The use of a hollow-fibre membrane for microfiltration introduces axial fea
tures which have important implications for both module design and fouling
behaviour. The rate and mechanism of fouling of these fibres depend on thei
r length and diameter. In this paper, the effect of fibre length on fouling
behaviour is investigated. Axial features play a key role in the initial s
tages of fouling, but become less significant as permeate flowrates decline
substantially. The rate of fouling is initially insensitive to fibre lengt
h, but as fouling progresses, longer fibres foul more slowly. After substan
tial fouling, the rate of fouling becomes dependent on membrane surface are
a, as might be expected from a planar membrane. A simple model is presented
which isolates the contribution to fouling due to axial features arising f
rom hollow-fibre geometry. This model predicts the experimentally-observed
dependence of fouling behaviour on fibre dimensions under conditions where
axial features are significant. Although, properties of the feed material (
such as particle size, size distribution, cake permeability and compressibi
lity) and transport phenomena (such as inertial lift and back-diffusion) ma
y be key contributors to membrane fouling, the decline in permeate flowrate
is dominated by axial features until substantial fouling has occurred. (C)
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