To start with I needed a better understanding of how this method of filtration worked.
The ion exchange process percolates water through ion exchange resins (which are typically a resin material in a spherical shape to increase overall surface area). As the water is run over the water filter made of these resin spheres, ions in the water are exchanged for other ions which are fixed or embedded on the resin beads. The two most common ion exchange systems in use today are used for softening and deionization.
Softening is used mainly as a pretreatment method for water hardness prior to reverse osmosis (which will be investigated for my next post). The softener beads have sodium ions embedded, and these are exchanged for calcium or magnesium ions in the water.
Deionization beads come in two varieties. These exchange hydrogen ions for cation ions ( ie, positively charged impurities ) and the anion beads remove negatively charge impurities.
De ionizing the water needs to be in two stages. Usually these resins are packed in two separate filters, to make the replacement of used up filters easier. They can also be mixed together to form one filter, but this is a little more wasteful. The major advantage the resin filters have is they can be regenerated. This involves getting them to release all the contaminants for hydrogen or hydroxyl ions, but the crucial part of this is that this regeneration will not occur in your drinking water.
After having gone through all this, I noticed this method of filtration occurs more frequently than I had realized, especially in hard water areas of the country to help reduce the amount of lime scale. Later on I will be investigating methods available to the public to remove these.
As with all filtration methods, there are pros and cons for this method.
This method is very efficient in removing inorganic ions from the water supply. It is also relatively cheap startup cost to incorporate this into a water system, and the ion exchange resins can be regenerated. This makes it a valuable part of a multi filter system.
The downside of relying on ion filtration is that this method only removes inorganic impurities. Any bacteria, or living material is not filtered, and bacteria can actually attach and grow cultures on the resin beads. The same is true for any other organic molecule or pyrogens. Another downside is this is an expensive running cost over time.
In summary, deionization can be an important component of a total water purification system when used in combination with other methods. DI systems effectively remove inorganic ions, but they do not effectively remove most organics or microorganisms. Microorganisms can attach to the resins, providing a culture media for bacterial growth and subsequent pyrogen generation.
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