PURPOSE: To enhance dehydration efficiency by providing a brake member on the wall of the accumulation channel of a drip drum for separating the liquid of washed waste and changing the passing cross section of the waste to adjust the compression stress applied to the waste.

CONSTITUTION: An accumulation channel 19 is provided to a drip drum 12 and a brake part consisting of two cams 21 is provided to the wall constituted of an elastic member of the channel. Therefore, the dehydrated waste passing through the accumulation channel 19 is restricted in its amt. and the passing amt. of the waste compressed by a screw 15 is adjusted and the waste is efficiently dehydrated by a dehydration means 14. The dehydrated and decomposed waste is blown off by a blower 29 to be sent to a drying drum 33 from an exterior part 32 and dried and the pretreatment of the waste is made compact.