RO Reverse Osmosis Membrane

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• What is osmosis?

• What is reverse osmosis (RO)?

Research and Technological Origins

• Origin: Reverse osmosis technology wasn’t originally developed for household water purification. It was first invented in the 1950s by two scientists from UCLA, Sidney Loeb and Srinivasa Sourirajan.
• Driving Force: The initial development was mainly driven by government projects, aiming to create an efficient and reliable seawater desalination and wastewater recycling technology for the U.S. Navy and NASA to solve drinking water problems for submarines and space missions.
• Technology Civilianization: With the continuous improvement of the technology and a reduction in costs, RO technology gradually found applications in industrial and civilian sectors starting in the 1970s, becoming the most recognized and effective deep purification technology for drinking water worldwide.
  
  

Key Performance Indicators for a High-Quality RO Membrane

Summary: A Top-Tier RO Membrane = High Salt Rejection Rate (≥98%) + Reasonable Recovery Rate (~50-75%) + Moderate Flux (e.g., 100 GPD) + Top-Brand Membrane (e.g., DuPont) + NSF/ANSI 58 Certification.

Usage and Maintenance Guide

1. Pre-filtration is Crucial: The RO membrane is highly delicate. It must rely on the PP cotton filter and activated carbon filter (composite filter) for pre-treatment, removing sand, rust, residual chlorine, etc. Residual chlorine can irreversibly oxidize and damage the polyamide layer on the RO membrane, causing a permanent decrease in salt rejection rate.
2. Keep the System Powered On: The RO system’s booster pump requires power to operate. If turned off or powered down, no water will be produced. After long periods of inactivity, refer to the manual for flushing instructions before restarting.
3. Regular Flushing: Before every water production cycle, the system typically performs a brief auto-flush to clear impurities concentrated on the membrane surface. If the system hasn’t been used for an extended period (e.g., over 24 hours), it’s recommended to manually flush the system for 2-3 minutes.
4. Replace Pre-filters on Time: Follow the recommended replacement cycle (e.g., your product: composite filter every 6 months). A failed pre-filter cannot protect the RO membrane, leading to rapid membrane clogging or damage. The cost of replacing an RO membrane is far greater than replacing pre-filters.
5. Monitor Wastewater Ratio: Proper wastewater discharge is essential for ensuring the longevity of the RO membrane. Claims of "zero waste" are often made at the cost of the membrane's lifespan.
6. Maintenance After Long-Term Inactivity: If the system hasn’t been used for more than a week, it’s recommended to drain the water stored in the tank. If unused for over a month, a complete flush and disinfection are necessary. If required, replace the RO membrane before restarting.
   
   

Why Must a New RO Membrane (or Replaced Membrane) Be Flushed Before Use?

1. Removal of Protective Liquid (Core Reason):

1. To protect the RO membrane during storage and transportation, manufacturers inject food-grade protective liquid (usually 1% sodium bisulfite solution, an antioxidant and bactericide). This liquid, though harmless to humans, has a faint sulfur-like smell and can affect the taste of water, making it undrinkable.
   
   

2. Activate Membrane Pores and Stabilize Performance:

1. In its dry state, the polyamide desalting layer of the RO membrane is in a “dormant” state. Flushing allows water molecules to fully permeate and pass through the membrane pores, "waking" it up to its optimal working state.

1. Initial salt rejection rates and water production might fluctuate slightly, but adequate flushing helps stabilize its performance quickly.
   
   

3. Release Air and Check Seals:

1. Flushing removes air trapped in the membrane housing and pipes, ensuring the system is filled with water and avoiding air impact on the pump and membrane elements (water hammer). It’s also a good opportunity to check for any leakage in the connections.
   
   

When is Flushing Complete and Safe to Use?

• Scientific Indicator: The TDS value of the output water stabilizes and falls within an acceptable range:
  
  
  • Start the water production mode and collect water from the purified water tap.
  • Use the TDS meter or view the OUT ppm on the machine to monitor real-time readings.
  • The initial TDS will be high (close to the raw water TDS), but it will drop steadily during flushing.
  • When the TDS reaches a lower level (e.g., below 50 ppm, ideally close to 20 ppm or lower) and stabilizes, it means the protective liquid has been fully flushed out, and the membrane is working properly. The water can then be safely consumed.
    
    

• No odor, normal taste:
  
  
  • Check the water smell—it should have no chemical or foul odor.
  • Taste the water—it should be refreshing and sweet, with no strange flavor.
    
    

• Typical flushing time is 30 minutes to 1 hour, or produce and discard water equivalent to 3-5 full tanks (e.g., your product has a 1.3L tank).
  
  
  • The Initial Unboxing and New Machine Cleaning process in your product manual requires flushing with water equivalent to at least 4 source water tanks, based on this principle.
    
    

Flushing Operation Precautions:

• Do not drink flushing water: Never drink the purified water produced during the flushing stage. Always discard it; it can be used for watering plants, mopping, or cleaning.
• Ensure wastewater flow is unobstructed: Wastewater (concentrated water) will flow at a high rate during flushing, so ensure the drainage system is clear and connected to the sewer.
• Maintain normal water pressure: During flushing, ensure the incoming water pressure is normal to ensure adequate water flow for membrane cleaning.
• Be patient: Don’t shorten the flushing time to save water. Adequate flushing is essential for ensuring the RO membrane performs optimally and lasts longer.