Wastewater Operator Class A Exam

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:

• Remove dissolved oxygen
• Remove suspended solids
• Reduce pH
• 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:

• Sodium bicarbonate
• Aluminum sulfate (alum) 1 / 4

• Calcium chloride
• Ferric chloride

Alum is widely used because it effectively forms flocs that settle out suspended particles.

3. The primary function of a clarifier is:

• Aerate the water
• Add chemicals
• Remove settled solids
• 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:

• Promote algae growth
• Increase biological activity
• Optimize chemical reactions
• Reduce chlorine demand

Many chemical reactions, including coagulation and precipitation, are pH-dependent.

5. Sludge thickening is performed to:

• Increase sludge volume
• Reduce sludge volume
• Neutralize sludge 2 / 4

• Aerate sludge

Thickening concentrates solids to reduce handling and disposal costs.

6. The purpose of chlorination in wastewater treatment is to:

• Remove turbidity
• Adjust pH
• Disinfect the effluent
• Settle solids

Chlorine kills or inactivates pathogenic microorganisms to protect public health.

7. The chemical formula for hypochlorite used in disinfection is:

• NaCl
• HCl
• NaOCl
• Cl2O

Sodium hypochlorite (NaOCl) is a common disinfectant in wastewater treatment.

8. The rate of flow through a clarifier is often expressed in:

• mg/L
• gallons per minute per square foot (GPM/ft²)
• pounds per day

D. MGD

The overflow rate helps determine the settling efficiency of a clarifier. 3 / 4

9. The purpose of a rapid mix basin in chemical treatment is to:

• Settle solids
• Aerate the water
• Disperse chemicals quickly
• Filter water

Rapid mixing ensures uniform distribution of coagulants before flocculation.

10. The sludge volume index (SVI) is a measure of:

• Sludge density
• Effluent turbidity
• Settling characteristics of sludge
• 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:

• Reduce turbidity
• Raise pH
• Lower alkalinity
• Promote aeration

Lime (Ca(OH)₂) increases pH, which is important for chemical precipitation and corrosion control.

12. Ferric chloride is primarily used for:

• pH reduction
• / 4