Engineering aspects and practical application of autotrophic nitrogen removal from nitrogen rich streams

摘要

The anaerobicammoniumoxidation (Anammox) process, discovered 20 years ago, is, in combination withpartial 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. Theconventional 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 canbe controlled in such a way that the partial nitritation step produces an Anammox-suited influent. TheAnammox reactor conditions should favour the growth of the Anammox organisms in view of their lowgrowth rate and possible inhibition effects. Dissolved oxygen and nitrite concentrations should be keptas low as possible and biomass washout should be limited. If the partial nitritation process and the Anammoxprocessare 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 aerobicand anaerobic ammonium oxidizers.An overview is presented of the practical implementation of autotrophic nitrogen removal. The processcan be accomplished in the same reactor (1-reactor system) or by using 2 separate reactors (2-reactorsystem). Typically the 1-reactor system is a biofilm or granular reactor where the ammonium oxidizersare active in the outer layers of the biofilm or granule, producing a suitable amount of nitrite for theAnammox organisms that are active in the inner layers. Transport of ammonium and the produced nitriteis governed by diffusion. Finally, the different nitrogen removal processes are compared in terms ofoperational conditions and a direction for future work is provided.