Achieving high-rate partial nitritation with aerobic granular sludge at low temperatures

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Background:

• Partial nitritation is crucial for mainstream anammox processes in wastewater treatment.
• Nitrite-oxidizing bacteria (NOB) are difficult to outcompete under mainstream conditions, limiting partial nitritation efficiency.
• Low temperatures pose additional challenges for biological nutrient removal processes.

Purpose of the Study:

• To develop a high-rate partial nitritation process for low-ammonium wastewater at low temperatures.
• To investigate the effectiveness of seeding aerobic granules for improved partial nitritation.
• To understand the mechanisms of NOB repression and process performance under challenging conditions.

Main Methods:

• Utilized aerobic granules as seed material for partial nitritation.
• Operated the system at low temperatures (10-15 °C) with progressively shortened hydraulic retention times.
• Monitored nitrogen loading rates, ammonium oxidation rates, and microbial community structure.

Main Results:

• Aerobic granules facilitated a stratified nitrifier structure and maintained sufficient residual ammonium, effectively repressing NOB.
• Achieved high nitrogen loading rates (6.8 ± 0.4 kg N m⁻³ d⁻¹) at low temperatures (10-15 °C).
• Granular sludge exhibited high concentration and activity, providing overcapacity to counteract temperature effects; anammox bacteria were also detected.

Conclusions:

• Aerobic granules show significant potential for achieving high-rate partial nitritation under mainstream conditions, even at low temperatures.
• The developed process demonstrates robustness and efficiency, contributing to the advancement of anammox-based wastewater treatment.
• The findings provide valuable insights into low-temperature partial nitrification, though further studies are needed for real domestic wastewater applications.