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1. What is the primary purpose of coagulation in water treatment?
A. Filtration
B. Chemical destabilization of particles
C. Disinfection
D. Aeration
Coagulation involves adding chemicals to destabilize suspended particles, making
them easier to remove in sedimentation and filtration.
2. Which chemical is commonly used as a coagulant in water treatment?
A. Chlorine
B. Alum (Aluminum sulfate)
C. Sodium hydroxide
D. Ozone
Alum is widely used to promote floc formation by destabilizing particles.
3. What is the primary function of a rapid mix basin?
A. Sedimentation
B. Filtration
C. Even distribution of coagulants
D. Disinfection
Rapid mix basins quickly disperse coagulants into water to ensure effective particle
destabilization.
4. Which process follows coagulation in conventional water treatment?
A. Disinfection
B. Flocculation
C. Aeration
, D. Fluoridation
Flocculation allows small destabilized particles to aggregate into larger flocs that
can settle out.
5. The removal of dissolved gases and volatile substances is primarily achieved by:
A. Filtration
B. Coagulation
C. Aeration
D. Sedimentation
Aeration exposes water to air, helping remove gases like carbon dioxide and
volatile compounds.
6. What is the main purpose of sedimentation in water treatment?
A. Disinfection
B. Coagulation
C. Removal of suspended solids
D. Fluoridation
Sedimentation allows flocs and other suspended particles to settle by gravity.
7. Which type of filter media is most commonly used in conventional water treatment?
A. Sand
B. Activated carbon
C. Anthracite over sand
D. Gravel
Dual-media filters (anthracite over sand) provide effective filtration by capturing
particles at different depths.
8. What is the primary purpose of disinfection in water treatment?
A. Remove color
B. Coagulate particles
C. Kill or inactivate pathogens
D. Aerate water
Disinfection prevents waterborne diseases by targeting bacteria, viruses, and
protozoa.
9. Which disinfectant provides a residual in the distribution system?
A. Ozone
B. UV light
C. Chlorine
D. Hydrogen peroxide
Chlorine maintains residual disinfectant levels in pipes to prevent microbial growth.
10. Free chlorine is measured as:
A. Total chlorine minus combined chlorine
, B. The amount of chlorine available for disinfection
C. Chloramine concentration
D. Chlorine dioxide
Free chlorine refers to chlorine available for microbial inactivation, not bound in
compounds.
11. What is the ideal pH range for coagulation using alum?
A. 2.0–3.0
B. 4.0–5.0
C. 6.0–7.5
D. 8.0–9.0
Alum is most effective within a slightly acidic to neutral pH range.
12. What is a typical detention time in a sedimentation basin?
A. 5–10 minutes
B. 2–4 hours
C. 24 hours
D. 30 minutes
Sedimentation basins are designed to allow sufficient time for flocs to settle.
13. Which process is most effective at removing iron and manganese?
A. Filtration
B. Coagulation
C. Oxidation followed by filtration
D. Aeration
Oxidation converts dissolved iron and manganese into solid forms that can be
filtered out.
14. Water turbidity is primarily caused by:
A. Dissolved salts
B. Suspended particles
C. Microorganisms only
D. Chlorine
Turbidity measures water cloudiness due to suspended solids.
15. A water operator should maintain chlorine residual of at least:
A. 0.1 mg/L
B. 0.2 mg/L
C. 1.0 mg/L
D. 2.0 mg/L
Florida requires a minimum free chlorine residual of 0.2 mg/L in distribution
systems.