NAMS 2002 Workshop - ICOM 2008

Membrane Fouling - General Topics – 6
Monday July 14, 12:15 PM-12:45 PM, O’ahu
Visual Characterization of Fouling Behaviour By Activated Sludge Model
Solutions
Y. Marselina, University of New South Wales, Sydney, Australia
P. Le-Clech, (Speaker) University of New South Wales, Sydney, Australia
R. Stuetz, University of New South Wales, Sydney, Australia
V. Chen, University of New South Wales, Sydney, Australia, v.chen@unsw.edu.au
Fouling can be easily characterized with the hydraulic performances of the
membrane, such as transmembrane pressure (TMP), flux and resistances. Better
insight of fouling can also be obtained by using visualization methods, which
include invasive and non-invasive techniques. The non-invasive techniques
provide some advantages over the invasive techniques, by analyzing the
membrane without removing it from its membrane module. Direct observation
(DO), which consists of modified crossflow module, microscope and video
camera, is one of the non-invasive techniques that can be used to visualize the
fouling deposition and removal on the hollow fibre membrane.
In this paper, the DO technique will be used to further characterize the fouling
behaviour for extracellular polymeric substances (EPS) in activated sludge for
membrane bioreactor (MBR) application. Recent research based on the effect of
the feed on MBR fouling has been conducted by using model solutions to mimic
the major foulants found in the mixed liquor. The bentonite particulate can be
used to approximate the behaviour of biomass particles and flocs. The alginate
and xanthan gum can be used to model the carbohydrate fraction and bovine
serum albumin (BSA) used to model the protein fraction of the EPS material in
the biomass. The glycerol was used to change the viscosity property of the fluid
and model the Newtonian fluid. Moreover, the xanthan gum was used to model
the non-Newtonian fluid.
During the filtration of the bentonite - alginate mixture, the fouling deposition
mechanisms were showed by the formation of the stagnant and fluidised layer on
the membrane surface. When the concentration of alginate in the bentonite -
alginate mixture was increased, the TMP and specific cake resistance increased
but the stagnant fouling thickness (Hc) decreased, indicating dense fouling layer.
Although the Hc decreased with the alginate concentration in the mixture, the
cleaning time required to remove most of the reversible fouling increased. This
showed that the addition of alginate contributed to the changes in the fouling
layer morphology by increasing the cohesion bonding between deposited
foulants and the adhesion bonding between foulants and membrane. It was
observed that the fouling removal mechanisms in the presence of alginate were