Haryana State Board HBSE 7th Class Science Solutions Chapter 18 Wastewater Story Textbook Exercise Questions and Answers.
Haryana Board 7th Class Science Solutions Chapter 18 Wastewater Story
HBSE 7th Class Science Wastewater Story Textbook Questions and Answers
Fill in the blanks :
(a) Cleaning of water is a process of removing _________.
(b) Wastewater released by houses is called _________.
(c) Dried _________ is used as manure.
(d) Drains get blocked by _________ and _________.
(d) chemicals, kitchenwaste.
What is sewage? Explain why it is harmful to discharge untreated sewage into rivers or seas.
Sewage is a liquid containing wastes disposed off by household, industrial and agricultural, activities in water. It is dangerous to release untreated sewage in water because it can pollute the whole source of water. Sewage contain harmful substances and disease causing organisms. It is therefore, dangerous and unsafe to release untreated sewage in water.
Why should oils and fats be not realeased in the drain? Explain.
Oils and fats should not be released in, the drains because they harden the soil in the pipes and block them. Fats get clogged in the holes of the soil in the drain and block it. It does not allow the wastewater to flow and thus the whole sewer system is blocked.
Describe the steps involved in getting clarified water from wastewater.
Water is treated physically, chemically and biologically in wastewater treatment plant.
Following Steps are involved in the purification of water:
(i) At first stage all the physical impurities like stones, rags, napkins, plastic bags, cans, packets etc. are removed. It is done by passing the water through bar screens.
(ii) Then water is taken to grit and sand removal tank where impurities are removed by sedimentation.
(iii) Solids impurities and faeces etc. are collected from the bottom of the water. These solid impurities collected are called sludge. Water is cleared of floatable solids like oil and grease.
(iv) Clarified water is cleared of other impurities by aerator. All disease causing bacteria are removed by chlorination and water is released in various water bodies.
What is sludge? Explain how it is treated.
Sludge is the collected solid waste from the wastewater during the treatment in water treatment plant. Sludge is decomposed in a separate tank by the anaerobic bacteria. Activated sludge is used as manure.
Untreated human excreta is a health hazard. Explain.
Untreated excreta can cause a lot of health related problems. It pollutes soil, water and air. The polluted water contain disease causing bacteria, which can spread epidemics like cholera, meningities etc.
Name two chemicals used to disinfect water.
Chlorine and ozone are the chemical used to clean the wastewater.
Explain the function of bar screens in a wastewater treatment plant.
Bar screens clear the wastewater of all the physical impurities. Large waste objects like napkins, plastics, can sticks, rags etc. are, removed from the wastewater through the bar screens.
Explain the relationship between sanitation and disease.
Sanitation and disease are related each other. It sanitation is there no disease will occur, but if the sanitation is not there various types of diseases will occur and spread. So sanitation should be kept to avoid diseases.
Outline your role as an active citizen in relation to sanitation.
As active citizen we should take care of our personal and environmental sanitation. We should make people around us, aware of the benefits of sanitation we should help the municipal corporations and gram panchayats to cover all the open drains and remove the unhygenic and disease causing substances thrown in’open.
Here is a crossword puzzle : “Good luck !
3. Liquid waste products
4. Solid waste extracted in sewage treatment
6. A word related to hygiene
8. Waste matter discharged from human body
1. Used water
2. A pipe carrying sewage
5. Micro-organisms which causes cholera
7. A chemical to disinfect water
Study the following statements about ozone:
(a) It is essential for breathing of living organisms.
(b) It is used to disinfect water.
(c) It absorbs ultraviolet rays.
(d) Its- proportion in 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
(b) and (c)
Extended Learning – Activities and projects
Construct a crossword puzzle of your own using the keywords.
Do it yourself.
Then and now; Talk to your grand parents 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.
Do it yourself.
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 _________.
(a) The location of the sewage plant.
(b) Treatment capacity.
(c) The purpose of screening as the initial process.
(d) How is air bubbled through the aeration tank?
(e) How safe is the water at the end of the treatment? How is it tested?
(f) Where is the water discharged after treatment?
(g) What happens to the plant during heavy rains?
(h) Is biogas consumed within the plant or sold to other consumers?
(i) What happens to the treatment sludge?
(j) Is there any special effort to protect nearby houses from the plant?
(k) Other observations.
Do it yourself.
HBSE 7th Class Science Wastewater Story Important Questions and Answers
Very Short Answer Type Questions
Write different sources of wastewater?
Household activities, industrial activities and agricultural activities.
Name certain organic impurities in the wastewater.
Animal waste, Human faeces, oil and urine, fruits and vegetables.
Write certain Inorganic impurities in, the wastewater.
Metals, phosphates and nitrates.
Name certain disease causing micro-organism.
Bacterias, Viruses etc.
Which process removes the solids like faeces and other substances from the wastewater?
Grit and sand removal tank.
Which instrument is used to remove floatable solids from the wastewater?
A skimmer is used to remove floatable impurities.
Who decomposes the sludge?
Anaerobic bacteria decompose the sludge.
What helps to clean the clarified water?
Aerobic bacteria helps to clean the clarified water.
Why is ozone and chlorine used?
Ozone and Chlorine is used to kill the bacteria etc. present in the clarified water.
Short Answer Type Questions
How is water’polluted?
Water is used for various’purposes in homes, industries and agriculture. When water is used for cleaning, bathing, washing, dying etc. it pollutes the water. Unwanted waste materials and chemicals etc. get added in the water and this wastes the water.
How “bar screen” and ‘grit and sand removal tank’ help in clarification of water?
When wastewater is passed through bar screens it separates big and large objects like plastics, bags, sticks, can, napkins etc. In grit and sand removal tank other solid impurities like pebbless and etc. are removed.
How is sludge treated?
Sludge is the solid impurities separated from the sewage. It is removed and treated in a separate tank with anaerobic bacteria. During this process biogas is produced which is used to produce electricity. Dried sludge is used as manure.
What are the problem arising due to open drains and other unsanitary conditions?
Open drains and unsanitary conditions produce bad smell. It becomes an idle place of breeding for mosquitoes, files and other harmful insects. These insects spread many harmful diseases and other health hazards.
How the kitchen waste blocks the drains?
Kitchen waste like oils and fats clogs the pores in soil and reduce the Alteration process. It also blocks the pipes by hardening the pipes. Wastes like tealeaves solid food remains, cotton etc. also choke the pipes and slows down flow of oxygen. This slows down the decomposition process by the aerobic bacteria.
Long Answer Type Questions
How defection in open cause health hazards?
Due to lack of proper sewage disposal system a large amount of people in India defecates in open. They use riverbeds, railway lines, fields and drains for this purpose. These excreta dries down and percolate, in soil with rain water. It pollutes the ground water. Excreate along river bed pollutes the river water. In this way water on the ground and under the ground get polluted. This polluted water contains the micro-organisms of various communicable diseases like cholera, typhoid, hepatilis and meningiti it is dysentry etc.
Wastewater Story Class 7 HBSE Notes
- Water is a precious natural resource.
- We cannot imagine our lives without water.
- We waste a lot of water daily in various household and industrial activities Such water is called wastewater.
- The wastewater produced during household activities, industrial activities, and various agricultural processes is also called sewage.
- Sewage is the liquid waste that can cause various diseases and environmental hazards if not managed.
- Sewage is collected from its sources and treated to destroy its harmful constituent to clean it.
- It is made usable in treatment plants and disposed of in various sources of water.
- Drainage systems should be covered to avoid communicable diseases.
- We should not throw waste in the open and should not defecate in open.
- Low-cost disposal methods can be adopted in areas where a proper sewer system is not available.