Over the years we humans have developed a range of ways to purify water for our own use. Water purification systems are from RO To UV ray treatment and eve gone to the exted of Ionizing water for our benefits and consumption. Read on for more information
This process involves removing undesirable chemicals, biological contaminants, suspended solids and gases from contaminated water. Water is purified for several purposes. The most common purpose of purification is for drinking. Purifies water is also necessary for various commercial purposes like medical, pharmaceutical, chemical and industrial purposes. The standard of purity required will vary according to the application for which it is used. Various governments or international organizations set purity according to specified standards. These standards set the minimum and maximum concentration of contaminants allowed for the various uses of water.
Common purification methods includes
- Physical processes like filtration, sedimentation and distillation
- Biological processes like slow sand filters or biologically active carbons
- Chemical processes like flocculation and chlorination
- Use of Electromagnetic radiation like ultraviolet rays
Common household methods like boiling water and use of household activated carbon filters have been found to be insufficient for the complete removal of all impurities in water. Spring water, which was safely used in earlier years, has also to be tested for purity.
Distillation: This is one of the oldest methods of water purification. Here water is first boiled and then cooled. Some of the contaminants remain in the distilled water. It also does not remove some chemicals which have a boiling point of less than 100 degrees. This method of water purification is not energy efficient and since water becomes acidic (tasteless), it is used mostly for industrious purposes.
Ion exchange: In this method water percolates through bead-like spherical resin materials. These resins contain ions which are exchanged with ions in water. This method is used for softening water and also for deionization. Water softening is done by exchanging two sodium ions for one calcium or magnesium ions. This process is done before reverse osmosis. Deionization process exchanges the hydrogen ions for cations (net positive charge) or hydroxyl ions for anions (net negative charge). These hydrogen and hydroxyl ions thus exchanged unite to from pure water. This method of water purification is more effective when used with other methods.
Carbon absorption: This is one of the most common methods of water filtration. Carbon can remove many of the disagreeable tastes and odors including chlorine. It is not effective against some of the microorganisms and does not remove dissolved solids, hardness or heavy metals. Some certified carbon filters can remove lead, asbestos, cysts and chloroform. There are two types of carbon filters, granular activated carbon and solid block carbon. This method of water purification works better when used with other methods like reverse osmosis.
Micro porous basic filtration: This method uses three types of filters, each performing different functions, depth, screen and surface filters. Depth filters are matted fibers or compressed materials to form a matrix and retains particles by random adsorption. Screen filters work like a sieve and retains all particles bigger than its size. Surface filters made of multiple layers of media again retains particles bigger than its media but accumulates them at the surface.
Reverse osmosis: This is one of the most cost effective and efficient methods of water purification. It is highly effective in removing most of the dissolved solids, water turbidity, metal concentrates like lead asbestos etc. and dissolved organics like radium. The RO membranes are very tight and reject most of the bacteria, and other particles. The semi-permeable membrane rejects even dissolved salts and sugars through an ionic process. The greater the charge of the ions, the greater is its rejection. It follows the principle of osmosis. Here, hydraulic pressure is applied to counter osmotic pressure. The concentrated water passes through the membrane and the purified water is collected below the membrane. This process is commonly used in conjunction with some of the above mentioned purification processes. This process of water purification is very slow and cannot be used to purify very large quantities of water.
Ultraviolet radiation: Low pressure mercury lamps which generate 254 nm UV lights are used to effectively treat water of its germicidal components. These ultraviolet rays inactivate the DNA and proteins in the microbial cells resulting in the inactivation of the microorganisms.