Class A Exam Practice Questions And

Surface Water Treatment Operator Class A Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of coagulation in water treatment?
• To disinfect the water
• To remove dissolved salts
• To destabilize suspended particles
• To filter out microorganisms

Rationale: Coagulation is the process of adding chemicals, such as alum, to

destabilize colloidal and suspended particles so they can be removed more easily during sedimentation and filtration.

• Which of the following is the most commonly used coagulant in

surface water treatment? 1 / 4

• Sodium hypochlorite
• Aluminum sulfate (alum)
• Chloramine
• Ferric chloride

Rationale: Aluminum sulfate, commonly called alum, is widely used due to

its effectiveness, cost efficiency, and availability.

• What is the main function of flocculation in water treatment?
• To neutralize pH
• To disinfect water
• To aggregate destabilized particles into larger flocs
• To remove dissolved organic matter

Rationale: Flocculation gently mixes water to promote the collision and

aggregation of destabilized particles into larger flocs that can settle more easily in sedimentation basins.

• Which type of sedimentation basin is most commonly used in surface

water treatment plants?

• Radial-flow
• Rectangular
• Circular
• Inclined-plate 2 / 4

Rationale: Rectangular basins are widely used for their simplicity and ease

of maintenance; however, circular and inclined-plate designs are also used in specific cases.

5. The purpose of filtration in water treatment is to:

• Add disinfectant
• Remove dissolved chemicals
• Remove remaining suspended solids and turbidity
• Adjust water pH

Rationale: Filtration removes particles that were not removed during

sedimentation, improving water clarity and reducing turbidity.

• Which type of filter media is commonly used in conventional surface

water filtration?

• Activated carbon
• Sand
• Anthracite only
• Zeolite

Rationale: Sand is commonly used due to its effective particle removal and

cost efficiency; often combined with anthracite for dual-media filtration.

• Which parameter is commonly used to measure water turbidity?
• pH
• Nephelometric Turbidity Units (NTU) 3 / 4

• Total Dissolved Solids (TDS)
• Conductivity

Rationale: NTU measures the cloudiness or turbidity of water, which

indicates the presence of suspended solids.

• What is the main purpose of chlorination in water treatment?
• To disinfect water and inactivate pathogens
• To remove turbidity
• To coagulate particles
• To adjust alkalinity

Rationale: Chlorination is a chemical disinfection process that kills bacteria,

viruses, and other pathogens to make water safe for consumption.

• Which of the following is a by-product of chlorination?
• Ozone
• Trihalomethanes (THMs)
• Alum
• Hydrogen peroxide

Rationale: THMs are disinfection by-products formed when chlorine reacts

with natural organic matter in water.

• What is the ideal pH range for conventional coagulation using

alum?

A. 3.0–4.0

• 5.0–6.0
• / 4