M. Pontié*, A. Thekkedath, S. Plantier,

J.B. Castaing, A. Massé, P. Jaouen

New seawater pre-treatment by ultrafiltration (UF) operation

intensification

Laboratory GEPEA, UMR CNRS 6144, 37 bd. de l’Université, 44602 Saint-Nazaire, France

*MPONTIE@aol.com

Session : l-6 Product related filtration and separation. Water

EUROPEAN CONFERENCE ON FLUID PARTICLE SEPARATION (ECFPS) 5 - 7 october 2010, Lyon - FRANCE

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

General introduction

3/17

M. Pontié et al. Desalination 204 (2007) 155-160

UF less susceptible to fouling than MF

4/17

Why Ultrafiltration ?? J

/J0

Membranes

(Millipore)

Material MWCO

YM 100,

30, 10

Regenerated cellulose,

Flat sheet

100 kDa

30 kDa and 10 kDa

5/17

200 nm

SEM image of the 100 kDa surface morphology (2D-FD :1.90)

N2

Permeate

manometers

Membrane

Filtration cell

+ -Millivoltmeter

Ag/AgClelectrode

Ag/AgClelectrode

N2

Permeate

manometers

Membrane

Filtration cell

N2

Permeate

manometers

Membrane

Filtration cell

N2

Permeate

manometers

Membrane

Filtration cell

Membrane

Filtration cell

Membrane

Filtration cell

+ -Millivoltmeter

Ag/AgClelectrode

Ag/AgClelectrode

Dead-End filtration cell in a bench scale

lab. pilot (membrane area 29 cm2)

Experimentals Membranes and bench scale unit

Humics characteristics

-20

-40

20

40

-60

0

3 4 5 6 7 8 9 10 11 12 1321

pH

500

1000

1500

2000

2500

Mea

npar

ticl

esiz

e(nm

)

(mV

)

0

Mean particle size (nm)

Zeta potential

-20

-40

20

40

-60

0

3 4 5 6 7 8 9 10 11 12 1321

pH

500

1000

1500

2000

2500

(mV

)

0

(mV)

Zet

apote

nti

al

-20

-40

20

40

-60

0

3 4 5 6 7 8 9 10 11 12 1321

pH

500

1000

1500

2000

2500

Mea

npar

ticl

esiz

e(nm

)

(mV

)

0

Mean particle size (nm)

Zeta potential

-20

-40

20

40

-60

0

3 4 5 6 7 8 9 10 11 12 1321

pH

500

1000

1500

2000

2500

(mV

)

0

(mV)

Zet

apote

nti

al

-20

-40

20

40

-60

0

3 4 5 6 7 8 9 10 11 12 1321

pH

500

1000

1500

2000

2500

Mea

npar

ticl

esiz

e(nm

)

(mV

)

0

Mean particle size (nm)

Zeta potential

-20

-40

20

40

-60

0

3 4 5 6 7 8 9 10 11 12 1321

pH

500

1000

1500

2000

2500

(mV

)

0

(mV)

Zet

apote

nti

al

Acrôs

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

O

O

N

O

O O

H

HN

CO

NR

N O

OH

O

OH

OO

HO CO2H

CO2H

OH

OH

OH

CO2H

CO2H

OH

R

CO2H

humic acid model structure (Stevenson, 1982)

pillared clay Inorgano clay

Montm-Na Natural clay (BENTONITE)

Na.xH2O

INTERCALATIONCALCINATION

Pillars Micropore

Mont-CTAB

CTAB ADSORPTION

SEM images of Mont-Al -CTAB (2 nm C deposition, beam

energy 3 keV, and the magnifications x500 and x10,000) 

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 m±2)

Mont-CTAB preparation steps

M.W. NACEUR et al. Desalination 168 (2004) 253-258 7/17

Modified fouling index for ultrafiltration (MFI-UF)

V (L)

t/V

(s/

L)

SCHIPPERS J. C., VERDOW J, Desalination 32 (1980) 137

t/V vs. V graph to determine MFI-UF and a humic acid cake formed on a PES membrane

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)

VSPI

Vt .

.2.

P.SR.

2m

+

= µµ

MFI

8/17

• 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.

FD = 1.57

log N = -(FD). log

Original and threshold images MANDELBROT B. B., The Fractal Geometry of Nature, Freeman, San Francisco, 1982. 9/17

Determination of cake Fractal Dimension (FD)

Particle-cluster aggregation (Diffusion-limited aggregation)

2D-FD = 1.5 to 1.75

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0 0,5 1 1,5 2 2,5

cumulated volume, V(L)

No

rmal

ized

flo

w, J

/J0

100 k Da 30 kDa 10 kDa

Acros HA, constant pressure of 2 bars pH 6.7 and 5 mg/L HA

.

Tighter membranes show lower flux decline

Role of membrane MWCO

10/17

Results and discussion

SEM images of cakes with and without Mont-CTAB - 100 kDa

HA alone HA + Mont-CTAB

11/17

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

Rcake decreased 3 times in presence of Mont-CTAB

Intensification of UF-100 kDa with Mont-CTAB

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0 0,2 0,4 0,6 0,8 1 1,2

Cumulated volume, V(L)

Norm

aliz

ed F

lux,

J/J

0

HA HA + Bentonite

12/17

20%

Less fouling occured with Mont-CTAB particles and a GAIN IN FLOW of 20 % was observed

MFI decreased 2 times in presence of Mont-CTAB

0

500

1000

1500

2000

2500

3000

0 0,2 0,4 0,6 0,8 1 1,2

Cumulated volume, V (L)

t/V (s

/L)

HA HA + bentonite

MFI : 1358 ± 140 s/L2 594 ± 60 s/L2

THEKKEDATH A., PhD Thesis, Angers University (France), (2007)

bentonite Humic Acid

1.57

1.45

HA alone

HA + Mont-CTAB particles

FD of cake surface imaging with and without Mont-CTAB

2D- Fractal dimension

13/17

FD decreases in presence of Mont-CTAB showing a more porous cake

FD, MWCO and Hydraulic permeability

1,5

1,55

1,6

1,65

1,7

1,75

1,8

1,85

0 20 40 60 80 100 120 140 160 180

Permeability

FD

(L. m -2. h -1. bar -1)

1,5

1,55

1,6

1,65

1,7

1,75

1,8

1,85

0 20 40 60 80 100 120 140 160 180

Permeability

FD

(L. m -2. h -1. bar -1)

100 kDa 1.57 155

30 kDa 1.62 83

10 kDa 1.82 20

MWCOFD

(Fouled membrane)Permeability (L.h-1.m-2.bar-1)

(Fouled membrane)

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.

1,5

1,55

1,6

1,65

1,7

1,75

1,8

1,85

0 20 40 60 80 100 120

MWCO (k Da)

FD

14/17

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.

15/17

Feed tank (Sea water)

Permeate

Feed Tank (adsorption+ coagulation)

Feed pump Membrane UF

Rejection water

Feed pump

Coagulant injection by peristaltic

Lamellar settler

UF submerged Hollow Fibers + Mont-CTAB

Conclusion and perspectives

16/17

Acknowledgements

Lots of thanks to my young collaborators : A. THEKKEDATH, H.

DACH, F. DE NARDI, K. KECILIMERCI to Nourredine Nghaffour

(KAUST) 16

www.gepea.fr

17/17

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

Low pHpH 3 Coiled, compact configuration Severe flux decline

Chemical conditions NOM in solution NOM on membrane surface

Role of pH

High pH Stretched, linear configurationpH 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

Annexe