NCERT Solutions for Class 7 Science Chapter 13 Wastewater Story

1. Fill in the blanks: 

a. Cleaning of water is process of removing ________. 

Ans: Cleaning of water is process of removing contaminants. 

b. Wastewater released by houses is called ________. 

Ans: Wastewater released by houses is called sewage. 

c. Dried ________ is used as manure.

Ans: Dried dung is used as manure. 

d. Drains get blocked by ________ and ________.

Ans: Drains get blocked by plastic and sludge.

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

Ans: Sewage is a kind of used water or wastewater that has been emitted by houses, industries, hospitals, offices, and other users. It also features subsurface storage for rainfall. It may contain dangerous chemicals and organisms that can endanger human life.

Algae can quickly develop when given various nutrients, resulting in a decreased amount of dissolved oxygen in the water. This is why sewage should not be discharged into seas and rivers.

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

Ans: Oil and fats should not be poured down the drain since they are not dissolved in water and float on top of it. It can clog drains and, if released into bodies of water, can harm aquatic life.

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

Ans: Wastewater treatment has physical, chemical, and biological processes.

a. Waste water is filtered using bar screens to eliminate large materials such as rags, twigs, cans, plastic packets, napkins, and so on.

b. Water is routed through a grit and sand removal tank, allowing sand, grit, and pebbles to settle.

c. The water is then allowed to settle in a big settling tank, where solid feces known as sludge is removed using a scarper.

d. Air is poured into the clarified water to assist aerobic bacteria in growing and consuming wastes.

e. Water of this kind is dumped into rivers or ponds.

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

Ans: Sludge is a solid waste material that settles in secondary water treatment. Generally, it is scraped out from the bottom. The clarified water is then discharged. Sludge is stored in a separate tank and treated with anaerobic bacteria, which creates biomass that can be used as bio manure.

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

Ans: Millions of bacteria live in the human stomach and expel with the feces. If human excreta is dumped directly into the soil or water, it can pollute both the water and the soil. Under favorable conditions, the bacteria divide and multiply, and when the water reaches the earth table, it might affect a bigger population that consumes it. It can induce water-borne diseases such as typhoid and cholera.

7. Name two chemicals used to disinfect water. 

Ans: Water disinfection involves removing or deactivating pathogenic bacteria, as well as killing them. Microorganisms are rendered inactive, putting an end to their development and reproduction. If germs are not removed from drinking water, humans will develop unwell from drinking water. Chlorine and ozone are the two chemicals used in water disinfection.

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

Ans: When waste water is pumped through bar screens, it serves as a large screen. In the first step of cleaning water, large materials such as rags, twigs, cans, plastics, and napkins are removed.

9. Explain the relationship between sanitation and disease. 

Ans: Sanitation is a public health issue. Sanitation includes the prevention of disease, the provision of safe drinking water, and the proper disposal of garbage. Diseases are spread when cleanliness standards are not met. Dirty water serves as a breeding ground for mosquitoes that transmit diseases. Improper sewage disposal can result in water-borne sickness. As a result, sanitation is the utmost pathogen rescue and can result in a disease-free environment.

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

Ans: All humans have a responsibility to play in keeping our environment clean as engaged and knowledgeable citizens. We can begin from home. Adopting excellent sanitation techniques should be a way of life for all of us. Our energy, ideas, and excitement can have an impact on others. And encourage people to maintain a healthy living environment for the benefit of society.

11. 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 the human body. 

Down 

1. Used water. 

2. A pipe carrying sewage. 

3. Micro-organisms which cause cholera. 

7. A chemical to disinfect water.

Ans: Across:
3. Liquid waste product- Sewage
4. Solid waste extracted in sewage treatment- Sludge
6. A word related to hygiene- Sanitation
8. Waste matter discharged from human body- Excreta

Down:                                                                                                                                                    1. Used water- wastewater
2. A pipe carrying sewage- Sewer
5. Microorganisms which causes cholera- Bacteria
7. A chemical to disinfect water- Ozone

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

Ans: ii.

Explanation: Ozone, often known as trioxygen, is an inorganic molecule having the formula $\mathrm{O}_{3}$. It's a pale blue gas with a pronounced unpleasant odor. Oxygen is required for living beings to breathe. As a result, statement a. is incorrect

Ozone is a powerful oxidant, even more potent than chlorine. Ozone is used in water to disinfect, deodorize, decolorize, and degrade organic compounds. As a result, statement b. is correct.

The ozone layer, also known as the ozone shield, is an area of the earth's stratosphere that absorbs the majority of the sun's UV radiation. As a result, statement c. is correct.

The concentration of ozone in the atmosphere is $0.000004 \%$. As a result statement d. is incorrect.

Therefore, the correct answer is (ii).

Topics Covered in Class 7 Science Chapter 13 Wastewater Story 

Benefits of Wastewater Story Class 7 Solutions

NCERT Solutions of Wastewater Story class 7 is an easy and scoring chapter offering elementary knowledge and a comprehensive brief.

• Class 7 science wastewater story questions answers understandably and help students comprehend the chapter and the chapter's contents and answer questions efficiently.

• NCERT Solutions for class 7 Science chapter 13 states the importance of Water in every individual's life. 

• The chapter Wastewater Story class 7 briefly explains the transition of clean water into dirty water and the measures that need to be implemented to reuse and recycle Wastewater. 

• NCERT class 7 science wastewater story question answers focus on contaminating issues with natural resource water and its dire consequences. 

• The wastewater story class 7 questions with answers provide an updated syllabus, learning provisions, and revision materials to keep students hassle-free for the rest of the year.

• NCERT Solutions for wastewater story class 7 solutions contain all the important topics and concepts under Wastewater Story. 

• Students can save much time referring to the wastewater management class 7 questions and answers during a test or an exam. 

• The mock exercises, activities, and the list of questions given at the end of the science chapter 13 class 7 question answers create extensive comprehension of all the crucial topics highlighted in the chapter.

Important Study Material Links for Class 7 Science Chapter 13

Conclusion

NCERT Solutions plays a crucial role in wastewater story class 7 exam preparation. Start by thoroughly reading the textbook chapter. After that, solve the class 7 science chapter 13 question answers. You can find detailed solutions on Vedantu that align with CBSE guidelines. Download the free NCERT Solutions for class 7 Science Chapter 13 Wastewater Story to guide your exam preparation with expert-reviewed answers.

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