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Arizona Water Treatment Operator Certification Exam – Grade
2 ACTUAL EXAM COMPLETE QUESTIONS AND CORRECT
ANSWERS LATEST UPDATE THIS YEAR
Arizona Water Treatment Operator Certification Exam – Grade 2, each with an answer and a
summarized rationale based on ADEQ regulations, standard water treatment principles, and ABC-
accredited exam topics.
The questions begin after a point-form summary of actual exam coverage areas.
Summarized Exam Topics Covered (Point Form – Accurate for AZ Grade 2 Treatment Exam)
• Source Water & Characteristics: groundwater vs. surface water, raw water quality parameters,
seasonal variations
• Coagulation & Flocculation: chemical addition (alum, ferric chloride), mixing energy, jar testing,
pH optimization
• Sedimentation: basin types, detention time, weir loading, sludge removal, short-circuiting
prevention
• Filtration: filter media (sand, anthracite, GAC), backwashing cycles, filter ripening, turbidity
monitoring
• Disinfection: chlorine (gas, liquid, on-site generation), chloramines, CT calculations, breakpoint
chlorination
• Softening: lime-soda ash process, ion exchange, bypass blending, hardness testing
• Corrosion Control: pH adjustment, orthophosphate, Langelier Saturation Index (LSI),
lead/copper rule
• Fluoridation: fluoride chemicals, saturator systems, optimal levels (0.7 mg/L), daily testing
• Iron & Manganese Removal: oxidation, greensand filtration, sequestering agents
• Pumps & Motors: types (centrifugal, positive displacement), pump curves, cavitation, VFDs
• Hydraulics: head loss, pressure, flow measurement (Parshall flume, venturi), friction loss
calculations
• Laboratory: pH, turbidity (NTU), alkalinity, hardness, chlorine residual (DPD), coliform sampling
• Safety: confined space entry (OSHA), H2S, lockout/tagout, chlorine handling, PPE
• Regulations: SDWA, ADEQ reporting, MCLs (TTHM 0.080 mg/L, HAA5 0.060 mg/L), public
notification
• Math: detention time, loading rates (gpm/ft²), chemical dosage (mg/L → lbs/day), filter
backwash rate
• Administration: monthly operating reports, certification renewal (3 years), CEU requirements
1. A surface water treatment plant operates at 5 MGD. The raw water turbidity is 12 NTU, and the
settled water turbidity is 2.5 NTU. What is the percent turbidity removal after sedimentation?
A) 21%
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B) 46%
C) 79%
D) 95%
Answer: C
*Rationale: Percent removal = [(Raw - Treated) / Raw] × 100 = [(12 - 2.5) / 12] × 100 = 79.2%.
Sedimentation typically removes 70-85% of turbidity.*
2. A water treatment operator notices that the floc in the sedimentation basin is very small and not
settling properly. What is the most likely cause?
A) Excessive coagulant dose
B) Low coagulant dose or insufficient mixing
C) Filter backwash too frequent
D) Chlorine residual too high
Answer: B
Rationale: Under-dosing coagulant or poor flocculation mixing produces small, light floc that does not
settle. Jar testing should be conducted to optimize chemical dosage.
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3. What is the normal pH range for effective coagulation using alum (aluminum sulfate)?
A) 4.5 – 5.5
B) 5.5 – 7.5
C) 7.5 – 8.5
D) 8.5 – 9.5
Answer: B
Rationale: Alum works best in the pH range of 5.5 to 7.5. Outside this range, aluminum solubility
increases, and coagulation efficiency decreases .
4. A water system uses chloramination for disinfection. Which two chemicals are combined to form
monochloramine?
A) Chlorine and chlorine dioxide
B) Chlorine and ammonia
C) Chlorine and ozone
D) Ammonia and sodium hydroxide
Answer: B
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Rationale: Monochloramine is formed by combining chlorine with ammonia. This combined residual
provides longer-lasting disinfection in distribution systems .
5. During jar testing, the operator sees that floc is forming but is very light and does not settle within 30
minutes. What adjustment should be made?
A) Increase the mixing speed during flocculation
B) Add a coagulant aid (polymer)
C) Decrease the coagulant dose
D) Increase the pH to 9.0
Answer: B
Rationale: Adding a coagulant aid (polymer) helps bind floc particles together, increasing weight and
settling velocity. Excess coagulant may already be present .
6. A filter has a surface area of 200 ft² and produces 1,000 gpm. What is the filtration rate in gpm/ft²?
A) 2.5 gpm/ft²
B) 5.0 gpm/ft²
C) 7.5 gpm/ft²
D) 10.0 gpm/ft²
Arizona Water Treatment Operator Certification Exam – Grade
2 ACTUAL EXAM COMPLETE QUESTIONS AND CORRECT
ANSWERS LATEST UPDATE THIS YEAR
Arizona Water Treatment Operator Certification Exam – Grade 2, each with an answer and a
summarized rationale based on ADEQ regulations, standard water treatment principles, and ABC-
accredited exam topics.
The questions begin after a point-form summary of actual exam coverage areas.
Summarized Exam Topics Covered (Point Form – Accurate for AZ Grade 2 Treatment Exam)
• Source Water & Characteristics: groundwater vs. surface water, raw water quality parameters,
seasonal variations
• Coagulation & Flocculation: chemical addition (alum, ferric chloride), mixing energy, jar testing,
pH optimization
• Sedimentation: basin types, detention time, weir loading, sludge removal, short-circuiting
prevention
• Filtration: filter media (sand, anthracite, GAC), backwashing cycles, filter ripening, turbidity
monitoring
• Disinfection: chlorine (gas, liquid, on-site generation), chloramines, CT calculations, breakpoint
chlorination
• Softening: lime-soda ash process, ion exchange, bypass blending, hardness testing
• Corrosion Control: pH adjustment, orthophosphate, Langelier Saturation Index (LSI),
lead/copper rule
• Fluoridation: fluoride chemicals, saturator systems, optimal levels (0.7 mg/L), daily testing
• Iron & Manganese Removal: oxidation, greensand filtration, sequestering agents
• Pumps & Motors: types (centrifugal, positive displacement), pump curves, cavitation, VFDs
• Hydraulics: head loss, pressure, flow measurement (Parshall flume, venturi), friction loss
calculations
• Laboratory: pH, turbidity (NTU), alkalinity, hardness, chlorine residual (DPD), coliform sampling
• Safety: confined space entry (OSHA), H2S, lockout/tagout, chlorine handling, PPE
• Regulations: SDWA, ADEQ reporting, MCLs (TTHM 0.080 mg/L, HAA5 0.060 mg/L), public
notification
• Math: detention time, loading rates (gpm/ft²), chemical dosage (mg/L → lbs/day), filter
backwash rate
• Administration: monthly operating reports, certification renewal (3 years), CEU requirements
1. A surface water treatment plant operates at 5 MGD. The raw water turbidity is 12 NTU, and the
settled water turbidity is 2.5 NTU. What is the percent turbidity removal after sedimentation?
A) 21%
, Page 2 of 142
B) 46%
C) 79%
D) 95%
Answer: C
*Rationale: Percent removal = [(Raw - Treated) / Raw] × 100 = [(12 - 2.5) / 12] × 100 = 79.2%.
Sedimentation typically removes 70-85% of turbidity.*
2. A water treatment operator notices that the floc in the sedimentation basin is very small and not
settling properly. What is the most likely cause?
A) Excessive coagulant dose
B) Low coagulant dose or insufficient mixing
C) Filter backwash too frequent
D) Chlorine residual too high
Answer: B
Rationale: Under-dosing coagulant or poor flocculation mixing produces small, light floc that does not
settle. Jar testing should be conducted to optimize chemical dosage.
, Page 3 of 142
3. What is the normal pH range for effective coagulation using alum (aluminum sulfate)?
A) 4.5 – 5.5
B) 5.5 – 7.5
C) 7.5 – 8.5
D) 8.5 – 9.5
Answer: B
Rationale: Alum works best in the pH range of 5.5 to 7.5. Outside this range, aluminum solubility
increases, and coagulation efficiency decreases .
4. A water system uses chloramination for disinfection. Which two chemicals are combined to form
monochloramine?
A) Chlorine and chlorine dioxide
B) Chlorine and ammonia
C) Chlorine and ozone
D) Ammonia and sodium hydroxide
Answer: B
, Page 4 of 142
Rationale: Monochloramine is formed by combining chlorine with ammonia. This combined residual
provides longer-lasting disinfection in distribution systems .
5. During jar testing, the operator sees that floc is forming but is very light and does not settle within 30
minutes. What adjustment should be made?
A) Increase the mixing speed during flocculation
B) Add a coagulant aid (polymer)
C) Decrease the coagulant dose
D) Increase the pH to 9.0
Answer: B
Rationale: Adding a coagulant aid (polymer) helps bind floc particles together, increasing weight and
settling velocity. Excess coagulant may already be present .
6. A filter has a surface area of 200 ft² and produces 1,000 gpm. What is the filtration rate in gpm/ft²?
A) 2.5 gpm/ft²
B) 5.0 gpm/ft²
C) 7.5 gpm/ft²
D) 10.0 gpm/ft²
