Low Dissolved Oxygen Nitrifying Systems Exploit Ammonia-Oxidizing Bacteria With Unusually High Yield (2011)

Author(s): Bellucci M, Ofiteru ID, Graham DW, Head IM, Curtis TP

    Abstract: In wastewater treatment plants, nitrifying systems are usually operated with elevated levels of aeration to avoid nitrification failures. This approach contributes significantly to operational costs and the carbon footprint of such wastewater treatment processes. In this study, we tested the effect of aeration rate on nitrification by correlating ammonia oxidation rates with the structure of the ammonia oxidizing bacterial (AOB) community and AOB abundance in four parallel continuous-flow reactors operated for 43 days. Two of the reactors were supplied with a constant air flow rate of 0.1 l/min, while in the other two units the air flow rate was fixed at 4 l/min. Complete nitrification was achieved in all configurations, though the dissolved oxygen (DO) concentration was only 0.5 ± 0.3 mg/l in the low aeration units. The data suggest that efficient performance in the low DO units resulted from elevated AOB levels in the reactors and/or putative development of a mixotrophic AOB community. Denaturing gradient gel electrophoresis and cloning of AOB 16S rRNA gene fragments followed by sequencing revealed that the AOB community in the low DO systems was a subset of the community in the high DO systems. However, in both configurations the dominant species belonged to the Nitrosomonas oligotropha lineage. Overall, the results demonstrated that complete nitrification can be achieved at low aeration in lab scale reactors. If these findings could be extended to full scale plants without increasing nitrous oxide emissions, it would be possible to minimize the operational costs and greenhouse gas emissions without risk of nitrification failure.

      • Date: 01-09-2011
      • Journal: Applied and Environmental Microbiology
      • Volume: 77
      • Issue: 21
      • Pages: 7787-7796
      • Publisher: American Society for Microbiology
      • Publication type: Article
      • Bibliographic status: Published

      Professor David Graham
      Professor of Environmental Engineering

      Professor Ian Head
      Prof of Environmental Microbiology