What does oxygen demand describe in water pollution?

What does oxygen demand describe in water pollution?

• A. The amount of oxygen dissolved in water by photosynthesis.
• B. The oxygen required by microbes to decompose organic waste, reducing dissolved oxygen.
• C. The oxygen produced by fish.
• D. Oxygen dissolved in rainwater.

Answer: (B)

Oxygen demand refers to the amount of oxygen that microorganisms need to break down organic waste in water. When organic pollution is present, these microbes respire and consume dissolved oxygen, lowering the oxygen available for other aquatic life. This potential for oxygen depletion is often captured by a measurement like biochemical oxygen demand, which indicates how much oxygen would be used if the water were left for a set period. The other ideas describe oxygen that is produced or dissolved by different processes (like photosynthesis or rainwater) rather than the oxygen that microbes require to decompose matter, so they don’t describe oxygen demand.

Oxygen demand refers to the amount of oxygen that microorganisms need to break down organic waste in water. When organic pollution is present, these microbes respire and consume dissolved oxygen, lowering the oxygen available for other aquatic life. This potential for oxygen depletion is often captured by a measurement like biochemical oxygen demand, which indicates how much oxygen would be used if the water were left for a set period. The other ideas describe oxygen that is produced or dissolved by different processes (like photosynthesis or rainwater) rather than the oxygen that microbes require to decompose matter, so they don’t describe oxygen demand.