Ammonium (NH4+), nitrite (NO2-), and nitrate (NO3-) are three most common forms of nutrient nitrogen (N) which are important environmental contaminants contributing to eutrophication, depletion of dissolved oxygen (DO) in surface water, toxicity to a wide range of organisms, and reduction of chlorine disinfection efficiency. One of the main responsibilities in wastewater treatment plants (WWTPs) is to remove (old school) or recover (preferred today) the nutrient (Nitrogen and Phosphorus) from the "waste"water. Anaerobic ammonium oxidation (Anammox), first discovered in 1995, is considered as a promising alternative technology to conventional one (nitrification/denitrification) due to the advantages of no requirements for oxygen and exogenous organic carbon addition, low sludge production, and decrease in greenhouse gas (GHG) emission. Therefore, Anammox research is becoming an attracting global topic in both research and industrial fields.
