NOVELTY - A radioactive nitrate waste disposal apparatus (10A) has denitrifying tank (12), reaeration tank (14) and sludge dissolution tank (81). Denitrifying tank accommodates activated sludge, in which anaerobic microbe is grown, and carries out adsorption of radioactive substance from nitrate waste liquid (11). Reaeration tank carries out aeration mixing of denitrifying liquid (24). Tank (81) carries out dissolution of surplus sludge (26A,26B) discharged from tanks (12,14), using sludge solubilizing agent (80). Dissolved sludge is supplied to denitrifying tank as carbon source (22).    USE - Apparatus is used for disposing radioactive nitrate waste discharged from nuclear installation, such as reprocessing plant.    ADVANTAGE - The apparatus efficiently enables disposal of radioactive nitrate waste.    DETAILED DESCRIPTION - A radioactive nitrate waste disposal apparatus has a denitrifying tank, a reaeration tank and sludge dissolution tank. The denitrifying tank accommodates activated sludge, in which anaerobic microbe capable of reducing nitric acid to nitrogen gas is grown, and carries out adsorption or absorption of radioactive substance from nitrate waste liquid containing nitric acid and radioactive substance. The reaeration tank carries out aeration mixing of denitrifying process liquid with activated sludge, in which aerobic microbe is grown. The sludge dissolution tank carries out dissolution of surplus sludge discharged from denitrifying tank and reaeration tank, using sludge solubilizing agent. The dissolved sludge is supplied to denitrifying tank as carbon source.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of disposal apparatus. (Drawing includes non-English language text)    Disposal apparatus (10A)    Nitrate waste liquid (11)    Denitrifying tank (12)    Reaeration tank (14)    Carbon source (22)    Denitrifying process liquid (24)    Surplus sludge (26A,26B)    Sludge solubilizing agent (80)    Sludge dissolution tank (81)