Page | 1
Operation of Wastewater Treatment Plants
(Levels 1-2 Exam Prep) Questions with
Detailed Verified Answers
Q: An Imhoff cone is used to measure________solids.
A. suspended
B. colloidal
C. volatile
D. settleable
Ans: D. settleable
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
Q: A _____ flume is widely used for measuring wastewater flow.
Ans: Parshall
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
Q: Velocity of flow in a grit channel must be reduced to a range of
____ to _____ fps in order for grit to properly settle.
, Page | 2
Ans: .7 to 1.4 fps
(Operation of Wastewater Treatment Plants, Volume 1, 3.33
by Kenneth D. Kerri)
Q: With respect to grit removal systems, grit is traditionally defined
as particles larger than 0.21mm (0.008 in) (65 mesh) and with a
specific gravity of greater than ______.
Ans: specific gravity of grit is 2.65 or greater
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
Q: Mechanically cleaned bar screens feature bars set at _____ to
_____ degrees from vertical.
Ans: Bars set at 0 to 30 degrees from vertical.
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
Q: Manually cleaned bar screens feature bars set at _____ to
_____ degrees from vertical to facilitate cleaning.
Ans: Bars set at 30 to 45 degrees from vertical to facilitate cleaning.
Primarily used in older or smaller treatment facilities, or in bypass
channels.
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
, Page | 3
Q: The BOD test measures the amount of oxygen that is consumed
while a sample of wastewater is incubated in the dark at a
temperature of _____ °C for _____ days (± _____ hours)
Ans: The BOD test measures the amount of oxygen that is consumed
while a sample of wastewater is incubated in the dark at a
temperature of 20 °C for 5 days (± 3 hours)
(USGS Book 9-A7 (Third Edition) Five-Day Biochemical Oxygen
Demand)
Q: What do we mean by Total Dissolved Solids (TDS) in
wastewater?
Ans: All the solids that cannot be filtered out of the water
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: What do we mean by Total Suspended Solids (TSS) in
wastewater?
Ans: All the solids that can be filtered out including: settleable solids
and non-settleable solids (colloids)
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: The wastewater in a sewer line should move at a speed that
will prevent the deposition and buildup of solids in the sewer; this
is called a "scouring velocity". A minimum velocity of _____ fps
provides this scouring or self-cleaning velocity.
, Page | 4
Ans: The wastewater in a sewer line should move at a speed that will
prevent the deposition and buildup of solids in the sewer; this is called
a "scouring velocity". A minimum velocity of 2 fps provides this scouring
or self-cleaning velocity.
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: Wastewater treatment ponds: Facultative ponds are _____ feet
deep
Ans: Facultative ponds are 4-8 feet deep
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: Wastewater treatment ponds: Anaerobic ponds are _____ feet
deep
Ans: Anaerobic ponds are >14 feet in depth
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: Typical Primary Clarifier Efficiencies: Settleable Solids expected
removal efficiency _____% to _____%
Operation of Wastewater Treatment Plants
(Levels 1-2 Exam Prep) Questions with
Detailed Verified Answers
Q: An Imhoff cone is used to measure________solids.
A. suspended
B. colloidal
C. volatile
D. settleable
Ans: D. settleable
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
Q: A _____ flume is widely used for measuring wastewater flow.
Ans: Parshall
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
Q: Velocity of flow in a grit channel must be reduced to a range of
____ to _____ fps in order for grit to properly settle.
, Page | 2
Ans: .7 to 1.4 fps
(Operation of Wastewater Treatment Plants, Volume 1, 3.33
by Kenneth D. Kerri)
Q: With respect to grit removal systems, grit is traditionally defined
as particles larger than 0.21mm (0.008 in) (65 mesh) and with a
specific gravity of greater than ______.
Ans: specific gravity of grit is 2.65 or greater
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
Q: Mechanically cleaned bar screens feature bars set at _____ to
_____ degrees from vertical.
Ans: Bars set at 0 to 30 degrees from vertical.
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
Q: Manually cleaned bar screens feature bars set at _____ to
_____ degrees from vertical to facilitate cleaning.
Ans: Bars set at 30 to 45 degrees from vertical to facilitate cleaning.
Primarily used in older or smaller treatment facilities, or in bypass
channels.
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
, Page | 3
Q: The BOD test measures the amount of oxygen that is consumed
while a sample of wastewater is incubated in the dark at a
temperature of _____ °C for _____ days (± _____ hours)
Ans: The BOD test measures the amount of oxygen that is consumed
while a sample of wastewater is incubated in the dark at a
temperature of 20 °C for 5 days (± 3 hours)
(USGS Book 9-A7 (Third Edition) Five-Day Biochemical Oxygen
Demand)
Q: What do we mean by Total Dissolved Solids (TDS) in
wastewater?
Ans: All the solids that cannot be filtered out of the water
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: What do we mean by Total Suspended Solids (TSS) in
wastewater?
Ans: All the solids that can be filtered out including: settleable solids
and non-settleable solids (colloids)
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: The wastewater in a sewer line should move at a speed that
will prevent the deposition and buildup of solids in the sewer; this
is called a "scouring velocity". A minimum velocity of _____ fps
provides this scouring or self-cleaning velocity.
, Page | 4
Ans: The wastewater in a sewer line should move at a speed that will
prevent the deposition and buildup of solids in the sewer; this is called
a "scouring velocity". A minimum velocity of 2 fps provides this scouring
or self-cleaning velocity.
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: Wastewater treatment ponds: Facultative ponds are _____ feet
deep
Ans: Facultative ponds are 4-8 feet deep
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: Wastewater treatment ponds: Anaerobic ponds are _____ feet
deep
Ans: Anaerobic ponds are >14 feet in depth
(New Mexico Wastewater Systems Operator Certification Study
Manual)
Q: Typical Primary Clarifier Efficiencies: Settleable Solids expected
removal efficiency _____% to _____%
