1.Sand filter

After the treatment of tap water by the municipal water plant, although most of the suspended impurities have been removed, there are still a small amount of suspended matter, turbidity and other indicators that can not meet the requirements of the reverse osmosis film for the water quality of water entering the water. In order to make the intake turbidity of the reverse osmosis film less than 1 NTU, a sand filter is set at the front of the system. The sand filter is a granular material that passes the original water through a certain thickness and effectively removes the turbidity of the water. It is a process of water purification. When too many impurities are trapped in the filter layer, the pores in the filter layer are blocked, and the resistance of the interception flow increases. The filtration speed becomes smaller. In order to restore the original filtration speed, it must be washed back with water periodically, and the impurities accumulated in the pores of the filter material must be washed off.

2.Activated carbon filter

After municipal tap water is sterilized, residual chlorine in the end of the pipe network is a strong oxidant. If it is not removed, it will cause irreversible damage to the resin and reverse osmosis membrane. The residual chlorine can be removed very thoroughly by adsorption with activated carbon. Activated carbon not only has strong adsorption capacity, but also has a large adsorption capacity. The main reason is its porous structure, which has a specific surface area of 500-700 M2 / G. It is precisely because activated carbon has a developed West hole structure and a huge specific surface area, it can completely absorb residual chlorine and some organic matter in water, and it also has a good removal effect on Chroma and odor.

3.Softener

The softener is a device used to reduce or basically eliminate the hardness of the original water. The residual hardness of the effluent can be reduced to below 0.03 mmol/L(in 1/2 Ca2 +). Here, we use sodium cationic exchange resin(RNa) for softening, and we exchange cations(such as Na +, H +) in the resin with cations to exchange calcium and magnesium ions contained in the water. This process is called the softening process of water. The Ionic reaction formula of this process is as follows:
Ca2 + +2 RNa = R2Ca +2 Na +
Mg2 + +2 RNa = R2Mg + 2Na +

From the above, Ca2 + and Mg2 + in the water are replaced by Na + in the RNa-type resin and remain in the resin, causing the ion exchange resin to change from RNa-type to R2Ca or R2Mgresin.
During the softening process, when the hardness of the water flowing through the resin layer exceeds a certain specified value and the water quality does not meet the standard requirements for water quality, the ion exchange resin in the exchanger will be regarded as "deactivated" and no longer play a softening effect. At this time, In order to restore the exchange capacity of ion exchange resins, ion exchange resins are usually reclaimed using industrial salt aqueous solutions(5-10 %), also known as reduction, that is, calcium and magnesium ions adsorbed in the resin are used with sodium ions in salt. Replacement. Its ion reaction formula:
Na + + 2RCa2 + = R2Na + 2Ca +
Na + + 2RMg2 + = R2Na + 2Mg2 +