Class 1 Exam Practice Questions And

Virginia Wastewater Works Operator Class 1 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of secondary treatment in a wastewater

plant?

• Remove grit
• Remove pathogens
• Remove dissolved and colloidal organic matter
• Remove heavy metals

Rationale: Secondary treatment focuses on biological degradation of

organics.

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• What is the typical range for the Food-to-Mass (F/M) ratio in a

conventional activated sludge system?

A. 0.1–0.2

B. 0.2–0.4

C. 0.2–0.5

D. 0.5–0.8

Rationale: Conventional activated sludge commonly operates around 0.2–

0.5.

• What does BOD measure?
• Suspended solids concentration
• Oxygen required by microorganisms to stabilize organics
• Chlorine demand
• Nutrient concentration

Rationale: BOD reflects biological oxygen use to break down organic

matter.

• In anaerobic digestion, which gas is produced in the highest quantity?
• Nitrogen
• Hydrogen sulfide
• Methane
• Carbon monoxide 2 / 4

Rationale: Methane is the dominant gas produced by anaerobic

microorganisms.

• Which indicator is used to assess nitrification efficiency?

A. BOD

• Ammonia concentration

C. TSS

• Chlorine residual

Rationale: Lower ammonia concentrations indicate successful nitrification.

• What is the primary function of a grit chamber?
• Remove pathogens
• Remove heavy inorganic particles
• Remove dissolved solids
• Remove floatable oils

Rationale: Grit chambers settle dense materials like sand and gravel.

• What is the typical dissolved oxygen target for activated sludge aeration

basins?

• 0.5 mg/L
• 1.0 mg/L 3 / 4

• 2.0 mg/L
• 5.0 mg/L

Rationale: Around 2 mg/L supports aerobic microbial activity.

• Which process converts ammonia to nitrate?
• Denitrification
• Nitrification
• Fermentation
• Sludge stabilization

Rationale: Nitrifying bacteria oxidize ammonia to nitrite and nitrate.

• What does the Sludge Volume Index (SVI) measure?
• Chlorine demand
• Influent BOD
• Settling characteristics of activated sludge
• Grit load

Rationale: SVI indicates sludge compaction and settling ability.

• What is the typical pH range for nitrification?

A. 4–5

• 5–6
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