What is the process of water supply purification which consists of applying certain chemicals in particles too small to be removed by plain sedimentation?

Coagulation is the process of water supply purification that involves the addition of chemicals to the water to facilitate the agglomeration of small particles. When coagulants, such as aluminum sulfate or ferric chloride, are introduced to the water, they neutralize the charge of the suspended particles, allowing them to cluster together into larger aggregates known as flocs. These larger particles can then be more easily removed through subsequent processes like sedimentation or filtration.

This method is particularly important in water treatment because plain sedimentation alone may not effectively remove very fine particles that are smaller than what can be settled out under gravity. Coagulation enhances the removal efficiency by increasing the size of those particles, enabling them to settle more readily or be filtered out from the water. It forms a critical step in the water purification process when dealing with turbid water, ensuring that contaminants and impurities are adequately removed before the water is deemed safe for consumption.

In contrast, sedimentation pertains to the settling of particles under gravity, filtration involves the passage of water through a medium that traps particles, and screening refers to the removal of larger debris prior to treatment. While these processes are integral components of the overall water treatment strategy, coagulation specifically targets those particles that are too small for