Rapid Achievement of Nitrogen Removal via Nitrite and Nitrifying Communities Transfer by Process Optimization

In order to optimize the population structure of nitrifying bacteria, several factors were analyzed in this paper to make partial nitrification start up. Lab-scale SBR was employed to treat the domestic wastewater of low COD/TN ratio. Steady partial nitrification can be achieved through real-time control in 32 cycles with dissolved oxygen (DO) 1.8plusmn0.1 mg/L and SRT 7 days at 30degC. The nitrite accumulation rate (NO₂ ^-- N /NO_x ^-- N) was over 90% under the premise of TN removal ratio above 95%. In the next 64 days, the system was also successfully operated at ambient temperature (20 ~ 24degC). Fluorescent in-situ hybridization (FISH) analysis showed that the population of ammonia oxidizing bacteria (AOB) increased by 58.9% while nitrite oxidizing bacteria(NOB) decreased by 83.2% during 32 cycles. NOB can be gradually washed out by the process control of DO and aerobic duration based on DO and pH on-line sensors so steady partial nitrification and nitrogen removal efficiency can be achieved and enhanced, respectively.