WASTEWATER OPERATOR CLASS C EXAM PRACTICE
REVIEW FINAL EXAM PRACTICE QUESTIONS WITH CLEAR
EXPLANATIONS | UPDATED 2025–2026
When Chlorine is combined with water what type of pipe should be used?
A. Ductile iron
B. Asbestos concrete
C. PVC
D. Carbon Steel - correct answer -C. PVC
A good settling sludge would consist of what type of protozoa?
A. Rotifers and nematodes
B. Amoebas and Flagellates
C. Stalked ciliates and mastagoria
D. Free swimmers and stalk ciliates - correct answer -D. Free swimmers and stalk ciliates
What is Phenolphylein used for in titration
A. Oxidizer
B. Indicator
C. Acid reducer to lower pH
D. Applicator - correct answer -B. Indicator
,Your plant has an influent of 220 BOD and 163 TSS, and an effluent of 10 BOD, and 6 TSS. What
is the BOD removal efficiency in your plant?
A. 92%
B. 94%
C. 95%
D. 96% - correct answer -C. 95%
You suspect your anaerobic digester is going sour. What is the best way to verify its condition?
A. pH
B. Foam type
C. VA/ALK ratio
D. DO - correct answer -C. VA/ALK ratio
Before operating any piece of equipment what should be done?
A. Lock out Tag out (remember, safety first!)
B. Read O & M manual
C. Read manufacturers manual
D. Notify supervisor - correct answer -C. Read manufacturers manual
Detritus is noticed in your grit channel. What is the problem?
A. Velocity too fast with short D/T
B. Velocity too low with long D/T
, C. Short circuiting
D. Density currents - correct answer -B. Velocity too low with long D/T
What is considered normal operation of an aerobic digester?
A. Fill react
B. Skim off foam when needed
C. Settle and Decant as needed
D. Feed only during low flow or constant when the sun is out - correct answer -C. Settle and
Decant as needed
A plant with a flow of 1 MGD should be monitored
A. Continuously
B. Intermittently
C. Daily
D. Every four hours depending on surface load - correct answer -A. Continuously
What do total solids consist of?
A. Dissolved and settleable
B. Floatable and settlable
C. Suspended and dissolved
D. Settlable and nonsettleable - correct answer -C. Suspended and dissolved
What would cause excessive wear on bearing?
REVIEW FINAL EXAM PRACTICE QUESTIONS WITH CLEAR
EXPLANATIONS | UPDATED 2025–2026
When Chlorine is combined with water what type of pipe should be used?
A. Ductile iron
B. Asbestos concrete
C. PVC
D. Carbon Steel - correct answer -C. PVC
A good settling sludge would consist of what type of protozoa?
A. Rotifers and nematodes
B. Amoebas and Flagellates
C. Stalked ciliates and mastagoria
D. Free swimmers and stalk ciliates - correct answer -D. Free swimmers and stalk ciliates
What is Phenolphylein used for in titration
A. Oxidizer
B. Indicator
C. Acid reducer to lower pH
D. Applicator - correct answer -B. Indicator
,Your plant has an influent of 220 BOD and 163 TSS, and an effluent of 10 BOD, and 6 TSS. What
is the BOD removal efficiency in your plant?
A. 92%
B. 94%
C. 95%
D. 96% - correct answer -C. 95%
You suspect your anaerobic digester is going sour. What is the best way to verify its condition?
A. pH
B. Foam type
C. VA/ALK ratio
D. DO - correct answer -C. VA/ALK ratio
Before operating any piece of equipment what should be done?
A. Lock out Tag out (remember, safety first!)
B. Read O & M manual
C. Read manufacturers manual
D. Notify supervisor - correct answer -C. Read manufacturers manual
Detritus is noticed in your grit channel. What is the problem?
A. Velocity too fast with short D/T
B. Velocity too low with long D/T
, C. Short circuiting
D. Density currents - correct answer -B. Velocity too low with long D/T
What is considered normal operation of an aerobic digester?
A. Fill react
B. Skim off foam when needed
C. Settle and Decant as needed
D. Feed only during low flow or constant when the sun is out - correct answer -C. Settle and
Decant as needed
A plant with a flow of 1 MGD should be monitored
A. Continuously
B. Intermittently
C. Daily
D. Every four hours depending on surface load - correct answer -A. Continuously
What do total solids consist of?
A. Dissolved and settleable
B. Floatable and settlable
C. Suspended and dissolved
D. Settlable and nonsettleable - correct answer -C. Suspended and dissolved
What would cause excessive wear on bearing?
