Purification of water at domestic and school level can be achieved by the following methods: 1. Distillation 2. Boiling 3. Filtration 4. Chemical method of sterilization.
In the process of distillation water is heated and evaporation takes place, whereby water changes back to water when cooled; this process is called condensation. The condensed water is the purest form of water, free from microbes, and impurities.
But it loses its taste and odor. Through aeration or passing oxygen through it the water becomes consumable.
This method is quite expensive and time – consuming. But in place like laboratories, on sea-ships or places where pure water is not available, this method is found to be very useful.
For water purification and in sterilization, boiling is the best and simplest method to purify and disinfect. After straining the water twice through clean muslin cloth, it is boiled for ten minutes lo kill the microbes present in it and also remove the temporary hardness of water.
If the water is still unclean then small amount of aluminum sulphate or fitkari is added and left for a few hours. The impurities will collect at the bottom of the pan. This water should be boiled again before use.
Different varieties of filters are used to purify the water at domestic level. Filter rods (candies) are installed in the upper chamber. These rods are made of china porcelain and it is porous and hollow from the centre. When water is filled in the upper chamber it purifies and drips in the lower chamber. This water is free of any suspended matter but still has microbes in it
4. Chemical Methods for Water Sterilization
(a) Aluminum Sulphate (b) Chlorine
(c) Potassium Permagnate purification by Ultra-Violet Rays
In a school where a large number of students and teachers depend on the water supplied by the local civic bodies, extra measures to ensure good quality of water are needed especially when it is routed through drinking water coolers.
These water collars should be cleaned at regular periodicity and should be pilferage free. Besides, ultra-violet rays may be used for destroying micro- organism from the water without any chemical change. It has the following advantages: –
(a) Ultraviolet rays destroy all kinds of bacteria and virus, which produce diseases.
(b) Besides the boiling method, this method is safe and water can immediately be used. There is no chance of any contamination in storing it for 48 hours. Water stored in ordinary filters and pitchers provide a breeding place for the microbes.
(c) Water is purified in its natural form; there is no chemical change in it.
(d) The quality of water remains intact.
(e) It has an electronic method for water purification, which is more reliable.