{"id":24539,"date":"2021-06-18T18:30:25","date_gmt":"2021-06-18T13:00:25","guid":{"rendered":"https:\/\/mcq-questions.com\/?p=24539"},"modified":"2022-03-02T10:38:17","modified_gmt":"2022-03-02T05:08:17","slug":"ncert-solutions-for-class-7-science-chapter-18","status":"publish","type":"post","link":"https:\/\/mcq-questions.com\/ncert-solutions-for-class-7-science-chapter-18\/","title":{"rendered":"NCERT Solutions for Class 7 Science Chapter 18 Wastewater Story"},"content":{"rendered":"
These NCERT Solutions for Class 7 Science<\/a> Chapter 18 Wastewater Story Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.<\/p>\n Question 1. Question 2. The untreated sewage can harm the rivers and seas as the contaminated water pollutes the whole source of water. As the sewage water may contain harmful substances and disease causing organisms, it is dangerous to release the untreated sewage into the water bodies.<\/p>\n Question 3. Question 4. Question 5. <\/p>\n Question 6. Question 7. Question 8. Question 9. Question 10. <\/p>\n Question 11. Question 12. NCERT Extended Learning Activities and Projects<\/span><\/p>\n Question 1. Question 2. <\/p>\n Activity 1<\/span><\/p>\n Objective: To locate an open drain near your home, school or on the road side and inspect water flowing through it.Wastewater Story NCERT Solutions for Class 7 Science Chapter 18<\/h2>\n
Class 7 Science Chapter 18 Wastewater Story Textbook Exercise Questions and Answers<\/h3>\n
\nFill in the blanks:
\na. Cleaning of water is a process of removing ……………….
\nb. Wastewater released by houses is called ……………….
\nc. Dried ………………. is used as manure.
\nd. Drains get blocked by ………………. and ……………….
\nAnswer:
\na. pollutants,
\nb. sewage,
\nc. sludge,
\nd. oils, fats<\/p>\n
\nWhat is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
\nAnswer:
\nWater containing liquid wastes disposed from domestic household activities, industrial activities and agricultural activities is termed as sewage.<\/p>\n
\nWhy should oils and fats be not released in the drain? Explain.
\nAnswer:
\nOils and fats can block the drains. In open drains, they block the pores in the soil and thus hamper the filtration by soil. Hence, oils and fats should not be released in the drains.<\/p>\n
\nDescribe the steps involved in getting clarified water from wastewater.
\nAnswer:
\nThe following steps are involved in clarifying wastewater:<\/p>\n\n
\nWhat is sludge? Explain how it is treated.
\nAnswer:
\nThe solid waste which settles at the bottom of the sedimentation tank is called sludge. The sludge is further treated by the process of aeration. This helps in growth of bacteria which eat away the human waste. Activated sludge is used as manure.<\/p>\n
\nUntreated human excreta is a health hazard. Explain.
\nAnswer:
\nUntreated human excreta contains many microbes which can cause deadly diseases like cholera, diarrhoea, jaundice and typhoid. The germs of these diseases can easily reach human population through insects and through contaminated food and water. Thus, untreated human excreta is a health hazard.<\/p>\n
\nName two chemicals used to disinfect water.
\nAnswer:
\nBleaching powder and chlorine tablets.<\/p>\n
\nExplain the function of bar screens in a wastewater treatment plant.
\nAnswer:
\nBar screens are large filters which are placed in the form of vertical screens. Large solid wastes like sticks, pebbles, sand, cans, plastic bottles, plastic bags, etc., are filtered out when the wastewater moves through the bar screens.<\/p>\n
\nExplain the relationship between sanitation and disease.
\nAnswer:
\nProper sanitation should be maintained in order to avoid diseases. They are related to each other. By sanitation, proper disposal of sewage and refuse from household and public places is carried out. Implementation of proper sanitation results in a state where we are free from any diseases. Lack of it may lead to various diseases.<\/p>\n
\nOutline your role as an active citizen in relation to sanitation.
\nAnswer:
\nAs an active citizen, we should take care of our personal environmental sanitation. For this, we should follow these steps:<\/p>\n\n
\nHere is a crossword puzzle. Good luck!
\n
\nAcross:
\n3. Liquid waste products
\n4. Solid waste extracted in sewage treatment
\n6. A word related to hygiene
\n8. Waste matter discharged from humans
\nDown:
\n1. Used water
\n2. A pipe carrying sewage
\n5. Micro-organisms which cause cholera
\n7. A chemical to disinfect water
\nAnswer:
\n1. Wastewater
\n2. Sewer
\n3. Sewage
\n4. Sludge
\n5. Bacteria
\n6. Sanitation
\n7. Ozone
\n8. Excreta<\/p>\n
\nStudy the following statements about ozone:
\n(a) It is essential for breathing of living organisms.
\n(b) It is used to disinfect water.
\n(c) It absorbs ultraviolet rays.
\n(d) Its proportion in air is about 3%. Which of these statements are correct?
\n(i) (a), (b) and (c)
\n(ii) (b) and (c)
\n(iii) (a) and (d)
\n(iv) All four
\nAnswer:
\n(ii) (b) and (c)<\/p>\n
\nThen 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.
\nHint:
\nDo it yourself<\/p>\n
\nVisit a sewage treatment plant.
\nIt 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.
\nRecord in your notepad:
\nPlace …………..
\nDate …………..
\nTime …………..
\nName of the official at the plant ………….. Guide\/
\nTeacher …………..
\na. The location of the sewage plant.
\nb. Treatment capacity.
\nc. The purpose of screening as the initial process.
\nd. How is air bubbled through the aeration tank?
\ne. How safe is the water at the end of the treatment? How is it tested?
\nf. Where is the water discharged after treatment?
\ng. What happens to the plant during heavy rains?
\nh. Is biogas consumed within the plant or sold to the other consumers?
\ni. What happens to treated sludge?
\nj. Is there any special effort to protect nearby houses from the plant?
\nk. Other observations.
\nHint:
\nDo it yourself with the help of your teacher.<\/p>\n
\nProcedure: Visit the nearby drain and observe it carefully.
\nObservations:<\/p>\n