Reverse Osmosis Plant Shutdown

Advanced Reverse Osmosis Technology

Permeate Flush

As salts in the feed water have concentrated up and exceeded their solubility during operation, they should be rinsed out prior to any shutdown (>15 minutes). Rinsing of the membranes with permeate water on shut will also aid the flushing of colloids and bacteria from the membrane surface.

Flow rate during flushing should be based on the recommended cleaning instruction flow rates. This is normally 30 – 40 gpm [6.8 – 9.1 m3 /hr] per pressure vessel.

Flushing time should be long enough for the conductivity out to equal the conductivity in. This is typically 15 – 20 minutes.

If the permeate flush is unavailable, feed water can be used by allowing low-pressure water to replace the water within the system by delaying the inlet valve closing. Scale inhibitor should be turned OFF during the permeate flush. If the water temperature in the membranes exceeds 115 Degree F, flush water should be continuously passed through the system to prevent membrane degradation.

Preservation

For shut downs longer than as 24 hours, biological growth in the RO system should be controlled. This requires the introduction of a chemical to kill bacteria and prevent growth. Any preservation chemical would then have to be rinsed out from the system when it is restarted.

Various membrane preservation procedures are available. For further information or assistance please contact Reverse Osmosis Chemicals International on +44 (0) 161 877 2334 or e-mail info@rochemicals.com.