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Ion Exchange or Water "Softeners"
Nearly all recognized household water softening equipment now on the market makes use of the ion exchange principle. Softening is used primarily as a pretreatment method to reduce water hardness prior to a Reverse Osmosis process.
The Ion Exchange process utilizes a bed of permanent bead-like or granular softening "ion exchange" material through which the water flows. As water flows through the bed, magnesium and calcium (commonly found in hard water) cations in the water are drawn to the anions present in the ion exchanger. Salt is used in this process in order to replace the hard water ions. Having a greater affinity for the calcium and magnesium ions than for sodium ions, the calcium and magnesium ions are absorbed, and a chemically equivalent number of sodium ions are released into the water. As the water travels through the bed of ion exchange material, hardness minerals are removed, leaving the water "soft," and more suitable for household use.
Most manufacturers make two basic types of water softeners. These can be classified as fully automatic or demand initiated regeneration models. Typically equipped with a timing device, a fully automatic softener initiates every step in the regeneration process. The regenerating of the unit is usually done at night when water usage is at a minimum. With a demand initiated regeneration unit all operations, including bypass of hard or soft water and return to service are initiated and performed automatically in response to the demand for treated water.
Problems with Ion Exchange and Water Softeners
While the Ion Exchange process is effective at removing hard water components such as magnesium and calcium, they do not effectively remove most VOCs or microorganisms. In addition, microorganisms can attach to the resins, providing a culture media for rapid bacterial growth and eventual output contamination.
After a vast number of hardness ions in the water have become affixed to the softening material through the attraction of positive and negative charges, and most of the sodium ions have been released, the unit can no longer soften the water. It has become temporarily exhausted. This is the reason that frequent replenishment of salt (the ionic exchange replacement), is necessary in these filtration systems. If salt is not replaced on a regular basis (depending on the demand of the incoming water), water contaminants will eventually flow untouched through the unit. Because of the necessity to replenish salt in a Water Softener (Ion Exchange Unit) often, this filtration method requires high operating costs over time. Salt must be purchased and kept on hand, while manual labor to add the salt is required. |
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