Exam Practice Questions And Correct

Wastewater Operator Class I Licensing Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• The primary purpose of preliminary treatment in a wastewater

treatment plant is to:

• Remove dissolved solids
• Remove pathogens
• Remove large debris and grit
• Reduce nutrients

Rationale: Preliminary treatment screens and removes grit and large

objects to protect equipment downstream.

• The main function of primary clarifiers is to: 1 / 3

• Aerate wastewater
• Remove settleable solids and floatable materials
• Reduce ammonia
• Break down organics biologically

Rationale: Primary clarifiers allow solids to settle and scum to float for

removal.

3. BOD stands for:

• Biological Organism Demand
• Biodegradable Oxygen Determination
• Biochemical Oxygen Demand
• 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:

• 0–0.5 mg/L
• 1–3 mg/L
• 6–9 mg/L
• 10–12 mg/L

Rationale: Maintaining 1–3 mg/L DO supports aerobic biological activity.

5. The purpose of grit removal is to:

• Remove fats, oils, and grease
• Improve sludge digestion 2 / 3

• Reduce nitrogen
• Protect pumps and mechanical equipment

Rationale: Grit is abrasive and damages equipment.

6. Chlorination in wastewater treatment is mainly used for:

• Sludge thickening
• Disinfection
• Odor control only
• Nutrient removal

Rationale: Chlorine is primarily for pathogen reduction before discharge.

7. Trickling filters are:

• Chemical treatment units
• Attached-growth biological systems
• Anaerobic digesters
• 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:

• Low oxygen
• Toxic gases
• Flammable gases
• All of the above

Rationale: Confined spaces pose multiple atmospheric hazards.

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