Class 2 Exam Practice Questions And

Virginia Wastewater Works Operator Class 2 Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

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

plant?

• To remove dissolved solids
• To remove large solids and debris
• To reduce biochemical oxygen demand
• To disinfect the wastewater

Rationale: Screening removes large solids such as sticks, rags, and other

debris that could damage equipment or interfere with treatment processes.

• Which of the following is a common method of primary clarification?
• Trickling filter 1 / 4

• Activated sludge
• Sedimentation tank
• Chlorination

Rationale: Sedimentation tanks allow heavier solids to settle, removing them

from the wastewater before secondary treatment.

3. BOD (Biochemical Oxygen Demand) primarily measures:

• The amount of oxygen dissolved in water
• The amount of oxygen required by microorganisms to decompose

organic matter

• The chemical oxygen content
• The pH of wastewater

Rationale: BOD indicates the organic load in wastewater, showing how

much oxygen microbes need to break it down.

• What is the primary function of aeration in an activated sludge system?
• To settle solids
• To remove nutrients
• To provide oxygen for microbial decomposition
• To disinfect wastewater

Rationale: Aeration supplies oxygen that bacteria need to metabolize

organic material in the wastewater.

5. Nitrification is a process that converts:

• Nitrogen gas to nitrate 2 / 4

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

Rationale: Nitrification is the aerobic conversion of ammonia to nitrate by

nitrifying bacteria.

6. Denitrification requires:

• Aerobic conditions
• Anaerobic conditions
• Chlorination
• High pH only

Rationale: Denitrification is an anaerobic process in which nitrate is

converted to nitrogen gas.

7. The purpose of a grit chamber is to:

• Remove large debris
• Remove sand, gravel, and other heavy inorganic solids
• Reduce BOD
• Disinfect wastewater

Rationale: Grit chambers remove heavy inorganic particles that could

damage pumps and other equipment.

8. In wastewater, TSS stands for:

• Total soluble salts
• Total suspended solids 3 / 4

• Total sanitary sludge
• Total sulfate solution

Rationale: TSS measures the amount of solid particles suspended in

wastewater, an important parameter for treatment efficiency.

• Which disinfectant is most commonly used in wastewater treatment?
• Iodine
• Ozone
• Chlorine
• Hydrogen peroxide

Rationale: Chlorine is widely used because it effectively kills pathogens and

is cost-efficient.

10. Sludge thickening primarily:

• Removes all pathogens
• Reduces water content of sludge
• Reduces BOD
• Increases dissolved oxygen

Rationale: Thickening concentrates solids to reduce volume before further

treatment or disposal.

11. The pH range suitable for most activated sludge systems is:

A. 4–5

• 6–7
• / 4