METHOD AND PLANT FOR THICKENING SLUDGE DERIVED FROM WATER TREATMENT BY FLOCCULATION-DECANTATION WITH BALLASTED FLOC

摘要

The invention concerns a method for thickening sludge derived from a water treatment plant by flocculation- decantation with floc ballasted with micro-sand or other dense granular material using a liquid cyclone treatment (1) of the decantation sludge. The invention is characterised in that it comprises successive steps which consist in: degassing (3) the overflow sludge of the liquid cyclone treatment (1) from the ballasted flocculation-decantation unit, said degassing step being carried out on a corresponding degassing surface at a degassing surface velocity of less than 100 mph; injecting at least a flocculating reagent (4) into said sludge; and thickening said sludge in at least a laminar sludge thickener (6), with a stilling floor load calculated at the thickener floor surface higher than 200 kg of suspended matter per m^2 per day and the extracted sludge concentration higher than 10 g/l.