Question

The concentration of dissolved Oxygen in water for growth of fish should be more than 𝑋 ppm and Biochemical Oxygen Demand in clean water should be less than 𝑌 ppm. X and Y in ppm are, respectively.

• A. X Y
  4  8
• B. X Y
  6  5
• C. X Y
  4  15
• D. X Y
  6  12

Answer 1

The Correct Option is B

The dissolved oxygen (DO) in water is an essential parameter for the survival of aquatic organisms. Fish and other aquatic species depend on adequate oxygen levels to carry out cellular respiration and maintain metabolic processes. In general:
- For healthy growth and reproduction of fish, the dissolved oxygen concentration must be above 6 ppm.
- Levels below 4 ppm can cause stress, and prolonged exposure to such conditions may be lethal to most fish species.
On the other hand, biochemical oxygen demand (BOD) measures the oxygen consumed by microorganisms while decomposing organic matter in the water. It serves as an indirect indicator of the level of organic pollution:
- For clean water, BOD values should remain below 5 ppm.
- Higher BOD levels indicate the presence of excess organic matter, leading to oxygen depletion, which adversely affects aquatic life.
Why X = 6 ppm and Y = 5 ppm?
1. Dissolved oxygen levels above 6 ppm ensure a favorable environment for fish, supporting their growth, activity, and reproduction.
2. A BOD below 5 ppm reflects clean water, indicating minimal pollution and sufficient oxygen for aquatic organisms.
Thus, the correct values for X and Y are 6 ppm and 5 ppm, respectively.