The amount of organic matter in sewage water can be estimated by

Options

A. Measuring oxygen demand
B. Weight of micro-organisms
C. Salt analysis
D. Calorimetery

Answer

To estimate the amount of organic matter in sewage water, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Concept**:
- Organic matter in sewage water primarily consists of biodegradable materials that can be decomposed by microorganisms.

2. **Identifying the Measurement Method**:
- The key method to estimate organic matter in sewage is through Biological Oxygen Demand (BOD). BOD measures the amount of oxygen required by aerobic bacteria to decompose organic matter in water.

3. **Conducting the BOD Test**:
- Collect a water sample from the sewage.
- Measure the initial dissolved oxygen (DO) level in the sample.
- Incubate the sample for a specific period (usually 5 days at 20°C).
- After incubation, measure the final DO level.

4. **Calculating BOD**:
- The BOD can be calculated using the formula:
\[ \text{BOD} = \text{Initial DO} - \text{Final DO} \]
- This value indicates the amount of organic matter present in the sewage water.

5. **Interpreting the Results**:
- A higher BOD value indicates a higher concentration of organic matter, as more oxygen is required for the decomposition process.

6. **Conclusion**:
- Therefore, the amount of organic matter in sewage water can be effectively estimated by measuring the Biological Oxygen Demand (BOD).

### Final Answer:
The amount of organic matter in sewage water can be estimated by **A, measuring oxygen demand** (specifically Biological Oxygen Demand).

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