BOD/COD Ratio Calculator
Calculate the wastewater biodegradability index from BOD₅ and COD concentrations.
Enter BOD₅ and COD values measured for the
same wastewater sample.
The BOD₅/COD ratio is commonly used as a preliminary indicator of how amenable wastewater may be to biological treatment.
The BOD₅/COD ratio is commonly used as a preliminary indicator of how amenable wastewater may be to biological treatment.
5-day biochemical oxygen demand.
Chemical oxygen demand.
BOD₅ / COD Ratio
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BOD₅
COD
Indicative BOD₅/COD Interpretation
> 0.50
Readily biodegradable wastewater; biological treatment is generally favourable.
0.30–0.50
Biodegradable to moderately biodegradable; biological treatment may be feasible depending on wastewater characteristics.
< 0.30
Low biodegradability; refractory or inhibitory constituents may be significant.
BOD₅/COD Ratio: The ratio compares the five-day biochemical oxygen demand with chemical oxygen demand. A higher ratio generally indicates that a larger share of the measured oxygen-demanding load is amenable to biological degradation within the BOD test period.
Interpretation ranges shown above are commonly used engineering
screening ranges reported in wastewater-treatment literature.
They are indicative rather than regulatory limits. Treatment
selection should also consider wastewater composition, toxicity,
pH, nutrients, suspended solids, treatability studies and other
relevant characteristics.