UPSC Prelims 2023 – Question 55

Here is Question 55, a part of our series on UPSC Prelims 2023

Q55. With reference to the role of biofilters in Recirculating Aquaculture Systems, 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 a 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  

Correct Answer: Option (b) 

• Role of Biofilters in Recirculating Aquaculture System (RAS): 

• RAS biofilters act to remove nitrogenous waste by-products generated by fish protein catabolism and oxidation processes. Hence, statement 1 is 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. Hence, statement 2 is correct. 
• The biofilter system reduces the concentration of nitrite, nitrate, phosphorus, and ammonium ions from the synthetic water. Hence, statement 3 is not correct. 

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