Application of the activated sludge model for nitrogen to elevated nitrogen conditions

Area of Science:

• Environmental Engineering
• Microbial Ecology
• Wastewater Treatment

Background:

• Industrial wastewater often contains high chemical oxygen demand (COD) and nitrogen.
• Ammonia-oxidizing bacteria can be inhibited, complicating biological nitrogen removal.
• Accurate modeling is crucial for optimizing wastewater treatment processes.

Purpose of the Study:

• To evaluate the Activated Sludge Model for Nitrogen (ASMN) under various conditions.
• To define the nitrification operating window and characterize denitrification performance.
• To develop guidelines for enhanced biological nitrogen removal.

Main Methods:

• Simulations of steady-state and dynamic conditions using industrial wastewater data.
• Varied simulation parameters including temperature, solids retention time, dissolved oxygen, pH, and salt concentration.
• Performed sensitivity analyses on model parameters and process variables.

Main Results:

• pH and temperature were identified as critical variables for nitrification, especially under upset conditions.
• Lower pH values facilitated better nitrification at higher temperatures for high-nitrogen wastewater.
• Nitric oxide and nitrous oxide emissions were elevated, linked to electron donor depletion in anoxic reactors.

Conclusions:

• The ASMN model accurately reflects the influence of key variables on nitrogen removal.
• Findings align with the known growth characteristics of nitrifying and denitrifying bacteria.
• Guidelines for improved biological nitrogen removal were established based on simulation outcomes.