Denitratation (NO 3 NO 2 )anammox is a promising method for anammox application in mainstream wastewater treatment plants (WWTPs) to reduce oxygen and organic matter consumption. Achieving nitrite production via denitratation and controlling denitritation (NO 2 N 2 ) is the basis of the denitratationanammox process. To control denitritation, the denitrifying biocommunity and growth rate are critically reviewed for biocommunity optimization. Then, the shortterm and longterm effects of pH on denitritation were summarized and the possible mechanism was discussed, along with the effect of CN ratio and organic matter type on denitritation. Meanwhile, the strategies for producing nitrite via controlling denitritation are discussed, as well as the processes for achieving nitrogen removal via denitratationanammox in WWTPs. Finally, the practical application of denitratationanammox in a fullscale mainstream WWTP is documented.