ASM2d-GHG/N₂O

Python package for ASM2d-GHG/N₂O dynamic process modelling.

Overview

The same compiled model can be used through three PyPI package names:

pip install asm2dn2o
pip install asm2dghg
pip install asm2dg

The main package is asm2dn2o. The packages asm2dghg and asm2dg are aliases to asm2dn2o and expose the same compiled four models:

  • asm2d_n2o = asm2d_ghg = asm2d_g : ASM2d-GHG/N₂O biochemical reactor

  • clarifiers : primary and secondary clarifier separation

  • combiner : flow-weighted two-stream mixer

  • delay : hydraulic delay

from asm2dn2o import asm2d_n2o, clarifiers, combiner, delay
from asm2dghg import asm2d_ghg, clarifiers, combiner, delay
from asm2dg import asm2d_g, clarifiers, combiner, delay

The model extends the IWA ASM framework for biological carbon, nitrogen, and phosphorus removal with explicit nitrous oxide pathway representation and gas-transfer calculations. At reactor level, it resolves C, N, P, and S transformations while tracking dissolved and off-gas N₂O dynamics.

N₂O pathways

The current ASM2d-N₂O implementation distinguishes three biological N₂O production pathways:

  1. NN pathway Nitrifier nitrification by AOB, linked to hydroxylamine oxidation.

  2. ND pathway Nitrifier denitrification by AOB, driven by nitrite / free nitrous acid and strongly influenced by low-DO conditions.

  3. DEN pathway Heterotrophic denitrification, where N₂O appears as an intermediate in the reduction chain:

    \[NO_3^- \rightarrow NO_2^- \rightarrow NO \rightarrow N_2O \rightarrow N_2\]

This pathways separation is central to the model because it allows the user to interpret whether N₂O are dominated by heterotrophic denitrification, AOB-related nitrifier denitrification, or nitrifier nitrification contributions.

A more detailed equation-level description is provided on the dedicated N₂O Pathways and Gas Transfer page.

Why this package is useful

The package is designed as a compact modelling kernel rather than a full end-user application. It gives the user the compiled building blocks needed to:

  • assemble dynamic ASM2d-GHG/N₂O reactor simulations in Python,

  • build plant-specific municipal anaerobic/anoxic/oxic (A2/O) or other layouts; including primary and secondary clarifiers, hydraulic combiner and delay, etc.,

  • test control logics on aeration, RAS, WAS, etc.

  • analyse DO, NH₄, NO₂, NO₃, and N₂O dynamics,

  • connect biological production with gas stripping and off-gas behaviour.

For authors acknowledgement, see: Acknowledgement.

For citation, license and contact information, see: Citation, License and Contact.

User Guide