In wastewater treatment plants with high ammonium concentration, nitrogen compounds would significantly reduce by activated sludge system with separate treatments: nitrification and denitrification. Over the past few years, new technologies for nitrogen removal have been developed to change to the traditional wastewater treatment technologies because it was consistent with nature of waste water and reducing technology costs. Newly discovered pathways are the anaerobic oxidation of ammonium (ANAMMOX). Ammonium is converted to nitrogen gas under anoxic conditions with nitrite as the electron acceptor. Compared to conventional nitrification and denitrification, the aeration and carbon-source demand is reduced by over 50 and 100 percent, respectively. Anaerobic ammonia oxidizing (Anammox) biomass was enriched from sludge collected in Hanoi's areas such as food processing Phu Do villages, sewage sludge of pig slaughtering area in Binh Da and septic tank of TOSERCO hotel. After 54 days anammox activity started to be detected, by the simultaneous consumption of ammonium and nitrite in the sludge enrichment system, this particularity stable from day 97 onwards. In anaerobic conditions, ammonia can be lost only in the presence of nitrite. Anammox activity was further confirmed by the formation of hydrazine-are intermediate products of anaerobic ammonium oxidation with nitrite as electron acceptor. After a stable anammox activity, the color of biomass of the 3 samples changed nom black to dark brown. The results of the activity tests is the ability to remove 10 mg N-NH4/l.day and 5 mg N-NO2/l.day in 250 ml glass bottles with 30 ml of sediment sludge (equivalent to 2.6g/l dry sludge).
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