GB542008A - Improvements in or relating to a process and plant for the treatment of sewage and the like - Google Patents

Abstract

542,008. Filters. COOMBS, J. A. June 18, 1940, No. 10505. [Class 46] Sewage or other impure liquid to which activated sludge has been added is forced through a filter bed comprising filtering media in the form of balls and through which the passage of air is promoted. The activated sludge may be that obtained from a sewage treatment plant as described in Specification 514,627 and the process is applicable for the treatment of partially purified effluent from such a plant. The balls may have pitted surfaces and may be of stone, concrete, brick, synthetic resin or similar mouldable material. The plant shown in Fig. 1 has two filter beds 10, 11 through which the liquid passes successively, the bed 10 serving to flocculate impurities and the bed 11 to mitrify them. The beds are supported on false floors 14 of perforated and corrugated sheeting or tiles and comprise alternate layers of coarser and finer media, the lowest and coarsest consisting of balls having a diameter roughly equal to the pitch of the corrugations. Impure liquid and activated sludge are distributed over the bed 10 by a travelling distributer 27, drawing siphonically from a trough 25 to which they are supplied through pipes 24, 24a respectively. Filtrate from the bed 10 passes to a well 32 to which activated sludge is supplied through an inlet 33. The liquid is raised from the well to a trough 35 by an air lift and distributed thence over the filter 11. Pipes 41 opening below the floors 14 may be connected to suction pumps and blowers for drawing atmospheric air downwardly through the beds or for passing air, which may have been dried and heated to a temperature of 100‹ to 150‹F. as described in Specification 521,895, upwardly through the beds. In the latter case the air pressure may be automatically regulated according to the amount of sludge accumulated in the upper portion of the bed. The beds may be in a concrete structure sunk below ground level with runways for bringing and removing the media. To facilitate removal of the bed a gantry ,40 carrying a mechanical labourer or elevator as described in Specifications 496,637 and 521,939, [Group XXX], may extend across the beds. As shown in Fig. 3, the filtrate from the bed 10 before distribution over the bed 11 is passed through an intermediate filter in the form of an endless travelling mat 46. The filtrate from the upper run of the mat collects in a sump 47 and is passed by a pipe 48 to the bed 11. Sludge removed from the mat by a brush 49 and by air blown through perforations in a hollow shaft 50 is collected in a sump 51 and discharged by a worm conveyer to trucks 52, Modified plant is described which comprises a tank in which sludge, removed from the sump below the front filter by scrapers as described in Specification 514,662, is activated under pressure for use in the plant. It is stated that the plant may be mounted on a movable carriage.