Virginia Wastewater Operator Class 2
License Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
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1. Which of the following processes is primarily responsible for the
biological removal of organic matter in a wastewater treatment plant?
A. Screening
B. Sedimentation
C. Chlorination
D. Activated sludge process
Answer: D. Activated sludge process
Rationale: The activated sludge process uses microorganisms to
biologically degrade organic pollutants, making it the core secondary
treatment method in wastewater systems.
2. In a wastewater treatment facility, what is the primary purpose of
preliminary treatment?
A. Remove dissolved solids
B. Remove large debris and grit
C. Kill pathogens
D. Stabilize sludge
Answer: B. Remove large debris and grit
, Rationale: Preliminary treatment focuses on removing coarse
materials like rags, sticks, and grit to protect downstream equipment
and processes.
3. Which parameter is most commonly used to measure the organic
strength of wastewater?
A. pH
B. Dissolved oxygen
C. Biochemical Oxygen Demand (BOD)
D. Turbidity
Answer: C. Biochemical Oxygen Demand (BOD)
Rationale: BOD measures the amount of oxygen required by
microorganisms to decompose organic matter, indicating wastewater
strength.
4. What is the main function of a secondary clarifier?
A. Remove grit
B. Settle biological solids
C. Disinfect effluent
D. Aerate wastewater
Answer: B. Settle biological solids
Rationale: Secondary clarifiers allow biological floc from the aeration
process to settle, separating treated water from biomass.
5. Which piece of equipment is used to add oxygen to wastewater in the
activated sludge process?
A. Clarifier
B. Aerator
C. Pump
D. Filter press
Answer: B. Aerator
, Rationale: Aerators supply oxygen necessary for aerobic
microorganisms to break down organic pollutants.
6. What is the primary purpose of disinfection in wastewater treatment?
A. Remove solids
B. Reduce nutrients
C. Kill pathogenic organisms
D. Adjust pH
Answer: C. Kill pathogenic organisms
Rationale: Disinfection eliminates harmful microorganisms before
effluent is discharged into the environment.
7. Which chemical is commonly used for wastewater disinfection?
A. Alum
B. Chlorine
C. Lime
D. Methanol
Answer: B. Chlorine
Rationale: Chlorine is widely used due to its effectiveness in killing
pathogens and its residual disinfecting capability.
8. What does MLSS stand for in wastewater treatment?
A. Maximum Liquid Suspended Solids
B. Mixed Liquor Suspended Solids
C. Minimum Level Settled Solids
D. Mechanical Liquid Sludge System
Answer: B. Mixed Liquor Suspended Solids
Rationale: MLSS refers to the concentration of suspended solids in the
aeration tank, including microorganisms and organic matter.
9. Which process removes ammonia from wastewater biologically?
A. Denitrification
B. Nitrification
License Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationale 2026 Q&A| Instant Download
1. Which of the following processes is primarily responsible for the
biological removal of organic matter in a wastewater treatment plant?
A. Screening
B. Sedimentation
C. Chlorination
D. Activated sludge process
Answer: D. Activated sludge process
Rationale: The activated sludge process uses microorganisms to
biologically degrade organic pollutants, making it the core secondary
treatment method in wastewater systems.
2. In a wastewater treatment facility, what is the primary purpose of
preliminary treatment?
A. Remove dissolved solids
B. Remove large debris and grit
C. Kill pathogens
D. Stabilize sludge
Answer: B. Remove large debris and grit
, Rationale: Preliminary treatment focuses on removing coarse
materials like rags, sticks, and grit to protect downstream equipment
and processes.
3. Which parameter is most commonly used to measure the organic
strength of wastewater?
A. pH
B. Dissolved oxygen
C. Biochemical Oxygen Demand (BOD)
D. Turbidity
Answer: C. Biochemical Oxygen Demand (BOD)
Rationale: BOD measures the amount of oxygen required by
microorganisms to decompose organic matter, indicating wastewater
strength.
4. What is the main function of a secondary clarifier?
A. Remove grit
B. Settle biological solids
C. Disinfect effluent
D. Aerate wastewater
Answer: B. Settle biological solids
Rationale: Secondary clarifiers allow biological floc from the aeration
process to settle, separating treated water from biomass.
5. Which piece of equipment is used to add oxygen to wastewater in the
activated sludge process?
A. Clarifier
B. Aerator
C. Pump
D. Filter press
Answer: B. Aerator
, Rationale: Aerators supply oxygen necessary for aerobic
microorganisms to break down organic pollutants.
6. What is the primary purpose of disinfection in wastewater treatment?
A. Remove solids
B. Reduce nutrients
C. Kill pathogenic organisms
D. Adjust pH
Answer: C. Kill pathogenic organisms
Rationale: Disinfection eliminates harmful microorganisms before
effluent is discharged into the environment.
7. Which chemical is commonly used for wastewater disinfection?
A. Alum
B. Chlorine
C. Lime
D. Methanol
Answer: B. Chlorine
Rationale: Chlorine is widely used due to its effectiveness in killing
pathogens and its residual disinfecting capability.
8. What does MLSS stand for in wastewater treatment?
A. Maximum Liquid Suspended Solids
B. Mixed Liquor Suspended Solids
C. Minimum Level Settled Solids
D. Mechanical Liquid Sludge System
Answer: B. Mixed Liquor Suspended Solids
Rationale: MLSS refers to the concentration of suspended solids in the
aeration tank, including microorganisms and organic matter.
9. Which process removes ammonia from wastewater biologically?
A. Denitrification
B. Nitrification
