Flux Decline Mechanism Research Articles

Clarification of the Cardoon (Cynara cardunculus) Blanching Wastewater by Ultrafiltration—Study of Membrane Fouling and Flux Recovery after Chemical Cleaning

This study focused on the clarification of real blanching wastewaters from the industrial processing of cardoon, a plant rich in polyphenols and belonging to the artichoke family (Cynara cardunculus). The aim of this study was to evaluate the performance of ultrafiltration (UF) as an initial clarification step prior to a subsequent nanofiltration treatment for the recovery and fractionation of polyphenols from these wastewaters. In this UF process, three commercial UF membranes with different pore sizes: 3 kDa, 15 kDa, and 50 kDa. The assessment of the clarification process was based on two key factors: permeate flux and the concentration of phenolic compounds. The membrane with a MWCO of 3 kDa was excluded as a potential UF membrane due to its limited performance in terms of permeate flux. The 15 kDa membrane showed comparable results in terms of cumulative flux to the 50 kDa membrane. However, further evaluation based on fouling index and water permeability recovery favored the 15 kDa membrane, indicating better performance. To gain insights into the flux decline mechanisms and understand membrane fouling, a study was conducted on the 15 kDa and 50 kDa membranes. The analysis revealed that the cake filtration model provided the best fit for both membranes. The study highlights the potential of UF membranes, specifically the 15 kDa membrane, for the clarification of cardoon blanching wastewater.

Interdependence of Contributing Factors Governing Dead-End Fouling of Nanofiltration Membranes.

Cake-enhanced concentration polarization (CECP) has been ascribed as the main cause of flux decline in dead-end filtration. An unfamiliar approach was used to investigate the role of CECP effects in the fouling of a nanofiltration membrane (NF-270) that poorly reject salts. Membrane–foulant affinity interaction energies were calculated from measured contact angles of foulants and membrane coupons based on the van der Waals/acid–base approach, and linked to resistance due to adsorption (Ra). In addition, other fouling mechanisms and resistance parameters were investigated using model organic and colloidal foulants. After selection, the foulants and membranes were characterized for various properties, and fouling experiments were conducted under controlled conditions. The fouled membranes were further characterized to gain more understanding of the fouling layer properties and flux decline mechanisms. Sodium alginate and latex greatly reduced membrane permeate flux as the flux declined by 86% and 59%, respectively, while there was minor flux decline when aluminum oxide was used as model foulant (<15% flux decline). More flux decline was noted when fouling was conducted with a combination of organic and colloidal foulants. Contrary to other studies, the addition of calcium did not seem to influence individual and combined fouling trends. Foulants adsorbed more on the membrane surface as the membrane–foulant affinity interactions became more attractive and pore blocking by the foulants was not important for these experiments. Hydraulic resistance due to cake formation (Rc) had a higher contributing effect on flux decline, while CECP effects were not substantial.

Harvesting of Microalgae Biomass Using Ceramic Microfiltration at High Cross-Flow Velocity.

This study aimed to investigate the harvesting of microalgae by microfiltration (MF) on a ceramic membrane at relatively high cross-flow velocity (CFV) of interest for commercial processes. Pilot-scale harvesting was conducted with algal suspensions (Chlorella vulgaris and Tisochrysis lutea (T-Iso)) and algal supernatants (Porphyridium cruentum) to assess the effect of feedstock characteristics and understand flux decline mechanisms. In total recycle mode (C. vulgaris, 1g/L), high steady-state permeation flux around 200L/m2/h was achieved. Total filtration resistance was mainly due to cake resistance (Rc, 57%) and pore adsorption and blocking (Ra, 40%). The process hydrodynamic conditions seemed to have relatively little effect on Chlorella cell integrity. In concentration mode, average permeate flux decreased from 441 to 73L/m2/h with increasing feed concentration (C. vulgaris, 0.25-1g/L); the contribution of Rc decreased (82 to 57%), while that of Ra rose (7 to 40%). With T-Iso suspensions and P. cruentum supernatants at 1g/L, average permeate flux was 59 and 49L/m2/h, respectively, with predominance of Rc and Ra, respectively. Distinct fouling mechanisms were inferred to explain the superior filterability of C. vulgaris. The results show that ceramic membrane MF at relatively high CFV could be a suitable option for harvesting certain microalgae including C. vulgaris.

Synthesis, characterization and performance studies of kaolin-fly ash-based membranes for microfiltration of oily waste water

The present study deals with the synthesis, characterization, and performance evaluation of low-cost porous ceramic microfiltration membranes for separation of oily waste water. Ceramic membranes were synthesized following paste-casting method using three different ratios of kaolin to coal fly ash, in combination with a few selected suitable pore - formers and binders like calcium and sodium carbonate, boric acid, and sodium metasilicate. The synthesized membranes were characterized using the field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and water permeation tests with the objective of investigating the influence of sintering temperature (750 °C–900 °C) and precursor ratio on the microstructural evolution of the fabricated membranes. Three varying concentrations of oil-in-water (O/W) emulsions (100, 200, and 300 mg/L) prepared using a typical crude oil collected from an oil field located in Digboi, India was used as a representative sample and tested for the microfiltration studies. A fabricated membrane with a porosity (~34.36–39.0%), pore size (~0.65–1.81 μm) showed an excellent separation efficiency of 96.7–99.5% with a permeate flux around ~ 24.3 × 10−5 m3 m−2 s−1. The flux decline mechanism was analyzed using the pore blocking models, and it was observed that the cake filtration model followed by the intermediate pore-blocking model were the best - fitted models as compared to others to describe the permeate flux data. The fabricated kaolin-fly ash-based membranes exhibited good permeability and separation efficiency characteristics, which suggest its suitability for microfiltration of oily waste water from oil exploration and refinery industries.

Application of peroxymonosulfate-based advanced oxidation process as a novel pretreatment for nanofiltration: Comparison with conventional coagulation

As a practical advanced oxidation process with high-efficiency, ferrous-activated peroxymonosulfate (PMS) technology has been extensively investigated and employed for the degradation of organic substances in water treatment process. However, to our best of knowledge, few studies in applying ferrous-activated PMS as the pretreatment for nanofiltration process have been conducted and the mechanisms of membrane fouling alleviation due to ferrous-activated PMS was still unclear. Consequently, ferrous-activated PMS approach was innovatively adopted as pretreatment for nanofiltration in present study, compared with the conventional pretreatment process (coagulation). The results indicated that both strategies could significantly mitigate organic fouling at membrane surface, but the gypsum scaling was enhanced when Fe(II)/PMS was adopted prior to nanofiltration process at the dose of 80/80 μM, because of the assistance of ferric ions and sulfate anions. ATR-FTIR spectra indicated that the greater alleviation of flux decline caused by Fe(II)/PMS oxidation was attributed to the less accumulation of organic substances on membrane surface, relative to the conventional Fe(III) coagulation. Furthermore, Xtended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was utilized to explain the greater interfacial free energy of adhesion (equal to decreased repulsion or increased attraction) between foulants and nanofiltration membranes in ferrous-activated PMS strategies joined nanofiltration process. Interestingly, Fe(II)/PMS oxidation could efficiently improve the quality of effluent in nanofiltration process, and three-dimension excitation emission matrix fluorescence spectroscopy (3D-EEM) spectra demonstrated that Fe(II)/PMS conferred higher removals of organic substances. The removal efficiency of Bisphenol A in Fe(II)/PMS assisted nanofiltration process varied from 53% to 78%, while only 5–12% Bisphenol A was removed in Fe(III) coagulation joined system. Besides, the potential mechanisms of flux decline caused by individual and combined organic substances were also investigated. Therefore, the findings in present study would contribute to the deep understanding of membrane fouling mechanism and promote the practical application of nanofiltration technologies.

Application of a Low Cost Ceramic Filter for Recycling Sand Filter Backwash Water

The aim of this study is to examine the application of a low cost ceramic filter for the treatment of sand filter backwash water (SFBW). The treatment process is comprised of pre-coagulation of SFBW with aluminum sulfate (Alum) followed by continuous filtration usinga low cost ceramic filter at different trans-membrane pressures (TMPs). Jar test results showed that 20 mg/L of alum is the optimum dose for maximum removal of turbidity, Fe, and Mn from SFBW. The filter can be operated at a TMP between 0.6 and 3 kPa as well as a corresponding flux of 480–2000 L/m2/d without any flux declination. Significant removal, up to 99%, was observed forturbidity, iron (Fe), and manganese (Mn). The flux started to decline at 4.5 kPa TMP (corresponding flux 3280 L/m2/d), thus indicated fouling of the filter. The complete pore blocking model was found as the most appropriate model to explain the insight mechanism of flux decline. The optimum operating pressure and the permeate flux were found to be 3 kPa and 2000 L/m2/d, respectively. Treated SFBW by a low cost ceramic filter was found to be suitable to recycle back to the water treatment plant. The ceramic filtration process would be a low cost and efficient option to recycle the SFBW.

Running-wheel activity delays mitochondrial respiratory flux decline in aging mouse muscle via a post-transcriptional mechanism.

SummaryLoss of mitochondrial respiratory flux is a hallmark of skeletal muscle aging, contributing to a progressive decline of muscle strength. Endurance exercise alleviates the decrease in respiratory flux, both in humans and in rodents. Here, we dissect the underlying mechanism of mitochondrial flux decline by integrated analysis of the molecular network.Mice were given a lifelong ad libitum low‐fat or high‐fat sucrose diet and were further divided into sedentary and running‐wheel groups. At 6, 12, 18 and 24 months, muscle weight, triglyceride content and mitochondrial respiratory flux were analysed. Subsequently, transcriptome was measured by RNA‐Seq and proteome by targeted LC‐MS/MS analysis with 13C‐labelled standards. In the sedentary groups, mitochondrial respiratory flux declined with age. Voluntary running protected the mitochondrial respiratory flux until 18 months of age. Beyond this time point, all groups converged. Regulation Analysis of flux, proteome and transcriptome showed that the decline of flux was equally regulated at the proteomic and at the metabolic level, while regulation at the transcriptional level was marginal. Proteomic regulation was most prominent at the beginning and at the end of the pathway, namely at the pyruvate dehydrogenase complex and at the synthesis and transport of ATP. Further proteomic regulation was scattered across the entire pathway, revealing an effective multisite regulation. Finally, reactions regulated at the protein level were highly overlapping between the four experimental groups, suggesting a common, post‐transcriptional mechanism of muscle aging.

A systematic optimization of Internally Staged Design (ISD) for a full-scale reverse osmosis process

In this study, Internally Staged Design (ISD) was numerically optimized in order to demonstrate the long-term performance of full-scale seawater reverse osmosis (SWRO) membrane systems in the presence of colloidal foulants. To this end, a numerical model based on a finite difference method was developed and optimized with various feed water qualities, such as fouling potential and total dissolved solids (TDS). As a result, the optimized ISD exhibited greater water flux and higher energy efficiency in long-term operation (90 days) compared to conventional designs, where single-type membrane elements were employed over a pressure vessel while achieving potable TDS concentration in permeate (< 400mg/L). This enhanced performance was attributed to the reduction of colloidal fouling on the lead elements and the alleviation of concentration polarization (CP) at the tail elements. Among fouling mechanisms, cake-enhanced concentration polarization (CECP) played a dominant role in flux decline at the lead elements, whereas CP was the chief flux decline mechanism at the tail elements. In addition, it was found that the employment of a low-permeability membrane at the lead element was important to maintain acceptable TDS in the permeate at either high TDS or high fouling potential of feed water.

Membrane distillation of high salinity wastewater from shale gas extraction: effect of antiscalants

AbstractAlthough shale gas has become an important source of natural gas, it has problems associated with water pollution by producing high salinity wastewater (i.e. TDS > 100,000 mg/L). Membrane distillation (MD) can be applied to treat such wastewater but may suffer from fouling due to scale formation. Accordingly, this study focused on the use of antiscalants to retard scale formation in MD process for the treatment of high salinity wastewater. Experiments were performed using a laboratory-scale direct contact MD (DCMD) system. Seven different antiscalants were applied to the simplified synthetic wastewater. The results were analyzed using a simple theoretical model. It was found that the abilities to retard scale formation were different for different antiscalants. The difference in chemical structures of the antiscalants was attributed to the changes in their effect on scale prevention. Moreover, the mechanisms of flux decline seem to be different in the presence of antiscalants. Not only surface blo...

Effects of organic and colloidal fouling on the rejection of two pharmaceutically active compounds (PhACs) by nanofiltration processes: role of membrane foulants

Results reported here indicate that membrane fouling could influence the removal of two pharmaceutically active compounds (PhACs) namely sulfamethoxazole and carbamazepine, by a nanofiltration process. The effects of membrane fouling on solute rejection by the tight nanofiltration (NF)-90 membrane were quite negligible. In contrast, remarkable effects of membrane fouling on the rejection of both inorganic salts and PhACs were observed with the larger pore size NF-270 membrane. The effects of membrane fouling on solute rejection were strongly foulant-dependent. The three model foulants (sodium alginate, bovine serum albumin, and silica colloid) used in this study resulted in three distinctive modes of membrane fouling. Subsequently, these three modes of membrane fouling consistently showed different effects on the membrane separation efficiency. Inorganic colloidal fouling resulted in the most severe rejection decrease while causing the least permeate flux decline. This observed reduction in rejection could be attributed to the cake-enhanced concentration polarization phenomenon that was also thought to be the primary mechanism of flux decline in inorganic colloidal fouling. In contrast, organic fouling caused by the model foulant alginate led to a lesser decrease in the rejection of PhACs despite the fact that alginate caused the most severe flux decline.

Study of different fouling mechanisms during membrane clarification of red plum juice

SummaryIn this study, the flux decline mechanisms were identified during membrane clarification of red plum juice at several processing parameters, including pore size, membrane type, transmembrane pressure, temperature and velocity. The results were used to investigate the effect of changes in operating conditions on the intensity of membrane fouling. Also, scanning electron microscopy (SEM) was used for analysing fouling‐layer morphology. These results showed that the main mechanism responsible for membrane fouling was cake formation (over 95% fitness) occurring in the first stage of the process. Intermediate, standard and complete blockings were formed during most of the runs as filtration proceeded. The results also indicated that increasing the temperature from 30 to 40 °C was the most effective factor in decreasing cake‐layer fouling, reducing it by about 66.7%. Furthermore, an increase in processing velocity of up to 0.5 m s−1 had the greatest effect on intermediate blocking, reducing it by about 86.1%. Also, increasing pressure up to 2.9 bar completely eliminated standard blocking and complete blocking. Finally, microstructure analysis of membrane using SEM confirmed that cake formation had the greatest impact on membrane fouling.

Prefiltration to suppress protein fouling of microfiltration membranes

The effect of prefiltration using membranes with pore sizes of 1.0, 0.45 and 0.22μm on the permeate flux during direct flow (dead end) filtration using 0.45μm polytetrafluoroethylene (PTFE) and polyvinyl alcohol (PVA) coated PTFE membranes has been investigated. Feed solutions consisted of lysozyme, β-lactoglobulin, ovalbumin and hemoglobin. Prefiltration with a 1.0μm pore size membrane led to a stable permeate flux for the lysozyme containing feed stream but was ineffective at preventing severe permeate flux decline for hemoglobin containing feed streams for both membranes. For β-lactoglobulin and ovalbumin, prefiltration with a 1.0μm pore size membrane led to stable permeate flux for the PTFE membrane but was ineffective at preventing severe permeate flux decline for the more hydrophilic PVA coated PTFE membrane probably due to the smaller effective pore diameter of this membrane following coating.However, prefiltration with a 0.45 or 0.22μm pore size membrane led to stable permeate flux for all proteins and both membranes. The results indicate the importance of prefiltration to maximize permeate flux, suggesting that flux decline is due to adsorption and deposition of aggregated proteins on the membrane surface.Analysis of FESEM images and ATR-FTIR spectra of virgin and fouled membranes support the flux data and highlights the value of these techniques when investigating mechanisms of flux decline. The results obtained here support earlier work that indicates it is the interplay among membrane properties, protein properties and operating conditions that determines the extent of fouling and flux decline.

Aluminum electrocoagulation pretreatment reduces fouling during surface water microfiltration

A bench-scale study was undertaken to evaluate aluminum electrocoagulation pretreatment for dead-end, constant pressure microfiltration of surface water. Electrochemical aluminum production quantitatively obeyed Faraday's law with a 3-electron transfer at nearly 100% efficiency resulting in Al(OH) 3 precipitation. X-ray diffractometry proved that Al(OH) 3 precipitates were predominantly amorphous. Enmeshment of colloids in amorphous precipitates (sweep flocculation) was the predominant colloid destabilization mechanism. Additionally, the floc zeta potential became less negative (→0) as more and more aluminum was added indicating the secondary role of adsorption of hydrolyzed aluminum species and charge neutralization in destabilization. Fouling of a commercially available polymeric microfiltration membrane following electrocoagulation pretreatment was found to (i) be lower at pH 6.4 compared with 7.5, (ii) decrease only up to an intermediate aluminum dosage, and (iii) exacerbate with increasing transmembrane pressure. In all experiments, cake filtration was the predominant flux decline mechanism for the entire duration of microfiltration. Increased fouling at higher transmembrane pressures (manifested as more rapid decline of the instantaneous flux normalized by the initial flux) was attributed to cake compressibility. Optical microscopy revealed that floc sizes increased monotonically with aluminum dosage even though fouling worsened at high electrocoagulant concentrations. This suggests that fouling was controlled by antagonistic effects of adding more and more aluminum coagulant; increasing total mass loading of colloidal foulants (higher total filtration resistance) and creating larger flocs (decreasing specific cake resistance). Significant reductions in microfilter fouling with aluminum electrocoagulation pretreatment suggests the next logical step of larger-scale testing under “real-world” conditions before recommending it for surface water treatment.

Reverse osmosis concentration of press liquid from orange juice solid wastes: Flux decline mechanisms

Orange juice production produces high amount of solid waste. An alternative for these wastes is their pressing with lime to obtain a press liquor stream and a dried solid for cattle feeding. The press liquor (around 10 °Brix) is traditionally concentrated up to 70 °Brix (citrus molasses) by multiple effect evaporation. In this investigation, reverse osmosis is evaluated as an alternative for press liquor preconcentration. Two synthetic feed solutions were studied, one included pectin in its composition (WP) and the other lacked pectin (WOP) to simulate a previous depectinization of WP. The concentration process was evaluated in terms of some selected parameters (chemical oxygen demand, total soluble solids, total dissolved solids and osmotic pressure). The fouling mechanism as well as the membrane resistance to the permeate pass were assessed. It was found that for later stages of concentration cake filtration was the dominant fouling mechanism while for earlier stages, the mechanism found was the complete pore blocking. The presence of pectin not only maximized the membrane fouling but also led to worse permeate quality.

Flux decline analysis in micellar-enhanced ultrafiltration of synthetic waste solutions for metal removal

It is known that micellar-enhanced ultrafiltration (MEUF) is an efficient and economic process for the removal of trace metal ions and organics from aqueous media. In this work, flux decline behavior in MEUF of aqueous solutions containing trace Cu(II) (1.6–8 mM) and anionic surfactants sodium dodecyl sulfate (SDS) or sodium dodecyl benzene sulfate (SDBS) was studied at 25 °C in batch mode. An UF membrane that had average pore size comparable to those of Cu(II)-adsorbed micelles was adopted. All experiments were performed as a function of stirring speed (200–400 rpm), solution pH (3.0–5.0), molar concentration ratio of surfactant to metal (S/M, 2.5–12.7), and applied pressure (69–345 kPa). It was shown that more than 90% of Cu(II) could be removed at an S/M ratio of 12.7 and pH 5 using SDS. The blocking filtration law was used to identify the mechanism(s) of flux decline during the MEUF processes. Finally, the specific cake resistances in both SDS and SDBS systems were evaluated and compared.

Quantification of transient flux decline during membrane separation of tanning effluent from tannery

Cake filtration model is described to establish/quantify transient flux decline mechanism for membrane separation of tanning effluent collected from tannery. Two membrane operations, Nanofiltration (NF) followed by Reverse Osmosis (RO), are adopted to treat tanning effluent. The experiments are conducted in a continuous cross-flow mode of operation. Three-flow regimes, namely, laminar, laminar with promoter and turbulent are investigated. Both for NF and RO, maximum cake resistance is observed in laminar flow regime followed by laminar with promoter and is the least in case of turbulent regime. For the nanofiltration process, the contributions of cake resistance towards total resistance are 85-88% for turbulent flow regime, 90-91% for laminar with turbulent promoter and maximum for purely laminar flow regime, which is 92-93%. In RO, cake resistance varies between 70-75% for turbulent flow regime, whereas it is 81% for laminar flow regime and 77% for laminar with turbulent promoter regime.

Effects of solid concentrations and cross-flow hydrodynamics on microfiltration of anaerobic sludge

The filtration characteristics and rheological properties of anaerobic sludge suspension containing different solid content were investigated using poly-tetrafluoroethylene (PTFE) microfiltration membrane with a pore size of 1 μm. The initial rapid flux decline was in good agreement with standard blocking filtration law, while the latter gentle flux decline is attributable to the cake filtration law, which represented a Class II type dynamic membrane. The highest pseudo-steady-state flux and lowest normalized flux reduction were observed at total solids (TS) concentration of 13–18 g/L. Initial standard blocking significantly affects the flux decline mechanism at TS concentrations of 10 g/L or below and cake formation dominates the flux decline at higher TS concentrations above 25 g/L. TS concentration significantly affected rheological properties as well as flux decline in microfiltration of anaerobic sludge. TS concentration of 5 g/L or less characterizes the transition from Newtonian to non-Newtonian behavior. Both Casson and power-law equations were fit for rheological modeling of anaerobic sludge with TS concentration of 10 g/L or above. The minimum cross-flow velocity (CFV) to produce turbulent flow (Reynolds number ∼ 2100) increased almost linearly to 0.5–0.8 m/s at TS concentration of 10–20 g/L. The concentration of soluble microbial products (SMP) was increased and the mean particle size was decreased with increase of CFV. Extracellular polymeric substances (EPS) even decreased after 6 h filtration runs. Some of EPS might contribute to the increased SMP due to cell lysis.

Treatment of Oily Waste Water Using Low-Cost Ceramic Membrane: Flux Decline Mechanism and Economic Feasibility

This work addresses the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration (MF) of stable oil-in-water (o/w) emulsions using relatively low-cost ceramic membranes. Circular disk type membranes (52.5 mm diameter and 4.5 mm thickness) were prepared by the paste method using locally available low-cost inorganic precursors such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium metasilicate. Characterization of the prepared membrane was done by SEM analysis, porosity determination, and pure water permeation through the membrane. Hydraulic pore diameter, hydraulic permeability, and hydraulic resistance of the membrane was evaluated as 0.7 µm, 1.94 × 10−6 m3/m2·s·kPa and 5.78 × 1011 m2/m3, respectively. The prepared membrane was used for the treatment of synthetic stable o/w emulsions of 40 and 50 mg/L crude oil concentration in batch mode with varying trans-membrane pressure differentials ranging from 41.37 to 165.47 kPa. The membrane exhibited 96.97% oil rejection efficiency and 21.07 × 10−6 m3/m2·s permeate flux after 30 min of experimental run at 165.47 kPa trans-membrane pressure for 50 mg/L oil concentration. Different pore blocking, models such as complete pore blocking, standard pore blocking, intermediate pore blocking and cake filtration were used to gain insights into the nature of membrane fouling during permeation. The observed trends for flux decline data convey that the decrease in permeate flux was initially due to intermediate pore blocking (during 1 to 10 minutes of experimental run) followed with cake filtration (during 10 to 30 minutes of experimental run). Based on retail prices of the inorganic precursors, the membrane cost was estimated to be 130 $/m2. Finally, preliminary process economic studies for a single stage membrane plant were performed for the application of the prepared membrane in industrial scale treatment of o/w emulsions. A process economics study inferred that the annualized cost of the membrane plant would be 0.098 $/m3 feed for treating 100 m3/day feed with oil concentration of 50 mg/L.

Generalized criteria for identification of fouling mechanism under steady state membrane filtration

Generalized criteria for the determination of fouling mechanism during cross flow membrane filtration are obtained. Two mechanisms, namely, complete pore blocking and cake formation over the membrane surface, in sequence, are considered. A set of three non-dimensional parameters have been evolved to control the mechanism of flux decline during filtration. Depending upon the relationship of these parameters, the various characteristic filtration regions have been identified. The effects of various parameters on the relative importance of both the resistances (complete pore blocking resistance and cake resistance) are analyzed. For example, steady state value of the permeate flux has profound influence on the onset of cake formation as well as the dynamics of the complete pore blocking phenomena. One can achieve higher permeate flux for a suitable combination of parameters in all the three regions.

Mechanism of Permeate Flux Decline during Microfiltration of Watermelon (Citrullus lanatus) Juice

Flux decline mechanism during microfiltration of watermelon juice was studied in detail. Identification of the flux decline mechanism was carried out by conducting experiments in an unstirred batch cell. Using the identified mechanism, flux decline was predicted during stirred microfiltration in a continuous mode. The operating pressure range was from 137 to 276 kPa and that of Reynolds number was 1.40 × 105 to 1.87 × 105. Cake formation was identified as the main reason for flux decline. Prediction of flux decline during stirred continuous microfiltration using this mechanism was found adequate.