TCEQ CLASS B SURFACE WATER LICENSE EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED ANSWERS)
PLUS RATIONALES 2026 Q&A | LATEST EXAM UPDATE 2026/2027
SECTION ONE: QUESTIONS 1–100
Question 1
Which reservoir layer is characterized by the warmest temperatures and is typically well-mixed during summer
stratification?
A. Hypolimnion
B. Metalimnion
C. Thermocline
D. Epilimnion
🟢 D. Epilimnion
🔴 RATIONALE: The epilimnion is the warm, upper layer of a stratified reservoir that is exposed to solar
radiation and wind mixing, making it the warmest zone .
Question 2
What is the primary purpose of a "flash mixer" in a conventional surface water treatment plant?
A. To increase dissolved oxygen levels in the raw water
B. To evenly disperse coagulant chemicals throughout the raw water
C. To form large, settleable floc particles
D. To remove algae through mechanical agitation
,🟢 B. To evenly disperse coagulant chemicals throughout the raw water
🔴 RATIONALE: The flash mixer is designed for rapid, violent mixing immediately after coagulants are added to
ensure uniform dispersion for particle destabilization before gentle flocculation begins .
Question 3
According to TCEQ regulations, what is the minimum free chlorine residual required at the far reaches of the
distribution system?
A. 0.5 mg/L
B. 0.2 mg/L
C. 1.0 mg/L
D. 0.8 mg/L
🟢 B. 0.2 mg/L
🔴 RATIONALE: Free chlorine residual must be at least 0.2 mg/L at all points in the distribution system .
Question 4
What is the CT concept in disinfection?
A. Chlorine concentration and temperature
B. Contact time and pH
C. Concentration of disinfectant and contact time
D. Turbidity and flow rate
🟢 C. Concentration of disinfectant and contact time
🔴 RATIONALE: CT is the product of disinfectant concentration (C) in mg/L and contact time (T) in minutes,
quantifying the disinfection dose applied .
Question 5
An operator notices a "rotten egg" smell in the raw water coming from the reservoir's bottom layer. This is most
likely caused by:
,A. Excessive copper sulfate treatment
B. Anaerobic decomposition producing hydrogen sulfide
C. A sudden increase in pH due to algal activity
D. An overdose of chlorine during pre-chlorination
🟢 B. Anaerobic decomposition producing hydrogen sulfide
🔴 RATIONALE: Low dissolved oxygen in the hypolimnion creates anaerobic conditions where sulfate-reducing
bacteria produce hydrogen sulfide (H₂S), which has a characteristic rotten egg odor .
Question 6
The rate-of-flow controller in a filter is typically installed in the:
A. Influent line
B. Backwash line
C. Effluent line
D. Wash water trough
🟢 C. Effluent line
🔴 RATIONALE: A rate-of-flow controller, installed in the filter effluent line, automatically maintains the desired
filtration rate .
Question 7
What is the maximum contaminant level (MCL) for nitrate (as N) in drinking water?
A. 5 mg/L
B. 10 mg/L
C. 15 mg/L
D. 20 mg/L
🟢 B. 10 mg/L
🔴 RATIONALE: The nitrate MCL established by the Safe Drinking Water Act is 10 mg/L as nitrogen .
, Question 8
During cold water conditions, the same dose of alum will typically result in:
A. Faster floc formation
B. Poorer floc formation and settling
C. Higher finished water pH
D. Lower chlorine demand
🟢 B. Poorer floc formation and settling
🔴 RATIONALE: Cold water increases viscosity and slows coagulation reaction kinetics, usually resulting in
smaller, lighter floc that does not settle as well .
Question 9
What is the standard rapid sand filter flow rate under normal operating conditions?
A. 1-2 GPM/ft²
B. 2-4 GPM/ft²
C. 5-8 GPM/ft²
D. 10-12 GPM/ft²
🟢 B. 2-4 GPM/ft²
🔴 RATIONALE: Under standard operating conditions, a rapid sand filter operates at 2 to 4 gallons per minute
per square foot of filter area .
Question 10
A system exceeds 5 NTU in the combined filter effluent. What must the system do?
A. Nothing; this is acceptable
B. Notify the public drinking water program by the next business day
C. Issue a boil water notice immediately
D. Shut down the entire plant
PLUS RATIONALES 2026 Q&A | LATEST EXAM UPDATE 2026/2027
SECTION ONE: QUESTIONS 1–100
Question 1
Which reservoir layer is characterized by the warmest temperatures and is typically well-mixed during summer
stratification?
A. Hypolimnion
B. Metalimnion
C. Thermocline
D. Epilimnion
🟢 D. Epilimnion
🔴 RATIONALE: The epilimnion is the warm, upper layer of a stratified reservoir that is exposed to solar
radiation and wind mixing, making it the warmest zone .
Question 2
What is the primary purpose of a "flash mixer" in a conventional surface water treatment plant?
A. To increase dissolved oxygen levels in the raw water
B. To evenly disperse coagulant chemicals throughout the raw water
C. To form large, settleable floc particles
D. To remove algae through mechanical agitation
,🟢 B. To evenly disperse coagulant chemicals throughout the raw water
🔴 RATIONALE: The flash mixer is designed for rapid, violent mixing immediately after coagulants are added to
ensure uniform dispersion for particle destabilization before gentle flocculation begins .
Question 3
According to TCEQ regulations, what is the minimum free chlorine residual required at the far reaches of the
distribution system?
A. 0.5 mg/L
B. 0.2 mg/L
C. 1.0 mg/L
D. 0.8 mg/L
🟢 B. 0.2 mg/L
🔴 RATIONALE: Free chlorine residual must be at least 0.2 mg/L at all points in the distribution system .
Question 4
What is the CT concept in disinfection?
A. Chlorine concentration and temperature
B. Contact time and pH
C. Concentration of disinfectant and contact time
D. Turbidity and flow rate
🟢 C. Concentration of disinfectant and contact time
🔴 RATIONALE: CT is the product of disinfectant concentration (C) in mg/L and contact time (T) in minutes,
quantifying the disinfection dose applied .
Question 5
An operator notices a "rotten egg" smell in the raw water coming from the reservoir's bottom layer. This is most
likely caused by:
,A. Excessive copper sulfate treatment
B. Anaerobic decomposition producing hydrogen sulfide
C. A sudden increase in pH due to algal activity
D. An overdose of chlorine during pre-chlorination
🟢 B. Anaerobic decomposition producing hydrogen sulfide
🔴 RATIONALE: Low dissolved oxygen in the hypolimnion creates anaerobic conditions where sulfate-reducing
bacteria produce hydrogen sulfide (H₂S), which has a characteristic rotten egg odor .
Question 6
The rate-of-flow controller in a filter is typically installed in the:
A. Influent line
B. Backwash line
C. Effluent line
D. Wash water trough
🟢 C. Effluent line
🔴 RATIONALE: A rate-of-flow controller, installed in the filter effluent line, automatically maintains the desired
filtration rate .
Question 7
What is the maximum contaminant level (MCL) for nitrate (as N) in drinking water?
A. 5 mg/L
B. 10 mg/L
C. 15 mg/L
D. 20 mg/L
🟢 B. 10 mg/L
🔴 RATIONALE: The nitrate MCL established by the Safe Drinking Water Act is 10 mg/L as nitrogen .
, Question 8
During cold water conditions, the same dose of alum will typically result in:
A. Faster floc formation
B. Poorer floc formation and settling
C. Higher finished water pH
D. Lower chlorine demand
🟢 B. Poorer floc formation and settling
🔴 RATIONALE: Cold water increases viscosity and slows coagulation reaction kinetics, usually resulting in
smaller, lighter floc that does not settle as well .
Question 9
What is the standard rapid sand filter flow rate under normal operating conditions?
A. 1-2 GPM/ft²
B. 2-4 GPM/ft²
C. 5-8 GPM/ft²
D. 10-12 GPM/ft²
🟢 B. 2-4 GPM/ft²
🔴 RATIONALE: Under standard operating conditions, a rapid sand filter operates at 2 to 4 gallons per minute
per square foot of filter area .
Question 10
A system exceeds 5 NTU in the combined filter effluent. What must the system do?
A. Nothing; this is acceptable
B. Notify the public drinking water program by the next business day
C. Issue a boil water notice immediately
D. Shut down the entire plant
