When a 2% sewage sample is incubated for 5 days at 20°C with an observed dissolved oxygen drop of 8 mg/l, what is the sewage BOD_________________?
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Answer: D. 400 mg/l
Explanation
Dilution factor represents the reciprocal of the sewage sample volume fraction used in the test bottle. Multiplying the measured dissolved oxygen depletion by the calculated dilution factor yields the total biochemical oxygen demand. Fifty multiplied by eight milligrams per liter calculates precisely to four hundred milligrams per liter. Biochemical oxygen demand measures the amount of dissolved oxygen consumed by microorganisms during organic decomposition. Standard BOD tests incubate diluted wastewater samples in sealed bottles at twenty degrees Celsius for five days. Dilution ensures that sufficient dissolved oxygen remains available throughout the multi-day incubation period.
Environmental engineers use BOD values to determine organic pollution loading in municipal wastewater treatment plants. Regulatory agencies enforce effluent discharge limits based on biochemical oxygen demand to protect aquatic ecosystems. Wastewater treatment facility designs depend on accurate BOD measurements to size biological aeration basins. Option A underestimates the pollutant concentration by failing to apply the correct volumetric dilution factor. Option B represents a lower dilution calculation error common in standard wastewater laboratory exercises. Option C underestimates the true oxygen demand by using incorrect arithmetic multipliers during evaluation.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
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