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Q. No.In the secondary treatment or biological treatment of sewage water, the primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and the air is pumped into it. This allows:
1. vigorous growth of useful aerobic microbes into flocs
2. the decrease in the number of aerobes in the water
3. rapid increase in the count of methanogens
4. a dramatic decrease in the anaerobic methanogens
Subtopic: Â Microbes in Sewage Treatment |
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During secondary treatment of sewage water:
| I: | vigorous growth of useful aerobic microbes into flocs is allowed |
| II: | aerobic microbes consume the major part of the organic matter in the effluent. |
| III: | the BOD of the water sample gets significantly increased |
| 1. | Only I and II are correct |
| 2. | Only I is correct |
| 3. | Only II and III are correct |
| 4. | I, II and III are correct |
Subtopic: Â Microbes in Sewage Treatment |
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From NCERT
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A small part of the activated sludge in sewage treatment plant is:
| 1. | pumped back into the aeration tank to serve as the inoculum. |
| 2. | added to the fresh water rivers. |
| 3. | is used to produce probiotics. |
| 4. | pumped into large tanks called anaerobic sludge digesters. |
Subtopic: Â Microbes in Sewage Treatment |
 92%
From NCERT
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Consider the given tow statements:
| Statement I: | BOD is a measure of the organic matter present in the water. |
| Statement II: | BOD refers to the amount of the oxygen that would be consumed if all the organic matter in one litre of water were oxidised by bacteria. |
| 1. | Statement I is correct; Statement II is incorrect |
| 2. | Statement I is incorrect; Statement II is incorrect |
| 3. | Statement I is correct; Statement II is correct |
| 4. | Statement I is incorrect; Statement II is correct |
Subtopic: Â Microbes in Sewage Treatment |
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From NCERT
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If oxygen availability to activated sludge flocs in a sewage treatment plant is reduced:
| 1. | the rate of degradation of organic matter slows down |
| 2. | the center of flocs becomes anoxic, causing death of bacteria and eventually breakage of flocs. |
| 3. | the flocs would increase in size as anaerobic bacteria would grow around flocs. |
| 4. | Protozoa would grow in large numbers. |
Subtopic: Â Microbes in Sewage Treatment |
From NCERT
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Treatment of waste-water is done by the:
| 1. | heterotrophic microbes naturally present in the sewage. |
| 2. | photosynthetic autotrophic microbes naturally present in the sewage. |
| 3. | methanogens. |
| 4. | anaerobic microbes added as inoculum. |
Subtopic: Â Microbes in Sewage Treatment |
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From NCERT
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