Long-Term Nitrogen Removal Performance and Microbial Analysis in a SNAD-Based MBBR at Room Temperature

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• The simultaneous partial nitrification, anammox, and denitrification (SNAD) process offers energy and sludge reduction benefits for wastewater treatment.
• Real domestic sewage treatment at ambient temperatures presents unique challenges for nitrogen removal processes.

Purpose of the Study:

• To evaluate the long-term performance and microbial mechanisms of a single-stage moving bed biofilm reactor (MBBR) using the SNAD process.
• To determine the impact of dissolved oxygen (DO) and C/N ratio on nitrogen removal efficiency in the SNAD-MBBR system.
• To identify key microbial communities driving nitrogen conversion in the reactor.

Main Methods:

• A single-stage moving bed biofilm reactor (MBBR) was operated for long-term treatment of real domestic sewage.
• A pre-carbon adsorption unit adjusted the influent C/N ratio.
• Dissolved oxygen (DO) levels and C/N ratios were monitored and controlled.
• Microbial community analysis was performed using molecular techniques.

Main Results:

• Stable SNAD operation achieved 65% total nitrogen (TN) removal at DO ~0.3 mg/L.
• Elevated C/N ratios (4.71:1) decreased TN removal by approximately 30%.
• Key microbial players identified: *Candidatus Brocadia* (anammox), *Nitrospirae* (AOB), and *Denitratisoma* (denitrifiers).

Conclusions:

• The SNAD-MBBR process is feasible for treating real domestic sewage under ambient conditions.
• Optimizing DO and C/N ratio is crucial for microbial synergy and stable nitrogen removal.
• The study provides insights into microbial mechanisms governing nitrogen conversion in SNAD systems.