Imhoff Tank

Name:
Imhoff Tank
Detailed information:
A reinforced concrete structure of considerable size (approximately 35 ft high) designed especially for sewage clarification. Its principal features are (1) an upper or sedimentation compartment in which in-flowing sewage deposits its suspended solids by gravity (residence time 2–3 hours), the free water being drawn off through an outlet, and (2) a separate lower compartment in which digestion of the accumulated sediment (sludge) takes place. The sludge is passed from the upper compartment to the digestion chamber through an inclined slot or channel. The gases generated by digestion are released through suitably located vents. The digested sludge is removed through outlet pipes at intervals of about 6 months. The dried sludge contains 2–3% ammonia and 1% phosphoric acid, which make it suitable as a soil conditioner.See Sewage Sludge.