Operator Grade 1 Practice Exam Questions

Vermont Wastewater Treatment Facility Operator Grade 1 Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

1. The primary purpose of preliminary treatment is to:

• Remove dissolved solids
• Remove large debris and protect downstream equipment
• Stabilize organic matter
• Remove nutrients

Rationale: Preliminary treatment focuses on removing large materials such

as rags, grit, and debris to prevent equipment damage.

2. Typical bar screen spacing for a coarse screen is:

• 1–3 mm
• 3–6 mm
• 25–50 mm 1 / 4

• 60–90 mm

Rationale: Coarse screens commonly use openings of 25–50 mm to capture

large debris.

3. Grit chambers are designed primarily to remove:

• Fats, oils, and grease
• Sand, gravel, and heavy inorganic particles
• Pathogens
• Nutrients

Rationale: Grit chambers remove heavy inorganic materials that could

cause abrasion or clogging.

4. Primary clarifiers typically remove:

• Viruses
• Heavy metals
• Settleable and some floatable solids
• Ammonia

Rationale: Primary clarification settles heavier solids and removes

floatable materials before biological treatment.

5. The measurement used to determine settleable solids in wastewater is:

• BOD test
• Imhoff cone test
• pH reading
• Chlorine residual test 2 / 4

Rationale: Imhoff cones measure settleable solids after a standard 60-

minute test.

6. The main purpose of secondary treatment is to:

• Remove grit
• Remove phosphorus
• Biologically oxidize organic matter
• Thicken sludge

Rationale: Secondary treatment employs microorganisms to decompose

organic pollutants.

7. A healthy activated sludge system typically has a color that is:

• White
• Black
• Brown
• Yellow

Rationale: Chocolate-brown coloration indicates a stable biological

community.

8. Filamentous bulking is often caused by:

• High chlorine residual
• Low dissolved oxygen
• Excessive mixing
• High pH 3 / 4

Rationale: Low DO conditions favor filamentous bacteria, causing poor

settling.

9. Dissolved oxygen in aeration tanks should generally be:

• 0.1–0.5 mg/L
• 0.5–1.0 mg/L
• 1.5–3.0 mg/L
• 4.0–8.0 mg/L

Rationale: 1.5–3 mg/L provides sufficient oxygen for microbial activity.

10. A secondary clarifier’s primary purpose is to:

• Remove grit
• Separate biological solids from treated effluent
• Remove nitrogen
• Oxidize ammonia

Rationale: Secondary clarifiers settle out biological solids from activated

sludge.

11. Sludge volume index (SVI) indicates:

• Chlorine demand
• Settling characteristics of activated sludge
• Alkalinity
• pH stability

Rationale: SVI assesses how well sludge settles in the clarifier.

12. High SVI values typically indicate:

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