Chemistry - Environmental Chemistry Question with Solution | TestHub
The large population of bacteria decomposes organic matter present in water, consuming the dissolved oxygen (DO). The amount of oxygen that water can hold is limited.
In cold water, the concentration of dissolved oxygen can reach up to W ppm, whereas oxygen in air is about 200,000 ppm.
If the DO concentration of water falls below X ppm, the growth of fish gets inhibited.
The amount of oxygen required by microorganisms to break down the organic matter in a certain volume of water is called Biochemical Oxygen Demand (BOD).
For clean water, BOD is less than Y ppm, whereas for highly polluted water, it can be Z ppm or more. Calculate the sum of W, X, Y, Z.
Answer:
Solution:
• W (Dissolved Oxygen in cold water) :
"In cold water, dissolved oxygen can reach up to 10 ppm."
• X (Minimum DO for Aquatic life) :
"If the concentration of dissolved oxygen falls below 6 ppm, the growth of fish gets inhibited"
• Y (BOD for clean water) :
"Clean water has BOD value less than 5 ppm"
•Z (BOD for Highly polluted water) :
"Highly polluted water may have BOD value of 17 ppm or more"
W + X + Y + Z = 10 + 6 + 5 +17 = 38
