EUROPEAN CONFERENCE ON FLUID PARTICLE
SEPARATION (ECFPS) 5 - 7 october 2010, Lyon - FRANCE
Session : l-6 Product related filtration and separation. Water
New seawater pre-treatment by
ultrafiltration (UF) operation
intensification
M. Pontié*, A. Thekkedath, S. Plantier,
J.B. Castaing, A. Massé, P. Jaouen
*MPONTIE@aol.com
Laboratory GEPEA, UMR CNRS 6144, 37 bd. de l’Université,
44602 Saint-Nazaire, France
General introduction
One of the critical issues in the successful application of
membrane systems for water treatment is the adhesion of
foulants to the membrane surface following by a cake
elaboration*.
The dramatic wellknown consequence is a decline in permeate
flow followed by an increase in operational and maintenance
costs.
Main aim : investigate the possibilities of de-organized
the cake by insertion of large size clays particles.
*A. THEKKEDATH, M. PONTIE, C.R. Chimie 10 (2007) 803- 812.
2/17
3/17
J/J0
Why Ultrafiltration ??
UF less susceptible to fouling than MF
M. Pontié et al. Desalination 204 (2007) 155-160
4/17
Experimentals
Membranes
(Millipore)
YM 100,
30, 10
Membranes and bench scale unit
Material
MWCO
Regenerated
cellulose,
Flat sheet
100 kDa
30 kDa and 10 kDa
+
Millivoltmeter
-
Ag/AgCl
electrode
Filtration cell
manometers
Ag/AgCl
electrode
N2
Membrane
200 nm
SEM image of the 100 kDa surface
morphology (2D-FD :1.90)
Permeate
Dead-End filtration cell in a bench scale
lab. pilot (membrane area 29 cm2)
5/17
Mean particle size (nm)
Zeta potential (mV)
Humics characteristics
2500
40
2000
20
1500
0
1000
-20
500
-40
0
1
2
3
4
5
6
7
8
9
10
11
12
Zeta potential (mV)
Mean particle size(nm)
Acrôs
CO2H
HO
H
CO2H
O
O
-60
13
O
pH
O
CO2H
OH
CO2H
H
R
O
humic acid model structure
(Stevenson, 1982)
OH
CO2H
OH
N
O
OH
O
O
O
N
O
HN
OH
O
C
NR
The distribution of mean particle size (nm) and zeta
potential (mV) for Acros humic acid (5 mg/L) at pH=6.2
(Zetasizer Malvern Co.) :
• Average particle size (250 nm)
• Charge (-30 mV)
6/17
Mont-CTAB preparation steps
Na.xH2O
Montm-Na
Natural clay
(BENTONITE)
INTERCALATION
CALCINATION
Micropore
Pillars
pillared clay
Inorgano clay
CTAB ADSORPTION
SEM images of Mont-Al -CTAB (2 nm C deposition, beam
energy 3 keV, and the magnifications x500 and x10,000)
Mont-CTAB
Relative elementary composition analysis of Mont-Al(C) from EDX (excluded C)
%
Na
Mg
Al
Si
Cl
K
Ca
Fe
1.31
2.56
34.26
56.51
-----
2.31
------
3.31
SEM images show microporous surface with aggregates (average size of 3 mm±2)
M.W. NACEUR et al. Desalination 168 (2004) 253-258
7/17
t/V (s/L)
Modified fouling index for ultrafiltration (MFI-UF)
V (L)
t/V vs. V graph to determine MFI-UF and a humic acid cake formed on a PES membrane




t = µ.R m + µ.I
2 .V
V DP.S 2DP.S
Purely based on cake formation
Fouling potential of the feed solution
Directly dependent on the concentration of particles
More reliable than SDI (silt density index)
MFI
SCHIPPERS J. C., VERDOW J, Desalination 32 (1980) 137
8/17
Determination of cake Fractal Dimension (FD)
• Image J software is used to determine the fractal dimension from SEM images
• From the original image, a threshold (binary) image is generated
• Fractal box count method is applied
• The slope of the log N (count) vs. log  (size) plot is used to get fractal dimension
of the image. The absolute value is taken as the FD.
2D-FD = 1.5 to 1.75
FD = 1.57
Particle-cluster aggregation
log N = -(FD).
log 
(Diffusion-limited
aggregation)
Original and threshold images
MANDELBROT B. B., The Fractal Geometry of
Nature, Freeman, San Francisco, 1982. 9/17
Results and discussion
Role of membrane MWCO
100 k Da
30 kDa
10 kDa
1,20
Acros HA, constant pressure of 2 bars
pH 6.7 and 5 mg/L HA
Normalized flow, J/J0
1,00
0,80
0,60
0,40
0,20
0,00
0
.
0,5
1
1,5
2
2,5
cumulated volume, V(L)
Tighter membranes show lower flux decline
10/17
SEM images of cakes with and
without Mont-CTAB - 100 kDa
Rm x 10-12 m-1
= 0.67
R HA +Mont-CTAB x 10-12 m-1 = 0.45
RHA x 10-12 m-1 = 1.67
HA alone
HA + Mont-CTAB
Rcake decreased 3 times in presence of Mont-CTAB
11/17
1,20
3000
1,00
2500
0,80
2000
t/V (s/L)
Normalized Flux, J/J0
Intensification of UF-100 kDa with Mont-CTAB
0,60
20%
0,40
1500
1000
0,20
MFI : 1358 ± 140 s/L2
 594 ± 60 s/L2
500
0,00
0
0
0,2
0,4
0,6
0,8
1
1,2
0
0,2
0,4
Cumulated volume, V(L)
HA
HA + Bentonite
Less fouling occured with
Mont-CTAB particles and a GAIN
IN FLOW of 20 % was observed
0,6
0,8
1
1,2
Cumulated volume, V (L)
HA
HA + bentonite
MFI decreased 2 times
in presence of Mont-CTAB
THEKKEDATH A., PhD Thesis, Angers University (France), (2007)
12/17
FD of cake surface imaging
with and without Mont-CTAB
HA alone
2D- Fractal
dimension
1.57
FD decreases in presence of Mont-CTAB
showing a more porous cake
1.45
HA + Mont-CTAB particles
bentonite
Humic Acid
13/17
FD, MWCO and Hydraulic permeability
FD
Permeability (L.h-1.m-2.bar-1)
(Fouled membrane)
(Fouled membrane)
MWCO
100 kDa
1.57
155
30 kDa
1.62
83
10 kDa
1.82
20
1,85
1,8
1,8
1,75
1,75
1,7
1,7
FD
FD
1,85
1,65
1,65
1,6
1,6
1,55
1,55
1,5
1,5
0
20
40
60
80
Permeability
100
120
-2
-1
140
-1
(L. m . h . bar )
160
180
0
20
40
60
80
100
120
MWCO (k Da)
 FD values were in a decreasing trend with increasing MWCO
 Higher value of permeability corresponds
to a lower value of FD or a more porous cake.
14/17
Conclusion and perspectives
Less fouling occured in UF in presence of Mont-CTAB particles with :
- a gain in permeate flow of 20%
- a lower cake resistance and a lower MFI
- a lower FD (NEW RESULT) meaning a more porous cake
Opening interesting perspectives for the intensification of UF as
seawater pre-treament before RO.
Rejection water
Coagulant injection by
peristaltic
Lamellar settler
Permeate
Feed tank
(Sea water)
Feed pump
Feed pump
Feed Tank
(adsorption+
coagulation)
UF
UFMembrane
submerged
Hollow
Fibers + Mont-CTAB
15/17
16/17
Acknowledgements
 MEDRC : Project n° 06-AS-003 (Sultate of Oman)
 AWWARF for funds to A. Thekkedath thesis
 Blida University (Algeria), M.W. Naceur
 LCME, Poitiers (France), B. Legube
 Microscopy Dept. (SCIAM), Angers university, (France), R. Filmon
www.gepea.fr
MERCI to Nourredine Nghaffour
(KAUST)
Lots of thanks to my young
collaborators : A. THEKKEDATH, H.
DACH, F. DE NARDI, K. KECILI
17/17
16
Annexe
Chemical conditions
Role of pH
NOM in solution
NOM on membrane surface
Low pH
pH 3
Coiled, compact
configuration
Severe flux decline
High pH
Stretched,
linear configuration
pH 9.5
Lower flux decline
• At basic pH, a thin and loosely packed cake layer
• At acidic pH, a dense and compact cake layer
HONG S. and. ELIMELECH M, J. Membr. Sci. 132 (1997) 152 A1