Standard Operating Procedure (SOP) For Integrity Testing Of Membrane Modules
Installation
Install the membrane module and connect the pipelines. Place the feed pipe into purified water, and put both the retentate pipe and permeate pipe into the waste tank.
Cleaning
Start the peristaltic pump. Once the retentate pipe is filled with liquid, adjust the retentate valve to ensure the system reaches an appropriate transmembrane pressure (TMP). Measure the pH of the liquids from both the retentate and permeate pipes until both become neutral.
Wetting
Turn off the peristaltic pump. Place the feed pipe, retentate pipe, and permeate pipe into purified water. Restart the pump, and once the retentate pipe is filled with liquid, adjust the retentate valve to maintain an appropriate TMP. Allow wetting for 15 minutes. Then stop the pump and fully open the retentate valve.
Draining
Remove the feed pipe from the purified water. Place the retentate pipe and permeate pipe into the waste tank. Start the pump to drain the liquid from the feed and retentate pipes.
Integrity Test
Completely close the retentate valve and place the permeate pipe into water. Start the peristaltic pump and pump in air until TMP = 0.65 bar. Stop the pump and maintain this condition for 10 minutes.
Measurement of Air Diffusion Flow
After 10 minutes, observe whether bubbles appear at the outlet of the permeate pipe:
If no bubbles are observed → membrane integrity is acceptable.
If bubbles are observed → measure the air diffusion flow using a flowmeter or an inverted graduated cylinder filled with water. Compare the measured value with the reference specification.
Since acceptable diffusion flow values may vary by manufacturer, always refer to the product manual provided by the respective manufacturer for the final acceptance criteria.
Venting
Fully open the retentate valve to release the air.
Troubleshooting Guide: Causes and Solutions When Integrity Test Fails
1. Incomplete Wetting
Ensure the membrane is fully wetted prior to testing.
Circulate water for 5–10 minutes.
Poor wetting leads to inaccurate results.
Note: Ultrafiltration membranes have small pore sizes and high bubble points; thus, diffusion flow testing is preferred.
2. Installation Issues
(A) Ensure gaskets, module, and clamp holes are properly aligned; tighten with a torque wrench.
(B) For 0.5, 1.3, and 2.5 m² modules, use thicker gaskets to improve sealing.
(C) Replace gaskets regularly; worn gaskets lose elasticity, causing leaks and test failures.
(D) Check three-way valves, pressure gauges, and clamps for air leakage.
3. Residues of Feed, Cleaning, or Storage Agents
Residues may prevent complete wetting.
Re-clean the module, rinse thoroughly, extend rinsing time, and raise water temperature if necessary.
4. Membrane Module Defects
If the above causes are excluded, the module itself may be defective due to:
(A) Transportation damage (drop/impact).
(B) Hard particles (e.g., iron filings, foreign solids) scratching the membrane.
(C) Excessive force during installation damaging the structure.
(D) Inappropriate cleaning or storage solutions.
(E) Severe clogging and residues causing long-term damage.
Solution: If the membrane module fails integrity testing, replace it with a new module.
