• Membrane Journal
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• v.24 no.1
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• pp.39-49
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• 2014

The effects of pH and oxygen back-flushing were investigated in hybrid process of ceramic microfiltration and PES (polyethersulfone) beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As increasing pH, $R_f$ decreased and J increased. Finally the maximum $V_T$ could be acquired at pH 9. Treatment efficiencies of turbidity was almost same independent of pH. Treatment efficiency of dissolved organic matters (DOM) decreased as increasing pH. As results of comparing the oxygen and nitrogen back-flushing, $R_{f,180}$ at oxygen back-flushing was the lower than that at nitrogen back-flushing, and the dimensionless final permeate flux ($J_{180}/J_0$) by initial permeate flux ($J_0$) at oxygen back-flushing was maintained the higher than that at nitrogen back-flushing except 10 and 12 min of back-flushing period (FT). Treatment efficiency of turbidity at oxygen back-flushing was a little higher than that at nitrogen back-flushing. Treatment efficiency of the DOM at nitrogen back-flushing was the higher than that at oxygen back-flushing. Also, treatment efficiency of turbidity at saturated oxygen was similar with those of oxygen and nitrogen back-flushing, but the treatment efficiency of DOM was increased significantly because OH radical could be generated by reaction between saturated oxygen and photocatalyst.

• Membrane Journal
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• v.22 no.6
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• pp.441-449
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• 2012

Effect of humic acid (HA) with periodic nitrogen back-flushing was investigated in hybrid process of alumina microfiltration and photocatalyst for drinking water treatment. It was compared and investigated with the previous results of microfiltration water back-flushing or ultrafiltration nitrogen back-flushing in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As results, the trends of membrane fouling were different depending on nitrogen or water back-flushing, and depending on ultrafiltration or microfiltration made with the same material. Also, the nitrogen back-flushing using microfiltration was more effective membrane fouling inhibition than ultrafiltration, and the nitrogen back-flushing was more effective than water back-flushing using the same microfiltration membrane. Turbidity treatment efficiencies were almost constant independent of HA concentration, but HA treatment efficiency was the maximum at HA 10 mg/L. From this results, it was shown that the treated water HA quality increased as increasing HA concentration, but HA could be removed the most effectively by photocatalyst beads adsorption and photo-oxidation at HA 10 mg/L.

• Membrane Journal
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• v.23 no.4
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• pp.267-277
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• 2013

The effect of water back-flushing period (FT) and water back-flushing time (BT) was compared with the previous study of nitrogen back-flushing in viewpoints of resistance of membrane fouling ($R_f$), permeate flux (J), and total permeate volume ($V_T$) in hybrid process of tubular ceramic microfiltration and PES (polyethersulfone) beads loaded $TiO_2$ photocatalyst for advanced drinking water treatment. As FT decreasing, Rf decreased, but J and $V_T$ increased. Turdity treatment efficiency was the maximum at NBF (no back-flushing) and increased a little as FT decreasing in both water and nitrogen back-flushing. Organic matter treatment efficiency was the maximum at FT 4 min in water back-flushing, but increased as FT decreasing in nitrogen back-flushing. As BT increasing, Rf and resistance of reversible membrane fouling ($R_{rf}$) decreased, but J and $V_T$ increased. The turdity treatment efficiency was almost constant beyond 98% in water back-flushing, but increased as BT increasing except NBF in nitrogen. The organic matter treatment efficiency was the maximum at BT 6 sec in water back-flushing, but increased as BT increasing except NBF in nitrogen. The $V_T$ was the maximum at BT 30 and FT 2 min, and optimal condition was BT 30 sec per FT 2 min in this experimental range.

• Membrane Journal
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• v.23 no.2
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• pp.159-169
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• 2013

The effect of humic acid (HA), and the roles of microfiltration (MF), PES (polyethersulfone) beads adsorption, and photo-oxidation were investigated in hybrid process of ceramic MF and PES beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment. The results of water and nitrogen back-flushing were compared in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). Because membrane fouling increased dramatically as increasing HA, Rf increased and J decreased, and finally $V_T$ was the highest at 2 mg/L HA. Average turbidity treatment efficiencies were almost same independent of HA concentration. Average organic matter treatment efficiency was the minimum 71.4% at 10 mg/L HA in water back-flushing, but those were almost constant in nitrogen back-flushing. The hybrid process of MF, PES beads, and UV (MF + $TiO_2$ + UV) have the lowest $R_f$, and the highest J and $V_T$ in both water and nitrogen back-flushing. The turbidity and organic matter treatment efficiencies were the maximum at MF + $TiO_2$ + UV independent of water and nitrogen back-flushing, and decreased sequently as simplifying the process to MF. However, adsorption performed the more important role than photo-oxidation in water back-flushing, and photo- oxidation was the more than adsorption in nitrogen back-flushing.

• Membrane Journal
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• v.24 no.2
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• pp.123-135
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• 2014

The effects of pH, saturated oxygen, and back-flushing media were investigated in hybrid process of tubular ceramic microfiltration and $TiO_2$ photocatalyst-loaded PES (polyethersulfone) beads for advanced drinking water treatment, and compared results of water, nitrogen, or oxygen back-flushing in the viewpoints of membrane fouling resistance ($R_f$), permeate flux (J) and total treated water ($V_T$). $R_f$ decreased, and J and $V_T$ increased as decreasing pH. Turbidity treatment efficiencies were similar at water or nitrogen back-flushing independent of pH, but DOM (dissolved organic matter) treatment efficiency did not have a trend at water back-flushing. $R_f$ at NBF (no back-flushing) with SO (saturated oxygen) was the lower than that at NBF without SO. Also, the DOM treatment efficiency at NBF with SO was the lower than that at NBF without SO. It happened because OH radicals produced by reaction of SO and photocatalyst could dilute with water inside the module. The DOM treatment efficiency of gas back-flushing showed the larger than that of water back-flushing at back-flushig period 10 min. It proved that the adsorption or photo-oxidation of PES beads could be activated by the more effective bead-cleaning of gas back-flushing than water back-flushing.

• Membrane Journal
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• v.19 no.3
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• pp.194-202
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• 2009

In this study periodic water-back-flushing using permeate water was performed to minimize membrane fouling and to enhance permeate flux in advanced water treatment by tubular ceramic ultrafiltration membrane for Gongji stream in Chuncheon city. The back-flushing period (FT, filtration time) 2 min with periodic water-back-flushing of 15 sec showed the highest value of dimensionless permeate flux (permeate flux vs. initial permeate flux), and the lowest value of resistance of membrane fouling. Also in the results of BT effect at fixed FT 10 min, BT (back-flushing time) 20 sec showed the lowest value of resistance of membrane fouling and the highest value of dimensionless permeate flux, and we could be obtained the highest total permeate volume of 107.3 L. Consequently FT 10 min and BT 20 sec could be the optimal condition in Gongji stream water treatment, which was the exactly same results of our previous tubular alumina microfiltration. Then the average rejection rates of pollutants by our tubular ceramic UF system were 97.0% for turbidity, 32.1 % for chemical oxygen demand by manganese method, 28.8% for ammoniac nitrogen and 54.4% for T-P.

• Membrane Journal
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• v.12 no.1
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• pp.8-20
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• 2002

In this study using $N_2$-back flushing, which wwas not the general back-flushing method of membranes, the discharged wastewater from a paper plant was filtrated by 4 kinds of tubular carbon ceramic ultrafiltration membranes. We could in vestigate effects of $N_2$-back flushing period, transmembrane pressure (TMP)and flow rate and find optimal operating conditions. The $N_2$-back flushing time (BT) was fixed at 40 sec, filtration times (FT) were changed in 4~32 min, TNP in $1.0~3.0kg_f/cm^2$ the flow celocities in 0.53~1.09cm/s. The optimal conditions were discussed in the viewpoints of dimensionless permeate flux ($J/J_0$), toal permeate volume ($V_T$) and resistance of membrane fouling ($R_f$). Optimal back-flushing period was BT/FT=0.167 (FT=8 min ), in which more $V_T$ was obtained than that in BT/FT=0.083 (FT=4 min) which was the most friquent back-flushing condition. Then rising TMP should increase the driving force, and more $V_T$ could be accumulated. And rising flow rate should decrease membrane fouling increase permeate flux, and more $V_T$could be produced. Average rejection rates of pollutants were higher than 95% for turbidity and 45~83% for $COD_{Cr}$, but rejection rates of total dissolved solid (TDS) were lower than 10%.

• Membrane Journal
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• v.23 no.1
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• pp.70-79
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• 2013

The $N_2$ back-flushing period (FT) and time (BT) were investigated in hybrid process of ceramic microfiltration and PES (polyethersulfone) beads loaded with titanium dioxide ($TiO_2$) photocatalyst for advanced drinking water treatment in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). As decreasing FT and increasing BT, $R_f$ decreased and J increased, and finally the maximum $V_T$ could be acquired at FT 10 min and BT 30 sec. In FT effect experiment, treatment efficiencies of turbidity and dissolved organic matters (DOM) were the highest at no back-flushing (NBF) because of dramatic membrane fouling. As result of BT effect, the treatment efficiencies were the maximum at BT 30 sec, which was different with the FT result. Because the photocatalyst beads could be cleaned effectively as decreasing FT and increasing BT, turbidity treatment efficiency increased a little from 95.4% to 97.5% as decreasing FT, and from 95.9% to 98.5% as increasing BT. Also DOM treatment efficiency increased from 70.8% to 80.6% as decreasing FT, and from 75.1% to 85.8% as increasing BT. The optimal condition, where the treatment efficiencies and $V_T$ were the maximum, should be FT 10 min and BT 30 sec in our experimental range.

• Membrane Journal
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• v.8 no.2
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• pp.102-108
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• 1998

Permeation behavior of the semiconductor rinsing wastewater containing Si particles was examined by ultrafiltration using the polysulfone plate membrane. The permeation flux was gradually decreased with time. It was due to the growth of cake deposited on the membrane surface and the pore plugging by Si particles. Permeation flux of cross flow type was 1.4 times higher than that of the dead end flow type. Nitrogen back flushing which is the removing method of membrane fouling was superior to the water sweeping. With nitrogen back flushing, the decrease of permeation flux due to the fouling was recovered about 85 % to the initial flux in the flat plate membrane system. The rejection rate of Si particles was about 90 % and the size of Si particle in the permeate was about 70 nm.

• Membrane Journal
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• v.23 no.3
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• pp.226-236
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• 2013

The effect of $N_2$ back-flushing period (FT) and time (BT) was compared with the previous result used PES (polyethersulfone) beads loaded with titanium dioxide photocatalyst in hybrid process of alumina microfiltration and PP (polypropylene) beads coated with photocatalyst in viewpoints of membrane fouling resistance ($R_f$), permeate flux (J), and total permeate volume ($V_T$). The reason of nitrogen back-washing instead of the general air back-washing method is to minimize the possible effect of oxygen included in air on water quality analysis. As decreasing FT, $R_f$ decreased and J and $V_T$ increased. Treatment efficiency of dissolved organic matters (DOM) was 82.0%, which was the higher than 78.0% of the PES beads result. This means that PP beads coated with photocatalyst was the more effective than PES beads loaded with photo-catalyst in the DOM removal. As increasing BT, the final $R_f$ decreased and the final J increased, but $V_T$ was the maximum at BT 15 sec. The average treatment efficiency of turbidity did not have any trend as changing BT. As BT increasing from 6 sec to 30 sec, the treatment efficiency of DOM increased 11.8%, which was a little higher than the result of PES beads.