Question

Define sewage. Why is it harmful to us?

Hint:

Sewage must be treated in Sewage Treatment Plants (STPs) using heterotrophic microbes before it can be safely released into natural water bodies.

Answer 1

Step 1: Sewage is the municipal wastewater generated daily in cities and towns. It contains large amounts of organic matter and microbes.
Step 2: Many of these microbes are pathogenic (disease-causing), leading to outbreaks of water-borne diseases like cholera, typhoid, and dysentery.
Step 3: When discharged into water bodies, the high organic content leads to high BOD, which depletes dissolved oxygen, causing the death of fish and other aquatic organisms.