Texas Class D Water License Exam 2026/2027 –
Complete Study Guide & Test Bank | 250+
Practice Questions with Verified Answers | TCEQ
Class D Water Operator Certification
1. Which of the following is a primary source of surface water?
A) Well
B) *River
C) Spring
D) Aquifer
Answer: B
Rationale: Rivers, lakes, and reservoirs are surface water sources.
2. Groundwater is typically found in:
A) Lakes
B) *Aquifers
C) Rivers
D) Oceans
Answer: B
Rationale: Aquifers are underground layers of water-bearing rock.
3. The Safe Drinking Water Act is enforced by:
,A) OSHA
B) *EPA
C) FDA
D) USDA
Answer: B
Rationale: EPA sets national drinking water standards under SDWA.
4. In Texas, the agency regulating public water systems is:
A) TCEQ
B) *TCEQ
C) TPWD
D) TxDOT
Answer: B
Rationale: Texas Commission on Environmental Quality (TCEQ) regulates water
systems.
5. The maximum contaminant level (MCL) for nitrate in drinking water is:
A) 5 mg/L
B) *10 mg/L
C) 15 mg/L
D) 20 mg/L
Answer: B
Rationale: EPA MCL for nitrate is 10 mg/L as nitrogen.
,6. Turbidity is a measure of:
A) Color
B) *Cloudiness
C) Taste
D) Odor
Answer: B
Rationale: Turbidity measures suspended particles causing cloudiness.
7. The primary disinfectant used in most Texas water systems is:
A) Ozone
B) *Chlorine
C) UV light
D) Chloramine
Answer: B
Rationale: Chlorine is the most common disinfectant for public water.
8. A minimum chlorine residual in the distribution system is typically:
A) 0.1 mg/L
B) *0.2 mg/L
C) 0.5 mg/L
D) 1.0 mg/L
, Answer: B
Rationale: TCEQ requires a minimum 0.2 mg/L free chlorine residual.
9. The process of adding chemicals to water to remove suspended particles is:
A) Filtration
B) *Coagulation
C) Disinfection
D) Sedimentation
Answer: B
Rationale: Coagulation neutralizes particle charges to form floc.
10. Flocculation is the process of:
A) Adding coagulants
B) *Gentle mixing to form larger floc
C) Settling floc
D) Filtering floc
Answer: B
Rationale: Flocculation encourages particles to clump together.
11. Sedimentation removes floc by:
A) *Gravity settling
B) Filtration
Complete Study Guide & Test Bank | 250+
Practice Questions with Verified Answers | TCEQ
Class D Water Operator Certification
1. Which of the following is a primary source of surface water?
A) Well
B) *River
C) Spring
D) Aquifer
Answer: B
Rationale: Rivers, lakes, and reservoirs are surface water sources.
2. Groundwater is typically found in:
A) Lakes
B) *Aquifers
C) Rivers
D) Oceans
Answer: B
Rationale: Aquifers are underground layers of water-bearing rock.
3. The Safe Drinking Water Act is enforced by:
,A) OSHA
B) *EPA
C) FDA
D) USDA
Answer: B
Rationale: EPA sets national drinking water standards under SDWA.
4. In Texas, the agency regulating public water systems is:
A) TCEQ
B) *TCEQ
C) TPWD
D) TxDOT
Answer: B
Rationale: Texas Commission on Environmental Quality (TCEQ) regulates water
systems.
5. The maximum contaminant level (MCL) for nitrate in drinking water is:
A) 5 mg/L
B) *10 mg/L
C) 15 mg/L
D) 20 mg/L
Answer: B
Rationale: EPA MCL for nitrate is 10 mg/L as nitrogen.
,6. Turbidity is a measure of:
A) Color
B) *Cloudiness
C) Taste
D) Odor
Answer: B
Rationale: Turbidity measures suspended particles causing cloudiness.
7. The primary disinfectant used in most Texas water systems is:
A) Ozone
B) *Chlorine
C) UV light
D) Chloramine
Answer: B
Rationale: Chlorine is the most common disinfectant for public water.
8. A minimum chlorine residual in the distribution system is typically:
A) 0.1 mg/L
B) *0.2 mg/L
C) 0.5 mg/L
D) 1.0 mg/L
, Answer: B
Rationale: TCEQ requires a minimum 0.2 mg/L free chlorine residual.
9. The process of adding chemicals to water to remove suspended particles is:
A) Filtration
B) *Coagulation
C) Disinfection
D) Sedimentation
Answer: B
Rationale: Coagulation neutralizes particle charges to form floc.
10. Flocculation is the process of:
A) Adding coagulants
B) *Gentle mixing to form larger floc
C) Settling floc
D) Filtering floc
Answer: B
Rationale: Flocculation encourages particles to clump together.
11. Sedimentation removes floc by:
A) *Gravity settling
B) Filtration
