Water purification is the process of purifying water by removing contaminants or microbial residues present in the water and make it acceptable for use. There are different types of purification techniques such as:
Boiling
Boiling water at 100 degrees Celsius is the traditional method of killing microbes causing intestinal diseases. But it cannot remove chemical toxins or impurities. Heating at 100 degrees Celsius for 10 minutes purifies water and makes it acceptable for use.
Distillation
Distillation technique works on the principle of condensation. In this technique, water is boiled at 100 degrees Celsius. Then water vapor raises to the condenser where cool water is passed to reduce the temperature, and vapor is condensed, collected and stored. The advantage of distillation is it removes broad range of contaminants. Disadvantage of this is that some contaminants carry into the condensate and it consumes more energy.
Reverse osmosis
Reverse osmosis uses filters to remove particles present in the water. It is an economical method and removes upto 99% of contaminants. The pore size of the reverse osmosis filter is more than ultra filters. It removes all the particles with greater than 300 daltons molecular weight. In this hydraulic pressure is applied to the concentrated solution to counteract the osmotic pressure. Thereby pure water is separated from the concentrated solution and collected at the bottom stream of the membrane.
Activated carbon absorption
It is a home based method of purification of water. In this method activated carbon is used to remove chlorine and all the contaminated particles present in the water. It will also remove many chemicals and gases. It will not affect total dissolved substances. It is prepared from a variety of carbon materials and processed under high temperatures. The main disadvantage of this method is it generates small carbon fines in water.
Desalination
It is the process of purification of saline water to form pure drinking water. This process is used in both distillation and reverse osmosis technique. It is expensive compared to other methods and it has limited use.
Gas hydrate centrifuge method
This technique is used to remove the contaminants from water by mixing carbon dioxide or low molecular weight gases to it. This creates hydrated crystals. These crystals are separated by centrifuge or sedimentation. Then purified water can be released by heating these crystals.
Ultra violet radiation
Ultra violet radiation treatment is used to kill microbes present in drinking water. Mercury low pressure lamps with ultra violet 254nm is passed through the water to purify it. This ultra violet radiation is absorbed by the DNA and proteins in the microbes present in the water and inactivates the microorganisms.
Direct contact membrane distillation
This method is used to purify saline water and converts into pure water. In this technique, water is heated and passed on to the surface of the hydrophobic polymeric membrane. Then evaporated water is passed from hot side to the cold side through pores on the membrane.