Page 1 of 136
Wastewater Treatment Operator Certification Test 1-
TEST 4, 2026-2027 COMPLETE 350 QUESTIONS AND
VERIFIED SOLUTIONS LATEST UPDATE THIS YEAR
Wastewater Treatment Operator Certification TEST 1
QUESTION: What is the purpose of a Parshall flume?
A) measure turbidity
B) measure flowrate
C) measure settling rate
D) measure solids content - ANSWER-B) measure flowrate (v.1 pg 43)
QUESTION: What is the typical removal efficiency of settable solids in a primary clarifier?
A) 95 to 99%
B) 40 to 60%
C) 20 to 50%
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D) 10 to 15% - 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. - 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
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D) MLSS is too low - ANSWER-D) MLSS is too low (v.2 pg 53,75)
Q; 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 - 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 - ANSWER-D) Decrease the pH (v.1 pg 349-350)
, Page 4 of 136
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 - ANSWER-C) The mixed liquor volatile
suspended solids in the aeration tank (v.2 pg 16)
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 - ANSWER-B) Increase the settling rate (v.1 pg 134)
Wastewater Treatment Operator Certification Test 1-
TEST 4, 2026-2027 COMPLETE 350 QUESTIONS AND
VERIFIED SOLUTIONS LATEST UPDATE THIS YEAR
Wastewater Treatment Operator Certification TEST 1
QUESTION: What is the purpose of a Parshall flume?
A) measure turbidity
B) measure flowrate
C) measure settling rate
D) measure solids content - ANSWER-B) measure flowrate (v.1 pg 43)
QUESTION: What is the typical removal efficiency of settable solids in a primary clarifier?
A) 95 to 99%
B) 40 to 60%
C) 20 to 50%
,Page 2 of 136
D) 10 to 15% - 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. - 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
,Page 3 of 136
D) MLSS is too low - ANSWER-D) MLSS is too low (v.2 pg 53,75)
Q; 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 - 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 - ANSWER-D) Decrease the pH (v.1 pg 349-350)
, Page 4 of 136
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 - ANSWER-C) The mixed liquor volatile
suspended solids in the aeration tank (v.2 pg 16)
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 - ANSWER-B) Increase the settling rate (v.1 pg 134)
