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Test: Zones of Pollution in River - Civil Engineering (CE) MCQ


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8 Questions MCQ Test Environmental Engineering - Test: Zones of Pollution in River

Test: Zones of Pollution in River for Civil Engineering (CE) 2024 is part of Environmental Engineering preparation. The Test: Zones of Pollution in River questions and answers have been prepared according to the Civil Engineering (CE) exam syllabus.The Test: Zones of Pollution in River MCQs are made for Civil Engineering (CE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Zones of Pollution in River below.
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Test: Zones of Pollution in River - Question 1

In which pollution zone of the river, growth of algae reappear?

Detailed Solution for Test: Zones of Pollution in River - Question 1

The growth of algae reappear in the zone of recovery.The growth of fungi decreases.

Test: Zones of Pollution in River - Question 2

The pollution zones in the river are divided into how many types?

Detailed Solution for Test: Zones of Pollution in River - Question 2

There are 4 types of pollution zones in the river, namely zone of degradation, zone of active decomposition, zone of recovery and zone of clear water.

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Test: Zones of Pollution in River - Question 3

Which is the third zone of pollution in the river?

Detailed Solution for Test: Zones of Pollution in River - Question 3

The zone of recovery is the third zone of pollution in the river where river tries to recover the polluted water through the self purification process.

Test: Zones of Pollution in River - Question 4

In which pollution zone of the river, the dissolved oxygen reduced to 0?

Detailed Solution for Test: Zones of Pollution in River - Question 4

The dissolved oxygen, reduced to 0 in the zone of active decomposition. The water is highly polluted in this zone.

Test: Zones of Pollution in River - Question 5

The fishes were present in the river, but algaes were not able to survive. What is the zone of pollution of the river?

Detailed Solution for Test: Zones of Pollution in River - Question 5

It is the zone of degradation as dissolved oxygen has reduced to 40%. The fishes will die when dissolved oxygen is less than 4ppm.

Test: Zones of Pollution in River - Question 6

In which pollution zone of the river, water retains its original dissolved oxygen concentration?

Detailed Solution for Test: Zones of Pollution in River - Question 6

The water retains its original dissolved oxygen concentration in the zone of clean water. It has a clear appearance.

Test: Zones of Pollution in River - Question 7

The following zones are formed in a polluted river under the self – purification process

  • zone of clear water
  • zone of active decomposition
  • zone of recovery
  • zone of pollution

The correct sequence in which these zones occur progressively downstream in a polluted river is:

Detailed Solution for Test: Zones of Pollution in River - Question 7


Correct order is
Zone A – Zone of clear water
Zone B – Zone of Degradation
Zone C – Zone of Active decomposition
Zone D – Zone of Recovery
Zone E – Zone of clear water

ZONES OF POLLUTION: 
A polluted stream undergoing self-purification presents the following four distinct zones of pollution.

  • ZONES OF DEGRADATION:
    • This usually occurs below the output sewer when discharging its contents into the stream. The zone is characterized by water becoming dark and turbid with the formation of sludge deposits on the bottom.
    • Dissolved oxygen gets reduced to 40%.
  • ZONES OF ACTIVE DECOMPOSITION: 
    • This is marked by heavy pollution. It is characterized by the absence of dissolved oxygen; water is grayish and darker with active anaerobic organic decomposition accompanying and with the evolution of methane (CH4), Hydrogen sulphide (H2S), Carbon dioxide (CO2), and Nitrogen (N2), bubbling to the surface with masses of sludge forming black scum.
    • Fish life is practically absent, fungi and bacteria disappear. As the organic decomposition slackens, reaction sets in, and D.O. again rises to its original level (i.e. 40%).
  • ZONE OF RECOVERY: 
    • In this zone, the stream tries to recover its former appearance. Most of the organic matter has been settled as sludge, B.O.D. falls and the D.O. content rises above 40% microscopic aquatic life reappears.
    • Water becomes clearer, fungi decrease and algae reappear. Mineralization is active and products such as nitrates, sulphates, and carbonates are formed.
  • CLEAR WATER ZONE: 
    • In this, the natural stream condition is restored, the D.O. is higher than the BOD. Oxygen balance is attained and recovery is said to be complete. Water becomes attractive in appearance. Some pathogenic organisms may, however, be present.
Test: Zones of Pollution in River - Question 8

In which pollution zone of the river, the concentration of D.O reduced to 40%?

Detailed Solution for Test: Zones of Pollution in River - Question 8

In the zone of active decomposition, the concentration of D.O reduced to 40%. It is the second zone of pollution in the river.

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