Wastewater Grade 2 Study Questions and
answers 2026\2027 A+ Grade
What is the methane content in a properly operating anaerobic digester?
a. 30 to 35% by volume
b. 1 to 2% by volume
c. 65 to 70% by volume
d. 15 to 20 % by volume
- correct answer c
What will the addition of chlorine gas do to the pH of wastewater?
a. Moderately increase the pH
b. pH will not be affected
c. Significantly increase the pH
d. Decrease the pH
- correct answer d
What is the purpose of a Parshall flume?
a. Measure turbidity
b. Measure flowrate
c. Measure settling rate
d. Measure solids content
- correct answer b
What is the typical removal efficiency of settleable solids in a primary clarifier?
,a. 95 to 99%
b. 40 to 60%
C. 20 to 50%
d. 10 to 15%
- correct answer a
Which of the following is true about pumping scum from a primary clarifier?
a. Pumping scum is less problematic during cold weather
b. Scum rarely leads to plugged pipelines due to its viscous nature
c. Scum causes more piping problems than other substances pumped at a wastewater treatment plant.
d. Scum causes the least amount of piping problems among all the substances pumped at a wastewater
treatment plant pumped at a wastewater treatment plant
- correct answer c
What might cause thick billows of white sudsy foam in the aeration tank?
a. MLSS is too high
b. Temperature in the aeration tank is too low
c. Old sludge
d. MLSS is too low
- correct answer d
What does the "M" in F/M ratio represent?
a. MLSS in the aeration tank
b. The influent BOD loading rate into the aeration tank
c. The mixed liquor volatile suspended solids in the aeration tank
,d. The mass of inorganic solids in the aeration tank
- correct answer c
In general- how will warmer temperature affect the settling rate of solids in a clarifier?
a. Decrease the settling rate
b. Increase the settling rate
c. Temperature will not affect the settling rate
d. Worsens the settling rate
- correct answer b
What could happen if the digester gas is mixed with air (85 TO 95% by volume)?
a. Cause an explosion
b. Improve efficiency of digestion
c. The bacteria will become aerobic and increase VSR
d. The digester becomes safer to operate due to less toxic gas in the system.
- correct answer a
How will algae impact the chlorine demand in the pond effluent?
a. Slightly decreases chlorine demand
b. Does not affect chlorine demand
c. Significantly decreases chlorine demand
d. Increases chlorine demand
- correct answer d
Which of the following is true about a positive displacement pump?
a. It is a type of centrifugal pump
, b. Suction valve should be closed when the pump is started
c. It must never be started with the discharge valve closed
d. Adds head to liquid using several impellers
- correct answer c
What is true about the F/M ratio?
a. MLVSS data is not required to determine the F/M ratio
b. Volume of the secondary clarifier is not needed to determine the F/M ratio
c. The amount of COD or BOD entering the aeration tank does not have to be known to calculate the
F/M ratio
d. The amount of organisms in the aeration tank is not needed to calculate the F /M ratio
- correct answer b
Which of the following is one of the basic rules of laboratory work?
a. Do not leave keys in equipment or vehicles at any time
b. Patrol the facilities frequently and look for suspicious activity or behavior
c. Never pipet hazardous material with your mouth even if the pi pet has been sterilized
d. Lock out and tag out relevant mechanical and electrical equipment before starting any maintenance
activity
- correct answer c
What is the recirculation ratio for a trickling filter?
a. Qr/Q
b. Q/Qr
c. Q/ Qr+Q
d. Qr+Q/Q
- correct answer a
answers 2026\2027 A+ Grade
What is the methane content in a properly operating anaerobic digester?
a. 30 to 35% by volume
b. 1 to 2% by volume
c. 65 to 70% by volume
d. 15 to 20 % by volume
- correct answer c
What will the addition of chlorine gas do to the pH of wastewater?
a. Moderately increase the pH
b. pH will not be affected
c. Significantly increase the pH
d. Decrease the pH
- correct answer d
What is the purpose of a Parshall flume?
a. Measure turbidity
b. Measure flowrate
c. Measure settling rate
d. Measure solids content
- correct answer b
What is the typical removal efficiency of settleable solids in a primary clarifier?
,a. 95 to 99%
b. 40 to 60%
C. 20 to 50%
d. 10 to 15%
- correct answer a
Which of the following is true about pumping scum from a primary clarifier?
a. Pumping scum is less problematic during cold weather
b. Scum rarely leads to plugged pipelines due to its viscous nature
c. Scum causes more piping problems than other substances pumped at a wastewater treatment plant.
d. Scum causes the least amount of piping problems among all the substances pumped at a wastewater
treatment plant pumped at a wastewater treatment plant
- correct answer c
What might cause thick billows of white sudsy foam in the aeration tank?
a. MLSS is too high
b. Temperature in the aeration tank is too low
c. Old sludge
d. MLSS is too low
- correct answer d
What does the "M" in F/M ratio represent?
a. MLSS in the aeration tank
b. The influent BOD loading rate into the aeration tank
c. The mixed liquor volatile suspended solids in the aeration tank
,d. The mass of inorganic solids in the aeration tank
- correct answer c
In general- how will warmer temperature affect the settling rate of solids in a clarifier?
a. Decrease the settling rate
b. Increase the settling rate
c. Temperature will not affect the settling rate
d. Worsens the settling rate
- correct answer b
What could happen if the digester gas is mixed with air (85 TO 95% by volume)?
a. Cause an explosion
b. Improve efficiency of digestion
c. The bacteria will become aerobic and increase VSR
d. The digester becomes safer to operate due to less toxic gas in the system.
- correct answer a
How will algae impact the chlorine demand in the pond effluent?
a. Slightly decreases chlorine demand
b. Does not affect chlorine demand
c. Significantly decreases chlorine demand
d. Increases chlorine demand
- correct answer d
Which of the following is true about a positive displacement pump?
a. It is a type of centrifugal pump
, b. Suction valve should be closed when the pump is started
c. It must never be started with the discharge valve closed
d. Adds head to liquid using several impellers
- correct answer c
What is true about the F/M ratio?
a. MLVSS data is not required to determine the F/M ratio
b. Volume of the secondary clarifier is not needed to determine the F/M ratio
c. The amount of COD or BOD entering the aeration tank does not have to be known to calculate the
F/M ratio
d. The amount of organisms in the aeration tank is not needed to calculate the F /M ratio
- correct answer b
Which of the following is one of the basic rules of laboratory work?
a. Do not leave keys in equipment or vehicles at any time
b. Patrol the facilities frequently and look for suspicious activity or behavior
c. Never pipet hazardous material with your mouth even if the pi pet has been sterilized
d. Lock out and tag out relevant mechanical and electrical equipment before starting any maintenance
activity
- correct answer c
What is the recirculation ratio for a trickling filter?
a. Qr/Q
b. Q/Qr
c. Q/ Qr+Q
d. Qr+Q/Q
- correct answer a
