WTO Sedimentation and Filtration 2

Question 1

What is the primary purpose of tube settlers installed in a sedimentation basin?

Accepted Answer

Reduce effective settling depth to improve particle removal

Answer

Tube settlers reduce the effective settling depth, allowing particles to settle over shorter distances and dramatically improving clarifier capacity.

Question 2

A rapid sand filter is backwashed when head loss reaches approximately what level above the clean bed loss?

Accepted Answer

5–8 feet

Answer

Most rapid sand filters are backwashed when head loss reaches roughly 5–8 feet above initial clean-bed head loss, indicating significant clogging.

Question 3

Which phenomenon causes a settled floc layer to resuspend and carry over the effluent weir during high flow periods?

Accepted Answer

Sludge blanket upset

Answer

A sludge blanket upset occurs when rising flow velocities exceed the settling rate of accumulated floc, causing it to resuspend and overflow the effluent weir.

Question 4

The Hazen-Williams equation is used in filtration systems primarily to calculate:

Accepted Answer

Head loss through filter media

Answer

The Hazen-Williams equation is used to estimate head loss (friction loss) through filter media and piping in water treatment systems.

Question 5

In a dual-media filter, anthracite coal is placed on top of sand because:

Accepted Answer

Coal has a lower specific gravity and larger grain size, allowing it to remain on top after backwash

Answer

Anthracite's lower specific gravity (1.4–1.6 vs. 2.65 for sand) and larger grain size cause it to stratify above the denser, finer sand after backwash.

(WTO) Water Treatment Operator Certification Practice Test

(WTO) Water Treatment Operator Certification Practice Test

WTO Sedimentation and Filtration 2