Startup and Stabilization of Nitrosation in an Anoxic-aerobic Continuous-flow Reactor with Granules

Matured nitrosation granules were inoculated to an anoxic-aerobic continuous-flow reactor at room temperature (17-19℃). The startup and stabilization of nitrosation with granules were studied. The results show that the nitrosation of the continuous-flow was successfully achieved with an average nitrite accumulation rate (NAR) above 95%. With the increase of the dissolved oxygen (DO) content from (3±0.2) to (4.5±0.2) mg·L-1 in the aerobic zone, the NAR remained above 95%. The effect of the hydraulic retention time (HRT) of the continuous-flow reactor was investigated. The short HRT (8.4 h) sped up the circulation of the sludge particles in the continuous-flow system such that the broken granular sludge could not be integrated in time, resulting in the deterioration of granular sludge settling and the loss of sludge granules. The performance of the system was restored with the increase of the HRT to 12.2 h and the continuous-flow system stabilized. The ammonia removal efficiency and NAR were 86.7% and 96.2% on day 166, respectively.