Anaerobic ammonium oxidation (anammox) has been discovered in 1990's from one of the side-stream treatment systems. Unlike conventional biological nitrogen removal processes involving complete ammonia oxidation followed by chemoorganoheterotrophic denitrification, anammox involves autotrophic conversion of a partially nitrified stream containing nearly equimolar mixtures of ammonia and nitrite to dinitrogen gas.
Anammox process is an attractive sustainable nitrogen control solution as no external carbon is required and can reduce energy costs by 60% while removing nitrogen from the liquid stream (i.e., the transformation of inorganic nitrogen species to dinitrogen gas). Additionally, a 90% less biomass yield can be achieved by anammox processes. Thus, this process is an energy and cost-effective alternative for conventional nitrogen removal.