Low-temperature sewage denitrification treatment system and method

The invention discloses a low-temperature sewage denitrification treatment system which comprises a hydrolysis denitrification tank and an aerobic nitrification tank, a sewage outlet of the hydrolysis denitrification tank is communicated with a sewage inlet of the aerobic nitrification tank through a water outlet pipe, and a sewage outlet of the aerobic nitrification tank is communicated with a sewage inlet of the hydrolysis denitrification tank through a return pipe; the pretreated sewage and the sewage flowing back from the backflow pipe enter the hydrolysis denitrification tank through the sewage inlet, and organic solid particles in the sewage are subjected to hydrolysis acidification reaction by using hydrolysis acidification bacteria in the hydrolysis denitrification tank; volatile fatty acid is generated, and organic nitrogen substances in the sewage are subjected to an ammoniation reaction to generate ammonia nitrogen; denitrifying bacteria in the hydrolysis denitrification tank and the generated vola