TREATMENT OF SEWAGE

摘要

1,272,294. Activated sludge process. SOUTH AFRICAN INVENTIONS DEVELOPMENT CORP. 28 May, 1969, No. 26956/69. Heading C1C. Raw sewage and activated sludge are agitated in a tank 12.1 after which a portion of the contents of this tank are transferred to a settling tank 14, from which settled sludge is removed, and the remainder of the contents are transferred to an aeration tank 12.2 from a higher level than that from which the portion of the contents of the agitation tank is transferred therefrom to the settling tank. The agitation may be effected by stirrers, rotating discs or by partial aeration. A portion of the effluent from the aeration tank 12.2 may be returned to the influent sewage via line 24 and the activated sludge may be directed from a settling tank 20 to the influent sewage via line 21 and to the aeration tank via line 26. Sludge discharged from the settling tank 14 may be transferred to an anaerobic digester 18. The rate of flow of liquid from the agitation tank 12.1 to the settling tank 14 may be controlled by adjusting the rate of sludge discharge or, Fig. 3 (not shown), of effluent flow from the settling tank 14 to the aeration tanx 12.2 via line (16.1). Some of the sludge from the settling tank 14 may be returned to the agitation tank 12.1 via line (17.1). The agitation tank 12.1 and aeration tank 12.2 may be in the form of one or more endless channels surrounding both settling tanks 14, 20, Fig. 2 (not shown).