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Question #45938
The Question
During the secondary treatment of sewage, activated sludge is pumped into large tanks called anaerobic sludge digesters. Which of the following statements regarding the metabolic and ecological dynamics within these digesters is INCORRECT?
Options
- A.
Anaerobic bacteria digest the aerobic flocs, initiating a sequence of hydrolysis and fermentation that produces organic acids.
- B.
Methanogens act upon the fermentative end-products to generate a biogas mixture primarily containing CH4, H2S, and CO2.
- C.
Since fermentation releases less than 7% of the substrate's energy, the unextracted energy is entirely dissipated as metabolic heat, making the sludge digestion process energetically wasteful.
- D.
The limitation of complete oxidation in this anaerobic environment is strategically utilized to convert waste biomass into a combustible energy source.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Comparative_Analysis
Sharpen your ability to evaluate multiple scenarios and distinguish between competing potential answers.
Concepts Behind This Question
Methanogens|Facultative_Anaerobes|BOD
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often conflate 'low ATP yield for the microbe' with 'low energy retention in the system'.
They memorize that fermentation is 'inefficient' (<7% energy released) but fail to realize that the 'unreleased' energy remains in the chemical bonds of the byproducts.
In sewage treatment, this metabolic 'inefficiency' is the exact mechanism that makes biogas a valuable, energy-rich fuel.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Respiration in Plants - Class 11 |
| Concept | Fermentation Limitations |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |