How can you produce demineralized water / ultrapure water?

Ultrapure water is highly pure water that contains almost no foreign substances. Unlike natural water that occurs in nature, ultrapure water does not contain minerals such as calcium and magnesium. Ultrapure water is produced for special industrial applications, such as steam generators.

According to the European Pharmacopoeia, the following requirements are placed on ultrapure water, among others:

• Conductivity less than 1.1 µS/cm at 20° C
• Total organic carbon (TOC) less than 0.5 mg/l
• Nitrate less than 0.2 mg/l

Quality of ultrapure water

The quality of different waters (e.g. distilled water, demineralized water and ultrapure water) can be measured in particular by their electrical conductivity. In practice, conductivity is often given in µS/cm. Because the water molecules react with themselves, even ultrapure water has a very low conductivity. Distilled water usually has a conductivity of 0.5 to 5 µS/cm at 25° C.
For steam generation in power plants with high-pressure steam generators, the water may have a maximum conductivity of 0.2 µS/cm.

Production of ultrapure water

Ultrapure water is usually produced by a reverse osmosis system with a downstream mixed bed resin. For optimal yield, the raw water is treated by a softening system before the reverse osmosis system. In this way, the yield of reverse osmosis increases significantly.