NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story

 

NCERT solutions for class 7 science chapter 18 Wastewater Story: A life without water is impossible. So it is our duty to avoid overuse or wastage of water. What is sewage? How to treat polluted water? Such questions are explained with the help of solutions of NCERT class 7 science chapter 18 wastewater story. Terms like aeration, aerobic and anaerobic bacteria, biogas etc are explained in the chapter. The CBSE NCERT solutions for class 7 science chapter 18 wastewater story make the preparation of the chapter easy. Students can make their studies interesting through activities. For example, by visiting a sewage treatment plant students can know how practically the treatment plant is running and can relate to what they have studied in the chapter. Solutions of NCERT helps in the preparation of the exam. The solutions of NCERT class 7 science chapter 18 wastewater story give an explanation to all the 12 questions in the exercise. 

 NCERT solutions for class 7 science chapter 18 wastewater story exercise:

1. 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 contaminants.
    (b) Wastewater released by houses is called sewage.
    (c) Dried cow dung is used as manure.
    (d) Drains get blocked by plastic and fats.

2What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.

Answer:

Sewage is wastewater coming out of households, public places, farms and industry. It also includes rainwater which has flown into the sewers.

Untreated sewage contains harmful chemicals which if released directly into the rivers or seas would pollute them harming the ecosystem of the water bodies and making the water unfit for drinking or further use.

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

Answer:

Oils and fats are insoluble in water. When released in the drain, it causes hardening and blocking of the sewage pipes. In an open drain, the fats block the soil pores which is required for filtering water. That is why oil and fats should not be released in the drain.

4. Describe the steps involved in getting clarified water from wastewater.

Answer:

The treatment of wastewater includes the following steps:

(i) First, the physical waste like plastic, rags, pebbles, wood etc is removed by passing the water through a bar screen.

(ii) Then water is sent into sand removal tank for removing sand, pebbles, grit etc. through the process of sedimentation.

(iii) Then the rest of the solid waste is allowed to settle at the bottom of a large settling tank. This waste deposited at the bottom is called sludge and is removed through a scraper.

(iv) The harmful microorganisms in this water are killed through chlorination or UV rays.

(v) Through aerator, air is pumped into this water so that aerobic bacteria can grow and decompose any remaining organic wastes.

(vi) This treated water is then released into the water bodies.

5. What is sludge? Explain how it is treated.

Answer:

Sludge is the solid waste which has settled at the bottom of settling tanks during the process of wastewater treatment.

It is treated by decomposition by anaerobic bacteria. This activated sludge further can be used as manure.

6. Untreated human excreta is a health hazard. Explain.

Answer:

Untreated human excreta contains many harmful organisms which can cause lots of health-related problems. Untreated human excreta pollutes air, water and soil. Epidemics like cholera, meningitis etc. can be spread by untreated human excreta.

7. Name two chemicals used to disinfect water.

Answer:

Two chemicals used to disinfect water are Chlorine and Ozone.

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

Answer:

Bar screens filter most of the large-sized solid waste like plastic, cans, wood etc from wastewater.

9. Explain the relationship between sanitation and disease.

Answer:

Sanitation refers to the availability of clean drinking water and proper treatment of human waste and sewage.

Without proper sanitation various diseases like cholera, typhoid, diarrhoea, etc. would spread and proper sanitation ensures that these diseases do not spread.

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

Answer:

As an active citizen, we should ensure that proper sanitation facilities are available in our home and workplaces, should make people aware about the necessity of sanitation and should not throw garbage in the open as it will block the drains and restrict the flow of the sewage.

Chapterwise NCERT solutions of class 7 science

Chapter No.

Chapter Name

Chapter 1  

NCERT solutions for class 7 science chapter 1 Nutrition in Plants

Chapter 2

Solutions of NCERT class 7 science chapter 2 Nutrition in Animals

Chapter 3

CBSE NCERT solutions for class 7 science chapter 3 Fibre to Fabric

Chapter 4

NCERT solutions for class 7 science chapter 4 Heat

Chapter 5

Solutions of NCERT class 7 science chapter 5 Acids Bases and Salts

Chapter 6

CBSE NCERT solutions for class 7 science chapter 6 Physical and Chemical Changes

Chapter 7

NCERT solutions for class 7 science chapter 7 Weather Climate and Adaptations of Animals to Climate

Chapter 8

Solutions of NCERT class 7 science chapter 8 Winds storms and cyclones

Chapter 9

CBSE NCERT solutions for class 7 science chapter 9 Soil

Chapter 10

NCERT solutions for class 7 science chapter 10 Respiration in Organisms

Chapter 11

Solutions of NCERT class 7 science chapter 11 Transportation in Animals and Plants

Chapter 12

CBSE NCERT solutions for class 7 science chapter 12 Reproduction in Plants

Chapter 13

NCERT solutions for class 7 science chapter 13 Motion and Time

Chapter 14

Solutions of NCERT class 7 science chapter 14 Electric Current and its Effects

Chapter 15

CBSE NCERT solutions for class 7 science chapter 15 Light

Chapter 16

NCERT solutions for class 7 science chapter 16 Water A Precious Resource

Chapter 17     Solutions of NCERT class 7 science chapter 17 Forests Our Lifeline

Chapter 18

CBSE NCERT solutions for class 7 science chapter 18 Wastewater Story

NCERT Solutions for Class 7 Subject Wise

NCERT Solutions for Class 7 Maths

CBSE NCERT Solutions for Class 7 Science

Importance of NCERT solutions for class 7 science chapter 18 wastewater story:

The chapter is important for the exam. One of the main aims is to create awareness about water usage. The CBSE NCERT solutions for class 7 science chapter 18 wastewater story help to understand the concepts studied in the chapter well. Along with the solutions of NCERT class 7 science chapter 18 wastewater theory, doing activities mentioned in the chapter will add an advantage of understanding the chapter in-depth.

 

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