Water Waste engg-4

Question No. 61

The sludge does not contain waste water from

(A) Bath rooms

(B) Wash basins

(C) Kitchen sinks

(D) Toilets

Answer: Option D

Question No. 62

In sewers the velocity of flow should not be

(A) More than the self-cleansing velocity

(B) Less than the self-cleansing velocity

(C) Less than 10 m/sec

(D) More than 20 m/sec

Answer: Option B

Question No. 63

Pick up the correct statement from the following:

(A) Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers

(B) 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river

(C) Solubility of oxygen in sewage is 95% of that of distilled water

(D) All the above

Answer: Option D

Question No. 64

In sewers the effect of scouring is more on

(A) Top side

(B) Bottom side

(C) Horizontal side

(D) All sides

Answer: Option B

Question No. 65

The rainfall at any place may be determined by

(A) Its intensity

(B) Its direction

(C) Its frequency

(D) All the above

Answer: Option D

Question No. 66

Pick up the correct statement from the following:

(A) The circular section of sewers provides maximum hydraulic mean depth

(B) The circular sewers are provided for separate sewerage system

(C) The circular sewers work efficiently if the sections run at least half full

(D) All the above

Answer: Option D

Question No. 67

Pick up the correct statement from the following:

(A) Rate of digestion of sludge is more at higher temperature

(B) Thermophilic organisms digest the sludge if the temperature ranges from 40° to 60°C

(C) Mesophilic organisms digest the sludge if the temperature is between 25° and 40°C

(D) All the above

Answer: Option D

Question No. 68

Sewer ventilating columns are generally placed at

(A) Distances 150 m to 300 m

(B) Upper ends of branch sewers

(C) Every change in the size of sewers

(D) All the above

Answer: Option D

Question No. 69

The sewer which resists sulphide corrosion, is

(A) Brick sewer

(B) Cast iron sewer

(C) R.C.C. sewer

(D) Lead sewer

Answer: Option D

Question No. 70

In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a

discharge Q, is

(A) Q/(B × D)

(B) Q/(L × D)

(C) Q/L

(D) Q/(B × L)

Answer: Option D

Question No. 71

The formula which accepts the value of rugosity coefficient n = 0.012 to be used in Manning's

formula, is given by

(A) Bazin

(B) Crimp and Bruges

(C) William-Hazen

(D) Kutter

Answer: Option B

Question No. 72

The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological

decomposition of sewage, is known

(A) Bio-Chemical Oxygen Demand (B.O.D.)

(B) Dissolved Oxygen (D.O.)

(C) Chemical Oxygen Demand (C.O.D.)

(D) None of these

Answer: Option B

Question No. 73

Water content of sewage is about

(A) 90 %

(B) 95 %

(C) 99 %

(D) 9.9 %

Answer: Option D

Question No. 74

Skimming tanks are

(A) Used to remove the grease and oil

(B) Those from which sludge is skimmed out

(C) Tanks provided with self-cleansing screens

(D) Improved version of grit chambers

Answer: Option A

Question No. 75

The most efficient cross-section of sewers in a combined sewerage system is

(A) Parabolic

(B) Circular

(C) Rectangular

(D) New egged

Answer: Option B

Question No. 76

The detention period for plain sedimentation water tanks, is usually

(A) 4 to 8 hours

(B) 8 to 16 hours

(C) 16 to 24 hours

(D) 24 to 36 hours

Answer: Option A

Question No. 77

The factor responsible for purification of sewage in river is

(A) Hydrology

(B) Dissolved oxygen in water

(C) Temperature

(D) All the above

Answer: Option D

Question No. 78

Hume steel pipes are

(A) Steel pipes

(B) Steel shell coated from inside with cement mortar

(C) Steel shell coated from outside with cement mortar

(D) Both (B) and (C)

Answer: Option D

Question No. 79

To maintain aerobic biological activity, the moisture content of the compost mass should be about

(A) 45 %

(B) 50 %

(C) 55 %

(D) 60 %

Answer: Option C