PURIFICATION TECHNOLOGIES
Distillation
The equipment is relatively inexpensive, there are no expendables other than replacement
glassware and heating elements, and it produces water of generally good quality.
Distillation typically produces water of Type II or III quality, with a resistivity
of about 1.0 megohm.
Distillation has several drawbacks, however, and because of
these, is not as widely used as in the past. Distillation is not an on-demand process.
Because of this aspect, a quantity of water must be distilled and stored for later
use. If the storage container is not made of an inert material, ions or plasticizers
will leach out of the water container and recontaminate the water. Bacteria are
known to grow well in standing water. The bottles may be sterilized and the collected
water autoclaved. However, once the bottle is opened, it is exposed to bacteria
and contamination begins.
Distillation has other drawbacks, including being highly
wasteful of energy and water typically only 5% of the water used in the process
ends up as product water. Stills require regular cleaning due to build-up of mineral
deposits from the feedwater.