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Question #46572
The Question
In a municipal sewage treatment plant, the secondary aeration tank operates essentially as a large-scale continuous stirred-tank bioreactor. If the impeller design is inadequate to handle the high viscosity of the heavy activated sludge, significantly reducing the oxygen transfer rate, which of the following will be the most direct biological consequence on the discharged effluent and the receiving water body?
Options
- A.
The effluent will exhibit a drastically reduced Biochemical Oxygen Demand (BOD) due to the premature settling of microbial flocs.
- B.
Chemoautotrophic bacteria will fail to completely oxidize ammonia, resulting in a nutrient-rich effluent that accelerates eutrophication.
- C.
Methanogenic bacteria will rapidly dominate the aeration tank, leading to high-yield biogas production prior to the sludge digester stage.
- D.
The primary sludge will fail to undergo anaerobic decomposition, directly increasing the biomagnification of heavy metals in the river.
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
Aerobic Tank|Stirred-Tank Bioreactor|Oxygen Transfer
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question integrates Biotechnology (bioreactor geometry and oxygen transfer mechanics) with Microbes in Human Welfare (sewage treatment).
Students often memorize that 'secondary treatment reduces BOD' without connecting the mechanical requirement of aeration to the specific metabolic needs of nitrifying bacteria.
The primary trap (Option C) plays on the assumption that low oxygen immediately leads to biogas production, failing to distinguish the specific spatial separation of aerobic tanks and anaerobic sludge digesters in NCERT.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Microbes in Human Welfare - Class 12 |
| Concept | Primary vs Secondary Sewage Treatment |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |