... remove the pigment in the water, smell, a large number of chemical and biological organisms, reducing the residual value ... Third stage pretreatment (Resin softener)Cationic resin used for water softening, primarily to remove hardness of water. The hardness of water is a ... raw water hardness ions through the resin layer, the water of the Ca2 +, Mg2 + was exchanged resin adsorption, and other objects at ...