ACTIVATED SLUDGE SEWAGE TREATMENT PROCESS AND SYSTEM

摘要

1385822 Activated sludge process AIR PRODUCTS & CHEMICALS Inc 15 March 1972 [18 March 1971 14 Feb 1972] 12045/72 Heading ClC An apparatus for treating waste liquid by the activated sludge process comprises an enclosed aeration zone to which is supplied oxygen-rich gas containing at least 35% oxygen, and an aeration zone which is open to the atmosphere and in which liquid is mixed with atmospheric air or oxygen-lean air. The enclosed aeration zone may comprise a chamber divided into subchambers by partitions of a number of interconnected separate chambers. The open aeration zone may comprise more than one chamber. In operation at least 25% of the biological oxygen demand of the liquid is satisfied in the enclosed aeration zone. The dissolved oxygen content is maintained at least 3 p.p.m. in at least part of the enclosed aeration zone. In Fig. 1 in enclosed aeration zone 12 waste liquid from line 16 and sludge recycled from settler 18 is mixed and aerated with oxygen-rich gas from source 51. Gas is removed from zone 12 and pumped through diffusers 56. Gas is vented from zone 12 under the control of valve 55 when the oxygen content of the gas in the zone is below a predetermined value. The waste liquid is subsequently aerated with atmospheric air in the zone provided with surface aerators 60 and settled in settler 18. The enclosed zone may be provided with surface aerators.