Purified water
Purified water has many uses, largely in the production of medications, in science and engineering laboratories and industries, and is produced in a range of purities.
It is also used in the commercial beverage industry as the primary ingredient of any given trademarked bottling formula, in order to maintain product consistency.
[1] Distillation involves boiling the water and then condensing the vapor into a clean container, leaving solid contaminants behind.
Deionization is a chemical process that uses specially manufactured ion-exchange resins, which exchange hydrogen and hydroxide ions for dissolved minerals, and then recombine to form water.
However, deionization does not significantly remove uncharged organic molecules, viruses, or bacteria, except by incidental trapping in the resin.
Co-current deionization refers to the original downflow process where both input water and regeneration chemicals enter at the top of an ion-exchange column and exit at the bottom.
Mixed bed deionization is a 40/60 mixture of cation and anion resin combined in a single ion-exchange column.
With proper pretreatment, product water purified from a single pass through a mixed bed ion exchange column is the purest that can be made.
A control system operates pumps and valves for the regenerants of spent anions and cations resins within the ion exchange column.
Softening consists in preventing the possible precipitation of poorly soluble minerals from natural water due to changes occurring in the physico-chemical conditions (such as pCO2, pH, and Eh).
It is applied when poorly soluble ions present in water might precipitate as insoluble salts (e.g., CaCO3, CaSO4...), or interact with a chemical process.
Processes rendering water potable but not necessarily closer to being pure H2O / hydroxide + hydronium ions include the use of dilute sodium hypochlorite, ozone, mixed-oxidants (electro-catalyzed H2O + NaCl), and iodine; See discussion regarding potable water treatments under "Health effects" below.
Purified water is suitable for many applications, including autoclaves, hand-pieces, laboratory testing, laser cutting, and automotive use.
[6] Purified water is also used in the commercial beverage industry as the primary ingredient of any given trademarked bottling formula, in order to maintain critical consistency of taste, clarity, and color.
In the process prior to filling and sealing, individual bottles are always rinsed with deionised water to remove any particles that could cause a change in taste.
The ASTM, NCCLS, and ISO 3696 or the International Organization for Standardization classify purified water into Grade 1–3 or Types I–IV depending on the level of purity.
For example, water that is being used for molecular-biology experiments needs to be DNase or RNase-free, which requires special additional treatment or functional testing.
It is worth noting that, although electrical conductivity only indicates the presence of ions, the majority of common contaminants found naturally in water ionize to some degree.
For comparison,[11] seawater has a conductivity of perhaps 5 S/m (53 mS/cm is quoted), while normal un-purified tap water may have conductivity of 5 × 10−3 S/m (50 μS/cm) (to within an order of magnitude), which is still about 2 or 3 orders of magnitude higher than the output from a well-functioning demineralizing or distillation mechanism, so low levels of contamination or declining performance are easily detected.
The presence of foreign ions commonly found in tap water will drastically shorten the lifespan of a lead–acid battery.
Since it does not contain impurities such as copper and chlorine, it helps to keep fish free from diseases and avoids the build-up of algae on aquarium plants due to its lack of phosphate and silicate.
The lack of impurity in the water means that the system stays clean and prevents a buildup of bacteria and algae.
[citation needed] When used as a rinse after washing cars, windows, and similar applications, purified water dries without leaving spots caused by dissolved solutes.
The use of purified water from water-fed poles also prevents the need for using ladders and therefore ensure compliance with Work at Height Legislation in the UK.
