Sedimentation

Question 1

How many zones are there in a sedimentation tank?

Answer 1

4

Question 2

Which is the largest zone in a sedimentation tank?

Answer 2

Settling zone

Question 3

In a conventional sedimentation tank, how long is the detention time?

Answer 3

2-6 hours

Question 4

What is short-circuiting?

Answer 4

When water takes a direct path from the influent to the effluent with out the fully mixing with the contents of the tank.

Question 5

What do you call the 4 zones in a sedimentation tank?

Answer 5

inlet, settling, sedimentation or sludge, outlet

Question 6

What affects the settling process?

Answer 6

temperature and turbidity

Question 7

• What are the advantages of a solid contact unit?

Answer 7

save on land use, all processes take place in one tank, save on chemicals, ability to adjust the slurry, especially to deal with algae problems,. capital and maintenance cost are reduced.

Question 8

For the volume over volume test, a _____ sample is taken from the _____ zone, and allowed to settle for____ minutes?

Answer 8

100ml / reaction zone / and 5 min

Question 9

What advice can you give to an operator at a neighboring plant who is experiencing high chemical cost?

Answer 9

recirculate chemicals

Question 10

⭐ when you took sludge samples, you determined that there was too much sludge in the tank. What will you do to correct this problem?

Answer 10

Increase the number of blowdowns or increase the duration of the blowdowns or both

Question 11

Observation of the treatment process indicates that there is not enough sludge in the treatment tank. What action is needed?

Answer 11

Reduce the number of blowdowns or their duration/ adjust the recirculation rate

Question 12

How do you adjust the recirculation rate?

Answer 12

Increase or decrease the flow ( some solid- contact units have a sludge recirculation device)

Question 13

By _____ The recirculation rate, a______ amount of sludge will be held in the tank.

Answer 13

Increasing, larger

Question 14

If the recirculation rate is too high, Will be carried over the_____.

Answer 14

Sludge slurry, filter

Question 15

How are the bottoms of sedimentation tanks and solid contact units configured to aid in sludge removal

Answer 15

They are sloped towards the center

Question 16

What would you install to improve Sedimentation?

Answer 16

Tube settlers

Question 17

What affects the efficiency of the tube Settlers?

Answer 17

High winds

Question 18

The gathering of a liquid or dissolve substance on the surface or interface zone of another material is called?

Answer 18

Absorption

Question 19

An electrical system for the preventing of rust or corrosion of metal surfaces that are in contact with water is called

Answer 19

Cathodic protection

Question 20

Indirect filtration, what process is omitted?

Answer 20

Sedimentation

Question 21

⭐ a water treatment process in which solid particles settle out of the water being treated is called

Answer 21

Sedimentation

Question 22

Put these processes in their correct order- flocculation, filtration, sedimentation, and coagulation.

Answer 22

Coagulation, flocculation, sedimentation, and filtration

Question 23

How do you prevent short- circuiting?

Answer 23

Install baffles

Question 24

⭐ if an overdose of coagulant occurs, what happens in solid- contact tanks?

Answer 24

Sludge settles to rapidly, and there is not enough sludge slurry recirculated

Question 25

⭐ how many sedimentation basins or solid contact units are needed in a water plant?

Answer 25

2

Question 26

⭐ how does the operator of a solid-contact unit control the performance of the unit?

Answer 26

Adjusting the chemical dose, recirculation rate, and sludge control

Question 27

What factors control the detention time?

Answer 27

Flow and tank volume

Question 28

Lower temperatures cause what condition in solid – contact tanks?

Answer 28

Slow settling

Question 29

Solid - contact units are most unstable during what conditions?

Answer 29

During rapid changes in temperature, flows and turbidity

Question 30

⭐ when there is a large increase in turbidity of the flow to a solid – contact unit, what action is needed?

Answer 30

Jar test or increase coagulant dose or change coagulant or increase alkalinity or adjust flash mixer/ flocculator speed/ intensity

Question 31

What will happen if the recirculation rate is too low?

Answer 31

Sledge will settle too fast and there will not be enough sludge Recirculating

Question 32

How is pin ink removed?

Answer 32

Filtration and or recarbonation

Question 33

What is the best test to evaluate the water treatment process?

Answer 33

Turbidity

Question 34

What is the best way to control chemical feed rates/ dosage in a WTP?

Answer 34

Electronically controlled chemical feeders

Question 35

A WTP is having problems maintaining its sludge blanket. What action is needed?

Answer 35

Adjust recirculation rate