NCERT Solution - Wastewater Story Class 7 Notes | EduRev

NCERT Textbooks (Class 6 to Class 12)

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UPSC : NCERT Solution - Wastewater Story Class 7 Notes | EduRev

The document NCERT Solution - Wastewater Story Class 7 Notes | EduRev is a part of the UPSC Course NCERT Textbooks (Class 6 to Class 12).
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Q.1. Fill in the blanks:
(a) Cleaning of water is a process of removing _______
Ans. Contaminants

(b) Wastewater released by houses is called _______
Ans. Sewage

(c) Dried _______ is used as manure.
Ans. Sludge

(d) Drains get blocked by _______ and _______
Ans. Cooking oil and fats

Q.2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
Ans. Wastewater released by houses is called sewage. Untreated sewage should not be discharged untreated into the sea because sewage consists of pollutants and harmful microorganisms which will contaminate water spreading diseases among people.

Q.3. Why should oils and fats be not released in the drain? Explain.
Ans. Oils and fats should not be released in the drain because drains get blocked by cooking oil and fats.

Q.4. Describe the steps involved in getting clarified water from wastewater.
Ans. The following steps are involved in clarifying wastewater:

  • Insoluble waste is removed by filtration and sedimentation processes.
  • Bacteria are allowed to grow through the process of aeration. Bacteria eat away human waste from the wastewater.
  • Chlorination is used to kill the germs in clarified water. After this step, the water becomes fit even for human consumption.


Q.5. What is sludge? Explain how it is treated.
Ans. Sludge is a semi-solid slurry that can be produced from a range of industrial processes, from water treatment, wastewater treatment or on-site sanitation systems or Semi-solids such as faeces that settle down during wastewater treatment are called sludge. This sludge is removed using a scraper and then transferred to a tank where it is decomposed by anaerobic bacteria to produce biogas. This biogas is used as a low-cost fuel for heating, cooking, etc. It is also used to produce electricity. Dried Sludge is used as manure instead of taking up space in a landfill or other disposal facility to improve and maintain productive soils and stimulate plant growth because it has nutrient-rich organic materials.


Q.6. Untreated human excreta is a health hazard. Explain.
Ans. Untreated human excreta contains many microbes which can cause deadly diseases; like cholera, diarrhea, jaundice and typhoid. The germs of these diseases can easily reach human population through insects and through contaminated food and water. Thus, untreated human excreta are a health hazard.

Q.7. Name two chemicals used to disinfect water.
Ans. Bleaching Powder and Chlorine Tablets

Q.8. Explain the function of bar screens in a wastewater treatment plant.
Ans. Bar screens are large filters which are placed in the form of vertical screens. Large solid wastes like sticks, pebbles, sand, cans, plastic bottles, plastic bags, etc. are filtered out when the wastewater moves through the bar screen.
NCERT Solution - Wastewater Story Class 7 Notes | EduRev
Q.9. Explain the relationship between sanitation and disease.
Ans. Sanitation and disease are closely related. Lack of sanitation leads to unhygienic conditions which creates many communicable diseases. Maintenance of sanitation removes the chances of such diseases.

Q.10. Outline your role as an active citizen in relation to sanitation.
Ans. My role as an active citizen can be in maintaining sanitation in the neighbourhood and at public places. For this, I shall follow these steps:

  • Throwing garbage at designated places and in garbage bins.
  • Preventing clogging of drains by not releasing oil and fat and solid waste into the drain.
  • Using a dustbin to throw trash at public places.
  • By not spitting at public places.


Q.11. 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
Ans. (ii) b and c


Q.12. Here is a crossword puzzle. Good Luck!
NCERT Solution - Wastewater Story Class 7 Notes | EduRev

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
Ans. 
Across
3. Sewage
4. Sludge
6. Sanitation
4. Excreta
Down
1. Wastewater
2. Sewer
5. Bacteria
7. Ozone

NCERT Solution - Wastewater Story Class 7 Notes | EduRev 

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