Best Practices for Cleaning a VLS Crossflow

VLS Crossflow Machine

The following instructions are for a VLS three element crossflow system. For larger systems, multiply the dosages by the appropriate factor. Note: chemical additions are never linear and water pH varies from facility to facility. Start with the suggested dosage and then gradually add more to the suggested pH’s called out. Make sure when in recirculation mode that you have 100% of the permeate going to the upper manifold. It may be necessary to have the lower permeate manifold open during filling (depending on your model) but be sure to close it when the system is completely filled. Also, when cleaning, never exceed 3,000 liters per hour of permeate as higher flow will prematurely wear out the membranes resulting in higher NTU’s. Less is better to ensure the majority of flow is scrubbing the membrane walls.


  1. Gradually bring temperature up to 38°C (100°F).

    Note: If the temperature of the membranes are already at ambient temperature, you can bring in the 38°C (100°F) water immediately. Avoid shocking the membranes with too high of temperature differential if membranes are cold. NEVER exceed an immediate temperature differential of 30°C (86°F).

  2. Put into recirculation mode for 5 minutes.
  3. Dump water and fill with 38°C (100°F).
  4. Put into recirculation mode.
  5. Add 400mL of 30% liquid sodium hydroxide or potassium hydroxide. More may be necessary if the house water has a low pH.
  6. Add to on board chemical tank and check pH after 5 minutes.
  7. Confirm pH 12 and add more if necessary.
  8. Circulate for 1 hour or more depending on how soiled the membranes are or until 70°C (158°F).
  9. Add 1000mL of 10% liquid hydrogen peroxide to chemical tank and existing cleaning solution.
  10. Circulate for 30 min.
  11. Repeat cycle if necessary.
  12. Note: The pH should never go above 12. Also, never add granulated cleaners without dissolving them first.
  13. Dump the used water and fill with fresh 38°C (100°F) water.
  14. Put into recirculation mode.
  15. Add 250 grams of citric acid to warm water (2-3 gallons) and mix thoroughly.
  16. Add to on-board chemical tank and check pH after 5 minutes.
  17. Confirm pH 3-4 and add more if necessary. The moderate pH ensures that little flushing is required prior to operation.
  18. Recirculate for 20 minutes.

Machine is ready for final flush/rinse.


An acid and sulfur solution should be made up for storage:

  1. Fill with fresh 38°C (100°F) water.
  2. Put machine into recirculation mode.
  3. While machine is recirculating, add in 150g of citric acid.
  4. Check pH after 5 minutes and add more if necessary to bring to pH to 2-2.5.
  5. Mix in 560 grams of metabisulfite.

DO NOT STORE SYSTEM IN A FREEZING ENVIRONMENT. When getting ready to use the filter from storage mode, it may take a few flushes to get rid of the storage solution. Let the machine recirculate and after 2-3 minutes, dump the water and bring in fresh water. Repeat as necessary to bring the pH back up to the same level as the water at your facility. If the machine has been stored for a month or longer, consider doing a quick sanitation and rinse. Every month or so a fresh storage solution should be made up and recirculated for just a couple minutes.


If transmembrane pressure does not spike, a warm rinse can be applied to quickly regenerate flow in place of a CIP. Do not go above 0.5 Bar transmembrane pressure (TMP) prior to a warm rinse, otherwise, a full cleaning is recommended.

  1. Push product back to their respective tanks.
  2. Bring the temperature up gradually if the product being filtered was below 4.4°C (40°F).
  3. Turn system on in recirculation mode and while it is running add in hot water while bleeding off existing water to get up to 38°C (100°F).
  4. Put into recirculation for 10 minutes.
  5. Dump water to drain and bring in ambient water to cool membranes to ambient temp. You do not need to turn on the system. Just the natural ambient water coming in will cool the system down. When full, dump water to drain and begin processing.


To ensure there are no broken capillaries, you may select the integrity test function. Prior to hitting start, you need to do the following:

  1. Drain the fluid from the retentate side of the system only.
  2. Reduce the incoming air or gas pressure to 0.8 bar.
  3. Open the air/gas valve on the permeate side and double check pressure.
  4. Press start from the integrity test page.


Hold Volume 27 gallons 50 gallons 70 gallons
Caustic (30% liquid) 2 liters 4 liters 5.5 liters
Caustic (powder) 2 lbs. 4 lbs. 6 lbs.
Hydrogen Peroxide (10% liquid) 2 liters 4 liters 5.5 liters
Citric Acid (powder) 250 g 500 g 750 g
KMBS 250 g 370 g 460 g