UPSC Prelims 2023 · Question 85 of 97

UPSC Prelims 2023 question on Biofilters Aquaculture Systems

With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements:

1. Biofilters provide waste treatment by removing uneaten fish feed.
2. Biofilters convert ammonia present in fish waste to nitrate.
3. Biofilters increase phosphorus as nutrient for fish in water.

How many of the statements given above are correct?

  1. Only one
  2. Only two
  3. All three
  4. None
Show answer

Answer: B. Only two

Verdict

Only statements 1 and 2 are correct → Option (b) Only two.

Analysis

Recirculating aquaculture systems (RAS) are unique engineered ecosystems that minimize environmental perturbation by reducing nutrient pollution discharge. They are indoor, tank-based systems in which fish are grown at high density under controlled environmental conditions.

Statement by statement

Statement 1 – CORRECT: A biofilter system purify the water and remove or detoxify harmful waste products and uneaten feed. Biofilters use microorganisms, which are capable of degrading many compounds, fixed to an inorganic/organic medium to break down pollutants present.

Statement 2 – CORRECT: Ammonia is removed from an aquarium system through the use of a biofilter. The biofilter provides a substrate on which nitrifying bacteria grow. These nitrifying bacteria consume ammonia and produce nitrite, which is also toxic to fish. Other nitrifying bacteria in the biofilter consume nitrite and produce nitrate.

Statement 3 – INCORRECT: Biofilters are also used to remove phosphorus waste by-products generated by fish. Thus biofilters do NOT increase phosphorous content in aquatic systems — they remove it.

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