What units combine coagulation, flocculation, and sedimentation into a single basin?

The correct choice highlights a specific type of treatment unit known as solid contact units, which effectively combine the processes of coagulation, flocculation, and sedimentation into a single basin.

In these units, the initial coagulation process introduces coagulant chemicals to the water, which helps in agglomerating suspended particles. As the process continues, flocculation occurs where these coagulated particles are further clumped together into larger aggregates, or "flocs," through gentle mixing. Finally, sedimentation takes place within the same basin, where the denser flocs settle to the bottom under the influence of gravity, thereby clarifying the water above.

This integrated system allows for a more efficient and space-saving approach to water treatment, reducing the need for multiple separate units and streamlining operations. The design aids in minimizing the overall footprint of the treatment plant while maintaining effective removal of particulate matter, making it a practical choice in many water treatment applications.