GB878099A - Improved method and apparatus for the filtration of undigested sewage sludge - Google Patents

Abstract

878,099. Treating sewage. KOMLINESANDERSON ENGINEERING CORPORATION. June 10, 1958, No. 18547/58. Class 111. Raw sewage passes through a grit chamber 10 and a bar screen or communicator 11 to a settling tank 12, from which the sludge is withdrawn directly, without digestion, by a pump 15 through a closed conduit to which lime is supplied from a feeder 16 in a proportion dependent on the flow of sludge to the pump ; a suitable proportion is 6-12%, based on the weight of dry solids. The pump delivers the sludge to a rotary-drum vacuum filter 18 fitted with a relatively coarse filtering medium e.g. having interstices between 0.01 and 0.028 inch diameter, on which a layer of solids builds up, through which the sludge is filtered. The filtering medium may be of polyvinylidene chloride or polytetrafluoroethylene and may be in the form of a series of filaments which are removed from the drum with the cake, or in the form of a coarsely woven fixed fabric from which the coke is removed by scrapers or strings. The filtrate from the filter is returned to one of the parts 10, 11, 12 and the filter cake may be used directly as a fertilizer or may be dried or incinerated. Optional features of the installation comprise (1) the provision of more than one ball check valve 17, 17<SP>1</SP>, in both the supply line to the pump 15 and the discharge line therefrom, to reduce stoppages caused by the blocking of a valve, (2) the provision of means for supplying additional reagents, e.g. ferric chloride, between the tank 12 and the filter 18 ; such reagents may be added before or after the lime or at an intermediate point between two stages of lining, and (3) the provision of an oxidation unit 13 and a second settling tank 14, for further clarification.