Treatment Operator Practice Exam

Physical-Chemical Industrial Waste Treatment Operator Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

1. The main purpose of coagulation in industrial wastewater treatment is to:

• Remove dissolved gases
• Destabilize colloidal particles
• Neutralize acidity
• Increase alkalinity

Rationale: Coagulation neutralizes charges on colloids, allowing particles

to clump for easier removal.

• Which chemical is most commonly used as a coagulant?
• Sodium hydroxide
• Aluminum sulfate (alum) 1 / 4

• Sodium bicarbonate
• Calcium carbonate

Rationale: Aluminum sulfate is widely used due to its effectiveness and

cost efficiency.

3. The pH range most effective for alum coagulation is:

A. 3–4

B. 5–6

C. 6–7

D. 9–10

Rationale: Alum performs optimally near neutral pH for maximum charge

neutralization.

4. The term “flocculation” refers to:

• Settling of solids
• Gentle mixing to form larger flocs
• Aeration of wastewater
• Chlorination process

Rationale: Flocculation gently mixes to allow destabilized particles to form

larger settleable flocs.

• / 4

5. The main objective of sedimentation is to:

• Remove dissolved salts
• Adjust pH
• Separate suspended solids by gravity
• Add nutrients

Rationale: Sedimentation relies on gravity to remove dense suspended

solids.

• Which type of sedimentation occurs in secondary clarifiers?
• Discrete
• Flocculent
• Zone settling
• Compression

Rationale: Zone settling dominates in biological clarifiers where solids

move as a mass.

7. Sludge thickening reduces:

• Soluble BOD
• Volume of sludge
• Odor generation
• Pathogen load

Rationale: Thickening concentrates solids, minimizing volume for further

treatment. 3 / 4

8. The main function of pH adjustment in chemical treatment is to:

• Optimize chemical reactions
• Remove solids
• Disinfect effluent
• Increase oxygen transfer

Rationale: Many treatment processes depend on maintaining correct pH

for reaction efficiency.

9. Lime is used in wastewater treatment primarily for:

• Disinfection
• Dechlorination
• pH control and precipitation
• Odor removal

Rationale: Lime increases alkalinity and helps precipitate metals and

phosphates.

10. The main reason for using polymers in coagulation-flocculation is:

• To raise alkalinity
• To bridge particles and improve settling
• To disinfect water
• To remove hardness
• / 4