To remove nitrogen compounds in wastewater treatment process, the traditional technologies are often applied nitrification - denitrification. This method will not be suitable for treatment of wastewater with low C/N concentration, such as industrial waste water because of COD supplying requirement. Therefore, new technologies for nitrogen compounds removal have been detected and developed to change to the traditional wastewater treatment technologies because it was consistent with nature of waste water and reducing technology costs. This is an anaerobic ammonium oxidation (ANAMMOX), this process with the participation of the anammox bacteria oxidize ammonia using nitrite as electron acceptor and producing atmospheric dinitrogen. After discovering the ANAMMOX process from enriched sludge samples (Phu Do village, sewage sludge of pig slaughtering area in Binh Da and manholes of TOSERCO hotel - Hanoi). The research on the characterization of anammox biomass was carried out. Anammox bacteria were detected by sequence of 16S rRNA genes amplified by PCR using universal primers designed for anammox bacteria. The suitable conditions for anammox activity are pH from 7 to 8 and temperature from 30 to 42°C. Anammox activity was completely inhibited when the nitrite concentration or = 100 mg N/L.