Engineering aspects and practical application of autotrophic nitrogen removal from nitrogen rich streams
Van Hulle, Stijn W.H. × Vandeweyer, Helge J.P. Meesschaert, Boudewijn Vanrolleghem, Peter A. Dejans, Pascal Dumoulin, Ann #
Chemical Engineering Journal vol:162 pages:1-20
The anaerobicammoniumoxidation (Anammox) process, discovered 20 years ago, is, in combination with
partial nitritation, ideally suited to treat nitrogen rich waste water streams such as digester effluent.
In this review the engineering aspects and the practical application of the process are reviewed. The
conventional nitrification–denitrification and nitritation–denitritation are also discussed briefly.
The environmental conditions affecting the nitrification process, free ammonia and nitrous acid concentration,
temperature, pH and dissolved oxygen concentration, are discussed. These conditions can
be controlled in such a way that the partial nitritation step produces an Anammox-suited influent. The
Anammox reactor conditions should favour the growth of the Anammox organisms in view of their low
growth rate and possible inhibition effects. Dissolved oxygen and nitrite concentrations should be kept
as low as possible and biomass washout should be limited. If the partial nitritation process and the Anammoxprocess
are occuring in the same reactor, care should be taken to the dissolved oxygen concentration,
the ammonium load and the nitrite concentration to obtain a sustainable co-existence between aerobic
and anaerobic ammonium oxidizers.
An overview is presented of the practical implementation of autotrophic nitrogen removal. The process
can be accomplished in the same reactor (1-reactor system) or by using 2 separate reactors (2-reactor
system). Typically the 1-reactor system is a biofilm or granular reactor where the ammonium oxidizers
are active in the outer layers of the biofilm or granule, producing a suitable amount of nitrite for the
Anammox organisms that are active in the inner layers. Transport of ammonium and the produced nitrite
is governed by diffusion. Finally, the different nitrogen removal processes are compared in terms of
operational conditions and a direction for future work is provided.