Purification Of Water Through : Disinfection, Distillation, Electro Dialysis and pH-adjustment
Q: How can we purify water through disinfection ?
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose. Most water is purified for human consumption (drinking water) but water purification may also be designed for a variety of other purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications. In general the methods used include physical processes such as filtration and sedimentation, biological processes such as slow sand filters or activated sludge, chemical processes such as flocculation and chlorination and the use of electromagnetic radiation such as ultraviolet light.
Disinfection is one of the most important steps in the purification of water from cities and communities. It serves the purpose of killing the present undesired microrganisms in the water; therefore disinfectants are often referred to as biocides. There are a variety of techniques available to disinfect fluids and surfaces, such as: ozone disinfection, chlorine disinfection and UV disinfection.
Chlorine has a downside: it can react to chloramines and chlorinated hydrocarbons, which are dangerous carcinogens. To prevent this problem chlorine dioxide can be applied. Chlorine dioxide is an effective biocide at concentrations as low as
0.1 ppm and over a wide pH range. ClO2 penetrates the bacteria cell wall and reacts with vital amino acids in the cytoplasm of the cell to kill the organism. The by-product of this reaction is chlorite. Toxicological studies have shown that the chlorine dioxide disinfection by-product, chlorite, poses no significant adverse risk to human health.
Ozone has been used for disinfection of drinking water in the municipal water industry in Europe for over a hundred years and is used by a large number of water companies, where ozone generator capacities up to the range of a hundred kilograms per hour are common. When ozone faces odours, bacteria or viruses, the extra atom of oxygen destroys them completely by oxidation. During this process the extra atom of oxygen is destroyed and there are no odours, bacteria or extra atoms left. Ozone is not only an effective disinfectant, it is also particularly safe to use.
UV-radiation is also used for disinfection nowadays. When exposed to sunlight, germs are killed and bacteria and fungi are prevented from spreading. This natural disinfection process can be utilised most effectively by applying UV radiation in a controlled way.
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