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

WW process: practice questions

Our Water/Wastewater Operator bank has 23 questions on this topic. Here are 5 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 is the main benefit of primary treatment before activated sludge?

  1. It removes solids and some BOD, reducing the load and air needed downstream
  2. It adds microorganisms
  3. It removes ammonia
  4. It disinfects the water
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A. It removes solids and some BOD, reducing the load and air needed downstream — Lower load lowers energy use.

Question 2 · Wastewater Treatment Class I

What is an oxidation ditch?

  1. A chlorine basin
  2. A grit channel
  3. A sludge lagoon
  4. A looped channel activated sludge system, often run as extended aeration
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D. A looped channel activated sludge system, often run as extended aeration — Brush or disc aerators move and aerate the flow.

Question 3 · Wastewater Treatment Class I

What does a sudden pH drop in the influent most likely indicate?

  1. Normal domestic flow during the morning peak
  2. An acidic industrial discharge
  3. Rainfall only
  4. More grit
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B. An acidic industrial discharge — Track down the source with pretreatment staff.

Question 4 · Wastewater Treatment Class I

The aeration basin DO is near zero and effluent is cloudy. What should be checked first?

  1. The grit chamber
  2. The UV lamps and the chlorine contact basin
  3. Blower operation and air delivery
  4. Chlorine dose
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C. Blower operation and air delivery — Low DO hurts treatment and settling.

Question 5 · Wastewater Treatment Class I

Why should operators avoid overloading a lagoon in cold weather?

  1. Biological activity slows in the cold, so treatment capacity drops
  2. It doesn't matter
  3. Lagoons work faster in winter
  4. Ice adds oxygen
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A. Biological activity slows in the cold, so treatment capacity drops — Plan storage or reduced loading.

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