The treatment of wastewater containing ammonia nitrogen is one of the emphases on the sustainable development of fertilizer industry.The biological denitrogenation technology is widely applied in practice because of its low cost and no secondary pollution.The fundamentals of the biological denitrogenation technology are analyzed.The traditional biological denitrogenation processes such as A/O and SBR,and the new type biological denitrogenation processes such as short cut nitrification and denitrification,si...