DM Water Plant Manufacturer: Two-Bed & Mixed-Bed

Water passes through a cation resin that exchanges dissolved cations for hydrogen ions, then an anion resin that exchanges anions for hydroxide ions. The hydrogen and hydroxide combine to form water, leaving the dissolved ionic load removed. A degasser between the two beds strips carbon dioxide and reduces the load on the anion resin.

A two-bed plant has separate cation and anion vessels in series. A mixed-bed unit holds both resins in one vessel and behaves like many two-bed stages in series, producing much lower conductivity. Mixed beds are normally used as a polishing stage after a two-bed plant or after RO.

The cation resin is regenerated with acid (hydrochloric or sulphuric) and the anion resin with caustic soda. Each regeneration follows the same sequence: backwash, regenerant injection, slow rinse to displace the regenerant, and a fast rinse until the outlet water is back within specification.

A well-operated two-bed plant typically delivers conductivity in the low single or double digits of µS/cm. Adding a mixed-bed polisher takes it below 1 µS/cm, which is what high-pressure boilers, pharmaceutical and laboratory applications usually require.

Where feed water TDS is high, usually yes. RO removes the bulk of the dissolved solids so the resin only polishes what remains, which cuts acid and caustic consumption and regeneration frequency substantially.