Abstract:The new type of autotrophic nitrogen removal reactor was designed according to the growth characteristics of nitrification and anammox microorganisms in order to achieve a better process of nitrification-anammox. The feasibility and characteristics of autotrophic nitrogen removal were investigated by inoculation of nitrification and anammox sludge in the reactor. The results show that the nitrification and anammox bacteria could be cultured in different area in a single reactor. After the running time of 104d, the nitrogen removal increased from 0.25kg/(m3×d) to 1.46kg/(m3×d) in the reactor. The nitrification liquid was circulated to the bottom of the reactor by using the off-gas in aerobic area and nitrogen gas produced in anaerobic area. The linear relationship between air flow rate (X) and recirculation flow rate (Y) was showed with Y = 2.8X - 37.1. The recycling ratio increased from 4 to 14, and it was no effect on the anaerobic environment in the reactor. It was confirmed by the ORP in the anaerobic area in the reactor, which kept relatively constant (-500mV) during the experiment. In addition, the ammonia nitrogen concentration in the influent decreased due to the recirculation liquid. It relieved the effect of the substrate on the inhibition of anammox bacteria in the reactor.