Texas Water Treatment Operator – TCEQ Class A Exam Prep |
questions & answers & rationale | 2025/2026 | Latest Update|
Instant download!!
1. A water treatment plant receives 5 MGD of raw water. The plant uses 3 mg/L of chlorine for
disinfection. How many pounds of chlorine are required per day? (1 mg/L = 8.34 pounds per million
gallons)
A. 125 pounds
B. 100 pounds
C. 125.1 pounds (correct answer)
D. 150 pounds
Rationale: Chlorine required (lbs/day) = Flow (MGD) × Dose (mg/L) × 8.34 = 5 × 3 × 8.34 = 125.1
lbs/day.
2. Which of the following is the primary purpose of coagulation in water treatment?
A. Remove dissolved salts
B. Aggregate fine particles into flocs for sedimentation (correct answer)
C. Increase pH only
D. Filter water
Rationale: Coagulation uses chemicals like alum to form flocs, making suspended solids easier to remove.
3. A clarifier has a surface area of 4,000 sq ft and flow of 4 MGD. What is the surface loading rate in
gpd/sq ft?
A. 500 gpd/sq ft
B. 1,000 gpd/sq ft (correct answer)
C. 1,500 gpd/sq ft
D. 2,000 gpd/sq ft
,Rationale: Surface loading = Flow ÷ Area = (4,000,000 gpd ÷ 4,000 sq ft) = 1,000 gpd/sq ft.
4. Which of the following is the primary purpose of pH adjustment in water treatment?
A. Disinfect water
B. Optimize coagulation and corrosion control (correct answer)
C. Increase TDS
D. Reduce turbidity
Rationale: Proper pH ensures coagulants work effectively and prevents corrosion in distribution systems.
5. A water sample has a turbidity of 8 NTU. After treatment, it measures 0.3 NTU. Which is true?
A. Treatment is ineffective
B. Treatment meets regulatory standards (correct answer)
C. Water is unsafe for chlorine residual
D. TDS is too high
Rationale: TCEQ requires treated water turbidity <1 NTU; 0.3 NTU meets standards.
6. Which of the following is true about activated carbon in water treatment?
A. Removes suspended solids only
B. Removes organic contaminants and taste/odor compounds (correct answer)
C. Adds chlorine
D. Increases turbidity
Rationale: Activated carbon adsorbs dissolved organics, improving taste and odor.
7. A reservoir has a volume of 100 MG and an inflow of 5 MGD. What is the hydraulic retention time
(HRT)?
A. 10 days
B. 20 days (correct answer)
, C. 15 days
D. 25 days
Rationale: HRT = Volume ÷ Flow = 100 ÷ 5 = 20 days.
8. Which of the following is true regarding flocculation in water treatment?
A. Randomly mix water
B. Gently mix water to grow flocs formed during coagulation (correct answer)
C. Only add chlorine
D. Increase TDS
Rationale: Flocculation gently mixes water to allow small flocs to combine into larger, settleable flocs.
9. A water sample has 120 mg/L hardness. What is the equivalent in grains per gallon (gpg)? (1 gpg =
17.1 mg/L)
A. 7 gpg
B. 5 gpg
C. 7.02 gpg (correct answer)
D. 8 gpg
Rationale: gpg = mg/L ÷ 17.1 = 120 ÷ 17.1 ≈ 7.02 gpg.
10. Which of the following is a primary purpose of sedimentation in water treatment?
A. Chlorinate water
B. Remove settleable solids (correct answer)
C. Adjust pH
D. Remove dissolved salts
Rationale: Sedimentation allows heavier particles to settle before filtration.
11. A plant uses 150 lbs of alum daily to treat 3 MGD of water. What is the dose in mg/L?
questions & answers & rationale | 2025/2026 | Latest Update|
Instant download!!
1. A water treatment plant receives 5 MGD of raw water. The plant uses 3 mg/L of chlorine for
disinfection. How many pounds of chlorine are required per day? (1 mg/L = 8.34 pounds per million
gallons)
A. 125 pounds
B. 100 pounds
C. 125.1 pounds (correct answer)
D. 150 pounds
Rationale: Chlorine required (lbs/day) = Flow (MGD) × Dose (mg/L) × 8.34 = 5 × 3 × 8.34 = 125.1
lbs/day.
2. Which of the following is the primary purpose of coagulation in water treatment?
A. Remove dissolved salts
B. Aggregate fine particles into flocs for sedimentation (correct answer)
C. Increase pH only
D. Filter water
Rationale: Coagulation uses chemicals like alum to form flocs, making suspended solids easier to remove.
3. A clarifier has a surface area of 4,000 sq ft and flow of 4 MGD. What is the surface loading rate in
gpd/sq ft?
A. 500 gpd/sq ft
B. 1,000 gpd/sq ft (correct answer)
C. 1,500 gpd/sq ft
D. 2,000 gpd/sq ft
,Rationale: Surface loading = Flow ÷ Area = (4,000,000 gpd ÷ 4,000 sq ft) = 1,000 gpd/sq ft.
4. Which of the following is the primary purpose of pH adjustment in water treatment?
A. Disinfect water
B. Optimize coagulation and corrosion control (correct answer)
C. Increase TDS
D. Reduce turbidity
Rationale: Proper pH ensures coagulants work effectively and prevents corrosion in distribution systems.
5. A water sample has a turbidity of 8 NTU. After treatment, it measures 0.3 NTU. Which is true?
A. Treatment is ineffective
B. Treatment meets regulatory standards (correct answer)
C. Water is unsafe for chlorine residual
D. TDS is too high
Rationale: TCEQ requires treated water turbidity <1 NTU; 0.3 NTU meets standards.
6. Which of the following is true about activated carbon in water treatment?
A. Removes suspended solids only
B. Removes organic contaminants and taste/odor compounds (correct answer)
C. Adds chlorine
D. Increases turbidity
Rationale: Activated carbon adsorbs dissolved organics, improving taste and odor.
7. A reservoir has a volume of 100 MG and an inflow of 5 MGD. What is the hydraulic retention time
(HRT)?
A. 10 days
B. 20 days (correct answer)
, C. 15 days
D. 25 days
Rationale: HRT = Volume ÷ Flow = 100 ÷ 5 = 20 days.
8. Which of the following is true regarding flocculation in water treatment?
A. Randomly mix water
B. Gently mix water to grow flocs formed during coagulation (correct answer)
C. Only add chlorine
D. Increase TDS
Rationale: Flocculation gently mixes water to allow small flocs to combine into larger, settleable flocs.
9. A water sample has 120 mg/L hardness. What is the equivalent in grains per gallon (gpg)? (1 gpg =
17.1 mg/L)
A. 7 gpg
B. 5 gpg
C. 7.02 gpg (correct answer)
D. 8 gpg
Rationale: gpg = mg/L ÷ 17.1 = 120 ÷ 17.1 ≈ 7.02 gpg.
10. Which of the following is a primary purpose of sedimentation in water treatment?
A. Chlorinate water
B. Remove settleable solids (correct answer)
C. Adjust pH
D. Remove dissolved salts
Rationale: Sedimentation allows heavier particles to settle before filtration.
11. A plant uses 150 lbs of alum daily to treat 3 MGD of water. What is the dose in mg/L?
