NAMS 2002 Workshop - ICOM 2008

Ultra- and Microfiltration III - Membranes – 1 – Keynote
Friday July 18, 2:15 PM-3:00 PM, Honolulu/Kahuku
Pilot-scale Integrity Monitoring of Microfiltration Processes Using a Novel
Multi-membrane Sensor
F. Wong (Speaker), Advanced Water and Membrane Centre, Institute of Env. Sci. and Eng.,
Singapore - jincai@ntu.edu.sg
A. Fane, Nanyang Technological University, Singapore
J. Phattanarawik, Norwegian University of Sci. and Tech., Norway
M. Wai, Advanced Water and Membrane Centre, Institute of Env. Sci. and Eng., Singapore
J. Su, Advanced Water and Membrane Centre, Institute of Env. Sci. and Eng., Singapore
Effective contaminant removal in a membrane process is guaranteed only when
the membrane is intact. In practice, the performances of the membrane filters
may be compromised by presence of oversized pores, broken fibres or leaking
O- ring connectors. Membrane integrity monitoring is to verify whether membrane
filters are meeting the treatment objectives. The popular methods used for
membrane integrity monitoring are pressure decay test, particle counting and
particle monitoring, sonic testing, and turbidity measurement [1-3]. Unfortunately,
the currently available integrity monitoring techniques show some disadvantages,
i.e. labour- intensive, time-consuming, high cost, low sensitivity or requiring
highly skilled operator, which limit their application.
The work presented here is part of an on-going project on pilot-scale integrity
monitoring of filtration processes. Novel membrane integrity sensors developed
by Phattaranawik et al. were employed in the pilot trials [4]. The novel sensor is a
two-membrane device incorporating small-area membranes connected in series.
The permeate from the first membrane flows totally to the second membrane,
considered to be the retentate of the second membrane. Sensor parameter is
defined as the ratio of the trans- membrane pressures of the two membranes.
When there is the problem such as a breach, chemical degradation or biological
degradation of the filtration membrane or mechanical failure of O- rings or
gaskets, more particles in the filtrate will deposit on the surface of the first
membrane within the sensor, resulting in significant drop in the permeate
pressure of the first membrane. Consequently, increased trans- membrane
pressure of the first membrane and decreased trans-membrane pressure of the
second membrane are observed. The value of sensor parameter thus rises, and
an alarm will be sent to the operator if the sensor parameter exceeds certain
limit. Pilot testing of the integrity sensor would be performed at three different
water plants in Singapore. The source waters used would be MF treated
secondary effluent (plant 1), submerged membrane treated reservoir water (plant
2), and MBR treated municipal wastewater (plant 3). Several integrity sensors
would be installed at the three sites and the continuous online integrity testing
would last for several months.