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Jul   2018

Water Purification Process & Various Methods Used for Water Purification:

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Water purification process & various methods used for water purification:

Water is a fundamental need of all the organisms it means that without water there is no life on the earth. One-third of the earth surface is surrounded by water but most of the water is in the form of sea water or ice which can't be used for the drinking purposes. Out of the total water on the earth, only 2-3% of water is in the form of freshwater.
These day human activity leads to the water pollution. Water pollution is used to define as the change in the physical, chemical, and biological properties of the water and the pollutant which is responsible for the water pollution is called the water pollutant. 
Water purification is a process which is used to remove the impurities present in the water. Water contains several impurities such as physical, chemical, and biological contaminants. Hence the water purification process removes undesirable contaminants, biological impurities, suspended solids, and gases from the water.
The main aim of the water purification process is to bring out water which is fits for the specific purposes such as drinking, medical, pharmaceutical, chemical, and industrial purposes.  Purification process reduces the concentration of the suspended particles, bacteria, algae, viruses, & fungi along with the range of the dissolved and particulate matter.
The standard of drinking water quality is created by governments or by international standards. According to the world health organization (who) report 2007, approximately 1 billion people is not able to use pure and healthy water for the drinking purposes.
Every year more than 4 billion case registers for diarrhea out of that approximately 90% of cases are due to the drinking of impure water. Diarrheal diseases cause approximately 1.8 million die every year. Who says that this ratio can be decreased up to 95% simply by access to pure and healthy water for the drinking purposes and modification in the environment. 
Reducing death which occurs due to the drinking of impure and contaminated water is the main aim of our country (India). Water purification can also be done at home by using chlorination, filters, solar disinfection, and storing in the safe container. 

Methods of water purification: 

Water purification process or access to pure and healthy water for drinking purposes can protect millions of lives every year. This can be achieved by the following methods which are given below-

  • Coagulation & flocculation:

This is the first step of the water purification in which some chemicals are added into the water for the removal of the suspended particle from the water. These added particles can be organic such as bacteria, virus, fungi, algae and any other natural organic compound and inorganic in nature such as clay and silt.
Addition of inorganic coagulants such as aluminum sulfate or iron salt such as iron chloride induces several chemical and physical interaction among the particles. The negative charge on the particles gets neutralized by the inorganic coagulants and starts forming a metal hydroxide of aluminum ions and iron.
These metal hydroxide i.e. Aluminum and iron hydroxide precipitate combine together and form a large compound under a natural process called Brownian motion or under induced mixing called as flocculation. These metal hydroxides start absorbing the suspended particle in the water and induce removal of those suspended particle by a subsequent process of sedimentation & filtration.
Organic coagulants are a man-made organic polymer. This polymer contains high molecular size and when it added into the water it starts absorbing the suspended particle present in the water and forms flock.  

  • Sedimentation:

Sedimentation is a physical process which removes suspended particles from the water using gravity. The particle which settles out from the water is called as sediment or sludge. The thick layer of sediment is known as consolidation.
Water containing flocculation basin enters into the sedimentation basin, sedimentation basin is a large tank which has low water velocities which allow the suspended particle to settle at the bottom. The flocculation basin and sedimentation basin are closed to each other that is why this process does not allow the floc to break up.
Before the coagulation process in water treatment process, sedimentation could be used to decrease the suspended particle present in the water. But after the coagulation process sedimentation is used to reduce the solid particle from the water so that the filtration process can function effectively.

  • Filtration:

Any mechanical, physical or biological operation which is used to separate solids from the fluids (i.e. Liquid or gas) by adding a medium which only allows the fluids to pass through it but doesn't allow the solids to pass. The fluids which pass through it is called as filtrate. There are various methods of filtration such as hot filter, cold filter, and vacuum filter and all these filters aim to separate the substance.

  • Disinfection:

The process of cleaning something to destroy microbes is regarded as disinfection. It could be done by removing harmful micro-organism or by adding disinfectant chemicals. Disinfection can be achieved by chlorine, chlorine dioxide, chloramine, ozone, and ultra-violate (UV) rays. Chlorine and its compounds such as chlorine dioxide and chloramine is a strong oxidant which efficiently kills the micro-organism whereas ozone is unstable molecules which produce natation oxygen which acts as a powerful oxidizing agent. Ultra-violate rays are very effective at reducing contamination.

  • Distillation:

The process of separation of any substance from a liquid mixture through selective boiling and condensation. It could be done to achieve the complete or partial separation which results in the higher concentration of the selective compound.

Additional methods for water purification:

  • Granulated activated carbon:

It is a form of activated carbon which has more surface area, more surface area allow it to absorb many toxic compounds. 

  • Reverse osmosis:

In this technology, water is allowed to pass through a semi-permeable membrane under a mechanical pressure. Researches say that reverse osmosis (RO) is the widely used technology for the water purification. The application of RO technology is RO water purifier.

  • Gas hydrated crystals centrifuged methods:

This method uses low molecular weight gas or carbon dioxide which is mixed with the contaminated water at low temperature and high pressure.

  • In-situ chemical oxidation:

It is an advanced form of oxidation which is achieved by inducing the effective oxidizer agent into the contamination medium to destroy the impurities.

  • Bioremediation:

This technology use micro-organism to remove the waste products such as alkenes & perchlorates from the contaminated water.

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