Modeling a bench-scale alternating aerobic/anoxic activated sludge system for nitrogen removal using a modified ASM1

Area of Science:

• Environmental Engineering
• Wastewater Treatment Technologies
• Biochemical Modeling

Background:

• The Activated Sludge Model No. 1 (ASM1) is a standard for modeling wastewater treatment processes.
• Nitrogen removal in alternating aerobic-anoxic (AAA) systems requires accurate dynamic modeling.
• Conventional ASM1 can be complex due to numerous state variables and parameters.

Purpose of the Study:

• To simplify and adapt the ASM1 for modeling nitrogen dynamics in bench-scale AAA systems.
• To improve the practical applicability of ASM1 for engineers designing and operating AAA systems.
• To assess the model's predictive capability for ammonium (NH4+) and nitrate (NO3-) removal.

Main Methods:

• Modified the original ASM1 by removing inert soluble COD (S(I)) and inert particulate COD (X(I)) state variables.
• Assumed soluble COD represents readily biodegradable COD (S(S)) and particulate COD represents slowly biodegradable COD (X(S)).
• Removed alkalinity from the model due to its stability in AAA systems; adjusted kinetic parameters.

Main Results:

• The modified ASM1 reasonably predicted NH4+ and NO3- dynamics in the AAA system.
• The model accurately predicted effluent NH4+ and NO3- concentrations.
• Model simplification did not compromise predictive performance for key nitrogen species.

Conclusions:

• The simplified ASM1 provides a practical tool for engineers managing AAA systems.
• Reduced complexity enhances usability without sacrificing accuracy in predicting nitrogen removal.
• Wastewater COD characterization is sufficient for effective application of the modified model.