1|Page
Wastewater Treatment Operator Certification Test #1 (NEW UPDATED VERSION) LATEST ACTUAL
EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED QUESTIONS AND ANSWERS) | GUARANTEED PASS
A+ UPDATED THIS YEAR
What is the methane content in a properly operation 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) 65 to 70% by volume (v.2 pg 158)
QUESTION :What will the addition of chlorine gas do to the pH of wastewater?
A) Moderately increase pH
B) pH will not be affected
C) Significantly increase the pH
D) Decrease the pH - CORRECT ANSWER D) Decrease the pH (v.1 pg 349-350)
QUESTION :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) measure flowrate (v.1 pg 43)
QUESTION :What is the typical removal efficiency of settable solids in a primary clarifier?
2026 2027 GRADED A+
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A) 95 to 99%
B) 40 to 60%
C) 20 to 50%
D) 10 to 15% - CORRECT ANSWER A) 95 to 99% (v.1 pg 129)
QUESTION :Which of the following is true about pumping scum from a primary clarifier?
A) Pumping scum is less problematic during colder 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. - CORRECT ANSWER C) Scum causes more piping
problems than other substances pumped at a wastewater treatment plant. (v.2 pg 449)
QUESTION :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) MLSS is too low (v.2 pg 53,75)
QUESTION :What does the "M" in F/M ratio represent?
A) MLSS in 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) The mixed
liquor volatile suspended solids in the aeration tank (v.2 pg 16)
2026 2027 GRADED A+
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QUESTION :In general, how will warmer temperature affect the settling rate of solids in a
clarifier?
A) Decrease settling rate
B) Increase the settling rate
C) Temperature will not affect the settling rate
D) Worsen the settling rate - CORRECT ANSWER B) Increase the settling rate (v.1 pg
134)
QUESTION :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) Cause an explosion (v.2 pg 158)
QUESTION :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) Increases chlorine demand
QUESTION :Which of the following is true about positive displacement pumps?
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) It must never be
started with the discharge valve closed (v.2 pg 435)
2026 2027 GRADED A+
Wastewater Treatment Operator Certification Test #1 (NEW UPDATED VERSION) LATEST ACTUAL
EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED QUESTIONS AND ANSWERS) | GUARANTEED PASS
A+ UPDATED THIS YEAR
What is the methane content in a properly operation 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) 65 to 70% by volume (v.2 pg 158)
QUESTION :What will the addition of chlorine gas do to the pH of wastewater?
A) Moderately increase pH
B) pH will not be affected
C) Significantly increase the pH
D) Decrease the pH - CORRECT ANSWER D) Decrease the pH (v.1 pg 349-350)
QUESTION :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) measure flowrate (v.1 pg 43)
QUESTION :What is the typical removal efficiency of settable solids in a primary clarifier?
2026 2027 GRADED A+
,2|Page
A) 95 to 99%
B) 40 to 60%
C) 20 to 50%
D) 10 to 15% - CORRECT ANSWER A) 95 to 99% (v.1 pg 129)
QUESTION :Which of the following is true about pumping scum from a primary clarifier?
A) Pumping scum is less problematic during colder 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. - CORRECT ANSWER C) Scum causes more piping
problems than other substances pumped at a wastewater treatment plant. (v.2 pg 449)
QUESTION :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) MLSS is too low (v.2 pg 53,75)
QUESTION :What does the "M" in F/M ratio represent?
A) MLSS in 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) The mixed
liquor volatile suspended solids in the aeration tank (v.2 pg 16)
2026 2027 GRADED A+
, 3|Page
QUESTION :In general, how will warmer temperature affect the settling rate of solids in a
clarifier?
A) Decrease settling rate
B) Increase the settling rate
C) Temperature will not affect the settling rate
D) Worsen the settling rate - CORRECT ANSWER B) Increase the settling rate (v.1 pg
134)
QUESTION :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) Cause an explosion (v.2 pg 158)
QUESTION :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) Increases chlorine demand
QUESTION :Which of the following is true about positive displacement pumps?
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) It must never be
started with the discharge valve closed (v.2 pg 435)
2026 2027 GRADED A+
