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

 To determine the correct values of X and Y for the conditions given in the question, it is essential to understand the environmental chemistry principles related to dissolved oxygen (DO) and biochemical oxygen demand (BOD).

Dissolved Oxygen (DO): This is a measure of how much oxygen is dissolved in the water. For the healthy growth of fish and other aquatic life, the concentration of dissolved oxygen must be higher than a certain threshold. Generally, more than 5 ppm is considered sufficient for aquatic life sustainability, especially for fish growth and metabolism.

Biochemical Oxygen Demand (BOD): This is an index for measuring the amount of oxygen consumed by microorganisms during the decomposition of organic matter in water. A higher BOD indicates more organic matter present, leading to less oxygen available for aquatic life. Clean water typically has a BOD of 5 ppm or less.

Given the choices:

X (DO in ppm)	Y (BOD in ppm)
4	8
6	5
4	15
6	12

Analysis of Options:

1. The option X = 4 ppm and Y = 8 ppm indicates relatively low DO, and a high BOD which would not support a clean aquatic environment.
2. Option X = 6 ppm and Y = 5 ppm satisfies the criteria as 6 ppm DO is enough for fish, and 5 ppm BOD indicates clean water.
3. Option X = 4 ppm and Y = 15 ppm presents low DO and extremely high BOD, which is detrimental to aquatic life.
4. Option X = 6 ppm and Y = 12 ppm shows adequate DO but a higher BOD than clean water standards.

Therefore, the correct values which ensure a good condition for fish growth while maintaining clean water are X = 6 ppm and Y = 5 ppm.