STD 7 SCIENCE LESSON

TOPIC : WATER

SUBTOPIC : WATER POLLUTION


This is industrial waste emptied into a river. What effect will it have on animals?

What is water pollution?

Water pollution happens when toxic substances enter water bodies such as lakes, rivers, oceans and so on, getting dissolved in them, lying suspended in the water or depositing on the bed. This degrades the quality of water.
         Not only does this spell disaster for aquatic ecosystems, the pollutants also seep through and reach the groundwater, which might end up in our households as contaminated water we use in our daily activities, including drinking.

Sources of water pollution

Water pollution can be caused in a number of ways, one of the most polluting being city

•  sewage discharge. 
• industrial waste discharge. Indirect sources of water pollution include
• contaminants that enter the water supply from soils or groundwater
• contaminants of systems and from the atmosphere via rain.

        Soils and ground waters contain the residue of human agricultural practices and also improperly disposed of industrial wastes.

ANSWER THE FOLLOWING QUESTIONS.
1. Water is polluted by

2. Which one of these is directly affected by industrial pollutant into rivers and lakes?

3. Clear water from the river

4. Rain water is basically polluted by_____

5. Which one of the following is an indirect source of water pollution?

6. City sewage discharge cause water pollution through

7. Ground water is most likely polluted by__

8. High concentration of toxic substances in lakes may lead to

9. The best way to stay safe from drinking polluted water is by___

10. Water stored in tanks should be ____