Correct option is D
Primary Treatment Units:-
• Screening
• Detritus tank
• Sedimentation tank
• Skimming tank
Skimming tank:-A skimming tank is a chamber so arranged that the floating matter like oil, fat, grease, etc., rises and remains on the surface of the wastewater (Sewage) until removed, while the liquid flows out continuously under partitions or baffles.
Therefore, this process in a skimming tank is known as skimming.
Detritus tank:-The function of the detritus tank to remove finer organic and inorganic particles.
practically, the detritus tank is similar to a grit chamber. To only difference is that the grit chamber is
meant for removing the larger particles and the detritus tank is meant for removing finer particles.
Sedimentation tank:- A sedimentation tank is a chamber in which settling of the heavy suspended
particle is done.
Screening :- Screening is used to remove large size stones and gravels.
