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Level 3 · Advanced sample questions

Primary Treatment Practice Questions for Level 3 · Advanced

4 free sample questions on primary treatment for the Level 3 · Advanced wastewater treatment operator exam. Try each one, then open the answer to check your work.

  1. Question 1

    A circular clarifier drive reaches high torque at the same point in each rotation. Motor current rises with torque at that point. Blanket depth is normal, and gearbox temperature and oil level remain steady. What should be inspected first under the isolation procedure?

    1. Sludge withdrawal rate and blanket control
    2. Torque transmitter and overload setting
    3. Gearbox lubrication and bearing temperature
    4. Collector, track, and support alignment
    Show the answer

    Answer: D. Collector, track, and support alignment

  2. Question 2

    A rectangular clarifier's chain-and-flight collector jerks once during each complete chain circuit. Operators mark one flight and find that the jerk follows that flight through different parts of the tank. Other flights move smoothly through those same locations. Which part should be inspected first?

    1. Main drive and reducer
    2. Common drive sprocket, shaft, and bearings
    3. Return-end sprocket, shaft, and bearings
    4. Marked flight and its attachments
    Show the answer

    Answer: D. Marked flight and its attachments

  3. Question 3

    Two primary clarifiers receive equal, steady flows. One develops a high sludge blanket and rising effluent TSS. Its collector works normally, and the blanket drops quickly when the sludge pump runs at its verified normal rate. What is the most likely problem?

    1. Unequal clarifier flow split
    2. Loss of sludge-pump capacity during withdrawal
    3. Too much time between sludge withdrawals
    4. Failure of the collector to move settled sludge
    Show the answer

    Answer: C. Too much time between sludge withdrawals

  4. Question 4

    Primary effluent TSS rises during peak flow. Clarifier blankets remain low, flow is evenly split, and settling tests clear as quickly as before the peak. Equalization storage is available. Which response best addresses the solids loss?

    1. Increase sludge withdrawal to lower the blankets
    2. Shift more flow toward the lowest-blanket clarifier
    3. Increase coagulant feed to improve settling
    4. Use equalization to reduce peak clarifier flow
    Show the answer

    Answer: D. Use equalization to reduce peak clarifier flow

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