TCEQ Wastewater Collection
System Operator Class III — Form B
Exam Questions and Correct
Answers with Detailed Rationales |
2026/2027 Edition | Exam Prep
Study Guide PDF
1. In a wastewater collection system, what is the primary purpose
of maintaining adequate minimum velocity in a gravity sewer?
A. To increase pipe pressure
B. To prevent wastewater from becoming too diluted
C. To minimize deposition of solids and maintain self-cleansing
conditions
D. To eliminate the need for routine cleaning
Answer: C. To minimize deposition of solids and maintain self-
cleansing conditions
Rationale: Adequate velocity helps keep suspended solids
moving through the sewer rather than allowing them to settle and
accumulate. Excessive deposition can reduce hydraulic capacity,
promote odors, and eventually contribute to blockages.
Maintaining appropriate design and operational velocities is
therefore an important part of collection-system management.
,2. A collection-system operator observes repeated sanitary sewer
overflows during intense rainfall. Which condition should be
investigated first?
A. Low chlorine residual at the treatment plant
B. Infiltration and inflow entering the collection system
C. Excessive dissolved oxygen in the receiving stream
D. Low alkalinity in the wastewater
Answer: B. Infiltration and inflow entering the collection
system
Rationale: Rainfall-related sewer overflows commonly indicate
excessive infiltration and inflow (I/I). Inflow can enter through
improper connections, roof drains, storm drains, and other direct
pathways, while infiltration enters through defective joints, cracks,
and groundwater intrusion. Identifying and reducing excessive I/I
can substantially reduce wet-weather hydraulic loading.
3. Which condition is most likely to cause hydrogen sulfide
formation in a collection system?
A. Highly turbulent, well-oxygenated wastewater
B. Warm, stagnant wastewater containing biodegradable organic
matter
C. Very low organic loading
D. Continuous exposure of wastewater to sunlight
Answer: B. Warm, stagnant wastewater containing
biodegradable organic matter
Rationale: Hydrogen sulfide is commonly associated with
anaerobic conditions in wastewater containing organic matter.
Stagnant or slow-moving wastewater allows oxygen to become
,depleted, creating conditions favorable for sulfate-reducing
microorganisms. Warmer temperatures generally accelerate
biological activity and can intensify odor and corrosion problems.
4. What is the primary operational concern associated with
hydrogen sulfide in a wastewater collection system?
A. It increases dissolved oxygen
B. It can create toxic exposure hazards and contribute to
corrosion
C. It prevents biological activity
D. It permanently disinfects sewer surfaces
Answer: B. It can create toxic exposure hazards and contribute
to corrosion
Rationale: Hydrogen sulfide is toxic and can present a serious
occupational hazard, particularly in confined spaces. It also
contributes to sewer corrosion because hydrogen sulfide can be
biologically converted to sulfuric acid under appropriate
conditions. Operators should use proper atmospheric monitoring
and confined-space procedures whenever required.
5. Which sewer feature is specifically designed to provide access
for inspection, cleaning, maintenance, and changes in sewer
alignment or elevation?
A. Air-release valve
B. Manhole
C. Backflow preventer
D. Sampling tap
, Answer: B. Manhole
Rationale: Manholes provide access to gravity collection sewers
for inspection, cleaning, maintenance, and other operational
activities. They are commonly located at changes in direction,
grade, pipe size, and at selected intervals along a sewer.
6. A force main discharges into a receiving manhole and produces
excessive turbulence and odor. Which operational change may
help reduce the problem?
A. Increase the discharge velocity as much as possible
B. Evaluate the discharge configuration and minimize excessive
turbulence
C. Remove all downstream manholes
D. Reduce all gravity sewer slopes
Answer: B. Evaluate the discharge configuration and minimize
excessive turbulence
Rationale: Excessive turbulence can increase agitation, release
dissolved gases, and contribute to odor problems. The discharge
arrangement should be evaluated to provide appropriate energy
dissipation and hydraulic conditions. Operators should consider
both hydraulic performance and odor-control objectives when
investigating force-main discharge points.
7. Which equation is commonly associated with calculating flow
in a partially full gravity sewer under open-channel conditions?
A. Boyle's law
B. Manning's equation
System Operator Class III — Form B
Exam Questions and Correct
Answers with Detailed Rationales |
2026/2027 Edition | Exam Prep
Study Guide PDF
1. In a wastewater collection system, what is the primary purpose
of maintaining adequate minimum velocity in a gravity sewer?
A. To increase pipe pressure
B. To prevent wastewater from becoming too diluted
C. To minimize deposition of solids and maintain self-cleansing
conditions
D. To eliminate the need for routine cleaning
Answer: C. To minimize deposition of solids and maintain self-
cleansing conditions
Rationale: Adequate velocity helps keep suspended solids
moving through the sewer rather than allowing them to settle and
accumulate. Excessive deposition can reduce hydraulic capacity,
promote odors, and eventually contribute to blockages.
Maintaining appropriate design and operational velocities is
therefore an important part of collection-system management.
,2. A collection-system operator observes repeated sanitary sewer
overflows during intense rainfall. Which condition should be
investigated first?
A. Low chlorine residual at the treatment plant
B. Infiltration and inflow entering the collection system
C. Excessive dissolved oxygen in the receiving stream
D. Low alkalinity in the wastewater
Answer: B. Infiltration and inflow entering the collection
system
Rationale: Rainfall-related sewer overflows commonly indicate
excessive infiltration and inflow (I/I). Inflow can enter through
improper connections, roof drains, storm drains, and other direct
pathways, while infiltration enters through defective joints, cracks,
and groundwater intrusion. Identifying and reducing excessive I/I
can substantially reduce wet-weather hydraulic loading.
3. Which condition is most likely to cause hydrogen sulfide
formation in a collection system?
A. Highly turbulent, well-oxygenated wastewater
B. Warm, stagnant wastewater containing biodegradable organic
matter
C. Very low organic loading
D. Continuous exposure of wastewater to sunlight
Answer: B. Warm, stagnant wastewater containing
biodegradable organic matter
Rationale: Hydrogen sulfide is commonly associated with
anaerobic conditions in wastewater containing organic matter.
Stagnant or slow-moving wastewater allows oxygen to become
,depleted, creating conditions favorable for sulfate-reducing
microorganisms. Warmer temperatures generally accelerate
biological activity and can intensify odor and corrosion problems.
4. What is the primary operational concern associated with
hydrogen sulfide in a wastewater collection system?
A. It increases dissolved oxygen
B. It can create toxic exposure hazards and contribute to
corrosion
C. It prevents biological activity
D. It permanently disinfects sewer surfaces
Answer: B. It can create toxic exposure hazards and contribute
to corrosion
Rationale: Hydrogen sulfide is toxic and can present a serious
occupational hazard, particularly in confined spaces. It also
contributes to sewer corrosion because hydrogen sulfide can be
biologically converted to sulfuric acid under appropriate
conditions. Operators should use proper atmospheric monitoring
and confined-space procedures whenever required.
5. Which sewer feature is specifically designed to provide access
for inspection, cleaning, maintenance, and changes in sewer
alignment or elevation?
A. Air-release valve
B. Manhole
C. Backflow preventer
D. Sampling tap
, Answer: B. Manhole
Rationale: Manholes provide access to gravity collection sewers
for inspection, cleaning, maintenance, and other operational
activities. They are commonly located at changes in direction,
grade, pipe size, and at selected intervals along a sewer.
6. A force main discharges into a receiving manhole and produces
excessive turbulence and odor. Which operational change may
help reduce the problem?
A. Increase the discharge velocity as much as possible
B. Evaluate the discharge configuration and minimize excessive
turbulence
C. Remove all downstream manholes
D. Reduce all gravity sewer slopes
Answer: B. Evaluate the discharge configuration and minimize
excessive turbulence
Rationale: Excessive turbulence can increase agitation, release
dissolved gases, and contribute to odor problems. The discharge
arrangement should be evaluated to provide appropriate energy
dissipation and hydraulic conditions. Operators should consider
both hydraulic performance and odor-control objectives when
investigating force-main discharge points.
7. Which equation is commonly associated with calculating flow
in a partially full gravity sewer under open-channel conditions?
A. Boyle's law
B. Manning's equation
