Bio-augmentation by nitrification with return sludge

Area of Science:

• Environmental Engineering
• Microbial Ecology

Background:

• Activated sludge processes often struggle with nitrification at suboptimal conditions, such as low temperatures or high loads.
• Bio-augmentation offers a strategy to bolster the nitrifying microbial community within these systems.

Purpose of the Study:

• To evaluate the effectiveness of bio-augmentation using a nitrification reactor in the sludge return line for enhancing nitrification in highly loaded activated sludge systems.
• To compare the impact of internal (reject water) versus external (artificial) ammonium sources for bio-augmentation.

Main Methods:

• Development and application of a mathematical model based on the Activated Sludge Model 1 (ASM1).
• Simulation of a high-load wastewater treatment plant in The Netherlands, incorporating a side-stream bio-augmentation process (BABE).
• Evaluation of different ammonium sources for feeding the bio-augmentation reactor.

Main Results:

• Bio-augmentation enables nitrification in highly loaded activated sludge systems, even at low winter temperatures.
• The most significant improvement was observed at approximately 50% of the minimal solid retention time (SRT) without augmentation.
• Utilizing an internal ammonia source (reject water) proved more effective than an external artificial ammonium source.

Conclusions:

• Process-internal bio-augmentation is a viable strategy to improve nitrification efficiency in challenging activated sludge systems.
• The findings provide a quantitative basis for designing bio-augmentation processes to enhance nitrogen removal capacity.
• Internal ammonia sources are recommended for more effective bio-augmentation in these systems.