Arkansas AR-WWT Wastewater
Treatment Contractor Practice
Exam | Questions, Verified
Answers & Detailed Rationales |
Complete Contractor License
Exam Prep Study Guide |
Updated 2026
1. What is the primary purpose of preliminary
wastewater treatment?
A. Remove dissolved nutrients
B. Remove large debris, rags, grit, and other materials
that can damage downstream equipment
C. Disinfect the final effluent
D. Remove all dissolved organic matter
Answer: Remove large debris, rags, grit, and other
materials that can damage downstream equipment
Rationale: Preliminary treatment protects pumps, pipes,
clarifiers, and other equipment by removing screenings,
grit, and similar materials before subsequent treatment
processes.
2. What is the main function of a bar screen at a
wastewater treatment plant?
A. Remove dissolved ammonia
B. Increase dissolved oxygen
C. Remove large floating and suspended debris
D. Remove phosphorus chemically
Answer: Remove large floating and suspended debris
,Rationale: Bar screens intercept rags, plastics, sticks,
and other large solids that could clog or damage
downstream equipment.
3. What is the primary purpose of a grit chamber?
A. Remove bacteria
B. Increase sludge concentration
C. Remove heavy inorganic particles such as sand and
gravel
D. Remove dissolved oxygen
Answer: Remove heavy inorganic particles such as sand
and gravel
Rationale: Grit removal protects pumps and mechanical
equipment and prevents abrasive materials from
accumulating in tanks and pipelines.
4. Which material is most likely classified as grit?
A. Activated sludge floc
B. Bacteria
C. Sand
D. Dissolved organic matter
Answer: Sand
Rationale: Grit consists primarily of dense inorganic
particles such as sand, gravel, eggshells, and similar
materials.
5. What is the primary objective of primary clarification?
A. Disinfect wastewater
B. Settle suspended solids and remove floatable
materials
C. Completely remove nitrogen
D. Add oxygen to wastewater
,Answer: Settle suspended solids and remove floatable
materials
Rationale: Primary clarifiers use gravity to remove
settleable solids and floating scum before biological
treatment.
6. What does BOD measure?
A. Amount of grit in wastewater
B. Amount of chlorine required for disinfection
C. Oxygen demand associated with biodegradable
organic matter
D. Total amount of inorganic solids
Answer: Oxygen demand associated with biodegradable
organic matter
Rationale: Biochemical oxygen demand indicates the
amount of oxygen microorganisms require to
biologically stabilize biodegradable organic material.
7. What does TSS stand for?
A. Total Soluble Salts
B. Treatment System Standard
C. Total Suspended Solids
D. Total Sewer Slope
Answer: Total Suspended Solids
Rationale: TSS represents particulate material
suspended in wastewater that can be measured by
filtering and weighing the retained solids.
8. Which process normally uses microorganisms to
remove dissolved and colloidal organic matter?
, A. Screening
B. Grit removal
C. Secondary biological treatment
D. Barometric treatment
Answer: Secondary biological treatment
Rationale: Biological treatment relies on
microorganisms to consume and transform
biodegradable organic material.
9. What is the purpose of aeration in an activated-
sludge process?
A. Remove grit
B. Supply oxygen and maintain biological activity
C. Increase chlorine concentration
D. Remove screenings
Answer: Supply oxygen and maintain biological activity
Rationale: Aeration supplies oxygen needed by aerobic
microorganisms and helps keep biological solids
suspended and mixed.
10. What is a clarifier's primary function in an activated-
sludge system?
A. Generate chlorine
B. Separate biological solids from treated wastewater
C. Grind screenings
D. Increase influent flow
Answer: Separate biological solids from treated
wastewater
Rationale: Secondary clarifiers allow biological floc to
settle so clarified effluent can leave the process while
sludge can be returned or wasted.
Treatment Contractor Practice
Exam | Questions, Verified
Answers & Detailed Rationales |
Complete Contractor License
Exam Prep Study Guide |
Updated 2026
1. What is the primary purpose of preliminary
wastewater treatment?
A. Remove dissolved nutrients
B. Remove large debris, rags, grit, and other materials
that can damage downstream equipment
C. Disinfect the final effluent
D. Remove all dissolved organic matter
Answer: Remove large debris, rags, grit, and other
materials that can damage downstream equipment
Rationale: Preliminary treatment protects pumps, pipes,
clarifiers, and other equipment by removing screenings,
grit, and similar materials before subsequent treatment
processes.
2. What is the main function of a bar screen at a
wastewater treatment plant?
A. Remove dissolved ammonia
B. Increase dissolved oxygen
C. Remove large floating and suspended debris
D. Remove phosphorus chemically
Answer: Remove large floating and suspended debris
,Rationale: Bar screens intercept rags, plastics, sticks,
and other large solids that could clog or damage
downstream equipment.
3. What is the primary purpose of a grit chamber?
A. Remove bacteria
B. Increase sludge concentration
C. Remove heavy inorganic particles such as sand and
gravel
D. Remove dissolved oxygen
Answer: Remove heavy inorganic particles such as sand
and gravel
Rationale: Grit removal protects pumps and mechanical
equipment and prevents abrasive materials from
accumulating in tanks and pipelines.
4. Which material is most likely classified as grit?
A. Activated sludge floc
B. Bacteria
C. Sand
D. Dissolved organic matter
Answer: Sand
Rationale: Grit consists primarily of dense inorganic
particles such as sand, gravel, eggshells, and similar
materials.
5. What is the primary objective of primary clarification?
A. Disinfect wastewater
B. Settle suspended solids and remove floatable
materials
C. Completely remove nitrogen
D. Add oxygen to wastewater
,Answer: Settle suspended solids and remove floatable
materials
Rationale: Primary clarifiers use gravity to remove
settleable solids and floating scum before biological
treatment.
6. What does BOD measure?
A. Amount of grit in wastewater
B. Amount of chlorine required for disinfection
C. Oxygen demand associated with biodegradable
organic matter
D. Total amount of inorganic solids
Answer: Oxygen demand associated with biodegradable
organic matter
Rationale: Biochemical oxygen demand indicates the
amount of oxygen microorganisms require to
biologically stabilize biodegradable organic material.
7. What does TSS stand for?
A. Total Soluble Salts
B. Treatment System Standard
C. Total Suspended Solids
D. Total Sewer Slope
Answer: Total Suspended Solids
Rationale: TSS represents particulate material
suspended in wastewater that can be measured by
filtering and weighing the retained solids.
8. Which process normally uses microorganisms to
remove dissolved and colloidal organic matter?
, A. Screening
B. Grit removal
C. Secondary biological treatment
D. Barometric treatment
Answer: Secondary biological treatment
Rationale: Biological treatment relies on
microorganisms to consume and transform
biodegradable organic material.
9. What is the purpose of aeration in an activated-
sludge process?
A. Remove grit
B. Supply oxygen and maintain biological activity
C. Increase chlorine concentration
D. Remove screenings
Answer: Supply oxygen and maintain biological activity
Rationale: Aeration supplies oxygen needed by aerobic
microorganisms and helps keep biological solids
suspended and mixed.
10. What is a clarifier's primary function in an activated-
sludge system?
A. Generate chlorine
B. Separate biological solids from treated wastewater
C. Grind screenings
D. Increase influent flow
Answer: Separate biological solids from treated
wastewater
Rationale: Secondary clarifiers allow biological floc to
settle so clarified effluent can leave the process while
sludge can be returned or wasted.
