Engineering Questions with Answers - Multiple Choice Questions
Environmental Engineering MCQ’s – Grit Chambers, Tanks and Vacuum Floatation
1 - Question
The unit of dynamic viscosity is ____________
a) Metre2/Sec
b) Metre/Sec
c) Pa * Sec
d) Dimensionless
View Answer
Answer: c
Explanation: The dynamic viscosity is the ratio of shear stress to velocity gradient. Its unit is Pa * Sec.
2 - Question
Which of the following has minimum detention period?
a) Grit chamber
b) Sedimentation tank
c) Oxidation ditch
d) Oxidation pond
View Answer
Answer: a
Explanation: Grit chamber has a minimum detention period with a value of 40-60 seconds.
3 - Question
The relation between dynamic and kinematic viscosity is given by ____________
a) Dynamic viscosity = Kinematic viscosity * Density of water
b) Kinematic viscosity = Dynamic viscosity + Density of water
c) Dynamic viscosity = Kinematic viscosity * Density of water
d) Dynamic viscosity = Kinematic viscosity / Density of water
View Answer
Answer: c
Explanation: μ = v * ρ, μ = dynamic viscosity, v = kinematic viscosity and ρ = density of water.
4 - Question
The dimension formula of dynamic viscosity is ____________
a) ML-1T
b) ML-1T-1
c) ML-2T-2
d) ML-1T-3
View Answer
Answer: b
Explanation: The dimension formula of dynamic viscosity is ML-1T-1 and it can be measured in kg m-1 s-1.
5 - Question
The dimension formula of kinematic viscosity is ____________
a) L-1T
b) ML-1T-1
c) ML-2T-2
d) L2T-1
View Answer
Answer: d
Explanation: The dimension formula of kinematic viscosity = ML-1T-1 / ML-3 = L2 T-1.
6 - Question
The coefficient of drag for a transition settling is ____________
a) CD = 18.5/R0.6
b) CD = 24/R
c) CD = 8.5/R0.6
d) CD = R/24
View Answer
Answer: a
Explanation: When Reynolds number ‘R’ lies between 1 and 1000, the coefficient of drag CD is given by CD = 18.5/R0.6.
7 - Question
In which of the following, large impurities are attached with air bubbles to remove it from the wastewater?
a) Sludge digestion tank
b) Primary sedimentation
c) Vacuum floatation
d) Oxidation pond
View Answer
Answer: c
Explanation: In skimming tanks, large impurities are attached with air bubbles to decrease its density, they float in sewage and are finally removed by skimming troughs.
8 - Question
Which of the following has a minimum detention period?
a) Sludge digestion tank
b) Primary sedimentation
c) Skimming tank
d) Oxidation pond
View Answer
Answer: c
Explanation: The skimming tank has a minimum detention period with a value of 3 minutes.
9 - Question
The design velocity of flow of a detritus tank is ____________
a) 1m/Sec
b) 1.2m/Sec
c) 0.9m/Sec
d) 0.5m/Sec
View Answer
Answer: c
Explanation: The detritus tanks are able to remove grit and sand particles by having a design velocity of 0.9m/Sec.
10 - Question
Which of the following device is used for the removal of oil and grease?
a) Skimming tank
b) Grit chambers
c) Tube settlers
d) Flocculator
View Answer
Answer: a
Explanation: The skimming tank is used after the grit chamber to remove oil and grease from the sewage.
11 - Question
The detention period of detritus tank is ____________
a) 40 seconds
b) 1 minute
c) 3 minute
d) 1 hour
View Answer
Answer: c
Explanation: The detention period of detritus tank is 3 minutes. It is used to remove the grit present in the wastewater.
12 - Question
A pressure difference of _____________ is applied to the vacuum floatation method to remove impurities from sewage.
a) 0.5 atm
b) 1 atm
c) 1.5 atm
d) 2 atm
View Answer
Answer: b
Explanation: In the vacuum floatation method, pressure of 1 atm is applied in sewage followed by the vacuum that creates a pressure difference of 1 atm, resulting in the formation of bubbles that helps in the removal of large impurities in sewage.