Vol 33 No 4 Text - International Ozone Association

Ozone News Volume 33, No. 4
Effect of dissolved ozone on TMP
The change of TMP (transmembrane pressure) with a
variation of dissolved ozone on the membrane surface
is shown in Figure 3. It is evident that the behavior of
TMP is influenced by dissolved ozone concentration.
That is, keeping the dissolved ozone concentration on
the membrane surface at 1.0mg/L can prevent the rise
of TMP. Therefore, this reveals that the dissolved
ozone may decompose or modify organic materials on
the membrane surface and reduce fouling of
membrane. The dissolved ozone concentration of
1.0mg/L is necessary to keep the stable operation of
MF membrane system.
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The change of TMP during the continuous filtration test
is shown in Figure 4. The dissolved ozone concentration
on the membrane surface was controlled approximately
1.0 mg/L. Membrane flux was 5.0 m3/m2. d. TMP doesn’t
rise rapidly and change slowly. At an elapse of 3,800
hours, TMP goes to only 120kPa. This value is less than
TMP of 200kPa, at which chemical cleaning is necessary.
This proves that a stable membrane operation at high flux
in the long term is obtained by controlling the dissolved
ozone concentration of 1.0 mg/L on the membrane
surface.
Conclusions
The reclamation system using MF membrane together
with ozone could provide high filtration flux of 5 m3 /m2. d
and a stable operation without chemical cleaning in the
long term. The water obtained by this reclamation system
was a high quality and excellent in security against
pathogenic organisms.
This system has following superior features:
1. The reclamation water obtained has a high quality
without color, odor and suspended matters.
Furthermore, it is excellent in security against
pathogenic organisms.
2. An economical membrane filtration system can be
designed based on higher filtration flux.
3. This system can be installed in a limited space.
Based on the above-mentioned data, the reclamation
plant was constructed at Shibaura water reclamation
center, bureau of sewerage of Tokyo Metropolitan
Government and began to operate in April 2004. This
plant has treatment capacity of 4,300 m 3/d. MF
membrane units are shown in Figure 5 (page 30). The
reclamation water is distributed to the redeveloped areas
in Shinagawa, Shiodome and Oosaki as toilet flashing
water and environmental uses. The water quality of
reclamation water obtained is much better than that of
existing sand filters and gets a good reputation by users.
In addition, the heat island phenomenon is now at stake
in highly urbanized areas. Sprinkling water on the roads
gives effect of preventing temperature on the roads and in
the atmosphere from going up. This reclamation water is
used as a measure of the heat island phenomenon. In the
future, the reclamation water with high water quality is
desired to apply progressively for many kinds of reuse.