GB570078A - Purification of liquids - Google Patents

Abstract

570,078. Treating sewage, &c. TRIGGS, W. W. (Dorr Co., Inc.). Dec. 11, 1942, No. 17668. [Class 111] In the treatment of sewage, &c., the liquid containing gas is treated in a vacuum flotation apparatus 11, as described in Specification 570,076, and the scum and sludge are passed through pipes 80, 81 respectively to a digestion tank 60, supernatent liquor being returned from the latter through a pipe 67 for retreatment in the apparatus 11. A branch pipe 671 allows the gasification tank 40 to be bypassed. A large tank 60 may be provided with rotary sludgeimpelling arms 61. The digested sludge is passed to a dewatering station 63 comprising filtering equipment and means for adding a coagulating chemical or other filter aid prior to filtration or a centrifuge, the separated liquid being removed through a pipe 70, preferably connected to the pipe 67, and the sludge cake being passed to a flash dryer or incinerator 68, preferably heated by digester gas supplied through a pipe 66. Gas and vapour from the tanks 40, 11 may be conducted through a pipe 49 to the incinerator for deodorization and a damper 72 may be provided in the stack 73 to permit the supply of stack gases through a pipe 74 by means of a compressor 44 to the gas-diffusing tiles 42 in the tank 40. The liquid level in the tank 11 relative to the ramp 82 and hopper 16 of the scum-removing means may be varied as by an adjustable nozzle 27, arranged in an auxiliary chamber 24 and connected to a wet vacuum pump 26, for controlling the concentration of the scum. The effluent from the tank 11 is withdrawn through a pipe 30 from below a baffle 31. The influent liquid may be passed through a disintegrator or screen 84 and a grit washing station 85, and coagulants, such as alum or ferric chloride, may be added through a pipe 83. If no chemicals be added, an impellor aerator may be provided in the tank 40 instead of the tiles 42. Inert gas is used with a liquid having a high biological oxygen demand.