WASTEWATER
What are two types of solids effectively removed by primary clarifiers?
A. Floatable and settleable
B. Floatable and dissolved
C. Dissolved and colloidal
D. Suspended and organic
Answer: A. Primary clarifiers are very effective at removing floatable and settleable solids. Floatables include objects and debris that are buoyant. Fats, oil and grease (also called FOG) are included, and primary clarifiers are well-adapted for these substances. Also included in floatable solids are paper products, plastic wrappers and products, fruit and vegetable seeds, soaps, and detergents. Much of the floatable material removed by a primary clarifier is inorganic. Settleable material is negatively buoyant (denser than water).
