High-rate nitrogen removal by the Anammox process with a sufficient inorganic carbon source

This study focused on high-rate nitrogen removal by the anaerobic ammonium oxidation (Anammox) process with a sufficient inorganic carbon (IC) source. Experiments were carried out in an up-flow column Anammox reactor fed with synthetic inorganic wastewater for 110 days. The IC source was added into the influent tank in the form of bicarbonate. The results confirmed the positive impact of inorganic matter on stimulating Anammox activity. After the addition of sufficient IC, the nitrogen removal rate sharply increased from 5.2 to 11.8 kg-N m−3 day−1 within only 32 days. NO2-N inhibition was not observed even at NO2-N concentrations greater than 460 mg N/L, indicating the enriched Anammox consortium adapted to high NO2-N concentrations. The ratio of NO2-N removal, NO3-N production and NH4-N removal for the reactor was correspondingly changed from 1.21:0.21:1 to 1.24:0.18:1. Simultaneously, the sludge volume index of the Anammox granules decreased markedly from 36.8 to 21.5 mL/g, which was attributed to the implementation of proper operational strategy. In addition, DNA analysis revealed that a shift from the KSU-1 strain to the KU2 strain occurred in the Anammox community.