Tubular Ceramic Microfiltration Membrane Research Articles

New low-cost tubular ceramic microfiltration membrane based on natural sand for tangential urban wastewater treatment

In wastewater treatment, the development of low-cost separation methods is of significant importance. Low-cost membranes based on natural materials have become a highly active research topic in recent years. Herein, using low-cost natural Moroccan sand, new ceramic supports have been developed and characterized using different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), along with scanning electron microscope (SEM). Plastic paste (average particle size ≤125 µm) was blended with organic additives and water, then the obtained paste was extruded into porous tubular supports. The support had a porosity of 43%, water permeability of 1928 L/h m2 bar, excellent chemical and mechanical properties and an average pore diameter in the range of 8–15 µm after firing at 950 °C/2 h. As per SEM analysis, the tubular supports had a smooth and crack-free surface. The slip casting process was used to create a microfiltration layer from the same natural sand powder (average particle size ≤63 µm) using a mixture of powder sand, water, and polyvinyl alcohol solution. The water permeability of the microfiltration membrane sintered at 950 °C/2 h was 1052 L/h m2 bar, the average pore size diameter was about 0.90 µm and 82% of pores had a diameter ≤1.00 µm. The obtained microfiltration membrane was tested for the treatment of urban wastewater. The membrane showed excellent separation performance in turbidity removal and chemical oxygen demand.

Indigenous bentonite based tubular ceramic microfiltration membrane: Elaboration, characterization, and evaluation of environmental impacts using life cycle techniques

This work fabricated a tubular ceramic microfiltration membrane from local bentonite clay and further characterized it to evaluate the membrane properties. The extrusion method followed by sintering was used to prepare the membrane. Rice husk ash (RHA) and activated charcoal were added as additives to improve the mechanical stability and porosity of the membrane. The synthesized tubular-shaped membrane was 100 mm in length, and it has 10 mm outside diameter and 5 mm inside diameter. X-ray diffraction and thermogravimetric and differential thermal analysis techniques were used to characterize the raw materials. The resulting bentonite membrane was analyzed by field emission scanning electron microscopy, mechanical strength, porosity, pure water flux, permeability, and pore size. In addition, the impact of sintering temperature on membrane properties was extensively studied. The membrane sintered at a temperature of 900 °C possesses a good porosity of 37% and exhibited an excellent flexural strength of 18 MPa. Besides, the membrane has shown better corrosion resistance towards acidic and basic environments. Permeability of the elaborated membrane was identified as 5.805 × 10−8 m3/m2 s kPa from pure water flux measurements, and its average pore size was estimated as 0.11 μm. Therefore, the prepared low-cost ceramic membrane could be predictable as a promising applicant for microfiltration applications due to its remarkable properties. The fabrication cost of the prepared tubular ceramic membrane was calculated as 96 $/m2. In addition, the environmental impacts of the fabricated membrane were assessed using GaBi ts 9.5.2.49 Pro software. It was observed that the majority of the impacts were primarily due to the power consumed during fabrication, and moving away from the conventional source of energy (fossil fuels) significantly (92.9%) reduced the impacts.

Effect of flow channel number in multi-channel tubular ceramic microfiltration membranes on flux and small protein transmission in milk protein fractionation

Ceramic multi-channel microfiltration (MF) membrane elements exist in various configurations, partially with high numbers of flow channels to increase the active membrane surface area and flux. The open question was how multi-channel membranes with different channel numbers perform in applications of protein fractionation, where not only flux, but more importantly, also transmission of components counts as decisive criteria. In this study, ceramic membrane elements with 1-, 7-, 19-, and 37-channels with the same outer diameter were compared with the task of milk protein fractionation in their main fractions (casein micelles, about d = 180 nm in diameter, and whey proteins, 4–8 nm in size) using 0.1 μm MF as technical example. Flux and therefore the advective protein transport towards the membrane surface was expected to differ between outer and inner channels owing to the different resistance to flow of the permeate from the inner channels to the outer rim of the ceramic element. In fact, the fouling intensity exerted by the retained biopolymers differed. Permeate flux, as well as whey protein transmission, depend on number and position of the individual channels. The 37-channel membrane element with more inner channels was found superior in terms of permeate volume flow and whey protein transmission. The results can be explained by the less pronounced deposit layer formation on the inner channels due to the higher backpressure for the permeate, which reduces the flux and, thus, the intensity of deposit layer formation of retained casein micelles rendering the membrane surface more open for whey protein transmission. • Concept for influence of flow channel number in multi-channel membranes. • Flux and transmission depends on the number and position of channels. • Deposit layer formation more intensive in outer channels due to backpressure. • 37-channel membrane element with more inner channels was found superior.

Membrane Filtration of Effluent from a One-Stage Bioreactor Treating Anaerobic Digester Supernatant

A challenge in side-stream treatment of anaerobic digester supernatant is that the effluent does not meet discharge standards. To address this challenge, this study tested tubular multichannel ceramic microfiltration (MF) and ultrafiltration (UF) membranes for the post-treatment of anaerobic digester supernatant. Pollutant rejection (total suspended solids (TSS), COD, total nitrogen (TN), and total phosphorus (TP)), color removal, and membrane susceptibility to fouling were determined at various transmembrane pressures (TMPs) (0.2, 0.3, 0.4, 0.5 MPa). Both methods completely removed TSS. In MF, COD was removed with 48–76% efficiency at 0.2–0.4 MPa. In UF, COD removal efficiency was slightly higher, reaching 83.7% at 0.4 MPa. With both methods, pollutant removal did not increase at TMP of 0.5 MPa. With both MF and UF, color was reduced by 54–100%, irrespective of the TMP. At 0.2–0.4 MPa, membrane resistance was lower and permeate flux was much higher with MF than UF. At 0.5 MPa, the methods differed only slightly from each other. Due to the larger cut-off, flux decline was slower in MF (0.7 h−1) than in UF (1.1 h−1), as the larger pore-size favors less foulant deposition. Thus, taking into account rejection efficiency, capacity, washing frequency, and cost (pressure), these results indicate that MF at 0.4 MPa is the most effective variant for post-treatment of anaerobic digester supernatant. With this variant, the almost colorless permeate contained 25 mg COD/L, no TSS, 55 mg TN/L (75% in the form of nitrites and nitrates), and 8.5 mg TP/L, thus meeting criteria for water to be used in irrigation or algae cultivation.

Development of new tubular ceramic microfiltration membranes by employing activated carbon in the structure of membranes for treatment of oily wastewater

Abstract In this research, the application of activated carbon and natural zeolite as absorbents and hydrophilic agents in the structure of a low-cost and high performance tubular ceramic microfiltration membrane for oily wastewater treatment was investigated. In this respect, Mullite, Mullite-Zeolite, and Mullite-Zeolite-Activated Carbon membranes were fabricated and characterized as ceramic MF membranes by using kaolin clay, natural zeolite and activated carbon powder. Performance of these membranes were assessed by comparing the quantity of permeation flux (PF) and total organic carbon (TOC) rejection during oily wastewater treatment where harsh conditions such as high oil concentration in various concentration of saline feed (0–200 g/L) were considered. Fouling and cleaning experiments were performed on oily waste water using a laboratory scale cross-flow test unit when NaOH was selected as a cleaning agent. Experimental results showed that the presence of activated carbon and natural zeolite in the structure of the membrane can enhance the permeation flux and total organic carbon rejection. Also, the permeation flux was highly dependent on the salt content of the feed solution. Actually, the flux improved sharply with the increase of salt content from 0 to 50 g/L, and then reduced slightly with further increase in salt concentration. In addition, total organic carbon rejection of up to 99.99% for Mullite-Zeolite-Activated carbon membrane was observed. The results of cleaning membrane process illustrated that the NaOH agent was able to clean the fouled MF membrane effectively. The exponential triple smoothing model was also used to predict the permeation flux in long periods.

Fabrication and characterization of low cost ceramic membranes for microfiltration of Acutodesmus obliquus using modified clays

ABSTRACT Tubular ceramic microfiltration membranes were prepared by extruding thermally treated clay (TC) and raw clay (NC) mixtures in different fractions with the addition of cationic manioc starch. Previous studies have verified that membranes containing TC possess higher hydraulic permeability and permeate flow values than those containing only NC for application in crossflow filtration. However, TC membranes had a low mechanical strength. Therefore, this study aimed to increase the mechanical strength without adversely affecting their permeate flow and hydraulic permeability. The physical, mineralogical, and morphological characteristics of the membranes were determined. The membranes were used for microfiltration of Acutodesmus obliquus microalgae with applied pressure of 1 bar with a volumetric flow rate of 250 L/h at a temperature of 10 ± 5°C. The efficiency of each ceramic membrane was evaluated in terms of the permeate flow for water and microalgae and hydraulic permeability. The mixture of 70% TC, 15% starch fractions and sintered at 1150°C exhibited optimal performance in mechanical strength (15.1±0.2 MPa), water permeate flow of 522.4±0.3 Kg•m-2•h-1, microalgae permeate flow of 114.8±0.8 Kg•m-2•h-1 and hydraulic permeability of 568.0±0.3 Kg•m-2•h-1•bar.

A rapid and scalable integrated membrane separation process for purification of polysaccharides from Enteromorpha prolifera

An integrated membrane separation process combining the tubular ceramic microfiltration (MF) membrane and the flat-sheet ultrafiltration (UF) membrane was developed to purify polysaccharides from Enteromorpha prolifera. The effects of membrane pore size, molecular weight cut-off (MWCO), transmembrane pressure (TMP) and adding-water multiples on membrane performance were in-depth studied. The results indicated that the optimal membrane pore size and TMP of the tubular ceramic MF process were found to be 1.2 μm and 0.225 MPa, and the optimal MWCO and TMP of the flat-sheet UF process were found to be 100 kDa and 0.3 MPa. The yields of polysaccharides were increased and optimized while the adding-water multiples was 1 during the diafiltration procedure. Furthermore, the water fluxes could be completely recovered using the specialized membrane cleaning methods, which ensured the reuse of membrane elements and satisfied the demands of industrial production. After purification by this integrated membrane separation process, the content of polysaccharides reached to 96.3%. The purified polysaccharides exhibited the superior moisture absorption and moisture retention properties compared to glycerol, polyethylene glycol (PEG) and luffa water.

Thermal treatment of clay-based ceramic membranes for microfiltration of Acutodesmus obliquus

Tubular ceramic microfiltration membranes were prepared by extruding thermally treated clay (TC) and raw clay to form a porous tubular membrane with the addition of cationic manioc starch and toasted manioc flour. The influence of an applied thermal treatment on the proprieties of the clay and the microfiltration membranes was characterized by measuring the particle size distribution, pore size distribution, and mechanical strength and by conducting X-ray fluorescence analysis, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The membranes were used for microfiltration of Acutodesmus obliquus microalgae with various applied pressures in the range of 2×104–1×105Pa with a volumetric flow rate of 6.94×10−5m3·s−1 at a temperature of 10±5°C. The efficiency of each of the ceramic membranes was evaluated in terms of the permeate flux for water and microalgae and the microalga retention. The addition of TC to the membrane resulted in an optimal microalga permeate flux of 3.24×10−2kg·m−2·s−1 and a microalga retention of 98.3% at 4×104Pa and had positive impacts on the other proprieties measured. Overall, these results demonstrate a potential application of TC in ceramic membranes for crossflow microfiltration processes.

Manufacturing of tubular ceramic microfiltration membrane based on natural pozzolan for pretreatment of seawater desalination

This work describes manufacturing of low-cost tubular ceramic microfiltration membrane made from natural pozzolan. Firstly, the tubular ceramic support was prepared by extrusion technique followed by sintering at low temperature of 950 °C. The extruded paste is essentially composed of pozzolan powder (<200μm), clay (<68μm), some organic additives and water. This formulation is conducted to obtain a ceramic support with uniform porous structure and high water permeability. Secondly, the membrane layer was prepared by cross-flow filtration of suspension containing the pozzolan powder (<45μm), polyvinyl alcohol and water, thereafter the membrane was dried and sintered at 950°C. Scanning electron microscope analysis showed that the membrane has homogenous structure and is free from any defect. In addition, the average pore size and water permeability parameters were respectively 0.36μm and 1444.7L/h·m2.bar.Manufactured membrane is expected to have challenge application in pretreatment of seawater for desalination. Membrane performance was evaluated by filtration of raw seawater in the aim of reducing its turbidity and its chemical oxygen demand. Experimental results showed a high rejection of turbidity (98.25%) as well as a good retention of chemical oxygen demand (70.77%).

Impact of algal organic matter released from Microcystis aeruginosa and Chlorella sp. on the fouling of a ceramic microfiltration membrane

Algal blooms lead to the secretion of algal organic matter (AOM) from different algal species into water treatment systems, and there is very limited information regarding the impact of AOM from different species on the fouling of ceramic microfiltration (MF) membranes. The impact of soluble AOM released from Microcystis aeruginosa and Chlorella sp. separately and together in feedwater on the fouling of a tubular ceramic microfiltration membrane (alumina, 0.1 μm) was studied at lab scale. Multi-cycle MF tests operated in constant pressure mode showed that the AOM (3 mg DOC L−1) extracted from the cultures of the two algae in early log phase of growth (12 days) resulted in less flux decline compared with the AOM from stationary phase (35 days), due to the latter containing significantly greater amounts of high fouling potential components (protein and humic-like substances). The AOM released from Chlorella sp. at stationary phase led to considerably greater flux decline and irreversible fouling resistance compared with that from M. aeruginosa. The mixture of the AOM (1:1, 3 mg DOC L−1) from the two algal species showed more similar flux decline and irreversible fouling resistance to the AOM from M. aeruginosa than Chlorella sp. This was due to the characteristics of the AOM mixture being more similar to those for M. aeruginosa than Chlorella sp. The extent of the flux decline for the AOM mixture after conventional coagulation with aluminium chlorohydrate or alum was reduced by 70%.

The effect of feed pretreatment on membrane microfiltration of titanium dioxide dispersions by ceramic tubular membranes

The influence of coagulant type and operating parameters on crossflow microfiltration of aqueous dispersions of titanium dioxide has been examined. The experiments were carried out with a tubular ceramic microfiltration membrane with a nominal pore size of 0.1μm at various operating parameters. Three chosen types of organic coagulants were used for a series of crossflow microfiltration experiments: polyacrylamide (PAM), poly(diallyldimethylammonium chloride) (PDADMAC), and poly(acrylamide-co-acrylic acid) partial sodium salt (PACA). The value of steady-state permeate flux has been experimentally evaluated for the crossflow microfiltration with and without pretreatment. The results of the experiments without coagulants showed that the flux initially declines rapidly and then stabilizes. The results also suggested that PDADMAC was a better coagulant for this system and its optimal concentration was 30 mg l−1. Finally, it was shown that pretreatment of the feed by PDADMAC resulted in a permeate flux that was more than three times higher than that obtained without any pretreatment. Moreover, there was a very positive effect of this coagulant on the particle size. Pretreatment by 30 mg l−1 PDADMAC led to an average particle size that was almost 18 times higher than that obtained without pretreatment. The other two coagulants did not produce such improvements: pretreatment of the feed by PAM increased the permeate flux by only 10%, while pretreatment by PACA gave even lower permeate flux than no pretreatment. This means that the results of various experiments have shown the need for careful selection of the coagulant due to their differing influences on the permeate flux. The relationship between the particle size of the dispersion and the permeate flux was found from the results of these experiments. A published mathematical model was used to estimate the permeate flux. The results of the experiments showed that the mathematical model was able to predict the steady-state permeate flux quite accurately in some cases.

Application of a novel gastrointestinal tract simulator system based on a membrane bioreactor (SimuGIT) to study the stomach tolerance and effective delivery enhancement of nanoencapsulated macelignan

In this research work, encapsulation of macelignan was performed in the lab by means of solid lipid nanoparticles (LNPs). The efficiency of the used nanoencapsulation technology was addressed with a focus on the enhancement towards the toleration of macelignan to the conditions of the stomach’s environment and in the intestine, for its effective delivery. Results were evaluated and contrasted with the absorption of free macelignan. For this purpose, a novel in-vitro gastrointestinal tract simulator system (GITS) named SimuGIT is presented, comprising a continuous stirred tank reactor (CSTR), simulating the conditions in the stomach and duodenum, connected in series to a continuous plug-flow tubular reactor (PFR) equipped with a tubular ceramic microfiltration (MF) membrane simulating the conditions and microvilli in the intestine. The net amount of macelignan LNPs within the absorbed product in the GITS was found to be over 10 times higher in terms of relative abundance than free macelignan. These promising results indicate that the produced LNPs permit macelignan resist the digestion process and enable the subsequent absorption of macelignan in the intestine. Furthermore, the LNPs were prepared from natural sources by using biocompatible components. Finally, the novel in-vitro GITS proposed stands out for its simplicity if compared to multi-vessel systems used in previous studies, and could be an easy platform to perform quick tests in order to assess the effective delivery of other compounds of interest.

Elaboration of novel tubular ceramic membrane from inexpensive raw materials by extrusion method and its performance in microfiltration of synthetic oily wastewater treatment

A tubular ceramic microfiltration membrane was prepared by an extrusion technique using inexpensive clay mixtures namely, ball clay, kaolin, feldspar, quartz, pyrophyllite and calcium carbonate. The mixture of clay powders extruded to form a porous tubular membrane without the addition of any organic additives. The dimensions, such as outer and inner diameters, wall thickness and length of the tube are 11.5, 5.5, 3 and 100mm, respectively. The sintered membrane possesses the porosity of 53%, water permeability of 5.93×10−7m/skPa, an average pore size of 0.309μm and mechanical strength of 12MPa with very good corrosion resistance in acidic and basic conditions. The fabricated membrane is expected to have potential applications in the pretreatment and also can be used as support for ultrafiltration membranes. With this intention, the membrane is subjected to microfiltration of synthetic oily wastewater emulsion experiments at various combinations of applied pressures (69–345kPa), feed concentrations (50–200ppm) and cross flow rates (5.55×10−7–1.66×10−6m3/s). An increase in the applied pressure and flow rate of oily wastewater emulsion result a decreased oil rejection while, an increase in the oil concentration results in enhanced rejection. The applied pressure of 69kPa offers the highest rejection of oily wastewater (99.98%) with permeate flux of 3.16×10−5m/s. Additionally, the membrane fouling mechanisms are investigated using diverse pore blocking models (complete, standard, intermediate pore blocking and cake filtration model) with obtained experimental data. It is found that the experimental results are well described by the cake filtration model. Finally, the rejection potential of the membrane is compared with other membranes reported in the literature.

Comparison of the performance of ceramic microfiltration and ultrafiltration membranes in the reclamation and reuse of secondary wastewater

Advanced treatment of secondary wastewater generally has been achieved using polymeric microfiltration and ultrafiltration membranes. Newly developed ceramic membranes offer distinctive advantages over the currently employed membranes and were recently introduced for the purpose. This paper presents results of a pilot study designed to investigate the application of ceramic microfiltration (MF) and ultrafiltration (UF) membranes in the recovery of water from secondary wastewater. Synthetic wastewater similar to the quality of secondary treated wastewater was fed to ceramic MF and UF system in a cross-flow mode. The filtration experiments revealed that the flux recovery through tubular ceramic MF membrane was more sensitive to the variation in TMP compared with the tubular ceramic UF membrane over the range of TMP studied. The resistance in series model was used for the evaluation of the resistance to the permeate flux. The results revealed that for ceramic UF membrane, the contribution to the total resistance of fouling was higher than the inherent of the clean membrane resistance. However, both the clean membrane resistance and the fouling resistance contribute equally in the case of MF membrane. Various wastewater indices were measured to evaluate the effectiveness of the filtration treatment. The ceramic UF membrane consistently met water quality in the permeate in terms of colour, turbidity, chemical oxygen demand and absorbance, suggesting that the permeate water could be made to be reused or recycled for suitable purposes. However, MF membrane appeared to be incompetent with respect to the removal of colour. The unified membrane fouling index (UMFI) was used to measure the fouling potential of both the membranes. The result showed that for UF membrane, the value of UMFI is one order of magnitude higher than MF membrane. The overall results suggest that there were significant differences in the performance of both the ceramic UF and MF membranes that are likely to impact on the operation and maintenance of the membrane system.

Understanding the fouling of a ceramic microfiltration membrane caused by algal organic matter released from Microcystis aeruginosa

Algal organic matter (AOM) released from Microcystis aeruginosa has high potential to cause fouling of water treatment membranes. The role of AOM components in the fouling of a commercial tubular ceramic microfiltration (MF) membrane (ZrO2–TiO2, 0.1µm) was investigated. The organic matter extracted from the three operationally-defined fouling layers (i.e., outer, middle and inner layer detached from the membrane using cross-flow flush, backwash and chemical cleaning, respectively) was characterised to gain an understanding of the fouling mechanism. The majority of the flux decline in the MF of the AOM solution was attributed to the large amount of organic matter (51% of total DOC of feed, primarily very high molecular weight (MW) hydrophobic molecules) deposited on the ceramic membrane surface to form a thick and dense outer layer. The middle layer contained a very small amount of organics (3%), mainly very high MW hydrophilic molecules, and contributed very little to the flux decline. The inner layer (22% of total DOC), which was responsible for the hydraulically irreversible fouling, was dominated by the high and low MW hydrophilic compounds. These molecules reached the membrane inner pores due to their hydrophilic nature, leading to pore restriction by adsorptive fouling.

Influence of the characteristics of soluble algal organic matter released from Microcystis aeruginosa on the fouling of a ceramic microfiltration membrane

The influence of the characteristics of soluble algal organic matter (AOM) on the fouling of a 7-channel tubular ceramic microfiltration membrane (ZrO2–TiO2, 0.1μm) was investigated at lab scale. The AOM (3mg DOC/L) extracted from a Microcystis aeruginosa culture at three phases of growth (10, 20 and 35 days) all caused severe flux decline, and its fouling potential increased with increasing growth time. Size exclusion chromatography, fluorescence excitation–emission matrix spectra and organic matter fractionation showed that the high MW biopolymers were the major component determining the severity of the AOM fouling of the ceramic membrane. For the AOM at stationary phase (35 days), 0.45 and 1μm pre-filtration gave greater flux decline and hydraulically irreversible fouling than 5μm pre-filtration due to the denser foulant layer formed and greater amounts of small organic molecules entering membrane pores. However, the non-pre-filtered AOM (with algal cells) caused the greatest flux decline which was likely due to the presence of the high fouling potential cell surface organic matter. The addition of calcium to the feed solutions led to a marked improvement in flux and reduction in membrane irreversible fouling due to the lower fouling potential of the AOM-calcium complexes formed.

Cell adhesion and related fouling mechanism on a tubular ceramic microfiltration membrane using Bacillus cereus spores

Adhesion of microorganisms to the membrane surface is an important and critical first step in biofilm fouling. Fouling mechanisms governing the adhesion of Bacillus cereus spores on a 0.45 μm tubular ceramic microfiltration membrane together with the relationship between hydraulic and microbiological cleanliness were investigated. Hydraulic cleanliness was evaluated using three parameters: percent flux recovery (FR), percent reversible removed fouling (RF) and a hydraulic cleanliness criterion (HCC). Microbiological cleanliness was assessed from the residual microbial population onto the membrane surface remaining after the fouling–rinsing sequence. The residual contamination (median value equal to 5.2 log cfu cm −2 for the whole set of experiments) was found to be uniform along the membrane path. Flux versus time curves supported the intermediate blocking filtration law at the initial stages of fouling during which microfiltration behaves as a dead-end filtration. Under fixed hydrodynamic shear conditions and solution chemistry (pH, ionic strength), cell – membrane adhesion was shown to be predominantly controlled by the permeation drag force. The residual contamination level could be predicted by means of a linear relationship involving two independent variables derived from fouling data: the blocked area per unit filtrate volume associated with the intermediate blocking filtration law ( σ) and a fouling parameter (noted F y ). A correlation was found between the residual spore population (median log N) and the residual irreversible fouling resistance. FR appeared to be a good indicator of microbiological cleanliness. A calculation using the actual shape of Bacillus cereus spores appeared to partly explain the discrepancies observed between the predicted and observed normalized flux decline following rinsing. This emphasized the large fouling capability of adhered bacteria, which resulted in the substantial water flux declines left after rinsing.

Cleaning kinetics and related mechanisms of Bacillus cereus spore removal during an alkaline cleaning of a tubular ceramic microfiltration membrane

In membrane separation processes, biofouling of membranes is now well recognized as a major impediment to their efficient operation and overall performance. This study focuses on the first (attachment) phase of biofouling. We have investigated experimentally the cleanability of a ceramic microfiltration membrane fouled by Bacillus cereus spores in terms of both hydraulic and microbiological cleanliness and examined the interrelationship between the two types of cleanliness. Cleaning kinetics was described in terms of both the hydraulic membrane resistance changes during cleaning and the number of residual adhered spores per unit membrane surface area as a function of time. Hydraulic cleanliness was evaluated using three parameters: percent flux recovery (FR), percent irreversible removed fouling (RF) and a hydraulic cleanliness criterion (HCC, i.e. (Rn–Rm)/Rm <0.05). Microbiological cleanliness was assessed by the measurement of the residual microbial population adhered to the membrane surface left after ...

Chemical cleaning of a tubular ceramic microfiltration membrane fouled with a whey protein concentrate suspension—Characterization of hydraulic and chemical cleanliness

The cleaning efficiency of a microfiltration membrane was characterized in terms of both chemical and hydraulic cleanliness and the existing relationships between flux recovery and the amount of proteins deposited on the membrane surface left after cleaning were searched. A 0.1 μm tubular ceramic microfiltration membrane fouled by a 3.5 wt% whey protein concentrate suspension was cleaned using sodium hydroxide. Hydraulic cleanliness was evaluated using three parameters: (i) percent flux recovery, (ii) percent irreversible removed fouling and (iii) a hydraulic cleanliness criterion representing the ratio of residual fouling resistance to initial membrane resistance. Chemical cleanliness was evaluated by means of the measurement of the amount of residual proteins deposited on the membrane surface following cleaning (expressed as μg cm −2 of membrane surface area). Three filtration operating parameters defining the cleaning operation were investigated: crossflow velocity, cleaning time and transmembrane pressure. Crossflow velocity had a slight beneficial influence on flux recovery but had no significant effect on the chemical cleanliness level ( p > 0.05). In contrast, flux recovery was greatly affected by transmembrane pressure which had a detrimental effect on hydraulic cleanliness. With an applied transmembrane pressure during cleaning, hydraulic cleanliness was not achieved in accordance with the presence of residual proteinaceous matter representing from 0.4% to 6% of the initial amount after fouling. An optimum cleaning time of 20 min has been highlighted for the chemical cleanliness whereas hydraulic cleanliness was not significantly affected by cleaning time ( p = 0.5). No linear correlation was found between the hydraulic and chemical cleanlinesses as a function of the cleaning operating conditions investigated. Percent flux recovery was insufficient in indicating accurately the chemical cleanliness.

The effect of pre-treatment on crossflow microfiltration of titanium dioxide dispersions

The influence of a coagulant type and operating parameters on crossflow microfiltration of aqueous dispersions of titanium dioxide was examined. Two types of coagulant for series of crossflow microfiltration experiments were used: inorganic—Al 2(SO 4) 3 and organic—PRAESTOL. The experiments were carried out on a tubular ceramic microfiltration membrane with nominal size of pores 0.1 μm at various operating parameters. Preliminary tests were performed before crossflow microfiltration experiments and from results of these tests were chosen optimal doses of coagulants. The value of steady state permeate flux was experimentally evaluated for crossflow microfiltration with and without pre-treatment. The results of the experiments show that aluminium sulphate is a better coagulant for this system and its optimal concentration is 40 mg/L. The results also show that pre-treatment of the feed led to four or five times higher permeate flux than that without any pre-treatment.