CBSE Solution for Class 8 Science Water Pollution – Chapter 18

CBSE Solution for Class 8 Science Water Pollution – Chapter 18

In the previous article, Air Pollution, its effects, and prevention methods from Pollution of Air and Water of Class 8 Science were discussed. Now, we will discuss water pollution, its effects, and prevention.

Water Pollution

We are surrounded by water in the form of rivers, lakes, ponds, oceans and even in the air present in the form of water vapours. It is one of the most abundant and main compounds on the Earth. 75% of the Earth’s surface is covered with water. The main sources of water supply are: –

• Surface water from springs, waterfalls, rivers lakes, etc
• Groundwater which is taken out from wells
• Salty water

All living beings need water to carry out life processes. Therefore, it is called a supporter of the life but somehow due to human negligence, we are polluting water. The main causes of the water pollution are:-

• Untreated industrial and domestic sewage in water bodies directly.
• Draining of Inorganic pesticides and chemical fertilizers directly into the water by farmers. Some pesticides like DDT enter into aquatic animal bodies and eventually reach to human beings.
• Animals bathing, washing clothes near water sources.
• Leakage of oil from boats, ships etc pollute river and oceans.

Now, we will explain the effects of water pollution

Effects of Water Pollution

1. Aquatic plants and animals reduced or killed by pollutants in their habitat.
2. Untreated domestic sewage becomes a  place to the birth of organisms that cause water-borne diseases
3. Water contamination with mercury leads to blurred vision and mental disorder, numbness of limbs, lips, and tongue.
4. Industrial domestic sewage released into water bodies contains a lot of toxic substances.

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Prevention of Water Pollution

1. Domestic and industrial sewage wastes should be treated to remove toxic substances.
2. Bathing and washing clothes near water bodies should be avoided.
3. Pollution control rules enforced by the government.
4. Eco-friendly fertilizers and herbicides should be encouraged.

Purification of Water

Water supplied to our homes is purified by the three main process through which water undergoes purification is sedimentation, filtration, and chlorination.

1. Water collected from the source made free of large pieces of dirt and pumped into reservoirs.
2. Water is stirred in a flocculation tank, which helps in forming lumps of the particle for their easy removal.
3. Water is allowed to stand in large tanks so that suspended impurities settle down. This process is called sedimentation.
4. Water is passed through filter beds to remove all other insoluble impurities. This process is called filtration
5. Water is chlorinated to kill any harmful microorganisms that may be present in it.
6. Filtered water is stored.
7. Water is supplied to homes and factories by huge water mains.

Impure water can be purified by various methods such as filtration, distillation and sedimentation.

Filtration:-In this method, insoluble impurities are removed by passing impure water through a filter or filter paper.

Sedimentation:-This method keeps the water still without any disturbance in a container, which allows insoluble impurities to settle at the bottom. Clean water is transferred in a clean container.

Distillation: – In this method, impure water is heated to its boiling point to convert water into steam. The impurities are left in the container/the steam is passed through a condenser, where it cools and changes back into liquid water.

Sample papers, practice papers for Class 8 Science are available, click Science Class 8 for more details.

Learn Class 8 Science – Chapter 18 Pollution of Air here…

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