WTO - Water Treatment Operator Sedimentation and Filtration Questions and Answers

Question 1

Which of the following principles primarily governs the process of sedimentation in a water treatment clarifier?

Accepted Answer

Gravity

Answer

Centrifugal Force

Answer

Brownian Motion

Answer

Electrostatic Attraction

Question 2

A water treatment plant is treating raw water with low turbidity and high quality. To reduce capital and operational costs, which treatment scheme would be most appropriate?

Accepted Answer

Direct Filtration

Answer

Conventional Filtration

Answer

Slow Sand Filtration

Answer

Diatomaceous Earth Filtration

Question 3

An operator observes a rapid increase in head loss across a gravity filter, and the finished water turbidity is approaching the regulatory limit. What is the most immediate and appropriate action to take?

Accepted Answer

Initiate a backwash cycle.

Answer

Increase the coagulant dose.

Answer

Decrease the filtration rate.

Answer

Add a polymer aid to the influent.

Question 4

According to Stokes' Law, which characteristic of a suspended particle will result in the fastest settling velocity in a sedimentation basin?

Accepted Answer

High density and large diameter

Answer

Low density and small diameter

Answer

High density and small diameter

Answer

Low density and large diameter

Question 5

During a filter backwash, what is the primary purpose of the initial air scour phase?

Accepted Answer

To break up the compacted filter bed and loosen trapped particles.

Answer

To disinfect the filter media with oxygen.

Answer

To stratify the filter media by size.

Answer

To warm the backwash water to improve cleaning efficiency.

Question 6

A water treatment plant using conventional filtration is experiencing an issue with floc carryover from the sedimentation basin to the filters. Which of the following is a likely cause?

Accepted Answer

Flow velocity through the basin is too high.

Answer

Excessively long detention time in the basin.

Answer

The coagulant dosage is too high.

Answer

The raw water temperature has significantly increased.