Operation of Wastewater Treatment Plants
(Levels 1-2 Exam Prep) Latest Update 2025-2026
125 Questions and 100% Verified Correct
Answers Guaranteed A+
______ is the anoxic biological reduction of nitrate nitrogen to nitrogen gas. -
CORRECT ANSWER: Denitrification is the anoxic biological reduction of nitrate nitrogen
to nitrogen gas. In secondary clarifiers the nitrogen bubbles produced as a result of
denitrification can attach to the biological floc and float the floc to the surface. This
condition is often the cause of rising sludge.
(Operation of Wastewater Treatment Plants, Volume 1, section 7.0
by Kenneth D. Kerri)
_______ is an aerobic process in which bacteria change the ammonia and organic
nitrogen in wastewater into oxidized nitrogen (usually nitrate). The second-stage BOD is
sometimes referred to as the "nitrogenous BOD" (first-stage BOD is called the
"carbonaceous BOD"). - CORRECT ANSWER: Nitrification is an aerobic process in
which bacteria change the ammonia and organic nitrogen in wastewater into oxidized
nitrogen (usually nitrate). The second-stage BOD is sometimes referred to as the
"nitrogenous BOD" (first-stage BOD is called the "carbonaceous BOD").
(Operation of Wastewater Treatment Plants, Volume 1, section 7.0
by Kenneth D. Kerri)
A _____ flume is widely used for measuring wastewater flow. - CORRECT ANSWER:
Parshall
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
,A minimum dissolved oxygen (D.O.) level of _____ mg/L is recommended in the
aeration tank for most basic types of activated sludge processes. - CORRECT
ANSWER: A minimum dissolved oxygen (D.O.) level of 1.0 mg/L is recommended in the
aeration tank for most basic types of activated sludge processes. Maintaining > 1.0
mg/L of D.O. contributes to establishing a favorable environment for the organisms,
which produces the desired type of organism and the desired level of activity.
(New Mexico Wastewater Systems Operator Certification Study Manual)
A three phase pump motor is rotating the wrong direction after repairing and replacing it.
What is a likely solution to this problem? - CORRECT ANSWER: Switch any two of the
three electrical leads to the motor.
(pg 81 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Aerobic biological treatment process capable of at least 85% removal of BOD and total
suspended solids. - CORRECT ANSWER: Secondary treatment
(pg 39 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
An Imhoff cone is used to measure________solids.
A. suspended
B. colloidal
C. volatile
D. settleable - CORRECT ANSWER: D. settleable
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
,At a WWTP, what can the following color codes on piping indicate?
Brown
Orange
Green
Blue
Gray
Yellow
Purple - CORRECT ANSWER: Brown=Sludge
Orange=Natural Gas/Digester Gas
Green=Compressed air
Blue=Water
Gray=Wastewater
Yellow=Chlorine
Purple=Reuse
(pg 83 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
At what point of the day do wastewater stabilization ponds have the lowest pH? -
CORRECT ANSWER: Late night & early morning. Diurnal variations of both pH and
dissolved oxygen are found in wastewater treatment ponds. During the day, algae use
carbon dioxide which raises the pH while at night they produce carbon dioxide and the
pH is lowered.
(Operation of Wastewater Treatment Plants, Volume 1, section 9.3
by Kenneth D. Kerri)
Chemical used to dechlorinate samples for BOD testing - CORRECT ANSWER: Sodium
Sulfite
, (pg 76 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Chlorine gas is _________ times (heavier or lighter?) than air. - CORRECT ANSWER:
The gas form of chlorine is 2.5 times heavier than air.
(Module #24, Gas Chlorination, Pennsylvania Department of Environmental Protection)
Classification of fires; used to determine the type of extinguisher:
Wood, paper, rubbish, etc.
Oil, solvents, gasoline, etc.
Electrical - CORRECT ANSWER: Wood, paper, rubbish, etc.= Class A
Oil, solvents, gasoline, etc.= Class B
Electrical= Class C
(pg 83 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Commonly used anaerobic digester process control tests - CORRECT ANSWER: pH
Volatile Acid/Alkalinity ratio
Digester gas percent CO2
(pg 17 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Distributes seal water uniformly around the pump shaft. - CORRECT ANSWER: Lantern
Ring
(pg 80 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
(Levels 1-2 Exam Prep) Latest Update 2025-2026
125 Questions and 100% Verified Correct
Answers Guaranteed A+
______ is the anoxic biological reduction of nitrate nitrogen to nitrogen gas. -
CORRECT ANSWER: Denitrification is the anoxic biological reduction of nitrate nitrogen
to nitrogen gas. In secondary clarifiers the nitrogen bubbles produced as a result of
denitrification can attach to the biological floc and float the floc to the surface. This
condition is often the cause of rising sludge.
(Operation of Wastewater Treatment Plants, Volume 1, section 7.0
by Kenneth D. Kerri)
_______ is an aerobic process in which bacteria change the ammonia and organic
nitrogen in wastewater into oxidized nitrogen (usually nitrate). The second-stage BOD is
sometimes referred to as the "nitrogenous BOD" (first-stage BOD is called the
"carbonaceous BOD"). - CORRECT ANSWER: Nitrification is an aerobic process in
which bacteria change the ammonia and organic nitrogen in wastewater into oxidized
nitrogen (usually nitrate). The second-stage BOD is sometimes referred to as the
"nitrogenous BOD" (first-stage BOD is called the "carbonaceous BOD").
(Operation of Wastewater Treatment Plants, Volume 1, section 7.0
by Kenneth D. Kerri)
A _____ flume is widely used for measuring wastewater flow. - CORRECT ANSWER:
Parshall
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
,A minimum dissolved oxygen (D.O.) level of _____ mg/L is recommended in the
aeration tank for most basic types of activated sludge processes. - CORRECT
ANSWER: A minimum dissolved oxygen (D.O.) level of 1.0 mg/L is recommended in the
aeration tank for most basic types of activated sludge processes. Maintaining > 1.0
mg/L of D.O. contributes to establishing a favorable environment for the organisms,
which produces the desired type of organism and the desired level of activity.
(New Mexico Wastewater Systems Operator Certification Study Manual)
A three phase pump motor is rotating the wrong direction after repairing and replacing it.
What is a likely solution to this problem? - CORRECT ANSWER: Switch any two of the
three electrical leads to the motor.
(pg 81 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Aerobic biological treatment process capable of at least 85% removal of BOD and total
suspended solids. - CORRECT ANSWER: Secondary treatment
(pg 39 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
An Imhoff cone is used to measure________solids.
A. suspended
B. colloidal
C. volatile
D. settleable - CORRECT ANSWER: D. settleable
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
,At a WWTP, what can the following color codes on piping indicate?
Brown
Orange
Green
Blue
Gray
Yellow
Purple - CORRECT ANSWER: Brown=Sludge
Orange=Natural Gas/Digester Gas
Green=Compressed air
Blue=Water
Gray=Wastewater
Yellow=Chlorine
Purple=Reuse
(pg 83 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
At what point of the day do wastewater stabilization ponds have the lowest pH? -
CORRECT ANSWER: Late night & early morning. Diurnal variations of both pH and
dissolved oxygen are found in wastewater treatment ponds. During the day, algae use
carbon dioxide which raises the pH while at night they produce carbon dioxide and the
pH is lowered.
(Operation of Wastewater Treatment Plants, Volume 1, section 9.3
by Kenneth D. Kerri)
Chemical used to dechlorinate samples for BOD testing - CORRECT ANSWER: Sodium
Sulfite
, (pg 76 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Chlorine gas is _________ times (heavier or lighter?) than air. - CORRECT ANSWER:
The gas form of chlorine is 2.5 times heavier than air.
(Module #24, Gas Chlorination, Pennsylvania Department of Environmental Protection)
Classification of fires; used to determine the type of extinguisher:
Wood, paper, rubbish, etc.
Oil, solvents, gasoline, etc.
Electrical - CORRECT ANSWER: Wood, paper, rubbish, etc.= Class A
Oil, solvents, gasoline, etc.= Class B
Electrical= Class C
(pg 83 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Commonly used anaerobic digester process control tests - CORRECT ANSWER: pH
Volatile Acid/Alkalinity ratio
Digester gas percent CO2
(pg 17 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
Distributes seal water uniformly around the pump shaft. - CORRECT ANSWER: Lantern
Ring
(pg 80 "Wastewater Treatment Flash CERT!" 2013 second edition, Daniel W. Lundy)
