WASTEWATER OPERATOR LATEST 2026 EXAM QUESTIONS
AND ANSWERS RATED A+
✔✔Wastewater sources & characteristics:
High suspended solids and BOD are most probably associated with which type of
organisms? - ✔✔flagellates
✔✔Wastewater sources & characteristics:
What organism would most likely enhance the penetration of oxygen into the activated
sludge - ✔✔rotifers
✔✔Rocks/Screens/Comminutors & Grit Removal:
Chlorine gas has a specific gravity of - ✔✔2.5 specific gravity
✔✔Rocks/Screens/Comminutors & Grit Removal:
Proper flow velocity through a grit channel is indicated when the grit being removed
contains
a. no organics
b. a little organic material
c. about half the volume as the grit being removed
d. about the same volume as the grit being removed - ✔✔a little organic material
✔✔Sedimentation and Flotation:
Surface loading and detention time is a clarifier are directly related to: - ✔✔flow through
a clarifier
✔✔Sedimentation and Flotation:
What is the expected range for the removal of settleable solids from a primary clarifier?
- ✔✔95-99%
✔✔Sedimentation and Flotation:
What condition will occur if sludge is not pumped out of primary clarifiers at regular
intervals? - ✔✔clarifier will become septic
✔✔Sedimentation and Flotation:
,Secondary clarifiers are usually located after:
a. primary clarifier
b. an anaerobic digester
c. a biological process
d. preaeration - ✔✔a biological process
✔✔Sedimentation and Flotation:
Filter sloughings are a product of: - ✔✔biological action
✔✔Sedimentation and Flotation:
when one liquid is dissolved in another liquid it is called - ✔✔an emulsion
✔✔Sedimentation and Flotation:
What is the optimum temperature for digester substances? - ✔✔90 degrees F
✔✔Secondary Treatment:
Which one of the following types of wastewater ponds listed below is not classified like
the other three?
a. polishing pond
2. oxidation pond
c. aerobic pond
d. raw sewage - ✔✔aerobic pond
✔✔Secondary Treatment:
What type of pond would receive wastewater form a secondary treatment system? -
✔✔polishing pond
✔✔Secondary Treatment:
The color of the bio-film on a rotating biological contactor undergoing nitrification would
appear? - ✔✔reddish brown to golden
✔✔Secondary Treatment:
The color of the bio-film on a rotating biological contactor that has high sulfur
concentrations would appear - ✔✔chalky white
✔✔Secondary Treatment:
, Rotating biological contactors have all the following advantages except:
a. high sludge production
b. they can handle a large range of flows
c. power requirements are low
d. low operating costs, as they are east to run - ✔✔high sludge production
✔✔Secondary Treatment:
A wastewater [plant has a train of three rotating biological contactor (RBC) units. The
color of the first RBC is___; the color of the second RBC is_____; and the color of the
third RBS C is____ - ✔✔(1) gray
(2) reddish brown
(3) reddish brown
✔✔Activated Sludge:
Following the activated sludge what process modification is very sensitive to bulking?
a. conventional modification
b. extended aeration activate sludge
c. complex mix aeration
d. pure oxygen - ✔✔conventional modification
✔✔Activated Sludge:
What modified activated sludge process does not require primary treatment?
a.complete mix aeration
b. contact stabilization
c. tapered aeration
d. step aeration - ✔✔contact stabilization
✔✔Activated Sludge:
Primary treatment is not required in which modified activated sludge process?
a. step aeration
b. complete mix aeration
c. tapered aeration
d. extended aeration activated sludge - ✔✔extended aeration activation sludge
✔✔Activated Sludge:
Mixed liquor is a combination of what 3 things? - ✔✔activated sludge in an aeration tank
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AND ANSWERS RATED A+
✔✔Wastewater sources & characteristics:
High suspended solids and BOD are most probably associated with which type of
organisms? - ✔✔flagellates
✔✔Wastewater sources & characteristics:
What organism would most likely enhance the penetration of oxygen into the activated
sludge - ✔✔rotifers
✔✔Rocks/Screens/Comminutors & Grit Removal:
Chlorine gas has a specific gravity of - ✔✔2.5 specific gravity
✔✔Rocks/Screens/Comminutors & Grit Removal:
Proper flow velocity through a grit channel is indicated when the grit being removed
contains
a. no organics
b. a little organic material
c. about half the volume as the grit being removed
d. about the same volume as the grit being removed - ✔✔a little organic material
✔✔Sedimentation and Flotation:
Surface loading and detention time is a clarifier are directly related to: - ✔✔flow through
a clarifier
✔✔Sedimentation and Flotation:
What is the expected range for the removal of settleable solids from a primary clarifier?
- ✔✔95-99%
✔✔Sedimentation and Flotation:
What condition will occur if sludge is not pumped out of primary clarifiers at regular
intervals? - ✔✔clarifier will become septic
✔✔Sedimentation and Flotation:
,Secondary clarifiers are usually located after:
a. primary clarifier
b. an anaerobic digester
c. a biological process
d. preaeration - ✔✔a biological process
✔✔Sedimentation and Flotation:
Filter sloughings are a product of: - ✔✔biological action
✔✔Sedimentation and Flotation:
when one liquid is dissolved in another liquid it is called - ✔✔an emulsion
✔✔Sedimentation and Flotation:
What is the optimum temperature for digester substances? - ✔✔90 degrees F
✔✔Secondary Treatment:
Which one of the following types of wastewater ponds listed below is not classified like
the other three?
a. polishing pond
2. oxidation pond
c. aerobic pond
d. raw sewage - ✔✔aerobic pond
✔✔Secondary Treatment:
What type of pond would receive wastewater form a secondary treatment system? -
✔✔polishing pond
✔✔Secondary Treatment:
The color of the bio-film on a rotating biological contactor undergoing nitrification would
appear? - ✔✔reddish brown to golden
✔✔Secondary Treatment:
The color of the bio-film on a rotating biological contactor that has high sulfur
concentrations would appear - ✔✔chalky white
✔✔Secondary Treatment:
, Rotating biological contactors have all the following advantages except:
a. high sludge production
b. they can handle a large range of flows
c. power requirements are low
d. low operating costs, as they are east to run - ✔✔high sludge production
✔✔Secondary Treatment:
A wastewater [plant has a train of three rotating biological contactor (RBC) units. The
color of the first RBC is___; the color of the second RBC is_____; and the color of the
third RBS C is____ - ✔✔(1) gray
(2) reddish brown
(3) reddish brown
✔✔Activated Sludge:
Following the activated sludge what process modification is very sensitive to bulking?
a. conventional modification
b. extended aeration activate sludge
c. complex mix aeration
d. pure oxygen - ✔✔conventional modification
✔✔Activated Sludge:
What modified activated sludge process does not require primary treatment?
a.complete mix aeration
b. contact stabilization
c. tapered aeration
d. step aeration - ✔✔contact stabilization
✔✔Activated Sludge:
Primary treatment is not required in which modified activated sludge process?
a. step aeration
b. complete mix aeration
c. tapered aeration
d. extended aeration activated sludge - ✔✔extended aeration activation sludge
✔✔Activated Sludge:
Mixed liquor is a combination of what 3 things? - ✔✔activated sludge in an aeration tank
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