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NCERT solutions Science Class 7 chapter 18 Wastewater Story


NCERT Science Class 7

Science Textbook for Class  7

Chapter 18 - Wastewater Story

Pages 228 - 229

Fill in the blanks:

Cleaning of water is a process of removing _______.

Q 1 | Page 228

Fill in the blanks:

Wastewater released by houses is called ________.

Q 1.2 | Page 228

Fill in the blanks:

Dried _______ is used as manure.

Q 1.3 | Page 228

Fill in the blanks:

Drains get blocked by ________ and ________.

Q 1.4 | Page 228

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

Q 2 | Page 228

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

Q 3 | Page 228

Describe the steps involved in getting clarified water from wastewater.

Q 4 | Page 228

What is sludge? Explain how it is treated.

Q 5 | Page 228

Untreated human excreta is a health hazard. Explain.

Q 6 | Page 228

Name two chemicals used to disinfect water.

Q 7 | Page 228

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

Q 8 | Page 228

Explain the relationship between sanitation and disease.

Q 9 | Page 228

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

Q 10 | Page 228

Here is a crossword puzzle: Good luck!


3. Liquid waste products

4. Solid waste extracted in sewage treatment

6. A word related to hygiene

8. Waste matter discharged from human body


1. Used water

2. A pipe carrying sewage

5. Micro-organism which causes cholera

7. A chemical to disinfect water




Q 11 | Page 228

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?

1) (a), (b) and (c)

2) (b) and (c)

3) (a) and (d)

4) All four

Q 12 | Page 229

NCERT Science Class 7

Science Textbook for Class  7