What is coagulation in water treatment?

Coagulation in water treatment refers to the process of adding chemicals, often referred to as coagulants, to water in order to facilitate the clumping together of fine particles and impurities. This is an essential step in the water treatment process where small suspended particles, such as dirt, organic matter, and microorganisms, are neutralized and formed into larger aggregates called flocs. These flocs can then be removed more effectively in subsequent treatment steps, such as sedimentation and filtration.

The use of coagulants, such as alum or ferric sulfate, alters the surface charge of these particles, promoting their agglomeration. As the particles clump together, they become heavy enough to settle out of the water through gravity, thus clearing the water of impurities.

This process is crucial because it significantly enhances the effectiveness of subsequent treatment stages, leading to cleaner, safer drinking water. It contrasts with other processes like sedimentation, where the settlement happens naturally without prior chemical treatment, or filtration, which physically removes particles without aiding their initial clumping.