In the water treatment area, ion exchangers are generally used for softening, partial desalination and complete demineralisation. The deionate produced during the process is required mostly as boiler feed water for the operation of steam generation systems in industrial plants. The raw water is pre-treated (e.g. flocculation and filtration) in accordance with the water source. Reverse osmosis has proved especially effective where demineralised water is needed.
WABAG has employed the ion exchange process for industrial water treatment for a variety of industrial operations. In particular, comprehensive experience has been gathered from a large number of plants installed for demineralisation and condensate polishing as part of the production of boiler feed water.
During the process, the exchangeable ions linked to the ion exchange matrix are substituted for the ions to be removed from the water. In general, this process is reversible so that the whole process cycle consists of a service and a regeneration step. The adsorber material is employed in sealed filters as a fixed bed, in either an up- or down-flow. Anionic and cationic exchangers can be used individually, in multi-filter or mixed bed applications. In the service cycle, the water flows through the mixed bed filter until the effluent concentration of the unwanted ions exceeds a certain level. The exhausted adsorber bed is regenerated with a solution containing an excess of exchangeable ions (in the form of brine, acids or a caustic solution). The adsorbed unwanted ions from the water are then removed in the form of a concentrate flow.
As opposed to other systems, ion exchange is a batch process. Therefore, when production is to be continuous, the plant requires at least two adsorbers.