From large-scale desalination plants to municipal waterworks, reverse osmosis (RO) membranes are core components of water treatment
systems. They provide precise filtration for a wide range of applications but require careful handling and maintenance to remain effective.
Performance and service life depend largely on raw water quality, pretreatment effectiveness, and daily operating practices.
This guide outlines practical, proven measures to protect your RO membrane investment and keep your system operating efficiently.
① Storage
When: Before installation
Membrane types:
- Dry-type elements: Easier to transport and install; generally have longer shelf life.
- Wet-type elements: Must remain moist and require careful preservation to avoid microbial growth or degradation.
Best Practices:
- Keep membranes in original sealed packaging until ready for installation.
- Store in a cool, clean, dry environment — avoid exposure to direct sunlight, freezing temperatures, or excessive heat.
- Handle with care — avoid bending, dropping, or impact damage.
Goal:Prevent deterioration before the membrane ever enters service.
② System Shutdown & Preservation Procedures
When: After installation & testing, or during operational downtime
If downtime follows trial operation：
If the RO system will not be placed into continuous service immediately after testing or operation, follow the appropriate preservation procedure based on downtime duration.
Short-Term Shutdown (less than 48 hours)
- Shut down per standard procedure.
- Low-pressure flush at shutdown.
- Flush every 24 hours to prevent microbial growth.
Long-Term Shutdown (more than 48 hours)
- Shut down and flush with RO permeate to remove feedwater and air.
- Fill vessels and piping with RO permeate; close all valves.
- Flush daily if the temperature is above 20 °C, and every two days if it is 20 °C or below.
- If flushing isn’t possible: circulate 1–1.5% sodium bisulfite solution (RO permeate-based) through the membranes, expel air, and
close all valves.
- Check solution pH weekly; replace if below 3.
- Maintain temperature between 5 and 45 °C; avoid freezing conditions.
Goal: Prevent microbial growth and chemical degradation during system downtime.
③ Operational Maintenance — Inspection, Pretreatment & Cleaning
When:During daily system operation
Routine Inspection
- Look for cracks, surface wear, or loose fittings that may cause leaks.
- Monitor operating pressure, flow rate, and pressure differential between feedwater and concentrate stream.
Pretreatment Control
- Maintain pH, temperature, turbidity, and residual chlorine within membrane limits.
- Use scale inhibitors (adjust based on water analysis) to control calcium/magnesium scaling.
- Ensure pre-filtration removes suspended solids, colloids, and organic matter before RO stage.
Timely Cleaning to Minimize Fouling
Common foulants:
- Suspended solids / colloids
- Organic matter
- Microorganisms (biofouling)
- Inorganic scaling (precipitated salts)
Initiate chemical cleaning when:
- Permeate flow decreases by more than 15% from initial performance.
- Salt passage increases by more than 10% from initial performance.
- Pressure differential increases by more than 15% from the initial value.
Cleaning Guidelines:
- Match cleaning agents to fouling type (scaling, organic, biological).
- Control cleaning chemical concentration, temperature, and contact time according to membrane manufacturer’s instructions.
- Clean promptly before fouling becomes irreversible.
Goal:Maintain efficiency, prevent irreversible damage, and extend service life.
④ Maintenance Benefits at a Glance
Correct storage - Prevents premature deterioration
Shutdown preservation - Reduces microbial contamination risk
Regular inspection - Enables early problem detection
Effective pretreatment - Minimizes fouling and scaling
Timely cleaning - Restores performance and extends membrane lifespan
Conclusion
By combining correct storage, regular monitoring, robust pretreatment, and timely cleaning, you can extend the working life of your RO membranes, safeguard water quality, and protect your operational investment.