Q. Biochemical Oxygen Demand (BOD) in a river water:
A) has no relationship with concentration of oxygen in the water.
B) gives a measure of salmonella in the water.
C) increases when sewage gets mixed with river water.
D) remains unchanged when algal bloom occurs.
Explanation
[Solution from source] BOD is the amount of oxygen consumed when microbes oxidise the organic matter in a litre of water; sewage adds a lot of organic matter, so BOD rises. BOD is about oxygen use by microbes in general, not a count of Salmonella. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.