NCERT Solutions | Class 7 Science Chapter 18

NCERT Solutions | Class 7 Science Chapter 18 | Wastewater Story 

NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story

CBSE Solutions | Science Class 7

Check the below NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story Pdf free download. NCERT Solutions Class 7 Science  were prepared based on the latest exam pattern. We have Provided Wastewater Story Class 7 Science NCERT Solutions to help students understand the concept very well.

NCERT | Class 7 Science

NCERT Solutions Class 7 Science
Book: National Council of Educational Research and Training (NCERT)
Board: Central Board of Secondary Education (CBSE)
Class: 7th
Subject: Science
Chapter: 18
Chapters Name: Wastewater Story
Medium: English

Wastewater Story | Class 7 Science | NCERT Books Solutions

You can refer to MCQ Questions for Class 7 Science Chapter 18 Wastewater Story to revise the concepts in the syllabus effectively and improve your chances of securing high marks in your board exams.

ncert science class 7 book, Question 1.

Fill in the blanks:

  1. Cleaning of water is a process of removing ……….
  2. Wastewater released by houses is called ……….
  3. Dried …….. is used as manure.
  4. Drains get blocked by …….. and ……

ncert class 7 science Chapter 18 question answer, Answer :

  1. pollutants
  2. sewage
  3. sludge
  4. cooking oils and fats

ncert science class 7 Chapter 18, Question 2.

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

cbse science class 7 solutions, Answer :

Sewage is wastewater released by homes, industries, hospitals, offices, and other users. It also includes rainwater that has run down the street during a storm or heavy rain. The water that washes off roads and rooftops carries harmful substances with it. Sewage is a liquid waste. Mostly, sewage contains water, which has dissolved and suspended impurities which are called contaminants. That is why it is harmful to discharge untreated sewage into rivers or seas.

ncert science class 7 pdf free download, Question 3.

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

ncert class 7 science Chapter 18 question answer, Answer :

Oils and fats should not be thrown down the drain. They get hard and block the pipes. In an open drain, the fats clog the soil pores reducing their effectiveness in filtering water.

ncert science class 7 solutions, Question 4.

Describe the steps involved in getting clarified water from wastewater.

cbse science class 7 solutions, Answer :

Following steps are involved in getting clarified water from wastewater:
(i) Firstly, wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastic packets, napkins are removed.

(ii)
Water then, goes to a grit and sand removal tank. The speed of the incoming wastewater is decreased to allow sand, grit, and pebbles to settle down

(iii)
The water is then allowed to settle in a large tank which is sloped towards the middle. Solids like faeces settle at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the floatable solids like oil and grease. Water so cleared is called clarified water. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.

(iv)
Air is pumped into the clarified water to help aerobic bacteria to grow. Bacteria consume human waste, food waste, soaps, and other unwanted matter still remaining in clarified water. After several hours, the suspended microbes settle at the bottom of the tank as activated sludge. The water is then removed from the top. The activated sludge is about 97% water. The water is removed by sand drying beds or machines. Dried sludge is used as manure, returning organic matter and nutrients to the soil.

The treated water has a very low level of organic material and suspended matter. It is discharged into a sea, a river or into the ground. Nature cleans it up further. Sometimes it may be necessary to disinfect water with chemicals like chlorine and ozone before releasing it into the distribution system.

ncert science class 7 textbook pdf, Question 5.

What is sludge? Explain how it is treated.

ncert class 7 science Chapter 18 question answer, Answer :

Solids like faeces which settle at the bottom of the tank and are removed with a scraper are called sludge. The sludge is transferred to a separate tank where it is decomposed by the anaerobic bacteria. The biogas produced in the process can be used as fuel or can be used to produce electricity.

NCERT Solutions for Class 7 Science, Question 6.

Untreated human excreta is a health hazard. Explain.

cbse science class 7 solutions, Answer :

Untreated human excreta is a health hazard. It may cause water pollution and soil pollution. Both the surface water and groundwater get polluted. Groundwater is a source of water for wells, tube-wells, springs, and many rivers. Thus, it becomes the most common route for water-borne diseases. They include cholera, typhoid, polio, hepatitis, and dysentery.

NCERT Solutions for Class 7 Science Chapter 18, Question 7.

Name two chemicals used to disinfect water.

ncert class 7 science Chapter 18 question answer, Answer :

  • Chlorine
  • Ozone

science class 7 Chapter 18, Question 8.

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

cbse science class 7 solutions, Answer :

Wastewater is passed through bar screens for removal of large objects such as rags, sticks, cans, plastic packets, napkins, etc.

science class 7 pdf, Question 9.

Explain the relationship between sanitation and disease.

ncert class 7 science Chapter 18 question answer, Answer :

Sanitation is the hygienic means of promoting health through the prevention of hazards of wastes as well as the treatment and proper disposal of sewage wastewater.
Poor sanitation is a major cause of diseases worldwide and improving sanitation is known to have a significant beneficial impact on households and across communities. So poor sanitation and contaminated water is the cause of a large number of diseases.

cbse class 7 science book, Question 10.

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

cbse science class 7 solutions, Answer :

We all have a role to play in keeping our environment clean and healthy. We must realize our responsibility in maintaining the water sources in a healthy state. Through good sanitation practices, we keep our environment clean and healthy. We should make people aware of the benefits of sanitation and help municipal corporations to cover all the open drains and remove disease-causing substances thrown in open.

cbse class 7 science Chapter 18, Question 11.

Here is a crossword puzzle. Good luck!
Across:
3. Liquid waste products
4. Solid waste extracted in sewage treatment fi. A word related to hygiene
8. Waste matter discharged from the human body.
Down:
1. Used water
2. A pipe carrying sewage
5. Microorganisms which cause cholera
7. A chemical to disinfect water
NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story Q.11.1

ncert class 7 science Chapter 18 question answer, Answer :

Across:
3. Sewage
4. Sludge
6. Sanitation
8. Excreta
Down:
1. Wastewater
2. Sewer
5. Bacteria
7. Ozone
NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story Q.11.2

cbse class 7 science notes pdf, Question 12.

Study the following statements about ozone:
(a) It is essential for the breathing of living organisms.
(b) It is used to disinfect water.
(c) It absorbs ultraviolet rays.
(d) Its proportion in the 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

cbse science class 7 solutions, Answer :

(ii) (b) and (c)

NCERT Class 7 Science

Class 7 Science Chapters | Science Class 7 Chapter 18

NCERT Solutions for Class 7 Science

NCERT Solutions of Science Class 7 Chapter-wise

Chapter-wise NCERT Solutions for Class 7 Science

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