ARIZONA WATER TREATMENT OPERATOR CERTIFICATION EXAM
GRADE 2 ACTUAL EXAM 2026/2027 ACCURATE TEST COMPLETE
APPROVED QUESTIONS AND CORRECT DETAILED ANSWERS WITH
RATIONALES (VERIFIED SOLUTIONS) LATEST UPDATED VERSION
2026 EDITION |GUARANTEED SUCCESS A+
1. A water treatment plant operates at a flow rate of 2.5 MGD. The
operator adds chlorine at a dose of 2.0 mg/L. How many pounds of
chlorine are required per day?
A) 41.7 lbs./day
B) 41.7 lbs./day CORRECT ANSWER – *Rationale: Use the pounds
formula: Flow (MGD) × Dose (mg/L) × 8.34. 2.5 × 2.0 × 8.34 = 41.7
lbs./day.*
C) 20.8 lbs./day
D) 83.4 lbs./day
2. What is the primary purpose of coagulation in water treatment?
A) Disinfection of pathogens
B) Neutralizing electrical charges to allow particles to clump
together CORRECT ANSWER – Rationale: Coagulation uses
chemicals like alum to destabilize colloidal particles by neutralizing
their negative charges, forming micro-flocs.
C) Removing dissolved gases
D) Adjusting pH to neutral
3. A sedimentation basin is 80 ft. long, 25 ft. wide, and has an average
water depth of 12 ft. What is the detention time at a flow of 2.5 MGD?
A) 2.1 hours
B) 4.3 hours CORRECT ANSWER – *Rationale: Volume =
80×25×12 = 24,000 ft³. Convert to gallons ×7.48 = 179,520 gal. Flow =
2.5 MGD = 2,500,000 gal/day. Detention time (hrs.) = (Vol gal / Flow
god) × 24 = (179,520/2,500,000)×24 = 4.3 hrs.*
,C) 6.5 hours
D) 1.8 hours
4. Which of the following is the most common chemical used for pH
adjustment in Arizona water treatment?
A) Sodium hypochlorite
B) Lime (calcium hydroxide) CORRECT ANSWER – Rationale:
Lime is frequently used to raise pH and alkalinity, especially in surface
water treatment and for corrosion control.
C) Aluminum sulfate
D) Potassium permanganate
5. If the chlorine residual in a clear well is 1.5 mg/L and the chlorine
demand is 0.6 mg/L, what is the chlorine dose?
A) 0.9 mg/L
B) 2.1 mg/L CORRECT ANSWER – *Rationale: Dose = Demand +
Residual = 0.6 + 1.5 = 2.1 mg/L.*
C) 2.5 mg/L
D) 1.2 mg/L
6. The maximum contaminant level (MCL) for arsenic in drinking water
is:
A) 0.010 mg/L
B) 0.010 mg/L CORRECT ANSWER – *Rationale: EPA MCL for
arsenic is 0.010 mg/L (10 µg/L). Arizona primacy enforces this
standard.*
C) 0.005 mg/L
D) 0.050 mg/L
7. A filter has a surface area of 200 sq. ft. and operates at a filtration rate
of 4 gym/sq. ft. What is the flow rate through the filter in MGD?
A) 0.58 MGD
B) 1.15 MGD CORRECT ANSWER – *Rationale: Flow (gym) = Rate
× Area = 4 × 200 = 800 gym. Convert to MGD: 800 gym × 1440
min/day = 1,152,000 gal/day = 1.15 MGD.*
, C) 2.30 MGD
D) 0.29 MGD
8. What is the acceptable turbidity level for filtered water leaving a
conventional treatment plant under the Surface Water Treatment Rule?
A) Always < 0.3 NTU in 95% of samples
B) ≤0.3 NTU in 95% of samples and never exceed 1.0
NTU CORRECT ANSWER – Rationale: SWTR requires combined
filter effluent turbidity ≤0.3 NTU in 95% of measurements, not to exceed
1.0 NTU.
C) < 5.0 NTU at all times
D) < 1.0 NTU for all samples
9. Which type of backwash is most effective for anthracite/sand dual
media filters?
A) Air scour alone
B) Air scour followed by low- and high-rate water
backwash CORRECT ANSWER – Rationale: Air scour loosens
media, then low-rate rinse, then high-rate backwash removes solids
efficiently without media loss.
C) Continuous surface wash only
D) High-rate water backwash without air
10. The operator notices a drop in filter run length. The most likely
cause is:
A) Decreased coagulant dose
B) Increased turbidity or coagulant overfeed causing floc
carryover CORRECT ANSWER – Rationale: Higher solids loading
or poor floc formation clogs filters faster, reducing run time.
C) Lower flow rate
D) Cleaner influent water
11. What chemical is commonly used as a sequestrate for controlling
iron and manganese?
A) Sodium hex metaphosphate
B) Sodium hex metaphosphate CORRECT ANSWER – Rationale:
GRADE 2 ACTUAL EXAM 2026/2027 ACCURATE TEST COMPLETE
APPROVED QUESTIONS AND CORRECT DETAILED ANSWERS WITH
RATIONALES (VERIFIED SOLUTIONS) LATEST UPDATED VERSION
2026 EDITION |GUARANTEED SUCCESS A+
1. A water treatment plant operates at a flow rate of 2.5 MGD. The
operator adds chlorine at a dose of 2.0 mg/L. How many pounds of
chlorine are required per day?
A) 41.7 lbs./day
B) 41.7 lbs./day CORRECT ANSWER – *Rationale: Use the pounds
formula: Flow (MGD) × Dose (mg/L) × 8.34. 2.5 × 2.0 × 8.34 = 41.7
lbs./day.*
C) 20.8 lbs./day
D) 83.4 lbs./day
2. What is the primary purpose of coagulation in water treatment?
A) Disinfection of pathogens
B) Neutralizing electrical charges to allow particles to clump
together CORRECT ANSWER – Rationale: Coagulation uses
chemicals like alum to destabilize colloidal particles by neutralizing
their negative charges, forming micro-flocs.
C) Removing dissolved gases
D) Adjusting pH to neutral
3. A sedimentation basin is 80 ft. long, 25 ft. wide, and has an average
water depth of 12 ft. What is the detention time at a flow of 2.5 MGD?
A) 2.1 hours
B) 4.3 hours CORRECT ANSWER – *Rationale: Volume =
80×25×12 = 24,000 ft³. Convert to gallons ×7.48 = 179,520 gal. Flow =
2.5 MGD = 2,500,000 gal/day. Detention time (hrs.) = (Vol gal / Flow
god) × 24 = (179,520/2,500,000)×24 = 4.3 hrs.*
,C) 6.5 hours
D) 1.8 hours
4. Which of the following is the most common chemical used for pH
adjustment in Arizona water treatment?
A) Sodium hypochlorite
B) Lime (calcium hydroxide) CORRECT ANSWER – Rationale:
Lime is frequently used to raise pH and alkalinity, especially in surface
water treatment and for corrosion control.
C) Aluminum sulfate
D) Potassium permanganate
5. If the chlorine residual in a clear well is 1.5 mg/L and the chlorine
demand is 0.6 mg/L, what is the chlorine dose?
A) 0.9 mg/L
B) 2.1 mg/L CORRECT ANSWER – *Rationale: Dose = Demand +
Residual = 0.6 + 1.5 = 2.1 mg/L.*
C) 2.5 mg/L
D) 1.2 mg/L
6. The maximum contaminant level (MCL) for arsenic in drinking water
is:
A) 0.010 mg/L
B) 0.010 mg/L CORRECT ANSWER – *Rationale: EPA MCL for
arsenic is 0.010 mg/L (10 µg/L). Arizona primacy enforces this
standard.*
C) 0.005 mg/L
D) 0.050 mg/L
7. A filter has a surface area of 200 sq. ft. and operates at a filtration rate
of 4 gym/sq. ft. What is the flow rate through the filter in MGD?
A) 0.58 MGD
B) 1.15 MGD CORRECT ANSWER – *Rationale: Flow (gym) = Rate
× Area = 4 × 200 = 800 gym. Convert to MGD: 800 gym × 1440
min/day = 1,152,000 gal/day = 1.15 MGD.*
, C) 2.30 MGD
D) 0.29 MGD
8. What is the acceptable turbidity level for filtered water leaving a
conventional treatment plant under the Surface Water Treatment Rule?
A) Always < 0.3 NTU in 95% of samples
B) ≤0.3 NTU in 95% of samples and never exceed 1.0
NTU CORRECT ANSWER – Rationale: SWTR requires combined
filter effluent turbidity ≤0.3 NTU in 95% of measurements, not to exceed
1.0 NTU.
C) < 5.0 NTU at all times
D) < 1.0 NTU for all samples
9. Which type of backwash is most effective for anthracite/sand dual
media filters?
A) Air scour alone
B) Air scour followed by low- and high-rate water
backwash CORRECT ANSWER – Rationale: Air scour loosens
media, then low-rate rinse, then high-rate backwash removes solids
efficiently without media loss.
C) Continuous surface wash only
D) High-rate water backwash without air
10. The operator notices a drop in filter run length. The most likely
cause is:
A) Decreased coagulant dose
B) Increased turbidity or coagulant overfeed causing floc
carryover CORRECT ANSWER – Rationale: Higher solids loading
or poor floc formation clogs filters faster, reducing run time.
C) Lower flow rate
D) Cleaner influent water
11. What chemical is commonly used as a sequestrate for controlling
iron and manganese?
A) Sodium hex metaphosphate
B) Sodium hex metaphosphate CORRECT ANSWER – Rationale:
