Ceramic Membrane Fouling Research Articles

Coupling Low-Frequency Ultrasound to a Crossflow Microfiltration Pilot: Effect of Ultrasonic Pulse Application on Sono-Microfiltration of Jackfruit Juice.

To reduce membrane fouling during the processing of highly pulpy fruit juices into clarified beverages, a crossflow Sono-Microfiltration (SMF) system was employed, strategically equipped with an ultrasonic probe for the direct application of low-frequency ultrasound (LFUS) to the juice just before the entrance to the ceramic membrane. Operating conditions were standardized, and the application of LFUS pulses in both corrective and preventive modes was investigated. The effect of SMF on the physicochemical properties and the total soluble phenol (TSP) content of the clarified juice was also evaluated. The distance of ultrasonic energy irradiation guided the selection of the LFUS probe. Amplitude conditions and ultrasonic pulses were more effective in the preventive mode and did not cause membrane damage, reducing the operation time of jackfruit juice by up to 50% and increasing permeability by up to 81%. The SMF did not alter the physicochemical parameters of the clarified juice, and the measured LFUS energy ranges did not affect the TSP concentration during the process. This study is the first to apply LFUS directly to the feed stream in a pilot-scale crossflow microfiltration system to reduce the fouling of ceramic membranes and maintain bioactive compounds in jackfruit juice.

Controlling of irreversible fouling and mechanism in a hybrid ceramic membrane bioreactor (CMBR)-reverse osmosis (RO) process for textile wastewater reclamation

In this study, the fouling propensity of a hybrid ceramic membrane bioreactor (CMBR)-reverse osmosis (RO) process was investigated over a prolonged period using real textile wastewater effluent. Additionally, the effectiveness of in-situ ozonation for fouling mitigation was investigated. The results revealed that the CMBR-RO system achieved approximately 99.8 % removal of chemical oxygen demand and 97.4 % removal of total nitrogen. Despite this, soluble extracellular polymeric substances, particularly biopolymers and humics-like substances, remained in the system, resulting in irreversible fouling on the ultrafiltration (UF) membrane. The implementation of in-situ ozonation notably reduced ceramic membrane fouling by enhancing the filterability of larger macromolecules and eliminating inorganic/organic foulants from the membrane surface. Multiple modified fouling indexes were also utilized to evaluate the fouling potential of the RO feed water through size fractionation. It is worth noting that ozonation could pose a potential risk for subsequent RO membrane fouling due to the formation of low molecular weight neutrals, acids, and calcium- or silica- related inorganic-organic complexes. Overall, the integrated CMBR-RO system with in-situ ozonation exhibited excellent performance in producing clean water, achieving nearly 100 % removal of 20 Aromatic Amines. These findings underscore the viability of the CMBR-RO system as a practical and sustainable choice for the reclamation of textile wastewater.

A DFT study of the adsorption of fouling molecules (metal sulfides and hydroxides) onto TiZrO4 ceramic membranes

Ceramic membrane fouling is a constraint in the treatment of acid mine drainage (AMD), leading to a decrease in efficiency over time. Here, it is described via first-principles calculations the physical and chemical phenomena occurring on the surface of TiZrO4 filtration membranes due to the adsorption of eight potential fouling compounds [CuS, FeS, Fe2S3, CaS, Al(OH)3, Fe(OH)3, Fe(OH)2, and Cu(OH)2]. The interaction of these fouling molecules was performed onto nanostructured TiZrO4 surfaces with several pores representing the filtration membranes employed in the treatment of AMD. The adsorption energies reveal that the adsorption is feasible with all the fouling molecules studied, and it is strongly related to the molecular polarity of the adsorbate. Consequently, the adsorption of metal sulfides is more feasible than hydroxides with adsorption orders of CaS>FeS>CuS>Fe2S3, and Al(OH)3>Fe-hydroxides>Cu(OH)2. The outcomes suggest that the metal sulfide adsorption depends on the adsorbate intrinsic polarity, solvent effects, adsorbate van der Waals radius, and membrane surface topology, while the adsorption of hydroxides is less influenced by the last two factors. Density-based binding and energy decomposition analyses indicate strong electrostatic attractions and covalent bonds at the adsorbate-membrane interface supporting the chemical fouling onto ceramic filtration membranes. According to our theoretical results and the elevated concentration of Cu and Fe in AMD, we propose that FeS and CuS are mainly responsible for the fouling onto TiZrO4 membrane surfaces. These results offer valuable information on the adsorption phenomena at TiZrO4 membrane surfaces, which can be useful for metallurgy, industrial water treatment, food industry, biotechnology, and pharmaceutical applications.

An innovative exploration to identify and isolate the dominant-flocculated-species from polytitanium chloride synthesized by electrodialysis

Abundance of dominant-flocculated-species is the key to determine coagulation performance of coagulant. Titanium-based coagulants have garnered considerable attention due to their high coagulation efficiency, but with a current challenge of the identification and isolation of the dominant-flocculated-species. Herein, polytitanium chloride (PTC), enriched with dominant-flocculated-species, was successfully synthesized by electrodialysis through accurate micro-interface control of the reaction among Ti-hydrolyzed-species and OH−. Special attention was paid to a feasible and high-effective strategy to isolate the dominant-flocculated-species from PTC through one-step rapid ultrafiltration. Selective preference was the ultrafiltration membranes (made of polyethersulfone) with a molecular weight cut-off of 5 kDa, which enabled the isolation of the dominant-flocculated-species, named PTC-5k. Results from the electrospray time-of-flight mass spectrometry (ESI-TOF-MS) proved a large proportion of the small and medium-sized hydrolyzed products as dominant-flocculated-species in PTC-5k, with the main signals concentrated between m/z 100 and 500. This composition achieved approximately 15.0% higher removal of organic matter with a 33.0% reduction in dosage compared to PTC. Unique snowflake-like branched structure of PTC-5k enhanced the coagulation mechanisms of sweeping and adsorption-bridging flocculation. Worth noting was the more compact flocs formed by PTC-5k than PTC, which was the probable reason for the mitigated fouling of ceramic membrane when PTC-5k was utilized as pre-treatment methodology. Continuous operation of ceramic membrane filtration up to 30 h, demonstrated 30% improvement in stable flux compared to PTC. This study provides the strategy for the isolation of Ti-dominant-flocculated-species, and lays the foundation for practical application.

High Recovery of Ceramic Membrane Cleaning Remediation by Ozone Nanobubble Technology.

The persistent issue of ceramic membrane fouling poses significant challenges to its widespread implementation. To address this concern, ozone nanobubbles (ozone-NBs) have garnered attention due to their remarkable mass transfer efficiency. In this investigation, we present a novel ozone-NB generator system to effectively clean a fouled ceramic membrane that is typically employed in the dye industry. The surface characteristics of the ceramic membrane underwent significant alterations, manifesting incremental changes in surface roughness and foulant accumulation reduction, as evidenced in atomic force microscopy, scanning electron microscopy, X-ray fluorescence, and energy-dispersive spectroscopy. Remarkably, the sequential 4 h cleaning process demonstrates an effective outcome leading to an almost 2-fold enhancement in the membrane flux. The initial fouled state of 608 L/h/m2 increased to 1050 L/h/m2 in the 4 h state with a recovery of 50%. We propose such membrane performance improvement governed by the ozone-NBs with a size distribution of 213.2 nm and a zeta potential value of -20.26 ± 0.13 mV, respectively. This effort showcases a substantial innovative and sustainable technology approach toward proficient foulant removal in water treatment applications.

Control behavior of pretreatment on ceramic membrane fouling caused by different organic substances

To guide the practical application of ozonation and adsorption coupled with ceramic membrane technology, the mitigation mechanisms of O3 pre-oxidation, powdered activated carbon (PAC) pre-adsorption, and combined O3-PAC pretreatment on membrane fouling caused by natural organic matter (NOM) were investigated. The membrane and water quality were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), three-dimensional fluorescence-parallel factor analysis (PARAFAC-EEM), dissolved organic carbon (DOC), laser particle size and Zeta potential. Results showed that the membrane flux decline caused by humic acid (HA), sodium alginate (SA), bovine serum albumin (BSA) and surface water were alleviated by 35.2%, 55.2%, 31.0% and 59.0% after O3-PAC pretreatment. Meanwhile the removal rates of HA, SA and BSA were 26.2, 74.8% and 42.3%, respectively. The combination of PAC and O3 can effectively control the membrane fouling caused by HA and SA. Ozonation can degrade organic matter into small molecules, and PAC has high adsorption to these small molecules, by recycling PAC can take away this part of organic matter, thereby reducing membrane fouling. O3 showed no obvious advantage for membrane fouling caused by BSA, and the decrease of membrane fouling was mainly attributed to the adsorption of PAC. This investigation highlights the potential mechanism of O3-PAC in alleviating the membrane fouling caused by different organic compounds, contributing to the efficient and low-carbon operation of the production.

Nanoparticles formed in Fe(II)/KMnO4-catalyzed ozonation to alleviate ceramic membrane fouling and improve membrane rejection performance of humic acid

Fe(II)/KMnO4 has been identified as a moderate oxidation system capable of producing ferromanganese nanoparticles (NPs). However, previous studies on the catalytic impact of these formed NPs on ozone was limited. This study delved into the catalytic effects of NPs on controlling membrane fouling induced by humic acid (HA). In-situ NPs (I-NPs), formed during Fe(II)/KMnO4 pretreatment for HA solutions, and ex-situ NPs (E-NPs), formed in DI water, combined with in-situ ozonation (5 mg O3/L), resulted in a decrease TMP/TMP0 from 2.32 to 1.85 and 1.20, respectively. Moreover, the membrane rejection performance of E-NPs/in-situ ozonation surpassed that of I-NPs/in-situ ozonation. The dissolved organic carbon (DOC) rejection ratio of 64.6% could be achieved at E-NPs [90 μM KMnO4/270 μM Fe(II)]/5 mg O3/L. Component analysis revealed that both I-NPs and E-NPs comprised FexOy, MnO2 and FeOOH. Nevertheless, KMnO4 was consumed by HA, and a portion of Fe(II) transformed into non-catalytic flocs during I-NPs preparation. E-NPs could decompose ozone into reactive oxygen species (ROSs), including ·OH, ·O2− and 1O2, contributing to higher membrane flux and rejection. Besides, E-NPs proved suitable for continuous-flow filtration resulting in a lower level of assimilable organic carbon (AOC) in the effluent. Therefore, the catalytic potential of Fe(II)/KMnO4-formed NPs on ozone presents a promising potential for mitigating membrane fouling caused by HA.

Cleaning efficiency and mechanism of ozone micro-nano-bubbles on ceramic membrane fouling

Membrane separation technology using ceramic membrane as carrier has attracted wide attention in drinking water treatment. However, the inevitable problem of irreversible contamination requires high intensity chemical cleaning in place (CIP) to ensure efficient ultrafiltration performance. Therefore, this study discussed the causes of membrane pollution, and further evaluated the purification effects of sodium hypochlorite, different aeration methods and different dosage of ozone as cleaning agents on membrane pollution. Comparison of the physicochemical properties and surface morphology of ceramic membranes before and after cleaning showed that ozone micro-nano-bubbles (O3-MNBs) had excellent cleaning efficiency at the same dosage. MNBs could provide shear forces, while their high mass transfer efficiency increased the dissolved ozone concentration rapidly. The degradation of fouling on the membrane surface was achieved by direct ozone oxidation and indirect oxidation by the generation of OH, resulting in a 100% flux recovery rate in a short time. Our results suggest that O3-MNBs, as a promising CIP method for ceramic membranes, not only significantly improves cleaning efficiency, but also reduces the negative environmental impact of chemical agents.

A robust superhydrophobic-superoleophilic PDMS/Al2O3/CM composite ceramic membrane: Stability, efficient emulsified oil/water separation, and anti-pollution performance

To address the issue of membrane fouling and low separation efficiency of ceramic membrane (CM) commonly encountered in oil/water separation, the implementation of a robust superhydrophobic coating on the surface of CM represents a viable and efficacious strategy. This study presented a facile approach for the fabrication of a durable superhydrophobic-superoleophilic composite coating on the surface of CM by the in-situ growth of needle-shaped alumina (Al2O3) followed by the impregnation of a polydimethylsiloxane (PDMS) coating. Various characterization techniques, such as FESEM, XPS, CLSM, bubble point porometer, contact angle etc. were used to characterize the microstructure, surface composition, pore size distribution, and surface characteristics of the PDMS/Al2O3/CM. The mechanical, chemical, and thermal stability were evaluated by means of sandpaper abrasion, tape peeling, immersion tests including organic solvent, acid, and base solutions, and heat treatment. The separation performance, anti-pollution property, and reusability of the modified CM were evaluated by oil/water mixture and water-in-oil emulsion. And the oil/water separation model and anti-fouling mechanism was also elaborated. The results indicated that a homogeneous needle Al2O3 cluster with a micro/nano dual-scale hierarchical roughness was grown on the surface of the CM, and the further introduction of PDMS gave the modified CM excellent superhydrophobicity with a water contact angle (WCA) of ∼160° and a water rolling angle (WOA) of 7.6°. The PDMS/Al2O3/CM composite membrane exhibited remarkable capability in segregating oil/water mixtures, including emulsified water-in-oil. The separation efficiency remained above 99 %, even after 15 cycles of separation. This study presents a simple technique for fabricating a robust superhydrophobic coating onto the Al2O3-based CM surface, which exhibits the potential for application to other ceramic membrane substrates. And the anticipated outcome of this developing is a broad spectrum of industrial applications for emulsified oil/water purification.

Ceramic membrane fouling mechanisms and control for water treatment

Ceramic membrane fouling mechanisms and control for water treatment

Visible light photocatalysis alleviates ceramic membrane fouling caused by intracellular organic matter of Microcystis aeruginosa

Ultrafiltration (UF) is an effective technology for treating algae-containing water. The algal intracellular organic matter (IOM) released by dead algae during an excessive algae growth phase causes more serious membrane fouling than viable algal cells and algal extracellular organic matter (EOM), which seriously restricts stable operation of UF. This paper studied the removal of IOM by a Bi2O3–TiO2/PAC (Bi-doped TiO2 nano-composites supported by powdered activated carbon) photocatalytic oxidation-ceramic ultrafiltration membrane, the inhibitory effect of membrane fouling at different photocatalytic oxidation times, and the fouling mechanism. The results show that both the adsorption and photocatalytic oxidation of Bi2O3–TiO2/PAC can significantly remove proteinoids and humic acid-like fluorescent components present in IOM, with removals of UV254 and DOC reaching up to 81.8% and 44.0%. The generated superoxide radicals and hydroxyl radicals positively affect the degradation of organic compounds of various molecular weights, and holes mainly degrade acidic low-molecular weight organic compounds. When the photocatalytic oxidation time was extended to 60 min, the membrane flux increased by 70.7% and the reversible resistance and irreversible resistance decreased by 83.4% and 90.1%, respectively. Under these conditions, the fouling mechanism changed from complete blockage to intermediate blockage. In the late stage of photocatalytic oxidation (90–120min), part of the high and medium molecular weight organic components were oxidized to produce low-molecular weight organic compounds (LMW acidic and neutral organic compounds), and blockage of filter cake became the main fouling mechanism. After photocatalysis, the zeta potential decreases significantly and the interaction forces between pollutants and pollutants are transformed into repulsive forces. Application of an appropriate photocatalytic oxidation time can alleviate the ultrafiltration membrane fouling caused by algal-derived organics.

Effect of Membrane Pore Size on Membrane Fouling of Corundum Ceramic Membrane in MBR.

Ceramic membrane has emerged as a promising material to address the membrane fouling issue in membrane bioreactors (MBR). In order to optimize the structural property of ceramic membrane, four corundum ceramic membranes with the mean pore size of 0.50, 0.63, 0.80, and 1.02 μm were prepared, which were designated as C5, C7, C13, and C20, respectively. Long-term MBR experiments showed that the C7 membrane with medium pore size experienced the lowest trans-membrane pressure development rate. Both the decrease and increase of membrane pore size would lead to more severe membrane fouling in the MBR. It was also interesting that with the increase of membrane pore size, the relative proportion of cake layer resistance in total fouling resistance was gradually increased. The content of dissolved organic foulants (i.e., protein, polysaccharide and DOC) on the surface of C7 was quantified as the lowest among the different ceramic membranes. Microbial community analysis also revealed the C7 had a lower relative abundance of membrane fouling associated bacteria in its cake layer. The results clearly demonstrated that ceramic membrane fouling in MBR could be effectively alleviated through optimizing the membrane pore size, which was a key structural factor for preparation of ceramic membrane.

Contribution of proteins to ceramic membrane fouling at the early stage of membrane filtration

Membrane-based filtration is widely applied for water and wastewater treatment, while membrane fouling caused by contaminants such as proteins is an inevitable problem. Protein-containing mixtures or intact model proteins (e.g., bovine serum albumin, BSA) have been conventionally adopted and recognized as important membrane foulants. However, due to the complex composition of the protein-containing mixture or the inappropriate concentrations of model substances adopted, the real contribution of protein-like fractions toward ceramic membrane fouling remains unknown yet. In this work, the fouling behaviors of BSA and tryptones, representing the intact protein and the mixture of peptides, respectively, in a ceramic membrane microfiltration system were investigated. Both of them exhibited a negligible flux decrease and membrane fouling. For comparison, the fouling behaviors of the environmental protein-like substances (EP) extracted from different sludge sources were also examined. In addition, the experimental and simulation results demonstrate that all the EP samples were easier to aggregate and be adsorbed on the membrane surface than the two model proteins because the environmental protein-like substances had more unsaturated groups. However, those properties were insufficient to cause rapid membrane pore blockage or biocake formation compared with the previous studies. Both the model and actual protein fractions led to light membrane fouling, implying that proteins were not mainly responsible for membrane fouling at the early stage of ceramic membrane microfiltration.

Experimental Study on the Recovery of Lignin from Black Liquor by Blade Dynamic Cross-Flow Filtration Device

The separation and recovery of lignin in black liquor is a hot topic in current research. Ceramic membrane technology has become the main method of lignin separation in black liquor due to its advantages of green environmental protection, high efficiency and high recovery rate. However, in the separation process, the problem of ceramic membrane fouling has always existed and has become the key to hinder its continuous separation. Aiming at the problem that the existing filtration methods can not meet the continuous separation of lignin in black liquor, this paper proposes to apply the blade dynamic cross-flow filtration device to the separation process of lignin in black liquor, and the influence of blade rotation speed on the separation performance is studied experimentally. The results showed that increasing the rotating speed of the blade could effectively reduce the accumulation of filter cake on the membrane surface and achieve the purpose of improving the filtration flux.

Attribution of photocatalysis of fluorescent natural organic matter fractions to the alleviation of ceramic membrane ultrafiltration fouling

In this study, a novel composite functioned as adsorption-photocatalysis based on bismuth oxide (Bi2O3), reduced graphene oxide and titanium dioxide (TiO2) (labelled as BRGT) was applied in combination with ceramic membrane ultrafiltration to removal natural organic matter (NOM) and to mitigate membrane fouling. The mechanisms of NOM removal and of membrane fouling were investigated. The dual action of adsorption and photocatalysis by the BRGT effectively degraded NOM, giving a removal efficiency of 22.2 % for dissolved organic carbon and 73.0 % for UV absorbance at 254 nm. ·O2− radicals were mainly involved in the degradation of humic and protein/polyphenol-containing fluorescent components of NOM. BGRT had a high adsorption affinity for protein-like components, whose removal depended more on h+. The fouling behavior of the ceramic membrane was the result of pore blocking combined with cake filtration formation. BRGT mainly adsorbed hydrophobic components, which exacerbated the reversible fouling resistance and transformed the fouling mechanism from standard blocking into complete blocking. With increase of photocatalytic time, the hydrophobic fraction was converted into hydrophilic and transphilic fractions, and large and medium molecular weight organics were degraded into small molecules. In this case, the cake filtration formation occurred much earlier, with reversible membrane resistance reduced by 95.5 % and irreversible membrane resistance reduced by 90.4 % at 60 min. From the results we concluded that NOM can be effectively treated with adsorption-photocatalysis by BRGT, especially its fluorescent fractions, which has great potential in alleviating ceramic ultrafiltration membrane fouling.

Alleviated membrane fouling of corundum ceramic membrane in MBR: As compared with alumina membrane

In this study, a novel ceramic membrane was prepared with white corundum powders (CM), and its fouling behavior was evaluated in comparison with an alumina membrane (AM). Although the two membranes possessed almost the same pore size and porosity, the pure water permeability of CM was substantially lower than that of AM, possible due to the irregular pore structure of CM membrane. However, when employed in MBR, the CM exhibited much better antifouling performance with significantly decreased TMP development rate. Dissolved organic foulants (i.e. polysaccharides, proteins and DOC) extracted from the membrane surface of CM was shown to be much lower than that from AM. XDLVO analysis also demonstrated the repulsion force between sludge and CM membrane was stronger. More interestingly, largely different microorganism population was observed to form on the two membranes, which might contribute to the alleviation of CM membrane fouling in MBR. This work provides an easy but effective strategy for improving the antifouling ability of ceramic membrane in MBR.

Optimal intermittent ultrasound-assisted ultrafiltration for membrane fouling remediation

One of the most critical issues encountered in membrane-based separation processes is the permeate flux decline over a long period of operation. This study considered the potential advantages of applying intermittent ultrasound (US) to the ultrafiltration (UF) processes to control long term membrane fouling. The particles in the feed solution tend to attach to the membrane's internal pores and accumulate on the membrane surface, which impedes the filtration process and limits separation efficiency and significantly increases the power consumption. US-generated microbubbles create local turbulence and shear effect near the membrane surface, which disrupt the concentration polarization and fouling layer, resulting in flux improvement. In this regard, remediation of ceramic membrane fouling by an in-line intermittent US system was investigated. Bubble generation under different frequencies (20 kHz, 28 kHz, and 40 kHz), power intensities (50 W, 60 W, and 100 W) and time intervals were evaluated to determine the optimal US condition for enhanced filtration. A real time in-situ imaging of US-generated bubbles was employed, using a synchrotron propagation-based imaging (PBI) at the Canadian Light Source (CLS). A novel non-invasive method was employed to improve the contrast between the liquid and gas inside the bubble (interface of liquid and gas) facilitating the qualitative and quantitative analysis of US-generated bubbles. In addition, a piezoelectric ultrasonic transducer was integrated into a UF unit that was used to filter a 0.5 wt% latex paint solution. The microbubble dynamics at different US conditions were analyzed in order to correlate it with latex particles’ detachment, cake formation control and flux enhancement from data obtained with filtration experiments. It was found that the flux enhancement at 20 kHz and 28 kHz were significant, while the flux enhancement at 100 kHz was not noticeable. It was also observed that the amount of deposited particles on the membrane decreased when the frequency was increased. Oscillation of large bubbles leads to liquid movement around the bubbles and reduces the probability of the particle-membrane attachment. Our results showed that the bubble velocity increased as the frequency was increased from 20 kHz to 40 kHz. In addition, more bubbles were created when the US irradiation was turned on; however, the bubbles did not disappear when the US was off, which represent the long lifetime of the bubbles. The optimal flux was achieved when the ultrasound was set at a frequency of 28 kHz and power intensity of 50 W, while the interval of intermittent ultrasound was set at 60 s.

Study on pickling technology to control fouling of ceramic membrane treating secondary treated effluent.

The application of membrane technology in the field of water treatment was increasingly widespread, but membrane fouling still restricted its development, and the membrane needed to be chemically cleaned. This research focused on the high-efficiency pickling technology of ceramic membrane, and developed the cleaning technology of ceramic membrane in cooperation with surfactant. In the experiment, the municipal secondary effluent was used as the raw water, and the single-step, mixed and step-by-step cleaning effects of three strong acids, three weak acids and surfactants on ceramic membranes and polyvinylidene difluoride (PVDF) membranes were investigated. For ceramic membrane, the optimal cleaning combination was H2SO4 first and then DTAC, and the flux recovery rate could reach 96.94%; for PVDF membrane, the optimal cleaning combination was HNO3 first and then H2SO4, and the flux recovery rate could reach 93.72%. In addition, the surface of initial, polluted, and cleaned membranes were analyzed by scanning electron microscope and contact angle, and the fouling mechanism of the ceramic membrane was analyzed. The results showed that through physical cleaning and chemical cleaning, most of the pollutants on the membrane surface and pores were removed. The cleaning method can effectively control the membrane pollution.

Experimental Investigation of the Novel Periodic Feed Pressure Technique in Minimizing Fouling during the Filtration of Oily Water Systems Using Ceramic Membranes.

Fouling represents a bottleneck problem for promoting the use of membranes in filtration and separation applications. It becomes even more persistent when it comes to the filtration of fluid emulsions. In this case, a gel-like layer that combines droplets, impurities, salts, and other materials form at the membrane’s surface, blocking its pores. It is, therefore, a privilege to combat fouling by minimizing the accumulation of these droplets that work as seeds for other incoming droplets to cluster and coalesce with. In this work, we explore the use of the newly developed and novel periodic feed pressure technique (PFPT) in combating the fouling of ceramic membranes upon the filtration of oily water systems. The PFPT is based on alternating the applied transmembrane pressure (TMP) between the operating one and zero. A PFPT cycle is composed of a filtration half-cycle and a cleaning half-cycle. Permeation occurs when the TMP is set at its working value, while the cleaning occurs when it is zero. Three PFPT patterns were examined over two feeds of oily water systems with oil contents of 100 and 200 ppm, respectively. The results show that the PFPT is very effective in minimizing the problem of fouling compared to a non-PFPT normal filtration. Furthermore, the overall drops in permeate flux during the cleaning half-cycles are compensated by appreciable enhancement due to the significant elimination of fouling development such that the overall production of filtered water is even increased. Inspection of the internal surface of the membrane post rinsing at the end of the experiment proves that all PFPT cycles maintained the ceramic membranes as clean after a 2-h operation. This can ensure a prolonged lifespan of the ceramic membrane use and a continuous greater permeate volume production. The advantage of the PFPT is that it can be implemented on existing units with minimal modification, ease of operation, and saving energy.

Electrochemical impedance spectroscopy (EIS) reveals the role of microbial fuel cell-ceramic membrane bioreactor (MFC-CMBR): Electricity utilization and membrane fouling

Ceramic membrane has become a major concern due to creasing cost and competitive efficiency. Microbial fuel cell-ceramic membrane bioreactor (MFC-CMBR) is considered alternative technology for larger-scale industrial application because of its advantages of convenient detecting and control of membrane fouling. However, MFC-CMBR are highly susceptible to membrane fouling and harsh operating requirements in these wastewaters of different compositions. This research critically discusses that electrochemical response in different types of MFC-CMBRs and control of electricity utilization on ceramic membrane fouling. The experimental results indicated that the application of sludge acclimated in coupling system with higher external resistance could ensure that lower costs (electricity utilization and membrane cleaning) provided enough membrane fouling control. The improved performance of MFC-CMBR-1 could be attributed to its enhanced nitrification/denitrification activity and capacity of electrons migration between electrode and sludge mixture. The coupling system alleviated membrane fouling and impedance increasing by improving the characteristics of sludge (increased particle size, decreased adsorption adhesion free energy), EPS (decreased hydrophobicity, molecular weight distribution regulation). And filtration tests showed that roughness and contact angle for the MFC-CMBR tend for better development compared to CMBR, dependent on the changes in the chemical surface groups as a result of electric distribution ratio. In addition, correlation analysis and filtration experiments showed that the extracellular polymer substances (EPS) enhanced the charge transfer resistance (Rct), and the protein substance in EPS was the main fouling substance when external resistance was close to the internal resistance of MFC. In summary, the low internal resistance of ceramic membrane lead to obvious better fouling control and electricity utilization than organic membrane, and the paper provides insight into the MFC-CMBR systems for a wide range of detecting membrane fouling and applications of membrane fouling mitigation.