WATER TREATMENT METHOD BY BALLASTED FLOC INCLUDING A RECYCLING OF GRANULAR MATERIAL

摘要

The invention concerns a flocculation-decantation method by ballasted flocs using a granular material and a step which consists in treating the sludge derived from flocculation-decantation in a circular grit trap wherein the auxiliary liquids tangentially injected into the sludge substantially in the same direction as the latter. The invention also concerns a circular grit trap with a cylindrical part of diameter D tangentially supplied with the suspension to be treated and a conical part and provided with a cylindrical chamber injecting wash-water provided at the conical part outlet and having a diameter D' ranging between 0.35 D and 0.65 D, said cylindrical chamber having at least a tangential supply of auxiliary liquid along the same feeding direction as said tangential supply of the suspension to be treated.