The following are symptoms of organics fouling:
- Membrane discoloration.
- Low flow on individual membrane test data.
- Possible high pressure differential on individual membrane test data.
The recommended cleaning approach is:
- A low pH clean using either RoClean P303 or L403, followed by a high pH clean using either RoClean P111 or, for severe cases, RoClean P112 or L212.
The combination of a low pH clean followed by the high pH solution is extremely effective in removing organics. The low pH cleaner helps break the bridge between the organics and the membrane. The high pH solution then lifts the foulant off the membrane surface. This is why there is sometimes a color discharge only when using the high pH cleaner. Don’t be misled though, the low pH clean was a vital step in the cleaning regime.
Steps to preventing organic fouling include:
- Remove the organics from the RO feedwater with a properly designed multimedia filter with coagulant addition. Metal salts blended with a polymer are usually the most effective coagulant for high organic waters.
Notes:
Figure 3 is an example of a spent cleaning solution. The foulant was humic acid, dissolved by formulated cleaners.
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