NOVELTY - Method for performing denitrification treatment process, involves fermenting sludge under anaerobic condition to generate fatty acid using anaerobic sludge-fixed film bioreactor, providing carbon source to the product, subjecting the product to denitrification process, and discharging the rest of active sludge from bottom of aerobic tank to maintain the whole biological process under the high sludge concentration.    USE - The method is useful for performing denitrification treatment process.    ADVANTAGE - The method is environmentally-friendly and simple, has high efficiency, and emission rate.    DETAILED DESCRIPTION - Method for performing denitrification treatment process, involves fermenting sludge under anaerobic condition to generate fatty acid using anaerobic sludge-fixed film bioreactor, providing carbon source to the product, subjecting the product to denitrification process, discharging the rest of active sludge from bottom of aerobic tank to maintain the whole biological process under the high sludge concentration, where total hydraulic power staying time is 6.5-10 hours, time for anaerobic fermenting process is 1.5-3.0 hours, time for denitrification process is 5-7 hours, the denitrification system is carried out for 80-120 days, the reacting time of nitrifying bacteria with sludge is 15-20 days and film subassembly flux is 18-22 liters. The anaerobic sludge-fixed film bioreactor comprises deep anaerobic tank (1), anoxic tank (2), and aerobic tank (3). The anaerobic sludge layer (11) is arranged at the lower portion of the deep anaerobic tank. The anaerobic supernatant (10) is formed at the upper portion. The anoxic tank (2) is internally provided with a stirring mixing device (4). The anoxic tank (3) is internally provided with an aeration oxygen filling device (5) and a film subassembly (6). The film subassembly (6) is connected with the water outlet through a film water outlet pump (9) and the pipeline. The bottom is provided with a rest active sludge discharge opening (12). The aerobic tank (3) is connected with the anoxic tank (2) through a first reflow pump (7) and a pipeline, and connected with the deep anaerobic tank (1) through a second reflow pump (8) and the pipeline. The original sewage enters the bioreactor from the bottom of the deep anaerobic tank (1) and passes through a section of anaerobic sludge layer (11) with the help of the anaerobic microorganism. The carbon source in the sewage is fully hydrolyzed and acidized and converted to volatile organic acid. The anaerobic supernatant (10) is enriched with high quality carbon source which enters the anoxic tank. The sewage is treated with efficient denitrification with the help of the heterotrophic bacteria. The sludge liquid enters the aerobic tank. The mixed liquid with nitrate and nitrite generated by the nitrification of the high concentration autotrophic microbe reflows to the anoxic tank to provide the electron receptor for the denitrification. The active sludge in the aerobic tank partly reflows to the bottom of the deep anaerobic tank to perform the anaerobic fermentation treatment for the sludge.    DESCRIPTION OF DRAWING(S) - The drawing shows schematic view of anaerobic sludge-fixed film bioreactor.    Anaerobic tank (1)    Anoxic tank (2)    Aerobic tank (3)    Mixing device (4)    Filling device (5)    Film subassembly (6)    First reflow pump (7)    Second reflow pump (8)    Anaerobic supernatant (10)    Anaerobic sludge layer (11)    Anaerobic supernatant (12)