Sedimentation Flashcards
How many zones are there in a sedimentation tank?
4
Which is the largest zone in a sedimentation tank?
Settling zone
In a conventional sedimentation tank, how long is the detention time?
2-6 hours
What is short-circuiting?
When water takes a direct path from the influent to the effluent with out the fully mixing with the contents of the tank.
What do you call the 4 zones in a sedimentation tank?
inlet, settling, sedimentation or sludge, outlet
What affects the settling process?
temperature and turbidity
- What are the advantages of a solid contact unit?
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.
For the volume over volume test, a _____ sample is taken from the _____ zone, and allowed to settle for____ minutes?
100ml / reaction zone / and 5 min
What advice can you give to an operator at a neighboring plant who is experiencing high chemical cost?
recirculate chemicals
⭐ when you took sludge samples, you determined that there was too much sludge in the tank. What will you do to correct this problem?
Increase the number of blowdowns or increase the duration of the blowdowns or both
Observation of the treatment process indicates that there is not enough sludge in the treatment tank. What action is needed?
Reduce the number of blowdowns or their duration/ adjust the recirculation rate
How do you adjust the recirculation rate?
Increase or decrease the flow ( some solid- contact units have a sludge recirculation device)
By _____ The recirculation rate, a______ amount of sludge will be held in the tank.
Increasing, larger
If the recirculation rate is too high, Will be carried over the_____.
Sludge slurry, filter
How are the bottoms of sedimentation tanks and solid contact units configured to aid in sludge removal
They are sloped towards the center
What would you install to improve Sedimentation?
Tube settlers
What affects the efficiency of the tube Settlers?
High winds
The gathering of a liquid or dissolve substance on the surface or interface zone of another material is called?
Absorption
An electrical system for the preventing of rust or corrosion of metal surfaces that are in contact with water is called
Cathodic protection
Indirect filtration, what process is omitted?
Sedimentation
⭐ a water treatment process in which solid particles settle out of the water being treated is called
Sedimentation
Put these processes in their correct order- flocculation, filtration, sedimentation, and coagulation.
Coagulation, flocculation, sedimentation, and filtration
How do you prevent short- circuiting?
Install baffles
⭐ if an overdose of coagulant occurs, what happens in solid- contact tanks?
Sludge settles to rapidly, and there is not enough sludge slurry recirculated
⭐ how many sedimentation basins or solid contact units are needed in a water plant?
2
⭐ how does the operator of a solid-contact unit control the performance of the unit?
Adjusting the chemical dose, recirculation rate, and sludge control
What factors control the detention time?
Flow and tank volume
Lower temperatures cause what condition in solid – contact tanks?
Slow settling
Solid - contact units are most unstable during what conditions?
During rapid changes in temperature, flows and turbidity
⭐ when there is a large increase in turbidity of the flow to a solid – contact unit, what action is needed?
Jar test or increase coagulant dose or change coagulant or increase alkalinity or adjust flash mixer/ flocculator speed/ intensity
What will happen if the recirculation rate is too low?
Sledge will settle too fast and there will not be enough sludge Recirculating
How is pin ink removed?
Filtration and or recarbonation
What is the best test to evaluate the water treatment process?
Turbidity
What is the best way to control chemical feed rates/ dosage in a WTP?
Electronically controlled chemical feeders
A WTP is having problems maintaining its sludge blanket. What action is needed?
Adjust recirculation rate
