AK Wastewater Treatment Contractor Exam
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
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1. What is the primary purpose of screening at the headworks of a
wastewater treatment facility?
a. Remove dissolved nutrients
b. Increase dissolved oxygen
c. Remove large debris and solids
d. Disinfect the wastewater
Rationale: Screening removes rags, sticks, plastics, and other large
debris that could damage pumps, clog pipes, or interfere with
downstream treatment equipment.
2. Which treatment process is primarily responsible for removing
settleable suspended solids?
,a. Chlorination
b. Aeration
c. Filtration
d. Primary sedimentation
Rationale: Primary sedimentation uses gravity to allow heavier
suspended and settleable solids to settle to the bottom of a clarifier,
while floatable materials can be removed from the surface.
3. What does BOD stand for?
a. Biological Oxygen Density
b. Biochemical Oxygen Demand
c. Biological Oxidation Distribution
d. Biochemical Organic Dissolution
Rationale: Biochemical Oxygen Demand (BOD) measures the amount
of dissolved oxygen microorganisms require to biologically decompose
biodegradable organic matter in wastewater.
4. A high BOD concentration in untreated wastewater generally
indicates:
a. Low organic loading
b. Excessive chlorine
,c. A high concentration of biodegradable organic matter
d. Very low microbial activity
Rationale: BOD increases when wastewater contains more
biodegradable organic material because microorganisms require more
oxygen to break that material down.
5. What is the main function of an aeration basin in an activated
sludge system?
a. Remove grit by gravity
b. Store sludge permanently
c. Provide oxygen and mixing for biological treatment
d. Disinfect final effluent
Rationale: Aeration basins supply oxygen and maintain mixing so
microorganisms can consume biodegradable organic matter and carry
out other biological treatment processes.
6. Which microorganism group is primarily responsible for
nitrification?
a. Protozoa
b. Algae
c. Nitrifying bacteria
d. Viruses
, Rationale: Nitrifying bacteria convert ammonia first to nitrite and
then to nitrate under suitable aerobic conditions.
7. What is the purpose of return activated sludge (RAS)?
a. Return screenings to the headworks
b. Return settled biological solids to the aeration process
c. Return disinfected water to the influent
d. Return grit to the primary clarifier
Rationale: RAS recycles microorganisms from the secondary clarifier
back to the aeration basin, maintaining an appropriate biological
solids concentration.
8. What is waste activated sludge (WAS)?
a. Sludge removed from a drinking-water filter
b. Primary sludge that has been disinfected
c. Excess biological solids removed from the activated sludge process
d. Sand removed from a grit chamber
Rationale: WAS is periodically removed from the biological process to
control the amount and age of microorganisms in the activated sludge
system.
9. What is the primary purpose of a secondary clarifier?
Questions and Correct Answers (Verified
Answers) Plus Rationale 2027 Q&A| Instant
Download Pdf
1. What is the primary purpose of screening at the headworks of a
wastewater treatment facility?
a. Remove dissolved nutrients
b. Increase dissolved oxygen
c. Remove large debris and solids
d. Disinfect the wastewater
Rationale: Screening removes rags, sticks, plastics, and other large
debris that could damage pumps, clog pipes, or interfere with
downstream treatment equipment.
2. Which treatment process is primarily responsible for removing
settleable suspended solids?
,a. Chlorination
b. Aeration
c. Filtration
d. Primary sedimentation
Rationale: Primary sedimentation uses gravity to allow heavier
suspended and settleable solids to settle to the bottom of a clarifier,
while floatable materials can be removed from the surface.
3. What does BOD stand for?
a. Biological Oxygen Density
b. Biochemical Oxygen Demand
c. Biological Oxidation Distribution
d. Biochemical Organic Dissolution
Rationale: Biochemical Oxygen Demand (BOD) measures the amount
of dissolved oxygen microorganisms require to biologically decompose
biodegradable organic matter in wastewater.
4. A high BOD concentration in untreated wastewater generally
indicates:
a. Low organic loading
b. Excessive chlorine
,c. A high concentration of biodegradable organic matter
d. Very low microbial activity
Rationale: BOD increases when wastewater contains more
biodegradable organic material because microorganisms require more
oxygen to break that material down.
5. What is the main function of an aeration basin in an activated
sludge system?
a. Remove grit by gravity
b. Store sludge permanently
c. Provide oxygen and mixing for biological treatment
d. Disinfect final effluent
Rationale: Aeration basins supply oxygen and maintain mixing so
microorganisms can consume biodegradable organic matter and carry
out other biological treatment processes.
6. Which microorganism group is primarily responsible for
nitrification?
a. Protozoa
b. Algae
c. Nitrifying bacteria
d. Viruses
, Rationale: Nitrifying bacteria convert ammonia first to nitrite and
then to nitrate under suitable aerobic conditions.
7. What is the purpose of return activated sludge (RAS)?
a. Return screenings to the headworks
b. Return settled biological solids to the aeration process
c. Return disinfected water to the influent
d. Return grit to the primary clarifier
Rationale: RAS recycles microorganisms from the secondary clarifier
back to the aeration basin, maintaining an appropriate biological
solids concentration.
8. What is waste activated sludge (WAS)?
a. Sludge removed from a drinking-water filter
b. Primary sludge that has been disinfected
c. Excess biological solids removed from the activated sludge process
d. Sand removed from a grit chamber
Rationale: WAS is periodically removed from the biological process to
control the amount and age of microorganisms in the activated sludge
system.
9. What is the primary purpose of a secondary clarifier?
