Home
NCERT Soltions
Class 7
Science
Wastewater Story
What is sewage? Explain why it is harmful to discharge untreated sewag...

What is sewage? Explain why it is harmfu | Class 7 Science Chapter Wastewater Story, Wastewater Story NCERT Solutions

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

Sewage: The waste water and faeces (human excretion) from homes and other buildings which is carried into the sewers is called sewage. Sewage includes household wastewater from kitchen sink, washing machine, washbasin, bathroom shower, bath tub and faeces from the toilet. Sewage is also produced and released by shops, offices, schools, hospitals, factories, industries and all other places where humans work or live. Sewage also includes rainwater that has run down the streets and roads during rains carrying harmful substances with it which also spreads various diseases along it, and flows into sewer pipes. Sometimes, sewage contains harmful and poisonous chemicals that are being discharged by factories and industries. Most of the dirty water contains dissolved and suspended impurities in it which are known as contaminants or pollutants.

Welcome to the NCERT Solutions for Class 7 Science - Chapter Wastewater Story. This page offers a step-by-step solution to the specific question from Exercise 1, Question 2: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.

Question 2:

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

Answer:

Sewage: The waste water and faeces (human excretion) from homes and other buildings which is carried into the sewers is called sewage. Sewage includes household wastewater from kitchen sink, washing machine, washbasin, bathroom shower, bath tub and faeces from the toilet. Sewage is also produced and released by shops, offices, schools, hospitals, factories, industries and all other places where humans work or live. Sewage also includes rainwater that has run down the streets and roads during rains carrying harmful substances with it which also spreads various diseases along it, and flows into sewer pipes. Sometimes, sewage contains harmful and poisonous chemicals that are being discharged by factories and industries. Most of the dirty water contains dissolved and suspended impurities in it which are known as contaminants or pollutants.

Other Questions of Chapter Wastewater Story

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

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-organisms which causes cholera
7. A chemical to disinfect water

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 ____________.

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

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

Name two chemicals used to disinfect water.

Untreated human excreta is a health hazard. Explain.

Describe the steps involved in getting clarified water from wastewater.

What is sludge? Explain how it is treated.

Explain the relationship between sanitation and disease.

Popular questions of class 7 Science

Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
(b) Dissolving sugar in water
(c) Burning of coal
(d) Melting of wax
(e) Beating aluminium to make aluminium foil
(f ) Digestion of food

Given below is a crossword puzzle based on this lesson. Use hints to fill in the blank spaces with letters that complete the words.
Down Across
(D) 1 : Thorough washing (A) 1 : Keeps warm
2 : Animal fibre 2 : Its leaves are eaten by silkworms
3 : Long thread like structure 3 : Hatches from egg of moth

Sketch the cross section of soil and label the various layers.

Solve the following crossword puzzle with the clues given:

Across
2. Plantation prevents it.
5. Use should be banned to avoid soil pollution.
6. Type of soil used for making pottery.
7. Living organism in the soil.

Down
1. In desert soil erosion occurs through.
3. Clay and loam are suitable for cereals like.
4. This type of soil can hold very little water.
5. Collective name for layers of soil.

Take three test-tubes. Fill æth of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO₂?

Sketch the reproductive parts of a flower.

Describe how crystals of copper sulphate are prepared.

Why does an athlete breathe faster and deeper than usual after finishing the race?

Write one similarity and one difference between the nutrition in amoeba and human beings.

Match the following :
(i) Land breeze blows during (a) summer
(ii) Sea breeze blows during (b) winter
(iii) Dark coloured clothes are preferred during (c) day
(iv) Light coloured clothes are preferred during (d) night

Recently Viewed Questions of Class 7 Science

What are the components of blood?

Name the source from which litmus solution is obtained. What is the use of this solution?

Classify the following as motion along a straight line, circular or oscillatory motion:

(i) Motion of your hands while running.
(ii) Motion of a horse pulling a cart on a straight road.
(iii) Motion of a child in a merry-go-round.
(iv) Motion of a child on a see-saw.
(v) Motion of the hammer of an electric bell.
(vi) Motion of a train on a straight bridge.

Match the items given in Column I with those in Column II:
Column I Column II
Chlorophyll Bacteria
Nitrogen Heterotrophs
Amarbel Pitcher plant
Animals Leaf
Insects Parasite

How do elephant living in the tropical rainforest adapt itself?

Out of the following, which are the two terms related to silk production? Sericulture, floriculture, moriculture, apiculture and silviculture.

Hints:
(i) Silk production involves cultivation of mulberry leaves and rearing silkworms.
(ii) Scientific name of mulberry is Morus alba.

A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

Describe how crystals of copper sulphate are prepared.

The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it
becomes a gas (Change – A) then it burns (Change – B). The following statements pertain to these changes. Choose the correct one.

(i) Process – A is a chemical change.
(ii) Process – B is a chemical change.
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change.

Can we survive only on raw, leafy vegetables/grass? Discuss.

Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

Read the question carefully and focus on the core concept being asked.
Reference examples and data from the chapter when answering questions about Wastewater Story.
Review previous year question papers to get an idea of how such questions may be framed in exams.
Practice answering questions within the time limit to improve your speed and accuracy.
Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Why Self-Discipline is More Important Than Motivation for Students

Have you ever noticed that doing activities such as playing outdoors, chilling with your friends, or using the mobile phone feels so effortless and fun? Whenever you might have played sports, you kept on playing even when it felt hard initially just so you could get that feeling after the game, a feeling of accomplishment, … Read more

How Visualization Strategies Can Improve Test Performance

Imagine this; You’re sitting in the test hall, pen in hand, and the question paper has been put in front of you. Rather than freezing, you feel calm, collected, and set. Why? As you have formerly been there in your mind. You’ve seen yourself sitting composibly, reviewing the question paper fluently, performing well in the … Read more

Smart Questions to Ask in a Parent-Teacher Meeting | PTM Made Easy

Parent-Teacher Meetings (PTMs) are more than quick updates on marks — they’re a chance to build a real partnership between home and school. A good Parent-Teacher Meeting conversation helps parents see beyond grades. It opens up insights about a child’s strengths, struggles, emotions and even hidden talents. When parents participate actively, they don’t just track … Read more

The Secret to Smarter Learning — Building Strong Critical Thinking Skills

In today’s world of endless information , knowing how to think is more important than knowing what to think . From school projects to real – life decisions , critical thinking helps students question ideas , analyze facts and form logical conclusions . But what exactly does critical thinking mean ? Simply put , it’s … Read more

View All Blog Posts