Biokinetic Models API Reference

Overview

ErgoPlanner supports advanced biokinetic models for mechanistic simulation of biological wastewater treatment processes. This includes Activated Sludge Models (ASM1, ASM2d, ASM3) and Anaerobic Digestion Model No. 1 (ADM1).

Note: Biokinetic model implementation is currently in development. This documentation will be updated as model interfaces are finalized.

Planned Model Support

Activated Sludge Models

ASM1 (Activated Sludge Model No. 1)

• Purpose: Carbon oxidation, nitrification, denitrification
• State Variables: 13 components including soluble/particulate COD fractions, nitrogen species, biomass
• Processes: Aerobic/anoxic heterotrophic growth, autotrophic nitrification, decay, hydrolysis

ASM2d (Activated Sludge Model No. 2d)

• Purpose: Extended biological phosphorus removal (EBPR)
• State Variables: 19 components including phosphorus-accumulating organisms (PAO)
• Processes: Biological P-removal, chemical P-precipitation, storage polymers

ASM3 (Activated Sludge Model No. 3)

• Purpose: Storage polymer-based carbon removal
• State Variables: Includes storage products, endogenous respiration
• Processes: Storage of substrate, growth on stored products

Anaerobic Digestion Models

ADM1 (Anaerobic Digestion Model No. 1)

• Purpose: Anaerobic digestion of complex organic matter
• State Variables: 24 soluble and 12 particulate components
• Processes: Hydrolysis, acidogenesis, acetogenesis, methanogenesis
• Outputs: Biogas production (CH4, CO2, H2)

Planned Interfaces

ASM1Parameters

interface ASM1Parameters {
  // Heterotrophic biomass parameters
  muH: number;           // Maximum specific growth rate (1/d)
  KS: number;            // Half-saturation coefficient for substrate (mg COD/L)
  KOH: number;           // Oxygen half-saturation for heterotrophs (mg O2/L)
  KNO: number;           // Nitrate half-saturation for denitrification (mg NO3-N/L)
  bH: number;            // Decay coefficient for heterotrophs (1/d)

  // Autotrophic biomass parameters
  muA: number;           // Maximum specific growth rate for autotrophs (1/d)
  KNH: number;           // Ammonia half-saturation for autotrophs (mg NH4-N/L)
  KOA: number;           // Oxygen half-saturation for autotrophs (mg O2/L)
  bA: number;            // Decay coefficient for autotrophs (1/d)

  // Stoichiometric parameters
  YH: number;            // Yield for heterotrophic biomass (mg COD/mg COD)
  YA: number;            // Yield for autotrophic biomass (mg COD/mg N)
  fp: number;            // Fraction of biomass to particulate products
  iXB: number;           // N content of biomass (mg N/mg COD)
  iXP: number;           // N content of products (mg N/mg COD)

  // Hydrolysis parameters
  kh: number;            // Maximum specific hydrolysis rate (1/d)
  KX: number;            // Half-saturation coefficient for hydrolysis (mg COD/mg COD)

  // Correction factors
  tempCorrection: {
    theta: number;       // Temperature correction factor (-)
    referenceTemp: number; // Reference temperature (°C)
  };
}

ASM2dParameters

interface ASM2dParameters extends ASM1Parameters {
  // PAO-specific parameters
  muPAO: number;         // Maximum specific growth rate for PAO (1/d)
  qPHA: number;          // Rate constant for storage of PHA (1/d)
  qPP: number;           // Rate constant for storage of poly-P (1/d)
  KP: number;            // Half-saturation for phosphorus (mg P/L)
  KPHA: number;          // Half-saturation for PHA (mg COD/L)
  bPAO: number;          // Decay coefficient for PAO (1/d)

  // Stoichiometric coefficients for EBPR
  YPAO: number;          // Yield for PAO (mg COD/mg COD)
  iPAO: number;          // P content of PAO (mg P/mg COD)

  // Chemical precipitation
  kPRE: number;          // Precipitation rate constant (m³/mg/d)
  kRED: number;          // Redissolution rate constant (m³/mg/d)
}

ADM1Parameters

interface ADM1Parameters {
  // Hydrolysis parameters
  kHyd_ch: number;       // Hydrolysis rate for carbohydrates (1/d)
  kHyd_pr: number;       // Hydrolysis rate for proteins (1/d)
  kHyd_li: number;       // Hydrolysis rate for lipids (1/d)

  // Acidogenesis parameters
  km_su: number;         // Maximum uptake rate for sugars (1/d)
  km_aa: number;         // Maximum uptake rate for amino acids (1/d)
  km_fa: number;         // Maximum uptake rate for fatty acids (1/d)

  // Acetogenesis parameters
  km_c4: number;         // Maximum uptake rate for valerate/butyrate (1/d)
  km_pro: number;        // Maximum uptake rate for propionate (1/d)

  // Methanogenesis parameters
  km_ac: number;         // Maximum uptake rate for acetate (1/d)
  km_h2: number;         // Maximum uptake rate for hydrogen (1/d)

  // Yield coefficients
  Y_su: number;          // Yield for sugar degraders (kg COD/kg COD)
  Y_aa: number;          // Yield for amino acid degraders
  Y_fa: number;          // Yield for fatty acid degraders
  Y_c4: number;          // Yield for valerate/butyrate degraders
  Y_pro: number;         // Yield for propionate degraders
  Y_ac: number;          // Yield for acetate degraders
  Y_h2: number;          // Yield for hydrogen degraders

  // Decay rates
  kdec_X: number;        // Decay rate for biomass (1/d)

  // Inhibition parameters
  KI_h2_fa: number;      // Inhibition constant for H2 on fatty acids
  KI_h2_c4: number;      // Inhibition constant for H2 on valerate/butyrate
  KI_h2_pro: number;     // Inhibition constant for H2 on propionate
  KI_nh3: number;        // Inhibition constant for ammonia

  // Gas transfer
  kLa: number;           // Gas-liquid transfer coefficient (1/d)
  pGas_h2o: number;      // Partial pressure of water vapor (bar)

  // Temperature correction
  tempCorrection: {
    theta: number;       // Temperature correction factor
    referenceTemp: number; // Reference temperature (°C)
  };
}

State Variables

ASM1 State Variables

interface ASM1State {
  // Soluble components (mg/L)
  S_I: number;           // Inert soluble COD
  S_S: number;           // Readily biodegradable substrate COD
  S_O: number;           // Dissolved oxygen
  S_NO: number;          // Nitrate and nitrite nitrogen
  S_NH: number;          // Ammonia nitrogen
  S_ND: number;          // Soluble biodegradable organic nitrogen
  S_ALK: number;         // Alkalinity (mol HCO3/m³)

  // Particulate components (mg/L)
  X_I: number;           // Inert particulate COD
  X_S: number;           // Slowly biodegradable substrate COD
  X_BH: number;          // Active heterotrophic biomass
  X_BA: number;          // Active autotrophic biomass
  X_P: number;           // Particulate products from biomass decay
  X_ND: number;          // Particulate biodegradable organic nitrogen
}

ADM1 State Variables

interface ADM1State {
  // Soluble components (kg COD/m³)
  S_su: number;          // Monosaccharides
  S_aa: number;          // Amino acids
  S_fa: number;          // Long chain fatty acids
  S_va: number;          // Valerate
  S_bu: number;          // Butyrate
  S_pro: number;         // Propionate
  S_ac: number;          // Acetate
  S_h2: number;          // Hydrogen gas
  S_ch4: number;         // Methane gas

  // Inorganic components
  S_IC: number;          // Inorganic carbon (kmol C/m³)
  S_IN: number;          // Inorganic nitrogen (kmol N/m³)
  S_I: number;           // Soluble inerts (kg COD/m³)

  // Particulate components (kg COD/m³)
  X_c: number;           // Composites
  X_ch: number;          // Carbohydrates
  X_pr: number;          // Proteins
  X_li: number;          // Lipids
  X_su: number;          // Sugar degraders
  X_aa: number;          // Amino acid degraders
  X_fa: number;          // Fatty acid degraders
  X_c4: number;          // Valerate/butyrate degraders
  X_pro: number;         // Propionate degraders
  X_ac: number;          // Acetate degraders
  X_h2: number;          // Hydrogen degraders
  X_I: number;           // Particulate inerts

  // Gas phase (bar)
  p_h2: number;          // Hydrogen partial pressure
  p_ch4: number;         // Methane partial pressure
  p_co2: number;         // Carbon dioxide partial pressure
}

COD Fractionation

COD Components

Wastewater COD fractionation for ASM models:

interface CODFractionation {
  // Total COD
  totalCOD: number;      // Total COD (mg/L)

  // Soluble fractions
  S_I: number;           // Inert soluble COD (mg/L)
  S_S: number;           // Readily biodegradable COD (mg/L)

  // Particulate fractions
  X_I: number;           // Inert particulate COD (mg/L)
  X_S: number;           // Slowly biodegradable COD (mg/L)

  // Calculated fractions (0-1)
  f_SI: number;          // Fraction of soluble inert
  f_SS: number;          // Fraction of readily biodegradable
  f_XI: number;          // Fraction of particulate inert
  f_XS: number;          // Fraction of slowly biodegradable
}

Nitrogen Speciation

interface NitrogenSpeciation {
  // Total nitrogen
  totalN: number;        // Total nitrogen (mg N/L)

  // Inorganic nitrogen
  NH4_N: number;         // Ammonia nitrogen (mg N/L)
  NO2_N: number;         // Nitrite nitrogen (mg N/L)
  NO3_N: number;         // Nitrate nitrogen (mg N/L)

  // Organic nitrogen
  TKN: number;           // Total Kjeldahl nitrogen (mg N/L)
  S_ND: number;          // Soluble biodegradable organic N (mg N/L)
  X_ND: number;          // Particulate biodegradable organic N (mg N/L)
  organicN_inert: number; // Inert organic nitrogen (mg N/L)
}

Phosphorus Speciation

interface PhosphorusSpeciation {
  // Total phosphorus
  totalP: number;        // Total phosphorus (mg P/L)

  // Inorganic phosphorus
  PO4_P: number;         // Orthophosphate (mg P/L)
  polyP: number;         // Polyphosphate (mg P/L)

  // Organic phosphorus
  organicP: number;      // Organic phosphorus (mg P/L)

  // In biomass
  biomassP: number;      // Phosphorus in biomass (mg P/L)
}

Model Execution

Planned BiokineticsEngine Interface

interface BiokineticsEngine {
  /**
   * Execute one timestep of biokinetic model
   */
  step(
    state: ASM1State | ASM2dState | ASM3State | ADM1State,
    parameters: ModelParameters,
    dt: number,
    temperature: number,
    volume: number
  ): {
    newState: ModelState;
    rates: ProcessRates;
    outputs: ModelOutputs;
  };

  /**
   * Calculate steady-state solution
   */
  steadyState(
    influent: ModelState,
    parameters: ModelParameters,
    operatingConditions: OperatingConditions
  ): ModelState;

  /**
   * Validate parameters
   */
  validateParameters(parameters: ModelParameters): {
    valid: boolean;
    warnings: string[];
    errors: string[];
  };
}

Implementation Status

Current Status: Biokinetic model interfaces are in the design phase.

Planned Implementation:

1. ASM1 for basic nitrification/denitrification modeling
2. ASM2d for biological phosphorus removal
3. ADM1 for anaerobic digestion and biogas production
4. Model parameter libraries for typical wastewater types
5. Temperature correction functions
6. Steady-state and dynamic solvers

Future Documentation

This section will be expanded to include:

• Complete parameter definitions for each model
• Default parameter sets for municipal wastewater
• Influent characterization methods
• Stoichiometry matrices
• Process rate equations
• Solver configuration
• Model calibration guidelines
• Typical operating ranges

Related Documentation

• Process Units API - Process unit types that use biokinetic models
• Simulation Engine API - Calculation mode selection
• Mass Balance API - COD and nutrient fractionation

References

1. Henze, M., et al. (2000). Activated Sludge Models ASM1, ASM2, ASM2d and ASM3. IWA Publishing.
2. Batstone, D.J., et al. (2002). The IWA Anaerobic Digestion Model No 1 (ADM1). Water Science and Technology, 45(10), 65-73.
3. Rieger, L., et al. (2012). Guidelines for Using Activated Sludge Models. IWA Publishing.