GB415775A - Method of and means for treating and purifying sewage - Google Patents

Abstract

415,775. Treating sewage. COOMBS, J. A., 12, Princes Park Avenue, Golders Green, London, and HEDGE, W., 213, Dartford Road, Dartford, Kent. March 2, 1933, Nos. 6349/33 and 7367/34. [Class 111.] In treating sewage by the activated sludge process, the mixed liquid and activated sludge is brought at least twice into contact with air at a free surface and at successively higher pressure, the air from the higher pressure stage being used at the lower pressure stage. The liquid may be heated at any stage. Sewage and activated sludge passing respectively over measuring weirs 13, 15, Fig. 1, mix in an open tank 11 and the mixture passes successively through closed cylindrical tanks 10. From the lowest tank 10 it passes to a settling tank 17, from which effluent liquid is discharged through a pipe 34, scum and grease through a pipe 32 and settled sludge through a pipe 19 to a closed regenerating tank 20. Air from a main 23 enters the tank 20 through diffusers 22. The air collecting above the sludge in the tank 20 is admitted to diffusers 22 in the lowest tank 10 through pipes 26 controlled by a valve 27. That collecting in the lowest tank 10 is similarly passed to the tank above and so on throughout the series. The regenerated sludge is raised by an air lift through a pipe 21 and passed to the weir 15. In the plant shown in Fig. 3 the air used passes successively through two tanks 45 containing slate or similar material, a sludge regenerating tank 42 and two treatment tanks 37. The sewage passes successively through the tanks 37 and then into a settling tank 40. Effluent from the settling- tank passes successively through the tanks 45 and is discharged to a trough 47. Sludge from the settling-tank is raised to the tank 42 and after regeneration passes to the upper tank 37. A cylindrical tank 50, Fig. 4, contains a series of inverted trays 54, 53 attached alternately to the wall of the tank and to a central flume 52. At the top of the series is a deeper tray 60 with air diffusers 61 on the top. Pipes 56, 57 deliver sewage and sludge respectively on to a deflector 55 and the mixture takes a sinuous path downwards around the trays 53, 54 contacting with air confined beneath the trays. The mixture is circulated up the flume and over a weir 58 at the top by an air lift 59 or by a centrifugal pump at the top of the flume. The mixture is withdrawn from the flume 59 through a pipe 69 delivering at an outlet 70 into a settling tank 71. Sludge from the tank 71 is raised by an air lift through a pipe 68 to the pipe 57. Pipes 63, 64 deliver air to one or more of the trays : adjacent trays may be connected by air pipes projecting under the lower tray. Diffusers may be provided above the trays. A continuous spiral may be substituted for the trays. In another modification the flow of sewage may be from side to side of a rectangular tank under trays of rectangular shape. Specification 21976/14, [Class 111], is referred to.