NCERT Solutions for Class 7 Science Chapter 18

Wastewater Story Class 7

Chapter 18 Wastewater Story Exercise Solutions

<< Previous Chapter 17 : Forests: Our Lifeline

Exercise : Solutions of Questions on Page Number : 228

Q1 :  

Fill in the blanks:

(a) Cleaning of water is a process of removing _______.

(b) Wastewater released by houses is called ________.

(c) Dried _______ is used as manure.

(d) Drains get blocked by ________and ________.


Answer :

(a) Cleaning of water is a process of removing __pollutants__.

(b) Wastewater released by houses is called __sewage__.

(c) Dried __sludge__is used as manure.

(d) Drains get blocked by __cooking oil__and __fats__.

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Q2 :  

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


Answer :

Sewage is the wastewater containing both liquid and solid wastes produced by human activities from homes, industries, hospitals, offices, etc.

Sewage contains various contaminants including disease-causing bacteria and other microbes. If untreated sewage is discharged into rivers or seas, then the water in the rivers or seas would also get contaminated. If this contaminated water is used for drinking, then it can cause diseases such as cholera, typhoid, dysentery, etc. which may lead to death. That is why it is harmful to discharge untreated sewage into rivers or seas.

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Q3 :  

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


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Q4 :  

Describe the steps involved in getting clarified water from wastewater.


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Q5 :  

What is sludge? Explain how it is treated.


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Q6 :  

Untreated human excreta is a health hazard. Explain.


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Q7 :  

Name two chemicals used to disinfect water.


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Q8 :  

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


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Q9 :  

Explain the relationship between sanitation and disease.


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Q10 :  

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


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Q11 :  

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-organismwhich causes cholera

7. A chemical to disinfect water


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Q12 :  

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


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<< Previous Chapter 17 : Forests: Our Lifeline

Science : CBSE NCERT Exercise Solutions for Class 7th for Wastewater Story will be available online in PDF book form soon. The solutions are absolutely Free. Soon you will be able to download the solutions.

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