Ion exchange

What Are The Best Technical Practices For Deionization Systems?

By Claude Gauthier, P.Eng.


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This technical article outlines best technical practices for power plant ion exchange (IX) demineralization equipment. Often when problems suddenly occur with IX equipment, plant operators will blame the IX resin. The first thing they will do is take a resin sample and submit to a lab for evaluation. It is the writer’s experience is that 9 of 10 cases it is not the resin at fault. It is either regeneration or mechanical issue that are the root cause of the problems experienced with effluent quality and/or reduced throughput capacity runs.

Case studies are presented in the article for troubleshooting and performance optimization of demineralizer equipment.

Impact of Pretreatment

Good IX performance is dependent on the quality of the influent supply water. If you use IX equipment as a filter, you cannot expect good deionization performance. It is best to provide low total suspended solids (TSS) as IX can filter down to 20 micron. The typical specification for standard deionization influent turbidity should be less than < 1 Nephelometric Turbidity Units. The water supply should be chlorinated to minimize the potential for biological growth. As the influent water temperatures increase above 55°F, the potential for biological activity growth increases.

Temperatures in the 84 to 104°F are the ideal range for rapid bio growth potential. The presence of oxidant residuals in the water will degrade the cation resin, which in turn sloughs off organic degradation products that will foul the downstream anion resin. The corrective practice is dechlorination using either granular activated carbon (GAC) filters, or by the chemical feed of sodium bisulfite.

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