A benchmark simulation to verify an inhibition model on decay stage for nitrification

Area of Science:

• Environmental Microbiology
• Biochemical Engineering
• Water Treatment Technologies

Background:

• Activated Sludge Models (ASMs) are crucial for wastewater treatment but often simplify nitrification to a single step.
• A two-step nitrification model is needed for specific process configurations to accurately represent nitrite nitrogen dynamics.

Purpose of the Study:

• To develop and validate a two-step nitrification model using benchmark datasets.
• To investigate the kinetics of Ammonium Oxidising Bacteria (AOB) and Nitrite Oxidising Bacteria (NOB).
• To incorporate nitrite toxicity effects on nitrifying bacteria into the model.

Main Methods:

• Utilized Water Environment Research Foundation (WERF) benchmark datasets from chemostat reactors.
• Conducted laboratory batch experiments to assess nitrite-N toxicity on nitrifying bacteria.
• Developed a poisoning model to account for nitrite and ammonia toxicity, replacing traditional inhibition models.

Main Results:

• The developed two-step nitrification model accurately reproduced the WERF datasets under varying conditions.
• Nitrite-N was found to be toxic to Nitrite Oxidising Bacteria (NOB) at 500 mg-N/L and pH 7.3.
• The poisoning model effectively captured the observed toxicity effects on oxygen uptake rates.

Conclusions:

• A two-step nitrification model with a poisoning mechanism provides a more accurate representation of biological wastewater treatment processes.
• The model's ability to reproduce benchmark data validates its utility for design and operation.
• Understanding and modeling nitrite toxicity is essential for optimizing wastewater treatment plant performance.