Most of the substances dissolved in water are inorganic salts existing in the ionic state. Positively charged ions are called “cations” whereas negatively charged ions are called “anions”
“Demineralizers” or “deionizers” are devices that use resins to carry out ionic exchanges and remove practically all salinity from the water. The exchange may either take place by successive stages on the cationic or anionic resins, or it may take place by a single phase of well-mixed resins or so–called “mixed beds”
Deionized water has a wide range of applications as process water, it is indispensable in the pharmaceutical, chemicals, and cosmetic industries.
Extremely pure deionized water is also fundamental to the electronics industry in manufacturing microprocessors, to the industrial washing of such products as glass and plastic molds, and to the dilution of concentrated products such as is required in preparing alcoholic beverages.
Finally, deionized water is an absolute necessity in analysis labs and high–pressure boilers.
Disinfection treatment methods include chlorination, chlorine dioxide, Ozone and Ultraviolet disinfection used to control most pathogenic bacteria, viruses etc.
The disinfection system needs careful selection to ensure the most effective process is integrated into the water treatment system.
Chlorine is the most cost-effective and widely used disinfectant. Its readily available around the world and maintains permanent water disinfection.
Chlorine dioxide (Cl02) is also widely used as a disinfectant for potable water. It is generated on-site in dedicated reactors by mixing hydrochloric Acid (HCl) and Sodium Chlorite (NaCl02) in appropriate proportions. Chlorine dioxide is effective over z wide range of pH (4-10) compared to other chlorine-based compounds, which are not effective for pH values above 7.5.
Ultraviolet (UV) rays are generated by special lamps emitting the appropriate wavelength of light for killing / inactivating microorganisms. UV rays at 254nm (nanometer) destroy 99.9% of pathogens and unlike chlorine, no residual is left in the water.
UV technology is often selected when an efficient system for eliminating pathogens without using any chemicals is preferred. Sometimes, UV is used in conjunction with other oxidants/disinfectants (Ozone, Oxygen etc) to increase their effectiveness.
Some of the main advantages of using UV disinfectant are;
- Excellent efficiency for water with low turbidity
- No alteration in the composition of the water
- No by-products and change in odor or taste
Ozone (0ӡ) is a strong oxidizing gas that reacts rapidly with most organic (and many inorganic) molecules. It’s short half–life in water, approximately 10 – 30 minutes in practical treatment applications, requires ozone to be generated on–site for use as a disinfectant.
Ozone does not produce a disinfecting residual, so a second disinfectant must usually be added to the treated water to furnish the necessary protection in the distribution system.