NOVELTY - The nitrogen-containing wastewater is denitrified by the activity of autotrophic denitrifying microorganisms in primary autotrophy-type denitrification process (A) during which ammonia nitrogen is made an electron donor and nitrite nitrogen is made an electron acceptor. The treated water of process (A) is subjected to secondary autotrophy-type denitrification process (B) during which hydrogen gas is made electron donor. The treated water from the process (B) is circulated to process (A). Thus, nitrogen-containing waste water is processed.    USE - For processing wastewater containing nitrogen.    ADVANTAGE - The method enables efficient and easy removal of nitrate nitrogen and nitrite nitrogen remained in the denitrified treated water by autotrophic denitrifying microorganisms. The processing of nitrogen-containing wastewater provides treated water of high quality. The nitrogen-containing wastewater processing apparatus is simple and compact in structure.    DETAILED DESCRIPTION - The nitrogen-containing wastewater is denitrified by the activity of autotrophic denitrifying microorganisms in primary autotrophy-type denitrification process (A) during which ammonia nitrogen is made an electron donor and nitrite nitrogen is made an electron acceptor. The treated water of process (A) is subjected to secondary autotrophy-type denitrification process (B) during which hydrogen gas is made electron donor, and nitrite nitrogen and/or nitrate nitrogen is made electron acceptor. The treated water from the process (B) is circulated to process (A). Thus, nitrogen-containing waste water is processed.    An INDEPENDENT CLAIM is included for nitrogen-containing wastewater processing apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows the systematic diagram of processing apparatus of nitrogen-containing wastewater. (Drawing includes non-English language text)    Autotrophic denitrifying microorganisms reaction tank (1)    Membrane element (10)    Piping (13)    Circulation tank (20)    Denitrifying processing unit (24)