• Membrane and Water Treatment
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• 제1권4호
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• pp.297-316
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• 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.

• 상하수도학회지
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• 제35권3호
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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.

• 상하수도학회지
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• 제23권1호
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• pp.121-128
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• 2009

Objectives of this study were to investigate influencing factors of detention time, particle size distribution, and filter medium characteristics for waterworks sludge dewatering. The stepped pressure filtration was carried out with lab scale apparatus and the filter press pilot test for dewatering was conducted at the water treatment plant. Effects of filter medium and polymer dose were examined through observing water content and dewatering velocity and cyclic dewatering rate with filter press pilot test. Relationships among detention time, particle size distribution and filtration resistance were analyzed. Prolongation of sludge detention time was found to cause blinding phenomenon in cake and filter medium and to decrease dewatering process efficiency. The average specific resistance increased according to detention time. In pilot test of dewatering for thickened sludge with Nylon Multi-NY840D and Nylon Mono-100% filter media, dewatering velocities were 0.92 and $0.93kg\;DS/m^2{\cdot}hr$ according to 0.1% polymer dose of dried solids weight base. And cyclic dewatering rates were 2.45 and $2.50kg\;DS/m^2{\cdot}cycle$ cycle for the Nylon Multi-NY840D and Nylon Mono-100% media. Dewatering velocity of polymer dosed sludge was observed to be higher than that of non-polymer sludge.

• 한국물환경학회지
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• 제20권4호
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• pp.370-375
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• 2004

Synthetic organic polyelectrolytes can be used to condition sludges to enhance their dewaterability. When conditioning biological sludges, the charge on the polymer has a significant impact on the effectiveness of the polymer as a conditioner. The objectives of this investigation were to determine the most effective type and dosage of polymer for conditioning digested sludge prior to dewatering, and to investigate the relationship between dewaterability and particle size. 3 types of digested sludge were used under the different digestion processes like anaerobic digestion, aerobic digestion and intermittent aerobic digestion. CST(capillary suction time), TTF(time-to-filter) and SRF(specific resistance to filtration) were tested as a dewaterability index and the number of particle distribution was analyzed using particle size analyzer. The results indicate that cationic polymer appears to be required for effective conditioning of these 3 types digested sludge and the optimal polymer dosage is about 0.6% of SS. CST and TTF are well correlated with mean particle diameter of which the dimension order is 1.7.

• 한국산학기술학회논문지
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• 제8권4호
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• pp.874-880
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• 2007

CST와 SRF는 슬러지 탈수효율 인자로 가장 널리 사용되고 있다. 이러한 CST와 SRF는 각각의 분석특징의 장.단점으로 인해 실험방법 및 결과 해석시, 슬러지 탈수의 최적조건을 찾아 예측하는데 어려움이 있다. 따라서 본 연구는 탈수성 지표로 이용되는 CST와 SRF의 이론식 가운데 CST와 SRF의 상호관계식을 유도하여 각각의 실측값과 예측값을 비교한 후 비교적 측정이 간편한 CST 시험만으로도 탈수최적조건을 도출할 수 있는 이론식을 검토하였다.

• 대한환경공학회지
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• 제27권12호
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• pp.1305-1310
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• 2005

하상여과에서 집수관의 최적 설계를 위한 방편으로 여러 개의 모래통을 이용하여 모형 집수관 실험을 수행하였다. 집수정의 수위, 집수관의 직경, 집수관의 길이, 그리고 모래의 투수계수를 변화시키면서 모형 집수관을 운영하였으며, 집수관 표면에서의 잔류 수두와 집수관 각 부위에서의 여과수 유입율, 그리고 집수정에서의 산출유량을 측정하였다. 실험결과 모래층에서의 저항에 비해 집수관에서의 저항이 작아서 집수관 표면에서의 잔류수두가 수평에 가까운 경우 효율적인 집수관임을 알 수 있었다. 집수관의 여과수 유입율은 집수정에 근접할수록 지수함수적으로 증가하였고, 집수관의 직경이 작을수록 그리고, 대수층의 투수계수가 클수록 이 지수함수의 기울기는 증가하였다. 집수관의 길이와 직경이 증가하면 산출유량은 증가하지만 그 한계생산성은 감소하였다. 효율적인 하상여과를 위해서는 집수관에서의 축방향 유속을 줄이는 것이 중요함을 알 수 있었으며, 본 연구의 조건에서는 이 유속이 1 m/sec를 넘을 경우 우물의 효율이 크게 감소함을 알 수 있었다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.18.2-18.2
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• 2009

Ceramics have some properties that are unmatched by other kind of materials like metals or polymers. The ability of high thermal and chemical resistance and in case of being superior in specific mechanical properties makes the ceramic materials suitable for arange of applications. The microstructure and morphology of a material arguably permit the use of many advanced application otherwise difficult to achieve.Porous structures have some important applications in biomedical and environmental field. For human hard tissue reconstruction and augmentation procedure suitable biomaterials are used with a desirable porosity. A range of porous bioceramics were fabricated with tailored design to meet the demand of specific applications. Channeled and interconnected porosity was introduced in alumina, zirconia, and hydroxyapatite or tri calcium phosphate ceramics by different methods like multi-pass extrusion process, bubble formation in viscous slurry,slurry dripping in immiscible liquid, sponge replica method etc. The detailed microstructural and morphological investigations were carried out to establish the unique features of each method and the developed systems. For environmental filters the porous structures were also very important. We investigated a range of channeled and randomly porous silicon based ceramic composites to enhance the material stability and filtration efficiency by taking advantage of the material chemistry of the element. Detailed microstructural and mechanical characterizations were carried out for the fabricated porous filtration systems.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.498-507
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• 2008

The mixture of bentonite powder and water is generally used to maintain the stability of excavation surface during the construction of vertical cutoff walls. The filter cake on the sidewall surface is the result of filtration of slurry into the adjacent soil formation. The filter cake is believed to have a very low hydraulic conductivity compared to that of the cutoff wall. This paper evaluates hydraulic conductivities of bentonite filter cakes set up with three types of bentonites under various pressure levels. A modified fluid loss test was employed in this experiment. Theory of filtration process was reviewed to explain the procedure in the present experiment. Hydraulic conductivity of the filter cakes with consideration of the filter medium resistance was evaluated. The results of the experiment with two calculation methods and discussion are presented to show the efficiency of the modified fluid loss test.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1502-1511
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• 2008

The mixture of bentonite powder and water is generally used to maintain the stability of excavation surface during the construction of vertical cutoff walls. The filter cake on the sidewall surface is the result of filtration of slurry into the adjacent soil formation. The filter cake is believed to have a very low hydraulic conductivity compared to that of the cutoff wall. This paper evaluates hydraulic conductivities of bentonite filter cakes set up with three types of bentonites under various pressure levels. A modified fluid loss test was employed in this experiment. Theory of filtration process was reviewed to explain the procedure in the present experiment. Hydraulic conductivity of the filter cakes with consideration of the filter medium resistance was evaluated. The results of the experiment with two calculation methods and discussion are presented to show the efficiency of the modified fluid loss test.

• 한국패류학회지
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• 제22권2호
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• pp.151-155
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• 2006

Proportion of Tegillarca granosa surviving after 2-6 hrs air exposure with 12 hrs interval at $20^{\circ}C$ and $28^{\circ}C$ for 20 days showed 85-100%, 80-100%, respectively. The survival rate was somewhat lower at high temperature but not significant (p < 0.05). Subsequent exposures for 7-9 days showed survival rate of 8.0-24.1% at $20^{\circ}C$ and $28^{\circ}C$. Oxygen consumption rates and filtration rates were significantly higher for 4 to 6 hrs exposures, compared with the preceding exposures. On the other hand, at $28^{\circ}C$, oxygen consumption rates in adult granular ark for 6 hrs exposure during 20 days had significantly decreased. Filtration rates in study groups increased a little over extended period of exposure, compared with those in control groups, and were similar irrelevant to the time of exposure and size of experimental animals. It is concluded, in view of their viability and oxygen consumption rate during air exposure, that ark shells have quite a high resistance to air exposure with their limited range of responses.