What is identified as the chief factor in the clarification process of still water?

The chief factor in the clarification process of still water is sedimentation. Sedimentation is the natural process where suspended particles in the water settle to the bottom due to gravity. This process is crucial in the treatment of still water, as it effectively reduces the concentration of turbidity and allows for the removal of larger particles, leading to clearer water.

In the context of water treatment, sedimentation occurs in sedimentation tanks where the flow of water is slowed down, allowing time for particles to settle out. This is an essential step in water clarification systems, as it helps to prepare the water for further treatment processes by removing solid contaminants.

The other factors, while they might play a role in water treatment, do not serve as the primary mechanism for clarification in still water. For instance, dilution might reduce concentration but does not specifically address the removal of particles. Infiltration refers to the process of water entering the soil but is not directly related to water clarification in a controlled setting. Aeration introduces air into the water, which can help oxidize certain contaminants but is not primarily involved in the sedimentation process that clarifies still water.