Partial nitrification in a continuous pre-denitrification submerged membrane bioreactor and its nitrifying bacterial activity and community dynamics

In this study, nitrogen removal by partial nitrification via nitrite was completely achieved for >40 days in a continuous submerged membrane bioreactor configured with both a pre-denitrification (10 L) and a nitrification tank (20 L). The possible aeration saving achieved with this configuration was 29% compared to that required for nitrogen removal via nitrate. Partial nitrification in the submerged membrane bioreactor was achieved by controlling the influent ammonium concentration (161 mg N/L) and the dissolved oxygen concentration in the nitrification tank (0.6 mg/L). Measurement of oxygen uptake rates during batch experiments confirmed that increasing influent ammonium concentration (161 mg N/L) decreased nitrite oxidizing activity of the biomass to almost zero. Furthermore, real-time PCR assays revealed that increasing influent ammonium concentration led to a decrease not of Nitrobacter but Nitrospira in the submerged membrane bioreactor. These results suggest that partial nitrification can be achieved by inhibiting the activity and growth of Nitrospira spp. with high ammonium concentration. (C) 2011 Elsevier B.V. All rights reserved.