Wastewater Operator Class I Licensing
Exam Practice Questions And Correct
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Rationales 2026 Q&A | Instant
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1. The primary purpose of preliminary treatment in a wastewater
treatment plant is to:
A. Remove dissolved solids
B. Remove pathogens
C. Remove large debris and grit
D. Reduce nutrients
Rationale: Preliminary treatment screens and removes grit and large
objects to protect equipment downstream.
2. The main function of primary clarifiers is to:
,A. Aerate wastewater
B. Remove settleable solids and floatable materials
C. Reduce ammonia
D. Break down organics biologically
Rationale: Primary clarifiers allow solids to settle and scum to float for
removal.
3. BOD stands for:
A. Biological Organism Demand
B. Biodegradable Oxygen Determination
C. Biochemical Oxygen Demand
D. Brominated Organic Demand
Rationale: BOD measures oxygen required by microorganisms to degrade
organics.
4. A typical dissolved oxygen (DO) range in an aeration tank is:
A. 0–0.5 mg/L
B. 1–3 mg/L
C. 6–9 mg/L
D. 10–12 mg/L
Rationale: Maintaining 1–3 mg/L DO supports aerobic biological activity.
5. The purpose of grit removal is to:
A. Remove fats, oils, and grease
B. Improve sludge digestion
, C. Reduce nitrogen
D. Protect pumps and mechanical equipment
Rationale: Grit is abrasive and damages equipment.
6. Chlorination in wastewater treatment is mainly used for:
A. Sludge thickening
B. Disinfection
C. Odor control only
D. Nutrient removal
Rationale: Chlorine is primarily for pathogen reduction before discharge.
7. Trickling filters are:
A. Chemical treatment units
B. Attached-growth biological systems
C. Anaerobic digesters
D. Filtration systems for drinking water
Rationale: Microbes grow on media and degrade organics as wastewater
trickles over them.
8. A confined space atmosphere may be unsafe due to:
A. Low oxygen
B. Toxic gases
C. Flammable gases
D. All of the above
Rationale: Confined spaces pose multiple atmospheric hazards.
Exam Practice Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. The primary purpose of preliminary treatment in a wastewater
treatment plant is to:
A. Remove dissolved solids
B. Remove pathogens
C. Remove large debris and grit
D. Reduce nutrients
Rationale: Preliminary treatment screens and removes grit and large
objects to protect equipment downstream.
2. The main function of primary clarifiers is to:
,A. Aerate wastewater
B. Remove settleable solids and floatable materials
C. Reduce ammonia
D. Break down organics biologically
Rationale: Primary clarifiers allow solids to settle and scum to float for
removal.
3. BOD stands for:
A. Biological Organism Demand
B. Biodegradable Oxygen Determination
C. Biochemical Oxygen Demand
D. Brominated Organic Demand
Rationale: BOD measures oxygen required by microorganisms to degrade
organics.
4. A typical dissolved oxygen (DO) range in an aeration tank is:
A. 0–0.5 mg/L
B. 1–3 mg/L
C. 6–9 mg/L
D. 10–12 mg/L
Rationale: Maintaining 1–3 mg/L DO supports aerobic biological activity.
5. The purpose of grit removal is to:
A. Remove fats, oils, and grease
B. Improve sludge digestion
, C. Reduce nitrogen
D. Protect pumps and mechanical equipment
Rationale: Grit is abrasive and damages equipment.
6. Chlorination in wastewater treatment is mainly used for:
A. Sludge thickening
B. Disinfection
C. Odor control only
D. Nutrient removal
Rationale: Chlorine is primarily for pathogen reduction before discharge.
7. Trickling filters are:
A. Chemical treatment units
B. Attached-growth biological systems
C. Anaerobic digesters
D. Filtration systems for drinking water
Rationale: Microbes grow on media and degrade organics as wastewater
trickles over them.
8. A confined space atmosphere may be unsafe due to:
A. Low oxygen
B. Toxic gases
C. Flammable gases
D. All of the above
Rationale: Confined spaces pose multiple atmospheric hazards.
