Method for improving autotrophic nitrogen removal contribution of polyculture type mainstream anaerobic ammonia oxidation granular sludge process

The invention discloses a method for improving autotrophic nitrogen removal contribution of a polyculture type mainstream anaerobic ammonia oxidation granular sludge process, which comprises the following steps: 1) carrying out carbon control pretreatment on urban sewage, regulating and controlling the content of dissolved organic matters in the sewage and the ratio of the dissolved organic matters to total nitrogen, and improving the carbon source quality of the sewage; (2) carrying out oxygen-limited aeration treatment on part of sewage subjected to carbon control pretreatment, mixing the part of sewage with sewage which is not subjected to aeration treatment to optimize the nitrogen composition of the sewage, and then pumping the sewage into an up-flow anaerobic ammonia oxidation reactor; and 3) limiting the heterotrophic denitrifying bacteria mediated nitrite nitrogen reduction activity in the up-flow anaerobic ammonia oxidation granular sludge reactor through directional sludge discharge based on micro-s