Patent GB-570076-A (GB)
Title: Improved method and apparatus for the removal of suspended particles from liquid media
IPC: B01D21/00
Filed: 1942-11-20
Abstract: 570,076. Treating sewage, &c. TRIGGS, W. W. (Dorr Co., Inc.). Nov. 20, 1942, No. 16456. [Classes 46 and 111] Suspended particles are removed from sewage and other wastes or liquids by maintaining a main body of liquid under treatment by continually supplying thereto liquid containing gas, maintaining a second body of liquid, which receives liquid from, and has a common atmosphere with, the main body, producing and maintaining above the surface of the liquid bodies a degree of reduced pressure or vacuum, such as to be effective within a region of predetermined depth from the surface of the main body to hold the floatable particles at, or float them to, the surface through the medium of the gas bubbles in the supplied liquid, by applying suction above the second body through an intake so disposed as to with- . draw liquid or gas according to the level of the liquid and thereby render the latter substantially constant and separately discharging the floating particles and the clarified liquid in a manner preventing impairment of the reduced pressure by ingress of air. In the apparatus shown, the gas-containing liquid is supplied by a draught-tube 56, 58 opening within the effective range of the reduced pressure below the surface of the main body of liquid in a tank 10. Clarified liquid passes under a partition 108 and overflows a weir 20 into a launder 22 communicating through a passage 24 with a chamber 26 from which depends a conduit 30 into a pool of liquid 32 in a tank 34 to form a barometric leg for the effluent passing to a discharge pipe 38. The chamber 26 is also connected by a pipe 28 with the top of the tank. A wet vacuum pump 40 is connected with a pair of adjustable intake nozzles 46 for withdrawing gas or liquid from the chamber 26 according, to the liquid level therein, the discharge pipe 41 of the pump being connectable by a valve 43 with the tank 10 or a discharge pipe 47. The upper part 58 of the draught-tube is: connected by webs 62 to a vertically-adjustable shaft 64 rotated through reduction gearing 68, 69 by a motor M. Resilient blades 90, carried by arms 88 on the shaft 64, sweep the scum over an inclined ramp into a hopper 94 leading to a pipe 96 extending into a pool of liquid 98 in a tank 83 to form a barometric leg. Sediment in the tank 10 may be directed by blades 74, carried by arms 72 on the tube section 58, to a sump 16 connected by a pump 78 with a sump 82 leading to a discharge pipe 84. Sediment or scum overflowing into a sump 102 may be removed by a pump 106. If the liquid to be treated does not contain sufficient gas, it is first passed through an aerating or gassing chamber 120 and then through chamber 124 to remove large gas bubbles, an inert gas being used where the liquid has a high biochemical oxygen demand. The degree of vacuum should be at least equivalent to 7 ins., and preferably to 9 ins., of mercury, the mouth of the tube 58 being located about 15 ins. below the liquid level and the partition 108 extending down to a region where the degree of vacuum is equivalent to, or below, about 5 ins. of mercury. In modifications, (1) the incoming liquid is sprayed on to the liquid 'in the tank, (2) scum only is removed and the non-floatable solids are discharged in the effluent and (3) the effluent is discharged independently of the chamber 26, the bottom of the latter being connected with the tank 16 below the liquid level therein.