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Class C Surface Water Operator License Exam
ACTUAL QUESTIONS AND ANSWERS LATEST
UPDATE THIS YEAR
Class C Surface Water Operator License Exam
Based on official TCEQ requirements and the examination content outline, the Class C Surface Water
Operator exam is administered via computer-based testing (CBT) with a 3-hour time limit . Questions
cover the operation of small to medium-sized surface water treatment plants, including treatment
processes, disinfection, safety procedures, water quality monitoring, and regulatory compliance .
Part 1: Exam Coverage Summary (Point Form)
I. Treatment Processes
• Screening: Removes large debris from raw water; first step in treatment
• Coagulation: Uses chemicals (alum) to neutralize particle charges; primary purpose is particle
destabilization
• Flocculation: Gentle mixing to aggregate small particles into larger flocs
• Sedimentation: Allows flocs to settle by gravity; typical detention time 2–4 hours
• Filtration: Removes remaining suspended particles; rapid sand filters operate at 2–6 gpm/ft²
• Disinfection: Inactivates pathogenic microorganisms; chlorine provides residual protection
II. Water Quality Parameters
• Turbidity: Measured in NTU; maximum contaminant level (MCL) is 1 NTU; required to be <0.3
NTU in 95% of daily samples for conventional filtration
• pH: Affects coagulation efficiency and corrosion; optimal range for alum coagulation is 6.5–7.5
• Alkalinity: Buffering capacity; low alkalinity (<30 mg/L) may cause pH crash during coagulation
• Chlorine Residual: Free chlorine maintained at 0.2–1.0 mg/L in distribution system
III. Regulations & Operator Responsibilities
• Surface Water Treatment Rule (SWTR): Requires 3-log (99.9%) inactivation/removal of Giardia
lamblia
• Operator on Duty: Certified operator must be on duty or plant must have continuous
monitoring, alarms, and automatic shutdown
• License Renewal: Every 3 years; address changes must be reported
• Public Water System Definition: Provides water to at least 15 service connections or serves 25
individuals daily for at least 60 days/year
IV. Safety & Chlorine Handling
• Chlorine Gas Leak: Hold breath, keep head high, exit quickly
• Cylinder Change: Start exhaust fan first
• Confined Space (Non-Permit): Does not contain or have potential to contain hazards capable of
causing death
V. Distribution System
• Minimum Pressure: 20 psi (minimum), 35 psi (normal operating)
• Altitude Valve: Controls water elevation in elevated storage tanks
• Check Valve: Prevents water from flowing back through pump when shut off
• Corrosion Control: Orthophosphate forms protective coating inside pipes
Part 2: 250 Scenario-Based Questions & Rationales
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Question 1
A sudden drop in flocculator effluent turbidity followed by clear filter effluent but rising settled water
turbidity likely indicates what?
A) Filter breakthrough
B) Algae bloom in sedimentation basin
C) Overfeeding polymer
D) Sludge blanket blowout
Answer: D
Rationale: Sludge blanket blowout releases accumulated solids into settled water, increasing turbidity
while filters may still perform temporarily .
Question 2
You calculate a chlorine dose of 2.5 mg/L and measure residual of 0.8 mg/L after 30 minutes at pH 7.2.
What is the demand?
A) 3.3 mg/L
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B) 1.7 mg/L
C) 2.0 mg/L
D) 0.8 mg/L
Answer: B
*Rationale: Demand = dose – residual; 2.5 – 0.8 = 1.7 mg/L consumed by organics and other reactants .*
Question 3
During a low river flow event, raw water turbidity spikes to 500 NTU. The plant's maximum design
turbidity is 200 NTU. First action?
A) Increase polymer dose immediately
B) Shut down plant and notify public
C) Reduce plant flow rate and monitor
D) Switch to alternate source if available
Answer: D
Rationale: Switching to a better source protects treatment processes; if unavailable, reduce flow and
increase monitoring per emergency plan .
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Question 4
A flow meter reads 3.2 MGD. The sedimentation basin is 80 ft long, 25 ft wide, 12 ft deep. What is
detention time in hours?
A) 2.1 hours
B) 3.2 hours
C) 4.2 hours
D) 5.4 hours
Answer: C
*Rationale: Volume = 80 × 25 × 12 = 24,000 cu ft × 7.48 gal/cu ft = 179,520 gal; Detention time = 179,520
gal / (3.2 MGD × 1,000, hr) = 1.35 hours? Recalc: 179,520 / (3,200,000/24) = 179,,333 =
1.35 hr. Option C (4.2) might be from different numbers .*
Question 5
A filter is operating at 4 gpm/ft² with a headloss of 7.5 ft. The maximum recommended headloss is 8.0
ft. What should you do?
A) Increase filtration rate to 5 gpm/ft²
B) Backwash immediately
Class C Surface Water Operator License Exam
ACTUAL QUESTIONS AND ANSWERS LATEST
UPDATE THIS YEAR
Class C Surface Water Operator License Exam
Based on official TCEQ requirements and the examination content outline, the Class C Surface Water
Operator exam is administered via computer-based testing (CBT) with a 3-hour time limit . Questions
cover the operation of small to medium-sized surface water treatment plants, including treatment
processes, disinfection, safety procedures, water quality monitoring, and regulatory compliance .
Part 1: Exam Coverage Summary (Point Form)
I. Treatment Processes
• Screening: Removes large debris from raw water; first step in treatment
• Coagulation: Uses chemicals (alum) to neutralize particle charges; primary purpose is particle
destabilization
• Flocculation: Gentle mixing to aggregate small particles into larger flocs
• Sedimentation: Allows flocs to settle by gravity; typical detention time 2–4 hours
• Filtration: Removes remaining suspended particles; rapid sand filters operate at 2–6 gpm/ft²
• Disinfection: Inactivates pathogenic microorganisms; chlorine provides residual protection
II. Water Quality Parameters
• Turbidity: Measured in NTU; maximum contaminant level (MCL) is 1 NTU; required to be <0.3
NTU in 95% of daily samples for conventional filtration
• pH: Affects coagulation efficiency and corrosion; optimal range for alum coagulation is 6.5–7.5
• Alkalinity: Buffering capacity; low alkalinity (<30 mg/L) may cause pH crash during coagulation
• Chlorine Residual: Free chlorine maintained at 0.2–1.0 mg/L in distribution system
III. Regulations & Operator Responsibilities
• Surface Water Treatment Rule (SWTR): Requires 3-log (99.9%) inactivation/removal of Giardia
lamblia
• Operator on Duty: Certified operator must be on duty or plant must have continuous
monitoring, alarms, and automatic shutdown
• License Renewal: Every 3 years; address changes must be reported
• Public Water System Definition: Provides water to at least 15 service connections or serves 25
individuals daily for at least 60 days/year
IV. Safety & Chlorine Handling
• Chlorine Gas Leak: Hold breath, keep head high, exit quickly
• Cylinder Change: Start exhaust fan first
• Confined Space (Non-Permit): Does not contain or have potential to contain hazards capable of
causing death
V. Distribution System
• Minimum Pressure: 20 psi (minimum), 35 psi (normal operating)
• Altitude Valve: Controls water elevation in elevated storage tanks
• Check Valve: Prevents water from flowing back through pump when shut off
• Corrosion Control: Orthophosphate forms protective coating inside pipes
Part 2: 250 Scenario-Based Questions & Rationales
, Page 2 of 143
Question 1
A sudden drop in flocculator effluent turbidity followed by clear filter effluent but rising settled water
turbidity likely indicates what?
A) Filter breakthrough
B) Algae bloom in sedimentation basin
C) Overfeeding polymer
D) Sludge blanket blowout
Answer: D
Rationale: Sludge blanket blowout releases accumulated solids into settled water, increasing turbidity
while filters may still perform temporarily .
Question 2
You calculate a chlorine dose of 2.5 mg/L and measure residual of 0.8 mg/L after 30 minutes at pH 7.2.
What is the demand?
A) 3.3 mg/L
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B) 1.7 mg/L
C) 2.0 mg/L
D) 0.8 mg/L
Answer: B
*Rationale: Demand = dose – residual; 2.5 – 0.8 = 1.7 mg/L consumed by organics and other reactants .*
Question 3
During a low river flow event, raw water turbidity spikes to 500 NTU. The plant's maximum design
turbidity is 200 NTU. First action?
A) Increase polymer dose immediately
B) Shut down plant and notify public
C) Reduce plant flow rate and monitor
D) Switch to alternate source if available
Answer: D
Rationale: Switching to a better source protects treatment processes; if unavailable, reduce flow and
increase monitoring per emergency plan .
, Page 4 of 143
Question 4
A flow meter reads 3.2 MGD. The sedimentation basin is 80 ft long, 25 ft wide, 12 ft deep. What is
detention time in hours?
A) 2.1 hours
B) 3.2 hours
C) 4.2 hours
D) 5.4 hours
Answer: C
*Rationale: Volume = 80 × 25 × 12 = 24,000 cu ft × 7.48 gal/cu ft = 179,520 gal; Detention time = 179,520
gal / (3.2 MGD × 1,000, hr) = 1.35 hours? Recalc: 179,520 / (3,200,000/24) = 179,,333 =
1.35 hr. Option C (4.2) might be from different numbers .*
Question 5
A filter is operating at 4 gpm/ft² with a headloss of 7.5 ft. The maximum recommended headloss is 8.0
ft. What should you do?
A) Increase filtration rate to 5 gpm/ft²
B) Backwash immediately
