This calculation performs the characterization of raw wastewater based on the STOWA methodology, widely used in biological wastewater treatment modeling (such as ASM models).
From global parameters like total COD and Total Kjeldahl Nitrogen (TKN), the method estimates the distribution of key wastewater components, splitting them into:
This decomposition is essential for process simulations, enabling accurate representation of wastewater behavior in biological reactors.
Mathematically, the process consists of a partitioning of COD and total nitrogen into different fractions:
| Parameter | Default units | Default value | Description |
|---|---|---|---|
| Total COD | mg/L | — | Total chemical oxygen demand of the wastewater |
| Total Kjeldahl nitrogen (TKN) | mg/L | — | Total organic and ammonia nitrogen concentration |
| Dissolved oxygen (SO) | mg/L | — | Dissolved oxygen concentration in the wastewater |
| Alkalinity (SALK) | mg/L | — | Buffering capacity of the medium |
| Soluble inert COD fraction (fSI) | — | 0.075 | Fraction of COD as soluble inert organic matter |
| Readily biodegradable COD fraction (fSS) | — | 0.2 | Fraction of COD as readily biodegradable substrate |
| Particulate inert COD fraction (fXI) | — | 0.175 | Fraction of COD as particulate inert organic matter |
| Heterotrophic biomass COD fraction (fXBH) | — | 0.05 | Fraction of COD as active heterotrophic biomass |
| Autotrophic biomass COD fraction (fXBA) | — | 0 | Fraction of COD as autotrophic biomass |
| Endogenous decay products fraction (fXP) | — | 0 | Fraction of COD as endogenous decay products |
| Ammonium nitrogen fraction of TKN (fSNH) | — | 0.7 | Fraction of TKN as ammonia nitrogen |
| Soluble biodegradable organic N fraction (fSND) | — | 0.1 | Fraction of TKN as soluble biodegradable organic nitrogen |
| Parameter | Default units | Description |
|---|---|---|
| Soluble inert organic matter (SI) | mg/L | Non-biodegradable soluble fraction |
| Readily biodegradable substrate (SS) | mg/L | Fraction readily consumed by microorganisms |
| Particulate inert organic matter (XI) | mg/L | Non-biodegradable particulate fraction |
| Active heterotrophs (XBH) | mg/L | Active heterotrophic biomass |
| Autotrophs (XBA) | mg/L | Autotrophic (nitrifying) biomass |
| Particulates from biomass decay (XP) | mg/L | Residues from biomass decay |
| Slowly biodegradable substrate (XS) | mg/L | Fraction requiring hydrolysis before consumption |
| Ammonia nitrogen (SNH) | mg/L | Nitrogen in ammonia form |
| Soluble biodegradable organic nitrogen (SND) | mg/L | Soluble organic nitrogen fraction |
| Particulate biodegradable organic nitrogen (XND) | mg/L | Particulate organic nitrogen fraction |
| Nitrate and nitrite (SNO) | mg/L | Oxidized nitrogen compounds |
| Alkalinity (SALK) | mg/L | Resulting alkalinity |
| Dissolved oxygen (SO) | mg/L | Resulting dissolved oxygen |