explain dm plant operation?

Answer 1

Basically a DM (demineralizing) plant works to take the mineral content of the liquid down to some level that is acceptable for consumption. This MAY mean all the way down to where there are no minerals left, by the way!

Chemical additives (like acids, bases, or even other metals) are blended with the water as it progresses from stage to stage, with the resulting chemical reactions creating non-soluble byproducts and "purer" water.

The process is repeated in as many stages as necessary to reduce the water to its required purity.

This is a very simplified version, but it may be enough to suit your needs.