Waste Water Engineering Mcqs - Set 3

1)   If a 2% solution of sewage sample is incubated for 5 days at 20°C and the dissolved oxygen depletion was found to be 8 mg/l. The BOD of the sewage is_________________?

a. 100 mg/l
b. 200 mg/l
c. 300 mg/l
d. 400 mg/l
Answer  Explanation 

ANSWER: 400 mg/l

Explanation:
No explanation is available for this question!


2)   A well oxidized sewage contains nitrogen mainly as___________________?

a. Nitrates
b. Nitrites
c. Free ammonia
d. None of these
Answer  Explanation 

ANSWER: Nitrates

Explanation:
No explanation is available for this question!


3)   In a sludge tank, the gas mainly produced, is_________________?

a. Oxygen
b. Nitrogen
c. Hydrogen
d. Carbon dioxide
Answer  Explanation 

ANSWER: Carbon dioxide

Explanation:
No explanation is available for this question!


4)   are available in size Stoneware sewers________________?

a. 10 cm
b. 15 cm
c. 20 cm
d. All the above
Answer  Explanation 

ANSWER: All the above

Explanation:
No explanation is available for this question!


5)   In normal conditions, the period for sludge digestion, is_______________?

a. 10 days
b. 20 days
c. 30 days
d. 60 days
Answer  Explanation 

ANSWER: 30 days

Explanation:
No explanation is available for this question!


6)   In trickling filter, B.O.D. is reduced to___________________?

a. 30 to 40%
b. 40 to 60%
c. 60 to 80%
d. 80 to 90%
Answer  Explanation 

ANSWER: 60 to 80%

Explanation:
No explanation is available for this question!


7)   The grit chambers of sewage treatment plants, are generally cleaned after__________________?

a. 2 days
b. 7 days
c. 12 days
d. 14 days
Answer  Explanation 

ANSWER: 14 days

Explanation:
No explanation is available for this question!


8)   Maximum permissible velocity 1.5 m/sec, is adopted in drains_______________________?

a. With beds of rocks and gravels
b. Lined with stones
c. Both A. and B.
d. Neither A. nor B.
Answer  Explanation 

ANSWER: Both A. and B.

Explanation:
No explanation is available for this question!


9)   If the discharge of a sewer running half is 628 1.p.s., i = 0.001, and n = 0.010, the diameter of the sewer, is__________________?

a. 1.39 m
b. 1.49 m
c. 1.59 m
d. 1.69 m
Answer  Explanation 

ANSWER: 1.69 m

Explanation:
No explanation is available for this question!


10)   running partially full with central angle , For a circular sewer of diameter__________________?

a. d/D = ½ (1 – –
b. a/A
c. r/R = [1 –
d. All the above
Answer  Explanation 

ANSWER: All the above

Explanation:
No explanation is available for this question!


11)   In the activated sludge process__________________?

a. Aeration is continued till stability
b. Aeration is done with an admixture of previously aerated sludge
c. Sludge is activated by constant stirring
d. Water is removed by centrifugal action
Answer  Explanation 

ANSWER: Aeration is done with an admixture of previously aerated sludge

Explanation:
No explanation is available for this question!


12)   The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is__________________?

a. Vs = 418 (Gs – Gw) d [(3T + 70)/100]
b. Vs = 418 (Gs – Gw)d² [(3T + 70)/100]
c. Vs = 218 (Gs – Gw)d² [(3T + 70)/100]
d. Vs = 218 (Gs – Gw)d [(3T + 70)/100]
Answer  Explanation 

ANSWER: Vs = 418 (Gs – Gw)d² [(3T + 70)/100]

Explanation:
No explanation is available for this question!


13)   Inter-distance between ventilation columns in a sewer line is kept__________________?

a. 25 to 50 m
b. 50 m to 100 m
c. 100 m to 150 m
d. 150 m to 300 m
Answer  Explanation 

ANSWER: 150 m to 300 m

Explanation:
No explanation is available for this question!


14)   The intensity of rain is expressed in________________?

a. cm/minute
b. cm/hour
c. cm/day
d. None of these
Answer  Explanation 

ANSWER: cm/hour

Explanation:
No explanation is available for this question!


15)   Which one of the following part of human body withstands minimum radiation ?

a. Thyroid
b. Kidneys
c. Eyes
d. Ovaries/testis
Answer  Explanation 

ANSWER: Ovaries/testis

Explanation:
No explanation is available for this question!


16)   The bottom of the sewage inlet chamber of septic tanks, is provided an outward slope_________________?

a. 1 in 5
b. 1 in 10
c. 1 in 15
d. 1 in 20
Answer  Explanation 

ANSWER: 1 in 10

Explanation:
No explanation is available for this question!


17)   Primary treatment of sewage consists of removal of__________________?

a. Large suspended organic solids
b. Oil and grease
c. Sand and girt
d. Floating materials
Answer  Explanation 

ANSWER: Large suspended organic solids

Explanation:
No explanation is available for this question!


18)   Cement concrete sewers are only suitable if non-scouring velocity is between_________________?

a. 2.5 to 3.0 m/sec
b. 3.0 to 4.0 m/sec
c. 3.5 to 4.5 m/sec
d. 4.5 to 5.5 m/sec
Answer  Explanation 

ANSWER: 2.5 to 3.0 m/sec

Explanation:
No explanation is available for this question!


19)   The most widely used pump for lifting sewage is_________________?

a. Centrifugal pump
b. Reciprocating pump
c. Pneumatic ejector
d. Air pressure pump
Answer  Explanation 

ANSWER: Centrifugal pump

Explanation:
No explanation is available for this question!


20)   Pick up the correct statement from the following ?

a. Maximum daily flow = 2 times the average daily flow
b. Maximum daily flow = average daily flow
c. Sewers are designed for minimum permissible velocity at minimum flow
d. All the above
Answer  Explanation 

ANSWER: All the above

Explanation:
No explanation is available for this question!