Questions and Answers
What does BOD measure in water?
Why is dissolved oxygen concentration important in aquatic environments?
What is the accepted standard incubation period for BOD testing?
During the BOD test, when is the initial dissolved oxygen measured?
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Which of the following reagents is NOT used in the BOD testing procedure?
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How should the BOD sample bottle be filled during collection?
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What happens to the organic matter during the BOD test?
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What is one effect of high BOD levels in water bodies?
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Study Notes
Biochemical Oxygen Demand (BOD)
- BOD measures the amount of oxygen required by microorganisms to decompose organic matter in water under aerobic conditions.
- Critical for evaluating water quality and its impact on aquatic life and aesthetics.
- Understanding organic matter's effect on dissolved oxygen (DO) is essential for effective water quality management.
Principles of BOD Testing
- Conducted by incubating water samples at 20°C in darkness.
- Standard incubation period is 5 days, though variations exist.
- Initial DO is measured right after dilution; subsequent oxygen uptake during incubation contributes to BOD results.
Reagents Used in BOD Testing
- Manganous Sulfate: Traps oxygen in sample.
- Alkaline Iodide: Stabilizes the sample for testing.
- Sulfuric Acid (H2SO4): Dissolves precipitates formed in the test.
- Sodium Thiosulphate (0.0125N): Used for titration to determine oxygen consumption.
- Starch indicator: Helps visualize the endpoint of the titration.
Sample Collection Procedure
- Rinse a 13-liter bucket with the sample before collection.
- Submerge the bucket 40 cm below the water surface to fetch the sample.
- Use a corked BOD bottle, removing the cork underwater to let the sample flow in.
- Label the BOD bottle with details such as location, date, and time.
- Collect two samples: one for initial testing (before seeding) and another after seeding and incubation.
Oxygen Fixation Process
- Add Manganous Sulfate (1 ml) and Alkaline Iodide (1 ml) to the sample.
- Introduce H2SO4 (1 ml) to dissolve any precipitate.
- Shake the solution for 30 seconds, then allow it to settle.
- Measure 50 ml of the treated sample into a conical flask.
- Titrate using 0.0125N Sodium thiosulphate until a pale-yellow color is obtained.
- Add starch indicator until the solution becomes colorless, noting the titer value.
- Repeat this process for both seeded and incubated samples to compare results.
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Description
Explore the concept of Biochemical Oxygen Demand (BOD) and its significance in water quality management. This quiz covers the impact of organic matter on dissolved oxygen levels and the importance of maintaining aquatic ecosystems. Test your understanding of BOD and its role in environmental science.
