This process requires a collector system about half way up the unit. For technical reasons, this is covered by an approx. 200 mm deep inactive resin layer (active resin). Air or water is used to create a pressure drop in this resin layer which holds the active resin bed in place during upstream regeneration and elution.
Rinsing with fully demineralised water (or decationised water in the case of cation resins) can be performed in the same direction as exhaustion (downflow) at high speed. Fully demineralised water is needed to rinse anion resins, but decationised water is sufficient for cation resins. It is important to make sure that the fine polishing layer in the resin bed is not exhausted or destroyed prior to operation in order to ensure that the counter-current process produces the high-quality water required of it.
- better water quality
- lower regenerant requirement
- lower water consumption
- high availability because of short regeneration cycle