Biology Questions and Answers – Microbes in Sewage Treatment

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This set of Biology Multiple Choice Questions & Answers (MCQs) focuses on “Microbes in Sewage Treatment”.

1. What is the major component of waste-water?
a) Pure water
b) Human excreta
c) Sand
d) Clay
View Answer

Answer: b
Explanation: A major component of this waste-water is human excreta. This municipal waste-water is also called as sewage. It contains a large amount of organic matter and microbes. Many of which are pathogenic.
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2. What is the full form of STPs?
a) Sexually transmitted problems
b) Sewage treatment plants
c) Serum tissue plasminogen
d) Sebaceous tissue plasminogen
View Answer

Answer: b
Explanation: STP stands for sewage treatment plants. Before the disposal of waste-water into the natural water bodies, sewage is treated in STPs to make it less polluting.

3. In how many stages the treatment of waste-water in STPs is carried out?
a) One
b) Two
c) Three
d) Four
View Answer

Answer: b
Explanation: The treatment of waste-water in STPs is carried out in two stages namely primary treatment and secondary treatment. Treatment of waste-water is done by the heterotrophic microbes naturally present in the sewage.
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4. Primary treatment involves filtration and distillation.
a) False
b) True
View Answer

Answer: a
Explanation: Primary treatment involves the basic removal of particles- large and small-from the sewage through filtration and sedimentation. These particles are removed further in various stages.

5. Which of the following is not correct regarding the primary treatment of waste-water?
a) Initially floating debris is removed by distillation
b) Grit and pebbles are removed by sedimentation
c) Solids that settle form the primary sludge
d) Supernatant forms the effluent
View Answer

Answer: a
Explanation: In primary treatment, initially floating debris is removed by sequential filtration. Then grit and small pebbles are removed by sedimentation. All solids that settle form the primary sludge while the supernatant forms the effluent.
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6. The effluent from the primary settling tank is taken for secondary treatment.
a) True
b) False
View Answer

Answer: a
Explanation: The effluent from the primary settling tank is taken for secondary treatment. The primary effluent is then passed into large aeration tanks where it is constantly agitated mechanically and the air is pumped into it.

7. What are flocs?
a) Masses of fungi
b) Masses of algae
c) Masses of animals
d) Masses of bacteria
View Answer

Answer: d
Explanation: The constant agitation of primary effluent allows vigorous growth of useful aerobic microbes into flocs which are the masses of bacteria associated with fungal filaments to form mesh-like structures.
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8. What is the full form of BOD?
a) Biochemical oxygen demand
b) Bionatal oxygen demand
c) Biological disease
d) Biological oxygen deficiency
View Answer

Answer: a
Explanation: BOD refers to the Biochemical oxygen demand. It is the amount of oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria.

9. Which of the following statements is not true regarding BOD?
a) Sewage water is treated until the BOD is reduced.
b) BOD is a measure of organic matter present in the water
c) Greater the BOD, lesser is the polluting potential of water
d) BOD measures the rate of uptake of oxygen
View Answer

Answer: c
Explanation: The sewage water is treated until the BOD is reduced. The BOD test measures the rate of uptake of oxygen by micro-organisms in a sample of water and thus, BOD is indirectly a measure of the organic matter present in the water. The greater the BOD of waste-water more is its polluting potential.
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10. What is activated sludge?
a) Distilled bacteria
b) Fermented bacteria
c) Sediment bacterial flocs
d) Fungi
View Answer

Answer: c
Explanation: Activated sludge are the sediment bacterial flocs which were present in the effluent. When the biochemical oxygen demand of sewage water is reduced significantly, the effluent is then passed into a settling tank where the bacterial flocs are allowed to sediment.

11. Where is the major part of sludge pumped in secondary treatment?
a) Aeration tank
b) Anaerobic sludge digesters
c) Rivers
d) Drains
View Answer

Answer: b
Explanation: In the secondary treatment, a small part of the activated sludge is pumped back into the aeration tank to serve as inoculum. The remaining major part of the sludge is pumped into large anaerobic sludge digesters.

12. How many gallons of waste-water is treated before being released into the natural water-bodies?
a) Millions
b) Billions
c) Trillions
d) Quadrillion
View Answer

Answer: a
Explanation: Millions of gallons of waste water is treated in various sewage plants where microbes play a major role in decomposing the waste. This methodology has been practised for a century, in almost all parts of the world.

13. What is the full form of GAP?
a) Ganglion active potential
b) Ganga active plan
c) Ganglion action potential
d) Ganga Action Plan
View Answer

Answer: d
Explanation: The Ministry of Environment and Forests has initiated Ganga Action Plan (GAP) and Yamuna Action Plan (YAP) to save these major rivers of our country from pollution.

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