Texas Water Class C Surface Water Operator Exam | TCEQ
Complete Exam Prep, Practice QUESTIONs & Detailed
Rationales 2026/2027
QUESTION 1
If you are treating 1.0 MGD of water and the required coagulant dosage
is 2.0 mg/L, how many pounds of chemical will you feed per day? (Use
8.34 lb/gal).
A. 8.34 lbs
B. 16.68 lbs
C. 4.17 lbs
D. 33.36 lbs
Correct Answer: B. 16.68 lbs
Detailed Rationale: Formula: Flow (MGD) × Dose (mg/L) × 8.34 =
lbs/day. 1.0 × 2.0 × 8.34 = 16.68 lbs/day.
,QUESTION 2
What is the primary function of the "coagulation" process?
A. To kill bacteria.
B. To neutralize the electrical charges on particles, causing them to
clump together.
C. To remove dissolved minerals.
D. To increase the pH of the water.
Correct Answer: B. To neutralize the electrical charges on particles,
causing them to clump together.
Detailed Rationale: Colloidal particles in surface water have a negative
charge, causing them to repel each other. Coagulants (like alum)
provide positive charges to neutralize them, allowing flocculation to
begin.
QUESTION 3
Which of the following is the most likely cause of "filter breakthrough"?
,A. The filter has been running for a very short time.
B. The floc is too large.
C. Excessive head loss or improper coagulation causing particles to pass
through the filter media.
D. The water temperature is too low.
Correct Answer: C. Excessive head loss or improper coagulation causing
particles to pass through the filter media.
Detailed Rationale: Breakthrough occurs when particles migrate
through the filter bed because the filter is "blinded" or exhausted, or
because the floc was not formed properly upstream.
QUESTION 4
What is the purpose of "backwashing" a rapid sand filter?
A. To clean the filter media by reversing the flow of water.
, B. To increase the production rate of the plant.
C. To add chlorine to the filter.
D. To test the water quality.
Correct Answer: A. To clean the filter media by reversing the flow of
water.
Detailed Rationale: Backwashing expands the filter bed, allowing
trapped particles to be flushed out into the washwater troughs.
QUESTION 5
According to TCEQ, what is the maximum turbidity level that must not
be exceeded in 95% of filtered water samples?
A. 0.1 NTU
B. 0.3 NTU
C. 1.0 NTU
Complete Exam Prep, Practice QUESTIONs & Detailed
Rationales 2026/2027
QUESTION 1
If you are treating 1.0 MGD of water and the required coagulant dosage
is 2.0 mg/L, how many pounds of chemical will you feed per day? (Use
8.34 lb/gal).
A. 8.34 lbs
B. 16.68 lbs
C. 4.17 lbs
D. 33.36 lbs
Correct Answer: B. 16.68 lbs
Detailed Rationale: Formula: Flow (MGD) × Dose (mg/L) × 8.34 =
lbs/day. 1.0 × 2.0 × 8.34 = 16.68 lbs/day.
,QUESTION 2
What is the primary function of the "coagulation" process?
A. To kill bacteria.
B. To neutralize the electrical charges on particles, causing them to
clump together.
C. To remove dissolved minerals.
D. To increase the pH of the water.
Correct Answer: B. To neutralize the electrical charges on particles,
causing them to clump together.
Detailed Rationale: Colloidal particles in surface water have a negative
charge, causing them to repel each other. Coagulants (like alum)
provide positive charges to neutralize them, allowing flocculation to
begin.
QUESTION 3
Which of the following is the most likely cause of "filter breakthrough"?
,A. The filter has been running for a very short time.
B. The floc is too large.
C. Excessive head loss or improper coagulation causing particles to pass
through the filter media.
D. The water temperature is too low.
Correct Answer: C. Excessive head loss or improper coagulation causing
particles to pass through the filter media.
Detailed Rationale: Breakthrough occurs when particles migrate
through the filter bed because the filter is "blinded" or exhausted, or
because the floc was not formed properly upstream.
QUESTION 4
What is the purpose of "backwashing" a rapid sand filter?
A. To clean the filter media by reversing the flow of water.
, B. To increase the production rate of the plant.
C. To add chlorine to the filter.
D. To test the water quality.
Correct Answer: A. To clean the filter media by reversing the flow of
water.
Detailed Rationale: Backwashing expands the filter bed, allowing
trapped particles to be flushed out into the washwater troughs.
QUESTION 5
According to TCEQ, what is the maximum turbidity level that must not
be exceeded in 95% of filtered water samples?
A. 0.1 NTU
B. 0.3 NTU
C. 1.0 NTU
