Practice Test Geeks(WTO) Water Treatment Operator Certification Practice Test
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Sedimentation and Filtration Flashcards

7 cards from real WTO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Sedimentation and Filtration flashcards as text

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

    Answer: Reduce effective settling depth to improve particle removal

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

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

    Answer: 5–8 feet

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

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

    Answer: Sludge blanket upset

    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.

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

    Answer: Head loss through filter media

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

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

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

    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.

  6. What condition is indicated when a filter's turbidity breakthrough occurs early in the filter run, shortly after returning to service?

    Answer: Filter ripening is incomplete or improper backwash

    Early turbidity breakthrough after returning to service typically indicates incomplete filter ripening, often caused by over-washing or failure to use a filter-to-waste period.

  7. Weir overflow rate (WOR) in a sedimentation basin is expressed in units of:

    Answer: Million gallons per day per linear foot of weir

    Weir overflow rate is expressed as flow per unit length of weir (gpd/ft or MGD/ft), which controls the velocity at which water leaves the basin and entrains floc.