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

WT math: practice questions

Our Water/Wastewater Operator bank has 12 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 · Water Treatment Class I

A plant treats 1.5 MGD and adds alum at 20 mg/L. How many pounds of alum per day are used?

  1. About 167 lb/day
  2. About 2,500 lb/day
  3. About 30 lb/day
  4. About 250 lb/day
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D. About 250 lb/day — 20 × 1.5 × 8.34 ≈ 250.

Question 2 · Water Treatment Class I

How many pounds per day of chlorine are needed to dose 2 MGD at 3 mg/L?

  1. 6 lb/day
  2. 16.7 lb/day
  3. 50 lb/day
  4. 500 lb/day
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C. 50 lb/day — lb/day = mg/L × MGD × 8.34 = 3 × 2 × 8.34 ≈ 50.

Question 3 · Water Treatment Class I

How many gallons are in one cubic foot?

  1. 7.48
  2. 8.34
  3. 62.4
  4. 1,000
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A. 7.48 — Standard conversion.

Question 4 · Water Treatment Class I

A filter is 20 ft by 25 ft and receives 1,250 gpm. What is the filtration rate?

  1. 0.4 gpm/ft²
  2. 2.5 gpm/ft²
  3. 1.25 gpm/ft²
  4. 0.25 gpm/ft²
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B. 2.5 gpm/ft² — 1,250 ÷ 500 ft².

Question 5 · Water Treatment Class I

A water column is 23.1 feet high. About what pressure does it exert at the bottom?

  1. 2.3 psi
  2. 10 psi
  3. 23 psi
  4. 53 psi
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B. 10 psi — 1 psi = 2.31 ft of water.

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