Carbon and nitrogen metabolic characteristics in biological aeration filter
曝气生物滤池中碳和氮代谢特性

Carbon and nitrogen metabolic characteristics were studyed in biological aeration filter (BAF) reactor filled with expanded clay. After the start up operation of 20 d, the effluent ammonium nitrogen below 0.05 mg/L, COD concentration below 25 mg/L, nitrite nitrogen 4.7 mg/L and nitrate nitrogen 7.1 mg/L were obtained with the influent ammonium nitrogen concentration about 52 mg/L, COD concentration about 100 mg/L and inner recycle ratio 200% in BAF reactor. The removal rates of COD, ammonium nitrogen and total nitrogen were up to 75%, 99.9% and 78%, respectively. Bigger or smaller inner recycle ratio was unsuitable for running of BAF reactor. This technique can be applied to treat urban wastewater and industrial wastewater with low COD and high ammonium concentrations.