What process do solids-contact process units combine?

The solids-contact process is a treatment method employed in water treatment systems to enhance the removal of suspended solids and particles from water. This process effectively integrates the stages of coagulation, flocculation, and sedimentation into a single operational unit.

Coagulation involves the addition of chemicals that destabilize the colloidal particles in the water, allowing them to clump together. This is followed by flocculation, where these clumps (called flocs) are agitated to promote further aggregation, forming larger particles that can be more easily removed. Finally, sedimentation allows the heavy flocs to settle at the bottom of the tank due to gravity, effectively separating them from the treated water.

By combining these processes, the solids-contact method improves efficiency, reduces space requirements, and minimizes the overall time needed for treatment while increasing the quality of the finished water by ensuring that most of the solids are removed effectively. Therefore, the integration of coagulation, flocculation, and sedimentation is crucial in the solids-contact process and is why this answer is the correct choice.