Intermediate/Final Clarifiers

The intermediate or final clarifier tanks provide detention time for the “sloughings” to settle to the bottom of the tank as sludge.  Slow moving ploughs collect and direct the sludge to a center sump.  This sludge, known as secondary sludge, is pumped back to the head of the plant where it settles in the primary clarifiers, and is then pumped with primary sludge to anaerobic digesters. Removal efficiencies of the trickling filters and intermediate/final clarifiers are BOD- 50-80%, NH3-N (ammonia nitrogen as nitrogen) 60-80%, and TSS 40-60%.