Step-by-step low pH and high pH chemical washing guide to restore permeate flow rates and salt rejection performance in industrial RO systems.

CIP Chemical Cleaning Procedure for DOW & Hydranautics RO Membranes

> Direct Answer: Clean-In-Place (CIP) is a chemical recirculation process designed to strip scale, silt, and biofilm deposits from spiral-wound Thin-Film Composite (TFC) RO membranes. A complete CIP requires a two-stage procedure: Stage 1 (Low pH 2.0–3.0 with Citric Acid) to dissolve calcium carbonate and iron oxide scales, followed by Stage 2 (High pH 11.0–12.0 with NaOH + EDTA) to dissolve organic fouling, silica, and bio-slime.

Stage 1: Acid Cleaning (Inorganic Scale & Metal Oxides)

Target Fouling: Calcium carbonate (CaCO_3), barium sulfate, calcium phosphate, and iron oxide deposits.
Chemical Solution: 2.0% Citric Acid (C_6H_8O_7) or 0.2% Hydrochloric Acid (HCl).
Target pH: 2.0 – 2.5.
Temperature: 25°C to 35°C (never exceed 40°C).
Recirculation: Recirculate at low pressure (20–40 PSI) for 45 minutes, then soak for 60 to 90 minutes.

Stage 2: Alkaline Cleaning (Biofilms, Silt & Organic Slime)

Target Fouling: Biofilm growth, dead microbial biomass, natural organic matter (NOM), and colloidal silt.
Chemical Solution: 0.1% Sodium Hydroxide (NaOH) + 0.1% Sodium Salt of EDTA (disodium/tetrasodium).
Target pH: 11.0 – 11.8.
Temperature: 30°C to 35°C.
Recirculation: Recirculate at low pressure for 45 minutes, then soak for 60 to 120 minutes until the wash solution turns amber or turbid.

Critical Safety & Operating Precautions

1. Always use pure RO permeate water to formulate chemical wash solutions. Never use raw or municipal water.

2. Recirculation Pressure: Keep pressure strictly below 40 PSI (2.8 bar) during CIP to prevent permeate production during cleaning.

3. Rinse to Drain: Always flush wash solutions directly to drain until pH returns to neutral (6.5–7.5) before routing permeate back to clean water storage tanks.

CIP Chemical Cleaning Procedure for DOW & Hydranautics RO Membranes

Stage 1: Acid Cleaning (Inorganic Scale & Metal Oxides)

Target Fouling: Calcium carbonate (CaCO_3), barium sulfate, calcium phosphate, and iron oxide deposits.

Chemical Solution: 2.0% Citric Acid (C_6H_8O_7) or 0.2% Hydrochloric Acid (HCl).

Target pH: 2.0 – 2.5.

Temperature: 25°C to 35°C (never exceed 40°C).

Recirculation: Recirculate at low pressure (20–40 PSI) for 45 minutes, then soak for 60 to 90 minutes.

Stage 2: Alkaline Cleaning (Biofilms, Silt & Organic Slime)

Target Fouling: Biofilm growth, dead microbial biomass, natural organic matter (NOM), and colloidal silt.

Chemical Solution: 0.1% Sodium Hydroxide (NaOH) + 0.1% Sodium Salt of EDTA (disodium/tetrasodium).

Target pH: 11.0 – 11.8.

Temperature: 30°C to 35°C.

Recirculation: Recirculate at low pressure for 45 minutes, then soak for 60 to 120 minutes until the wash solution turns amber or turbid.

Critical Safety & Operating Precautions

1. Always use pure RO permeate water to formulate chemical wash solutions. Never use raw or municipal water.

2. Recirculation Pressure: Keep pressure strictly below 40 PSI (2.8 bar) during CIP to prevent permeate production during cleaning.

3. Rinse to Drain: Always flush wash solutions directly to drain until pH returns to neutral (6.5–7.5) before routing permeate back to clean water storage tanks.