AR WWT Wastewater Treatment
Contractor Exam Questions and Correct
Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a municipal wastewater treatment
plant?
A. To increase the mineral content of drinking water
B. To remove pollutants from wastewater before discharge or reuse
C. To produce potable water without additional treatment
D. To eliminate the need for sewer collection systems
Correct Answer: B. To remove pollutants from wastewater before
discharge or reuse
Rationale: Wastewater treatment plants remove or reduce suspended
solids, organic matter, nutrients, pathogens, and other contaminants.
,Proper treatment protects public health and receiving waters while
allowing treated effluent to be safely discharged or reused when
applicable requirements are met.
2. Which wastewater characteristic is most directly associated with
the amount of biodegradable organic matter present?
A. Total dissolved solids (TDS)
B. Electrical conductivity
C. Biochemical oxygen demand (BOD)
D. Water hardness
Correct Answer: C. Biochemical oxygen demand (BOD)
Rationale: BOD measures the oxygen consumed by microorganisms as
they biologically break down biodegradable organic material under
specified test conditions. Elevated BOD in wastewater indicates a
greater potential to deplete dissolved oxygen in receiving waters if
the wastewater is discharged without adequate treatment.
3. What is the principal function of a bar screen at the headworks of a
wastewater treatment plant?
A. To remove large debris from incoming wastewater
B. To disinfect treated effluent
,C. To remove dissolved nitrates
D. To increase dissolved oxygen
Correct Answer: A. To remove large debris from incoming wastewater
Rationale: Bar screens intercept large materials such as rags, plastics,
sticks, and other debris. Removing these materials protects
downstream pumps, valves, pipes, and treatment equipment from
clogging or mechanical damage.
4. Which treatment process primarily removes settleable inorganic
materials such as sand and grit?
A. Chlorination
B. Activated sludge treatment
C. Biological nutrient removal
D. Grit removal
Correct Answer: D. Grit removal
Rationale: Grit chambers reduce the velocity or alter the flow pattern
of wastewater to allow dense inorganic particles, including sand and
gravel, to settle. Removing grit prevents excessive abrasion,
accumulation, and damage in pumps, tanks, and sludge-handling
equipment.
, 5. What is the main purpose of primary sedimentation?
A. To remove all dissolved organic compounds
B. To settle suspended solids and remove floating materials
C. To destroy all microorganisms
D. To convert ammonia completely into nitrogen gas
Correct Answer: B. To settle suspended solids and remove floating
materials
Rationale: Primary sedimentation allows heavier suspended solids to
settle as primary sludge while grease and other floatable materials
can be skimmed from the surface. This reduces the solids and organic
loading entering secondary biological treatment.
6. In an activated sludge system, what is the principal role of
aeration?
A. To increase wastewater salinity
B. To remove grit through sedimentation
C. To supply oxygen and support biological treatment
D. To sterilize wastewater completely
Correct Answer: C. To supply oxygen and support biological treatment
Contractor Exam Questions and Correct
Answers (Verified Answers) Plus Rationale
2027 Q&A| Instant Download Pdf
1. What is the primary purpose of a municipal wastewater treatment
plant?
A. To increase the mineral content of drinking water
B. To remove pollutants from wastewater before discharge or reuse
C. To produce potable water without additional treatment
D. To eliminate the need for sewer collection systems
Correct Answer: B. To remove pollutants from wastewater before
discharge or reuse
Rationale: Wastewater treatment plants remove or reduce suspended
solids, organic matter, nutrients, pathogens, and other contaminants.
,Proper treatment protects public health and receiving waters while
allowing treated effluent to be safely discharged or reused when
applicable requirements are met.
2. Which wastewater characteristic is most directly associated with
the amount of biodegradable organic matter present?
A. Total dissolved solids (TDS)
B. Electrical conductivity
C. Biochemical oxygen demand (BOD)
D. Water hardness
Correct Answer: C. Biochemical oxygen demand (BOD)
Rationale: BOD measures the oxygen consumed by microorganisms as
they biologically break down biodegradable organic material under
specified test conditions. Elevated BOD in wastewater indicates a
greater potential to deplete dissolved oxygen in receiving waters if
the wastewater is discharged without adequate treatment.
3. What is the principal function of a bar screen at the headworks of a
wastewater treatment plant?
A. To remove large debris from incoming wastewater
B. To disinfect treated effluent
,C. To remove dissolved nitrates
D. To increase dissolved oxygen
Correct Answer: A. To remove large debris from incoming wastewater
Rationale: Bar screens intercept large materials such as rags, plastics,
sticks, and other debris. Removing these materials protects
downstream pumps, valves, pipes, and treatment equipment from
clogging or mechanical damage.
4. Which treatment process primarily removes settleable inorganic
materials such as sand and grit?
A. Chlorination
B. Activated sludge treatment
C. Biological nutrient removal
D. Grit removal
Correct Answer: D. Grit removal
Rationale: Grit chambers reduce the velocity or alter the flow pattern
of wastewater to allow dense inorganic particles, including sand and
gravel, to settle. Removing grit prevents excessive abrasion,
accumulation, and damage in pumps, tanks, and sludge-handling
equipment.
, 5. What is the main purpose of primary sedimentation?
A. To remove all dissolved organic compounds
B. To settle suspended solids and remove floating materials
C. To destroy all microorganisms
D. To convert ammonia completely into nitrogen gas
Correct Answer: B. To settle suspended solids and remove floating
materials
Rationale: Primary sedimentation allows heavier suspended solids to
settle as primary sludge while grease and other floatable materials
can be skimmed from the surface. This reduces the solids and organic
loading entering secondary biological treatment.
6. In an activated sludge system, what is the principal role of
aeration?
A. To increase wastewater salinity
B. To remove grit through sedimentation
C. To supply oxygen and support biological treatment
D. To sterilize wastewater completely
Correct Answer: C. To supply oxygen and support biological treatment
