Cleaning Methods and Formulas for Reverse Osmosis (RO) Membranes

(Recommended for operation by professional technicians only)

I. Cleaning Formulas

1. Formula 1 (For Inorganic Scale):
   • Composition: 0.2% Hydrochloric Acid (HCl) solution.
   • pH Level: 2.0 – 3.0.
   • Optimal Temperature: 35°C.
2. Formula 2 (For Sulfate and Organic Colloid Fouling):
   • Composition: 0.1% Sodium Hydroxide (NaOH) + 0.025% Sodium Dodecyl Benzene Sulfonate (SDBS).
   • pH Level: 12.0.
   • Optimal Temperature: 30°C.

II. Operating Procedures

1. Preparation of Materials

• Hydrochloric Acid (36%): 4 bottles (500g per bottle).
• Sodium Hydroxide (NaOH): 4 bottles (500g per bottle).
• Purified Water: 100 kg (Note: Use of ozone-treated purified water is strictly prohibited).
• pH Test Paper: 1 pack (Range: 1–14).

2. Chemical Preparation (Example: Formula 1)

• Calculate the weight of water required to fill the cleaning tank to 2/3 capacity.
• Add the chemicals to the purified water according to the specified ratio. Stir thoroughly until completely dissolved, then pour into the cleaning tank.
• For the 0.2% HCl solution, the initial pH will be approximately 1–2. While stirring, continue to test with pH paper until the standard value of 2–3 is reached.
• Note: If conditions allow, it is best to maintain the cleaning solution temperature between 35–40°C.

3. Cleaning Process

• Valve Configuration:
  • Open: The circulation valves for both concentrate (brine) and permeate (product water) to allow flow back into the cleaning tank.
  • Open: The inlet valve between the cleaning tank and the cleaning pump.
  • Close: The concentrate discharge (drain) valve and the permeate valve leading to the pure water storage tank.
• Operation: Set the electrical control system to Manual Mode. Start the cleaning pump to begin the circulation.
• Duration: Circulate for 1–2 hours.
• Evaluation: Observe the water in the cleaning tank. If the water becomes turbid, it indicates a successful cleaning effect; if the water remains clear, the effect is poor.
• Rinsing: After the chemical circulation is complete, drain the cleaning solution from the tank. The residual chemicals inside the membrane must be flushed out for approximately 1–2 hours. During this time, fully open the concentrate discharge valve and the permeate discharge valve.
• Return to Service: Only put the system back into normal operation after rinsing for 1–2 hours to ensure all chemical residues are removed.

Note:

Generally, Formula 1 (Acid Wash) is selected for standard cleaning. The operating method for Formula 2 (Alkaline Wash) is identical to Formula 1.