How does clarification make drinking water clearer?

Clarification makes drinking water clearer by removing suspended impurities that cause turbidity and color. This process typically involves a sequence of steps designed to aggregate and extract particles that are too small or light to settle on their own.12

• Coagulation and Flocculation: Chemicals called coagulants, such as aluminum sulfate, are added to the water to neutralize charges on suspended particles, allowing them to clump together. Through rapid mixing followed by gentle flocculation, these particles form larger, heavier masses known as "floc".23
• Sedimentation: The water then enters a sedimentation basin, where the heavy floc settles to the bottom as sludge, which is then removed.34
• Filtration: Because sedimentation cannot remove all impurities, the water undergoes filtration. Water is passed through porous media, such as sand, anthracite, or garnet, which traps remaining suspended particles, microorganisms, and color, resulting in clear water.1

By systematically removing these solids, clarification ensures the water is sufficiently clear for effective final disinfection.15