Wastewater Operator Class II Licensing Exam
Prep | Questions And Answers With Verified
Rationales | 2026/27 Qs & Ans | Digital Pdf
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1. What is the primary purpose of secondary wastewater treatment?
A. Remove large debris
B. Remove dissolved and suspended organic matter biologically
C. Increase wastewater flow
D. Add chemicals for color removal
Answer: B
Rationale: Secondary treatment uses microorganisms to biologically
degrade organic pollutants remaining after primary treatment.
2. Which operational parameter is commonly used to evaluate activated
sludge performance?
A. F/M ratio
B. Pipe diameter
C. Air pressure only
D. Detention gate size
Answer: A
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,Rationale: The Food-to-Microorganism (F/M) ratio measures the balance
between organic loading and biomass concentration.
3. What does SVI stand for in wastewater treatment?
A. Sludge Volume Index
B. Standard Velocity Indicator
C. Sewer Valve Inspection
D. Solids Variation Intake
Answer: A
Rationale: SVI evaluates settling characteristics of activated sludge.
4. Which process converts nitrate into nitrogen gas?
A. Nitrification
B. Sedimentation
C. Denitrification
D. Aeration
Answer: C
Rationale: Denitrification removes nitrogen biologically under anoxic
conditions.
5. What condition is necessary for effective nitrification?
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,A. Low dissolved oxygen
B. High grease concentration
C. Adequate dissolved oxygen
D. Zero sludge age
Answer: C
Rationale: Nitrifying bacteria require sufficient oxygen to convert
ammonia to nitrate.
6. Which bacteria are responsible for nitrification?
A. Heterotrophic bacteria only
B. Nitrosomonas and Nitrobacter
C. Coliform bacteria
D. Filamentous bacteria exclusively
Answer: B
Rationale: Nitrosomonas converts ammonia to nitrite, while Nitrobacter
converts nitrite to nitrate.
7. What is sludge age also called?
A. Hydraulic detention time
B. Solids retention time
C. Overflow rate
D. Loading factor
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, Answer: B
Rationale: Solids retention time (SRT) represents how long
microorganisms remain in the system.
8. Which process is most affected by toxic industrial discharges?
A. Preliminary screening
B. Biological treatment
C. Grit removal
D. Flow measurement
Answer: B
Rationale: Toxic substances can inhibit or kill microorganisms essential for
biological treatment.
9. What is the purpose of return activated sludge (RAS)?
A. Waste excess solids
B. Maintain microbial concentration in aeration tanks
C. Reduce pH
D. Remove chlorine
Answer: B
Rationale: RAS returns settled microorganisms to maintain biological
treatment efficiency.
© 2026 Academics_Excellence. All Rights Reserved.
Prep | Questions And Answers With Verified
Rationales | 2026/27 Qs & Ans | Digital Pdf
Download
1. What is the primary purpose of secondary wastewater treatment?
A. Remove large debris
B. Remove dissolved and suspended organic matter biologically
C. Increase wastewater flow
D. Add chemicals for color removal
Answer: B
Rationale: Secondary treatment uses microorganisms to biologically
degrade organic pollutants remaining after primary treatment.
2. Which operational parameter is commonly used to evaluate activated
sludge performance?
A. F/M ratio
B. Pipe diameter
C. Air pressure only
D. Detention gate size
Answer: A
© 2026 Academics_Excellence. All Rights Reserved.
,Rationale: The Food-to-Microorganism (F/M) ratio measures the balance
between organic loading and biomass concentration.
3. What does SVI stand for in wastewater treatment?
A. Sludge Volume Index
B. Standard Velocity Indicator
C. Sewer Valve Inspection
D. Solids Variation Intake
Answer: A
Rationale: SVI evaluates settling characteristics of activated sludge.
4. Which process converts nitrate into nitrogen gas?
A. Nitrification
B. Sedimentation
C. Denitrification
D. Aeration
Answer: C
Rationale: Denitrification removes nitrogen biologically under anoxic
conditions.
5. What condition is necessary for effective nitrification?
© 2026 Academics_Excellence. All Rights Reserved.
,A. Low dissolved oxygen
B. High grease concentration
C. Adequate dissolved oxygen
D. Zero sludge age
Answer: C
Rationale: Nitrifying bacteria require sufficient oxygen to convert
ammonia to nitrate.
6. Which bacteria are responsible for nitrification?
A. Heterotrophic bacteria only
B. Nitrosomonas and Nitrobacter
C. Coliform bacteria
D. Filamentous bacteria exclusively
Answer: B
Rationale: Nitrosomonas converts ammonia to nitrite, while Nitrobacter
converts nitrite to nitrate.
7. What is sludge age also called?
A. Hydraulic detention time
B. Solids retention time
C. Overflow rate
D. Loading factor
© 2026 Academics_Excellence. All Rights Reserved.
, Answer: B
Rationale: Solids retention time (SRT) represents how long
microorganisms remain in the system.
8. Which process is most affected by toxic industrial discharges?
A. Preliminary screening
B. Biological treatment
C. Grit removal
D. Flow measurement
Answer: B
Rationale: Toxic substances can inhibit or kill microorganisms essential for
biological treatment.
9. What is the purpose of return activated sludge (RAS)?
A. Waste excess solids
B. Maintain microbial concentration in aeration tanks
C. Reduce pH
D. Remove chlorine
Answer: B
Rationale: RAS returns settled microorganisms to maintain biological
treatment efficiency.
© 2026 Academics_Excellence. All Rights Reserved.
