4. Ion exchange

Please refer to the Ion Exchange articles in the Process Engineering treatise.

Until recently, only cation exchange resins were authorized for drinking water treatment (circular dated May 3, 1963).

Circular no. 1 136 of July 21, 1985 authorizes the use of anion exchange resins, and defines the conditions and technical specifications they must meet (type of resins, application, regeneration).

This is immediately applicable to denitration treatment (figure 25 ). The authorized exchanges are those of the ${\text{NO}}_3^{-}$ ion between...