Method and apparatus for treating nitrate waste liquid

A method for treating a nitrate waste liquid performing a treatment for reducing a nitrate waste liquid by using active sludge which adsorbs or takes in a radioactive substance in the nitrate waste liquid containing nitric acid and the radioactive substance and in which an anaerobic microorganism that reduces the nitric acid to nitrogen gas grows, the method comprising:

• a first separation treatment step at which an active sludge treatment is performed by supplying a first carbon source in which the anaerobic microorganism can easily multiply and a second carbon source in which the anaerobic microorganism cannot easily multiply, while adjusting pH of the nitrate waste liquid in a denitrification tank that accommodates the nitrate waste liquid, and at a time of separating a denitrified liquid treated with the active sludge by providing a first solid-liquid separating unit that separates the denitrified liquid into a sludge-containing solid content and a denitrification-treated liquid, gas not containing oxygen is supplied thereby to accelerate a treatment for reducing anaerobic microorganism and cleanse active sludge adhered to the first solid-liquid separating unit with gas;
• and
• a second separation treatment step of further separating the denitrification-treated liquid treated at the first separation treatment step in a reaeration tank that accommodates the denitrification-treated liquid treated at the first separation treatment step and aerates and mixes the liquid with active sludge by providing a second solid-liquid separating unit that separates the liquid into a sludge-containing solid content and a reaeration-treated liquid.