GB1311819A - Treatment of sewage - Google Patents

Abstract

1311819 Sewage treating plant SOUTH AFRICAN INVENTIONS DEVELOPMENT CORP 19 April 1971 [8 April 1970] 24525/71 Heading B1D [Also in Division Cl] Sewage flows along a series of endless channels 12 to 26 each connected to its neighbours at diametrically opposed points to maximise the total length of the flow path. Channels 12 to 18 have rotary disc aerators to agitate and activate the sewage, which flows from channel 18 into channel 20 through a float-controlled sluice. As illustrated in Fig. 1 (not shown) channels 12 to 18 are oval and channels 20 to 26 circular in plan. A second set of channels 20 to 26 may be provided to the right of Fig. 1. Channels 20 to 26 are settling channels spanned by a rotating bridge 65 carrying air lift pumps 66 to 72 which withdraw settled sludge and deliver it via pipe 74 to a central sludge channel 30. Chains (86 to 92) trail behind the pump inlets to agitate the floor layer of sludge and release gas therefrom. Flocculant could be added to channel 24 and mixed by means suspended from the bridge, and chlorine may be added to channel 26. Clarified liquid flows from channel 26 via passage (46) into the upper part of a channel 28 which encloses a downward flow sand bed filter 96, 98. Filtrate flows from space 100 through normally stationary pump 104 (Fig. 3) into a reservoir 108, 110, and periodically, under control of a float-switch above bed 96, pump 104 is switched on pumping filtrate upwards through the bed 96 until a timer switches it off. The filtrate thus used to backwash the filter flows over wall 122 into sludge channel 30, a one-way valve preventing flow back into channel 26. The sludge and liquid from channel 30 may return via conduit 128 to aeration channel 12 or may be discharged via conduit 126. Weir 112 in the reservoir prevents the liquid level in filter channel 28 falling below the top of bed 96 therein.