A/O pilot-scale nitrogen removal process treating domestic wastewater Ⅱ. The study of system characteristics and SND
A/O生物脱氮工艺处理生活污水中试(二)系统性能和SND现象的研究

The COD, ammonia and total nitrogen (TN) removal efficiency were studied in the paper at low DO concentration in a pilot-scale A/O nitrogen removal plant treating domestic wastewater. The experimental results showed that the COD and ammonia removal efficiency reach 85% and 92%, respectively. Because of the low influent COD/TN ratio (2.93), the average TN removal efficiency was only 64%, while TN removal efficiency could be increased by 12% with the nitrite accumulation ratio increased from 15% to 85%. A good correlation of ammonia removal efficiency, nitrification rate and TN removal efficiency was found. Simultaneous nitrification and denitrification (SND) with nitrite at low DO level could be realized, which contributed to 5%~12% TN nitrogen removal based on nitrogen mass balance. The SND would be damaged with the DO increased, and the mechanism of SND with nitrite was presented.