Question

What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer 1

Sewage is the wastewater produced by human activities from homes, industries, hospitals, offices, etc. Sewage contains various contaminants including disease-causing bacteria and other microbes.
If untreated sewage is discharged into rivers or seas, then the water in the rivers or seas would also get contaminated. If this contaminated water is used for drinking, then it can cause diseases such as cholera, typhoid, dysentery, etc. That is why it is harmful to discharge untreated sewage into rivers or seas.