Avoid “Membrane-Damaging” Pitfalls: The Right Way to Use RO Reverse Osmosis Membranes

RO Reverse Osmosis Membrane Usage Guide: Don't Let Improper Operation Ruin It! In water treatment, RO reverse osmosis membranes are the “core component.” Whether for drinking water or industrial water treatment, their efficient filtration is indispensable. Yet many users often damage membrane performance, shorten lifespan, or even compromise water quality due to incorrect handling. Today, we'll break down the proper methods for using RO reverse osmosis membranes to help you avoid these “membrane-killing” pitfalls!

I. Beware! These Operational Errors Can Directly Damage RO Reverse Osmosis Membranes

While RO reverse osmosis membranes appear stable, minor operational oversights can lead to premature failure. Issues typically fall into three categories:

1. Residual Gas Not Fully Vented Under High Pressure Causes “Gas Hammering” Damage

When residual gas remains in the system during high-pressure operation, it creates a “gas hammering effect,” directly impacting the membrane elements and causing physical damage. This typically occurs in two scenarios: Gas Not Fully Vented During Restart: After draining the system, if air isn't completely purged before rapidly increasing pressure during restart, the residual gas will violently impact the membrane under high pressure. Correct procedure: Operate initially at 2–4 bar low pressure. Once no bubbles appear in the flowmeter (indicating air exhaustion), gradually increase pressure. Poor pipe sealing allowing air ingress: If connections between pretreatment equipment (e.g., microfilters) and the high-pressure pump leak or are poorly sealed, insufficient pretreatment feedwater (e.g., reduced flow due to microfilter clogging) can create a vacuum in the piping, drawing in air. Solution: Promptly clean or replace clogged microfilters, inspect and repair leaking pipes to ensure no air enters during operation.

2. Incorrect shutdown methods lead to membrane scaling and contamination

Many mistakenly believe “shutdown = direct power cut,” but this creates hidden risks for RO membranes, primarily due to two issues:

- Pressure reduction without flushing causes scaling on the concentrate side: During operation, inorganic salt concentrations on the concentrate side far exceed those in the feedwater. If pressure is rapidly reduced during shutdown without thorough flushing, these salts adhere to the membrane surface. Over time, this forms scale that blocks pores and reduces filtration efficiency. Rinsing with chemically treated water: Some users rinse membrane elements with pretreatment water containing chemical additives. This practice is inadvisable—chemically treated water may react with the membrane during downtime or leave residues that contaminate the membrane, compromising subsequent water quality.

3. Inadequate disinfection and maintenance allow microorganisms to “colonize” the membrane

Composite polyamide is a common material for RO membranes, but it has a weakness: poor resistance to residual chlorine. If chlorine or other disinfectants are not properly dosed during use, coupled with insufficient attention to microbial contamination, bacteria and microorganisms in the water will multiply on the membrane surface, forming a biofilm. This not only clogs the membrane pores but also leads to microbial contamination in the treated water (this is the root cause of many manufacturers' purified water failing microbial standards).

II. Untimely or Incorrect Cleaning Can Cause “Cliff-Like” Decline in Membrane Performance

During operation, RO membranes experience normal performance degradation. However, contamination-induced decline is often more severe and irreversible. Failure to clean promptly or using incorrect cleaning methods can halve the membrane's lifespan. First Understand: The 3 Common Types of RO Membrane Contamination

Different contaminants exhibit distinct symptoms and causes. Learning to identify them enables targeted cleaning:

Chemical Scale Contamination: Primarily caused by high concentrations of calcium, magnesium, or silica ions in the feedwater. Prolonged operation leads to the formation of calcium carbonate, calcium sulfate, or silica scale on the membrane surface. Symptoms include: reduced system water production, increased inlet-outlet pressure differential, and deteriorated treated water quality.

Organic/Colloidal Contamination: Humic acids, proteins, and colloidal particles in the feedwater adhere to the membrane surface, forming a “fouling layer.” This reduces membrane permeability, decreases water production, and makes rapid recovery after cleaning difficult.

Microbial Contamination: As mentioned earlier, biofilms formed by microbial proliferation not only reduce water production but also cause off-odors in the treated water, microbial overgrowth, and may leave slimy biological residues on the membrane surface.

Remember: Pollution identification requires “comprehensive judgment.” Relying solely on a single symptom makes it difficult to accurately determine the pollution type. It is necessary to combine the following information:

Raw water quality reports (e.g., hardness, organic content); Equipment design parameters (e.g., design water production, recovery rate); Contamination indices (SDI values reflecting suspended solids and colloids); Operational logs (recent changes in water production, pressure differential); Membrane element appearance (presence of slimy deposits or white scale); Microbial test data (microbial counts in effluent or on membrane surfaces).

Key reminder: Cleaning must be “timely + targeted”

Immediate cleaning is required upon detecting these signals:

① Product water flow rate decreases by over 10% from initial value;

② Inlet/outlet pressure differential increases by over 15% from initial value;

③ Outflow water quality (e.g., conductivity) deteriorates significantly.

Cleaning precautions: Use specific cleaning agents for different contaminants (e.g., acidic agents for chemical scale, alkaline agents for organic fouling) to prevent membrane damage. Control cleaning temperature and pressure, strictly follow the membrane manufacturer's cleaning guidelines, and avoid improper operation.

Final Summary: Proper RO Membrane Use Boils Down to Three Core Points

1. Purge air before operation and gradually increase pressure: Eliminate the “air hammer effect” to protect the membrane's physical structure;

2. Thoroughly flush before shutdown without using chemically treated water: Prevent scaling and chemical contamination to extend membrane lifespan;

3. Regular disinfection + timely targeted cleaning: Prevent microbial contamination and slow performance degradation.

As the “core consumable” in water treatment, RO membranes deliver maximum value only through proper usage. May this guide help you avoid common pitfalls, ensuring longer stable operation and more reliable water quality!