Although counter-currently regenerated ion exchange demineralizer (DM) plants have been widely available since the 1960’s, the past decade has seen the introduction of a new generation of demineralizer designs in North America and Europe. Promoted by several of the major resin manufacturers, these include UPCORE from Dow Chemical, PUROPACK from Purolite and AMBERPACK from Rohm & Haas. Although these systems have minor differences in design, they generally tend to share a number of common features. These include:
- counter-flow (i.e. counter-current) regeneration
- packed resin beds (i.e. no freeboard)
- fine/uniform particle resins
- short resin beds
- shorter operating cycles
The major advantages claimed for this technology are lower regenerant chemical consumption, higher demineralized water purity and smaller equipment. These systems have sparked renewed interest in ion exchange demineralization. The improved performance has reversed or slowed the industry-wide trend towards the use of reverse osmosis in lieu of ion exchange.
While these designs have advanced the stateof- the-art somewhat, they should be considered a evolution of the technology, with only incremental advantages. Advancement has been limited by traditional fixed-bed ion exchange design principles, which have been ingrained into the thinking of most water treatment professionals.