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Wastewater Treatment License Exam
(Latest Update) Questions
and Verified Answers | 100% Correct
| Grade A+
1. The primary purpose of a bar screen in a wastewater
treatment plant is to:
A) Remove grit and sand
B) Remove large solids (rags, sticks, plastics) that could damage
pumps and equipment
C) Remove oil and grease
D) Equalize flow
Answer: B
Rationale: Bar screens capture large debris to protect
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downstream equipment such as pumps, valves, and clarifiers. Grit
removal is done by grit chambers (not bar screens).
2. A mechanically cleaned bar screen should be cleaned at a
frequency determined by:
A) The manufacturer’s recommendation only
B) The head loss across the screen
C) The color of the debris
D) The time of day
Answer: B
Rationale: Head loss increases as solids accumulate. Cleaning is
initiated when head loss reaches a predetermined value (e.g., 6–
12 inches) to maintain hydraulic capacity.
3. The typical particle size removed by a fine bar screen (6
mm spacing) is:
A) > 25 mm
B) 6–25 mm
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C) < 6 mm
D) Only dissolved solids
Answer: B
Rationale: Fine screens have openings of 1.5–6 mm and remove
smaller solids, but “fine” typically refers to 6 mm spacing,
capturing particles 6–25 mm. Microscreens remove particles < 1
mm.
4. A grit chamber is designed to remove:
A) Organic solids
B) Inorganic solids (sand, gravel, eggshells) with specific gravity
~2.65
C) Floating debris
D) Bacteria
Answer: B
Rationale: Grit chambers remove heavy inorganic particles that
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would otherwise abrade pumps and accumulate in digesters.
Typical specific gravity of grit is 2.65.
5. The recommended horizontal velocity in a rectangular
aerated grit chamber is:
A) 0.1–0.3 m/s
B) 0.6–0.9 m/s
C) 1.5–2.0 m/s
D) 3.0–4.0 m/s
Answer: B
Rationale: For aerated grit chambers, a horizontal velocity of
0.6–0.9 m/s (2–3 ft/s) allows grit to settle while keeping lighter
organics in suspension.
6. True or False: Grit removal is usually located downstream of
bar screens and upstream of primary clarifiers.
A) True
B) False
Wastewater Treatment License Exam
(Latest Update) Questions
and Verified Answers | 100% Correct
| Grade A+
1. The primary purpose of a bar screen in a wastewater
treatment plant is to:
A) Remove grit and sand
B) Remove large solids (rags, sticks, plastics) that could damage
pumps and equipment
C) Remove oil and grease
D) Equalize flow
Answer: B
Rationale: Bar screens capture large debris to protect
,Page 2 of 42
downstream equipment such as pumps, valves, and clarifiers. Grit
removal is done by grit chambers (not bar screens).
2. A mechanically cleaned bar screen should be cleaned at a
frequency determined by:
A) The manufacturer’s recommendation only
B) The head loss across the screen
C) The color of the debris
D) The time of day
Answer: B
Rationale: Head loss increases as solids accumulate. Cleaning is
initiated when head loss reaches a predetermined value (e.g., 6–
12 inches) to maintain hydraulic capacity.
3. The typical particle size removed by a fine bar screen (6
mm spacing) is:
A) > 25 mm
B) 6–25 mm
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C) < 6 mm
D) Only dissolved solids
Answer: B
Rationale: Fine screens have openings of 1.5–6 mm and remove
smaller solids, but “fine” typically refers to 6 mm spacing,
capturing particles 6–25 mm. Microscreens remove particles < 1
mm.
4. A grit chamber is designed to remove:
A) Organic solids
B) Inorganic solids (sand, gravel, eggshells) with specific gravity
~2.65
C) Floating debris
D) Bacteria
Answer: B
Rationale: Grit chambers remove heavy inorganic particles that
, Page 4 of 42
would otherwise abrade pumps and accumulate in digesters.
Typical specific gravity of grit is 2.65.
5. The recommended horizontal velocity in a rectangular
aerated grit chamber is:
A) 0.1–0.3 m/s
B) 0.6–0.9 m/s
C) 1.5–2.0 m/s
D) 3.0–4.0 m/s
Answer: B
Rationale: For aerated grit chambers, a horizontal velocity of
0.6–0.9 m/s (2–3 ft/s) allows grit to settle while keeping lighter
organics in suspension.
6. True or False: Grit removal is usually located downstream of
bar screens and upstream of primary clarifiers.
A) True
B) False
