Chemical Oxygen Demand (COD) (COD measures oxygen equivalent of oxidizable matter (dichromate oxidation in standard lab)
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COD measures oxygen equivalent of oxidizable matter (dichromate oxidation in standard lab framing). Usually COD ≥ BOD because COD includes non-biodegradable oxidizable species too.
What each symbol means
| Symbol | What it stands for |
|---|---|
| BOD | Biochemical oxygen demand |
| COD | Chemical oxygen demand (mg O2 equivalent / L in common reporting) |
| Oxidizable matter | Organics + some inorganic reductants counted in COD test |
When to use this
Textbook generalization: COD ≥ BOD for municipal / mixed wastes; exact numbers depend on sample.