Ultra-filtration System Membrane Cleaning

To Ultra-filtration membrane is the core element of ultra-filtration system and is often used in the mid-end treatment of ultra-pure water preparation. Since the ultra-filtration membrane removes impurities in the water by physical retention, it should be cleaned regularly to extend the service life of the ultra-filtration membrane.

The cleaning method of the ultra-filtration membrane is generally determined according to the nature of the membrane and the nature of the treated liquid. It is similar to the cleaning of reverse osmosis membranes, that is, first hydraulic cleaning, and then cleaning with different chemical detergents according to the situation.

Cleaning steps are as follows:

1) Prepare cleaning solution based on contaminants

2) Feed cleaning agent by low flow rate

- First, mix the cleaning agent by cleaning pump, and make the flow rate as low as possible; then replace the raw water in the component with the lowest possible cleaning agent pressure, that is, the pressure must be low enough that no obvious permeated water be produced.

3) Circulation

- After the raw water is replaced, the cleaning agent should appear in the reject water pipeline. At this time, the cleaning agent should be circulated back to the cleaning water tank.

4) Soak

- After the circulation is completed, stop the operation of the cleaning pump, and let the membrane elements completely soak in the cleaning solution.

- Sometimes soaking for about 1 hour is enough, but for stubborn pollutants, it is necessary to extend the soaking time, such as soaking for 10-15 hours or soaking overnight.

5) Flush membrane by high flow rate

After the soaking is completed, flush the contaminants washed by the cleaning agent under a high flow rate.

6) Rinse

- The pre-treated qualified product water can be used to rinse the cleaning agent in the system

- In order to prevent precipitation, the minimum flushing temperature is 20 degrees Celsius

- During acid cleaning process, the pH value of the cleaning agent should be checked at any time. When the acid is consumed by the dissolved inorganic salt precipitation, if the pH increases by more than 0.5, the acid should be supplemented to the cleaning tank.

- The total circulation time of the liquid should not exceed 20 minutes. After this time, the cleaning liquid may be saturated with the cleaned inorganic salt, and the contaminants will be deposited on the membrane surface again. The first cleaning liquid in the membrane system and cleaning system is discharged, and the cleaning liquid is reconfigured for acid cleaning operation.

- If the system must be shut down for more than 24 hours, the components should be stored in a 1% (weight ratio) sodium bisulfite aqueous solution.

- Before cleaning the large-capacity system, it is recommended to take out a membrane element from the system to be cleaned, and conduct a test evaluation of the cleaning effect of that membrane element.

Cleaning of the ultra-filtration membrane timely can maintain the permeation rate to extend the service life of the membrane, thus the correct cleaning method can save time and reduce the damage of membrane elements during the cleaning process.

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