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TMM-300
General instructions and conditions for RO cleaning
TORAY REVERSE OSMOSIS ELEMENTS section page:
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Operation, Maintenance and Handling Manual rev.: 105
v
ersion: October 2012
General instructions and conditions for RO cleaning
The surface of an RO membrane is subject to fouling by suspended solids,
colloids and precipitation. Pre-treatment of feed water prior to the RO process
should be designed to avoid contamination/fouling of membrane surface as
much as possible.
Operation at optimum conditions (permeate flow rate, pressure, recovery and
pH-value) will result in less fouling of the membranes.
SDI15 is a measurement of particulates present in the feed water. With high
SDI15 values (even in allowable range), membrane fouling due to particulates
can cause performance decline in long-term operation.
Fouling can also be a consequence of large variations in raw water quality, or of
errors in RO operation mode.
Fouling of the membrane surface will result in a performance decline, i.e. lower
permeate flow rate and/or higher solute passage and/or increased differential
pressure loss from feed side of a stage to the brine side.
Illustration 1 illustrates the effect of flux decrease due to fouling, and restoration
of flux through cleaning. If the source of the foulant is not addressed and
corrected, foulant removal will only bring temporary relief, as illustrated by the
“saw tooth” pattern of the permeate flow in Illustration TMM-300.1.
0
2
4
6
8
10
Normalized Permeate Flow Rate
typical
m³
/h
Periodical cleanings
Illustration TMM-300.1: Effect of fouling on permeate flow rate
It should be noted that the best solution is typically to remove the foulant
through improved pretreatment rather than subject the membranes to repeated
cleanings.
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Page 61
Coral Sea Owner's Manual
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