Which statement best describes the role of a clarifier in water treatment?

Which statement best describes the role of a clarifier in water treatment?

• A. It separates solids from water by allowing settled solids to accumulate while clarified water rises over the surface.
• B. It adds coagulants to improve settling.
• C. It provides the disinfection stage.
• D. It is used for air stripping of volatile compounds.

Answer: (A)

Clarifiers use gravity settling to remove solids from water. In this unit, heavier particles gradually fall to the bottom as sludge while the clearer water flows over the top, producing effluent that’s much less turbid for downstream treatment. This is exactly described as separating solids from water by allowing settled solids to accumulate while clarified water rises over the surface. The other steps—adding coagulants to improve settling, disinfection, or air stripping of volatiles—occur in different parts of the treatment process and are not the function of the clarifier.

Clarifiers use gravity settling to remove solids from water. In this unit, heavier particles gradually fall to the bottom as sludge while the clearer water flows over the top, producing effluent that’s much less turbid for downstream treatment. This is exactly described as separating solids from water by allowing settled solids to accumulate while clarified water rises over the surface. The other steps—adding coagulants to improve settling, disinfection, or air stripping of volatiles—occur in different parts of the treatment process and are not the function of the clarifier.