Industrial water demineralization and distillation are two of the most common water treatment methods used today and each process offers varying benefits. Between the two water treatment processes, the most obvious difference is the method of purification. In demineralization, the water runs through a bed of ion exchange resin, which separates out ionic impurities, including dissolved carbon dioxide. In the case of water distillation, the water is boiled and then the vapor is cooled. When the vapor has condensed, demineralized water is produced. However, distilled water is saturated with dissolved carbon dioxide.
Water distillation is an older purification method. Evaporation is achieved through various means – the most common being the heating method. However, a large drawback is the high energy cost of converting water into steam.
Distillation, unlike demineralization, is effective at killing bacteria and viruses and is often the method of choice for pharmaceutical and medical applications. However, organic substances with a similar boiling point to water can pass through distillation and may have to be removed downstream. Similarly, dissolved carbon dioxide, which passes through distillation, may need to be removed using gas-permeable membrane or polishing demineralization. Water softening or demineralization is sometimes utilized upstream of distillation to prevent build-up of minerals in the boiling chamber.
Lower operating and capital costs and less concern about bacteria and viruses makes demineralization preferable to distillation for most industrial process water applications.