Where is Lime Added in Water Treatment Plants?

Water treatment plants are designed to remove impurities and contaminants from water to make it safe for human consumption. The treatment process involves several stages, including coagulation, sedimentation, filtration, disinfection, and, in some cases, pH adjustment. Lime is one of the common chemicals used in water treatment plants to adjust the pH level of water.

What is Lime?

Lime is a white, caustic, alkaline substance that is obtained by heating limestone or seashells in a kiln. It is also known as calcium oxide (CaO). In water treatment plants, lime is used in its hydrated form, known as slaked lime, which is obtained by adding water to quicklime. Slaked lime has a chemical formula of Ca(OH)2 and is commonly used in water treatment plants because of its ability to raise the pH level of acidic water.

Why is Lime Added in Water Treatment Plants?

Lime is added in water treatment plants to adjust the pH level of acidic water. Acidic water is corrosive and can damage pipes, fixtures, and other components of the water distribution system. By raising the pH level of water, lime reduces its corrosiveness and increases its ability to inhibit the growth of harmful bacteria and viruses. In addition, lime has a coagulation effect that helps to remove impurities and contaminants from water during the treatment process.

Where is Lime Added in the Water Treatment Process?

Lime is typically added to the water treatment process after coagulation and sedimentation but before filtration and disinfection. Coagulation involves adding chemicals such as aluminum sulfate or ferric chloride to water to form flocs, which are clusters of impurities that can be easily removed. Sedimentation involves allowing the flocs to settle to the bottom of a tank or basin, where they can be removed. After coagulation and sedimentation, lime is added to raise the pH level of the water and help to flocculate any remaining impurities.

After the addition of lime, the water is passed through a filtration system to remove any remaining impurities. Filtration involves passing water through sand, gravel, or other materials that trap impurities and contaminants. Finally, the water is disinfected with chlorine or other chemicals to kill any remaining bacteria and viruses. Disinfection is a crucial step in the water treatment process to ensure that the water is safe for human consumption.

Conclusion

Lime is an important chemical used in water treatment plants to adjust the pH level of water and help remove impurities and contaminants. It is typically added after coagulation and sedimentation but before filtration and disinfection. By raising the pH level of acidic water, lime reduces its corrosiveness and increases its ability to inhibit the growth of harmful bacteria and viruses. Water treatment plants play a crucial role in ensuring that the water we drink is safe and free from contaminants.