NAMS 2002 Workshop - ICOM 2008

Desalination I – 3
Monday July 14, 3:30 PM-4:00 PM, O’ahu
Submerged Hollow Fibre Pre-treatment to RO in Seawater Applications
Y. Ye (Speaker), UNESCO Center for Membrane Science and Technology, School of Chemical
Science, Sydney, Australia
L. Sim, UNESCO Center for Membrane Science and Technology, School of Chemical Science,
Sydney, Australia
V. Chen, UNESCO Center for Membrane Science and Technology, School of Chemical Science,
Sydney, Australia, v.chen@unsw.edu.au
A. Fane, UNESCO Center for Membrane Science and Technology, School of Chemical Science,
Sydney, Australia
Since reverse osmosis membranes are very sensitive to foulants such as
colloids, inorganic scale and biofouling, proper pre-treatment process therefore
becomes a critical factor for a successful long-run seawater reverse osmosis
(SWRO) plants. Recently, low pressure membrane has been successfully used
in the pre-treatment for wastewater reclamation by reverse osmosis (RO). This is
because membrane pre-treatment offers several advantages such as smaller
plant footprint, better quality of feed water for RO unit and less chemical
consumption. As a result, the use of low pressure membrane is now being
considered as a viable solution for pre-treatment to SWRO plants but further
improvements in membrane configurations and operations need to be
investigated to reduce fouling and energy consumption.
The aim of this study is to investigate the efficiency of pre-treatment using MF
and UF submerged hollow fibre system by varying the operation parameters.
Three different type of hollow fibre (0.22um polypropylene (PP) membrane and
two 0.04um polyvinylidene fluoride (PVDF) membranes with different fibre outer
diameters) were used for the pre-treatment of the synthetic seawater. Three
different modes of filtration: continuous, relaxation and backwash mode of
filtration were investigated. For all three membranes used, it was found that,
during the relaxation mode of filtration, TMP only decreased slightly after 40s of
relaxation in each filtration circle (1hr). The decrease of TMP was also observed
after each backwash (3560s filtration, 40s backwash where the backwash flux is
twice of the permeate flux). However, the rate of TMP increase during each
filtration circle for the backwash mode is much higher than that in the relaxation
mode of filtration. Consequently, it leads to higher final TMP value in the end of
20 hr’s backwash mode filtration when compared to the relaxation mode.
Meanwhile, comparing different membranes fibres, it appears that bigger pore
size PP hollow fibre has higher dTMP/dt in each cycle of filtration after backwash
than those observed for smaller pore size PVDF membranes. All these indicate
that inappropriate backwash might even accelerate the membrane fouling. The
further characterization of the membranes using different mode of filtration is