2026 IL Class B Water Operator Test UPDATED ACTUAL Questions and
CORRECT Answers
Question: Common Types Of Underdrain Systems are?
Correct Answer: Pipe Lateral Collectors Perforated Tile Bottoms Wheeler Filter Bottoms Porous Plate
Bottoms False Floor Underdrain Systems
Question: What filter sytems require a gravel support bed to prevent sand and anthracite from flowing into
the underdrains?
Correct Answer: Pipe Lateral Collectors Perforated Tile Bottoms Wheeler Filter Bottoms
Question: What is wash water through?
Correct Answer: A through placed above the filter media to collect the backwash water and carry it to the
drainage system.
Question: Air scouring works particulary well for what type of filter bed?
Correct Answer: Monomedium beds.
Question: Why is a rate of flow controller needed for backwashing?
Correct Answer: Without the controller flow surges could force suspended particles through the filter.
Question: Why are loss of head indicators used on filters?
Correct Answer: Are required to monitor the status of resistance to flow in the filter as susupened matter
builds up in the media.
Question: A sudden incrase in efflunet turbidity indicates what?
Correct Answer: Filter Breakthrough
Question: If filter run times between backwashes are long, for example one week, because high quality
(low turbidity) water is being applied to the filters, which problem could still arise? a. Mudball formation b.
Air binding and formation of mudballs c. Extended backwashing due to media becoming too compacted d.
Floc breakthrough
Correct Answer: Floc Breakthrough
Question: Gravel displacement in a filter bed from backwash rates with too high of a velocity could
eventually cause a. compaction of the filter media. b. loss of media into the backwash troughs. c. a sand
boil. d. bed shrinkage.
Correct Answer: C. A sand Boil
Question: Which conventional treatment step is eliminated by direct filtration.
Correct Answer: Sedimentation
Question: Which of the following is the layer of solids and biological growth that forms on the top of a
slow sand filter?
Correct Answer: Schmutzdecke
Question: Filter tanks are generlly made?
Correct Answer: Rectangular and constructed of concrete
, Question: In a typical air scour sequence, air is applied______backwash water is introduced?
Correct Answer: Before
Question: What is the filtration flow rate through a high rate mixed media filter?
Correct Answer: 3-8 gpm/ft2
Question: Which system is the first and oldest type of underdrain system, having a central mainfold pipe
with perforated lateral pipe on each side?
Correct Answer: Pipe lateral Collectors
Question: Which regulation requires that all filters in a surface water treatment plant have online
turbidmeters, and that they monitor the filter while in operation?-
Correct Answer: IESWTR
Question: Prehistoric deposits of the skeletal remains of microscopic aquatic plants are the source of what
useful filtering element?
Correct Answer: Diatomaceous Earth (DE)
Question: What is sand boil?
Correct Answer: The violent washing action in a filter caused by uneven distribution of backwash water.
Question: What is air binding?
Correct Answer: A condition that occurs in filters when air comes out of solution as a result of pressure
decreases and temperature increases. The air clogs the voids between the media grains, which causes
increased head loss through the filter and shorter runs. (Not a issue in pressure filters)
Question: What is a polymer?
Correct Answer: High-molecular weight, sythetic organic compound that is used to aid in the coagulation
and flocculation process.
Question: What is Floc?
Correct Answer: Collections of smaller particles (Such as silt, organic matter and microorganisms) that
have come together (agglomerated) into larger, more settable partivcles as a result of the
coagulation-flocculation process.
Question: What is unique about the wheeler filter bottom?
Correct Answer: A pateneted filter underdrain system using small porcelain spheres of various sizes in
conical depressions.
Question: The advantage to using the oxidant ozone is that it?
Correct Answer: Has little PH effect.
Question: Pretreament with chlorine is being elimnated at many water treatment plants because it has been
shown to?
Correct Answer: Sometimes produce disinfection by products known to be carcinogenic.
Question: C x T values are based on?
Correct Answer: Concentration of chlorine, contact time, PH, and temperature.
CORRECT Answers
Question: Common Types Of Underdrain Systems are?
Correct Answer: Pipe Lateral Collectors Perforated Tile Bottoms Wheeler Filter Bottoms Porous Plate
Bottoms False Floor Underdrain Systems
Question: What filter sytems require a gravel support bed to prevent sand and anthracite from flowing into
the underdrains?
Correct Answer: Pipe Lateral Collectors Perforated Tile Bottoms Wheeler Filter Bottoms
Question: What is wash water through?
Correct Answer: A through placed above the filter media to collect the backwash water and carry it to the
drainage system.
Question: Air scouring works particulary well for what type of filter bed?
Correct Answer: Monomedium beds.
Question: Why is a rate of flow controller needed for backwashing?
Correct Answer: Without the controller flow surges could force suspended particles through the filter.
Question: Why are loss of head indicators used on filters?
Correct Answer: Are required to monitor the status of resistance to flow in the filter as susupened matter
builds up in the media.
Question: A sudden incrase in efflunet turbidity indicates what?
Correct Answer: Filter Breakthrough
Question: If filter run times between backwashes are long, for example one week, because high quality
(low turbidity) water is being applied to the filters, which problem could still arise? a. Mudball formation b.
Air binding and formation of mudballs c. Extended backwashing due to media becoming too compacted d.
Floc breakthrough
Correct Answer: Floc Breakthrough
Question: Gravel displacement in a filter bed from backwash rates with too high of a velocity could
eventually cause a. compaction of the filter media. b. loss of media into the backwash troughs. c. a sand
boil. d. bed shrinkage.
Correct Answer: C. A sand Boil
Question: Which conventional treatment step is eliminated by direct filtration.
Correct Answer: Sedimentation
Question: Which of the following is the layer of solids and biological growth that forms on the top of a
slow sand filter?
Correct Answer: Schmutzdecke
Question: Filter tanks are generlly made?
Correct Answer: Rectangular and constructed of concrete
, Question: In a typical air scour sequence, air is applied______backwash water is introduced?
Correct Answer: Before
Question: What is the filtration flow rate through a high rate mixed media filter?
Correct Answer: 3-8 gpm/ft2
Question: Which system is the first and oldest type of underdrain system, having a central mainfold pipe
with perforated lateral pipe on each side?
Correct Answer: Pipe lateral Collectors
Question: Which regulation requires that all filters in a surface water treatment plant have online
turbidmeters, and that they monitor the filter while in operation?-
Correct Answer: IESWTR
Question: Prehistoric deposits of the skeletal remains of microscopic aquatic plants are the source of what
useful filtering element?
Correct Answer: Diatomaceous Earth (DE)
Question: What is sand boil?
Correct Answer: The violent washing action in a filter caused by uneven distribution of backwash water.
Question: What is air binding?
Correct Answer: A condition that occurs in filters when air comes out of solution as a result of pressure
decreases and temperature increases. The air clogs the voids between the media grains, which causes
increased head loss through the filter and shorter runs. (Not a issue in pressure filters)
Question: What is a polymer?
Correct Answer: High-molecular weight, sythetic organic compound that is used to aid in the coagulation
and flocculation process.
Question: What is Floc?
Correct Answer: Collections of smaller particles (Such as silt, organic matter and microorganisms) that
have come together (agglomerated) into larger, more settable partivcles as a result of the
coagulation-flocculation process.
Question: What is unique about the wheeler filter bottom?
Correct Answer: A pateneted filter underdrain system using small porcelain spheres of various sizes in
conical depressions.
Question: The advantage to using the oxidant ozone is that it?
Correct Answer: Has little PH effect.
Question: Pretreament with chlorine is being elimnated at many water treatment plants because it has been
shown to?
Correct Answer: Sometimes produce disinfection by products known to be carcinogenic.
Question: C x T values are based on?
Correct Answer: Concentration of chlorine, contact time, PH, and temperature.
