Environmental Engineering MCQ Questions & Answers

61

The percentage of filtered water, which is used for backwashing in rapid sand filters, is about

A) 0.2 to 0.4 B) 0.4 to 1.0 C) 2 to 4 D) 5 to 7

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Answer & Solution

Answer: Option C

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62

The percentage of chlorine in fresh bleaching powder is about

A) 10 to 15 B) 20 to 25 C) 30 to 35 D) 40 to 50

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Answer & Solution

Answer: Option C

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63

For a country like India, where rainfall is mainly confined to one season, the suitable sewerage system will be

A) Separate system B) Combined system C) Partially combined system D) Partially separate system

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Answer & Solution

Answer: Option A

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64

Dissolved oxygen in streams is

A) Maximum at noon B) Minimum at noon C) Maximum at midnight D) Same throughout the day

Discuss

Answer & Solution

Answer: Option A

Solution:

The correct answer is Option A: Maximum at noon

Let's break down why:

* Dissolved Oxygen (DO): This refers to the amount of oxygen gas that is present in the water.

* Photosynthesis: Aquatic plants (like algae) and phytoplankton in streams perform photosynthesis. This process uses sunlight to convert carbon dioxide and water into glucose (food) and, importantly, oxygen. This oxygen is released into the water, increasing the DO.

* Sunlight and Photosynthesis: Photosynthesis is dependent on sunlight.

* Noon: Around noon, sunlight is typically at its strongest intensity.

* Therefore, maximum photosynthesis occurs around noon, leading to a maximum level of dissolved oxygen in the stream.

* Midnight: At midnight, there is no sunlight, so photosynthesis stops. Respiration by aquatic organisms (which *consumes* oxygen) continues. Therefore, DO is typically *lowest* at night.

* So, the dissolved oxygen is not the same throughout the day.

65

If the time of concentration is 9 minutes, then the intensity of rainfall according to British Ministry of Health formula will be

A) 4 mm/hr B) 10 mm/hr C) 20 mm/hr D) 40 mm/hr

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Answer & Solution

Answer: Option D

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66

For normal sludge, the value of sludge index for Indian conditions is

A) 0 to 50 B) 50 to 150 C) 150 to 350 D) 350 to 500

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Answer & Solution

Answer: Option C

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67

The most common cause of acidity in water is

A) Carbon dioxide B) Oxygen C) Hydrogen D) Nitrogen

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Answer & Solution

Answer: Option A

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68

The length of rectangular sedimentation tank should not be more than
(Where ‘B’ is the width of the tank)

A) B B) 2B C) 4B D) 8B

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Answer & Solution

Answer: Option C

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69

Septic tank is a
(i) Settling tank
(ii) Digestion tank
(iii) Aeration tank

A) Only (i) B) (i) and (ii) C) (i) and (iii) D) Only (iii)

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Answer & Solution

Answer: Option B

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70

Double filtration is used

A) To increase the filtration slow sand filters capacity of B) To increase the filtration rapid sand filters capacity of C) For isolated buildings like pools, hotels etc swimming D) All of the above

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Answer & Solution

Answer: Option A

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Environmental Engineering MCQ Questions & Answers | Civil Engineering