TEXAS WASTEWATER COLLECTION SYSTEM OPERATOR
CLASS II EXAM – QUESTIONS AND
ANSWERS | VERIFIED AND WELL DETAILED ANSWERS
| PLUS RATIONALES | GUARANTEED PASS | LATEST EXAM
UPDATE | EXAM PREP | STUDY GUIDE |
PRACTICE TEST
1. Which of the following is the primary
purpose of a lift station in a wastewater
collection system?
A. To provide secondary treatment for sewage.
B. To reduce the organic load of incoming
wastewater.
C. To pump wastewater to a higher elevation.
D. To remove grit and large debris from the
influent.
✅ Correct Answer: C. To pump wastewater to a higher elevation.
💡 Rationale:
The fundamental purpose of a lift
station is to elevate wastewater from a lower
level to a higher level, allowing gravity to
continue transporting the flow toward the
treatment plant when
,the natural topography or pipeline depth
makes gravity flow impossible.
2. When performing a routine inspection of a
wet well, which hazard should an operator be
most concerned with regarding atmospheric
conditions?
A. Excess nitrogen levels.
B. Oxygen deficiency and toxic gases like
hydrogen sulfide.
C. High humidity causing slip hazards.
D. Excessive noise pollution from the pump
motors.
✅ Correct Answer: B. Oxygen deficiency and toxic gases like
hydrogen sulfide.
💡 Rationale:
Wet wells are classified as confined
spaces. They often contain hazardous
atmospheres, including hydrogen sulfide
(H2S), which is toxic and potentially fatal, as
well as methane or carbon dioxide that can
displace oxygen, leading to asphyxiation.
,3. What is the minimum velocity required in a
gravity sewer to prevent the deposition of
solids and the resulting buildup of hydrogen
sulfide?
A. 1.0 feet per second (fps).
B. 2.0 feet per second (fps).
C. 3.0 feet per second (fps).
D. 4.5 feet per second (fps).
✅ Correct Answer: B. 2.0 feet per second (fps).
💡 Rationale:
A minimum velocity of 2.0 feet per
second at full or half-full flow is the industry
standard (often referred to as "self-cleansing
velocity") to ensure that suspended solids
remain in suspension and do not settle, which
prevents odor issues and pipe blockages.
4. A centrifugal pump is failing to discharge
water despite the motor running. What is the
most likely cause?
A. The pump is air-bound or has lost prime.
B. The impeller is spinning too fast.
, C. The discharge valve is too wide open.
D. The influent flow is too high.
✅ Correct Answer: A. The pump is air-bound or has lost prime.
💡 Rationale:
If a centrifugal pump runs but does not
move fluid, the most common mechanical
issue is a loss of prime (air in the pump
casing). The impeller cannot create the
necessary vacuum to draw water if the casing
is filled with air rather than liquid.
5. Which type of pipe is most commonly used
for small-diameter service laterals in modern
construction due to its flexibility and
resistance to root intrusion?
A. Clay pipe.
B. Concrete pipe.
C. Polyvinyl Chloride (PVC) pipe.
D. Brick masonry.
✅ Correct Answer: C. Polyvinyl Chloride (PVC) pipe.
CLASS II EXAM – QUESTIONS AND
ANSWERS | VERIFIED AND WELL DETAILED ANSWERS
| PLUS RATIONALES | GUARANTEED PASS | LATEST EXAM
UPDATE | EXAM PREP | STUDY GUIDE |
PRACTICE TEST
1. Which of the following is the primary
purpose of a lift station in a wastewater
collection system?
A. To provide secondary treatment for sewage.
B. To reduce the organic load of incoming
wastewater.
C. To pump wastewater to a higher elevation.
D. To remove grit and large debris from the
influent.
✅ Correct Answer: C. To pump wastewater to a higher elevation.
💡 Rationale:
The fundamental purpose of a lift
station is to elevate wastewater from a lower
level to a higher level, allowing gravity to
continue transporting the flow toward the
treatment plant when
,the natural topography or pipeline depth
makes gravity flow impossible.
2. When performing a routine inspection of a
wet well, which hazard should an operator be
most concerned with regarding atmospheric
conditions?
A. Excess nitrogen levels.
B. Oxygen deficiency and toxic gases like
hydrogen sulfide.
C. High humidity causing slip hazards.
D. Excessive noise pollution from the pump
motors.
✅ Correct Answer: B. Oxygen deficiency and toxic gases like
hydrogen sulfide.
💡 Rationale:
Wet wells are classified as confined
spaces. They often contain hazardous
atmospheres, including hydrogen sulfide
(H2S), which is toxic and potentially fatal, as
well as methane or carbon dioxide that can
displace oxygen, leading to asphyxiation.
,3. What is the minimum velocity required in a
gravity sewer to prevent the deposition of
solids and the resulting buildup of hydrogen
sulfide?
A. 1.0 feet per second (fps).
B. 2.0 feet per second (fps).
C. 3.0 feet per second (fps).
D. 4.5 feet per second (fps).
✅ Correct Answer: B. 2.0 feet per second (fps).
💡 Rationale:
A minimum velocity of 2.0 feet per
second at full or half-full flow is the industry
standard (often referred to as "self-cleansing
velocity") to ensure that suspended solids
remain in suspension and do not settle, which
prevents odor issues and pipe blockages.
4. A centrifugal pump is failing to discharge
water despite the motor running. What is the
most likely cause?
A. The pump is air-bound or has lost prime.
B. The impeller is spinning too fast.
, C. The discharge valve is too wide open.
D. The influent flow is too high.
✅ Correct Answer: A. The pump is air-bound or has lost prime.
💡 Rationale:
If a centrifugal pump runs but does not
move fluid, the most common mechanical
issue is a loss of prime (air in the pump
casing). The impeller cannot create the
necessary vacuum to draw water if the casing
is filled with air rather than liquid.
5. Which type of pipe is most commonly used
for small-diameter service laterals in modern
construction due to its flexibility and
resistance to root intrusion?
A. Clay pipe.
B. Concrete pipe.
C. Polyvinyl Chloride (PVC) pipe.
D. Brick masonry.
✅ Correct Answer: C. Polyvinyl Chloride (PVC) pipe.
