The invention relates to an urban 
sewage treatment device and method for quick realization of partial 
nitrification based on free 
nitrous acid inhibition and belongs to the field of 
sewage treatment. The method comprises the steps that an FNA 
treatment unit is arranged in parallel in the 
sludge backflow process of a traditional A2 / O technology secondary 
sedimentation tank, the growth activity of 
nitrite oxidizing 
bacteria (NOB) is partially inhibited by using the selective bacterium inhibiting effect of FNA on 
ammonia oxidizing 
bacteria (AOB) and NOB under the anoxic condition, 
sludge then flows back to a main flow A2 / O reactor, NOB in active 
sludge are gradually elutriated under the effect of sludge age control, and thus partial 
nitrification of the urban 
sewage is quickly achieved in the main flow A2 / O reactor. The method is simple, heating or real-
time control is not needed, and a good 
sedimentation effect is achieved; in addition, 
phosphate removal and 
nitrogen removal are carried out simultaneously, the 
phosphate removal effect is not affected by addition of the FNA 
treatment unit, the efficient and simultaneous 
phosphate removal and 
nitrogen removal effect of the low-
carbon source urban sewage is achieved, and the urban 
sewage treatment device and method for quick realization of partial 
nitrification based on free 
nitrous acid inhibition are suitable for upgrading transformation of existing urban sewage plants.