Operation of Wastewater Treatment prep complete
exam questions and verified answers 2024/2025
An Imhoff cone is used to measure________solids.
A. suspended
B. colloidal
C. volatile
D. settleable
D. settleable
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
A _____ flume is widely used for measuring wastewater flow.
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.
.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 ______.
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.
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.
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)
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?
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?
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.
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
Facultative ponds are 4-8 feet deep
(New Mexico Wastewater Systems Operator Certification Study Manual)
Wastewater treatment ponds: Anaerobic ponds are _____ feet deep
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 _____%
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 _____%
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 _____%
Typical Primary Clarifier Efficiencies: Total Solids expected removal efficiency 10% to 15%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Biochemical Oxygen Demand (BOD) expected removal efficiency
_____% to _____%
, Typical Primary Clarifier Efficiencies: Biochemical Oxygen Demand (BOD) expected removal efficiency
20% to 50%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Sludge septicity in the primary clarifier can be recognized when:
A. sludge gasification causes large clumps of sludge to float on the water surface.
B. Primary clarifier foam is black
C. The Specific Oxygen Uptake Rate (SOUR) in the primary clarifier is greater than 3000 mg O2/L/hr
D. The sludge contains from 4.0 to 8.0 percent dry solids in TS laboratory testing
E. All of the above
A. sludge gasification causes large clumps of sludge to float on the water surface.
Pump cavitation may be caused by:
A. Loss of discharge pressure due to open hy-drants or line breaks
B. Closed suction valve
C. Obstruction in the suction line
D. Low suction head due to drop in water level
E. All of the above
E. All of the above
(New Mexico Wastewater Systems Operator Certification Study Manual)
A minimum dissolved oxygen (D.O.) level of _____ mg/L is recommended in the aeration tank for
most basic types of activated sludge processes.
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)
If the D.O. in the aeration tank is allowed to drop too low for long periods, undesirable organisms,
such as ____________________________ may develop and overtake the process.
If the D.O. in the aeration tank is allowed to drop too low for long periods, undesirable organisms,
such as filamentous type bacteria may develop and overtake the process.
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical operating parameters for conventional activated sludge systems:
exam questions and verified answers 2024/2025
An Imhoff cone is used to measure________solids.
A. suspended
B. colloidal
C. volatile
D. settleable
D. settleable
(Operation of Wastewater Treatment Plants, Volume 1
by Kenneth D. Kerri)
A _____ flume is widely used for measuring wastewater flow.
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.
.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 ______.
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.
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.
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)
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?
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?
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.
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
Facultative ponds are 4-8 feet deep
(New Mexico Wastewater Systems Operator Certification Study Manual)
Wastewater treatment ponds: Anaerobic ponds are _____ feet deep
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 _____%
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 _____%
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 _____%
Typical Primary Clarifier Efficiencies: Total Solids expected removal efficiency 10% to 15%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical Primary Clarifier Efficiencies: Biochemical Oxygen Demand (BOD) expected removal efficiency
_____% to _____%
, Typical Primary Clarifier Efficiencies: Biochemical Oxygen Demand (BOD) expected removal efficiency
20% to 50%
(New Mexico Wastewater Systems Operator Certification Study Manual)
Sludge septicity in the primary clarifier can be recognized when:
A. sludge gasification causes large clumps of sludge to float on the water surface.
B. Primary clarifier foam is black
C. The Specific Oxygen Uptake Rate (SOUR) in the primary clarifier is greater than 3000 mg O2/L/hr
D. The sludge contains from 4.0 to 8.0 percent dry solids in TS laboratory testing
E. All of the above
A. sludge gasification causes large clumps of sludge to float on the water surface.
Pump cavitation may be caused by:
A. Loss of discharge pressure due to open hy-drants or line breaks
B. Closed suction valve
C. Obstruction in the suction line
D. Low suction head due to drop in water level
E. All of the above
E. All of the above
(New Mexico Wastewater Systems Operator Certification Study Manual)
A minimum dissolved oxygen (D.O.) level of _____ mg/L is recommended in the aeration tank for
most basic types of activated sludge processes.
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)
If the D.O. in the aeration tank is allowed to drop too low for long periods, undesirable organisms,
such as ____________________________ may develop and overtake the process.
If the D.O. in the aeration tank is allowed to drop too low for long periods, undesirable organisms,
such as filamentous type bacteria may develop and overtake the process.
(New Mexico Wastewater Systems Operator Certification Study Manual)
Typical operating parameters for conventional activated sludge systems:
