• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.6
• /
• pp.855-864
• /
• 2009

The main object of this work was to determine the influence of periodic chemical backwash on filtration resistance in membrane filtration system. In this work Hermia's models were used to investigate the fouling mechanisms involved in the microfiltration of $0.45{\mu}m$ filtered sewage feed. Batch microfiltration experiments were performed at transmembrane pressure 0.4 bar and different feed SCOD concentration (9~67 mgSCOD/L). The results showed that the best fit to experimental data corresponded to the intermediate blocking model followed by the standard and complete blocking model for all the experimental conditions tested. From the simulation results of filtration performance, it was found that in order to maintain sustainable operation of membrane filtration system, irreversible foulant component accumulated continuously on membrane surface and/or pore must be effectively removed. In addition, it was verified that periodic chemical backwash using NaOCl or NaOH effectively improved filtration performance of membrane.

• Membrane Journal
• /
• v.29 no.6
• /
• pp.329-338
• /
• 2019

The constant-pressure and constant-flux membrane filtration experiments of alumina colloidal solution are performed to investigate defouling effect of the natural convection instability flow (NCIF) induced in membrane module. The permeate flux at constant-pressure and the transmembrane pressure (TMP) at constant-flux experiments are measured by changes the inclined angle (0, 90 and 180°) of membrane module to the gravity, and flux results are analyzed by using the blocking filtration model. NCIF are more induced as the inclined angles increased from 0° to 180°, and the maximum induced NCIF at 180° angle enhances flux to 2.8 times and reduces TMP to 85% after two-hour operation. As a result of analyzing flux data by applying the blocking filtration model, it is more reasonable to analyze them by using the intermediate blocking model within 15-minute operation time and then thereafter times by using the cake filtration model. The induced NCIF at 180° angle reduces the intermediate blocking fouling at 52% in the early operation time of 15-minute and thereafter the cake layer fouling at 93%. The main membrane fouling control mechanism of NCIF induced in membrane module is evaluated as suppressing the formation of the cake layer of particulate colloidal materials on membrane surface.

• Membrane Journal
• /
• v.29 no.1
• /
• pp.18-29
• /
• 2019

The dead-end ultrafiltration (UF) of BSA protein solution was performed to investigate the defouling effects of natural convection instability flow (NCIF) induced in membrane module. The permeate fluxes were measured according to the inclined angles ($0{\sim}180^{\circ}$) of membrane module with respect to gravity, and analyzed using the blocking filtration model. NCIF are more induced as the inclined angles increased from $0^{\circ}$ to $180^{\circ}$, and the induced NCIF enhances flux. Comparing the fluxes at $0^{\circ}$ inclined angle (no NCIF induction) and $180^{\circ}$ (maximum NCIF induction), the flux enhancements by NCIF induction are increased about 5 times in the short-term UF operation (2 hours) and about 17 times in the long-term operation (20 hours). As applying the blocking filtration model, it is more suitable to analyze the flux results by using the intermediate blocking model in the early times of UF operation within 15 minutes and then thereafter times by using the cake filtration model. NCIF induced at $180^{\circ}$ inclined angle reduces the intermediate blocking fouling at about 67% in the early times operation and thereafter the cake layer fouling at about 99.9%. The main defouling mechanism of NCIF induced in the membrane module is suppress the formation of protein cake layer.

• Membrane Journal
• /
• v.19 no.1
• /
• pp.34-46
• /
• 2009

Effect of backflushing on the membrane fouling for polyethylene capillary membranes was examined by measuring the flux of $Al_2O_3$ colloidal suspensions through the cross flow microfiltration. In the comparison of with and without the application of backflushing, the hydraulic resistance to permeate flow of the suspension was less with backfluslng, but the Increasing rate in permeate resistance was higher. Regardless of backflushing, the cake filtration was dominant at the initial period of filtration with backflushing, being followed by the pore blocking. And at steady state, the fouling mechanism is almost governed by the cake filtration model. On the contrary, the pore blocking preceded the cake filtration in the initial stage of the original membrane before backflushing. And irrespective of backflushing, the ratio of cake filtration to total fouling increased, compared with that fur before backflushing. For the membrane with $0.24{\mu}m$ pore size, the permeate resistance was higher than that of $0.34{\mu}m$ pore size membrane. but the ratio of cake filtration was smaller than that of large pore membrane. In comparing the ratio of each fouling component to the total fouling for the case with backflushing pore blocking was 7.8% and cake filtration was 92.2%. for the case without backflushing, total fouling was composed of 9.6% pore blocking and 90.4% cake filtration.

• Membrane and Water Treatment
• /
• v.1 no.4
• /
• pp.297-316
• /
• 2010

Membrane fouling is one of the major operational concerns of membrane processes which results in loss of productivity. This paper investigates the ultrafiltration (UF) results of synthetic oil-in-water (o/w) emulsion using flat sheets of polysulfone (PSf) membrane synthesized with four different compositions. The aim is to identify the mechanisms responsible for the observed permeate flux reduction with time for different PSf membranes. The experiments were carried out at four transmembrane pressures i.e., 68.9 kPa, 103.4 kPa, 137.9 kPa and 172.4 kPa. Three initial oil concentrations i.e., 75 $mgL^{-1}$, 100 $mgL^{-1}$ and 200 $mgL^{-1}$ were considered. The resistance-in-series (RIS) model was applied to interpret the data and on that basis, the individual resistances were evaluated. The significances of these resistances were studied in relation to parameters, namely, transmembrane pressure and initial oil concentration. The total resistance to permeate flow is found to increase with increase in both transmembrane pressure and initial oil concentration while for higher oil concentration, resistance due to concentration polarization is found to be the prevailing resistance. The applicability of the constant pressure filtration models to the experimental data was also tested to explain the blocking process. The study shows that intermediate pore blocking is the dominant mechanism at the initial period of UF while in the later period, the fouling process is found to approach cake filtration like mechanism. However, the duration of pore blocking mechanism is different for different membranes depending on their morphological and permeation properties.

• Korean Membrane Journal
• /
• v.5 no.1
• /
• pp.31-35
• /
• 2003

The permeation characteristics of the wastewater containing Si fine particles were examined by ultrafiltration using the polyolefin tubular membrane module. Flux with time was due to the growth of Si cake deposited on the membrane surface and the pore plugging by fine particles. The rate of flux decline in the initial stage increased with the trans-membrane pressure. The pore blocking resistance was the dominant resistance at the initial period of filtration and the cake resistance began to dominate with the initial pore blocking resistance. The larger pores compared with the fine particles, the more the membrane pores could be blocked by the fine particles. Before and after treatment, the distribution of particle size was shifted toward to the left. Then, the average size of fine particles in the permeate was 20 nm.

• Membrane and Water Treatment
• /
• v.9 no.5
• /
• pp.343-351
• /
• 2018

As membrane fouling is based on various factors, it is a complex phenomenon that is hard to estimate. This study investigated membrane fouling in a thermophilic jet loop membrane bioreactor (JLMBR). With this purpose, four different empirical membrane fouling models with different sludge retention times were applied on the flow data obtained in the system. As a result of the model implementation, it was found for all sludge retention times that, standard blocking is effective in the first 1.5 hours of filtration, while cake filtration was dominant in the remaining duration. Additionally, it was observed that as the sludge retention time increases, membrane fouling rate decreases.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1999.07a
• /
• pp.95-96
• /
• 1999

The ultrafiltration behavior of dilute colloidal solution containing Si particles has been investigated. The experiments in cross flow mode have been performed at different operating condition by using the membrane with 20 kDa cut-off. The flux decline was due to the development of membrane fouling which was a dynamic process of two distinctive stages. For the high trans-membrane pressure, the pore blocking resistance was dominant at the initial period of filtraion and was followed by the cake resistance. And for the low cross flow velocity, the membrane fouling was governed by the cake filtration model at the initial stage of filtration process. Flux jump was observed temporally during the membrane filtration of mixed feed solution.

• Membrane and Water Treatment
• /
• v.9 no.5
• /
• pp.373-383
• /
• 2018

Fouling by solids and microorganisms is the major obstacle limiting the efficient use of membrane wastewater treatment. In our previous study, two stages microalgae/membrane filtration system was proposed to treat anaerobic digested palm oil mill effluent (AnPOME). This two stages microalgae/membrane filtration system had showed great potential for the treatment of AnPOME with high removal of COD, $NH_3-N$, $PO_4{^{3-}}$, TSS, turbidity, and colour. However, fouling behavior of the membrane in this two stages microalgae/membrane filtration system was still unknown. In this study, empirical models that describe permeate flux decline for dead-end filtration (pore blocking - complete, intermediate, and standard; and cake layer formation) presented by Hermia were used to fit the experimental results in identifying the fouling mechanism under different experimental conditions. Both centrifuged and non-centrifuged samples were taken from the medium with 3 days RT intervals, from day 0 to day 12 to study their influence on fouling mechanisms described by Hermia for ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) filtration mode. Besides, a more detailed study on the use of resistance-in-series model for deadend filtration was done to investigate the fouling mechanisms involved in membrane filtration of AnPOME collected after microalgae treatment. The results showed that fouling of UF and NF membrane was mainly caused by cake layer formation and it was also supported by the analysis for resistance-in-series model. Whereas, fouling of RO membrane was dominated by concentration polarization.

• Journal of Korean Society of Water and Wastewater
• /
• v.35 no.6
• /
• pp.425-436
• /
• 2021

In this study, chemically enhanced steam cleaning(CESC) was applied as a novel and efficient method for the control of organic and inorganic fouling in ceramic membrane filtration. The constant filtration regression model and the resistance in series model(RISM) were used to investigate the membrane fouling mechanisms. For total filtration, the coefficient of determination(R²) with an approximate value of 1 was obtained in the intermediate blocking model which is considered as the dominant contamination mechanism. In addition, most of the coefficient values showed similar values and this means that the complex fouling was formed during the filtration period. In the RISM, R _c/R _f increased about 4.37 times in chemically enhanced steam cleaning compared to physical backwashing, which implies that the internal fouling resistance was converted to cake layer resistance, so that the membrane fouling hardly to be removed by physical backwashing could be efficiently removed by chemically enhanced steam cleaning. The results of flux recovery rate showed that high-temperature steam may loosen the structure of the membrane cake layer due to the increase in diffusivity and solubility of chemicals and finally enhance the cleaning effect. As a consequence, it is expected that chemically enhanced steam cleaning can drastically improve the efficiency of membrane filtration process when the characteristics of the foulant are identified.