KDF 55 and KDF 85 are two process media using copper-zinc granules to remove contaminants in water using an oxidation/reduction (redox) reaction. KDF 55 is used for the removal of chlorine and water-soluble heavy metals (lead, mercury, nickel chromium). It also controls scale, bacteria and algae.

In case of chlorine, the free chlorine is reduced to chloride ions.

Filter cartridges containing granular activated carbon (GAC) based on coconut shell are often used in combination with KDF 55/85 to extend the life of the filter cartridges. Also ion exchange systems use KDF to extend the life time of the resin bed.