Solution of Chapter 18. Wastewater Story (NCERT Science Book)

Fill in the blanks:

a. Cleaning of water is process of removing_____.

b. Wastewater released by houses is called_____.

c. Dried _______ is used as manure.

d. Drains get blocked by ______ and _______.

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

Why should oils and fats be not released in the drain? Explain.

Describe the steps involved in getting clarified water from wastewater.

What is sludge? Explain how it is treated.

Untreated human excreta is a health hazard. Explain.

Name two chemicals used to disinfect water.

Explain the function of bar screens in a wastewater treatment plant.

Explain the relationship between sanitation and disease.

Outline your role as an active citizen in relation to sanitation.

Here is a crossword puzzle: Good luck!

Across

3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from human body

Down

1. Used water

2. A pipe carrying sewage

5. Micro-organisms which causes cholera

7. A chemical to disinfect water

Study the following statements about ozone:

(a) It is essential for breathing of living organisms.

(b) It is used to disinfect water.

(c) It absorbs ultraviolet rays.

(d) Its proportion in air is about 3%.

Which of these statements are correct?

(i) (a), (b) and (c)

(ii) (b) and (c)

(iii) (a) and (d)

(iv) All four

Correct