Pretreatment before reverse osmosis membranes

Why pre-treatment is required before entering the reverse osmosis membrane

As a new type of pure physical desalination process, reverse osmosis equipment has high requirements for feed water due to the structure, material and desalination mechanism of the reverse osmosis membrane element.

Learn more about the requirements of reverse osmosis membranes for water quality.

Reverse osmosis pretreatment plays an irreplaceable role in this. When pretreatment is not done properly, the reverse osmosis feed water quality is seriously substandard and too long, it can lead to irreversible physical and chemical damage to the reverse osmosis membrane elements, greatly shortening the service life of the reverse osmosis membrane elements.

Pre-treatment equipment

The pre-treatment equipment consists of five units: raw water pressurisation pump, quartz sand filter, activated carbon filter, and automatic water softener and fine filter.

1. Raw water booster pump

When the raw water is tap water, the pressure of tap water should be greater than the total resistance of water flow (water pressure difference) of quartz sand filter, activated carbon filter, automatic water softener and fine filter, and can meet the requirements of water pressure into the reverse osmosis host, so it is necessary to set the pressurization pump to achieve the water pressure requirements.

2. Quartz sand filter

Because the turbidity of tap water is generally 3 to 5 degrees, the water also contains a small amount of suspended matter and sediment. Therefore, it is necessary to set up a quartz sand filter to reduce the turbidity of the water by no more than 1 degree and to prevent blockage of the reverse osmosis membrane.

3. Activated carbon filter

Mainly to remove free chlorine and organic matter in the water, to prevent free chlorine oxidation of the reverse osmosis membrane. It also removes odour from the water and improves the taste of pure water for drinking.

4. Automatic water softener

When the process water passes through the automatic sodium ion exchanger, cations such as Ca2+ and Mg2+ in the water are exchanged with Na+ in the exchanger to reduce the hardness of the water and soften the water.

5.  Cartridge Filter Housing

This filter is the last filtration device before the tap water enters the membrane, it can effectively remove the sand filter, carbon filter is not clean greater than 5μm material, can intercept the sand filter, carbon filter loss of broken sand and activated carbon powder, etc., so as to effectively protect the RO membrane from or less contaminated.

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