Development of long-term stable partial nitrification and subsequent anammox process.

Area of Science:

• Environmental Engineering
• Wastewater Treatment
• Microbial Ecology

Background:

• Partial nitrification is a crucial step in advanced nitrogen removal processes.
• Optimizing conditions for stable partial nitrification is essential for efficient wastewater treatment.
• Previous studies highlight the sensitivity of partial nitrification to operational parameters.

Purpose of the Study:

• To establish and operate a stable partial nitrification reactor.
• To identify critical operational parameters for successful partial nitrification.
• To evaluate the performance of partial nitrification for subsequent anammox treatment.

Main Methods:

• Operation of a partial nitrification reactor for over 250 days.
• Monitoring of key parameters: ammonium loading rate, pH, free ammonia, and air flow rate.
• Analysis of effluent nitrite, ammonium, and nitrate concentrations.

Main Results:

• Stable partial nitrification achieved with a maximum nitrite production rate of 1.12 kg-Nm(-3)day(-1).
• Optimal conditions identified: high ammonium loading (>1.0 kg-Nm(-3)day(-1)), pH ~8.0, high free ammonia (>10mg NH(3)-NL(-1)), and controlled air flow ratio (<0.1).
• Stable effluent nitrite-to-ammonium ratio (1.20 ± 0.33) and low nitrate (<1.2 ± 1.0mg-NL(-1)) achieved, suitable for anammox.

Conclusions:

• Successful and stable partial nitrification was demonstrated under optimized conditions.
• The established partial nitrification process is effective for preparing effluent for granular-sludge anammox reactors.
• High nitrogen removal rates (up to 15.0 kg-TNm(-3)day(-1)) were achieved in the coupled system.