WasteWater Operator class C exam practice review
2026/2027 version
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
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
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?
A. Misalignment
B. Reduced Oil due to low viscosity
C. Blow seal
D. Over tubercation- correct answer>>>A. Misalignment
Amperometric titration is used to measure
A. Dissolved solids
B. Chlorine residual
C. Colloids
D. Emulsions- correct answer>>>B. Chlorine residual
, What growth phase is an aerobic digester operated in.
A. Log
B. Lag
C. Endogenous respiration
D. Declining phase- correct answer>>>C. Endogenous respiration
If excessive pressure builds up in a chlorine tank due to excessive heat. What will
prevent explosions?
A. Valve seat adjustments
B. Heat reducing valve
C. Fusible plug
D. Check valve- correct answer>>>C. Fusible plug
You notice that your bearings are excessively hot on a pump, why?
A. Ambient temperature too high
B. Over lubrication
C. Oil seal blown
D. Discharge rate too low- correct answer>>>B. Over lubrication
Where can you gain access for collection system maintenance?
A. Lift station
B. Force main
C. Man hole
D. Gravity main- correct answer>>>C. Man hole
Low DO and nutrient deficiency will promote the growth of what?
A. Rotifers
B. Filamentous bacteria
C. Spirillium
D. Amoebas- correct answer>>>B. Filamentous bacteria
When charging a lead-acid type battery for a composite sampler, what dangerous gas
could be produced?
A. Hydrogen
B. Oxygen
C. Hydrogen sulfide
D. Cyanide- correct answer>>>A. Hydrogen
What is the best method in dealing with a chemical spill?
2026/2027 version
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
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
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?
A. Misalignment
B. Reduced Oil due to low viscosity
C. Blow seal
D. Over tubercation- correct answer>>>A. Misalignment
Amperometric titration is used to measure
A. Dissolved solids
B. Chlorine residual
C. Colloids
D. Emulsions- correct answer>>>B. Chlorine residual
, What growth phase is an aerobic digester operated in.
A. Log
B. Lag
C. Endogenous respiration
D. Declining phase- correct answer>>>C. Endogenous respiration
If excessive pressure builds up in a chlorine tank due to excessive heat. What will
prevent explosions?
A. Valve seat adjustments
B. Heat reducing valve
C. Fusible plug
D. Check valve- correct answer>>>C. Fusible plug
You notice that your bearings are excessively hot on a pump, why?
A. Ambient temperature too high
B. Over lubrication
C. Oil seal blown
D. Discharge rate too low- correct answer>>>B. Over lubrication
Where can you gain access for collection system maintenance?
A. Lift station
B. Force main
C. Man hole
D. Gravity main- correct answer>>>C. Man hole
Low DO and nutrient deficiency will promote the growth of what?
A. Rotifers
B. Filamentous bacteria
C. Spirillium
D. Amoebas- correct answer>>>B. Filamentous bacteria
When charging a lead-acid type battery for a composite sampler, what dangerous gas
could be produced?
A. Hydrogen
B. Oxygen
C. Hydrogen sulfide
D. Cyanide- correct answer>>>A. Hydrogen
What is the best method in dealing with a chemical spill?
