Wastewater Operator Class III Licensing
Exam Practice Test Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
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1. What is the primary purpose of a wastewater treatment plant?
A. To produce drinking water
B. To remove contaminants from wastewater
C. To increase water salinity
D. To store stormwater
Rationale: Wastewater treatment plants are designed to remove physical,
chemical, and biological contaminants before discharge or reuse.
2. Which process removes large debris from wastewater?
A. Sedimentation
B. Screening
C. Chlorination
D. Aeration
Rationale: Screening is the first step and removes large solids like rags and
sticks.
3. What does BOD measure?
A. Chemical toxicity
B. Oxygen demand of microorganisms
, C. pH level
D. Water hardness
Rationale: Biochemical Oxygen Demand (BOD) measures the oxygen used
by bacteria to decompose organic matter.
4. Which unit is used for flow measurement?
A. PSI
B. MGD
C. ppm
D. mg/L
Rationale: Million gallons per day (MGD) is commonly used for
wastewater flow.
5. What is the function of a bar screen?
A. Remove dissolved solids
B. Remove large solids
C. Add chlorine
D. Increase oxygen
Rationale: Bar screens trap large debris before further treatment.
6. Primary treatment mainly involves:
A. Filtration
B. Sedimentation
C. Disinfection
D. Digestion
Rationale: Primary treatment relies on settling solids by gravity.
7. What gas is commonly produced in anaerobic digestion?
A. Oxygen
B. Methane
C. Nitrogen
D. Chlorine
Rationale: Methane is produced during anaerobic decomposition of
organic matter.
, 8. Aeration tanks are used to:
A. Remove solids
B. Provide oxygen to bacteria
C. Filter metals
D. Add chemicals
Rationale: Aeration supports aerobic bacteria in breaking down waste.
9. What does pH measure?
A. Temperature
B. Acidity or alkalinity
C. Flow rate
D. Turbidity
Rationale: pH indicates whether water is acidic or basic.
10.Chlorination is used for:
A. Sedimentation
B. Disinfection
C. Filtration
D. Aeration
Rationale: Chlorine kills pathogens in wastewater.
11.Sludge is primarily:
A. Clean water
B. Settled solids
C. Air bubbles
D. Dissolved salts
Rationale: Sludge consists of solids removed during treatment.
12.Secondary treatment mainly removes:
A. Plastics
B. Dissolved organic matter
C. Metals
D. Sand
Rationale: Biological processes remove dissolved organic material.
Exam Practice Test Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
1. What is the primary purpose of a wastewater treatment plant?
A. To produce drinking water
B. To remove contaminants from wastewater
C. To increase water salinity
D. To store stormwater
Rationale: Wastewater treatment plants are designed to remove physical,
chemical, and biological contaminants before discharge or reuse.
2. Which process removes large debris from wastewater?
A. Sedimentation
B. Screening
C. Chlorination
D. Aeration
Rationale: Screening is the first step and removes large solids like rags and
sticks.
3. What does BOD measure?
A. Chemical toxicity
B. Oxygen demand of microorganisms
, C. pH level
D. Water hardness
Rationale: Biochemical Oxygen Demand (BOD) measures the oxygen used
by bacteria to decompose organic matter.
4. Which unit is used for flow measurement?
A. PSI
B. MGD
C. ppm
D. mg/L
Rationale: Million gallons per day (MGD) is commonly used for
wastewater flow.
5. What is the function of a bar screen?
A. Remove dissolved solids
B. Remove large solids
C. Add chlorine
D. Increase oxygen
Rationale: Bar screens trap large debris before further treatment.
6. Primary treatment mainly involves:
A. Filtration
B. Sedimentation
C. Disinfection
D. Digestion
Rationale: Primary treatment relies on settling solids by gravity.
7. What gas is commonly produced in anaerobic digestion?
A. Oxygen
B. Methane
C. Nitrogen
D. Chlorine
Rationale: Methane is produced during anaerobic decomposition of
organic matter.
, 8. Aeration tanks are used to:
A. Remove solids
B. Provide oxygen to bacteria
C. Filter metals
D. Add chemicals
Rationale: Aeration supports aerobic bacteria in breaking down waste.
9. What does pH measure?
A. Temperature
B. Acidity or alkalinity
C. Flow rate
D. Turbidity
Rationale: pH indicates whether water is acidic or basic.
10.Chlorination is used for:
A. Sedimentation
B. Disinfection
C. Filtration
D. Aeration
Rationale: Chlorine kills pathogens in wastewater.
11.Sludge is primarily:
A. Clean water
B. Settled solids
C. Air bubbles
D. Dissolved salts
Rationale: Sludge consists of solids removed during treatment.
12.Secondary treatment mainly removes:
A. Plastics
B. Dissolved organic matter
C. Metals
D. Sand
Rationale: Biological processes remove dissolved organic material.
