GB662647A - Improvements in and relating to sewage treatment - Google Patents

Abstract

662,647. Sewage treatment. GRIFFIN, J D. Aug. 6, 1948 [Aug. 15, 1947], No. 20787/48. Class 111 Sewage having a solid constituent and a watery constituent much in excess of the solid constituent is fed to the bottom of a tank 2 as by conduit 3 thereby causing an upward flow through the tank which flow is so ccntrolled, as by valve 4, that the solid part slows down relatively to the liquid, and forms in the tank a body of retained sludge which is treated by means of bacterial action while it is being displaced from below by the sludge of the incoming sewage and through all of which the water constituent flows upwardly and so washes the sludge and maintains the bacteria in an active state. The constituents may be progressively withdrawn from the upper portion of the tank together as through the overflow trough 11 and pipe 10, or the sludge may be removed from the top of the sludge body as through the channel 7 and pipe 8 below the liquid overflow trough 11 and pipe 10. The flow of the sludge should be such that it remains in the tank for a sufficient period to bring about the digestion. The sludge and liquid withdrawn together as through the pipe 10 may be subjected to aerobic treatment in which case it is fed, as through a valve 17, Fig. 4, to a sludge drying bed 18a and the drainage from the bed is fed by pipe 16 to an enforced ventilation biological filter 18. Purified effluent from the filter 18 may be recirculated through the retained sludge in the tank 2 as by pipe 21 feeding effluent from the filter to sewage entering the tank. In an alternative form of tank 2 the top converges towards the outlet for the liquid and the sludge outlet may be located at the commencement of the converging portion. Any detritus settling at the bottom of the tank 2 may be withdrawn as by pipe 23.