Virginia Wastewater Works Operator Class 3 Practice
Examination 100 Questions And Correct Answers
(100% Verified Answers) Plus Rationales Q&A
1. What does a turbidimeter measure?
A. Color
B. Turbidity (light scattering)
C. Conductivity
D. DO
Answer: B
Rationale: Turbidimeters quantify particulate cloudiness.
2. What happens when a blower fails in the aeration tank?
A. Increased DO
B. Improved settling
C. Reduced oxygen levels
D. Lower sludge production
Answer: C
Rationale: Aeration loss quickly reduces tank oxygen.
3. Which parameter is most impacted by short-circuiting in clarifiers?
A. BOD
,B. Turbidity
C. Sludge age
D. Chlorine contact time
Rationale: Short-circuiting causes solids carryover, increasing turbidity.
4. Which chemical is commonly used to dechlorinate effluent?
A. Alum
B. Polymer
C. Sulfur dioxide
D. Soda ash
Answer: C
Rationale: Sulfur dioxide neutralizes chlorine residual.
5. What is the typical range for sludge age in conventional activated
sludge?
A. 1–2 days
B. 3–15 days
C. 20–30 days
D. 40–60 days
Answer: B
Rationale: Most conventional systems operate within this solids
retention time.
6. What is the purpose of a composite sampler?
,A. Measure solids
B. Collect time-weighted or flow-weighted samples
C. Analyze chlorine
, D. Test for pathogens
Answer: B
Rationale: Composite samples represent average conditions.
7. Which condition causes septic odors in collection systems?
A. High DO
B. Anaerobic conditions
C. High pH
D. Chlorination
Answer: B
Rationale: Anaerobic wastewater forms hydrogen sulfide.
8. What instrument measures electrical conductivity?
A. DO meter
B. EC meter
C. pH meter
D. Turbidimeter
Answer: B
Rationale: EC meters quantify ionic strength.
9. What causes rising sludge in primary clarifiers?
A. Nitrification
B. Septic sludge producing gases
C. High DO
D. Low temperature
Examination 100 Questions And Correct Answers
(100% Verified Answers) Plus Rationales Q&A
1. What does a turbidimeter measure?
A. Color
B. Turbidity (light scattering)
C. Conductivity
D. DO
Answer: B
Rationale: Turbidimeters quantify particulate cloudiness.
2. What happens when a blower fails in the aeration tank?
A. Increased DO
B. Improved settling
C. Reduced oxygen levels
D. Lower sludge production
Answer: C
Rationale: Aeration loss quickly reduces tank oxygen.
3. Which parameter is most impacted by short-circuiting in clarifiers?
A. BOD
,B. Turbidity
C. Sludge age
D. Chlorine contact time
Rationale: Short-circuiting causes solids carryover, increasing turbidity.
4. Which chemical is commonly used to dechlorinate effluent?
A. Alum
B. Polymer
C. Sulfur dioxide
D. Soda ash
Answer: C
Rationale: Sulfur dioxide neutralizes chlorine residual.
5. What is the typical range for sludge age in conventional activated
sludge?
A. 1–2 days
B. 3–15 days
C. 20–30 days
D. 40–60 days
Answer: B
Rationale: Most conventional systems operate within this solids
retention time.
6. What is the purpose of a composite sampler?
,A. Measure solids
B. Collect time-weighted or flow-weighted samples
C. Analyze chlorine
, D. Test for pathogens
Answer: B
Rationale: Composite samples represent average conditions.
7. Which condition causes septic odors in collection systems?
A. High DO
B. Anaerobic conditions
C. High pH
D. Chlorination
Answer: B
Rationale: Anaerobic wastewater forms hydrogen sulfide.
8. What instrument measures electrical conductivity?
A. DO meter
B. EC meter
C. pH meter
D. Turbidimeter
Answer: B
Rationale: EC meters quantify ionic strength.
9. What causes rising sludge in primary clarifiers?
A. Nitrification
B. Septic sludge producing gases
C. High DO
D. Low temperature
