PURPOSE: To enable the successive discharge of sludge and the sufficient mixing of the sludge and a solidificating material to be carried out, by inserting the inlet opening of the first jet pump to a sludge layer so as to absorb sludge, next discharging the absorbed sludge into a settling tank by the second jet pump in which the mixed liquid of water and a solidificating material is used for a driving fluid.

CONSTITUTION: The discharge opening of the first jet pump 1 is connected with a carrying pipe, the discharge opening of this carrying pipe is opened into a settling tank 3, an equipment in which the second jet pump 2 is intervened in the middle of the carrying pipe is utilized. And the inlet opening of the first jet pump 1 is inserted to a sludge layer so as to absorb sludge 12, net the absorbed sludge is discharged into the settling tank 3 by the second jet pump 2. Thus, the second jet pump 2 uses the mixed liquid of water 4 and a solidificating material 5 for a driving fluid as well as the sludge can be discharged successively from a river bed by the jet pumps, so that the sludge 12 and the driving fluid are mixed powerfully each other in the carrying pipe, and the sludge 12 and the solidificating material 5 can be sedimented to the settling tank 3 in a sufficiently mixed condition.