PURPOSE: To perform stable feed of sludge by pipe line without causing damage to valve by simply separating foreign matter from sludge by locating the sludge liquor surface inside casing between sludge exhaust port and foreign matter exhaust port.

CONSTITUTION: Sludge coming into the casing 4 through sludge supply pipe is regulated its liquor surface at the position from H1 to H2 all the time by a level controller. Among the sludge in the casing 4, sludge containing foreign matters of a size smaller than the diameter of the sludge exhaust port 12 enters into a filtering area consisting of a plural number of the sludge exhaust port 12 and collected in the path 14 and then discharged to the sludge exhaust port 8. The sludge from the sludge exhaust port 8 is sent to the sludge feed pump and then to a treatment site. On the other hand, foreign matters of a size larger than the diameter of the sludge exhaust port 12 are sent up by the conveyer 5 and passed through the sludge liquor surface, where the foreign matters are separated from sludge.