Patent Number: 
Section: claims

1. An apparatus for treating a radioactive nitrate waste liquid, comprising:a denitrification tank that accommodates active sludge which adsorbs or takes in a radioactive substance in a nitrate waste liquid containing nitrate and the radioactive substance and in which an anaerobic microorganism that reduces the nitrate to nitrogen gas grows; anda reaeration tank that aerates and mixes a denitrification-treated liquid treated in the denitrification tank with active sludge in which the aerobic microorganism grows, whereinthe denitrification tank includes:a pH adjusting unit that supplies a pH adjuster used for adjusting pH of the nitrate waste liquid;a carbon-source supplying unit that supplies a carbon source to the denitrification tank;a first solid-liquid separating unit that separates a denitrified liquid treated with the active sludge into a sludge-containing solid content and a denitrification-treated liquid; anda gas supplying unit that is arranged on a lower side of the first solid-liquid separating unit and supplies gas not containing oxygen into the denitrification tank, andthe reaeration tank includes:a second solid-liquid separating unit that further separates the denitrification-treated liquid treated with the active sludge into a sludge-containing solid content and a treated liquid; andan air supplying unit that is arranged on a lower side of the second solid-liquid separating unit and supplies air into the reaeration tank. 2. The apparatus for treating a radioactive nitrate waste liquid according to claim 1, wherein pH of the denitrified liquid in the denitrification tank is from 7.0 to 10.0. 3. The apparatus for treating a radioactive nitrate waste liquid according to claim 1, wherein the denitrification tank includes a gas circulating line through which nitrogen gas and carbon dioxide gas produced by a reaction between the anaerobic microorganism and the nitrate in the denitrified liquid are circulated into the denitrification tank. 4. The apparatus for treating a radioactive nitrate waste liquid according to claim 1, further comprising:a pH sensor that measures pH of the denitrified liquid; anda carbon-dioxide-gas supply-amount adjusting valve that adjusts an amount of carbon dioxide gas supplied to the denitrification tank. 5. The apparatus for treating a radioactive nitrate waste liquid according to claim 1, whereina carbon source supplied to the denitrification tank is acetic acid, andthe apparatus further includes:a pH sensor that measures pH of the denitrified liquid; anda carbon-source supply-amount adjusting valve that adjusts an amount of a carbon source supplied to the denitrification tank. 6. The apparatus for treating a radioactive nitrate waste liquid according to claim 3, whereina carbon source supplied to the denitrification tank is one of or both of organic acid and sweetener, andair is temporarily supplied to the gas circulating line via an air-supply-amount adjusting valve. 7. The apparatus for treating a radioactive nitrate waste liquid according to claim 6, wherein the denitrification tank includes an oxidation-reduction potential meter that measures an oxidation-reduction potential of the denitrified liquid. 8. The apparatus for treating a radioactive nitrate waste liquid according to claim 1, comprising an adjusting tank at an upstream of the denitrification tank, whereinthe adjusting tank includes:an electrical conductivity meter that measures a level of electric conductivity;an industrial-water introducing line; andan industrial-water supply-amount adjusting valve that is interposed through the industrial-water introducing line and adjusts an amount of water supplied based on a measurement value of the electrical conductivity meter. 9. The apparatus for treating a radioactive nitrate waste liquid according to claim 1, wherein the first solid-liquid separating unit and the second solid-liquid separating unit are solid-liquid separating films. 10. An apparatus for treating a radioactive nitrate waste liquid, comprising:a denitrification tank that accommodates active sludge which adsorbs or takes in a radioactive substance in a nitrate waste liquid containing nitrate and the radioactive substance and in which an anaerobic microorganism that reduces the nitrate to nitrogen gas grows; anda reaeration tank that aerates and mixes a denitrification-treated liquid treated in the denitrification tank with active sludge in which the aerobic microorganism grows, whereinthe denitrification tank includes:a pH adjusting unit that supplies a pH adjuster used for adjusting pH of the nitrate waste liquid;a carbon-source supplying unit that supplies a carbon source to the denitrification tank;a weir that prevents flowing-out sludge from leaking out into the denitrification tank, andthe reaeration tank includes:a second solid-liquid separating unit that further separates the denitrification-treated liquid treated with the active sludge into a sludge-containing solid content and a treated liquid; andan air supplying unit that is arranged on a lower side of the second solid-liquid separating unit and supplies air into the reaeration tank. 11. A method for treating a radioactive nitrate waste liquid, comprising:in a denitrification tank that accommodates active sludge that adsorbs or takes in a radioactive substance in a nitrate waste liquid containing nitrate and the radioactive substances and in which an anaerobic microorganism that reduces the nitrate to nitrogen gas grows, a step at which an active sludge treatment is performed by supplying a carbon source while adjusting pH of the nitrate waste liquid, and at a time of separating a denitrified liquid treated with the active sludge by using a first solid-liquid separating unit into a sludge-containing solid content and a denitrification-treated liquid, gas not containing oxygen is supplied thereby to accelerate a process for reducing an anaerobic microorganism and cleanse the active sludge adhered to the solid-liquid separating unit with the gas; andin a reaeration tank that aerates and mixes the denitrification-treated liquid treated in the denitrification tank with the active sludge, a step of further separating the denitrification-treated liquid treated with the active sludge into a sludge-containing solid content and a reaeration-treated liquid by using a second solid-liquid separating unit.