PURPOSE: To enhance the treating capacity of soft sludge, by providing a water permeable line body which is moved in a soft sludge storage tank and taken up to the outside and a means for removing soft sludge adhered to said line body out of said tank as the movement thereof to accelerate the precipitation speed of said soft sludge.

CONSTITUTION: A main apparatus as the precipitation treatment part of a soft sludge treating vessel is constituted from a soft sludge storage tank 30, winders 15, 15', washing machines 16, 16' as soft sludge removing means and rope like or narrow strip like water permeable line bodies 17, 17'. In this apparatus, the line bodies 17, 17' provided under tension in the storage tank 30, into which sludge 4 is introduced, are moved by the winders 15, 15' and drive pulleys and sludge adhered to the line bodies 17, 17' is removed by the adhered sludge removing means such as the washing machines 16, 16' provided to the outside of the storage tank 30. As the resut, the clogging of the line bodies 17, 17' are prevented as well as consolidation promoting effect of the sludge 14 is held and the precipitation speed of consolidated sludge can be accelerated.