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Water Purification

Last Updated : 19 Oct, 2021
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Water is carried through canals or lengthy pipelines in a water purification system, which contains various pollutants and suspended particles from rivers and lakes. River water is commonly used to supply cities with drinking and dining water. This water is unsafe for drinking or dining because it contains a high concentration of suspended pollutants and potentially hazardous microorganisms including bacteria and germs. The following stages make up the water purification system process:

What is Water Purification?

Water purification is the process of removing unwanted chemical compounds, organic and inorganic elements, and biological pollutants from water. 

Distillation (the conversion of a liquid into vapour in order to condense it back into liquid form) and deionization are also part of this process (ion removal through the extraction of dissolved salts). One of the primary goals of water filtration is to produce safe drinking water. Water purification also satisfies the requirements for clean and drinkable water in medical, pharmaceutical, chemical, and industrial applications. Contaminants such as suspended particles, parasites, bacteria, algae, viruses, and fungus are reduced in concentration during the purifying process. Water purification occurs in a variety of sizes, ranging from big (e.g., for a whole city) to tiny (e.g., for individual households).

The majority of communities rely on natural bodies of water for water purification and day-to-day use. These resources are typically categorised as groundwater or surface water and include subterranean aquifers, creeks, streams, rivers, and lakes. Oceans and salty seas have also been employed as alternate water sources for drinking and domestic usage due to recent technology developments.

Water Purification System

The supply water is purified as discussed in the following stages in four respective to reach out to our homes:

Stage 1: The water is gathered from rivers and lakes using canals or long pipes.

Stage 2: It is placed in the sedimentation tank, which allows all solid particles to settle. When suspended materials and matter sink to the bottom of a container, the second stage begins. The longer the water stays undisturbed, the more solids will fall to the container floor due to gravity. The sedimentation process must occur continually and in vast sedimentation basins for a community water supply. Before the filtration and disinfection processes, this simple, low-cost application is required as a pre-treatment step.

Sedimentation tank: The water from the river or lake is first filtered by the sedimentation tank. The water is allowed to sit for a while here. Many suspended solids settle to the bottom of the tank during this time.

Stage 3: It’s transferred to a loading tank, where all of the dispersed particles can settle.

Loading tank: Water is supplied to the loading tank from the sedimentation tank. Alum (phitkari) is added to the water in the loading tank. Clay particles in water are negatively charged colloidal particles. In the sedimentation tank, they do not settle. When alum is introduced, however, the positively charged aluminium ions in alum neutralize the negatively charged particles. As a result, suspended clay particles become heavy, loaded with aluminium ions, and settle to the bottom of the tank.

Stage 4: The water is then pumped into a three-layer filtration tank. The colloidal particles have dropped to the bottom of the water supply at this point, and the clean water is ready to be treated further. Filtration is required due to the presence of minute, dissolved particles such as dust, parasites, chemicals, viruses, and bacteria in clear water. Water travels through physical particles that vary in size and content during filtering. Sand, gravel, and charcoal are some of the most commonly used materials. 

Filtration tank: The water is routed through a filtration tank after insoluble solids and other suspended pollutants have been removed. There are three layers in the filtering tank. Coarse gravel is placed at the bottom of the tank. Fine gravel is placed over it, and a thick layer of fine sand is laid on top of the gravel. These sand and gravel layers operate as filters. At the bottom, filthy water is added. All of the contaminants in the water are retained as the water climbs above, and only pure water leaves the tank at the top.

Stage 5: The filtered water is then sent into a chlorination tank for disinfection, where it is combined with chlorine tablets to eliminate microorganisms in the water. The final step in the dining water treatment process is to add a disinfectant to the water supply, such as chlorine. Since the late 1800s, chlorine has been used. Mono-chloramine is the type of chlorine used in water treatment. This is not the same as the type that might contaminate interior air quality around swimming pools. The disinfection impact is to oxidise and remove organic matter, which stops parasites, viruses, and bacteria from spreading in the drinking water. 

Chlorination tank: The water from the filtration tank is pumped into the chlorination tank, where it is bleached or treated with additional germicides to eliminate microorganisms. As a result, the water purification system has reached its conclusion, and pure water is now available for drinking and other human use.

 Supply of Dining\Drinking Water in a city

The water obtained after the above procedures is free of all pollutants and microorganisms, and it is distributed to our homes for drinking.

Sample Questions

Question 1: What is the primary distinction between a solution and a regular mixture?


In general, mixtures are heterogeneous, with a border separation between distinct substituents. Solutions are homogeneous mixtures in which there is no obvious separation between the various ingredients.

Question 2: What is the difference between the two sorts of pure substances? Give an example of each of the types.


There are two sorts of pure substances:

  1. A pure substance formed up of atoms of the same type. Sulphur is a good example.
  2. A pure substance formed up of molecules of the same type. Water is good example.

Question 3: Give two physical qualities that distinguish metals from non-metals.


Non-metals are neither malleable or ductile, whereas metals are.

Question 4: How would you know if a colourless liquid you were given was pure water?


Ans. We can test this by evaporating the colourless liquid provided. The colourless liquid is pure water if nothing is left behind.

Question 5: Give two reasons why you think water is a compound rather than a mixture.


Below are the reasons for water is a compound.

  • Physical methods cannot split water into its constituents, hydrogen and oxygen.
  • When water is created by burning hydrogen in oxygen, heat and light are released.

Question 6:  Give one trait that a sugar solution in water has in common with a sugar and sand mixture, and one property that it doesn’t.


  • Similarity: Physical procedures can be used to separate the mixture into its constituents in both circumstances is same.
  • Difference: In a mixture of sugar and water, no separation is visible, however in a mixture of sand and sand, separation is visible.

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