Demineralization of water – DM water

Demineralization of water is a process that removes minerals from water and produced demineralized water. Shortly it is called dm water or demi water. It is water softening process. The most common dm water processes are distillation, deionization, membrane filtration (reverse osmosis or nanofiltration), electrodialysis. This water is not free from some uncharged molecules like viruses or bacteria and organic contaminants. The transportation of demi water is very significant as it is highly aggressive for metals and other plumbing materials. Comparably plastic materials are safe for transportation and storage.

pH value of dm water

The pH value of demineralized water should be 7.0 but it is slightly acidic. Reason, the carbon dioxide dissolves in it from the air; until reaches dynamic equilibrium with the atmosphere. The dissolved carbon dioxide reacts with the water and creates carbonic acid.

H₂O + CO₂ → H₂CO₃ (carbonic acid)

Only fresh dm water has neutral pH value 7.0, but when we leave them for a few hours; they will capture carbon dioxide from the atmosphere and become slightly acidic. In this way the pH value can be 5.5.

DM water conductivity

As the demineralization of water is a minerals removing process and the electric current is related to minerals, therefore the demineralized water has a very low electric conductivity. It has no fixed value. It has a higher conductivity value than deionized water. The dm water conductivity unit is expressed as millisiemens/meter (mS/m) or microsiemens/centimeter (µS/cm). Generally it is less than 2 mS/m, even lower than 0.1 mS/m.

DM water TDS value

The TDS value of water depends on the amount of minerals that are dissolved in water. When the minerals like calcium bicarbonate, magnesium sulfate, and sodium chloride increases than the TDS value increases. Consequently the process of demineralization of water decreases the TDS. It should be always less than 10 mg/l, even as low as 1 mg/l.

Demineralized water uses

The water that contains the minerals like calcium bicarbonate, magnesium sulfate, and sodium chloride can hamper different stages on chemical or physical process of chemical industries. They require low salt or low conductivity water. DM water is free of minerals salt, so this water is suitable for those industries. For example demi water is used in boiler feed water, textiles, pharmaceuticals, breweries, swimming pools, potable water, hospitals, automobile, lead-acid batteries, fertilizers, cooling systems.

Drinking demineralized water

A certain amount of minerals are important parts of drinking water. Internationally maximum acceptable levels of inorganic and organic substances have been established to assure the safety of drinking water. Different minerals increase the taste of water. As the dm water almost completely free from minerals; it has poor taste and thirst-quenching characteristics. Moreover trace amount of certain minerals provide the health benefits, so the consumption of this water is not good for health. In addition the demi water tends to take out minerals from food and electrolytes from the body, so it is also not suitable cooking purposes.

Difference between demineralized and distilled water

Both the demineralized and distilled water are purified water. Although distillation process is one kind of demineralization of water system but they have a clear difference. The major difference is that the distilled water is free of both the organic and inorganic contaminants; even it is also free of uncharged molecules such as viruses or bacteria whereas demineralized water is only free of mineral ions, but not free of uncharged molecules like viruses or bacteria and organic substances. Distilled water is much purer than dm water but it is more costly.