This set of Environmental Engineering MCQs focuses on “Grit Chambers, Tanks and Vacuum Floatation”.
1. The unit of dynamic viscosity is ____________
a) Metre2/Sec
b) Metre/Sec
c) Pa * Sec
d) Dimensionless
View Answer
Explanation: The dynamic viscosity is the ratio of shear stress to velocity gradient. Its unit is Pa * Sec.
2. Which of the following has minimum detention period?
a) Grit chamber
b) Sedimentation tank
c) Oxidation ditch
d) Oxidation pond
View Answer
Explanation: Grit chamber has a minimum detention period with a value of 40-60 seconds.
3. 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
Explanation: μ = v * ρ, μ = dynamic viscosity, v = kinematic viscosity and ρ = density of water.
4. The dimension formula of dynamic viscosity is ____________
a) ML-1T
b) ML-1T-1
c) ML-2T-2
d) ML-1T-3
View Answer
Explanation: The dimension formula of dynamic viscosity is ML-1T-1 and it can be measured in kg m-1 s-1.
5. The dimension formula of kinematic viscosity is ____________
a) L-1T
b) ML-1T-1
c) ML-2T-2
d) L2T-1
View Answer
Explanation: The dimension formula of kinematic viscosity = ML-1T-1 / ML-3 = L2 T-1.
6. 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
Explanation: When Reynolds number ‘R’ lies between 1 and 1000, the coefficient of drag CD is given by CD = 18.5/R0.6.
7. 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
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. Which of the following has a minimum detention period?
a) Sludge digestion tank
b) Primary sedimentation
c) Skimming tank
d) Oxidation pond
View Answer
Explanation: The skimming tank has a minimum detention period with a value of 3 minutes.
9. 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
Explanation: The detritus tanks are able to remove grit and sand particles by having a design velocity of 0.9m/Sec.
10. 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
Explanation: The skimming tank is used after the grit chamber to remove oil and grease from the sewage.
11. The detention period of detritus tank is ____________
a) 40 seconds
b) 1 minute
c) 3 minute
d) 1 hour
View Answer
Explanation: The detention period of detritus tank is 3 minutes. It is used to remove the grit present in the wastewater.
12. 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
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.
Sanfoundry Global Education & Learning Series – Environmental Engineering.
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