External feedwater treatment is accomplished by passing water through a ______?

• A. Zeolite Softener
• B. Activated Carbon Filter
• C. Ion Exchange Resin
• D. Sand Filtration

Answer: (A)

Removing hardness from the feedwater before it enters the boiler is essential to prevent scale on heat-transfer surfaces. A zeolite softener accomplishes this by passing water through a bed of zeolite that exchanges calcium and magnesium ions in the water for sodium ions on the zeolite. This ion-exchange process softens the water, dramatically reducing its tendency to form scale inside the boiler. Once the zeolite becomes exhausted, it’s regenerated with brine to restore capacity. Other options don’t target hardness: activated carbon mainly removes organics, sand filtration removes particulates, and while ion-exchange resin can soften water, the device described for external pretreatment is the zeolite softener.