- Email: [email protected]
ultrafiltration process
Desalination 200 (2006) 421–423
Removal of natural organic matter from water by in-line coagulation/ultrafiltration process Malgorzata Kabsch-Korbutowicz Wroclaw University of Technology, Institute of Environment Protection Engineering, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland Tel. +48 71 3203639; Fax +48 71 3282980; email: [email protected] Received 29 October 2005; accepted 4 March 2006
1. Introduction The use of ultrafiltration for treatment of water is nowadays growing rapidly. However, the economic use of membrane filtration systems is often limited by fouling, which increases applied pressure drops and cleaning frequencies, and the associated decrease in removal efficiency is observed. Currently, the most common method of preventing fouling is by pretreating the influent to the membrane process with the application of conventional unit processes. A variety of pretreatment processes for UF have been investigated including coagulation, activated carbon adsorption, adsorption on iron oxides or other pre-formed settleable solid phases, or ozonation. Coagulation, as a pretreatment process, can substantially reduce the concentration of natural organic substances found in raw water; thus, it can decrease the membrane potential for fouling and enhance membrane rejection. Common modes of coagulation realization include ordinary coagulation, where the coagulation and sedimentation steps are carried out in separate tanks ahead of the membrane. However, for small membrane systems such complex water treatment train is not advisable and many works
are going on for simplification of membranebased waterworks. One of the solutions is application of in-line coagulation. The term “in-line coagulation” is used to describe the use of a coagulation before membrane filtration, without a sedimentation or pre-filtration step [1,2]. The objective of the study was to investigate the influence of pre-coagulation with three types of aluminum-based coagulants realized as an in-line process with ultrafiltration on the effectiveness of natural organic matter (NOM) elimination and membrane fouling. The influence of coagulant type, its dose and membrane type on membrane fouling, and NOM elimination was analyzed.
2. Materials and methods Experiments were carried out on a model solution prepared from natural water flowing out from The Great Batorow Peatbag (southwest Poland) and dechlorinated tap water. The concentration of organic matter, expressed as UV 254 absorbance amounted to 0.425 cm–1. pH of the water was equal to 7.7. Three aluminum-based coagulants, i.e. alum (Al2(SO4)3),
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2006.03.389
422
M. Kabsch-Korbutowicz / Desalination 200 (2006) 421–423 100
100
PES30 membrane
80 R abs 254 nm, %
R abs 254 nm, %
80
C30 membrane
60 40 20
60 40 20
0
0 0
d1
d2
d3
0
Coagulant dose, g Al m–3 Al2(SO4)3
d1
d2
d3
Coagulant dose, g Al m–3 PAC 10WA
NaAlO2
Fig. 1. Effect of coagulant type and its dose on natural organic matter (NOM) efficiency removal in the in-line coagulation/ultrafiltration process for polyethersulfone (PES) and regenerated cellulose (C) membranes (d1 = 1.79 g Al m–3, d2 = 2.87 g Al m–3, d3 = 3.59 g Al m–3).
NaAlO2 and polyaluminum chloride (PAC 10WA) have been applied. The coagulation was carried out at Al doses equal to 1.79, 2.87 and 3.59 g Al m–3. The samples were stirred rapidly for 3 min, which was followed by 20 min slow mixing. Then the solution (with flocs of hydrolyzed coagulants) underwent an ultrafiltration process. In this study, Millipore ultrafiltration 1.0
membranes of cutoff = 30 kDa made of polyethersulfone (PES) and regenerated cellulose (C) were used. The operating pressure was 0.1 MPa. 3. Results and discussion Fig. 1 shows the effects of coagulant type and its dose on the removal of UV absorbance 1.0
PES30 membrane
0.8
C30 membrane
0.8
0.6
0.6 J/J0
J/J0 0.4
0.4
0.2
0.2
0.0
0.0 0
d1
d2
d3
0
Coagulant dose, g Al m–3 Al2(SO4)3
d1
d2
d3
Coagulant dose, g Al m–3 PAC 10WA
NaAlO2
Fig. 2. The influence of coagulant type and its dose on flux decline in the in-line coagulation/ultrafiltration process for polyethersulfone (PES) and regenerated cellulose (C) membranes (d1 = 1.79 g Al m–3, d2 = 2.87 g Al m–3, d3 = 3.59 g Al m–3).
M. Kabsch-Korbutowicz / Desalination 200 (2006) 421–423
(abs 254). As can be inferred from the presented results, the application of alum or polyaluminum chloride resulted in the increase of organic matter elimination, while the use of sodium aluminate did not affect the separation of organic substances. The experimental results obtained during ultrafiltration of water-containing NOM through C and PES membranes (Fig. 2) showed that application of in-line coagulation considerably reduced membrane fouling.
process might be a good solution to the problem of small membrane-based water treatment plant operations. Acknowledgement The work was partly supported by Polish Ministry of Education and Science, Grant # 3 T09D 014 29 (years 2005–2007). References [1]
4. Conclusions Application of in-line coagulation/ultrafiltration process with the use of alum or polyaluminum chloride resulted in improved removal of NOM from treated water and reduced membrane fouling. It seems that the investigated
423
[2]
K.Y. Choi and B.A. Dempsey, In-line coagulation with low-pressure membrane filtration, Water Res., 38 (2004) 4271–4281. C. Guigui, J.C. Rouch, L. Durand-Bourlier, V. Bonneylye and P. Aptel, Impact of coagulation conditions on the in-line coagulation/UF process for drinking water production, Desalination, 147 (2002) 95–100.
Removal of natural organic matter from water by in-line coagulation/ultrafiltration process Malgorzata Kabsch-Korbutowicz Wroclaw University of Technology, Institute of Environment Protection Engineering, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland Tel. +48 71 3203639; Fax +48 71 3282980; email: [email protected] Received 29 October 2005; accepted 4 March 2006
1. Introduction The use of ultrafiltration for treatment of water is nowadays growing rapidly. However, the economic use of membrane filtration systems is often limited by fouling, which increases applied pressure drops and cleaning frequencies, and the associated decrease in removal efficiency is observed. Currently, the most common method of preventing fouling is by pretreating the influent to the membrane process with the application of conventional unit processes. A variety of pretreatment processes for UF have been investigated including coagulation, activated carbon adsorption, adsorption on iron oxides or other pre-formed settleable solid phases, or ozonation. Coagulation, as a pretreatment process, can substantially reduce the concentration of natural organic substances found in raw water; thus, it can decrease the membrane potential for fouling and enhance membrane rejection. Common modes of coagulation realization include ordinary coagulation, where the coagulation and sedimentation steps are carried out in separate tanks ahead of the membrane. However, for small membrane systems such complex water treatment train is not advisable and many works
are going on for simplification of membranebased waterworks. One of the solutions is application of in-line coagulation. The term “in-line coagulation” is used to describe the use of a coagulation before membrane filtration, without a sedimentation or pre-filtration step [1,2]. The objective of the study was to investigate the influence of pre-coagulation with three types of aluminum-based coagulants realized as an in-line process with ultrafiltration on the effectiveness of natural organic matter (NOM) elimination and membrane fouling. The influence of coagulant type, its dose and membrane type on membrane fouling, and NOM elimination was analyzed.
2. Materials and methods Experiments were carried out on a model solution prepared from natural water flowing out from The Great Batorow Peatbag (southwest Poland) and dechlorinated tap water. The concentration of organic matter, expressed as UV 254 absorbance amounted to 0.425 cm–1. pH of the water was equal to 7.7. Three aluminum-based coagulants, i.e. alum (Al2(SO4)3),
Presented at EUROMEMBRANE 2006, 24–28 September 2006, Giardini Naxos, Italy. 0011-9164/06/$– See front matter © 2006 Published by Elsevier B.V. doi:10.1016/j.desal.2006.03.389
422
M. Kabsch-Korbutowicz / Desalination 200 (2006) 421–423 100
100
PES30 membrane
80 R abs 254 nm, %
R abs 254 nm, %
80
C30 membrane
60 40 20
60 40 20
0
0 0
d1
d2
d3
0
Coagulant dose, g Al m–3 Al2(SO4)3
d1
d2
d3
Coagulant dose, g Al m–3 PAC 10WA
NaAlO2
Fig. 1. Effect of coagulant type and its dose on natural organic matter (NOM) efficiency removal in the in-line coagulation/ultrafiltration process for polyethersulfone (PES) and regenerated cellulose (C) membranes (d1 = 1.79 g Al m–3, d2 = 2.87 g Al m–3, d3 = 3.59 g Al m–3).
NaAlO2 and polyaluminum chloride (PAC 10WA) have been applied. The coagulation was carried out at Al doses equal to 1.79, 2.87 and 3.59 g Al m–3. The samples were stirred rapidly for 3 min, which was followed by 20 min slow mixing. Then the solution (with flocs of hydrolyzed coagulants) underwent an ultrafiltration process. In this study, Millipore ultrafiltration 1.0
membranes of cutoff = 30 kDa made of polyethersulfone (PES) and regenerated cellulose (C) were used. The operating pressure was 0.1 MPa. 3. Results and discussion Fig. 1 shows the effects of coagulant type and its dose on the removal of UV absorbance 1.0
PES30 membrane
0.8
C30 membrane
0.8
0.6
0.6 J/J0
J/J0 0.4
0.4
0.2
0.2
0.0
0.0 0
d1
d2
d3
0
Coagulant dose, g Al m–3 Al2(SO4)3
d1
d2
d3
Coagulant dose, g Al m–3 PAC 10WA
NaAlO2
Fig. 2. The influence of coagulant type and its dose on flux decline in the in-line coagulation/ultrafiltration process for polyethersulfone (PES) and regenerated cellulose (C) membranes (d1 = 1.79 g Al m–3, d2 = 2.87 g Al m–3, d3 = 3.59 g Al m–3).
M. Kabsch-Korbutowicz / Desalination 200 (2006) 421–423
(abs 254). As can be inferred from the presented results, the application of alum or polyaluminum chloride resulted in the increase of organic matter elimination, while the use of sodium aluminate did not affect the separation of organic substances. The experimental results obtained during ultrafiltration of water-containing NOM through C and PES membranes (Fig. 2) showed that application of in-line coagulation considerably reduced membrane fouling.
process might be a good solution to the problem of small membrane-based water treatment plant operations. Acknowledgement The work was partly supported by Polish Ministry of Education and Science, Grant # 3 T09D 014 29 (years 2005–2007). References [1]
4. Conclusions Application of in-line coagulation/ultrafiltration process with the use of alum or polyaluminum chloride resulted in improved removal of NOM from treated water and reduced membrane fouling. It seems that the investigated
423
[2]
K.Y. Choi and B.A. Dempsey, In-line coagulation with low-pressure membrane filtration, Water Res., 38 (2004) 4271–4281. C. Guigui, J.C. Rouch, L. Durand-Bourlier, V. Bonneylye and P. Aptel, Impact of coagulation conditions on the in-line coagulation/UF process for drinking water production, Desalination, 147 (2002) 95–100.