South Carolina Physical/Chemical
Wastewater Operator Class A Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. The primary purpose of coagulation in wastewater treatment is:
A. Remove dissolved oxygen
B. Remove suspended solids
C. Reduce pH
D. Kill pathogens
Coagulation destabilizes colloidal particles so they can aggregate
into larger flocs for removal in sedimentation.
2. The most common coagulant used in wastewater treatment is:
A. Sodium bicarbonate
B. Aluminum sulfate (alum)
, C. Calcium chloride
D. Ferric chloride
Alum is widely used because it effectively forms flocs that settle out
suspended particles.
3. The primary function of a clarifier is:
A. Aerate the water
B. Add chemicals
C. Remove settled solids
D. Neutralize pH
Clarifiers allow suspended solids to settle out from the wastewater
stream, producing a clearer effluent.
4. In physical-chemical treatment, pH adjustment is often required to:
A. Promote algae growth
B. Increase biological activity
C. Optimize chemical reactions
D. Reduce chlorine demand
Many chemical reactions, including coagulation and precipitation,
are pH-dependent.
5. Sludge thickening is performed to:
A. Increase sludge volume
B. Reduce sludge volume
C. Neutralize sludge
, D. Aerate sludge
Thickening concentrates solids to reduce handling and disposal costs.
6. The purpose of chlorination in wastewater treatment is to:
A. Remove turbidity
B. Adjust pH
C. Disinfect the effluent
D. Settle solids
Chlorine kills or inactivates pathogenic microorganisms to protect
public health.
7. The chemical formula for hypochlorite used in disinfection is:
A. NaCl
B. HCl
C. NaOCl
D. Cl2O
Sodium hypochlorite (NaOCl) is a common disinfectant in wastewater
treatment.
8. The rate of flow through a clarifier is often expressed in:
A. mg/L
B. gallons per minute per square foot (GPM/ft²)
C. pounds per day
D. MGD
The overflow rate helps determine the settling efficiency of a
clarifier.
, 9. The purpose of a rapid mix basin in chemical treatment is to:
A. Settle solids
B. Aerate the water
C. Disperse chemicals quickly
D. Filter water
Rapid mixing ensures uniform distribution of coagulants before
flocculation.
10. The sludge volume index (SVI) is a measure of:
A. Sludge density
B. Effluent turbidity
C. Settling characteristics of sludge
D. pH stability
SVI indicates how well sludge will settle in a clarifier; high SVI
indicates poor settling.
11. Lime is added to wastewater primarily to:
A. Reduce turbidity
B. Raise pH
C. Lower alkalinity
D. Promote aeration
Lime (Ca(OH)₂) increases pH, which is important for chemical
precipitation and corrosion control.
12. Ferric chloride is primarily used for:
A. pH reduction
Wastewater Operator Class A Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationales 2026
Q&A | Instant Download Pdf
1. The primary purpose of coagulation in wastewater treatment is:
A. Remove dissolved oxygen
B. Remove suspended solids
C. Reduce pH
D. Kill pathogens
Coagulation destabilizes colloidal particles so they can aggregate
into larger flocs for removal in sedimentation.
2. The most common coagulant used in wastewater treatment is:
A. Sodium bicarbonate
B. Aluminum sulfate (alum)
, C. Calcium chloride
D. Ferric chloride
Alum is widely used because it effectively forms flocs that settle out
suspended particles.
3. The primary function of a clarifier is:
A. Aerate the water
B. Add chemicals
C. Remove settled solids
D. Neutralize pH
Clarifiers allow suspended solids to settle out from the wastewater
stream, producing a clearer effluent.
4. In physical-chemical treatment, pH adjustment is often required to:
A. Promote algae growth
B. Increase biological activity
C. Optimize chemical reactions
D. Reduce chlorine demand
Many chemical reactions, including coagulation and precipitation,
are pH-dependent.
5. Sludge thickening is performed to:
A. Increase sludge volume
B. Reduce sludge volume
C. Neutralize sludge
, D. Aerate sludge
Thickening concentrates solids to reduce handling and disposal costs.
6. The purpose of chlorination in wastewater treatment is to:
A. Remove turbidity
B. Adjust pH
C. Disinfect the effluent
D. Settle solids
Chlorine kills or inactivates pathogenic microorganisms to protect
public health.
7. The chemical formula for hypochlorite used in disinfection is:
A. NaCl
B. HCl
C. NaOCl
D. Cl2O
Sodium hypochlorite (NaOCl) is a common disinfectant in wastewater
treatment.
8. The rate of flow through a clarifier is often expressed in:
A. mg/L
B. gallons per minute per square foot (GPM/ft²)
C. pounds per day
D. MGD
The overflow rate helps determine the settling efficiency of a
clarifier.
, 9. The purpose of a rapid mix basin in chemical treatment is to:
A. Settle solids
B. Aerate the water
C. Disperse chemicals quickly
D. Filter water
Rapid mixing ensures uniform distribution of coagulants before
flocculation.
10. The sludge volume index (SVI) is a measure of:
A. Sludge density
B. Effluent turbidity
C. Settling characteristics of sludge
D. pH stability
SVI indicates how well sludge will settle in a clarifier; high SVI
indicates poor settling.
11. Lime is added to wastewater primarily to:
A. Reduce turbidity
B. Raise pH
C. Lower alkalinity
D. Promote aeration
Lime (Ca(OH)₂) increases pH, which is important for chemical
precipitation and corrosion control.
12. Ferric chloride is primarily used for:
A. pH reduction
