Demineralizer Effluent Quality

How to tell effluent quality in a two bed demineralizer.

In a normal operating two bed demineralizer, the effluent quality if primarily indicated by the amount of sodium leaking off of the cation unit. The cation bed is operated in the hydrogen form. The anion bed is operated in the freebase form if it is a weak base anion unit; the hydroxide form if it is a strong base anion unit.

After exiting the cation unit, the sodium ion remains as a salt when it subsequently exits a weak base anion unit. When passing through a strong base anion unit, however, it becomes NaOH which causes a higher effluent pH.

RESISTIVITY AND pH OF TWO BED EFFLUENTS