NOVELTY - The processing apparatus of nitrogen component-containing water has aerobic tank (4) for nitrifying nitrogen component, supply pipe (8) for supplying water, anaerobic tank (3) for denitrifying nitrified component, circuit (5) for returning water, and oxygen circulation portion. Tanks (3,4) are closed in airtight condition, and oxygen circulation portion is provided between tanks. The oxygen circulation portion has oxygen enrichment device (9) for separating oxygen in anaerobic tank and supplying oxygen into interface upper direction of water in aerobic tank.    USE - For processing water containing nitrogen component, such as organic nitrogen and ammonium compound.    ADVANTAGE - The processing apparatus efficiently enables processing of nitrogen component-containing water.    DETAILED DESCRIPTION - The processing apparatus of nitrogen component-containing water carries out biological treatment of nitrogen component-containing water. The processing apparatus has aerobic tank (4) for nitrifying nitrogen component with nitrifying bacteria, a supply pipe (8) for supplying nitrogen component-containing water, connected with upstream of aerobic tank through a flow path (20), an anaerobic tank (3) for denitrifying nitrified nitrogen component with denitrifying bacteria, a circuit (5) for returning water in aerobic tank to anaerobic tank, and an oxygen circulation portion. The aerobic tank and anaerobic tank are closed in airtight condition, and oxygen circulation portion is provided between aerobic tank and anaerobic tank. The oxygen circulation portion has oxygen enrichment device (9) for separating oxygen in anaerobic tank and supplying oxygen into interface upper direction of water in aerobic tank.    DESCRIPTION OF DRAWING(S) - The figure shows the processing apparatus of nitrogen component-containing water. (Drawing includes non-English language text)    Anaerobic tank (3)    Aerobic tank (4)    Circuit (5)    Supply pipe (8)    Oxygen enrichment device (9)    Flow path (20)