Question

Explain why it is harmful to discharge untreated sewage into rivers and seas.

Answer 1

• Sewage is the wastewater from homes (domestic liquid waste) as well as from industries, offices, hospitals and other places.
• All the wastewater that is released from various sources forms the sewage which contains suspended impurities. These impurities are called contaminants.
• The contaminants may be classified as:

Organic impurities	Human faeces, animal waste, urine, oil, pesticides, fruits and vegetable wastes etc.
Inorganic impurities	Nitrates, phosphates, metals
Nutrients	Phosphorus, nitrogen
Bacteria	Causing cholera, typhoid.
Other microbes	Causing dysentery

• River water is used for different purposes like washing, bathing, drinking. Clean sea water is essential for marine life.
• So, if untreated sewage is discharged into water bodies, it can spread harmful diseases and even cause death.
• Sewage must always be treated in wastewater treatment plants before being released into water bodies.