NOVELTY - Denitrifation device comprises water tank (1), AAO reactor (2), sediment pool (3), middle water tank, BAF reactor (5) and sequencing batch reactor (6). Water tank has inflow pump. AAO reactor is connected to anaerobic area which is connected to anoxic area. Volume ratio of AAO reactor, anoxic area and aerobic area is 3:5:1. Aerobic area is connected to sediment pool which is connected to water tank by another inflow pump. Sediment pool is connected to sludge pump, and has outlet at its bottom. Sludge pump is connected to sediment storage tank.    USE - Denitrification device used for removing phosphorus and nitrogen from sludge mixture (all claimed).    ADVANTAGE - The denitrification device is cheap, and reduces excess production.    DETAILED DESCRIPTION - Denitrifation device comprises water tank, AAO reactor, sediment pool, middle water tank, BAF reactor and sequencing batch reactor. Water tank has inflow pump. AAO reactor is connected to anaerobic area which is connected to anoxic area. Volume ratio of AAO reactor, anoxic area and aerobic area is 3:5:1. Aerobic area is connected to sediment pool which is connected to water tank by another inflow pump. Sediment pool is connected to sludge pump, and has outlet at its bottom. Sludge pump is connected to sediment storage tank. Sequencing batch reactor transfers lye through another sludge pump. Aerobic area has aeration head and sump pump. BAF reactor has 40-50% filler. Sequencing batch reactor has stirrer, pH meter and temperature control device. An INDEPENDENT CLAIM is included for a method for performing denitrification, which involves:    (A) adding sludge mixture to water tank under stirring condition;    (B) maintaining chemical oxygen demand at 280-320 mg/L;    (C) transferring obtained mixture to sedimentation tank by sludge pump;    (D) transferring obtained material to aeration zone;    (E) recycling obtained material to stirrer;    (F) keeping recycled material under anaerobic conditions for 1.5-2 hours;    (G) transferring obtained mixture to anoxic zone;    (H) processing obtained mixture in BAF reactor under stirring condition;    (I) treating obtained mixture in aerobic zone to obtain material having dissolved oxygen content of 2-3 mg/L;    (J) separating liquid and solid content of obtained material in sedimentation tank;    (K) transferring supernatant to intermediate tank, and then to BAF reactor;    (L) treating supernatant with denitrifying bacteria in the form of fixed-film biological growth on active filler;    (M) providing oxygen by aeration pump;    (N) transferring certain amount of obtained material back to AAO reactor, and remaining amount to sludge storage tank;    (O) adding sodium hydroxide (1-2 mol/L) from lye tank;    (P) maintaining temperature and pH at 20-30 degrees C and 9-10 respectively;    (Q) processing obtained sludge in mixer for 5-10 days; and    (R) discharging obtained mixture.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of denitrification device.    Water tank (1)    AAO reactor (2)    Sediment pool (3)    BAF reactor (5)    Sequencing batch reactor (6)