Sterilization of Reverse Osmosis Composite Membrane Elements Using Bactericides

When is disinfection needed?

How to disinfect and what chemicals to use for disinfection

Bacterial control and sterilization

Rules for controlling bacterial concentration in concentrated water:

• If <4 log CFU/mL, the bacterial count is considered under control.
  

• If 4 to 6 log CFU/mL, attention should be paid.
  

• If 6 log CFU/mL is reached or the bacterial count increases, the problem should be addressed.
  

Note: 4 log = 10,000 = 10⁴ 6 log = 1,000,000 = 10⁶

• Disinfection: refers to a 99.9% reduction in bacteria (3 logs)

• Sterilization: refers to a 99.9999% reduction in bacteria (6 logs)
  

• Sterilization: refers to a 99.9999999% reduction in bacteria (9 logs)
  

• Bioinhibitors: inhibit bacterial growth
  

• Slime destroyers: destroy the biofilm
  

Characteristics of reverse osmosis chemical sterilization

• Kills bacteria

• Removes biofilm
  

• Minimal contact time
  

• Minimal harm to membranes
  

• Non-toxic and environmentally friendly
  

• Safe to operate
  

• Reasonable price
  

What are some disinfectants for disinfecting reverse osmosis composite membrane elements?

Formaldehyde

• Dosage: 0.1~1.0%

• In the United States, this agent is considered to have some toxicity.
  

• For new membranes, it must be used only after 24 hours of operation, otherwise it will lead to irreversible water flux loss.
  

• Can be used as a disinfectant solution that can be stored for a long time.
  

Sodium bisulfite

• Dosage: 500ppm, use 30~60ppm

• A 1.0% solution can be used for long-term storage.
  

Isothiazolinone

• Dosage: 15~25ppm

• Can be used as a disinfectant solution for long-term storage.

Hydrogen peroxide/peracetic acid

• Dosage: 0.2% (sum of the two compounds)

• pH: 3~4 (high pH values will cause membrane oxidation)

• Temperature: 25℃ (maximum)

• The presence of iron or excessive metals can cause CPA membrane oxidation.

• Circulate repeatedly for 20-30 minutes / soak for 2 hours / then rinse.
  

• A contact time of up to 4 hours may be required to disrupt biofilms.
  

• It is an effective and rapid oxidizing bactericide.
  

• It is relatively effective in disrupting biofilms.
  

• This bactericide is not suitable for long-term storage.
  

KY-221

• Dosage: 50 PPM (shock sterilization)

• Dosage: 0.5 PPM (continuous sterilization)

• Non-oxidizing bactericide, with rapid and effective sterilization.

• It has a good stripping effect on bacterial slime.

• Compatible with all membrane elements.

• Wide operating pH range, good biodegradability, and environmentally friendly.

• 30 minutes each time, once every two weeks, is sufficient for good results.

• Can be added during normal operation without stopping the system.

• KY-221 reverse osmosis-specific bactericide can also be used as a shutdown cleaning agent for reverse osmosis systems.

• Suitable for long-term storage disinfection.

Note: This product is developed, researched, and produced by Kaiyuan Hengye.

Acetic Acid Film Disinfectant

Free Chlorine

• Dosage: When the pH is 5-6, add continuously at a dose of 0.1-1.0 ppm.

• Dosage: Once every two weeks, use 5 ppm for 1 hour each time.
  

• Reaction with corrosion products (iron) may cause abrasive damage.
  

• If iron is present, it is recommended to use a chloramine solution with a maximum concentration of 10 ppm instead.
  

• A solution of 0.1-1.0 ppm can be used as a disinfectant for long-term storage.
  

Formaldehyde

• Dosage: 0.1-1.0%

• Can be used as a disinfectant for long-term storage.

Isothiazolinone

• Dosage: 15-25 ppm

• Can be used as a disinfectant for long-term storage.

KY-221

• Dosage: 50 PPM (shock disinfection)

• Dosage: 0.5 PPM (Continuous Sterilization)

• Non-oxidizing bactericide, providing rapid and effective sterilization.

• Excellent removal effect on bacterial slime.

• Compatible with all membrane elements.

• Wide operating pH range, good biodegradability, and environmentally friendly.

• 30-minute dosing every two weeks is sufficient for good results.

• Can be added during normal operation without system shutdown.

• KY-221 reverse osmosis-specific bactericide can also be used as a shutdown cleaning agent for reverse osmosis systems.

• Can be used as a sterilizing solution for long-term storage.

Note: This product was developed, researched, and manufactured by Kaiyuan Hengye.