How to select Pre-treatment filters and Maintain

I. Sand filter

It can be used to remove suspended impurities with large particle size in water, prevent these impurities from entering into activated carbon filter and cover the surface of activated carbon, so that the capillary structure of activated carbon loses the ability to absorb impurities in water.

As the retained solid impurities increase, the pressure of sand filter increase while the flow rate decrease. Thus it is necessary for the backwash of sand filter when the pressure increase to the certain level. During the backwash, some fins sand is flushed out so should add some sand. After repeated backwash, the degree of crushing increases, as the left silt gradually increase, the sand filter should be replaced.

II. Activated carbon filter

It can be used to remove macromolecular organic matter, iron oxide and residual chlorine. Residual chlorine and will break the membrane structure to cause the reverse osmosis membrane ineffective.

The activated carbon filter utilizes abundant activated carbon pores to adsorb and filter macromolecular organic matter, residual chlorine, iron oxide and other colloids in water. This adsorption is irreversible, that means activated carbon has a certain saturation adsorption capacity. After the adsorption is saturated, the activated carbon loses its adsorption performance and cannot be removed by backwash. In addition, after activated carbon adsorbs organic matter, it provides bacteria with rich nutrients, allowing bacteria to multiply in activated carbon filters, and increases the microbial content of water through activated carbon filtration.

Thus should backwash the activated carbon filter regularly before the saturation of activated carbon to remove a large number of bacterial colonies and suspended solids on the surface of the activated carbon. After the activated carbon is saturated, it should be replaced with new activated carbon immediately, otherwise it will cause irreparable damage to the reverse osmosis membrane.

III. Water softener

It is used to remove calcium and magnesium ions from the water to soft the water. If there is no water softener while the concentration of calcium and magnesium ions increase, will form the water-soluble precipitates on the surface of the reverse osmosis membrane to cause the block of membrane and reduce service life of it.

Normally the resin used for water softener is usually sodium-type cation exchange resin, as the resin is exchanged and saturated and then regenerated by salt. After years of operation, the broken degree of resin is becoming more and more severe and lose the softening gradually. Especially when the activated carbon be saturated and have not been replaced on time. The iron, organic matter and residual chlorine in the raw water will directly enter the water softener, resulting in resin poisoning. Once the resin is poisoned, it cannot be regenerated and need to be replaced.

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