N₂O emission during wastewater nitrification with enriched nitrifying bacteria

Abstract

Nitrifying bacteria were enriched in a sequencing batch reactor and used to quantify N₂O emission specifically by wastewater nitrification while minimizing or preventing the chances of denitrification during the experiment. Batch wastewater nitrification was carried out in a reactor (working volume 0.5 L) at different aeration rates (10 and 20 mL/min) and -N concentrations (25, 50, and 100 mg/L). Wastewater nitrification efficiencies were more than 97% in all the cases except at 100 mg/L with 10 mL/min aeration rate (92%). Cumulative N₂O emission reached 0.2, 1.15, and 2.67 mg (aeration: 10 mL/min) and 0.37, 2.18, and 3.08 mg (aeration: 20 mL/min) at the initial -N concentration of 25, 50, and 100 mg/L, respectively. N₂O emission yields (kg N₂O-N per kg processed -N) were 0.016–0.058 and 0.029–0.088 at 10 and 20 mL/min aeration rate, respectively. The yields were higher than that of denitrification. The results showed that cumulative N₂O emission and the yield increased at higher ammonium concentration and aeration rate. Accumulated nitrite during nitrification also contributed and played a pivotal role in N₂O emission.

Keywords:

• Enriched nitrifiers
• N₂O emission
• Nitrification
• Nitrite

Acknowledgments

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by Ministry of Education, Science and Technology (Grant no. 2010-0004497). This research was also supported by a Hallym University Research Fund, 2014 (HRF 201401-011) and by Korea Ministry of Environment as “Global Top Project” (Project No. GT-11-B-02-008-2).