TEXAS WASTEWATER EXAMINATION
VERSIONS A AND B Actual Exam
2026/2027 Complete Questions and
Verified Answers Graded A Pass
Guaranteed - A+ Graded
Q1. In wastewater treatment, the primary purpose of a bar screen is to
remove:
• A) Dissolved solids
• B) Large debris and rags
• C) Nutrients
• D) Bacteria
Correct ,,,,answer,,,: B) Large debris and rags. Bar screens are preliminary
treatment devices designed to remove large solids such as sticks, rags, and
plastics that could damage pumps or clog downstream equipment.
Q2. The unit process that removes settleable solids from wastewater by
gravity is:
• A) Primary clarification
• B) Chlorination
• C) Aeration
• D) Filtration
,Correct ,,,,answer,,,: A) Primary clarification. Primary clarifiers (sedimentation
tanks) allow heavy solids to settle by gravity while lighter materials float to
the surface, typically removing 50-70% of suspended solids.
Q3. The purpose of grit chambers is to remove:
• A) Oils and grease
• B) Sand and heavy particles
• C) Dissolved oxygen
• D) Bacteria
Correct ,,,,answer,,,: B) Sand and heavy particles. Grit chambers remove heavy
inorganic materials such as sand, gravel, and coffee grounds, which could
cause abrasion to pumps and accumulate in pipes.
Q4. What does the term "influent" refer to?
• A) Treated wastewater leaving the plant
• B) Wastewater entering the plant
• C) Sludge removed from clarifiers
• D) Recycled water
Correct ,,,,answer,,,: B) Wastewater entering the plant. Influent is the incoming
untreated wastewater that arrives at the treatment facility via the collection
system.
Q5. Screenings from a treatment plant should be:
• A) Returned to the headworks
• B) Buried in a permitted sanitary landfill
• C) Discharged into the receiving stream
• D) Used as agricultural fertilizer
Correct ,,,,answer,,,: B) Buried in a permitted sanitary landfill. Screenings are
considered solid waste and must be properly disposed of at a permitted
landfill to prevent public health hazards.
,Q6. The process of "pre-aeration" is used in preliminary treatment primarily
to:
• A) Disinfect the wastewater
• B) Remove odors and aid in grease separation
• C) Increase BOD concentration
• D) Decrease flow velocity
Correct ,,,,answer,,,: B) Remove odors and aid in grease separation. Pre-
aeration adds air to the wastewater early in the treatment process to freshen
septic wastes, float grease to the surface for removal, and provide some initial
BOD reduction.
Q7. In a primary clarifier, the weir overflow rate is calculated to ensure:
• A) Maximum sludge withdrawal
• B) Uniform flow distribution and prevent solids carryover
• C) High velocity for scum removal
• D) Anaerobic conditions in the tank
Correct ,,,,answer,,,: B) Uniform flow distribution and prevent solids
carryover. Weir overflow rate controls the amount of water flowing over the
effluent weir per foot of weir length; a low rate prevents short-circuiting and
carries over fine solids.
Q8. The "detention time" in a primary clarifier is the:
• A) Time required to pump sludge from the tank
• B) Theoretical time water remains in the tank
• C) Time between maintenance cleaning cycles
• D) Period of aeration needed before settling
Correct ,,,,answer,,,: B) Theoretical time water remains in the tank. Detention
time is calculated by dividing the tank volume by the flow rate. It indicates
how long the water is held, allowing solids to settle by gravity.
, Q9. What is the typical BOD removal efficiency of a well-functioning primary
clarifier?
• A) 30-40%
• B) 50-60%
• C) 70-80%
• D) 85-95%
Correct ,,,,answer,,,: A) 30-40%. Primary clarifiers rely on physical settling to
remove settleable solids; they typically remove 30-40% of BOD and 50-70%
of TSS.
Q10. Floating scum and grease are removed from the primary clarifier by:
• A) Bottom sludge withdrawal pipes
• B) Surface skimming mechanisms
• C) Submerged effluent weirs
• D) Diffused aeration systems
Correct ,,,,answer,,,: B) Surface skimming mechanisms. Rotating skimmer arms
or flights push floating scum, grease, and other light materials toward a
collection trough for removal and separate treatment.
Q11. At what approximate depth do primary clarifiers typically operate?
• A) 2-5 ft
• B) 10-15 ft
• C) 25-30 ft
• D) 50-60 ft
Correct ,,,,answer,,,: B) 10-15 ft. Primary clarifiers are designed with sidewater
depths ranging from 10 to 15 feet to provide adequate quiescent conditions
for settling solids and allowing clear effluent to flow over the weirs.
Q12. The mechanism of "flocculation" in a primary clarifier:
VERSIONS A AND B Actual Exam
2026/2027 Complete Questions and
Verified Answers Graded A Pass
Guaranteed - A+ Graded
Q1. In wastewater treatment, the primary purpose of a bar screen is to
remove:
• A) Dissolved solids
• B) Large debris and rags
• C) Nutrients
• D) Bacteria
Correct ,,,,answer,,,: B) Large debris and rags. Bar screens are preliminary
treatment devices designed to remove large solids such as sticks, rags, and
plastics that could damage pumps or clog downstream equipment.
Q2. The unit process that removes settleable solids from wastewater by
gravity is:
• A) Primary clarification
• B) Chlorination
• C) Aeration
• D) Filtration
,Correct ,,,,answer,,,: A) Primary clarification. Primary clarifiers (sedimentation
tanks) allow heavy solids to settle by gravity while lighter materials float to
the surface, typically removing 50-70% of suspended solids.
Q3. The purpose of grit chambers is to remove:
• A) Oils and grease
• B) Sand and heavy particles
• C) Dissolved oxygen
• D) Bacteria
Correct ,,,,answer,,,: B) Sand and heavy particles. Grit chambers remove heavy
inorganic materials such as sand, gravel, and coffee grounds, which could
cause abrasion to pumps and accumulate in pipes.
Q4. What does the term "influent" refer to?
• A) Treated wastewater leaving the plant
• B) Wastewater entering the plant
• C) Sludge removed from clarifiers
• D) Recycled water
Correct ,,,,answer,,,: B) Wastewater entering the plant. Influent is the incoming
untreated wastewater that arrives at the treatment facility via the collection
system.
Q5. Screenings from a treatment plant should be:
• A) Returned to the headworks
• B) Buried in a permitted sanitary landfill
• C) Discharged into the receiving stream
• D) Used as agricultural fertilizer
Correct ,,,,answer,,,: B) Buried in a permitted sanitary landfill. Screenings are
considered solid waste and must be properly disposed of at a permitted
landfill to prevent public health hazards.
,Q6. The process of "pre-aeration" is used in preliminary treatment primarily
to:
• A) Disinfect the wastewater
• B) Remove odors and aid in grease separation
• C) Increase BOD concentration
• D) Decrease flow velocity
Correct ,,,,answer,,,: B) Remove odors and aid in grease separation. Pre-
aeration adds air to the wastewater early in the treatment process to freshen
septic wastes, float grease to the surface for removal, and provide some initial
BOD reduction.
Q7. In a primary clarifier, the weir overflow rate is calculated to ensure:
• A) Maximum sludge withdrawal
• B) Uniform flow distribution and prevent solids carryover
• C) High velocity for scum removal
• D) Anaerobic conditions in the tank
Correct ,,,,answer,,,: B) Uniform flow distribution and prevent solids
carryover. Weir overflow rate controls the amount of water flowing over the
effluent weir per foot of weir length; a low rate prevents short-circuiting and
carries over fine solids.
Q8. The "detention time" in a primary clarifier is the:
• A) Time required to pump sludge from the tank
• B) Theoretical time water remains in the tank
• C) Time between maintenance cleaning cycles
• D) Period of aeration needed before settling
Correct ,,,,answer,,,: B) Theoretical time water remains in the tank. Detention
time is calculated by dividing the tank volume by the flow rate. It indicates
how long the water is held, allowing solids to settle by gravity.
, Q9. What is the typical BOD removal efficiency of a well-functioning primary
clarifier?
• A) 30-40%
• B) 50-60%
• C) 70-80%
• D) 85-95%
Correct ,,,,answer,,,: A) 30-40%. Primary clarifiers rely on physical settling to
remove settleable solids; they typically remove 30-40% of BOD and 50-70%
of TSS.
Q10. Floating scum and grease are removed from the primary clarifier by:
• A) Bottom sludge withdrawal pipes
• B) Surface skimming mechanisms
• C) Submerged effluent weirs
• D) Diffused aeration systems
Correct ,,,,answer,,,: B) Surface skimming mechanisms. Rotating skimmer arms
or flights push floating scum, grease, and other light materials toward a
collection trough for removal and separate treatment.
Q11. At what approximate depth do primary clarifiers typically operate?
• A) 2-5 ft
• B) 10-15 ft
• C) 25-30 ft
• D) 50-60 ft
Correct ,,,,answer,,,: B) 10-15 ft. Primary clarifiers are designed with sidewater
depths ranging from 10 to 15 feet to provide adequate quiescent conditions
for settling solids and allowing clear effluent to flow over the weirs.
Q12. The mechanism of "flocculation" in a primary clarifier:
