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

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

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

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

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

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

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

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

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

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

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

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