Search Results (27)

The growing problem of antibiotic resistance poses a serious threat to public health and ecosystems. New disinfection methods could help address this global issue. In this study, ultraviolet-C light-emitting diodes (UV-C LEDs) were used to inactivate Escherichia coli isolates resistant to antibiotics. These isolates were obtained from various real water sources, including seawater, surface water, and treated wastewater. Inactivation assays were performed using two wavelengths (255 nm and 265 nm), applying UV fluences ranging from 1 to 7 mJ/cm² to a phosphate-buffered saline solution inoculated with a mixture of 10 E. coli strains. Using an UV fluence of 2 mJ/cm², a log reduction of about 5 was achieved with both UV-C wavelengths tested. SEM imaging revealed no observable alterations in cell morphology after UV-C exposure. Pyrimidine dimer formation was quantified, yielding approximately 40 ng/mL of cyclobutane pyrimidine dimers after 2 mJ/cm² of exposure to both wavelengths. Additionally, water treatment was tested using ceramic silicon carbide membranes. High average rejection efficiencies (99.9%) were obtained for both total coliforms and E. coli using uncut flat sheet membranes. The combination with UV-C LEDs led to treatment of the concentrated membrane retentate (99.985% or higher), highlighting the potential of this treatment approach for effective water disinfection. Full article

In this work, a carrier-free photoacoustic spectroscopy system is developed for the detection of trace acetylene gas in insulating oil. The photoacoustic cell was integrated with an oil–gas separator, allowing dissolved gases in oil to be introduced into the cell through free diffusion. The oil–gas separator is a custom-fabricated AF2400-coated ceramic membrane, and its spin-coating process was carefully designed to enable rapid oil–gas separation and achieve high film flatness. Using a resonant photoacoustic cell and a low-noise lock-in amplifier, the sensitivity of the system was improved to 6.90 mV/ppm, with a repeatability error less than 1.65%. Calibration experiments demonstrated that continuous detection of dissolved gas in oil could be achieved, with a response time T₉₀ of less than 72.5 min. Compared to traditional photoacoustic spectroscopy, the continuous measurement capability of this method is expected to enable earlier fault diagnosis, thus having greater potential in industrial fields. Full article

Microplastics, pervasive environmental pollutants with significant health risks, present formidable challenges in wastewater treatment due to their persistence and resistance to conventional removal methods. This study investigates the efficacy of hybrid ceramic membrane filtration for the systematic removal of micro- and nanoplastics from wastewater, while evaluating the role of anaerobic digestion as a pretreatment to enhance membrane performance. This study systematically assesses the performance of the 1.4 μm pore-sized flat sheet ceramic membrane and the 1 kDa pore-sized tubular ceramic membrane, respectively, for microplastic and nanoplastic removal in wastewater. Also, the effect of anaerobic digestion was assessed in microplastic separation and quantification. Anaerobic digestion reduced suspended solids by 57–67%. The average microplastic concentration was ~1782 MP L⁻¹. However, anaerobic digestion reduced the average concentration to ~913 MP L⁻¹. The opposite trend was observed in nanoplastic concentrations, which were ~4268 and ~10,066 NP L⁻¹, respectively, for the samples without and with anaerobic digestion. The ceramic membrane flux decreased from ~106.5 to ~25 L m⁻² h⁻¹ at a flow rate of 0.4 L min⁻¹ during the collection of 2 L of filtrate. However, anaerobic digestion improved the flux approximately 3 times. The tubular ceramic membrane flux was ~6.1 L m⁻² h⁻¹ at a flow rate of 2.0 L min⁻¹, which was reduced by 50% after the ceramic membrane treatment. By overcoming the limitations of conventional microplastic removal methods, such as the inefficiency of residual chemicals or byproducts, hybrid ceramic membrane filtration is a viable option for a scalable, efficient, and sustainable method in controlling microplastic and nanoplastic pollution. Full article

The application of ceramic membranes in hemodialysis modules remains underexplored, as prior investigations have primarily concentrated on flat-sheet samples or small-scale assessments. This study advances the field by fabricating Al₂O₃ hollow fiber membranes, integrating them into a lab-scale module, and systematically evaluating the influence of sintering temperature on their structural characteristics, hemocompatibility, and dialysis performance. Al₂O₃ hollow fiber membranes were prepared using a phase inversion method and then sintered at three different temperatures. All membranes exhibited superior protein adsorption behavior compared to conventional polymer-based membranes, which indicates higher biocompatibility. Furthermore, the amount of adsorbed protein decreased with increasing sintering temperature. This suggests that the amount of protein adsorption can be controlled by adjusting the heat treatment conditions. The lab-scale hemodialyzer integrated with a membrane sintered at 1200 °C achieved the fastest urea removal rate of approximately 90% in 2 h and reached a Kt/V value of 1.1 after 60 min, which is comparable to the performance of commercial polymer-based hemodialyzers. Full article

In the pursuit of developing advanced nanofiltration membranes with high permeation flux for organic solvents, a TiO₂ nanofilm was synthesized via a vapor–liquid interfacial reaction on a flat-sheet α-Al₂O₃ ceramic support. This process involves the reaction of glycerol, an organic precursor with a structure featuring 1,2-diol and 1,3-diol groups, with TiCl₄ vapor to form organometallic hybrid films. Subsequent calcination in air at 250 °C transforms these hybrid films into carbon-doped titanium oxide nanofilms. The unique structure of glycerol plays a crucial role in determining the properties of the resulting nanopores, which exhibit high solvent permeance and effective solute rejection. The synthesized carbon-doped TiO₂ nanofiltration membranes demonstrated impressive performance, achieving a pure methanol permeability as high as 90.9 L·m⁻²·h ⁻¹·bar⁻¹. Moreover, these membranes exhibited a rejection rate of 93.2% for Congo Red in a methanol solution, underscoring their efficacy in separating solutes from solvents. The rigidity of the nanopores within these nanofilms, when supported on ceramic materials, confers high chemical stability even in the presence of polar solvents. This robustness makes the carbon-doped TiO₂ nanofilms suitable for applications in the purification and recovery of organic solvents. Full article

One method of processing municipal waste biogas plant digestate is to separate it into solid and liquid fractions. Since the digestate can be a potential source of water, it must undergo the appropriate treatment. Pressurised membrane processes preceded by struvite precipitation can be particularly useful in this regard. Experiments were conducted to determine the effectiveness of treating the digestate liquid fraction from a municipal waste biogas plant using an integrated process that combines struvite precipitation with membrane filtration, employing flat ceramic membranes with different cut-off values. The results confirm that this integrated process is effective for digestate treatment. A significantly increased improvement in the final quality of the test solution and a reduction in membrane fouling intensity were observed compared to those of these processes conducted separately. It is noteworthy that the purest solution was obtained when struvite precipitation and filtration through a flat ceramic membrane with a cut-off of 1 kDa were combined. This approach enabled the precipitation of struvite, a valuable fertiliser; the protection of the membranes from fouling; and a high degree of organic compound removal. The recovered water from the digestate (after dilution or removal of excess salts) can be used in agriculture or horticulture. Full article

The extensive application of ceramic membranes in wastewater treatment draws increasing attention due to their ultra-long service life. A cost-effective treatment for high-strength swine wastewater is an urgent and current need that is a worldwide challenge. A pilot-scale sequencing batch flat-sheet ceramic membrane bioreactor (ScMBR) coupled with a short-cut biological nitrogen removal (SBNR) process was developed to treat high-strength swine wastewater. The ScMBR achieved stable and excellent removal of COD (95.3%), NH₄⁺-N (98.3%), and TN (92.7%), though temperature went down from 20 °C, to 15 °C, to 10 °C stepwise along three operational phases. The COD and NH₄⁺-N concentrations in the effluent met with the discharge standards (GB18596-2001). Microbial community diversity was high, and the genera Pseudomonas and Comamonas were dominant in denitritation, and Nitrosomonas was dominant in nitritation. Ceramic membrane modules of this pilot-scale reactor were separated into six layers (A, B, C, D, E, F) from top to bottom. The total filtration resistance of both the top and bottom membrane modules was relatively low, and the resistance of the middle ones was high. These results indicate that the spatial distribution of the membrane fouling degree was different, related to different aeration scour intensities demonstrated by computational fluid dynamics (CFD). The results prove that the membrane fouling mechanism can be attributed to the cake layer formation of the middle modules and pore blocking of the top and bottom modules, which mainly consist of protein and carbohydrates. Therefore, different cleaning measures should be adopted for membrane modules in different positions. In this study, the efficient treatment of swine wastewater shows that the ScMBR system could be applied to high-strength wastewater. Furthermore, the spatial distribution characteristics of membrane fouling contribute to cleaning strategy formulation for further full-scale MBR applications. Full article

In the last decade, the development of a new generation of membranes based on low-cost materials has been widely studied. These membranes demonstrate significantly higher performance than the conventional ceramic membranes currently used in membrane separation technology. This work is focused on the development of a low-cost flat UF ceramic membrane composed completely of sepiolite using a uniaxial pressing method with dimensions of 5.5 cm of diameter and 3 mm of thickness. The sintering temperatures used were from 650 to 800 °C. Several properties, such as morphology, porosity, permeability, mechanical strength, and chemical resistance, are investigated. The results show that the mean pore diameter is increased from 40 to 150 nm when the sintering temperature increases from 650 °C to 800 °C. At these temperatures, excellent mechanical strength of 18 MPa to 22 MPa and high chemical resistance were achieved. SEM results revealed a crack-free structure with a uniformly smooth surface. Permeability tests were conducted using dead-end filtration. The sepiolite membrane demonstrated an improvement in its water permeability from 18 to 41 L·m⁻²·h⁻¹·bar⁻¹ when the sintering temperature increased from 650 °C to 750 °C. The efficiency of the sepiolite membranes sintered at 650 °C and 700 °C were evaluated with the application of the removal of paracetamol (PCT) and indigo blue (IB) dye separately from two synthetic aqueous solutions representing the pharmaceutical and textile sectors. Excellent removal efficiency of almost 100% for both contaminants was observed at ambient temperature and a pressure of 3 bars. Membrane regeneration was achieved through simple rinsing with deionized water. According to this finding, the UF sepiolite membrane demonstrated reversible fouling, which is consistent with the fouling coefficient “FRR” value higher than 90%. Full article

Ceramic membranes prepared with flat sheet configuration using local materials, iron ore and bentonite, are reported in this investigation. The feedstocks used were fully characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and laser diffraction/light scattering. In order to optimize the preparation conditions, the effect of sintering temperature on the microstructure of ferric and clayey membranes was assessed. Results obtained with SEM, confirmed by optical microscopy, indicate that the optimized sintering temperature was in the vicinity of 900 °C. The properties of the fabricated membranes were characterized in terms of mass and thickness loss throughout a determined period of time. The experimental results present a negligible variation in the rate of mass change, which suggested the stability of the synthesized membranes. Both the ferric and clayey membranes exhibit a prevalence of mesopores in their pore distribution. These results suggest that these specific membranes could be employed as cost-effective and environmentally friendly materials. Furthermore, they hold promise for potential applications in gas treatment processes. Full article

Composite flat membranes were prepared using a dry uniaxial pressing process. The effect of the sintering temperature (850–950 °C) and smectite proportion (10–50 wt.%) on membrane properties, such as microstructure, mechanical strength, water permeability, and treatment performances, was explored. It was observed that increasing the sintering temperature and adding higher amounts of smectite increased the mechanical strength and shrinkage. Therefore, 850 °C was chosen as the optimum sintering temperature because the composite membranes had a very low shrinkage that did not exceed 5% with high mechanical strength, above 23 MPa. The study of smectite addition (10–50 wt.%) showed that the pore size and water permeability were significantly reduced from 0.98 to 0.75 µm and from 623 to 371 L·h⁻¹·m⁻²·bar⁻¹, respectively. Furthermore, the application of the used membranes in the treatment of indigo blue (IB) solutions exhibited an almost total turbidity removal. While the removal of color and COD decreased from 95% to 76%, respectively, they decreased from 95% to 52% when the amount of smectite increased. To verify the treated water’s low toxicity, a germination test was performed. It has been shown that the total germination of linseed grains irrigated by M_S10-Z90 membrane permeate was identical to that irrigated with distilled water. Finally, based on its promising properties, its excellent separation efficiency, and its low energy consumption, the M_S10-Z90 (10 wt.% smectite and 90 wt.% zeolite) sintered at 850 °C could be recommended for the treatment of colored industrial wastewater. Full article

Micropollutants (MPs) are widely occurring in surface water all over the world with extremely low concentrations, and their treatment requires high energy consumption and efficiency. In this study, a large-sized planar photocatalytic reactive ceramic membrane (PRCM) was prepared using the facile dip-coating method with nitrogen-doped TiO₂ (N-TiO₂-CM) for the purification of tetracycline hydrochloride (TC) as a model MP. The N-TiO₂ nanoparticles and the as-prepared N-TiO₂-CM were characterized by SEM/EDS, TEM, XPS, UV–Vis DRS, and FT-IR. A fixed bed reactor integrated N-TiO₂-CM, and visible LED light was fabricated for the new PRCM water treatment system for the removal of TC with a comprehensive consideration of the degradation rate and permeate flux. The SEM/EDS results indicated that the N-TiO₂ was uniformly and tightly loaded onto the flat CM, and the pure water flux could reach over 2000 L/(m² × h) under a trans-membrane pressure (TMP) of −92 kPa. The fixed bed PRCM water treatment system is extremely suited for MP purification, and the removal efficiency of TC was as high as 92% with 270 min even though its initial concentration was as low as 20 mg/L. The degradation rate and permeate flux of N-TiO₂-CM was 2.57 and 2.30 times as high as that of the CM, indicating its good self-cleaning characteristics. The quenching experiments illustrated that the reactive radicals involved in the PRCM process, •OH and •O₂⁻, were responsible for TC degradation. This research also provides a utilization proposal for a scale-up N-TiO₂-CM system for water and wastewater treatment. Full article

Multilayer ceramic membranes to be used for bacteria removal by filtration were prepared from ceramic materials. They consist of a macro-porous carrier, an intermediate layer and a thin separation layer at the top. Tubular and flat disc supports were prepared from silica sand and calcite (natural raw materials), using extrusion and uniaxial pressing methods, respectively. Making use of the slip casting technique, the silica sand intermediate layer and the zircon top-layer were deposited on the supports, in this order. The particle size and the sintering temperature for each layer were optimized to achieve a suitable pore size for the deposition of the next layer. Morphology, microstructures, pore characteristics, strength and permeability were also studied. Filtration tests were conducted to optimize the permeation performance of the membrane. Experimental results show that the total porosity and average pore size of the porous ceramic supports sintered at different temperatures within the range (1150–1300 °C), and lie in the ranges of 44–52% and 5–30 μm, respectively. For the ZrSiO₄ top-layer, after firing at 1190 °C, a typical average pore size of about 0.3 μm and a thickness of about 70 μm were measured, while water permeability is estimated to a value of 440 lh⁻¹m⁻²bar⁻¹. Finally, the optimized membranes were tested in the sterilization of a culture medium. Filtration results show the efficiency of the zircon-deposited membranes for bacteria removal; indeed, the growth medium was found to be free of all microorganisms. Full article

High-rate processes have been investigated for the recovery of organic matter from municipal wastewater. High-rate membrane bioreactors (HR-MBRs) may simultaneously achieve the increased recovery of carbon and high effluent quality, although control of membrane fouling is extremely difficult. To address the severe fouling in HR-MBRs, the combination of granular scouring and frequent chemically enhanced backwashing was examined. The use of robust flat-sheet ceramic membranes enabled the application of those cleaning strategies. Experiments were carried out at an existing wastewater treatment plant. To operate as a high-rate system, the bioreactor solid residence time and hydraulic residence time were set at 0.5 days and 1.6 h, respectively. Although a relatively high flux of 20 L m⁻² h⁻¹ was applied, the proposed HR-MBR exhibited a very low fouling rate of 1.3 kPa/day. The system could recover >70% of the carbon from raw wastewater, whereas the concentration of chemical oxygen demand in the effluent was lowered to <20 mg/L. The performance of the proposed HR-MBR observed in this study was clearly superior to those reported in previous related studies. Full article

A lab-scale ceramic membrane bioreactor (MBR) with active membrane-fouling control system was developed for the partial nitrification (PN) process. The in situ membrane cleaning method was applied to remove the contaminants on the surface of the membrane with no interruption of the wastewater treatment. The results showed that the device increased critical flux and reduced gel layer resistance (R_g) and internal resistance (R_i) of the flat-sheet ceramic membrane by inhibiting the formation of the cake layer. In long-term experiments, nitrite oxidizing bacteria (NOB) was successfully suppressed, and nitrite accumulation rate (NAR) was achieved at a high level, up to 90.09%; the effluent NO₂⁻-N/NH₄⁺-N was maintained in balance dynamically with an average ratio of ~1.30, which would be beneficial to the proliferation of Anammox bacteria and the following autotrophic nitrogen removal (ANR) process. Moreover, with the assistance of in situ cleaning, energy input from aeration was significantly reduced, while over aeration was avoided for more stable PN performance. Full article

In order to efficiently remove NOMs in natural surface water and alleviate membrane pollution at the same time, a flat microfiltration ceramic membrane (CM) was modified with MnFeO_X (Mn-Fe-CM), and a coagulation–precipitation–sand filtration pretreatment coupled with an in situ ozonation-ceramic membrane filtration system (Pretreatment/O₃/Mn-Fe-CM) was constructed for this study. The results show that the removal rates of dissolved organic carbon (DOC), specific ultraviolet absorption (SUVA) and NH₄⁺-N by the Pretreatment/O₃/Mn-Fe-CM system were 51.1%, 67.9% and 65.71%, respectively. Macromolecular organic compounds such as aromatic proteins and soluble microbial products (SMPs) were also effectively removed. The working time of the membrane was about twice that in the Pretreatment/CM system without the in situ ozone oxidation, which was measured by the change in transmembrane pressure, proving that membrane fouling was significantly reduced. Finally, based on the SEM, AFM and other characterization results, it was concluded that the main mitigation mechanisms of membrane fouling in the Pretreatment/O₃/Mn-Fe-CM system was as follows: (1) pretreatment could remove part of DOC and SUVA to reduce their subsequent entrapment on a membrane surface; (2) a certain amount of shear force generated by O₃ aeration can reduce the adhesion of pollutants; (3) the loaded MnFeO_X with a higher catalytic ability produced a smoother active layer on the surface of the ceramic membrane, which was conducive in reducing the contact among Mn-Fe-CM, O₃ and pollutants, thus increasing the proportion of reversible pollution and further reducing the adhesion of pollutants; (4) Mn-Fe-CM catalyzed O₃ to produce ·OH to degrade the pollutants adsorbed on the membrane surface into smaller molecular organic matter, which enabled them pass through the membrane pores, reducing their accumulation on the membrane surface. Full article