Reverse osmosis plant Different pollution causes

Reverse osmosis membrane is the core element to realize reverse osmosis, and it is a kind of artificial semi-permeable membrane with characteristics made by simulating biological semi-permeable membrane. Generally made of polymer materials. Such as cellulose acetate film, aromatic polyhydrazide film, aromatic polyamide film. The diameter of the surface micropores is generally between 0.5 and 10 nm, and the permeability is related to the chemical structure of the membrane itself.

Good reverse osmosis plant membrane should have the following characteristics:

1) It should have high efficient desalination rate under high flow rate

2) It has relatively higher mechanical strength and longer service life

3) It can function under relatively lower operating pressure

4) It can withstand the influence of chemical or biochemical effects

5) Less affected by factors such as pH value and temperature

Reverse osmosis plant membrane service life

In addition to the normal attenuation of the performance of the equipment during use, the attenuation of the equipment performance due to pollution is more serious. The usual pollution mainly includes chemical fouling, organic and colloidal pollution, and microbial pollution. Different pollution exhibits different symptoms. The symptoms of membrane fouling proposed by different membrane companies are also different.

For example, when the membrane is polluted by calcium carbonate scale for one week, the main manifestation is the rapid decrease of the desalination rate, the slow increase of the pressure difference, but the insignificant change in the product water capacity. Once the membrane is cleaning by citric acid can completely restore the performance.

Identifications of pollution causes of reverse osmosis plant

To identify the type of pollution, it is necessary to comprehensively judge the raw water quality, design parameters, pollution index, operation records, equipment performance changes and microbial indicators:

1) Colloid pollution

When colloidal pollution occurs, it is usually accompanied by the following two characteristics:

A. The cartridge filter will be blocked quickly in the, especially the pressure difference increases quickly.

B. SDI value is usually above 2.5.

2) Microbial contamination

When microbial contamination occurs, the total number of bacteria in the permeated water and concentrated water of RO system is relatively high, and maintenance and disinfection are not performed as required. To prevent the damage of membrane, new membrane elements are usually soaked in 1% NaHSO3 and 18% glycerin aqueous solution and stored in a sealed plastic bag.

If the plastic bag is not broken, it will not affect its life and performance if it is stored for about 1 year. But when the plastic bag is open, it should be used as soon as possible to prevent the NaHSO3 from oxidizing in the air and adversely affecting the components.

Therefore, the membrane should be open as far as possible before use. After the equipment was tested, we used two methods to protect the film. The equipment test machine runs for two days (15-24h), and then uses 2% formaldehyde solution for maintenance.

3) Take the raw water, the original cleaning solution, and the cleaning solution, and analyze the three samples. After determining the type of contamination, can process chemical cleaning. When the type of pollution cannot be determined, generally take the steps of cleaning + disinfection + 0.1% HCl (pH 3).

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