[Performance of internal-loop air-lift nitrifying bioreactor]

Area of Science:

• Environmental Microbiology
• Biochemical Engineering

Context:

• Wastewater treatment often faces challenges with ammonia removal due to toxicity and eutrophication risks.
• Developing stable and efficient nitrification processes is crucial for environmental protection.

Purpose:

• To evaluate the performance of an internal-loop air-lift bioreactor for ammonia removal.
• To characterize the formation and properties of nitrifying granular activated sludge.
• To assess the anaerobic ammonia oxidation and nitrite reduction capabilities of the developed sludge.

Summary:

• The internal-loop air-lift bioreactor demonstrated robust performance with high ammonia tolerance (78.49 mmol/L), a high conversion rate (163.18 mmol/L·d), and stable operation (>94.42% ammonia removal).
• Nitrifying granular activated sludge formed within 45 days, exhibiting favorable characteristics: 0.83 mm diameter, 55.53 m/h settling velocity, and a specific ammonia removal rate of 0.95 mmol NH4(+)-N/g VS·d.
• The granular sludge also showed significant anaerobic activity, with ammonia oxidation and nitrite reduction rates of 0.23 and 0.24 mmol NH4(+)-N/g VS·d, respectively.

Impact:

• This study highlights a promising bioreactor configuration for efficient and stable ammonia removal in wastewater treatment.
• The formation of nitrifying granular sludge offers a more settleable and active biomass for enhanced biological nutrient removal.
• The observed anaerobic capabilities suggest potential for integrated nitrogen removal processes, reducing operational costs and environmental impact.