A/O pilot-scale nitrogen removal process treating domestic wastewater Ⅰ . The study of short-cut nitrification and denitrification
A/O生物脱氮工艺处理生活污水中试（一）短程硝化反硝化的研究

The effect of main factors, such as pH, MLSS, FA, T, SRT, DO and HRT, on short-cut nitrification and denitrification was systematically analyzed in a pilot-scale A/O nitrogen removal plant treating domestic wastewater. The experimental results demonstrated that DO is the main factor to achieve short-cut nitrification in the study. Fish analysis presented that a long-term operation at low DO (0.3~0.7 mg?L-1) concentration lead to the elimination of ammonia oxidizing bacteria (AOB), so as to realize nitrite accumulation. The average nitrite accumulation ratio could reach 85%; sometimes the nitrite accumulation ratio was higher than 95%. The short-cut nitrification and denitrification was damaged with the nitrite accumulation ratio decreasing from 85% to 10% when DO was increased above 1.5 mg?L-1. The nitrite accumulation ratio was resumed to 75% after about two sludge ages with the DO kept in low level. The SVI increased with the increase of nitrite accumulation ratio in the initial period, but the SVI maintained at a proper level of 80~120 mL?g-1 in the after time no matter how high or low the nitrite accumulation ratio was.