South Carolina Physical/Chemical
Wastewater Operator Class D Exam Practice
Questions and Answers Plus Rationales
Latest 2026/27
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 answersC. 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 answersD. 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 answersB. 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 answersC. 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 answersC. 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 answersC. 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 answersB. 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 answersC. 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 answersA. Continuously
What do total solids consist of?
A. Dissolved and settleable
B. Floatable and settlable
C. Suspended and dissolved
D. Settlable and nonsettleable - correct answersC. 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 answersA. Misalignment
Amperometric titration is used to measure
A. Dissolved solids
, B. Chlorine residual
C. Colloids
D. Emulsions - correct answersB. Chlorine residual
What growth phase is an aerobic digester operated in.
A. Log
B. Lag
C. Endogenous respiration
D. Declining phase - correct answersC. 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 answersC. 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 answersB. Over lubrication
Where can you gain access for collection system maintenance?
A. Lift station
B. Force main
C. Man hole
D. Gravity main - correct answersC. Man hole
Low DO and nutrient deficiency will promote the growth of what?
A. Rotifers
B. Filamentous bacteria
C. Spirillium
D. Amoebas - correct answersB. 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
Wastewater Operator Class D Exam Practice
Questions and Answers Plus Rationales
Latest 2026/27
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 answersC. 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 answersD. 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 answersB. 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 answersC. 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 answersC. 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 answersC. 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 answersB. 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 answersC. 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 answersA. Continuously
What do total solids consist of?
A. Dissolved and settleable
B. Floatable and settlable
C. Suspended and dissolved
D. Settlable and nonsettleable - correct answersC. 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 answersA. Misalignment
Amperometric titration is used to measure
A. Dissolved solids
, B. Chlorine residual
C. Colloids
D. Emulsions - correct answersB. Chlorine residual
What growth phase is an aerobic digester operated in.
A. Log
B. Lag
C. Endogenous respiration
D. Declining phase - correct answersC. 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 answersC. 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 answersB. Over lubrication
Where can you gain access for collection system maintenance?
A. Lift station
B. Force main
C. Man hole
D. Gravity main - correct answersC. Man hole
Low DO and nutrient deficiency will promote the growth of what?
A. Rotifers
B. Filamentous bacteria
C. Spirillium
D. Amoebas - correct answersB. 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
