Shuffling of RO membrane.

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We have a two-stage RO system in our ETP, with each stage containing one vessel, and each vessel housing 8 membranes. The recovery of the RO plant has decreased, and there has been no improvement despite several CIP cycles. I am considering shuffling the membranes. Is there a thumb rule or pattern for membrane rearrangement? Which membrane should be moved to which location within the vessel? Could you shed some light on this?

4 Answers

  1. If you're seeing a drop in recovery rates in your two-stage RO system, shuffling the membranes could help. Check the age and condition of each membrane, and consider moving older or fouled ones to different spots. Also, do keep an eye on pressure differences and water quality too. 

    Once you've made changes, monitor how your system performs before and after. 

    I hope this helps.

  2. Please check whether there is a problem with the anti-scaling system. What is the hardness of the RO incoming water?I would like to ask if the current water temperature has changed.

  3. I agree with Vinod below. Assuming the problem is scaling rather than biofouling, the membranes at the brine end are most likely to be scaled. If you can replace just the last one there should be a disproportionate improvement but moving them won't achieve much.

    A long shot, but MAYBE if you rotate the membranes and then do a scaling CIP it may be more effective.

    Have you tried a high pH CIP to treat biofouling?

    Finally, does your system allow osmotic backflow on shut down? That helps a lot to remove fouling.

    1 Comment

    1. thanks for your information.
      shall i identify the most scaled / fouled membrane by measuring the weight of individual membrane?
      i have tried high pH cleaning, but no significant improvement.
      since it is small plant (9 m3/hr), we don't have osmotic backflow arrangement in our plant. could you please let me know will the osmotic backflow reduce the chance of fouling and scaling? how dose it works?

      1 Comment reply

      1. Maybe best if you can send a membrane unit off for analysis to a specialist to see what went wrong. I've never heard of weighing the membranes to determine which is the most fouled but maybe it can be done. Perhaps not very helpful advice now but maybe worth always having a spare sealed membrane unit in store so you can try changing out different existing units.

        Osmotic backflow, which a well designed plant should allow but many do not, happens on each shutdown. Flow back THROUGH the membrane helps to clean it, instead of a CIP which washes OVER the feed surface.

        I can recommend an Australian consultant to provide advice but I guess you are in Mumbai and that is problematic.

  4. If the flow has decreased than it is a indication that membrane has choked there is no alternative than replacement of membrane.Shuffling will be very temporary solution.

    1 Comment

    1. I need to do some temporary arrangement until the receipt of new membranes.