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Page No 275:

Question A:

Solve the following crossword puzzle:
Figure

Across
2. Impurities present in waste water
3. It is the waste water
4. The leakage of petroleum oil into the sea

Down
1. This fuel is produced by anaerobic
2. It is a water-borne disease

Answer:

Page No 275:

Question B.1:

Waste water containing human excreta is known as
(a) sewage
(b) sewer
(c) sewerage
(d) none of these

Answer:

(a) sewage
Sewage is waste water containing human excreta.

Page No 275:

Question B.2:

Discharge of industrial waste is called
(a) sludge
(b) sewer
(c) sewerage
(d) effluent

Answer:

(d) effluent
The discharge of industrial waste is known as industrial effluent.

Page No 275:

Question B.3:

The light materials which float during waste water treatment is
(a) sludge
(b) scum
(c) biogas
(d) sewer

Answer:

(b) scum
The light material that floats during waste water treatment is known as scum.

Page No 275:

Question B.4:

Primary treatment is a
(a) mechanical process
(b) chemical process
(c) biological process
(d) none of these

Answer:

(a) mechanical process
Primary treatment is a mechanical process.

Page No 275:

Question B.5:

Sewage is often processed with the help of
(a) septic tank
(b) vermi-processing toilet
(c) both (a) and (b)
(d) none of these

Answer:

(c) both (a) and (b)
Both sceptic tanks and vermi-processing toilets are used for sewage processing.

Page No 275:

Question C:

Fill in the blanks:
1. The sewage is carried by big and small pipes called ................................ .
2. Dried sludge is used as a ................................ .
3. Tertiary treatment is a ................................ process.
4. ................................ consists of human excreta and other organic materials.
5. Drains get blocked by ................................ and ................................ .

Answer:

  1. The sewage is carried by big and small pipes called sewer.
  2. Dried sludge is used as a manure.
  3. Tertiary treatment is a chemical process.
  4. Domestic waste water consist of human excreta and other organic materials. 
  5. Drains get blocked by sanitary towels and solid food remains.



Page No 276:

Question 1:

Dams protect people from floods and also provide electricity. However, they also cause several people to lose their lands and homes because of the rise in the level of water behind the dam. Is building a dam desirable or dangerous? Find yourself.

Answer:

Dams can cause several problems such as submergence of lands and forests. Dams can also cause earthquakes, if they are built on seismic zones. However, carefully constructed dams allow water to be harnessed and electricity to be generated. So, building a dam is desirable but the consequences of faulty engineering must be carefully thought out.

Page No 276:

Question 2:

Does a faulty sewer line increase the risk of water-borne diseases? Explain.

Answer:

Yes, faulty sewer lines can potentially lead to the mixing of sewage with drinking water. They might also contaminate food. This can increase the likelihood of water-borne diseases such as cholera, dysentery etc.

Page No 276:

Question 3:

Why are Ganga and Yamuna rivers regarded as open sewers?

Answer:

The banks of the Ganga and the Yamuna are brimming with human population. A large amount of waste is generated by this population, such as sewage and human waste that are dumped into these rivers. Also, industrial waste is directly discharged into the Ganga and the Yamuna. Hindus float corpses in the Ganga since it is considered a holy river by them. Hence, the Ganga and the Yamuna are regarded as open sewers.

Page No 276:

Question D:

Match the items in Column A with the items in Column B:

Column A Column B
1. Tertiary treatment (a) Mechanical process
2. Sewers (b) Biological process
3. Waste water (c) Scum
4. Secondary treatment (d) Sewage
5. Primary treatment (e) Pipes carrying sewage
  (f) Chemical process

Answer:

Column A Column B
1. Tertiary treatment (f) Chemical process
2. Sewers (e) Pipes carrying sewage
3. Waste water (d) Sewage
4. Secondary treatment (b) Biological process
5. Primary treatment (a) Mechanical process
 

Page No 276:

Question E:

Write True (T) of False (F) against the following statements in the given brackets:
1. Primary treatment of waste water is a mechanical process. ( )
2. Scum is removed with a skimmer. ( )
3. Septic tank is an example of on-site sewage disposal system. ( )
4. Aeration of clarified water kills disease-causing microbes. ( )
5. Sewer pipes are made up of case iron. ( )

Answer:

1. True (T)

2. True (T)

3. True (T)

4. False (F)
Ozonisation or chlorination is used to kill disease-causing microbes.

5. True (T)



Page No 277:

Question A.1:

How will you define waste?

Answer:

Any material that has lost its value and cannot be used again is known as waste.

Page No 277:

Question A.2:

What is sewage?

Answer:

Water that contains contaminants or waste and is unfit for use is known as sewage.

Page No 277:

Question A.3:

What is scum?

Answer:

Scum is the light material that floats on the top during waste water treatment.

Page No 277:

Question A.4:

Why are bacterial used in sewage treatment plants?

Answer:

Bacteria are used in sewage treatment plants to decompose suspended waste and other undesirable organic substances.

Page No 277:

Question A.5:

What is the function of screens in a water treatment plant?

Answer:

Large rotating bar screens in sewage treatment plants help remove large objects such as rags, sticks, cans, plastics, napkins etc.

Page No 277:

Question A.6:

Name two inorganic impurities present in sewage.

Answer:

Nitrates and phosphates are two inorganic impurities present in sewage.

Page No 277:

Question A.7:

Name a chemical that is used to disinfect water.

Answer:

Chlorine can be used to disinfect water.



Page No 278:

Question B.1:

What is sludge and how do we use?

Answer:

During the primary treatment of sewage, after its passage through bar filters and a grit and sand tank, the liquid material is held in large sedimentation tanks. The solid waste then settles to the bottom of the tank, from where it is removed using a scrubber. This material at the bottom of the tank is known as sludge. Sludge can be used in the production of biogas.

Page No 278:

Question B.2:

Under what condition do we make spetic tanks?

Answer:

Septic tanks are common in areas where a sewerage system is not available or has not yet been constructed.

Page No 278:

Question B.3:

What problem do we face with open drainage?

Answer:

The limitations of open drainage are:

  1. Open drains can be easily blocked and then they might overflow.
  2. Overflowing sewage collects in pools and stagnates there. The stagnating pools of sewage are a breeding ground for mosquitoes and dangerous bacteria.
  3. Open drains lead to the spreading of bad odour in their surroundings.

Page No 278:

Question B.4:

What is an oil spill?

Answer:

An oil spill is the leakage of petroleum and oil into the sea, which causes pollution of the sea.

Page No 278:

Question B.5:

What are the main constituents of sewage? Give any two examples of each.

Answer:

The constituents of sewage are:

  1. Organic impurities: Example: human excreta and urine
  2. Inorganic impurities: Example: nitrates and phosphates
  3. Nutrients: Example: nitrogen and phosphorus
  4. Disease-causing microbes: Example: viruses and bacteria causing cholera, typhoid etc.

Page No 278:

Question B.6:

What is the difference between sewer and sewer and sewer system?

Answer:

Sewer Sewer system
A pipe made of PVC plastic or cast iron used to carry sewage is known as a sewer. A collection of many sewer pipes is known as a sewer system.

Page No 278:

Question B.7:

What is the function of a treatment plant?

Answer:

A sewage treatment plant performs the following functions:

  1. Sewage is treated in these plants and rendered harmless.
  2. Water generated by a sewage treatment plant can be used for fisheries, irrigation. etc.
  3. The sludge formed during the treatment of sewage can be used as manure, or it can be used for making biogas.

Page No 278:

Question C.1:

Why should butter and oil not be released in the drainage?

Answer:

Butter and oil can clog drains leading to an overflow of sewage. To avoid this, butter and oil must never be released in the drainage.

Page No 278:

Question C.2:

List four ways to control sewage generation.

Answer:

Sewage generation can be controlled by:

  1. Regularly checking and repairing sewage lines
  2. Using low capacity flushes to reduce the amount of flushed water
  3. Avoiding public defecating and spitting, and littering
  4. Planting eucalyptus trees around sewage plants to help absorb surplus water

Page No 278:

Question C.3:

Discuss the stages of waste water treatment process.

Answer:

The stages of waste water treatment process are as follows:
(a) Primary treatment: This stage is a mechanical process involving screening and settling of large particles from waste water using vertical bars and grit chambers. After screening, water is passed into sedimentation tanks.

(b) Secondary treatment: This stage is a biological process that involves the breakdown of the organic matter obtained from the primary treatment, with the help of bacteria, producing biogas. Water is sent into aeration tanks and air is blown through them to speed up the treatment of water.

(c) Tertiary treatment: This stage is a chemical process and the last stage in the treatment of water. Chemicals are added to remove phosphorous and nitrogen from water. Bacteria and other germs are killed by the addition of chlorine.

Page No 278:

Question C.4:

Why is it harmful to discharge untreated sewage into the rivers?

Answer:

Untreated sewage contains toxic waste that can kill aquatic plants and animals. Furthermore, untreated sewage can lead to an outbreak of diseases such as cholera, meningitis and typhoid.

Page No 278:

Question C.5:

What are vermi toilets?

Answer:

In a vermi toilet, earthworms are used to treat human excreta. Using very little water, this toilet converts human excrement into vermi cakes that can be used as manure.

Page No 278:

Question C.6:

List three good housekeeping practices.

Answer:

The following are three good housekeeping practices:

  1. Avoid the disposal of oil, butter, fats, plastics etc., down the drain to prevent drains from getting choked.
  2. Do not dispose of paint, chemicals or medicines down the drain as these materials can kill the microorganisms used for cleaning the sewage.
  3. Used tea leaves, sanitary pads, toys, solid foods etc., must not be disposed of down the drain.



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