Wastewater Operator Class II 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 wastewater treatment?
A. To increase water salinity
B. To remove contaminants from wastewater
C. To produce drinking water directly
D. To generate electricity
Correct Answer: B
Rationale: The main goal of wastewater treatment is to remove physical,
chemical, and biological contaminants before discharge or reuse.
2. Which process removes large solids from wastewater?
A. Chlorination
B. Sedimentation
C. Screening
D. Aeration
Correct Answer: C
Rationale: Screening removes large debris such as sticks, rags, and plastics
early in treatment.
,3. What is the function of grit chambers?
A. Remove dissolved solids
B. Remove heavy inorganic particles like sand
C. Add oxygen to wastewater
D. Kill bacteria
Correct Answer: B
Rationale: Grit chambers remove heavy inorganic materials like sand and
gravel to prevent equipment damage.
4. Which microorganism is most important in activated sludge systems?
A. Viruses
B. Protozoa and bacteria
C. Helminths
D. Algae only
Correct Answer: B
Rationale: Bacteria and protozoa break down organic matter in biological
treatment processes.
5. What is biochemical oxygen demand (BOD)?
A. Amount of oxygen in water
B. Oxygen required to chemically oxidize metals
C. Oxygen required by microorganisms to decompose organic matter
D. Chlorine demand in water
Correct Answer: C
Rationale: BOD measures the oxygen used by microbes to break down
organic waste.
6. What does primary treatment remove?
A. Dissolved salts
, B. Large solids and settleable organic matter
C. Nitrogen compounds
D. Pathogens only
Correct Answer: B
Rationale: Primary treatment removes settleable solids through
sedimentation.
7. Secondary treatment primarily targets:
A. Metals
B. Organic matter
C. Plastic waste
D. Sand and grit
Correct Answer: B
Rationale: Secondary treatment uses biological processes to remove
dissolved and suspended organic matter.
8. What is the role of aeration tanks?
A. Add chlorine
B. Provide oxygen for microbial activity
C. Remove sludge
D. Filter solids
Correct Answer: B
Rationale: Aeration tanks supply oxygen to support aerobic bacteria.
9. What is sludge?
A. Clean water
B. Treated effluent
C. Settled solids from wastewater
D. Chemical disinfectant
Exam Practice Test Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
1. What is the primary purpose of wastewater treatment?
A. To increase water salinity
B. To remove contaminants from wastewater
C. To produce drinking water directly
D. To generate electricity
Correct Answer: B
Rationale: The main goal of wastewater treatment is to remove physical,
chemical, and biological contaminants before discharge or reuse.
2. Which process removes large solids from wastewater?
A. Chlorination
B. Sedimentation
C. Screening
D. Aeration
Correct Answer: C
Rationale: Screening removes large debris such as sticks, rags, and plastics
early in treatment.
,3. What is the function of grit chambers?
A. Remove dissolved solids
B. Remove heavy inorganic particles like sand
C. Add oxygen to wastewater
D. Kill bacteria
Correct Answer: B
Rationale: Grit chambers remove heavy inorganic materials like sand and
gravel to prevent equipment damage.
4. Which microorganism is most important in activated sludge systems?
A. Viruses
B. Protozoa and bacteria
C. Helminths
D. Algae only
Correct Answer: B
Rationale: Bacteria and protozoa break down organic matter in biological
treatment processes.
5. What is biochemical oxygen demand (BOD)?
A. Amount of oxygen in water
B. Oxygen required to chemically oxidize metals
C. Oxygen required by microorganisms to decompose organic matter
D. Chlorine demand in water
Correct Answer: C
Rationale: BOD measures the oxygen used by microbes to break down
organic waste.
6. What does primary treatment remove?
A. Dissolved salts
, B. Large solids and settleable organic matter
C. Nitrogen compounds
D. Pathogens only
Correct Answer: B
Rationale: Primary treatment removes settleable solids through
sedimentation.
7. Secondary treatment primarily targets:
A. Metals
B. Organic matter
C. Plastic waste
D. Sand and grit
Correct Answer: B
Rationale: Secondary treatment uses biological processes to remove
dissolved and suspended organic matter.
8. What is the role of aeration tanks?
A. Add chlorine
B. Provide oxygen for microbial activity
C. Remove sludge
D. Filter solids
Correct Answer: B
Rationale: Aeration tanks supply oxygen to support aerobic bacteria.
9. What is sludge?
A. Clean water
B. Treated effluent
C. Settled solids from wastewater
D. Chemical disinfectant
