CONCENTRATION DEVICE FOR SLUDGE

PURPOSE:To concentrate excess sludge withdrawn from a final settling basin economically by feeding a layer of concentrated sludge by floatation and a layer of concentrated sludge by settling to a centrifugal concentrator, and feeding the mixture of the separated water and the excess sludge to the centrifugal concentrator. CONSTITUTION:A layer of floated solid matters is mixed or collected in a sludge collecting box 3d provided to an intermediate chamber Q, and then enters an external box 3e. On one hand, settled sludge is withdrawn by a pump 4 from the bottom 3c, combined with the sludge withdrawn by a pump 5 from the external box 3e and enters a tank 6. The sludge in the tank 6 is withdrawn by a pump 7 and fed to a centrifugal concentrator 8. On the other hand, an intermediate clear layer contg. only small amt. of solid matters interposed between the floated solid matters layer and the settled sludge layer is discharged through a conduit pipe 9 and fed back to a filthy water treatig facility. The solid matter content of the intermediate water in this stage is reduced to less amt. than the content of solid matter in the separated water immediately after it is discharged from the centrifugal concentrator 8.