Wastewater Operator Class C Exam
Practice Review Questions and
Answers | Latest Version | 2025/2026 |
Correct & Verified
Which measurement is most important to protect fish in receiving waters?
A. pH
✔✔B. Dissolved oxygen
C. Chlorine residual
D. TSS
What is the function of an influent pump station?
✔✔A. Lift wastewater to higher elevation
B. Add chlorine
C. Remove pathogens
D. Reduce nitrogen
Which device prevents rags and trash from damaging pumps?
✔✔A. Bar screen
1
,B. Grit chamber
C. Primary clarifier
D. Aeration tank
What is the main purpose of primary treatment?
A. Destroy pathogens
✔✔B. Settle solids and floatables
C. Supply oxygen
D. Remove chlorine
Which test measures the amount of biodegradable organic matter?
✔✔A. BOD test
B. TSS test
C. Alkalinity test
D. Hardness test
What happens if sludge is not removed from a clarifier?
✔✔A. Solids wash out into effluent
2
,B. pH increases
C. Chlorine demand drops
D. Flow decreases
Which type of bacteria carry out nitrification?
A. Anaerobic bacteria
✔✔B. Nitrifying bacteria
C. Sulfate-reducing bacteria
D. Fermenting bacteria
What is the most common safety hazard with chlorine gas?
✔✔A. Respiratory damage
B. Explosion risk
C. Electrical shock
D. Heat burns
Why is dissolved oxygen important in activated sludge?
A. Neutralizes alkalinity
3
, ✔✔B. Supports microorganism respiration
C. Removes grit
D. Reduces chlorine
What is the primary purpose of secondary treatment?
✔✔A. Biologically remove organic matter
B. Filter heavy metals
C. Increase alkalinity
D. Add grit
What is the typical detention time for an aeration basin?
A. 10–20 minutes
✔✔B. 4–8 hours
C. 24–36 hours
D. 72 hours
What is the purpose of secondary clarifiers?
✔✔A. Settle biological solids
4
Practice Review Questions and
Answers | Latest Version | 2025/2026 |
Correct & Verified
Which measurement is most important to protect fish in receiving waters?
A. pH
✔✔B. Dissolved oxygen
C. Chlorine residual
D. TSS
What is the function of an influent pump station?
✔✔A. Lift wastewater to higher elevation
B. Add chlorine
C. Remove pathogens
D. Reduce nitrogen
Which device prevents rags and trash from damaging pumps?
✔✔A. Bar screen
1
,B. Grit chamber
C. Primary clarifier
D. Aeration tank
What is the main purpose of primary treatment?
A. Destroy pathogens
✔✔B. Settle solids and floatables
C. Supply oxygen
D. Remove chlorine
Which test measures the amount of biodegradable organic matter?
✔✔A. BOD test
B. TSS test
C. Alkalinity test
D. Hardness test
What happens if sludge is not removed from a clarifier?
✔✔A. Solids wash out into effluent
2
,B. pH increases
C. Chlorine demand drops
D. Flow decreases
Which type of bacteria carry out nitrification?
A. Anaerobic bacteria
✔✔B. Nitrifying bacteria
C. Sulfate-reducing bacteria
D. Fermenting bacteria
What is the most common safety hazard with chlorine gas?
✔✔A. Respiratory damage
B. Explosion risk
C. Electrical shock
D. Heat burns
Why is dissolved oxygen important in activated sludge?
A. Neutralizes alkalinity
3
, ✔✔B. Supports microorganism respiration
C. Removes grit
D. Reduces chlorine
What is the primary purpose of secondary treatment?
✔✔A. Biologically remove organic matter
B. Filter heavy metals
C. Increase alkalinity
D. Add grit
What is the typical detention time for an aeration basin?
A. 10–20 minutes
✔✔B. 4–8 hours
C. 24–36 hours
D. 72 hours
What is the purpose of secondary clarifiers?
✔✔A. Settle biological solids
4
