Food Processing Unit Operations Questions and Answers for Entrance exams on “Mechanical Separation – Sedimentation Equipment”.
1. What should be the velocity for the sedimentation process?
a) High
b) Low
c) Does not depend
d) Very high
Answer: b
Clarification: In sedimentation tank, the continuous flow through the equipment is commonly desired, so therefore the flow velocities have to be low enough to avoid unsettling of the sediment.
2. What is flotation?
a) Removal of fine particles by air bubbles
b) Removal of fine particles by sedimentation
c) Removal of fine particles by chelating agents
d) Removal of large particles by air bubbles
Answer: a
Clarification: In some cases, where it is difficult to remove fine particles, therefore floatation equipment is used where these are floated to the surface with the help of air bubbles.
3. Which of the following food industry uses floatation equipment?
a) Sugar industry
b) Oil industry
c) Bakery industry
d) Salt industry
Answer: b
Clarification: In the food industry, floatation is used in the separation of small particles of fat from water. The air dissolved in water under pressure produces the froth. When the pressure suddenly released, the air comes out of solution in the form of bubbles which rise and carry the fat with them to surface.
4. What is limitation of large sedimentation tank?
a) Regarding contact time
b) Regarding efficiency
c) Regarding quality
d) Regarding quantity
Answer: a
Clarification: The disadvantages of large sedimentation tank are the slow rate of sedimentation, it requires large chamber areas and the long contact times between particles and the heated air that results in deterioration of heat-sensitive products.
5. What is the accumulated at the bottom in sedimentation tank?
a) Solute
b) Solvent
c) Solution
d) Sludge
Answer: d
Clarification: In the sedimentation tank, a layer of accumulated solids is formed at the bottom of the tank and is periodically removed. This is known as sludge.
6. Is ballasted flocculation a physical-chemical sedimentation process?
a) True
b) False
Answer: a
Clarification: Ballasted flocculation is a high-rate, physical-chemical sedimentation process involving the fixing of flocs, or suspended solids, onto ballast generally sand with the help of a polymer.
7. What are clarifiers?
a) Horizontal basin sedimentation tank
b) Circular basin sedimentation tank
c) Vertical basin sedimentation tank
d) Square basin sedimentation tank
Answer: b
Clarification: The Circular basins are called as clarifiers. These basins are similar to rectangular basins, but are more prone to short circuiting and particle removal problems.
8. How is sludge removed from sedimentation tank?
a) Scraper
b) Air
c) Vacuum devices
d) Scraper and vacuum devices
Answer: d
Clarification: The Sludge is removed from the sludge zone in sedimentation tank by scraper or vacuum devices which move along the bottom. Low flow velocities are allowed to enter the sludge zone, or else the sludge could be swept up and out of tank.
9. What is the largest portion of the sedimentation basin?
a) Sludge zone
b) Settling zone
c) Inlet zone
d) Outlet zone
Answer: b
Clarification: The settling zone is the largest portion of the sedimentation basin. This zone provides the area essential for the settling of the suspended particles.
10. Are these statements about the rectangle sedimentation tank true?
Statement 1: Low tolerance to shock overload.
Statement 2: Minimal short circuiting.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: Rectangular sedimentation basins are used in large-scale water treatment plants. They are high tolerance to shock overload. It is cost effectiveness due to lower construction cost and lower maintenance. It has minimal short circuiting.
Food Processing Unit Operations for Entrance exams,