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Question #46584
The Question
During secondary sewage treatment, a toxic influx destroys the aerobic microbial flocs in the aeration tank, leaving the effluent with an exceptionally high Biochemical Oxygen Demand (BOD). If this unprocessed effluent is directly pumped into the anaerobic sludge digester and inoculated with Methanobacterium, efficient biogas production fails. Which of the following best explains this failure?
Options
- A.
Methanogens require the high dissolved oxygen levels typically associated with high BOD to initiate the breakdown of complex organic matter.
- B.
The absence of activated sludge prevents the formation of primary sludge, which serves as the exclusive substrate for methanogenesis.
- C.
Methanogens are strict anaerobes that cannot directly metabolize complex organic polymers and require an O2-depleted environment with simpler fermented intermediates.
- D.
High BOD indicates a low concentration of organic matter, thereby depriving the methanogens of the necessary carbon source for biogas production.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Methanobacterium|Activated_Sludge|BOD|Biogas
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often harbor the misconception that methanogens directly consume raw sewage to produce biogas.
This question tests the understanding of obligate microbial succession in sewage treatment: aerobic depletion of O2 and breakdown of complex organics must precede anaerobic fermentation, which in turn provides the specific substrates (like H2 and CO2) required for methanogenesis.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Microbes in Human Welfare - Class 12 |
| Concept | Methanogens Metabolism |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |