Biochemical Oxygen Demand (BOD) (BOD measures oxygen required by aerobic microbes to oxidize biodegradable organic matter)
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BOD measures oxygen required by aerobic microbes to oxidize biodegradable organic matter in water — reported as mg O2 per litre (standard 5-day, 20 °C is commonly cited).
What each symbol means
| Symbol | What it stands for |
|---|---|
| BOD | Biochemical oxygen demand (mg O2 / L typical reporting) |
| Dissolved O2 | O2 available in water — drops when pollution is high |
| Organic load | Biodegradable organics that consume dissolved O2 |
When to use this
Operational definition depends on incubation protocol; JEE focuses on concept: higher biodegradable organics → higher BOD → more polluted water.