The importance of the substrate ratio in the operation of the Anammox process in upflow biofilter

The influence of the substrate ratio on the nitrogen removal performance of the anaerobic ammonium oxidation (Anammox) process was evaluated using an upflow biofilter fed with different ratios of substrates. The influent substrate ratio of nitrite-to-ammonium (R-IS) was shown to be a key factor in the Anammox process, and the optimal R-IS level was 1.2. When the influent ammonium or nitrite level was relatively high, residual substrate over-consumption was observed. The free ammonia was not significantly inhibitory to the Anammox biomass at a concentration of 17 +/- 2 mg N L-1; however, a high level of residual nitrite reduced the activity of Anammox bacteria. The activity that was depressed by nitrite inhibition was revived within 5 days following the reduction of the R-IS. In this study, the Haldane, Edwards and Aiba models, which were used to simulate nitrite inhibition of the Anammox process, were workable, and the parameters for these models were determined. (C) 2012 Elsevier B.V. All rights reserved.