Application of Anaerobic Ammonium Oxidation in Mainstream Municipal Wastewater Treatment

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Nitritation combined with anaerobic ammonium oxidation (anammox) has been widely applied in treatment of high nitrogenous wastewaters since its discovery in the 1990s. This process is more cost efficient than conventional treatment technologies and has been studied intensively for municipal reject water or centrate treatment. Due to the slow growth rate of the involved microorganisms systems with high biomass retention such as biofilm reactors or granular based sequencing batch reactors (SBRs) are often employed. The current applications of nitritation-anammox processes are confined to wastewaters with ammonium concentrations of > 500 mg-N l-1 and temperatures around 30 °C. Complete nitrogen removal without the need for organic carbon and in addition less energy consumption is, however, also highly interesting for mainstream municipal wastewater treatment. The main goal of this project is thus to realize the application of nitritation-anammox at low temperature/low substrate conditions with two different reactor types, SBR (suspended sludge system) and MBBR (biofilm reactor system). The key questions are the stabilization of the anammox reaction under these conditions on the one side and the minimization of unwanted nitrite oxidation on the other side. Stepwise reduction of ammonium loading and temperature will be used to acclimate the biomass to the desired condition. Oxygen limitation strategies and pH control will be applied as main regulatory instruments to sustain an optimal biomass composition and limit aerobic nitrite oxidation.