Wastewater Operator Class I Licensing Exam
Prep | Questions And Answers With Verified
Rationales | 2026/27 Qs & Ans | Digital Pdf
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1. What is the primary purpose of wastewater treatment?
A. To increase water hardness
B. To remove contaminants from wastewater
C. To create drinking water directly
D. To add chemicals to rivers
Answer: B
Rationale: Wastewater treatment removes physical, chemical, and
biological contaminants before water is discharged back into the
environment.
2. Which process removes large debris from incoming wastewater?
A. Chlorination
B. Aeration
C. Screening
D. Digestion
Answer: C
Rationale: Screening is the preliminary treatment step that removes large
objects such as sticks, rags, and plastics.
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,3. What is measured by Biochemical Oxygen Demand (BOD)?
A. Amount of chlorine in water
B. Oxygen needed by microorganisms to decompose organic matter
C. Total suspended solids
D. Water temperature
Answer: B
Rationale: BOD indicates the strength of wastewater by measuring oxygen
consumed during biological decomposition.
4. Which unit is commonly used to measure flow in a wastewater plant?
A. Gallons per minute
B. Volts
C. Pounds per square inch
D. Degrees Celsius
Answer: A
Rationale: Flow rates in wastewater systems are commonly expressed in
gallons per minute (GPM) or million gallons per day (MGD).
5. What is the main purpose of grit removal?
A. Remove bacteria
B. Remove dissolved oxygen
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,C. Remove heavy inorganic particles
D. Add chlorine
Answer: C
Rationale: Grit chambers remove sand, gravel, and other heavy inorganic
materials that can damage equipment.
6. Which treatment stage primarily removes settleable solids?
A. Secondary treatment
B. Preliminary treatment
C. Primary treatment
D. Disinfection
Answer: C
Rationale: Primary clarifiers allow heavier solids to settle out by gravity.
7. Activated sludge is part of which treatment process?
A. Chemical treatment
B. Biological treatment
C. Disinfection treatment
D. Sludge drying
Answer: B
Rationale: Activated sludge uses microorganisms to biologically degrade
organic matter.
© 2026 Academics_Excellence. All Rights Reserved.
, 8. What is the ideal dissolved oxygen range in an aeration basin?
A. 0–0.5 mg/L
B. 8–10 mg/L
C. 1–3 mg/L
D. 15–20 mg/L
Answer: C
Rationale: Maintaining dissolved oxygen around 1–3 mg/L supports
healthy microbial activity.
9. Which microorganism is most important in activated sludge treatment?
A. Viruses
B. Algae
C. Bacteria
D. Protozoa
Answer: C
Rationale: Bacteria are the primary organisms responsible for
decomposing organic waste.
10. What does TSS stand for?
A. Total Settled Solids
B. Total Suspended Solids
© 2026 Academics_Excellence. All Rights Reserved.
Prep | Questions And Answers With Verified
Rationales | 2026/27 Qs & Ans | Digital Pdf
Download
1. What is the primary purpose of wastewater treatment?
A. To increase water hardness
B. To remove contaminants from wastewater
C. To create drinking water directly
D. To add chemicals to rivers
Answer: B
Rationale: Wastewater treatment removes physical, chemical, and
biological contaminants before water is discharged back into the
environment.
2. Which process removes large debris from incoming wastewater?
A. Chlorination
B. Aeration
C. Screening
D. Digestion
Answer: C
Rationale: Screening is the preliminary treatment step that removes large
objects such as sticks, rags, and plastics.
© 2026 Academics_Excellence. All Rights Reserved.
,3. What is measured by Biochemical Oxygen Demand (BOD)?
A. Amount of chlorine in water
B. Oxygen needed by microorganisms to decompose organic matter
C. Total suspended solids
D. Water temperature
Answer: B
Rationale: BOD indicates the strength of wastewater by measuring oxygen
consumed during biological decomposition.
4. Which unit is commonly used to measure flow in a wastewater plant?
A. Gallons per minute
B. Volts
C. Pounds per square inch
D. Degrees Celsius
Answer: A
Rationale: Flow rates in wastewater systems are commonly expressed in
gallons per minute (GPM) or million gallons per day (MGD).
5. What is the main purpose of grit removal?
A. Remove bacteria
B. Remove dissolved oxygen
© 2026 Academics_Excellence. All Rights Reserved.
,C. Remove heavy inorganic particles
D. Add chlorine
Answer: C
Rationale: Grit chambers remove sand, gravel, and other heavy inorganic
materials that can damage equipment.
6. Which treatment stage primarily removes settleable solids?
A. Secondary treatment
B. Preliminary treatment
C. Primary treatment
D. Disinfection
Answer: C
Rationale: Primary clarifiers allow heavier solids to settle out by gravity.
7. Activated sludge is part of which treatment process?
A. Chemical treatment
B. Biological treatment
C. Disinfection treatment
D. Sludge drying
Answer: B
Rationale: Activated sludge uses microorganisms to biologically degrade
organic matter.
© 2026 Academics_Excellence. All Rights Reserved.
, 8. What is the ideal dissolved oxygen range in an aeration basin?
A. 0–0.5 mg/L
B. 8–10 mg/L
C. 1–3 mg/L
D. 15–20 mg/L
Answer: C
Rationale: Maintaining dissolved oxygen around 1–3 mg/L supports
healthy microbial activity.
9. Which microorganism is most important in activated sludge treatment?
A. Viruses
B. Algae
C. Bacteria
D. Protozoa
Answer: C
Rationale: Bacteria are the primary organisms responsible for
decomposing organic waste.
10. What does TSS stand for?
A. Total Settled Solids
B. Total Suspended Solids
© 2026 Academics_Excellence. All Rights Reserved.
