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Water & Wastewater Operator (WPI/ABC Class I) — Practice Exam

WW equipment: aeration: practice questions

Our Water/Wastewater Operator bank has 7 questions on this topic. Here are 4 of them with answers; the full mock exam draws from every topic, like the real one.

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Question 1 · Wastewater Treatment Class I

What happens to diffusers fouled by biological growth or scale?

  1. Bubbles get larger and transfer more
  2. Back pressure rises and oxygen transfer drops
  3. They release smaller bubbles, so oxygen transfer improves
  4. Airflow improves
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B. Back pressure rises and oxygen transfer drops — Cleaning restores efficiency.

Question 2 · Wastewater Treatment Class I

What is a surface aerator?

  1. A diffuser mounted on the basin floor
  2. A mechanical mixer at the water surface that throws water into the air to add oxygen
  3. A diffuser on the basin floor
  4. A clarifier skimmer
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B. A mechanical mixer at the water surface that throws water into the air to add oxygen — Common in lagoons and oxidation ditches.

Question 3 · Wastewater Treatment Class I

Which aeration system releases fine bubbles from the basin floor?

  1. Fine-bubble diffusers
  2. Mechanical brushes
  3. Surface aerators
  4. Mechanical brush aerators
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A. Fine-bubble diffusers — Fine bubbles transfer oxygen more efficiently.

Question 4 · Wastewater Treatment Class I

What does a DO probe in an aeration basin need regularly?

  1. Painting and replacement every day
  2. Lubricating
  3. Painting
  4. Cleaning and calibration
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D. Cleaning and calibration — Fouled probes read low or drift.

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