Louisiana Water Treatment Operator Level II
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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Multiple-Choice Questions (1–50)
1. What is the primary purpose of coagulation in water treatment?
A. Remove dissolved minerals
B. Destabilize suspended particles
C. Adjust pH
D. Add chlorine
Coagulation neutralizes particle charges so they can clump
together.
2. Which chemical is most commonly used as a coagulant?
A. Sodium hypochlorite
B. Lime
C. Aluminum sulfate (alum)
D. Carbon dioxide
Alum is the most widely used coagulant in U.S. water treatment
plants.
3. Flocculation is best described as:
A. Mixing chemicals at high speed
B. Gentle mixing to form larger floc particles
C. Settling of solids
, D. Rapid mixing of coagulants
Flocculation gently grows floc so it can settle effectively.
4. The ideal turbidity after filtration should be:
A. 5 NTU
B. Less than 0.3 NTU
C. Less than 2 NTU
D. 1 NTU exactly
Most regulations require <0.3 NTU for effective pathogen removal.
5. Breakpoint chlorination occurs when:
A. Chlorine first enters the system
B. Demand is fully satisfied and free chlorine residual begins to
rise
C. Free chlorine is zero
D. Combined chlorine peaks
At breakpoint, chlorine starts forming free residual.
6. Which gas is dangerous because it is heavier than air and collects
in low areas?
A. Oxygen
B. Chlorine gas
C. Nitrogen
D. Methane
Chlorine gas sinks and can accumulate in pits or basements.
7. The minimum free chlorine residual required in a distribution
system is:
A. 0.1 mg/L
B. 0.2 mg/L
C. 0.2 mg/L
, D. 0.5 mg/L
Regulations require at least 0.2 mg/L free chlorine.
8. Hardness in water is mainly caused by:
A. Sodium and potassium
B. Iron and manganese
C. Chlorides
D. Calcium and magnesium
These two ions are responsible for most hardness.
9. What is the typical pH range for effective coagulation with alum?
A. 3–4
B. 5–6
C. 5.5–7.5
D. 8–9
Alum works best in slightly acidic to neutral pH.
10. Which valve type provides the best throttling control?
A. Gate valve
B. Plug valve
C. Ball valve
D. Globe valve
Globe valves offer precise flow control.
11. Chlorine gas reacts with water to form:
A. Sodium chloride
B. Hypochlorous and hydrochloric acids
C. Calcium carbonate
D. Sulfur dioxide
These acids create disinfecting chlorine species.
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
Multiple-Choice Questions (1–50)
1. What is the primary purpose of coagulation in water treatment?
A. Remove dissolved minerals
B. Destabilize suspended particles
C. Adjust pH
D. Add chlorine
Coagulation neutralizes particle charges so they can clump
together.
2. Which chemical is most commonly used as a coagulant?
A. Sodium hypochlorite
B. Lime
C. Aluminum sulfate (alum)
D. Carbon dioxide
Alum is the most widely used coagulant in U.S. water treatment
plants.
3. Flocculation is best described as:
A. Mixing chemicals at high speed
B. Gentle mixing to form larger floc particles
C. Settling of solids
, D. Rapid mixing of coagulants
Flocculation gently grows floc so it can settle effectively.
4. The ideal turbidity after filtration should be:
A. 5 NTU
B. Less than 0.3 NTU
C. Less than 2 NTU
D. 1 NTU exactly
Most regulations require <0.3 NTU for effective pathogen removal.
5. Breakpoint chlorination occurs when:
A. Chlorine first enters the system
B. Demand is fully satisfied and free chlorine residual begins to
rise
C. Free chlorine is zero
D. Combined chlorine peaks
At breakpoint, chlorine starts forming free residual.
6. Which gas is dangerous because it is heavier than air and collects
in low areas?
A. Oxygen
B. Chlorine gas
C. Nitrogen
D. Methane
Chlorine gas sinks and can accumulate in pits or basements.
7. The minimum free chlorine residual required in a distribution
system is:
A. 0.1 mg/L
B. 0.2 mg/L
C. 0.2 mg/L
, D. 0.5 mg/L
Regulations require at least 0.2 mg/L free chlorine.
8. Hardness in water is mainly caused by:
A. Sodium and potassium
B. Iron and manganese
C. Chlorides
D. Calcium and magnesium
These two ions are responsible for most hardness.
9. What is the typical pH range for effective coagulation with alum?
A. 3–4
B. 5–6
C. 5.5–7.5
D. 8–9
Alum works best in slightly acidic to neutral pH.
10. Which valve type provides the best throttling control?
A. Gate valve
B. Plug valve
C. Ball valve
D. Globe valve
Globe valves offer precise flow control.
11. Chlorine gas reacts with water to form:
A. Sodium chloride
B. Hypochlorous and hydrochloric acids
C. Calcium carbonate
D. Sulfur dioxide
These acids create disinfecting chlorine species.
