GB1403186A - Sludge deliquification - Google Patents

Abstract

1403186 Filter or drainage bed EN-TOUTCAS LTD 7 July 1972 [7 July 1971] 31986/71 Heading B1D [Also in Division F4] A filter or drainage bed for dewatering sludge comprises a trough having brick walls 1 enclosing a drainage bed 2 of broken or crushed stone, hard clinker, gravel or other hard core having land drain pipes 4 embedded therein and covered by a layer 5 of porous nofines concrete of single sized aggregate of ¢"- 1" nominal grade. A filtering layer 7 of gravel or sand may be applied to the concrete surface before each filtering cycle and removed with the sludge after filtration. The concrete layer has a level and even surface to facilitate sludge removal. The no-fines concrete suitably uses gravel or broken granite aggregate and binders of portland cement, rapid hardening cements, cements with plastics or other chemical additives, synthetic resins or bitumen. Instead of a single concrete layer, a plurality of layers of increasingly coarse aggregate in the direction of flow through the bed may be used with one or more of the layers being formed of prefabricated slabs or beams of the no-fines concrete.