• Membrane Journal
• /
• v.29 no.3
• /
• pp.147-154
• /
• 2019

The permeate flux increments of a natural convection instability flow (NCIF) caused by the change of inclined angles ($0{\sim}180^{\circ}$) to gravity of the commercial membrane module were tested in the dead-end membrane filtration of BSA protein solution. The NCIF are more generated as the inclined angle increased from $0^{\circ}$ to $180^{\circ}$, and the occurred NCIF enhances permeate flux. However, the commercial module can only generate NCIF by completely removing the air gap in module. Since the custom design module designed in this study is permeated in a crossward direction ($90^{\circ}$), NCIF is always generated even if there is the air gap in module. The results of membrane filtration of BSA and dextran solutions using a custom design module showed that the flux in the crossward direction is increased to about 3.8 times for BSA solution and 1.8 times for dextran solution after two hours of operation due to the occurrence of NCIF. Also, NCIF generation is continued during 20 hours filtration of BSA solution, increasing the permeate flux to about 7.5 times. Since the custom design module with a permeation in the crossward direction and NCIF is always generated within the module, so it is possible to expect an increase in permeate flux due to the suppression of fouling formation, and thus to be utilized as a superb dead-end membrane module.

• Membrane and Water Treatment
• /
• v.8 no.2
• /
• pp.113-123
• /
• 2017

This study investigated effects of physical and chemical cleaning methods on the initial flux recovery of fouled membrane in membrane distillation process. A laboratory scale direct contact membrane distillation (DCMD) experiment was performed to treat digested livestock wastewater with 3.89 mg/L suspended solids, 874.7 mg/L COD, 543.7 mg/L nitrogen, 15.6 mg/L total phosphorus, and pH of 8.6. A hydrophobic PVDF membrane with an average pore size of $0.22{\mu}m$ and a porosity of 75 % was installed inside a direct contact type membrane distillation module. The temperature difference between feed and permeate side was maintained at $40^{\circ}C$ with the feed and permeate stream velocity of 0.18 m/s. The results showed that the permeate flux decreased from $22.1L{\cdot}m^{-2}{\cdot}hr^{-1}$ to $19.0L{\cdot}m^{-2}{\cdot}hr^{-1}$ after 75 hours of distillation. The fouled membrane was cleaned first by physical flushing and consecutively by chemicals with NaOCl and citric acid. After the physical cleaning the flux was recovered to 92 % as compared with the initial clean water flux of the virgin membrane. Then 94 % of the flux was recovered after cleaning by 2,000 ppm NaOCl for 90 minutes and finally 97 % of flux recovered after 3 % citric acid for 90 minutes. SEM-EDS and FT-IR analysis results presented that the foulants on the membrane surface were removed effectively after each cleaning step. The contact angle measurement showed that the hydrophobicity of the membrane surface was also restored gradually after each cleaning step to reach nearly the same hydrophobicity level as the virgin membrane.

• Membrane Journal
• /
• v.25 no.1
• /
• pp.7-14
• /
• 2015

In this study transmembrane pressure (TMP) was measured with respect to operational time in order to estimate fouling of the submerged membrane in the membrane bioreactor(MBR). The microfiltration flat sheet module which has $0.02m^2$ of effective area and $0.15{\mu}m$ nominal pore size was submerged in the activated sludge solution of MLSS 5,000 mg/L. The permeate experiments were carried out simultaneously to compare TMP of the run/stop (R/S) with that of the sinusoidal flux continuous operation (SFCO). TMP for SFCO mode was up to 93% lower than that of R/S mode, and the effect of TMP drop reduced as permeate flux increased. Also, TMP of the SCFO mode was maintained below 40% of the limited operating TMP 55 kPa until the permeate operational time extended to longer than 5 times for the case as the coagulant $FeCl_3$ was dosed into the activated sludge solution with 500 mg/L concentration.

• Applied Chemistry for Engineering
• /
• v.22 no.6
• /
• pp.703-710
• /
• 2011

As the spacer in the membrane module provide the channel space to flow the feed solution smoothly and induce the flow turbulence, it could help to reduce both the concentration polarization and to take the long-term operation of membrane modules with high permeate flux by mixing the accumulated contaminants on the membrane surface into the bulk solution. In this study, the concentration distribution in membrane module with respect to the spacers which have the cross-sectional shapes of circle, cross, diamond and hexagon, the angles of spacer configuration, solute rejection and permeate flux were interpreted and optimized numerically using the "COMSOL Multiphysics" software. The concentration on the membrane surface was kept the lowest level for the cross-shape among the above four types of spacers. Also the 30 degree spacer configuration was showed as the most efficient case. The concentrations on the membrane surface at the module outlet for without spacer and the cross shape with the 30 degree spacer configuration were 2.09 and 1.29 times higher than those at inlet, respectively. The reduction effect of concentration polarization increased rapidly as the permeate flux increased.

• Membrane and Water Treatment
• /
• v.2 no.1
• /
• pp.63-74
• /
• 2011

A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.17 no.1
• /
• pp.13-19
• /
• 2014

The feed temperature has an effect on the performance during desalination of seawater by membrane separation. When the permeate flux intends to increase using the waste heat, it is necessary to analyze the effect of feed temperature precisely on the membrane performance. The experiments were carried out to investigate the performance of membranes by varying the seawater temperature from $10^{\circ}C$ to $60^{\circ}C$. The increase of permeate flux with increase of feed temperature was interpreted as the change of water viscosity and the membrane itself. While the increase of permeate flux could be predicted by the viscosity change in case of nanoflitration membrane, there exists 30% difference between the experiment data and the prediction by the viscosity change in case of reverse osmosis (RO) membrane, which seems to be due to 8% decrease of the pore size in 60caused by the contraction of membrane with the increase of temperature. Therefore, the desalination of seawater should be carried out within the range that the elevation of temperature does not cause the alteration of membrane itself even for the purpose of increasing the permeate flux.

• 한국생물공학회:학술대회논문집
• /
• 2002.04a
• /
• pp.145-148
• /
• 2002

Membrane bioreactors for wastewater treatment must operate for long periods without chemical cleaning. This study investigates the critical flux concept introduced by Field et al. as a means for achieving this goal. We conducted two series of tests: at fixed transmembrane pressure(TMP) and at fixed permeate flux. set by a volumetric pump on the permeate. Comparison of constant pressure and constants flux tests under same conditions showed that the critical flux is almost identical to the limiting or pressure independent flux obtained in constant pressure. More generally, constant flux procedure below the critical flux avoids overfouling of the membrane in the initial stage and is more advantageous for membrane bioreactor operation.

• Journal of Environmental Science International
• /
• v.7 no.2
• /
• pp.209-216
• /
• 1998

Nanofiltration[NF45] and reverse osmosis membrane(HR98PP) separation treatment of dyestuff wastewater was carried out In order to separate relatively pure water from synthetic dyestuff wastewater, which consists of reactive dye, acid dye, basic dye, direct dye, and disperse dye. The experiments were performed by using the plate and frame membrane module. In the nanofiltration and reverse osmosis membrane separation, When the NaCl concentration was 0.1, 5.0, and 20.091, retention was 63.0, 46.0, 0.9%, respectively. When permeate flux was 125.0, 67.5, and 45.0 L/$m^2$ h, the osmotic pressure increased with Increasing the NaCl concentration. Permeate flux of two membranes Increased as temperature Increased due to segmental movement of polymer of the membrane and the rejection rate of dyestuff was decreased gradually. It was found that the rejection rate was about 95% in the nanofiltratlon, while the reverse osmosis membrane showed a high rejection rate of 99% under all temperature and pressures conditions.

• Korean Membrane Journal
• /
• v.9 no.1
• /
• pp.12-17
• /
• 2007

We performed periodic water-back-flushing using permeate water to minimize membrane fouling to enhance permeate flux in tubular ceramic microfiltration system for water treatment of high turbid source. The filtration time (FT) = 2 min with periodic 6 sec water-back-flushing showed the highest value of dimensionless permeate flux ($J/J_o$), and the lowest value of resistance of membrane fouling ($R_f$), and we acquired the highest total permeate volume $(V_T)\;=\;6.805L$. Also in the result of BT effect at fixed FT = 10 min and BT (back-flushing time) = 20 sec showed the lowest value of $R_f$ and the highest value of $J/J_o$, and we could obtain the highest $V_T\;=\;6.660\;L$. Consequently, FT = 2 min and BT = 6 sec could be the optimal condition in water treatment of high turbid source above 10 NTU. However, FT = 10 min and BT = 20 sec was superior to reduce operating costs because of lower back-flushing frequency. Then the average quality of water treated by our tubular ceramic MF system was turbidity of 0.07 NTU, $COD_{Mn}$ of 1.86 mg/L and $NH_3-N$ of 0.007 mg/L.

• Korean Membrane Journal
• /
• v.10 no.1
• /
• pp.33-38
• /
• 2008

In this study periodic water-back-flushing using permeate water was performed to minimize membrane fouling and to enhance permeate flux in tubular ceramic micro filtration system for Gongji stream water treatment in Chuncheon city. The filtration time (FT) 2 min with periodic 6 sec water-back-flushing showed the highest value of dimensionless permeate flux ($J/J_0$), and the lowest value of resistance of membrane fouling ($R_f$), and we acquired the highest total permeate volume ($V_T$) of 7.44L. Also in the results of BT effect at fixed FT 10 min, BT (back-flushing time) 20 sec showed the lowest value of $R_f$ and the highest value of $J/J_0$, and we could be obtained the highest $V_T$ of 8.04 L. Consequently FT 10 min and BT 20 sec could be the optimal condition in Gongji stream water treatment. Then the average rejection rates of pollutants by our tubular ceramic MF system were 93.8% for Turbidity, 20.7% for $COD_{Mn}$, 39.2% for $NH_3$-N and 31.5% for T-P.