Best Practices: Simple Protective Measures for Safely Shutting Down an Industrial RO System| Insights by AQUALITEK

Simple Protective Measures for Temporary Shutdown of an Industrial RO System

Industrial reverse osmosis (RO) systems are highly sensitive to shutdown conditions. Even short periods of inactivity can lead to membrane fouling, biological growth, scaling, or even irreversible damage if the system is not preserved properly.

Below are the best and simplest protection practices for various downtime scenarios.

1. Short-Term Shutdown (Within 24 Hours) — Keep the System Wet and Sealed

When the system stops for less than a day, the risk of membrane damage is low.

Recommended actions

•Keep the pressure vessels completely filled with permeate water

•Shut off the high-pressure pump but keep the system sealed

•Avoid allowing air into the membrane housings

Purpose

Maintaining membrane wetness is sufficient for short shutdowns, preventing drying or early bacterial growth.

2. Medium-Term Shutdown (24 Hours to 7 Days) — Low-Pressure Flush Circulation

If the downtime lasts several days, microbial activity becomes a concern.

Recommended actions

•Perform a low-pressure flush every 24 hours (10–20 minutes each time)

•Ensure the system remains full of clean permeate

•Refresh the water inside the membranes when possible

Benefits

•Prevents bacteria from colonizing membrane surfaces

•Reduces fouling and scaling caused by stagnant water

•Keeps membranes in a ready-to-start condition

This is the simplest and most effective method for medium-term shutdown.

3. Long-Term Shutdown (More Than 7 Days) — Chemical Preservation

For extended downtime, simple flushing is not enough—chemical preservation is essential.

Common preservation solutions

•1%–2% sodium metabisulfite (SMBS) solution

•Mild acidic solutions (pH 3–6) recommended by membrane manufacturers

Key notes

•Prepare the preservation solution strictly according to membrane guidelines

•Ensure membrane housings are completely filled with no trapped air

•Replace the preservation solution every 1–2 months

Purpose

•Suppresses microbial growth

•Prevents membrane drying

•Provides stable long-term protection for inactive RO systems

4. Ensure Zero Chlorine and Proper pH Before Shutdown

Regardless of downtime duration, correct water conditions before shutdown are mandatory.

Always ensure:

•Residual chlorine = 0 (to avoid membrane oxidation)

•SDI < 5

•pH within manufacturer limits (typically 4–10)

Reason:
Shutdown water remains in contact with the membrane for long periods, so poor water quality dramatically increases the risk of damage.

5. Keep the Membranes Wet — Never Allow Drying

RO membranes must remain fully hydrated at all times.

If membranes dry out, it may cause:

•Irreversible structural damage

•Permanent increase in salt passage

•Performance that cannot be restored through cleaning

Wet storage is the foundation of all shutdown protection.

6. Record Conditions Before and During Shutdown

Proper documentation makes future startup safer and more predictable.

Recommended data to record:

•Shutdown date and expected duration

•Preservation method used

•Concentration and pH of chemicals

•Confirmation that housings were filled and no air was trapped

This ensures smooth troubleshooting and startup after long-term shutdowns.

Conclusion

The primary goals of RO shutdown protection are to keep membranes wet, inhibit microbial growth, prevent scaling, and avoid oxidation. By choosing the right protection strategy—ranging from simple wet storage to periodic flushing and chemical preservation—you can significantly extend membrane life and ensure the system restarts safely at any time.