Assessment of partial nitrification reactor performance through microbial population shift using quinone profile,...

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Partial nitrification to nitrite is crucial for efficient biological nitrogen removal in engineered systems.
• Controlling operating parameters is key to accumulating ammonia-oxidizing bacteria (AOB).

Purpose of the Study:

• To investigate the effects of pH, dissolved oxygen (DO), and temperature on AOB accumulation.
• To optimize conditions for partial nitrification suitable for Anammox reactors.

Main Methods:

• Operated reactors at varying pH, DO, and temperature.
• Assessed microbial population shifts using quinone profiling, Scanning Electron Microscopy (SEM), and Fluorescence In Situ Hybridization (FISH).

Main Results:

• Optimal conditions (pH 8, DO 0.3-0.5 mg/l, 35°C) achieved a nitrite-to-ammonium nitrogen ratio (NO2N:NH4N) of 0.9-1.5.
• UQ-8, a key AOB quinone, increased from 24.8% to 61.2% over 136 days.
• FISH confirmed AOB outcompeted other bacteria, becoming dominant.
• SEM revealed a shift in aerobic granular sludge morphology towards spherical and small rod-shaped clusters.

Conclusions:

• Specific operating parameters significantly enhance AOB accumulation for effective partial nitrification.
• The optimized process provides a suitable substrate for Anammox reactors, improving nitrogen removal efficiency.
• Microbial community analysis confirmed the dominance of AOB under optimal conditions.