TCEQ Class C Water License Exam –
Complete Questions and Answers Texas
Commission on Environmental Quality
(TCEQ) Full Study Guide with 100% Pass
Rate
Question 1
When treating surface Water, the process of coagularon will be most affected by the
Correct Answer
pH, alkalinity, temperature, and chemical Dosage
Question 2
The distance from the water level in the well to the centerline of a pump is
Correct Answer
Static suction head
Question 3
One foot of water inside a storage vessel will raise a pressure gauge at the bottom of
the vessel by
Correct Answer
0.433 lbs. (1 ft. Water creates 0.433 psi of pressure)
Page 1 of 93
,Question 4
Livestock and septic tanks must be no closer than ________ to a public well.
Correct Answer
50 feet
Question 1: Which of the following is the primary purpose of coagulation in
conventional surface water treatment?
A. To kill pathogenic microorganisms
B. To remove dissolved gases
C. To destabilize and aggregate colloidal particles
D. To adjust the pH of the finished water
CORRECT ANSWER: C. To destabilize and aggregate colloidal particles
Rationale: Coagulation involves the addition of chemicals such as aluminum sulfate
or ferric chloride to neutralize the negative charges on colloidal particles, allowing
them to form larger aggregates (flocs) that can be removed by sedimentation and
filtration.
Question 2: According to TCEQ regulations, what is the maximum contaminant
level (MCL) for total coliform bacteria in public water systems?
A. 5% of samples positive in a month
B. Zero detectable organisms
C. 1 colony-forming unit per 100 mL
D. 10% of samples positive in a month
CORRECT ANSWER: A. 5% of samples positive in a month
Rationale: Under the Total Coliform Rule and TCEQ standards, a public water system
collecting at least 40 samples per month is in violation if more than 5.0% of samples
are total coliform-positive. Systems collecting fewer than 40 samples violate if more
than one sample is positive.
Question 3: What is the primary function of a clearwell in a water treatment
plant?
A. To store raw water prior to treatment
B. To provide contact time for disinfection and store finished water
C. To settle out large debris from source water
D. To aerate water for iron removal
CORRECT ANSWER: B. To provide contact time for disinfection and store
finished water
Page 2 of 93
,Rationale: A clearwell is a finished-water storage facility located after filtration and
disinfection. It ensures adequate chlorine contact time (CT) for pathogen
inactivation and provides operational storage before distribution.
Question 4: Which chemical is most commonly used for disinfection of public
water supplies in Texas?
A. Ozone
B. Chlorine or chlorine compounds
C. Ultraviolet light only
D. Potassium permanganate
CORRECT ANSWER: B. Chlorine or chlorine compounds
Rationale: Free chlorine and chloramines are the predominant disinfectants used by
Texas public water systems because of their effectiveness, residual-maintaining
capability, and regulatory acceptance under TCEQ rules.
Question 5: What does the term “CT” represent in water disinfection?
A. Chlorine residual times temperature
B. Concentration of disinfectant times contact time
C. Chemical treatment dosage
D. Coliform test result
CORRECT ANSWER: B. Concentration of disinfectant times contact time
Rationale: CT is the product of residual disinfectant concentration (C in mg/L) and
contact time (T in minutes). It is used to calculate the inactivation credit for viruses,
Giardia, and other pathogens under the Surface Water Treatment Rule.
Question 6: Which of the following is a common cause of taste and odor
problems in surface water supplies?
A. High hardness
B. Algae blooms producing geosmin or MIB
C. Low pH
D. Excess fluoride
CORRECT ANSWER: B. Algae blooms producing geosmin or MIB
Rationale: Certain blue-green algae and actinomycetes produce geosmin and 2-
methylisoborneol (MIB), which cause earthy or musty tastes and odors even at
nanogram-per-liter concentrations.
Question 7: What is the purpose of a backflow prevention assembly in a public
water system?
Page 3 of 93
, A. To increase water pressure
B. To prevent contaminated water from flowing back into the potable system
C. To measure water flow
D. To remove sediment
CORRECT ANSWER: B. To prevent contaminated water from flowing back into
the potable system
Rationale: Backflow prevention devices (such as reduced-pressure zone assemblies
or double-check valves) protect the public water supply from contamination caused
by backpressure or backsiphonage from customer premises.
Question 8: Which type of pump is most commonly used for high-volume,
low-head applications in water treatment plants?
A. Positive-displacement piston pump
B. Centrifugal pump
C. Diaphragm pump
D. Peristaltic pump
CORRECT ANSWER: B. Centrifugal pump
Rationale: Centrifugal pumps are the workhorses of water treatment and
distribution because they efficiently move large volumes of water at relatively low
pressures and are simple to operate and maintain.
Question 9: Under TCEQ rules, how often must a Class C water operator renew
their license?
A. Every year
B. Every two years
C. Every three years
D. Every five years
CORRECT ANSWER: C. Every three years
Rationale: TCEQ water operator licenses (Classes A, B, C, and D) are issued for three-
year terms and require continuing education hours for renewal.
Question 10: What is the most effective method for removing turbidity from
surface water?
A. Aeration alone
B. Coagulation, flocculation, sedimentation, and filtration
C. Disinfection only
D. Softening
CORRECT ANSWER: B. Coagulation, flocculation, sedimentation, and filtration
Page 4 of 93
Complete Questions and Answers Texas
Commission on Environmental Quality
(TCEQ) Full Study Guide with 100% Pass
Rate
Question 1
When treating surface Water, the process of coagularon will be most affected by the
Correct Answer
pH, alkalinity, temperature, and chemical Dosage
Question 2
The distance from the water level in the well to the centerline of a pump is
Correct Answer
Static suction head
Question 3
One foot of water inside a storage vessel will raise a pressure gauge at the bottom of
the vessel by
Correct Answer
0.433 lbs. (1 ft. Water creates 0.433 psi of pressure)
Page 1 of 93
,Question 4
Livestock and septic tanks must be no closer than ________ to a public well.
Correct Answer
50 feet
Question 1: Which of the following is the primary purpose of coagulation in
conventional surface water treatment?
A. To kill pathogenic microorganisms
B. To remove dissolved gases
C. To destabilize and aggregate colloidal particles
D. To adjust the pH of the finished water
CORRECT ANSWER: C. To destabilize and aggregate colloidal particles
Rationale: Coagulation involves the addition of chemicals such as aluminum sulfate
or ferric chloride to neutralize the negative charges on colloidal particles, allowing
them to form larger aggregates (flocs) that can be removed by sedimentation and
filtration.
Question 2: According to TCEQ regulations, what is the maximum contaminant
level (MCL) for total coliform bacteria in public water systems?
A. 5% of samples positive in a month
B. Zero detectable organisms
C. 1 colony-forming unit per 100 mL
D. 10% of samples positive in a month
CORRECT ANSWER: A. 5% of samples positive in a month
Rationale: Under the Total Coliform Rule and TCEQ standards, a public water system
collecting at least 40 samples per month is in violation if more than 5.0% of samples
are total coliform-positive. Systems collecting fewer than 40 samples violate if more
than one sample is positive.
Question 3: What is the primary function of a clearwell in a water treatment
plant?
A. To store raw water prior to treatment
B. To provide contact time for disinfection and store finished water
C. To settle out large debris from source water
D. To aerate water for iron removal
CORRECT ANSWER: B. To provide contact time for disinfection and store
finished water
Page 2 of 93
,Rationale: A clearwell is a finished-water storage facility located after filtration and
disinfection. It ensures adequate chlorine contact time (CT) for pathogen
inactivation and provides operational storage before distribution.
Question 4: Which chemical is most commonly used for disinfection of public
water supplies in Texas?
A. Ozone
B. Chlorine or chlorine compounds
C. Ultraviolet light only
D. Potassium permanganate
CORRECT ANSWER: B. Chlorine or chlorine compounds
Rationale: Free chlorine and chloramines are the predominant disinfectants used by
Texas public water systems because of their effectiveness, residual-maintaining
capability, and regulatory acceptance under TCEQ rules.
Question 5: What does the term “CT” represent in water disinfection?
A. Chlorine residual times temperature
B. Concentration of disinfectant times contact time
C. Chemical treatment dosage
D. Coliform test result
CORRECT ANSWER: B. Concentration of disinfectant times contact time
Rationale: CT is the product of residual disinfectant concentration (C in mg/L) and
contact time (T in minutes). It is used to calculate the inactivation credit for viruses,
Giardia, and other pathogens under the Surface Water Treatment Rule.
Question 6: Which of the following is a common cause of taste and odor
problems in surface water supplies?
A. High hardness
B. Algae blooms producing geosmin or MIB
C. Low pH
D. Excess fluoride
CORRECT ANSWER: B. Algae blooms producing geosmin or MIB
Rationale: Certain blue-green algae and actinomycetes produce geosmin and 2-
methylisoborneol (MIB), which cause earthy or musty tastes and odors even at
nanogram-per-liter concentrations.
Question 7: What is the purpose of a backflow prevention assembly in a public
water system?
Page 3 of 93
, A. To increase water pressure
B. To prevent contaminated water from flowing back into the potable system
C. To measure water flow
D. To remove sediment
CORRECT ANSWER: B. To prevent contaminated water from flowing back into
the potable system
Rationale: Backflow prevention devices (such as reduced-pressure zone assemblies
or double-check valves) protect the public water supply from contamination caused
by backpressure or backsiphonage from customer premises.
Question 8: Which type of pump is most commonly used for high-volume,
low-head applications in water treatment plants?
A. Positive-displacement piston pump
B. Centrifugal pump
C. Diaphragm pump
D. Peristaltic pump
CORRECT ANSWER: B. Centrifugal pump
Rationale: Centrifugal pumps are the workhorses of water treatment and
distribution because they efficiently move large volumes of water at relatively low
pressures and are simple to operate and maintain.
Question 9: Under TCEQ rules, how often must a Class C water operator renew
their license?
A. Every year
B. Every two years
C. Every three years
D. Every five years
CORRECT ANSWER: C. Every three years
Rationale: TCEQ water operator licenses (Classes A, B, C, and D) are issued for three-
year terms and require continuing education hours for renewal.
Question 10: What is the most effective method for removing turbidity from
surface water?
A. Aeration alone
B. Coagulation, flocculation, sedimentation, and filtration
C. Disinfection only
D. Softening
CORRECT ANSWER: B. Coagulation, flocculation, sedimentation, and filtration
Page 4 of 93
