DM plant, short for demineralization plant, is a water treatment system that removes all dissolved minerals and salts from water. This process is also known as deionization and is typically used in industrial applications that require ultra-pure water.

DM plants remove dissolved minerals and salts from water using a combination of ion exchange resins and a reverse osmosis system. The ion exchange resins remove dissolved ions such as calcium, magnesium, and sodium, while the reverse osmosis system removes other dissolved solids such as dissolved organic compounds.

The DM plant normally has a pre-treatment unit, a cation exchange unit, an anion exchange unit, and a mixed bed unit. Suspended solids and other impurities are removed from the water in the pre-treatment unit before the water enters the cation exchange unit. Positively charged ions such as calcium, magnesium, and sodium are exchanged with hydrogen ions in the cation exchange unit. In the anion exchange unit, negatively charged ions such as chloride, sulfate, and bicarbonate are exchanged for hydroxide ions. Mixed bed unit is composed of cation and anion exchange resins in the same tank, thus the water will be demineralized completely.

DM plants are usually applied in the industries that demand ultra-pure water, for example, pharmaceuticals, semiconductor manufacturing, and power plants. Conductivity is used to measure the quality of water produced by the DM plant, which represents the amount of dissolved salts and minerals in the water. Water produced by a DM plant may have a conductivity of less than 1 µS/cm, which is regarded as ultra-pure.

Materials commonly used in DM plants include mild steel (MS), stainless steel (SS), and fiber-reinforced plastic (FRP). The material used depends on the application, the operating conditions, and budget.

In summary, DM plants are water treatment systems that remove all dissolved minerals and salts from water. They use a combination of ion exchange resins and a reverse osmosis system to achieve this. DM plants are typically used in industries requiring ultra-pure water, and they can be made of materials like MS, SS, or FRP.