Question

Organic matter is considered as a major source of water pollution caused by wastes of food, animal and human excreta, garbage etc. The excess of organic matter in water causes a threat to aquatic life because ?

• A. the space available to aquatic life decreases
• B. microorganisms consume dissolved oxygen to decompose organic matter
• C. organic matter is swallowed by small animals
• D. decomposition of organic matter increases the temperature of water.

Answer 1

The correct option is B microorganisms consume dissolved oxygen to decompose organic matter

Aquatic life depends on account of oxygen. If it falls down below 6 ppm, the aquatic life falls under threat. Deoxygenation of water occurs by microorganisms as follows,

$HCHO\left(aq\right)+O_2\left(aq\right)\to C{O}_2\left(aq\right)+H_{2}O\left(l\right)$

This leads to the pollution of water.