NOVELTY - A radioactive nitrate waste disposal apparatus (10A) has denitrifying tank (12A) and reaeration tank (14). 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) with activated sludge. Denitrifying tank has pH control unit, carbon source supply unit, solid-liquid separation unit (25) and gas supply unit. Reaeration tank has solid-liquid separation unit (28) and air supply unit.    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 and a reaeration 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 denitrifying tank has a pH control unit for supplying pH adjuster (21) capable of adjusting pH of nitrate waste liquid, a carbon source supply unit for supplying carbon source (22) to denitrifying tank, a primary solid-separation unit and gas supply unit. The separation unit separates denitrified process liquid and solid content containing sludge. The gas supply unit supplies oxygen-free gas to denitrifying tank, and is provided in lower portion of separation unit. The reaeration tank has secondary solid-liquid separation unit for separating denitrified liquid into surplus sludge and process liquid (27), and air supply unit for supplying air to reaeration tank, and provided in lower portion of separation unit.    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 (12A)    Reaeration tank (14)    Agent for adjusting pH (21)    Carbon source (22)    Denitrifying process liquid (24)    Solid-liquid separation unit (25,28)    Process liquid (27)