\u00a0<\/strong><\/td><\/td> <\/td> <\/td> <\/td> <\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nNCERT Solutions Class 7 Science Chapter 13: Wastewater Story<\/h2>\n\n\n\n In the final section of Class 7 Science Chapter 13, we have tried to answer all the questions. All solutions adhere to the latest CBSE curriculum.\u00a0<\/p>\n\n\n\n
Ques 1. Fill in the blanks:<\/strong><\/p>\n\n\n\na. Cleaning of water is a process of removing_______________.<\/strong><\/p>\n\n\n\nb. Wastewater released by houses is called________________.<\/strong><\/p>\n\n\n\nc. Dried______________ is used as manure.<\/strong><\/p>\n\n\n\nd. Drains get blocked by_(1)____________ and_(2)____________.<\/strong><\/p>\n\n\n\nAns:<\/strong><\/p>\n\n\n\na. Pollutant<\/p>\n\n\n\n
b. Sewage\u00a0<\/p>\n\n\n\n
c. Sludge<\/p>\n\n\n\n
d. (1) Cooking oil; (2) fats<\/p>\n\n\n\n
Ques 2. What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.<\/strong><\/p>\n\n\n\nAns:<\/strong> Sewage\u201d is a liquid waste, which primarily contains water with dissolved and suspended impurities.<\/p>\n\n\n\nThe discharge of untreated sewage into rivers and seas will contaminate the water in these water bodies. Further, the consumption of polluted water by humans, terrestrial animals and aquatic animals will cause several diseases in these organisms.\u00a0<\/p>\n\n\n\n
Ques 3. Why should oils and fats be not released in the drain? Explain.<\/strong><\/p>\n\n\n\nAns:<\/strong> Do not dispose of cooking oil and fats down the drain as they can block pipes. Also, oil and fats reduce the effectiveness of soil in filtering water.<\/p>\n\n\n\nQues 4. Describe the steps involved in getting clarified water from wastewater.<\/strong><\/p>\n\n\n\nAns:<\/strong> Here are the steps to get clarified water from wastewater:<\/p>\n\n\n\n\nTo improve the quality of the wastewater, you can use an aquarium aerator to bubble air through the sample in a glass jar.\u00a0<\/li>\n\n\n\n For effective aeration, you must leave the aerator attached overnight, although several hours can also be effective. Alternatively, you can also use a mechanical stirrer or mixer to reduce the unpleasant odour of the wastewater.<\/li>\n\n\n\n Following aeration, the water undergoes filtration through layers of sand, fine gravel, and medium gravel. This filtration process effectively removes various types of pollutants, and it is continued until the water becomes clear.<\/li>\n\n\n\n Finally, water disinfection is achieved by employing a chlorine tablet.<\/li>\n<\/ul>\n\n\n\nQues 5. What is sludge? Explain how it is treated.<\/strong><\/p>\n\n\n\nAns: <\/strong>The solids that settle after the primary treatment are called \u201csludge\u201d.\u00a0<\/p>\n\n\n\nAfter the collection of sludge, it is decomposed using bacteria. In this process of decomposition, a gas is produced.\u00a0<\/p>\n\n\n\n
Ques 6. Untreated human excreta is a health hazard. Explain.<\/strong><\/p>\n\n\n\nAns:<\/strong> Untreated human excreta is a significant health hazard due to the presence of several disease-causing microorganisms and pollutants. These contaminants can pollute the soil and water resources that people rely on for drinking and domestic purposes. When we use water that has been contaminated with human excreta, they are at risk of contracting diseases such as Cholera, Typhoid, Dysentery, and Hepatitis.<\/p>\n\n\n\nQues 7. Name two chemicals used to disinfect water.<\/strong><\/p>\n\n\n\nAns:<\/strong> Ozone and Chlorine<\/p>\n\n\n\nQues 8. Explain the function of bar screens in a wastewater treatment plant.<\/strong><\/p>\n\n\n\nAns:<\/strong> Bar screens are designed to separate large objects such as napkins, rags, cans, sticks, and plastic pouches from the wastewater.<\/p>\n\n\n\nQues 9. Explain the relationship between sanitation and disease.<\/strong><\/p>\n\n\n\nAns:<\/strong> Sanitation typically involves offering facilities and services for the safe disposal of human urine and faeces. Inadequate sanitation causes numerous diseases and health risks as we consume water that is discharged from sewage systems.\u00a0<\/p>\n\n\n\nInefficient sanitation causes the following waterborne diseases:<\/p>\n\n\n\n
\nPolio<\/li>\n\n\n\n Typhoid<\/li>\n\n\n\n Cholera<\/li>\n\n\n\n Dysentery\u00a0<\/li>\n<\/ul>\n\n\n\nQues 10. Outline your role as an active citizen in relation to sanitation.<\/strong><\/p>\n\n\n\nAns: <\/strong>\u00a0As an active citizen, I must contribute to the sanitation process in the following ways:<\/p>\n\n\n\n\nI will keep my surroundings clean.<\/li>\n\n\n\n I will manage my household sanitation system properly.<\/li>\n\n\n\n I will dispose of waste properly and after segregation.<\/li>\n\n\n\n I will report to the concerned authorities about leakages in the sewage system in my neighbourhood.\u00a0<\/li>\n<\/ul>\n\n\n\nQues 11. Here is a crossword puzzle: Good luck!<\/strong><\/p>\n\n\n\nAcross:<\/strong><\/p>\n\n\n\n3. Liquid waste products<\/strong><\/p>\n\n\n\n4. Solid waste extracted in sewage treatment<\/strong><\/p>\n\n\n\n6. A word related to hygiene<\/strong><\/p>\n\n\n\n8. Waste matter discharged from the human body<\/strong><\/p>\n\n\n\nDown:<\/strong><\/p>\n\n\n\n1. Used water<\/strong><\/p>\n\n\n\n2. A pipe carrying sewage<\/strong><\/p>\n\n\n\n5. Micro-organisms which cause cholera<\/strong><\/p>\n\n\n\n7. A chemical to disinfect water<\/strong><\/p>\n\n\n\nAns:<\/strong><\/p>\n\n\n\nAcross:<\/strong><\/p>\n\n\n\n3. Sewage<\/p>\n\n\n\n
4. Sludge<\/p>\n\n\n\n
6. Sanitation<\/p>\n\n\n\n
8. Excreta<\/p>\n\n\n\n
Down:<\/strong><\/p>\n\n\n\n1. Wastewater<\/p>\n\n\n\n
2. Sewer<\/p>\n\n\n\n
5. Bacteria<\/p>\n\n\n\n
7. Ozone<\/p>\n\n\n\n
Ques 12. Study the following statements about ozone:<\/strong><\/p>\n\n\n\na. It is essential for breathing of living organisms.<\/strong><\/p>\n\n\n\nb. It is used to disinfect water.<\/strong><\/p>\n\n\n\nc. It absorbs ultraviolet rays.<\/strong><\/p>\n\n\n\nd. Its proportion in air is about 3%.<\/strong><\/p>\n\n\n\nWhich of these statements are correct?<\/strong><\/p>\n\n\n\n(i) a, b, and c<\/strong><\/p>\n\n\n\n(ii) b and c<\/strong><\/p>\n\n\n\n(iii) a and d<\/strong><\/p>\n\n\n\n(iv) All four<\/strong><\/p>\n\n\n\nAns:<\/strong> Option (ii) b and c<\/p>\n\n\n\n\n\nFAQs<\/h2>\n\n\n\n
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