Analysis of Reverse Osmosis Membrane Removal Performance

I. Removal Rates of Reverse Osmosis Membranes for Different Contaminants

With an ultra-fine pore size of 0.0001 microns (approximately one-millionth the diameter of a human hair), reverse osmosis (RO) membranes can efficiently remove various contaminants from water, making them one of the most precise water treatment technologies available today.

Ion Removal Performance

Overall Desalination Rate: RO membranes achieve a total ion rejection rate of approximately 99%, including:

High-Valence Ions (such as Ca²⁺, Mg²⁺, SO₄²⁻, etc.): Rejection rate approaching 100%

Monovalent Ions (such as Na⁺, Cl⁻, etc.): Rejection rate of approximately 92%

Heavy Metal Removal: Removal rates ≥ 99% for lead, cadmium, arsenic, and other heavy metals

Organic Removal Performance

Macromolecular Organics (molecular weight > 100 Da): Removal rate > 90%

Pesticide Residues (such as DDT, BHC, etc.): Removal rate 95–99%

Pharmaceutical Residues (antibiotics, hormones, etc.): Removal rate 90–98%

Disinfection Byproducts (such as trihalomethanes THMs): Removal rate 95–99%

Microplastics: Removal rate up to 90%–99%, making it one of the most effective household filtration technologies

Microorganism Removal Performance

Bacteria (such as E. coli): Removal rate 99.99%

Viruses (such as Norovirus): Removal rate ≥ 99.99%

II. Typical Water Quality Parameters After Reverse Osmosis Treatment

Water Quality Parameter

Treatment Performance

Typical Value Range

TDS    Reduced by over 99%    0–50 ppm    

Conductivity    Significantly reduced    < 50 μS/cm (25°C)    

Hardness    Almost completely removed    Approaching 0    

pH    May become slightly acidic    Slightly lower than feed water    

Mineral Content    Almost free of minerals    Approaching pure water    

Microbiological Indicators    Bacteria/viruses almost completely removed    Not detected    

III. Key Factors Affecting Removal Performance

Contaminant Characteristics

Ion Valence: Desalination rate increases with ion valence; di- and trivalent salts exhibit higher rejection rates than monovalent salts

Molecular Size: Desalination rate increases with molecular diameter

Dissolved Gases: Soluble gases such as CO₂ and SO₂ readily permeate in their free state and are not effectively removed

Operating Conditions

Operating Pressure: Higher pressure typically improves desalination rate, but excessive pressure may accelerate membrane compaction

Feed Water Temperature: Increased temperature raises permeate flux but may reduce desalination rate; optimal temperature is 20–25°C

Feed Water pH: pH affects membrane surface charge and ion speciation, with optimal desalination typically achieved in the pH 6–8 range

Recovery Rate: Higher recovery rates increase feed-side concentration, potentially leading to scaling and reduced desalination

System Maintenance Factors

Pretreatment Quality: Inadequate removal of suspended solids and organics accelerates membrane fouling

Chemical Cleaning: Regular cleaning (every 3–6 months) is required to maintain membrane performance

Microbiological Control: Residual chlorine must be strictly controlled (< 0.05 ppm) to prevent membrane oxidation

IV. Performance Maintenance Strategies in Practical Applications

Pretreatment Optimization:

Multi-media filtration for suspended solids removal

Activated carbon adsorption for organics and residual chlorine removal

For high-hardness water, softening pretreatment is recommended

Operating Parameter Monitoring:

Real-time monitoring of critical parameters including pressure, flow, and temperature

Investigate promptly when permeate flow declines by 10% or desalination rate decreases significantly

Cleaning and Maintenance:

Regular physical flushing (backwashing) and chemical cleaning

Thorough flushing required during shutdown to prevent scaling on the concentrate side

Rinse new membranes and activated carbon when replacing filter cartridges

V. Comprehensive Evaluation of Technical Characteristics

Advantages

Thorough Purification: Almost completely removes all types of contaminants; permeate approaches pure water quality

Safe and Reliable: Excellent removal of bacteria and viruses

Broad Applicability: Suitable for high-pollution water sources, seawater desalination, and other demanding conditions

Limitations

Nearly Free of Minerals: Mineral supplementation should be considered for long-term consumption

Relatively High Energy Consumption: Requires high-pressure pump providing 0.5–4 MPa operating pressure

Significant Wastewater: System recovery rate typically 50%–75%, generating 25%–50% concentrated brine

With its outstanding removal performance, reverse osmosis technology has become the preferred solution for applications including drinking water safety, medical water, and ultrapure water production for the electronics industry. In practical applications, reasonable system parameter design and enhanced operation and maintenance based on source water quality and usage requirements are essential to fully realize its performance advantages.

The above information has been compiled by the editorial team of Qisheng Membrane Separation Technology Co., Ltd. regarding the removal performance of reverse osmosis membranes. For further inquiries, please feel free to contact us!