Purified water

Lore & Background

Purified water is usually produced by the purification of drinking water or ground water. The impurities that may need to be removed include inorganic ions, organic compounds, bacteria, endotoxins and nucleases, particulates, and gases. Distilled water, produced by boiling water and condensing the vapor, was the most common form of purified water, but water is now more frequently purified by other processes including capacitive deionization, reverse osmosis, carbon filtering, microfiltration, ultrafiltration, ultraviolet oxidation, or electrodeionization. Combinations of these processes produce ultrapure water with trace contaminants measured in parts per billion or parts per trillion.

Reader's Guide

Purified water is significant because it enables critical applications in medicine, science, and industry where water purity is essential. The source article notes that distilled water, like all purified water, must be stored in a sterilized container to guarantee the absence of bacteria. Deionized water, which removes almost all mineral ions, is generally similar to distilled water but quicker to produce and does not build up scale, though it does not significantly remove uncharged organic molecules, viruses, or bacteria. Double-distilled water was historically the de facto standard for highly purified laboratory water for biochemistry and trace analysis until combination purification methods became widespread. The article also notes that in colloquial English, purified water can refer to water treated to neutralize, but not necessarily remove, contaminants considered harmful to humans or animals. The various methods—distillation, deionization (co-current, counter-current, mixed bed), softening, demineralization, and other processes like reverse osmosis—offer different trade-offs in purity, cost, and application, with mixed bed deionization producing the purest water from a single pass when properly pretreated.

Did You Know?

• Distilled water, like all purified water, must be stored in a sterilized container to guarantee the absence of bacteria.
• Deionization does not significantly remove uncharged organic molecules, viruses, or bacteria, except by incidental trapping in the resin.
• Mixed bed deionization uses a 40/60 mixture of cation and anion resin combined in a single ion-exchange column.
• Purified water is used in the commercial beverage industry as the primary ingredient of any given trademarked bottling formula to maintain product consistency.