OPERATION OF WASTEWATER TREATMENT PLANTS
(LEVELS 1-2 EXAM PREP) EXAM QUESTIONS AND
ANSWERS
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)
A _____ flume is widely used for measuring wastewater flow. - CORRECT ANSWER✅✅Parshall
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
Velocity of flow in a grit channel must be reduced to a range of ____ to _____ fps in order for grit to
properly settle. - CORRECT ANSWER✅✅.7 to 1.4 fps
(Operation of Wastewater Treatment Plants, Volume 1, 3.33
by Kenneth D. Kerri)
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 ______. - CORRECT ANSWER✅✅specific gravity
of grit is 2.65 or greater
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
,Mechanically cleaned bar screens feature bars set at _____ to _____ degrees from vertical. - CORRECT
ANSWER✅✅Bars set at 0 to 30 degrees from vertical.
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
Manually cleaned bar screens feature bars set at _____ to _____ degrees from vertical to facilitate
cleaning. - CORRECT ANSWER✅✅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)
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) - CORRECT
ANSWER✅✅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)
What do we mean by Total Dissolved Solids (TDS) in wastewater? - CORRECT ANSWER✅✅All the solids
that cannot be filtered out of the water
(New Mexico Wastewater Systems Operator Certification Study Manual)
What do we mean by Total Suspended Solids (TSS) in wastewater? - CORRECT ANSWER✅✅All the solids
that can be filtered out including: settleable solids and non-settleable solids (colloids)
(New Mexico Wastewater Systems Operator Certification Study Manual)
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. - CORRECT ANSWER✅✅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)
Wastewater treatment ponds: Facultative ponds are _____ feet deep - CORRECT
ANSWER✅✅Facultative ponds are 4-8 feet deep
(New Mexico Wastewater Systems Operator Certification Study Manual)
Wastewater treatment ponds: Anaerobic ponds are _____ feet deep - CORRECT ANSWER✅✅Anaerobic
ponds are >14 feet in depth
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Settleable Solids expected removal efficiency _____% to _____% -
CORRECT ANSWER✅✅Typical Primary Clarifier Efficiencies: Settleable Solids expected removal
efficiency 95% to 99%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Suspended Solids expected removal efficiency _____% to _____% -
CORRECT ANSWER✅✅Typical Primary Clarifier Efficiencies: Suspended Solids expected removal
efficiency 40% to 60%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Total Solids expected removal efficiency _____% to _____% -
CORRECT ANSWER✅✅Typical Primary Clarifier Efficiencies: Total Solids expected removal efficiency
10% to 15%
(LEVELS 1-2 EXAM PREP) EXAM QUESTIONS AND
ANSWERS
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)
A _____ flume is widely used for measuring wastewater flow. - CORRECT ANSWER✅✅Parshall
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
Velocity of flow in a grit channel must be reduced to a range of ____ to _____ fps in order for grit to
properly settle. - CORRECT ANSWER✅✅.7 to 1.4 fps
(Operation of Wastewater Treatment Plants, Volume 1, 3.33
by Kenneth D. Kerri)
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 ______. - CORRECT ANSWER✅✅specific gravity
of grit is 2.65 or greater
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
,Mechanically cleaned bar screens feature bars set at _____ to _____ degrees from vertical. - CORRECT
ANSWER✅✅Bars set at 0 to 30 degrees from vertical.
(EPA Wastewater Technology Fact Sheet, Screening and Grit Removal)
Manually cleaned bar screens feature bars set at _____ to _____ degrees from vertical to facilitate
cleaning. - CORRECT ANSWER✅✅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)
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) - CORRECT
ANSWER✅✅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)
What do we mean by Total Dissolved Solids (TDS) in wastewater? - CORRECT ANSWER✅✅All the solids
that cannot be filtered out of the water
(New Mexico Wastewater Systems Operator Certification Study Manual)
What do we mean by Total Suspended Solids (TSS) in wastewater? - CORRECT ANSWER✅✅All the solids
that can be filtered out including: settleable solids and non-settleable solids (colloids)
(New Mexico Wastewater Systems Operator Certification Study Manual)
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. - CORRECT ANSWER✅✅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)
Wastewater treatment ponds: Facultative ponds are _____ feet deep - CORRECT
ANSWER✅✅Facultative ponds are 4-8 feet deep
(New Mexico Wastewater Systems Operator Certification Study Manual)
Wastewater treatment ponds: Anaerobic ponds are _____ feet deep - CORRECT ANSWER✅✅Anaerobic
ponds are >14 feet in depth
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Settleable Solids expected removal efficiency _____% to _____% -
CORRECT ANSWER✅✅Typical Primary Clarifier Efficiencies: Settleable Solids expected removal
efficiency 95% to 99%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Suspended Solids expected removal efficiency _____% to _____% -
CORRECT ANSWER✅✅Typical Primary Clarifier Efficiencies: Suspended Solids expected removal
efficiency 40% to 60%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Total Solids expected removal efficiency _____% to _____% -
CORRECT ANSWER✅✅Typical Primary Clarifier Efficiencies: Total Solids expected removal efficiency
10% to 15%
