Steps Involved in the Purification of Drinking Water


To provide safe and quality drinking water, water utility companies have to meet the stringent requirements and regulations throughout the world. Not meeting these strict regulations can lead to severe reputational and financial consequences, not to mention spreading health hazards among populations.Companies follow a rigid drinking water treatment process to purify it using different chemicals, like Poly aluminiumchloride (PAC), to coagulate, filter, and disinfect it before it can be consumed.Here are the steps involved in the purification of drinking water:

Step 1: Aeration

Firstly, raw water is collected in an aeration tank. During the aeration process, CO2 and foul odors are removed from the water by adding compressed air in the tank through perforated pipes. This process also eliminates metals, like manganese and iron.

Step 2:  Settling or Storage

In the next step, the aerated water is stored in a settling tank for around 10 to 14 days. Around 90% of suspended solids and certain toxic chemicals in the water settle down in this storage within a day. This leaves behind clear water. (

Within seven days, pathogenic bacteria gets eliminated, and there is a 90% decrease in the bacterial count.

Step 3: Coagulation

The stored water is placed in a coagulation tank, and certain chemicals and agents, including Poly aluminiumchloride (PAC), are added and mixed in the water. The suspended solids remaining in the water absorb these agents and become heavier, and gradually settle down. Any negatively charged impurities left in the water settle down during this step.

Step 4: Filtration

The partially clarified water enters the filtration process in which it is passed through a filter. A sand gravity filter is used in this process that helps to remove about 99% of impurities and microorganisms.

This water filter is a rectangular tank that includes three layers of the filter bed. The filtered water is collected at the bottom of the filter in a collection tank.

During this process of filtration, the filter bed gets a slimy layer that is called a vital layer, which includes bacteria, diatoms, and algae. These microorganisms oxidize the organic matter still present in the water while also filtering the microbial cells.

In case there is still an unpleasant odor in the water, the activated carbon can be included in the filter bad to eliminate it.

Step 5: Disinfection

In the last step, this filtered water is purified with the help of disinfectants, like chlorination. These disinfectants help to kill pathogenic microorganisms and other impurities. Finally, the purified water is placed in an overhead tank for distribution.

These are the main steps involved in purifying drinking water, ensuring it is safe for public consumption. Water companies search actively for cost-effective and efficient solutions to remove containments present in the water and maintain high quality and standards of drinking water.


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