NEET Biology Microbes In Sewage Treatment Multiple Choice Question And Answers

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Biology MCQ For NEET With Answers Microbes In Sewage Treatment

Question 1. Primary treatment involves

  1. Physical removal of large and small particles from sewage
  2. Biological removal of large and small particles from sewage
  3. Chemical removal of large and small particles from sewage
  4. Both (2) and (3)

Answer: 1. Physical removal of large and small particles from sewage

Primary treatment of sewage is the process of removal of small and large, floating and suspended solids from sewage through filtration and sedimentation.

Question 2. In the primary treatment of sewage, the floating debris is removed by passing the sewage through wire mesh screens. This is known as

  1. Sequential filtration
  2. Sedimentation
  3. Aeration
  4. Evaporation

Answer: 1. Sequential filtration

In the primary treatment of sewage, the floating debris is removed by sequential filtration by passing through wire mesh.

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Question 3. Which of the following in sewage treatment removes suspended solids?

  1. Tertiary treatment
  2. Secondary treatment
  3. Primary treatment
  4. Sludge treatment

Answer: 3. Primary treatment

Primary treatment of sewage is the process of removal of small and large, floating and suspended solids from sewage through filtration and sedimentation.

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NEET Biology Microbes In Sewage Treatment Multiple Choice Question And Answers

Question 4. Sand and small pebbles are removed in

  1. Grit chambers
  2. Sludge digesters
  3. Aeration tank
  4. Effluent tank

Answer: 1. Grit chambers.

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  • The wastewater is passed through a screen to remove rags and large debris. The screening system washes and dewaters the debris before discharging it into a garbage cane.
  • The screened wastewater then flows to an aerated grit chamber that facilitates the sedimentation of heavier inorganic materials, such as sand and grit, by reducing the velocity of the wastewater.
  • The grit chamber is aerated to increase the dissolved oxygen content of the wastewater, which supports the aerobic biological process used later in the treatment system.
  • The material collected at the bottom of the grit vessel is removed by an auger and mixed with biosolids generated during the treatment process. Thus, sand and small pebbles are removed in grit chambers.

Question 5. Sewage water can be purified for recycling with the action of

  1. Aquatic plants
  2. Penicillin
  3. Microorganisms
  4. Fishes

Answer: 3. Microorganisms

Microbes or microorganisms play an essential role in sewage treatment plants by decomposing organic matter both aerobically and anaerobically. They help to purify and recycle the sewage water.

Question 6. Sewage water cannot be discharged directly into rivers because

  1. It contains a high level of organic matter
  2. It contains pathogenic microbes
  3. It may destroy the flora and fauna of the river
  4. All of the above

Answer: 4. All of the above

  • Sewage water cannot be discharged directly into rivers because sewage is a liquid containing organic wastes from households, industrial and agricultural activities discharged into water. It contains harmful substances and disease-causing microbes.
  • All these components can adversely affect the flora and fauna of water bodies. Therefore, it is dangerous to release untreated sewage into the water.

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Question 7. Secondary sewage treatment is basically

  1. A chemical process
  2. A physical process
  3. A mechanical process
  4. A biological process

Answer: 4. A biological process

Secondary treatment of the liquid effluent from the primary settling tank is purely a biological treatment, involving microbial activity.

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Question 8. In the biological treatment of sewage, the mass of bacteria is held together by fungal filaments and forms a mesh-like structure called

  1. Activated sludge
  2. Aerobic process
  3. Flocs
  4. Anaerobic sludge

Answer: 3. Flocs

  • Useful aerobic microbes grow rapidly and form flocs. Flocs are masses of bacteria associated with fungal filaments to form mesh-like structures.
  • The growing microbes consume organic matter and thus, reduce the biochemical oxygen demand (bod).

Question 9. In sewage treatment, bacterial flocs are allowed to sediment in a settling tank. This sediment is called as

  1. Activated sludge
  2. Primary sludge
  3. Anaerobic sludge
  4. Secondary sludge

Answer: 1. Activated sludge

In sewage treatment, when the biochemical oxygen demand (body) of sewage has reduced, the effluent is passed into the settling tank. Since the sludge consists of active biological material such as flocs, it is referred to as activated sludge.

Question 10. Bod of wastewater is estimated by measuring the amount of

  1. Carbon dioxide present
  2. Biodegradable organic matter
  3. Oxygen evolution
  4. Oxygen consumption

Answer: 4. Oxygen consumption

Biochemical oxygen demand (bod) measures the amount of organic matter in water by measuring the rate of oxygen uptake (i.e. Oxygen consumption) by microbes.

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Question 11. Bod is

  1. Biochemical oxygen demand
  2. Biological oxygen deficit
  3. Biochemical oxygen deficit
  4. Botanical oxygen demand

Answer: 1. Biochemical oxygen demand

Biochemical oxygen demand (bod) measures the amount of organic matter in water by measuring the rate of oxygen uptake (i.e. Oxygen consumption) by microbes.

Question 12. The purpose of biological treatment of wastewater is to

  1. Reduce bod
  2. Increase bod
  3. Reduce sedimentation
  4. Increase sedimentation

Answer: 1. Reduce bod

The growing microbes consume organic matter and thus reduce the biochemical oxygen demand (bod).

13. Good drinking water should have a body level at

  1. 9-12 Ppm
  2. 1-2 Ppm
  3. 15-20 Ppm
  4. 10.2 ppm

Answer: 2. 1-2 Ppm

  • A body level of 1-2 ppm is considered very good. There will not be much organic waste present in the water supply. A water supply with a body level of 3-5 ppm is considered moderately clean.
  • In water with a body level of 6-9 ppm, the water is considered somewhat polluted because there is usually organic matter present and bacteria are decomposing this waste. At body levels of 100 ppm or greater, the water supply is considered very polluted with organic waste.

14. Consider the following statements.

  1. Biochemical oxygen demand (bod) represents the amount of dissolved oxygen that would be consumed if all the organic matter in 1 l of water were oxidised by microorganisms.
  2. The low value of the body means the water is either normal or less polluted by organic matter.
  3. The high value of the body means the water is highly polluted by organic matter.

Choose the option containing

Correct statements.

  1. 1 And 2
  2. 1 And 3
  3. 2 And 3
  4. 1, 2 And 3

Answer: 4. 1, 2 And 3

  • All given statements are correct. Bod refers to the amount of oxygen consumed if all the organic matter in one litre of water is oxidised by bacteria. A body level of 1-2 ppm is considered very good.
  • There will not be much organic waste present in the water supply. A water supply with a body level of 3-5 ppm is considered moderately clean.
  • In water with a body level of 6-9 ppm, the water is considered somewhat polluted because there is usually organic matter present and bacteria are decomposing this waste. At body levels of 100 ppm or greater, the water supply is considered very polluted with organic waste.

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15. Which of the following plan has been initiated by the Ministry of Environment and Forests to protect rivers from water pollution?

  1. Ganga action plan
  2. Yamuna action plan
  3. Both (1) and (2)
  4. Neither (1) nor (2)

Answer: 3. Both (1) and (2)

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In order to protect the major rivers of India from sewage pollution, the Ministry of Environment and Forests has initiated the development of sewage treatment plants under the national river conservation authority, Examples: Ganga action plan (gap), yamuna action plan, Sutlej Action plan, gomti action plan, etc.

Question 16. When a huge amount of sewage is dumped into a river, the body will

  1. Increase
  2. Remain unchanged
  3. Slightly decrease
  4. Decrease

Answer: 1. Increase

  • When huge amounts and sewage are dumped into a river, the body will increase. Untreated sewage contains large amounts of organic matter.
  • Bod is the amount of oxygen required to decompose the organic matter present in a water body. The higher the body, the more polluted the water.

Question 17. Given below is the flowchart of sewage treatment. Identify a, b, c, d and e and select the correct option.

NEET Biology Microbes in Sewage Treatment MCQs Primary sludge

  1. A– secondary treatment, b–microbial digestion, c–high bod, d–activated sludge, e–aerobic sludge digesters
  2. A–aerobic treatment, b–mechanical agitation, c–low bod, d–deactivated sludge, e–aerobic sludge digesters
  3. A–small aeration tank, b–microbial digestion, c–low bod, d–activated sludge, e–anaerobic sludge digesters
  4. A–secondary treatment, b–mechanical agitation, c–reduced body, d–activated sludge, e–anaerobic sludge digesters

Answer: 4. –Secondary treatment, b–mechanical agitation, c–reduced body, d–activated sludge, e–anaerobic sludge digesters

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Question 18. Microbes are used in

  1. Primary treatment of sewage
  2. Secondary treatment of sewage
  3. Anaerobic sludge digesters
  4. Production of biogas

Choose the correct option.

  1. 1, 2 And 3
  2. 1, 3 And 4
  3. 2, 3 And 4
  4. 1, 2, 3 And 4

Answer: 3. 2, 3 And 4

  • All listed processes involve the use of microbes except primary treatment of sewage because primary treatment is the physical removal of large and small particles from sewage.
  • Secondary treatment of the liquid effluent from the primary settling tank is purely a biological treatment involving microbial activity.
  • In the anaerobic sludge digesters, heterotrophic microbes anaerobically digest bacteria and fungi in sludge producing a mixture of gases such as methane, hydrogen sulphide and CO2 which form the biogas.

Question 19. During secondary treatment,

  1. Primary effluent is continuously agitated in the aeration tank
  2. There is vigorous growth of useful aerobic microbes into flocs
  3. Reduction in body level
  4. All of the above

Answer: 4. All of the above

  • In the secondary treatment, the effluent is present in large effluent tanks. Air is constantly pumped and the effluent is agitated. This results in rapid growth of microbial flocs which are associations of bacteria and fungi.
  • These flocs feed on the organic matter present in the effluent thereby, reducing the body. On significant reduction of body, the effluent is then passed to the settling tanks.

Question 20. What gases are produced in anaerobic sludge digesters?

  1. Methane and co2 only
  2. Methane, hydrogen sulphide and
  3. Methane, hydrogen sulphide and o2
  4. Hydrogen sulphide and co2

Answer: 2. Methane, hydrogen sulphide and

In an anaerobic sludge digester, due to the activity of anaerobic bacteria like methanogenic and sulphur bacteria, gases like ch4, h s2 and co2 are produced.

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Question 21. What will happen to the activated sludge floc if oxygen is reduced?

  1. It will slow down the rate of degradation of organic matter
  2. The centre of flocs will become anoxic resulting in death
  3. Flocs would increase in size as anaerobic bacteria would grow around flocs
  4. Protozoa would grow in a large number

Answer: 3. Flocs would increase in size as anaerobic bacteria would grow around flocs

Without oxygen, the microbes cannot survive. If O2 is reduced, the centre of the flocs will become anoxic, which would cause death.

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Question 22. Choose the incorrect statement about secondary sewage treatment.

  1. In the settling tank, the bacterial flocs settle and the sediment is called activated sludge
  2. A small part of the sludge is used as an inoculum. The remaining part is passed into anaerobic sludge digesters
  3. On anaerobic digestion of bacteria and fungi, a mixture of gases such as carbon dioxide, nitrogen and carbon monoxide are produced
  4. None of the above

Answer: 3. On anaerobic digestion of bacteria and fungi, a mixture of gases such as carbon dioxide, nitrogen and carbon monoxide are produced

  • The statement in the option is incorrect and can be corrected as methane, hydrogen sulphide and CO2 are the main gases produced in the digesters by the anaerobic digestion by heterotrophic bacteria and fungi.
  • Carbon monoxide is not produced during this process. Rest statements are correct about secondary sewage treatment.

Question 23. Which of the following is put into an anaerobic sludge digester for further sewage treatment?

  1. Floating debris
  2. The effluent of primary treatment
  3. Activated sludge
  4. Primary sludge

Answer: 3. Activated sludge

Activated sludge is put into an anaerobic sludge digester for further sewage treatment. It contains biological flocs that contain bacteria and fungi for further digestion of organic waste.

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