Sedimentation

Question 1

This is where the particles are separated from the liquid by gravitational forces.

Answer 1

Sedimentation

Question 2

It includes the _________ from liquid sewage wastes, settling of crystals from the mother liquor, and separation of the liquid-liquid mixture from a solvent extraction.

Answer 2

Removal of solids

Question 3

When the particles are crowded, they settle at a lower rate. A particle is sufficiently far from the walls of the container and other particles so that it stays and is not affected by them.

Answer 3

The first statement is true. The second statement is false.

Question 4

In some sedimentation processes, the purpose is to remove the particles from the fluid stream so that the fluid is free of particle contaminants. Fluid can exist in the form of a liquid or gas, and it can be either stationary or in motion.

Answer 4

Both statements are true

Question 5

It is the proportionality constant and dimensionless

Answer 5

Drag coefficient

Question 6

Whenever a particle moves through a fluid, one force will act on the particle.

Answer 6

The statement is false

Question 7

The resultant force must be equal to the force due to?

Answer 7

Acceleration

Question 8

Gravity acting_____, buoyant force acting______, and drag force acting ______

Answer 8

Downward, upward, downward

Question 9

The buoyant force on the particle will counterbalance the external force and the particle will move relative to the fluid.

Answer 9

The statement is false

Question 10

The external force of gravity is needed to impart motion to the particle. Density is not needed between the particle and the fluid.

Answer 10

The first statement is true. The second statement is false.

Question 11

What is the process called when a dilute slurry separates by gravity into a clear fluid and a slurry of higher solids concentration?

Answer 11

Sedimentation

Question 12

What is the primary mechanism of sedimentation?

Answer 12

Gravity

Question 13

What is the purpose of a batch settling test?

Answer 13

To measure the settling velocity of a slurry

Question 14

What is the purpose of a batch settling test in determining settling velocities and mechanisms of settling?

Answer 14

To determine the settling velocity of particles

Question 15

What happens to the particles in zone B during the batch settling test?

Answer 15

They settle at a uniform rate

Question 16

What happens to the height z during the batch settling test?

Answer 16

It decreases

Question 17

What is the clear liquid zone in the batch settling test?

Answer 17

Zone A

Question 18

What happens during compression in the batch settling test?

Answer 18

Liquid is expelled upward from zone D

Question 19

What is the critical point in the batch settling test?

Answer 19

The point where compression first appears

Question 20

What is the method proposed by Talmage and Fitch for determining thickener area?

Answer 20

Talmage and Fitch procedure

Question 21

For many cases in settling, a small number of particles are present. The velocity gradients surrounding each particle are affected by the close presence of other particles.

Answer 21

The first statement is true. The second statement is false.

Question 22

In settling, the surrounding particles interfere with the motion of ______ particles.

Answer 22

Individual

Question 23

The particles in settling in the liquid displace the solid. An appreciable downward velocity of the liquid is generated.

Answer 23

Both statements are false

Question 24

The velocity of the liquid is appreciably ____ with respect to the particle than with respect to the apparatus itself.

Answer 24

Greater

Question 25

The true drag force is greater in the suspension because?

Answer 25

'Because of the interference of other particles.

Question 26

The higher viscosity of the mixture is equal to what?

Answer 26

The actual viscosity of the liquid

Question 27

The empirical correction factor depends upon what?

Answer 27

The volume fraction of the slurry mixture occupied by the liquid

Question 28

When the Reynolds number is less than 1, the settling is in the?

Answer 28

Stokes` Law regime

Question 29

When will the wall effect be exerted on the particle?

Answer 29

When the diameter of the particle becomes appreciable with respect to the diameter of the container.

Question 30

What happens to the terminal velocity when the wall effect is exerted on the particle?

Answer 30

It reduces

Question 31

The Spitzkasten classifier separates particles based on what principle?

Answer 31

Size and density

Question 32

In which industry is the Spitzkasten classifier commonly used?

Answer 32

Mining industry

Question 33

What is the advantage of using a Spitzkasten classifier?

Answer 33

It can handle large volumes of material and is relatively inexpensive.

Question 34

What is the limitation of a Spitzkasten classifier?

Answer 34

It may not be suitable for very fine particles.

Question 35

What is the other name for the sedimentation process called?

Answer 35

Thickening

Question 36

What is the main purpose of a sedimentation thickener in wastewater treatment?

Answer 36

To separate solids from the liquid using gravity

Question 37

What is the shape of a typical sedimentation thickener?

Answer 37

Cylindrical

Question 38

What is the advantage of using a sedimentation thickener?

Answer 38

It is a simple and cost-effective method for thickening sludge.

Question 39

What is the limitation of a sedimentation thickener?

Answer 39

Overfeeding the thickener can lead to reduced efficiency.

Question 40

In a laboratory set-up, what happens to the solids in the suspension after the sedimentation process?

Answer 40

They settle at the bottom of the tank.

Question 41

Brownian motion is present if the particles are?

Answer 41

quite small

Question 42

How does Brownian motion affect the settling of particles?

Answer 42

It may occur slowly or not at all

Question 43

At what particle size (approximately) does Brownian motion become appreciable?

Answer 43

a few micrometers

Question 44

Which of the following methods can help reduce the effect of Brownian motion for very small particles?

Answer 44

applying centrifugal force

Question 45

What is the term used for a particle falling under the action of gravity that will accelerate until the drag force balances gravitational force?

Answer 45

Terminal velocity

Question 46

What factors can cause fluctuations in the settling of particles?

Answer 46

Vortex shedding and particle shape

Question 47

Where did the drag crisis occur?

Answer 47

At lower Reynolds number when the free stream is turbulent.

Question 48

What is the random motion imparted to the particle by collisions between the molecules of the fluid surrounding the particle and particle? 

Answer 48

Brownian Motion

Question 49

Internal circulation inside the particle and particle deformation can occur when the particles are?

Answer 49

Non-rigid

Question 50

In the turbulent Newton’s law region above a Reynolds number of about , the drag coefficient is?

Answer 50

0.44

Question 51

Helps in separating coal samples according to the difference in their respective specific gravities in a heavy liquid medium.

Answer 51

Sink and Float Method

Question 52

Devices for the separation of solid particles into several fractions based upon their rates of flow or settling through fluids are known as _____

Answer 52

Classifiers

Question 53

Sink and float method is dependent on the sizes of the particles and depends only upon the relative densities of the two materials. This means liquid used must have densities greater than water, since most solid has high densities

Answer 53

The first statement is false. The second statement is true

Question 54

Utilizes the difference in terminal velocities that can exist between substances of different densities

Answer 54

Differential Settling method

Question 55

What is the disadvantage of the Differential Settling method

Answer 55

the larger, light particles settle at the same rate as the smaller heavy ones and mixed fraction is obtained

Question 56

In the Sink and Float method, what happens to the heavy and light material?

Answer 56

the heavy material sinks through the medium while the lighter material floats

Question 57

Use of Differential Settling method

Answer 57

to bring in the concept of equal-settling particles

Question 58

This method is also called heavy-fluid separation

Answer 58

Sink and Float method

Question 59

In the sink and float method, both light and heavy materials settle through the same medium. This method also brings in the concept of the equal-settling method

Answer 59

Both statements are false

Question 60

What is the advantage of the Sink and Float method?

Answer 60

the separation depends only on the difference in the densities of the two substances and is independent of the particle size

Question 61

The time given by dividing the vertical height of the chamber by the settling velocity must be ______ the residence time of air

Answer 61

less than

Question 62

Which of the following factors most significantly affects the settling velocity of particles in a batch sedimentation tank?

Answer 62

particle size and density difference between the particles and the liquid

Question 63

Which of the following statements about the advantages of batch sedimentation is NOT true?

Answer 63

it is a continuous process, allowing for constant operation

Question 64

The main purpose of a primary settling tank in wastewater treatment is to:

Answer 64

remove a significant portion of settleable organic matter and grit through gravity separation

Question 65

Which of the following applications is NOT well-suited for batch sedimentation?

Answer 65

continuous production of a chemical product

Question 66

When designing a batch sedimentation tank, it's important to consider the strength and stability of the structure. What factor plays a crucial role in determining the required wall thickness?

Answer 66

the depth of the tank and the volume of liquid it will hold.

Question 67

Compared to some other wastewater treatment technologies, batch sedimentation offers the advantage of:

Answer 67

being a relatively simple and low-tech process with minimal moving parts

Question 68

The overall efficiency of a batch sedimentation process can be limited by:

Answer 68

incomplete removal of settled solids during the unloading stage, leading to solids carryover in the effluent

Question 69

Materials used for the construction of a batch sedimentation tank should be:

Answer 69

chemically resistant to the wastewater being treated

Question 70

How does properly operating and maintaining a primary settling tank impact a wastewater treatment plant?

Answer 70

improved effluent quality and reduced downstream treatment burden