NAMS 2002 Workshop - ICOM 2008

Membrane Fouling - UF & Water Treatment – 6
Tuesday July 15, 5:00 PM-5:30 PM, Honolulu/Kahuku
On the Representativeness of Model Polymers in Fouling Research
A. Drews (Speaker), TU Berlin, Berlin, Germany - anja.drews@tu-berlin.de
A. Shammay, UNESCO Centre UNSW, Sydney, Australia
V. Chen, UNESCO Centre UNSW, Sydney, Australia
P. Le Clech, UNESCO Centre UNSW, Sydney, Australia
Objectives In an attempt to track down the culprit components or conditions, labscale
fouling experiments where the complexity of the interacting phenomena is
reduced are carried out by many groups all over the world. Such experiments
often involve small-scale (test cell) membrane filtration experiments with either
real feed suspensions, supernatants or model substances such as xanthan gum
or alginate (e.g. [1]). In reducing the complexity, the representativeness of
conclusions drawn from these trials becomes highly questionable - not only
quantitatively but also qualitatively. During such investigations under allegedly
more defined conditions a number of problems can be encountered, concerning
both filtrations conditions (different fouling mechanisms occur at constant flux
and constant pressure, respectively, or by lack of air scour in test cells [2]) and
composition of the feed suspension. For the filtration of real feeds, it is known
that even a few hours, which often elapse between sampling and filtration tests,
can lead to potentially unrepresentative fouling behaviour [2]. Model polymers
are assumed to be more stable - generally without proof - and more defined but
might still be unrepresentative due to the following: a) The form in which they are
obtained or prepared (completely dissolved or particulate) will affect their
fouling/adsorption potential [3], b) the chemical structure of the substance might
be largely different from that found in the real feed, c) the absence of the solids
matrix might cause largely different fouling mechanisms, and d) fouling might not
always mainly be caused by biopolymers. This study aims at elucidating the
representativeness of model foulant experiments in fundamental fouling
research.
Methods Test cell experiments (J = const, air-sparged, MF and UF membranes)
were carried out with suspensions or solutions of alginate, xanthan gum, BSA,
yeast, and bentonite (pure and spiked with BSA and/or alginate) under sub- and
supercritical flux conditions. A new membrane was used for each trial. To
determine the influence of “aging” of the model suspension on filtration results,
experiments were repeated after several hours of stirring and pumping through
the set-up. SMP, EPS and TOC were analysed in the feed and permeate [4, 5].
Results were compared to data obtained with sludge.