Level 3 · Advanced sample questions
5 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.
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?
Answer: D. Collector, track, and support alignment
Torque and motor current rise together at one repeatable position, while the blanket and gearbox indicators remain normal. That pattern supports a localized mechanical bind involving the collector, track, or supports.
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?
Answer: D. That flight and its chain attachments
The jerk follows the marked flight rather than occurring at one fixed location. Because other flights move smoothly through the same locations, the marked flight and its attachments are the most likely source.
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?
Answer: C. Too much time between sludge withdrawals
Equal flow, normal collector operation, and a verified withdrawal rate rule out the other listed causes. Because the blanket drops quickly when pumping begins, the pump has capacity but is not being run often enough to prevent accumulation.
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?
Answer: D. Use equalization to reduce peak clarifier flow
Low blankets, equal flow splitting, and unchanged settling behavior do not indicate sludge buildup or poorer particle settling. The solids loss occurs with peak hydraulic loading, so available equalization should be used to reduce the peak flow through the clarifiers.
A primary-clarifier blanket swings high and low under a fixed pump timer as solids loading changes. The blanket signal is verified, and the sludge pump can vary speed. Which control change best stabilizes the blanket?
Answer: A. Use verified blanket feedback
A verified blanket signal can provide feedback as solids loading changes, and variable pump speed can respond smoothly. Fixed speed, influent-only control, and shorter fixed cycles do not directly control the measured blanket.
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