[Short-cut Nitrification Recovery and Its Transformation into CANON Process in a Biofilm Reactor]

A short-cut nitrification process with modified polyethylene as carrier was operated to investigate the biofilm short-cut nitrification recovery using synthetic inorganic ammonia-rich wastewater as influent at 30℃ ±1℃. The short-cut nitrification was destroyed first by excessive aeration, and it was not built in 83 days under the condition of continuous aeration with DO less than 0.5 mg·L^-1 and free ammonia (FA) more than 1.5 mg·L^-1, which are very beneficial to short-cut nitrification. However,short-cut nitrification was realized by changing continuous aeration to intermittent aeration on 84^th day, and it was proved again on 142^nd day. After that, biofilm system provided a living environment for ANAMMOX bacteria, anaerobic ammonia oxidation occurred, and the biofilm short-cut nitrification process was gradually transformed into CANON process. As the load of influent and aeration increased, the total nitrogen removal efficiency and removal load increased, and the total nitrogen removal load could reach up to 2.52 kg·(m³·d)^-1. Finally, in the 3rd stage, ΔNO₃^--N/ΔTN was 0.10 on average, which means stabe short-cut nitrification in the CANON process. Therefore, once NOB was adapted to FA, it would be not very easy to recover short-cut nitrification, while intermittent aeration was an effective way, and the nitriation process would be finally transformed into CANON process, which would further improve the short-cut nitrification stability.