The difference between sedimentation tank and clarifier is as follows:

Processing method: 

The sedimentation tank mainly relies on the particles in the water to sink due to gravity being greater than buoyancy, thereby separating them from the incoming water. The clarifier utilizes natural sedimentation and physical separation to separate suspended solids and some dissolved substances in the water, providing preliminary water purification.

Chemical reagents: 

Chemical reagents are generally required in the clarifier to generate flocculants, which is the "coagulation" step. No chemical reactions or reagents are involved in the sedimentation tank.

Separation method: 

In the clarifier, the separated clear water flows upward and is collected through channels, while the settled mud and sludge partially refluxes and mixes with the original water for mechanical mixing and reaction, and partially undergoes concentration and is periodically discharged. The sedimentation tank relies primarily on gravity for separation of suspended solids and water.

Processing efficiency: 

The clarifier typically has a higher processing efficiency as it simultaneously completes mixing, reaction of water with flocculants, and separation of flocculants from water. The sedimentation tank has a relatively lower processing efficiency as it relies on natural sedimentation for water purification.

Applicability: 

The clarifier has a strong adaptability to changes in water quantity and ion concentration in water, providing stable treatment effects and is widely used in various water treatment scenarios. The sedimentation tank is more commonly used for simple removal of suspended solids with relatively poorer treatment effects.

In summary, sedimentation tanks and clarifiers are important water treatment facilities, but they differ in their treatment principles, methods, efficiencies, and applicability. In practical applications, appropriate facilities should be selected based on water quality conditions and treatment requirements.