UPSC CSE Prelims
Question 67
With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements :
- Biofilters provide waste treatment by removing uneaten fish feed.
- Biofilters convert ammonia present in fish waste to nitrate.
- Biofilters increase phosphorus as nutrient for fish in water.
How many of the statements given above are correct?
View correct answer and explanation
Correct answer: B
Correct Option: B (Only two)
Explanation: Recirculating aquaculture uses a waste-treatment train and biological nitrification; the supplied key broadly counts feed-waste treatment and ammonia conversion but not phosphorus addition.
Statement / Pair / Item-wise Analysis:
1. Correct/True - Taken broadly, biofiltration is part of the waste-treatment train handling contaminants derived from uneaten feed; solid particles are actually removed by mechanical filters.
2. Correct/True - Nitrifying bacteria in biofilters oxidize toxic ammonia through nitrite into nitrate.
3. Incorrect/False - Biofilters are designed to remove/process pollutants, not raise phosphorus nutrients in fish water.
Option-wise Analysis:
A. Incorrect-it counts 1, but items 1, 2 qualify, giving 2.
B. Correct-exactly 2 of the 3 listed items satisfy the condition.
C. Incorrect-it counts 3, but only 2 qualify; item(s) 3 do not.
D. Incorrect-it counts 0, but items 1, 2 qualify, giving 2.
Review note: Technical distinction: mechanical filters remove uneaten-feed solids; biofilters primarily treat dissolved ammonia. The broad wording behind key B is disputed; answer preserved.