TREATMENT OF SEWAGE IN SPETIC TANK

摘要

PURPOSE:To effectively perform decomposition, nitrification and denitrification of organic substance contained in sewage by reducing supply of air into a contact aeration tank from a diffuser and, furthermore, performing biological treatment while returning treated water in the contact aeration tank to an anaerobic filter bed tank. CONSTITUTION:In the daytime wherein a septic tank 1 is in an ordinary inflow loaded condition, air is always supplied from the diffusers D1, D2 in a first and second chambers E1, E2 of a contact aeration tank. Thereby ordinary aerobic treatment is performed in the first and second chambers E1, E2 of the contact aeration tank. Then, in the nighttime wherein inflow load is reduced, supply of air from the diffusers D1, D2 is intermittently stopped by a built-in timer 4t of a blower 4 for air blow. Air is always supplied quantitatively to an air lift pump A from a blower 5 for air lift. Nitrification liquid and peeled sludge contained in treated water are returned to a first chamber N1 of an anaerobic filter bed tank via a return path B from the contact aeration tank E.