CBSE Class 9 Answered

• It consists of kitchen, toilet and other household waste water.
• In cities and industrial areas, the sewage is released in lakes and rivers.
• Organisms present in water compete with aquatic life for the utilisation of oxygen.

2. Industrial waste pollution-

• This water consists of many dissolved chemicals.
• Fish processing units located near the sea coast release many toxic substances into the sea.

3. Oil spillage

• It is the accidental discharge of petroleum in oceans or estuaries.
• The sources of oil spills are overturned oil tankers, offshore oil mining and oil refineries.
• Oil spills kill a lot of marine life.

4. Thermal Pollution

• Hot water released by thermal power stations brings about temperature fluctuations in water bodies.
• Aquatic animals cannot adapt to these temperature fluctuations which lead to their death.

5. Chemical pollution-

• Nitrates, phosphates and other chemicals used in pest and weed control are washed into rivers, lakes and ultimately into oceans.