• Membrane Journal
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• v.14 no.1
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• pp.66-74
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• 2004

Total resistance of membrane in a micro-filtration system using a metal membrane was mainly attributed to the permeate resistance of cake layer($R_c$), which was formed by deposited particles from the physico-chemical interactions of solids on membrane surface. Intermittent back ozonation was highly effective than the air backwashing for fouling reduction. As far the operational effect, under same ozone injection, the increase of gas flow-rate was more favorable than the increase of injection time far the recovery of permeation flux. As the filtration time was longer, the effect of flux recovery by intermittent back-ozonation decreased. Therefore, it is preferable to operate membrane cleaning before the foulant is consolidated on membrane surface.

• Journal of the Korean Geotechnical Society
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• v.27 no.2
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• pp.53-62
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• 2011

During the construction of vertical cutoff walls, filtration of bentonite slurry into the adjacent soil formation fabricates a layer of bentonite filter cake on the wall surface. The bentonite filter cake possesses much lower hydraulic conductivity compared to that of backfill materials in the cutoff wall. Hydraulic conductivity of bentonite filter cakes formed with three different types of bentonites has been measured by performing the modified fluid loss test under various pressure levels. Three different mixture ratios, 4, 6, and 8%, were selected for fabricating bentonite filter cakes to represent common field conditions. Two analysis methods for interpreting the experimental data from the modified fluid loss tests were employed to estimate hydraulic conductivity of the bentonite cakes. The range of hydraulic conductivities of the three bentonite cakes is between $2.15{\times}10^{-11}\;m/s$ and $2.88{\times}10^{-10}\;m/s$ which is 1 to 2.7 orders of magnitude lower than that of the design cutoff wall backfill. The stress distribution and thickness of the bentonite cakes were also evaluated in this paper.

• Membrane Journal
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• v.15 no.1
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• pp.52-61
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• 2005

Permeate flux decline in a microfiltration was analyzed by measuring the permeability of bentonite colloidal solution through polyethylene capillary membranes. The flux decline with time was due to the growth of cake layer on the membrane surface and to the pore blocking by particles. As the time approaches to steady state, the permeate flux is almost controlled by the cake filtration model. Faster flux decline at high trans-membrane pressure was attributed to the formation of denser packed cake layer and pore blocking. The ratio of permeate flux to the initial permeate flux, J/J₁, decreased with increasing the trans-membrane pressure, from 45% for 0.5 kg/sub f//㎠ to 38% for 2.0 kg/sub f//㎠. In comparing the ratio of each fouling component to the total fouling for the 0.5 kg/sub f//㎠ TMP condition, complete blocking was 23.4%, standard blocking was about 14.6% and cake filtration was 62.0%, respectively. Permeate flux through the membrane increases with cross flow velocity, and the effect of the variation of velocity is more significant at 1.0 kg/sub f//㎠ rather than at 2.0 kg/sub f//㎠ of the operation pressure. Permeate flux for the membrane having the average pore diameter of 0.34 ㎛ was higher than that for the membrane of 0.24 ㎛ pore size, with the higher flux with the low concentration of feed. On the operation using the membrane of 0.34 ㎛ pore, the pore blocking in the low concentration of 200 ppm is negligible relative to the pore blocking in the 1000 ppm feed.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.681-689
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• 2011

Submerged membrane bio-reactor (SMBR) has several advantages such as high MLSS, long SRT, and low F/M ratio at wastewater treatment. So, this has widely applied over the world and many studies have been conducted. However, membrane fouling remains an inevitable problem. This study was investigated using bench-scale SMBR with three poeration modes. Raw waters were prepared by addition of starch, acetic and fibric acid to recovery water of zeolite. The efficiency of nitrification and COD were very stable as about 95% and 80%, respectively. And critical flux was 128.8L/$m^{2}$/hr. The result of biodegradability test was following values at the each mode : Ss+Xs/$C_{T}$=81.7%, 35.1% and 45.3%, $X_{I}+S_{I}/C_{T}=18.3%$, 64.9% and 54.7%. When particulate matters such as $X_{I}$ and $X_{S}$ in influent are increased, membrane fouling will take place more and more. A relative ratio of filtration resistance to the fouling occurred by the cake layer was increased when increased the portion of $X_{I}$ and polysaccharide. It was thought that the formation of cake layer was promoted due to bond between $X_{I}$ and vicid material s generated from the polysaccharide.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.3
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• pp.197-204
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• 2021

In MBR, extracellular polymeric substance (EPS) is known as an important factor of fouling; soluble EPS (sEPS) affects internal contamination of membrane, and bound EPS (bEPS) affects the formation of the cake layer. The production of EPS changes according to the composition of influent, which affects fouling characteristics. Therefore, in this study, the effects of the F/M ratio on the sEPS concentration, bEPS content, and fouling were evaluated. The effects of F/M ratio on the amount and composition of EPS were confirmed by setting conditions that were very low or higher than the general F/M ratio of MBR, and the fouling occurrence characteristics were evaluated by filtration resistance distribution. As a result, it was found that the sEPS increased significantly with the increase of the F/M ratio. When the substrate was depleted, bEPS content decreased because bEPS was hydrolyzed into BAP and seemed to be used as a substrate. In contrast, when the substrate is sufficient, UAP (utilization-associated products) was rapidly generated in proportion with the consumption of the substrate. UAP has a relatively higher Protein/Carbohydrate ratio (P/C ratio) than BAP, and this means, it has a higher adhesive force to the membrane surface. As a result, UAP seems like causing fouling rather than BAP (biomass-associated products). Therefore, R_f (Resistance of internal contamination) increased rapidly with the increase of UAP, and R_c (Resistance of cake layer) increased with the accumulation of bEPS in proportion, and as a result, the fouling interval was shortened. According to this study, a high F/M ratio leads to an increment in UAP generation and accumulation of bEPS, and by these UAP and bEPS, membrane fouling is promoted.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.501-510
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• 2017

In this study, it is estimated that ceramic membrane process which can operate stably in harsh conditions replacing existing organic membrane connected with coagulation, sedimentation etc.. Jar-test was conducted by using artificial raw water containing kaolin and humic acid. It was observed that coagulant (A-PAC, 10.6%) 4mg/l is the optimal dose. As a results of evaluation of membrane single filtration process (A), coagulation-membrane filtration process (B) and coagulation-sedimentation-membrane filtration process (C), TMP variation is stable regardless of in Flux $2m^3/m^2{\cdot}day$. But in Flux $5m^3/m^2{\cdot}day$, it show change of 1-89.3 kpa by process. TMP of process (B) and (C) is increased 11.8, 0.6 kpa each. But, the (A) showed the greatest change of TMP. When evaluate (A) and (C) in Flux $10m^3/m^2{\cdot}day$, TMP of (A) stopped operation being exceeded 120 kpa in 20 minutes. On the other hand, TMP of (C) is increased only 3 kpa in 120 minutes. Through this, membrane filtration process can be operated stably by using the linkage between the pretreatment process and the ceramic membrane filtration process. Turbidity of treated water remained under 0.1 NTU regardless of flux condition and DOC and $UV_{254}$ showed a removal rate of 65-85%, 95% more each at process connected with pretreatment. Physical cleaning was carried out using water and air of 500kpa to show the recovery of pollutants formed on membrane surface by filtration. In (A) process, TMP has increased rapidly and decreased the recovery by physical cleaning as the flux rises. This means that contamination on membrane surface is irreversible fouling difficult to recover by using physical cleaning. Process (B) and (C) are observed high recovery rate of 60% more in high flux and especially recovery rate of process (B) is the highest at 95.8%. This can be judged that the coagulation flocs in the raw water formed cake layer with irreversible fouling and are favorable to physical cleaning. As a result of estimation, observe that ceramic membrane filtration connected with pretreatment improves efficiency of filtration and recovery rate of physical cleaning. And ceramic membrane which is possible to operate in the higher flux than organic membrane can be reduce the area of water purification facilities and secure a stable quantity of water by connecting the ceramic membrane with pretreatment process.

• Membrane Journal
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• v.22 no.6
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• pp.450-460
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• 2012

In the submerged membrane-coupled sequencing batch reactor (MSBR) with sponge type media, the effect of media on the removal efficiency and filtration performance were investigated. Dosages of the media in the MSBR were set of 5%, 10%, and 20% based on working volume of reactor. As a control system, the MSBR without media was also operated. The experimental results showed that there was also no difference observed in the removal efficiencies of COD, T-N, and T-P irrespective of the dosages of the media. But TMP (transmembrane pressure) of the MSBR with media increased slowly during the operation time, while that of the MSBR without media increased rapidly at the initial operation. This result was thought that the collisions between flat membrane and moving media gave shear forces which decreased the cake layer on the surface of flat type membrane. Consequently, this study showed that filtration performance of the MSBR with media was greatly enhanced compared with that of the MSBR without media. The MSBR with media suggested in this study can be a good candidate for the wastewater treatment.

• Korean Chemical Engineering Research
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• v.58 no.1
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• pp.84-91
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• 2020

The efficiency of the synthetic magnesium silicate used in basic polyols and edible oil purification is evaluated by its purification ability and filtration rate and is affected by the particle size and surface area of magnesium silicate. In this study, it was investigated the change on the particle size of magnesium silicate was influenced by the reaction temperature, injection rate, injection order (Si, Mg) and Mg/Si reaction mole ratio. The synthesized magnesium silicate was compared and analyzed for the synthesis, grinding, and refining processes. In the synthesis process, the reaction temperature and feed rate did not affect the average particle size change of magnesium silicate, while the reaction molar ratio of Mg / Si and the order of injection acted as main factors for the change of average particle size. The average particle size of magnesium silicate increased by 8.7 ㎛ from 54.4 ㎛ to 63.1 ㎛ at Mg injection when Mg molar ratio increased from 0.125 to 0.500, and increased by about 4.8 ㎛ from 47.3 ㎛ to 52.1 ㎛ at Si injection. The average particle size according to the order of injection was 59.1 ㎛ for Mg injection and 48.4 ㎛ for Si injection and the difference was shown 10.7 ㎛, therefore the filtration rate was about 2 times faster under the condition of Mg injection. That is, as the particle size increases, the filtration time is shortened and washing filtration rate can be increased to improve the productivity of magnesium silicate. The cake form of separated magnesium silicate after filtration becomes a solid through drying process and is used as powdery adsorbent through the grinding process. As the physical strength of the dried magnesium silicate increased, the average particle size of the powder increased and it was confirmed that this strength was affected by the reaction molar ratio. As the reaction molar ratio of Mg / Si increased, the physical strength of magnesium silicate decreased and the average particle size after grinding decreased by about 40% compared to the average particle size after synthesis. This reduction of strength resulted in an improvement of the refining ability due to the decrease of the average particle size and the increase of the amount of fine particle after the pulverization, but it resulted in the decrease of the purification filtration rate. While the molar ratio of Mg/Si was increased from 0.125 to 0.5 at Mg injection, the refining ability increased about 1.3 times, but the purification filtration rate decreased about 1.5 times. Therefore, in order to improve the productivity of magnesium silicate, the reaction molar ratio of Mg / Si should be increased, but in order to increase the purification filtration rate of the polyol, the reaction molar ratio should be decreased. In the synthesis parameters of magnesium silicate, the order of injection and the reaction molar ratio of Mg / Si are important factors affecting the changes in average particle size after synthesis and the changes of particle size after grinding due to the changes of compressive strength, therefore the synthetic parameter is an important thing that determines productivity and refining capacity.

• Journal of Korean Society on Water Environment
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• v.20 no.4
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• pp.346-351
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• 2004

Because of being produced a great deal of excess sludges from biological wastewater treatment process, the subject regarding treatment and disposal of them has been significantly handled in real plants. It should be considered the alternative treatment with easy operating and cost effective process in rural areas. For the thickening of wasted activated sludge from small scale wastewater treatment facilities, thus, the provisional sludge thickening system was developed by the application of mesh filter module. Three meshes with different pore size(100, 150, $200{\mu}m$) were prepared for filter modules that were used to withdraw effluent from thickening system. A filter module with $100{\mu}m$ mesh was chosen as the most effective thickening material in the viewpoint of volume reduction and effluent quality: the volume reductions of initially injected sludge with 3,600 mg/L and 9,100 mg/L were 95% and 85%, respectively, and the filtered effluents were enough good to be shown below 1.0 mg/L of SS and 1.0 NTU of turbidity. Since the filtration of thickening was influenced by the cake layer formed on mesh filter module and this system was operated in the combination of sludge thickening with gravity settling, the filter modules with smaller pore size and the larger floc size were required for long term operation safely.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.407-426
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• 2008

The bentonite slurry has been used as the stabilize suspension for wet process bored pile construction in Thailand. The bentonite suspension has benefit on filtration in the sand layer, but it creates thick cake film along pile shaft and loose sedimentation at pile toe. The base grouting technique was widely used to rectify the soft base or loose sedimentation problem of bored pile. The base grouting technique was not increased only end bearing capacity, but was also more increase in skin friction capacity of the bored piles. The comprehensive researches on base grouting was carried out by installing PVC casing inside the shaft to allow the drilling through the pile base in order to collect the soil sample below the pile tip. The polymer based slurry recently was used to replace the bentonite slurry to overcome the thick cake film along pile shaft as well as loose sedimentation at pile toe. The extent research on polymer slurry by physical model was performed to verify the real behavior of polymer. The appropriate mixing ratio of polymer was proposed. The design skin friction coefficient, $\beta$ and end bearing coefficient, Nq, for sand layer base on fully instrumented tested pile were proposed. The application on remedial of the lose capacity bored pile with large displacement in Bangladesh was proposed and discussed.