Introduction to the main points of Reverse osmosis membrane pollutant cleaning

The main points of reverse osmosis membrane cleaning

The main points of cleaning are high flow rate, low pressure and cleaning frequency.

(1) Cleaning flow rate:

When the device is running, particulate pollutants with high adhesion are gradually accumulated on the surface of the membrane. If the flow rate during cleaning is equal to or lower than the flow rate during operation, it is difficult to clean these contaminants from the membrane element. Therefore, a higher flow rate should be used during cleaning than during normal operation (generally, it can be considered as 1.2 times the flow rate of concentrated water during normal operation). In fact, the pressure difference between the two ends of the membrane element is proportional to the inlet water flow. The pressure difference of a single membrane element is not allowed to exceed 0.7 bar. Therefore, Hyde Energy has strictly limited the maximum inlet flow of a single membrane element. Follow the following rules when cleaning.

(2) Cleaning pressure

In normal high-pressure operation, the pressure directly acts on the membrane surface vertically, so that the influent water passes through the membrane surface to obtain water, and the contaminants are also pressed to the membrane surface. Therefore, if the same high pressure is used during cleaning, the contaminants will be accumulated on the surface of the membrane, and the cleaning effect will be reduced. When cleaning, use low pressure and high flow rate as much as possible to increase the horizontal shearing force to flush the contaminants out of the membrane element. The cleaning pressure is generally recommended to be controlled below 3.0bar. If it is below 3.0bar, it is difficult to meet the flow requirements, control the inlet water pressure as much as possible, and use no water as the standard. Generally, the inlet water pressure cannot be greater than 4.0 bar.

(3) Cleaning frequency

When conditions permit, it is recommended to clean the system frequently. Increasing the number of cleanings is more effective than extending the time of one cleaning. The general cleaning frequency is recommended to be more than once a day. According to the specific situation, customers can specify the frequency of cleaning by themselves. The cleaning water generally uses qualified pretreatment product water.

Cleaning steps

(1) Stop device

Slowly reduce the operating pressure and gradually stop the device. The rapid drop in pressure caused by rapid shutdown will form water hammer, which will cause impact damage to pipelines, pressure vessels and membrane elements.

(2) Regulating valve

First open the concentrated water valve fully; then close the water inlet valve; then fully open the water production valve (such as closing the water production valve after closing the system). If the water production valve is closed by mistake, the membrane element at the back end of the pressure vessel may be mechanically damaged due to the back pressure of the production water.

(3) Cleaning operation

First start the low-pressure cleaning pump; then slowly open the inlet valve while observing the flow of the concentrated water flow meter; adjust the inlet valve until the flow and pressure are adjusted to the design value; finally, slowly close the inlet valve after 10-15 minutes , Stop the water inlet pump.

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