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ASM1 Property Package

This package implements property relationships for the treatment of wastewater using an activated sludge biological reactor as provided in Henze, M. et al. (1987).

This Activated Sludge Model no.1 (ASM1) property/reaction package:
  • supports 'H2O', 'S_I', 'S_S', 'X_I', 'X_S', 'X_BH', 'X_BA', 'X_P', 'S_O', 'S_NO', 'S_NH', 'S_ND', 'X_ND', and 'S_ALK' as components
  • supports only liquid phase

Sets

Description Symbol Indices
Components j ['H2O', 'S_I', 'S_S', 'X_I', 'X_S', 'X_BH', 'X_BA', 'X_P', 'S_O', 'S_NO', 'S_NH', 'S_ND', 'X_ND', 'S_ALK']
Phases p ['Liq']

Components

Description Symbol Variable
Soluble inert organic matter, S_I SI S_I
Readily biodegradable substrate S_S SS S_S
Particulate inert organic matter, X_I XI X_I
Slowly biodegradable substrate X_S XS X_S
Active heterotrophic biomass X_B,H XB, H X_BH
Active autotrophic biomass X_B,A XB, A X_BA
Particulate products arising from biomass decay, X_P XP X_P
Oxygen, S_O SO S_O
Nitrate and nitrite nitrogen, S_NO SNO S_NO
NH4 + + NH 3 Nitrogen, S_NH SNH S_NH
Soluble biodegradable organic nitrogen, S_ND SND S_ND
Particulate biodegradable organic nitrogen, X_ND XND X_ND
Alkalinity, S_ALK SALK S_ALK

State variables

Description Symbol Variable Index Units
Total volumetric flowrate Q flow_vol None m3/s
Temperature T temperature None K
Pressure P pressure None Pa
Component mass concentrations Cj conc_mass_comp [p] kg/m3
Alkalinity in molar concentration A alkalinity [p] kmol HCO3−/m3

Stoichiometric Parameters

Description Symbol Parameter Value at 20 C Units
Yield of cell COD formed per g N consumed, Y_A YA Y_A 0.24 dimensionless
Yield of cell COD formed per g COD oxidized, Y_H YH Y_H 0.67 dimensionless
Fraction of biomass yielding particulate products, f_p fP f_p 0.08 dimensionless
Mass fraction of N per COD in biomass, i_xb iXB i_xb 0.08 dimensionless
Mass fraction of N per COD in particulates, i_xp iXP i_xp 0.06 dimensionless

Kinetic Parameters

Description Symbol Parameter Value at 20 C Units
Maximum specific growth rate for autotrophic biomass, mu_A µA mu_A 0.5 d − 1
Maximum specific growth rate for heterotrophic biomass, mu_H µH mu_H 4.0 d − 1
Half-saturation coefficient for heterotrophic biomass, K_S KS K_S 0.01 kg COD/m3
Oxygen half-saturation coefficient for heterotrophic biomass, K_O,H KO, H K_OH 0.0002 kg -COD/m3
Oxygen half-saturation coefficient for autotrophic biomass, K_O,A KO, A K_OA 0.0004 kg -COD/m3
Nitrate half-saturation coefficient for denitrifying heterotrophic biomass, K_NO KNO K_NO 0.0005 kg NO3-N/m3
Decay coefficient for heterotrophic biomass, b_H bH b_H 0.3 d − 1
Decay coefficient for autotrophic biomass, b_A bA b_A 0.05 d − 1
Correction factor for mu_H under anoxic conditions, eta_g ηg eta_g 0.8 dimensionless
Correction factor for hydrolysis under anoxic conditions, eta_h ηh eta_h 0.8 dimensionless
Maximum specific hydrolysis rate, k_h kh k_h 3.0 d − 1
Half-saturation coefficient for hydrolysis of slowly biodegradable substrate, K_X KX K_X 0.1 dimensionless
Ammonia Half-saturation coefficient for autotrophic biomass, K_NH KNH K_NH 1.0 kg NH3-N/m3
Ammonification rate, k_a ka k_a 0.00005 m3/kg COD . d

Properties

Description Symbol Variable Index Units
Fluid specific heat capacity cp cp None J/kg/K
Mass density ρ dens_mass [p] kg/m3

Process Rate Equations

Description Equation
Aerobic growth of heterotrophs $ρ_1 = µ_{H}(\frac{S_{S}}{K_{S}+S_{S}})(\frac{S_{O}}{K_{O,H}+S_{O}})X_{B,H}$
Anoxic growth of heterotrophs $ρ_2 = µ_{H}(\frac{S_{S}}{K_{S}+S_{S}})(\frac{K_{O,H}}{K_{O,H}+S_{O}})(\frac{S_{NO}}{K_{NO}+S_{NO}})η_{g}X_{B,H}$
Aerobic growth of autotrophs $ρ_3 = µ_{A}(\frac{S_{NH}}{K_{NH}+S_{NH}})(\frac{S_{O}}{K_{O,A}+S_{O}})X_{B,A}$
Decay of heterotrophs ρ4 = bHXB, H
Decay of autotrophs ρ5 = bHXB, H
Ammonification of soluble organic nitrogen ρ6 = kaSNDXB, H
Hydrolysis of entrapped organics $ρ_7 = k_{H}(\frac{X_{S}/X_{B,H}}{K_{X}+(X_{S}/X_{B,H})})[(\frac{S_{O}}{K_{O,H}+S_{O}})+η_{h}(\frac{K_{O,H}}{K_{O,H}+S_{O}})(\frac{S_{NO}}{K_{NO}+S_{NO}})]X_{B,H}$
Hydrolysis of entrapped organic nitrogen $ρ_7 = k_{H}(\frac{X_{S}/X_{B,H}}{K_{X}+(X_{S}/X_{B,H})})[(\frac{S_{O}}{K_{O,H}+S_{O}})+η_{h}(\frac{K_{O,H}}{K_{O,H}+S_{O}})(\frac{S_{NO}}{K_{NO}+S_{NO}})]X_{B,H}(X_{ND}/X_{S})$

Scaling

Scaling for the ASM1 property package has yet to be implemented.

References

[1] Henze, M., Grady, C.P.L., Gujer, W., Marais, G.v.R., Matsuo, T., "Activated Sludge Model No. 1", 1987, IAWPRC Task Group on Mathematical Modeling for Design and Operation of Biological Wastewater Treatment. https://belinra.inrae.fr/doc_num.php?explnum_id=4467

[2] Alex, J. et al. Benchmark Simulation Model no.1 (BSM1). Lund University, 2008, 5-6. https://www.iea.lth.se/publications/Reports/LTH-IEA-7229.pdf