Colorado WW Operator D Exam Actual
Exam QUESTIONS AND ANSWERS 2026 |
Complete Solution Guide A+ Graded | Pass
Guaranteed - A+ Graded
Section 1: Basic Mathematics and Calculations
Questions 1-15
Question 1 Convert 150 gallons to cubic feet. (1 cubic foot = 7.48 gallons)
A. 15.0 ft³
B. 20.1 ft³ [CORRECT]
C. 1122 ft³
D. 1500 ft³
Correct Answer: B
Rationale: 150 gallons ÷ 7.48 gallons/ft³ = 20.05 ft³ ≈ 20.1 ft³.
• Option A (15.0) might come from incorrectly dividing by 10.
• Option C (1122) incorrectly multiplies 150 × 7.48 instead of dividing.
• Option D (1500) incorrectly multiplies by 10.
Question 2 A rectangular tank is 20 feet long, 10 feet wide, and has a water depth of 8 feet. What
is the volume of water in gallons? (1 ft³ = 7.48 gallons)
A. 1,600 gallons
B. 11,968 gallons [CORRECT]
C. 14,960 gallons
D. 20,000 gallons
Correct Answer: B
Rationale: Volume in cubic feet = length × width × depth = 20 ft × 10 ft × 8 ft = 1,600 ft³.
Convert to gallons: 1,600 ft³ × 7.48 gal/ft³ = 11,968 gallons.
• Option A (1,600) is the volume in cubic feet, not gallons.
, • Option C (14,960) might use incorrect dimensions (20×10×10).
• Option D (20,000) is a rounded incorrect estimate.
Question 3 A pump delivers 500 gallons per minute (gpm). How many million gallons per day
(MGD) does this represent?
A. 0.5 MGD
B. 0.72 MGD [CORRECT]
C. 1.2 MGD
D. 12 MGD
Correct Answer: B
Rationale: 500 gpm × 60 minutes/hour × 24 hours/day = 720,000 gallons/day = 0.72 MGD.
• Option A (0.5) incorrectly uses 500/1000.
• Option C (1.2) might use 500 × 2.4 (incorrect conversion).
• Option D (12) incorrectly calculates 500 × 24/1000.
Question 4 A treatment plant treats 2.5 MGD. The chlorine dosage is 2.5 mg/L. How many
pounds of chlorine are used per day? (Use formula: lbs/day = mg/L × MGD × 8.34)
A. 5.2 lbs
B. 20.9 lbs
C. 52.1 lbs [CORRECT]
D. 208.5 lbs
Correct Answer: C
Rationale: lbs/day = 2.5 mg/L × 2.5 MGD × 8.34 = 6.25 × 8.34 = 52.125 lbs ≈ 52.1 lbs.
• Option A (5.2) incorrectly calculates mg/L × MGD only (omits 8.34).
• Option B (20.9) incorrectly calculates 2.5 × 8.34 (omits MGD).
• Option D (208.5) incorrectly multiplies by 4.
Question 5 The detention time in a clarifier is 4 hours. If the flow rate is 1.5 MGD, what is the
volume of the clarifier in gallons?
A. 250,000 gallons [CORRECT]
B. 500,000 gallons
,C. 750,000 gallons
D. 1,000,000 gallons
Correct Answer: A
Rationale: Detention time = Volume / Flow rate. Rearranged: Volume = Flow rate × Detention
time. Convert 4 hours to days: 4/24 = 0.1667 days. Volume = 1.5 MGD × 0.1667 days = 0.25
million gallons = 250,000 gallons.
• Option B (500,000) would require 8 hours detention.
• Option C (750,000) would require 12 hours detention.
• Option D (1,000,000) would require 16 hours detention.
Question 6 A circular tank has a diameter of 40 feet and a depth of 12 feet. What is the volume
in cubic feet? (Use π = 3.14, Volume = π × r² × depth)
A. 7,536 ft³
B. 15,072 ft³ [CORRECT]
C. 30,144 ft³
D. 60,288 ft³
Correct Answer: B
Rationale: Radius = 40/2 = 20 feet. Volume = 3.14 × (20)² × 12 = 3.14 × 400 × 12 = 15,072 ft³.
• Option A (7,536) might use diameter instead of radius (3.14 × 40² × 12 ÷ 4 = 15,072, but
error in calculation).
• Option C (30,144) might use diameter squared without dividing by 4.
• Option D (60,288) might double the correct answer.
Question 7 What is the flow velocity in a 12-inch pipe carrying 2.0 cfs (cubic feet per second)?
(Velocity = Flow / Area, Area = π × r², 12 inches = 1 foot diameter)
A. 1.5 fps
B. 2.0 fps
C. 2.55 fps [CORRECT]
D. 4.0 fps
Correct Answer: C
Rationale: Diameter = 1 foot, radius = 0.5 feet. Area = 3.14 × (0.5)² = 0.785 ft². Velocity = 2.0
cfs / 0.785 ft² = 2.55 fps.
, • Option A (1.5) might use incorrect area calculation.
• Option B (2.0) assumes 1 ft² area.
• Option D (4.0) might use radius as 0.25 ft.
Question 8 A treatment plant has a surface loading rate of 0.5 gpm/ft² on a clarifier with surface
area of 2,000 ft². What is the flow rate in gpm?
A. 500 gpm
B. 1,000 gpm [CORRECT]
C. 2,000 gpm
D. 4,000 gpm
Correct Answer: B
Rationale: Surface loading rate = Flow / Area. Rearranged: Flow = Loading rate × Area = 0.5
gpm/ft² × 2,000 ft² = 1,000 gpm.
• Option A (500) might divide instead of multiply.
• Option C (2,000) might use 1.0 gpm/ft².
• Option D (4,000) might double the correct answer.
Question 9 How many pounds of alum are needed to treat 5 MGD at a dosage of 8 mg/L? (lbs =
mg/L × MGD × 8.34)
A. 167 lbs
B. 334 lbs [CORRECT]
C. 667 lbs
D. 1,334 lbs
Correct Answer: B
Rationale: lbs = 8 mg/L × 5 MGD × 8.34 = 40 × 8.34 = 333.6 ≈ 334 lbs.
• Option A (167) might use 4 MGD or incorrect formula.
• Option C (667) might use 10 mg/L or double the MGD.
• Option D (1,334) might use 16 mg/L.
Question 10 A pump must lift water 50 feet vertically. What is the pressure in psi required? (1
psi = 2.31 feet of head)
Exam QUESTIONS AND ANSWERS 2026 |
Complete Solution Guide A+ Graded | Pass
Guaranteed - A+ Graded
Section 1: Basic Mathematics and Calculations
Questions 1-15
Question 1 Convert 150 gallons to cubic feet. (1 cubic foot = 7.48 gallons)
A. 15.0 ft³
B. 20.1 ft³ [CORRECT]
C. 1122 ft³
D. 1500 ft³
Correct Answer: B
Rationale: 150 gallons ÷ 7.48 gallons/ft³ = 20.05 ft³ ≈ 20.1 ft³.
• Option A (15.0) might come from incorrectly dividing by 10.
• Option C (1122) incorrectly multiplies 150 × 7.48 instead of dividing.
• Option D (1500) incorrectly multiplies by 10.
Question 2 A rectangular tank is 20 feet long, 10 feet wide, and has a water depth of 8 feet. What
is the volume of water in gallons? (1 ft³ = 7.48 gallons)
A. 1,600 gallons
B. 11,968 gallons [CORRECT]
C. 14,960 gallons
D. 20,000 gallons
Correct Answer: B
Rationale: Volume in cubic feet = length × width × depth = 20 ft × 10 ft × 8 ft = 1,600 ft³.
Convert to gallons: 1,600 ft³ × 7.48 gal/ft³ = 11,968 gallons.
• Option A (1,600) is the volume in cubic feet, not gallons.
, • Option C (14,960) might use incorrect dimensions (20×10×10).
• Option D (20,000) is a rounded incorrect estimate.
Question 3 A pump delivers 500 gallons per minute (gpm). How many million gallons per day
(MGD) does this represent?
A. 0.5 MGD
B. 0.72 MGD [CORRECT]
C. 1.2 MGD
D. 12 MGD
Correct Answer: B
Rationale: 500 gpm × 60 minutes/hour × 24 hours/day = 720,000 gallons/day = 0.72 MGD.
• Option A (0.5) incorrectly uses 500/1000.
• Option C (1.2) might use 500 × 2.4 (incorrect conversion).
• Option D (12) incorrectly calculates 500 × 24/1000.
Question 4 A treatment plant treats 2.5 MGD. The chlorine dosage is 2.5 mg/L. How many
pounds of chlorine are used per day? (Use formula: lbs/day = mg/L × MGD × 8.34)
A. 5.2 lbs
B. 20.9 lbs
C. 52.1 lbs [CORRECT]
D. 208.5 lbs
Correct Answer: C
Rationale: lbs/day = 2.5 mg/L × 2.5 MGD × 8.34 = 6.25 × 8.34 = 52.125 lbs ≈ 52.1 lbs.
• Option A (5.2) incorrectly calculates mg/L × MGD only (omits 8.34).
• Option B (20.9) incorrectly calculates 2.5 × 8.34 (omits MGD).
• Option D (208.5) incorrectly multiplies by 4.
Question 5 The detention time in a clarifier is 4 hours. If the flow rate is 1.5 MGD, what is the
volume of the clarifier in gallons?
A. 250,000 gallons [CORRECT]
B. 500,000 gallons
,C. 750,000 gallons
D. 1,000,000 gallons
Correct Answer: A
Rationale: Detention time = Volume / Flow rate. Rearranged: Volume = Flow rate × Detention
time. Convert 4 hours to days: 4/24 = 0.1667 days. Volume = 1.5 MGD × 0.1667 days = 0.25
million gallons = 250,000 gallons.
• Option B (500,000) would require 8 hours detention.
• Option C (750,000) would require 12 hours detention.
• Option D (1,000,000) would require 16 hours detention.
Question 6 A circular tank has a diameter of 40 feet and a depth of 12 feet. What is the volume
in cubic feet? (Use π = 3.14, Volume = π × r² × depth)
A. 7,536 ft³
B. 15,072 ft³ [CORRECT]
C. 30,144 ft³
D. 60,288 ft³
Correct Answer: B
Rationale: Radius = 40/2 = 20 feet. Volume = 3.14 × (20)² × 12 = 3.14 × 400 × 12 = 15,072 ft³.
• Option A (7,536) might use diameter instead of radius (3.14 × 40² × 12 ÷ 4 = 15,072, but
error in calculation).
• Option C (30,144) might use diameter squared without dividing by 4.
• Option D (60,288) might double the correct answer.
Question 7 What is the flow velocity in a 12-inch pipe carrying 2.0 cfs (cubic feet per second)?
(Velocity = Flow / Area, Area = π × r², 12 inches = 1 foot diameter)
A. 1.5 fps
B. 2.0 fps
C. 2.55 fps [CORRECT]
D. 4.0 fps
Correct Answer: C
Rationale: Diameter = 1 foot, radius = 0.5 feet. Area = 3.14 × (0.5)² = 0.785 ft². Velocity = 2.0
cfs / 0.785 ft² = 2.55 fps.
, • Option A (1.5) might use incorrect area calculation.
• Option B (2.0) assumes 1 ft² area.
• Option D (4.0) might use radius as 0.25 ft.
Question 8 A treatment plant has a surface loading rate of 0.5 gpm/ft² on a clarifier with surface
area of 2,000 ft². What is the flow rate in gpm?
A. 500 gpm
B. 1,000 gpm [CORRECT]
C. 2,000 gpm
D. 4,000 gpm
Correct Answer: B
Rationale: Surface loading rate = Flow / Area. Rearranged: Flow = Loading rate × Area = 0.5
gpm/ft² × 2,000 ft² = 1,000 gpm.
• Option A (500) might divide instead of multiply.
• Option C (2,000) might use 1.0 gpm/ft².
• Option D (4,000) might double the correct answer.
Question 9 How many pounds of alum are needed to treat 5 MGD at a dosage of 8 mg/L? (lbs =
mg/L × MGD × 8.34)
A. 167 lbs
B. 334 lbs [CORRECT]
C. 667 lbs
D. 1,334 lbs
Correct Answer: B
Rationale: lbs = 8 mg/L × 5 MGD × 8.34 = 40 × 8.34 = 333.6 ≈ 334 lbs.
• Option A (167) might use 4 MGD or incorrect formula.
• Option C (667) might use 10 mg/L or double the MGD.
• Option D (1,334) might use 16 mg/L.
Question 10 A pump must lift water 50 feet vertically. What is the pressure in psi required? (1
psi = 2.31 feet of head)
