Practice Examination Questions And

Utah Wastewater Operator Class IV Practice Examination Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• The primary purpose of preliminary treatment in a wastewater plant is

to:

• Reduce pathogens
• Remove settleable solids
• Increase dissolved oxygen
• Protect downstream equipment

Rationale: Preliminary treatment removes debris and grit that could

damage pumps and other equipment.

2. Grit chambers are designed mainly to remove:

• Organic colloids
• Inorganic sand and silt 1 / 4

• Fats, oils, grease
• Settleable organic sludge

Rationale: Grit systems target heavy inorganic particles that settle quickly.

3. The typical detention time for primary clarifiers is:

• 5–10 minutes
• 6–8 hours
• 1.5–2.5 hours
• 10–12 hours

Rationale: Primary sedimentation requires moderate detention to settle

solids without promoting septic conditions.

4. The main mechanism for BOD removal in primary treatment is:

• Biological oxidation
• Physical settling
• Chemical precipitation
• Filtration

Rationale: Primary clarifiers remove BOD by settling particulate organics.

5. In activated sludge, sludge age (SRT) represents:

• Time solids are in aeration only
• Time water remains in aeration
• Average time biomass remains in the system
• Time solids stay in clarifier 2 / 4

Rationale: SRT measures biomass retention and controls microbial

populations.

6. Nitrification is the biological conversion of:

• Nitrogen gas to nitrate
• Ammonia to nitrate
• Nitrate to nitrogen gas
• Nitrite to ammonia

Rationale: Nitrifying bacteria oxidize ammonia first to nitrite, then to

nitrate.

7. The organisms most responsible for nitrification are:

• Protozoa
• Facultative heterotrophs
• Autotrophic bacteria
• Fungi

Rationale: Nitrifiers are autotrophic bacteria requiring oxygen and

alkalinity.

8. Low DO in aeration commonly leads to:

• Improved settleability
• Filamentous bulking
• Increased nitrification
• Increased alkalinity 3 / 4

Rationale: Filamentous organisms outcompete floc-formers under low

oxygen.

9. The PRIMARY indicator of secondary clarifier performance is:

• pH
• DO
• Sludge blanket depth
• F/M ratio

Rationale: A rising blanket shows solids carryover risk.

10. A high F/M ratio generally produces:

• Pin floc
• Robust young sludge
• Old sludge with poor activity
• Filament overgrowth

Rationale: High food availability favors young, fast-growing biomass.

11. Extended aeration systems typically operate at:

• Low SRT
• High F/M
• Long SRT
• Low MLSS

Rationale: These systems rely on long biomass retention to stabilize

wastes.

• A sudden drop in RAS flow generally results in:
• / 4