Wastewater Treatment Operator Certification Test – Updated 2025 | Latest Verified Questions & Answers

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Wastewater Treatment Operator Certification Test #2 (NEW UPDATED
VERSION) LATEST ACTUAL EXAM QUESTIONS AND CORRECT ANSWERS (VERIFIED
QUESTIONS AND ANSWERS) | GUARANTEED PASS A+ UPDATED THIS YEAR




What is the typical BOD removal efficiency in a primary clarifier?


A) 10 to 15%
B) 40 to 60%
C) 20 to 50%

D) 95 to 99% - CORRECT ANSWER C) 20 to 50% (v.1 pg 129)



QUESTION :What does the "F" in F/M ratio represent?


A) The microorganism population in the aeration tank
B) The amount of filamentous bacteria in the activated sludge process
C) The MLVSS in the aeration tank

D) The food for the microorganisms flowing into the aeration tank, in lbs/day - CORRECT
ANSWER D) The food for the microorganisms flowing into the aeration tank, in lbs/day (v.2
pg 58)


QUESTION :Which of the following describes the appearance of healthy activated sludge?


A) Thick, greasy, dark tan foam
B) Brown with a moderate amount of crisp, white foam
C) Clear liquid with clear foam

D) Gray liquid with no foam - CORRECT ANSWER B) Brown with a moderate amount of
crisp, white foam




2026 2027 GRADED A+

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QUESTION :What is used to control filamentous organisms?


A) Polymer
B) Sulfur Dioxide
C) Coagulant

D) Chlorine - CORRECT ANSWER D) Chlorine (v.1 pg 399)



QUESTION :What are commonly used to control chlorine feed rate for disinfection?


A) BOD and MLVSS
B) pH and temperature
C) Flow and chlorine residual

D) DO and TSS - CORRECT ANSWER C) Flow and chlorine residual (v.1 pg 356)



QUESTION :Which toxic gas is commonly found in septic wastewater and smells like rotten
eggs?


A) Hydrogen Sulfide
B) Carbon monoxide
C) Hydrogen

D) Carbon Dioxide - CORRECT ANSWER A) Hydrogen Sulfide (v.2 pg 299)



QUESTION :What is the permissible exposure limit for chlorine gas vapor during a normal 8
hour workday and a 40 hour work week?


A) 0.1 ppm
B) 0.5 ppm
C) 1 ppm

D) 15 ppm - CORRECT ANSWER B) 0.5 ppm (v.2 pg 268)




2026 2027 GRADED A+

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QUESTION :What is a vulnerability assessment?


A) Assesses the impact of hydrogen sulfide to a concrete structure
B) Analyzes the impact of flow and infiltration problem to the plant hydraulics
C) Estimates the vulnerability of aquatic wildlife to excessive algae growth
D) Contingency planning to determine the vulnerability of the utility during various types of
emergencies and identify corrective actions to reduce the risks - CORRECT ANSWER D)
Contingency planning to determine the vulnerability of the utility during various types of
emergencies and identify corrective actions to reduce the risks (v.2 pg 722)


QUESTION :What is the difference between the settling rate of activated sludge and raw
sludge?


A) Activated sludge settles slightly faster than raw sludge
B) Activated sludge settles at the same rate as raw sludge
C) Activated sludge settles slower than raw sludge

D) Activated sludge settles much faster than raw sludge - CORRECT ANSWER C)
Activated sludge settles slower than raw sludge (v.1 pg 109)


QUESTION :What should be mostly found in healthy activated sludge?


A) Tiny flagellates
B) Amoeboids
C) Short Filaments

D) Free swimmers and stalked ciliates - CORRECT ANSWER D) Free swimmers and
stalked ciliates (v.2 pg 120,124)


QUESTION :One to two percent of the digester gas in an anaerobic consists of


A) Hydrogen, Nitrogen, Hydrogen sulfide, and other gases
B) Methane
C) Carbon Dioxide


2026 2027 GRADED A+