Deposit membrane fouling: influence of specific cake
layer resistance and tangential shear stresses
A. Charfi, J. Harmand, N. Ben Amar, A. Grasmick and M. Heran
ABSTRACT
Cake fouling is the leading cause of membrane permeability decrease when filtering mixed liquor
suspension containing high suspended solid concentrations. A simple model is proposed to simulate
the cake resistance evolution with time by considering a macro-scale fouling only linked to the
accumulation of particles on the membrane surface. This accumulation appears as the difference
between the flux of deposited particles due to the filtration and the flux of particles detached from
the membrane surface due to the tangential shear stresses caused by, recirculation flow in
sidestream membrane bioreactor (MBR) or gas sparging close to the membrane surface for
submerged MBR configuration. Two determining parameters were then highlighted: the specific cake
resistance and the ‘shear parameter’. Based on these parameters it is possible to predict model
outputs as cake resistance and permeate flux evolution for short-time filtration periods.
A. Charfi (corresponding author)
A. Grasmick
M. Heran
Institut Européen des Membranes (IEM),
Université Montpellier 2, place Eugene Bataillon,
CC05, 34095 Montpellier, France
E-mail: amine.charfi@ymail.com
A. Charfi
N. Ben Amar
Laboratoire de Modélisation Mathématique et
Numérique dans les Sciences
de l’Ingénieur, ENIT, B. P 37 Le Belvédère 1002
Tunis, Tunisia
and
Institut National des Sciences Appliquées et de
Technologie,
B. P. 676, 1080 Tunis Cedex, Tunisia
J. Harmand
Laboratoire de Biotechnologie de l’Environnement,
INRA, UR0050, Avenue des étangs,
11100 Narbonne, France
and
MODEMIC Research Group,
INRIA, Laboratoire de Mathématiques,
Informatique et Statistique pour l’Environnement
et l’Agronomie-INRA,
2 Place Viala, 34060 Montpellier, France
Key words | cake formation, membrane fouling modelling, specific cake resistance, tangential shear
stresses
NOMENCLATURE
m
acc
Specific mass of accumulated cake (g/m
2
)
m
acc,lim
Maximum specific mass of accumulated cake
(g/m
2
)
m
in
Specific mass of particles approaching the mem-
brane surface (g/m
2
)
m
out
Specific mass of particles removed from the mem-
brane by shear forces (g/m
2
)
X Total suspended solids concentration (gTSS/L)
J
p
Permeate flux (Lm
À2
h
À1
)
TMP Trans-membrane pressure (Pa)
μ Dynamic viscosity (Pa s)
R
0
Clean membrane resistance (m
À1
)
R
c
Cake resistance (m
À1
)
J
0
Initial permeate flux (Lm
À2
h
À1
)
β Shear parameter (kg
À1
)
α Specific cake resistance (mk g
À1
)
R
c,max
Resistance at steady state (m
À1
)
J
p,end
Permeate flux at steady state (Lm
À2
h
À1
)
INTRODUCTION
Many studies have tried to model fouling in membrane pro-
cesses. Many are based on the four basic fouling
mechanisms introduced by Hermia () namely cake foul-
ing, pore constriction, complete blocking, and intermediate
blocking. Despite being established for dead-end filtration
at constant pressure, these models have been also used for
cross-flow filtration (Ho & Sung ; Charfi et al. ) or
have been adapted to cross-flow filtration (Field et al. )
by taking into account the role of shear forces to eliminate
particle deposition on the membrane surface (De Bruijn
et al. ). More realistic models are also presented when
considering simultaneous fouling mechanisms; while
Bolton et al.() combined Hermia’s models, Wu et al.
() established a model considering simultaneously
three fouling mechanisms namely pore constriction, pore
blockage, and cake filtration associated to soluble, colloidal
and suspended activated sludge components, respectively.
Abdelrasoul et al.() considered the probability of par-
ticle deposition on the membrane surface or on another
1 © IWA Publishing 2014 Water Science & Technology | in press | 2014
doi: 10.2166/wst.2014.186
Uncorrected Proof