High Dissolved Oxygen Selection against Nitrospira Sublineage I in Full-Scale Activated Sludge

Area of Science:

• Environmental microbiology
• Wastewater treatment technologies
• Biogeochemical cycles

Background:

• Ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) are key players in wastewater nitrification.
• Oxygen availability is a critical factor influencing the population dynamics of AOB and NOB.
• Previous understanding suggested NOB require higher oxygen levels than AOB.

Purpose of the Study:

• To investigate the oxygen affinity of a specific Nitrospira sublineage I OTU.
• To determine the impact of dissolved oxygen (DO) levels on NOB and AOB populations in wastewater treatment.
• To understand how oxygen affects microbial community structure and function in nitritation.

Main Methods:

• Comparative analysis of oxygen affinity constants between Nitrospira and AOB.
• Long-term laboratory-scale reactor experiments manipulating DO concentrations.
• Microscopic observation of AOB and NOB microcolony morphology under varying DO conditions.

Main Results:

• A specific Nitrospira sublineage I OTU exhibited lower oxygen affinity than cohabitating AOB.
• Low DO conditions selected for this NOB, while high aeration inhibited it.
• NOB microcolonies showed a low surface area-to-volume ratio, while AOB maintained a porous morphology, reflecting their oxygen affinities.

Conclusions:

• The oxygen affinity of dominant microbial taxa dictates their response to DO levels.
• Species-specific oxygen affinities are crucial for understanding AOB/NOB population dynamics.
• Operating strategies for partial nitritation must consider these specific oxygen requirements for effective process control.