NCERT solutions for Science [English] Class 7 chapter 13 - Wastewater Story [Latest edition]

Cleaning of water is a process of removing ______.

Wastewater released by houses is called ______.

Dried ______ is used as manure.

Drains get blocked by ______ and ______.

What is sewage?

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

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

Describe the steps involved in getting clarified water from wastewater.

What is sludge?

Explain how sludge is treated.

Untreated human excreta is a health hazard. Explain.

Name two chemicals used to disinfect water.

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

Explain the relationship between sanitation and disease.

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

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-organism which causes cholera

7. A chemical to disinfect water

Study the following statements about ozone:

1. It is essential for breathing of living organisms.
2. It is used to disinfect water.
3. It absorbs ultraviolet rays.
4. Its proportion in air is about 3%.

Which of these statements are correct?

Construct a crossword puzzle of your own using the keywords.

Then and now: Talk to your grandparents and other elderly people in the neighbourhood. Find out the sewage disposal systems available to them. You can also write letters to people living in far off places to get more information. Prepare a brief report on the information you collected.

Visit a sewage treatment plant.

It could be as exciting and enriching as a visit to a zoo, a museum, or a park. To guide your observation here are a few suggestions.

Record in your notepad:

Place ______ Date ______ Time ______

Name of the official at the plant ______ Guide/Teacher ______

1. The location of the sewage plant.
2. Treatment capacity.
3. The purpose of screening as the initial process.
4. How is air bubbled through the aeration tank?
5. How safe is the water at the end of the treatment? How is it tested?
6. Where is the water discharged after treatment?
7. What happens to the plant during heavy rains?
8. Is biogas consumed within the plant or sold to other consumers?
9. What happens to the treated sludge?
10. Is there any special effort to protect nearby houses from the plant?
11. Other observations.