Spatial Organization of Microbiome Stability and Nitrogen Removal Resilience in a Full-Scale Plug-Flow PN/A System

Area of Science:

• Environmental microbiology
• Wastewater treatment engineering
• Biogeochemical cycling

Background:

• Partial nitritation/anammox (PN/A) is an energy-efficient nitrogen removal process crucial for wastewater treatment.
• Understanding the ecological drivers of stability and resilience in full-scale PN/A systems is critical but remains poorly characterized.
• Spatial heterogeneity and microbial community dynamics influence system performance, especially under operational disturbances.

Purpose of the Study:

• To investigate the spatial heterogeneity and recovery patterns in a full-scale plug-flow PN/A system following a dissolved oxygen (DO) shock.
• To characterize the ecological drivers, including microbial community structure and function, that govern the stability and resilience of PN/A systems.
• To identify measurable ecological indicators for strengthening PN/A operation under dynamic aeration conditions.

Main Methods:

• Integrated 13-month performance monitoring with multi-omics (metagenomics and metatranscriptomics) analyses.
• Characterized spatial variations in microbial communities and nitrogen-cycling gene expression along the reactor.
• Assessed system recovery and microbial community shifts after a controlled dissolved oxygen shock event.

Main Results:

• Stable PN/A operation achieved 84.5% total nitrogen removal, with the upstream zone contributing significantly (61.3%).
• A DO shock temporarily reduced the nitrogen removal rate, and while function recovered, microbial structure and bacterial gene copies did not fully return, indicating a decoupling.
• Higher bacterial diversity and functional redundancy correlated with faster recovery, and upstream microbiome stability best represented overall system resilience.

Conclusions:

• Upstream microbiome stability and functional redundancy are critical indicators of PN/A system resilience.
• Faster recovery is associated with greater microbial diversity and nitrogen cycling functional redundancy across zones.
• An upstream-focused control strategy is recommended to enhance PN/A system resilience against dynamic aeration disturbances.