Wastewater Operator Class I Licensing Exam
Test Questions and Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a wastewater treatment plant?
A. Generate electricity
B. Remove contaminants from wastewater
C. Produce drinking water directly
D. Increase water hardness
Answer: B
Rationale: Wastewater treatment plants are designed to remove
physical, chemical, and biological contaminants before discharge or
reuse.
2. Which process is considered primary treatment?
A. Chlorination
B. Screening and sedimentation
,C. Aeration
D. Filtration
Answer: B
Rationale: Primary treatment involves physical removal of solids
through screening and settling.
3. What is the main purpose of bar screens?
A. Remove dissolved solids
B. Remove large debris
C. Add oxygen
D. Adjust pH
Answer: B
Rationale: Bar screens remove large objects such as rags and sticks from
influent wastewater.
4. Which microorganism is most important in activated sludge
systems?
A. Fish
B. Protozoa and bacteria
C. Algae only
,D. Viruses
Answer: B
Rationale: Bacteria and protozoa break down organic matter in
biological treatment systems.
5. What does BOD measure?
A. Chemical toxicity
B. Oxygen required by microorganisms to decompose organic matter
C. Hardness of water
D. pH level
Answer: B
Rationale: Biochemical Oxygen Demand indicates the amount of oxygen
needed for microbial decomposition.
6. What is the ideal pH range for most biological wastewater
treatment processes?
A. 1–3
B. 4–5
C. 6.5–8.5
D. 10–12
, Answer: C
Rationale: Most biological processes function best in a near-neutral pH
range.
7. What is the purpose of aeration tanks?
A. Remove solids by gravity
B. Add oxygen for microorganisms
C. Filter metals
D. Store sludge
Answer: B
Rationale: Aeration tanks supply oxygen to support aerobic microbial
activity.
8. What is sludge?
A. Clean water
B. Solid waste separated from wastewater
C. Chlorinated effluent
D. Rainwater runoff
Answer: B
Rationale: Sludge consists of settled solids removed during treatment.
Test Questions and Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary purpose of a wastewater treatment plant?
A. Generate electricity
B. Remove contaminants from wastewater
C. Produce drinking water directly
D. Increase water hardness
Answer: B
Rationale: Wastewater treatment plants are designed to remove
physical, chemical, and biological contaminants before discharge or
reuse.
2. Which process is considered primary treatment?
A. Chlorination
B. Screening and sedimentation
,C. Aeration
D. Filtration
Answer: B
Rationale: Primary treatment involves physical removal of solids
through screening and settling.
3. What is the main purpose of bar screens?
A. Remove dissolved solids
B. Remove large debris
C. Add oxygen
D. Adjust pH
Answer: B
Rationale: Bar screens remove large objects such as rags and sticks from
influent wastewater.
4. Which microorganism is most important in activated sludge
systems?
A. Fish
B. Protozoa and bacteria
C. Algae only
,D. Viruses
Answer: B
Rationale: Bacteria and protozoa break down organic matter in
biological treatment systems.
5. What does BOD measure?
A. Chemical toxicity
B. Oxygen required by microorganisms to decompose organic matter
C. Hardness of water
D. pH level
Answer: B
Rationale: Biochemical Oxygen Demand indicates the amount of oxygen
needed for microbial decomposition.
6. What is the ideal pH range for most biological wastewater
treatment processes?
A. 1–3
B. 4–5
C. 6.5–8.5
D. 10–12
, Answer: C
Rationale: Most biological processes function best in a near-neutral pH
range.
7. What is the purpose of aeration tanks?
A. Remove solids by gravity
B. Add oxygen for microorganisms
C. Filter metals
D. Store sludge
Answer: B
Rationale: Aeration tanks supply oxygen to support aerobic microbial
activity.
8. What is sludge?
A. Clean water
B. Solid waste separated from wastewater
C. Chlorinated effluent
D. Rainwater runoff
Answer: B
Rationale: Sludge consists of settled solids removed during treatment.
