Friday, December 30, 2011

CBSE 7th Waste Water Story management Solved Sample questions

Q1. State various uses of water.
Ans. Water is used for: • Drinking • Cooking • Washing clothes, utensils • Generating electricity • Bathing
• Habitat for various organisms etc.
Q2. What is waste water?
Ans. The dirty water which contains various impurities like dust, polythene bags, Vegetable peels, kitchen waste, oil & water that goes down the drains from sinks, showers, toilets, laundries etc is waste water. Waste water can not be used further.
Q3. What are the various causes of water pollution?
Ans. water is polluted by various factors like:
• Bathing of cattle in river bodies.
• Washing of clothes & utensils by people in rivers.
• Discharging wastes from factories, industries in nearby river bodies & ponds.
Q4. When is World Water Day celebrated?
Ans. World Water Day is celebrated on 22nd March.
Q5. What is sewage?
Ans. The waste water that is being generated at homes, industries, agricultural activities, human activities etc is called sewage.
Q6. What do you mean by “sewage treatment”?
Ans. Sewage treatment is a process of removing pollutants before it enters a water body or is refused.
Q7. Explain why is it harmful to discharge untreated sewage into Water bodies?
Ans. It is harmful to discharge the untreated sewage into the water bodies as it contains harmful substances. Most of it is water which has dissolved & suspended impurities which may pollute the water bodies & also harm the aquatic plants & animals.
Q8. What is sludge? How is it treated?

Ans. Solid Faecal matter which is generated after the water treatment plant is known as sludge.
The sludge is transferred to a separate tank where it is decomposed by anaerobic bacteria. The biogas produced can be used as a fuel & the dried sludge is used as manure for replenishing the nutrients of the soil.
Q9. Untreated human excreta are a health hazard. Justify the statement.
Ans. Untreated human excreta is a health hazard as it may cause water pollution. It pollutes both Surface water as well as ground water. Since ground water is a source of water for wells, tube wells etc therefore it leads to waterborne diseases like cholera, jaundice, typhoid etc.
Q10. Name any two chemicals that are used to disinfect water.
Ans. Chlorine & Ozone.
Q11. What do you understand by the term “sewerage”?
Ans. Sewerage is like a transport system that carries sewage from the point where it is being generated to the point of disposal i.e. treatment plant.
Q12. List five ways to control sewage generation .
Ans. Ways to control sewage generation are:
• Leakage in sewer lines should be checked & repaired regularly.
• Do not defecate, spit or scatter litter in public places.
• Used tea leaves, solid food remains, toys, towels etc should not be thrown in water pipe because these materials may choke the pipe.
Q13. Suggest alternative arrangement for sewage disposal.
Ans. To improve sanitation, low cost onsite sanitation sewage disposals are being made. For example: septic tanks, composting pits etc.
Q14.Why are bacteria used in sewage treatment plants?
Ans. The bacteria decompose the suspended waste that includes domestic wastes & other undesirable organic substances present in the clarified water.
The activity of bacteria produces decomposed organic material from which solid waste is separated. This solid waste is used as manure.
Q15.Discuss the various steps involved in water treatment plant.
Ans. There are various steps involved in the water treatment plant which involves physical, chemical & biological processes:
• Waste water is passed through bar screens to remove big objects like cans, sticks, rags etc.
• The liquid material is then passed through sedimentation tank where solid wastelike faecal matter, sand, grit settles down.• This solid matter is then removed with the help of a scrapper. This is the sludge.
• A skimmer removes the floatable solids like oil, grease etc.
• The clear water so obtained is called clarified water.
• Air is pumped into clarified water to help aerobic bacteria to grow. The bacteriathen consume the unwanted matter still present in clarified water.
• The suspended microbes settle at the bottom & the water is removed from the top.
Q16. What are the harmful effects of sewerage?
Ans. Accumulation of sewerage leads to:
a) spread of various diseases.
b) Water pollution.
c) Discharge of sewerage in water bodies leads to excessive growth of algae .
Q17.What is the function of bar screens in waste water treatment plant?
Ans. The bar screen sremove the large objects like rags, sticks, cans, plastis packets etc.from the sewage.
Q18.What is a manhole?Why are manholes made?
Ans. A manhole is a covered vertival hole in the ground, pavement or road above the underground sewer pipeline.
If there is any leakage or blockage in the underground sewer pipeline, the sanitary worker can go down, up to these sewer pipelines for cleaning or any repair.
Q19.Why should not chemicals be released in the drain?
Ans.Chemicals like paints, solvents, insecticides should not be thrown down the drain as it may kill the useful microbes that help to decompose the waster present in the sewage & purify water.
Q20.Why should used tea leaves, solid food remains, etc not be released in the drains?
Ans. Used tea leaves , solid food remains etc should not be thrown down the drain as they may c hoke the drain.

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