biodegradability. This study demonstrated the effectiveness of UV/H2O2 oxidation as an integrated option for an FO system used for extended filtration, membrane fouling mitigation, and the production of low-strength landfill leachate concentrate.

Combined fouling of forward osmosis membrane by alginate and TiO2 nanoparticles and fouling mitigation mechanisms

Forward osmosis (FO) is a promising technology for water treatment, but its fouling mechanisms are poorly understood compared to other membrane-based processes. This study focuses on combined fouling caused by alginate (SA) and TiO2 nanoparticles, which serve as representative organic and inorganic foulants, respectively. The results show that the co-presence of TiO2 can effectively mitigate membrane fouling by SA under vas feed chemistries (Ca2+ concentrations). The negative charge of the SA foulants increased in the presence of TiO2, alleviating SA aggregation due to electrostatic and steric stabilization. The behavior and mechanisms of membrane fouling were characterized by attenuated total reflection-Fourier transformation infrared spectroscopy (ATR-FTIR) coupled with isothermal titration calorimetry (ITC) and atomic force microscopy (AFM) at the molecular level. Combined SA-TiO2 had a lower binding affinity to Ca2+ than single SA, which was spontaneously exothermic and dominated by electrostatic interaction to reduce membrane fouling. This study provides new insight into the mechanisms of nanoparticles-mediated organic fouling in the FO process. It also demonstrates that an integrated ATR-FTIR/ITC/AFM approach can provide useful information for understanding other complicated interactions between inorganic and organic foulants.

Understanding the interaction mechanism of algal cells and soluble algal products foulants in forward osmosis dewatering

Forward osmosis (FO) has increasingly been an energy saving technology in microalgae dewatering, whereas membrane fouling is still a major obstacle for FO application. To explore the fouling mechanism of algal cells and their organic matters during microalgal FO dewatering process, Chlorella vulgaris and Scenedesmus obliquus were adopted as algae species, and the algae-derived foulants including algae cells, soluble algal products (SAP) and algal broth were used as feed solutions. The water fluxes behaviors of algal foulants had been investigated, and the dissolved organic carbon (DOC), protein and carbohydrates proportions of the feed solutions were then characterized, followed by the scanning electronic microscopy (SEM) and the analysis of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory for the FO membrane foulants. The results indicated that algal broth resulted in the fastest flux decline due to the combined fouling between SAP and algae cells. The competitive adsorption phenomenon between cells and SAP was found in C. vulgaris broth but not in S. obliquus, resulting in a high protein content loss in the feed solution of C. vulgaris. The fouling potential of those individual and combined feed solutions could be well predicated using the XDLVO theory, and the higher the interfacial energy, the faster the flux decline was found for both adhesion and cohesion stages. The findings improve the understanding of FO membrane fouling mechanism by microalgae, indicating the selection of algae species for FO processes.

Performance Improvement and Biofouling Mitigation in Osmotic Microbial Fuel Cells via In Situ Formation of Silver Nanoparticles on Forward Osmosis Membrane.

An osmotic microbial fuel cell (OsMFC) using a forward osmosis (FO) membrane to replace the proton exchange membrane in a typical MFC achieves superior electricity production and better effluent water quality during municipal wastewater treatment. However, inevitable FO membrane fouling, especially biofouling, has a significantly adverse impact on water flux and thus hinders the stable operation of the OsMFC. Here, we proposed a method for biofouling mitigation of the FO membrane and further improvement in current generation of the OsMFC by applying a silver nanoparticle (AgNP) modified FO membrane. The characteristic tests revealed that the AgNP modified thin film composite (TFC) polyamide FO membrane showed advanced hydrophilicity, more negative zeta potential and better antibacterial property. The biofouling of the FO membrane in OsMFC was effectively alleviated by using the AgNP modified membrane. This phenomenon could be attributed to the changes of TFC–FO membrane properties and the antibacterial property of AgNPs on the membrane surface. An increased hydrophilicity and a more negative zeta potential of the modified membrane enhanced the repulsion between foulants and membrane surface. In addition, AgNPs directly disturbed the functions of microorganisms deposited on the membrane surface. Owing to the biofouling mitigation of the AgNP modified membrane, the water flux and electricity generation of OsMFC were correspondingly improved.