Important Questions Class 7 Science Chapter 18

Important Questions Class 7 Science Chapter 18 – Wastewater Story

The eighteenth chapter of the Class 7 Science curriculum is about Wastewater Story. The chapter covers topics of wastewater, sewage, wastewater treatment plant, sanitation and waterborne disease management, an alternative arrangement for sewage disposal management, etc.

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To score well in Science, students must read through all the chapters and revise by practising a lot of questions. Extramarks understand the importance of regularly solving questions. To help students provide a comprehensive set of questions, our faculty experts have collated questions of varying degrees of difficulty levels from various sources such as NCERT textbook and exemplar, other reference books, past years’ question papers, etc. Our experienced faculty have prepared step-by-step solutions with detailed explanation of all concepts covered in Chapter 18. Students can refer to our Important Questions in Class 7 Science Chapter 18 to start practising. 

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Important Questions Class 7 Science Chapter 18 – With Solutions

Given below are a list of a few questions along with their answers from our question bank of Chapter 18 Class 7 Science Important Questions.

Students can register on the Extramarks website and get full access to our solutions for Science Class 7 Chapter 18 Important Questions.

 

Question 1. What are onsite composting methods?

Answer 1. Onsite composting systems treat wastewater at the point of production rather than transporting it to a treatment facility. Septic tanks, chemical toilets, composting pits, and other onsite composting technologies include septic tanks, chemical toilets, and compost pits, among others. Such onsite solutions can be used because the quantities of sewage created by tiny units are lower than those generated by a large population. The bacterial action composts sewage, and cleaned wastewater is reintroduced into the sewers. The load on the sewage treatment plants is reduced as a result.

 

Question 2. What is the importance of sewage treatment?

Answer 2. Households and industries produce sewage. As a result, it contains a substance that is dangerous to health. Water and solid stuff such as faecal matter make up sewage. If sewage is not treated, the organic material in it provides ideal conditions for the growth of bacteria and other very harmful carrier organisms. These organisms can cause diseases in both humans and animals. Further, sewage has a foul odour that is nauseating and can induce a variety of illnesses. Due to the scarcity of clean water, this is impossible.

Question 3. Explain the steps involved in getting clarified water from wastewater.

Answer 3. Use an aerator from an aquarium to bubble air through the sample in the glass bottle. Allow a few hours for aeration; leave the aerator attached for one day. You can use a mechanical stirrer or a mixer if the aerator is unavailable. This reduces the foul smell of wastewater.

Then, the water is filtered through the sand, fine gravel and medium gravel layers. Filtration makes the wastewater clean from various types of pollutants. The water is filtered continuously until it becomes clear.

Water is disinfected by using a chlorine tablet.

 

Question 4. Name two chemicals used to disinfect water

Answer 4. Chlorine and Ozone chemicals are used to disinfect water.

 

Question 5. Write the function of bar screens in a wastewater treatment plant. 

Answer 5. The bar screen removes large objects like rags, sticks, cans, plastic packets and napkins.

  

Question 6. Outline your role as an active citizen concerning sanitation.

Answer 6. Each citizen has a role in maintaining proper sanitization. Following are some of the ways through which this can be done.

  1. i) Ensure that our surroundings are kept clean.
  2. ii) The sewage system in the house should be managed appropriately

iii) Report to the concerned authority immediately in case of leakages in sewage pipes.

 

Question 7. Define sewage and explain why it is harmful to discharge untreated wastewater into rivers or seas.

Answer 7. Wastewater discharged by houses is called sewage. Untreated sewage should not be discharged directly into the sea because sewage consists of pollutants and harmful microorganisms which will contaminate water, causing disease or sickness among people who consume it. .

 

Question 8. Which is/are the products of wastewater treatment?

(a) Biogas

(b) Sludge

(c) Both biogas and sludge

(d) Aerator

Answer 8. The answer is option (c) Both biogas and sludge.

 

Explanation: Water can settle in a large tank sloped towards the middle during wastewater treatment. Solids like faeces are set at the bottom and are removed with a scraper. This is the sludge. A skimmer removes the buoyant solids like oil and grease. Water that is so clean is called clarified water. The sludge is transferred to another tank where anaerobic bacteria decompose it. The biogas formed in the process can be used as fuel or to produce electricity.

 

Question 9. How are open drains harmful to our health?

Answer 9. The open draining system causes problems with the foul smell. An open drainage system is the breeding source for mosquitos and flies. The available drainage system also helps the growth of disease-causing organisms. Hence drains are harmful to human health.

 

Question 10. What are the various steps of cleaning wastewater in a wastewater treatment plant?

Answer 10. Wastewater treatment involves physical, chemical, and biological processes which remove physical, chemical and biological matter contaminating the wastewater.

  1. Wastewater is passed through bar screens. Large objects like rags, sticks, cans, plastics and napkins are removed.
  2. Water then goes to a stone and sand removal tank. The speed of the incoming wastewater is reduced to allow sand, stones and pebbles to settle down.
  3. The water was then settled in a large tank tilted towards the middle. Solids like faeces are set at the bottom and are removed with a scraper. This is called sludge. A skimmer removes the floatable materials like oil and grease. Water so cleared is called clarified water. The sludge is moved to a separate tank where anaerobic bacteria decompose it. The biogas produced in this process can be used as fuel or to generate electricity.
  4. Air is pumped into the clarified water that helps aerobic bacteria to grow. These bacteria consume human waste, food waste, soaps and other unwanted matter remaining in clarified water. 

After a few hours, the floating microbes were set at the bottom of the tank as activated sludge. The water is then taken from the top. This activated sludge is approx 97% water. Sand drying beds or machines remove the water. Dried sludge is used as manure, and organic matter and nutrients return to the soil. The treated water has a very low organic material and floating matter. It is discharged into a sea, a river or the ground. Nature then cleans it up. Sometimes it is necessary to disinfect water with chemicals like chlorine and ozone before releasing it into the distribution system.

  

Question 11. The terms sewage, sewers and sewerage are interlinked with each other. Can you explain how?

Answer 11. The terms ‘sewage, ‘sewers,’ and ‘sewerage are interlinked with each other because sewage is a mixture of wastewater coming out of homes and other places. Sewers carry sewage, and sewerage is a network of sewage-carrying pipes.

 

Benefits of Solving Important Questions Class 7 Science Chapter 18

Science is a subject that requires constant reading and revising of different topics and concepts covered across all the chapters. Class 7 students are advised to go through Extramarks Important Questions Class 7 Science Chapter 18. The solutions for all the questions are prepared by Science subject experts and will help students thoroughly understand the concepts that are covered in each question. 

Extramarks leaves no stone unturned when it comes to providing the best learning material with unmatchable speed and accuracy for students irrespective of the class and subject.  We have all the answers to your queries. This encourages the students to master the topic and increases their confidence in achieving a high grade. Below are a set of few benefits that students will achieve by solving questions from our question bank: :

  • Our team of subject matter experts at Extramarks has carefully curated the questions and provided the solutions while strictly adhering to the CBSE guidelines and syllabus, so as to make it convenient for students to take all the necessary help and guidance to step up their academic performance. They need not refer to so many other books for additional information. Extramarks is a one-stop solution to all your problems and studies.
  • The questions from our Important Questions Class 7 Science Chapter 18 will be based on all aspects of the chapter, including all topics. This helps students to self-assess their knowledge and understanding of various topics and revise those topics they are weak in and enhance the clarity of concepts that can help them in higher studies as well. .
  • Solving questions helps to understand how to write an answer and make it presentable. We recommend students take guided practice and help to be aware of their mistakes and maximise their potential by learning how to frame the right answer and develop the confidence to get 100% marks in the exams.
  • The student can learn to manage time by solving important questions. That itself reduces stress and anxiety to a great extent.Students need not refer to other books as Extramarks has all the solutions to your problems as it would be a total wastage of time and may lead to unnecessary stress and anxiety

We at Extramarks recommend taking the guided practice and maximise your potential by learning how to frame the right answer and develop the confidence to get 100% marks in the exams. Extramarks provides comprehensive learning solutions for students from Class 1 to Class 12. We have abundant resources on our website and important questions and answers. Students can click on the links given below to access some of these resources:

Q.1 Select the correct order of steps taken in WWTP.

(a). bar screens, scrapper, grit and sand removal tank, aerator, ozone

(b). bar screens, grit and sand removal tank, scrapper, aerator, ozone

(c). bar screens, grit and sand removal tank, scrapper, ozone, aerator

(d). bar screens, grit and sand removal tank, aerator, scrapper, ozone

Marks:1

Ans

(b). bar screens, grit and sand removal tank, scrapper, aerator, ozone

The wastewater is first passed through bar screens which remove big objects. The wastewater is then sent to a grit and sand removal tank. The sludge is then separated from the water with the help of a scrapper, then it is moved to an aerator that pumps air into it. Harmful chemicals are removed by using disinfectants such as the ozone.

Q.2 Which factor is not responsible for increasing the scarcity of fresh water?

(a).Pollution

(b). Population growth

(c). Mismanagement

(d). Chlorination

Marks:1

Ans

(d). Chlorination

Chlorination is used for making water bacteria free.

Q.3 After frying pakoras, some oil with suspended solid impurities was left in the frying pan. Answer the following questions based on the given situation:
a) Can the leftovers be released into the drain? Explain your answer.
b) Suggest a suitable technique by which the leftovers can be managed.

Marks:3

Ans

a) No, the leftover oil cannot be released into the drain because the solid impurities and the oil will clog the drain and will not allow free flow of oxygen. This will hamper the degradation process.
b) The impure oil must be filtered off and the solid impurities must be thrown into the dustbin. The remaining oil must be stored separately in a container and be reused later.

Q.4 Answer the following questions.
1. What is a manhole?
2. Where are manholes located?
3. What is the function of manholes?
4. Define sewers.
5. Which nutrients are found in sewage?

Marks:5

Ans

(a) A large, covered hole on the ground, pavement, or road above the underground sewer system is known as a manhole.
(b) Manholes are positioned every 50 to 60 metres in the sewer, at the intersection of two or more sewers and at spots where the direction of the sewage changes.
(c) The sanitary workers can enter the sewer systems through the manholes to clean or repair any leaks or blockages.
(d) The underground pipes that carry wastewater separately are known as sewers.
(e) Nitrogen and phosphorus are found in sewage.

Q.5 Why is defecation in open considered as a big problem?

Marks:2

Ans

A large fraction of people defecates in the open, on dry river boards, railway tracks and many times directly in water. Due to this, groundwater and surface water gets polluted. This polluted water gives rise to many diseases. Hence, defecation in open is considered as a big problem.

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FAQs (Frequently Asked Questions)

1. Where can a student easily find Important Questions Class 7 Chapter 18?

Students can easily register with Extramarks and gain access to Important Questions Class 7 Science Chapter 18. These important questions cover the entire chapter. Made by subject experts, these questions and their solutions are entirely authentic and exclusive. And help students achieve better grades in their examinations.

 

2. What books are recommended to learn about Chapter 18 Wastewater story and other chapters of Class 7 Science?

The Central Board of Secondary Education (CBSE) recommends NCERT Class 7 Science textbook and exemplar. The textbook has in-depth coverage of each topic with narratives and real-life examples to make learning interesting and engaging for students. It also comes with a lot of exercises and questions to help students check their understanding of the concepts.  The book consists of 18 chapters that discuss important topics from general science. 

Along with NCERT textbooks, students can refer to Extramarks’ comprehensive suite of study materials including NCERT solutions, chapter notes, revision notes, etc.

3. What are the best practices to understand the concepts of the given topics from Class 7 Science?

Students should start their studies by referring to the NCERT textbooks. Along with the textbook, it’s a good idea to refer to reliable study resources from Extramarks. Students can refer to our NCERT solutions which include comprehensive chapter notes covering all aspects of the chapter. Regularly solving questions from our Important Questions Class 7 Science Chapter 18 will further help students to revise the chapter and also understand their weak areas. These solutions will assist students in developing a clear understanding of the key concepts in an easy-to-understand language and help them to get excellent scores.