How is Distilled Water different from Deionised Water?

The principal differences between Distilled water and Deionised water are in their production methods. Deionisation is considered a much inferior practice to distilling water and in some cases the two processes are used in tandem. The deionisation process is driven by an exchange of percolates that are artificially introduced into the water. These percolates take the form of a bead like sphere consisting of a high density resin material known as ion-exchange resins.


During the process, the ion-exchange resins undergo a process during which the purer ions that have been fixed to the beads are released while the impure ions that are lighter are driven upwards an on to the beads that are later removed from the tank. These hard working deionisation beads will exchange hydrogen and/or hydroxyl ions for cations or for anions which are regarded as being impure elements. The deionisation process is generally carried out as a component of total water purification albeit an important one.


It is rarely used as single component in water purification and is generally part of an overall process where reverse osmosis, high level filtration system when used in combination with other methods discussed in this primer such as RO filtration and even when treating water that has undergone a carbon absorption process to remove exceptionally fine dust such as coal dust.


Deonisation is known to be exceptionally efficient, although the process can struggle to remove most forms of organic bacteria or micro-organisms. In the process it is not unusual for micro-organisms to attach themselves to the resins in the tank, actually exacerbating the growth of bacteria.


Conversely the process of distilling water involves some form of evaporation process where water from a feed tank is brought to boiling point and the steam that gathers is harnessed in a separate tank allowed to cool back to liquid form. This is a relatively simple process, and does not involve the introduction of any materials into the water as is the case with deonisation. In order to produce ultrapure water for high level industrial processes, or in science, medicine or even in the field of high tech, it is fairly common practice for companies to use a double stage process where first water is distilled and then deionised. The reason for this that the pureness levels of the water after distillation will be high enough to enable the resin beads introduced during introduce distilled water greatly prolongs the life of the resin beds as well as increasing their efficiency.


There are many other forms of mechanised water purification with the others being reverse osmosis, carbon filtration, microfiltration, ultra filtration, ultraviolet oxidation, or electro dialysis and sometimes even a combination of one or more of the processes. To achieve acceptable high levels of purification any of these methods will prove to be equally efficient, but none of them will be as cost-effective as condensing water. While there are no specific statistics available it is generally estimated that condensed water comprises a very large overall percentage of all water has been treated to increase its purity levels.