The link between nitrous oxide emissions, microbial community profile and function from three full-scale WWTPs.

Area of Science:

• Environmental Microbiology
• Wastewater Engineering
• Biogeochemical Cycles

Background:

• Nitrous oxide (N₂O) is a potent greenhouse gas with significant emissions from wastewater treatment plants (WWTPs).
• Limited understanding exists on the microbial drivers of N₂O emissions in full-scale WWTPs.
• Seasonal variations and operational events can influence N₂O production.

Purpose of the Study:

• To investigate the relationship between microbial community structure and function and N₂O emissions in WWTPs.
• To identify key microbial taxa and genes associated with N₂O production.
• To explore the impact of operational parameters and seasonal changes on N₂O emissions.

Main Methods:

• High-throughput sequencing and reverse transcriptase quantitative PCR (RT-qPCR) were used on activated sludge samples.
• Wastewater characteristics, N₂O emissions, and microbial community data were collected over two seasons.
• Correlation analyses were performed to link microbial data with N₂O emission factors.

Main Results:

• N₂O emissions varied significantly (0.001–0.280% of influent NH₄-N).
• Abundances of Nitrotoga, Candidatus Microthrix, and Rhodobacter genera correlated with N₂O emissions, favored by high dissolved oxygen (DO) and nitrate (NO₃^-).
• NirK gene expression was linked to N₂O emissions, with peaks associated with aeration transitions.

Conclusions:

• Aeration optimization is crucial for mitigating N₂O emissions during operational events.
• Monitoring specific microbial genera and gene expression (nirK, nosZ clade II) is vital for controlling N₂O production.
• Understanding microbial ecology is key to reducing greenhouse gas footprints of WWTPs.