[Half-nitrosofication of dewatering liquid of digested sludge with high ammonia]

Area of Science:

• Environmental Engineering
• Microbiology
• Wastewater Treatment

Context:

• Digested sludge dewatering liquid presents challenges for nitrogen removal.
• Achieving partial nitrification (half-nitrosation) is crucial for efficient wastewater treatment.
• A/O (Anaerobic/Oxic) processes are commonly used in wastewater treatment.

Purpose:

• To investigate the factors affecting and methods for achieving and maintaining half-nitrosation of digested sludge dewatering liquid.
• To identify optimal operational conditions for stable partial nitrification.
• To understand the role of free ammonia (FA) in maintaining half-nitrosation.

Summary:

• Half-nitrosation was achieved in 29 days under specific conditions (9-20°C, 5.4 mg/L DO, 30 d SRT, 0.64 kg/(m³·d) ammonia loading).
• Stable nitritation with 70% nitrite accumulation was maintained for 65 days when FA > 4 mg/L.
• Half-nitrosation was confirmed with an effluent ammonia to nitrite ratio of 1:1.32, and high FA was proven critical for its maintenance.

Impact:

• Demonstrates that maintaining FA > 4 mg/L in A/O reactors enables stable half-nitrosation.
• Highlights the potential for enhanced total nitrogen removal (91 mg/L) due to carbon source conservation.
• Provides a method for controlling half-nitrosation through dynamic adjustment of ammonia loading and pH at moderate/low temperatures.