PURPOSE: To simplify the whole structure and facilitate the operation by a structure wherein a fluidized drying furnace and a fluidized incineration furnace are systematically combined and the combustion gas produced in the incineration furnace is diluted with the air and then supplied to the drying furnace and stillfurther the waste gas of the drying furnace is supplied to an aeration tank.

CONSTITUTION: The waste water treated sludge 1 dehydrated to the order of 70W 90% of water content is sent to the fluidized drying furnace 3 by a pressure feeding means 2. In the fluidized drying furnace 3, the raw sludge is fluidizedly contacted with the hot drying gas made by diluting the whole amount of combustion gas 6 from the fluidized incineration furnace 5 by 10W15 times with the air to be dehydrated to the order of about 50W60% of water content. The resultant dried sludge 8 is sent to the fluidized incineration furnace 5 and fluidizedly burnt with the air 9 and the combustion gas 6, after the ash being separated, is flowed back to the drying furnace 3. The waste gas 11 discharged from the drying furnace 3, after the sludge 12 being separated, is sent to the aeration tank 13 in which the deodorization treatment of the waste gas 11 is also performed.