Page 1 of 96
Wastewater Treatment Operator Certification Test 2
2026-2027 COMPLETE 250 QUESTIONS AND VERIFIED
SOLUTIONS LATEST UPDATE THIS YEAR
Wastewater Treatment Operator Certification TEST 2
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 - ANSWER-B) Brown with a moderate amount of crisp, white foam
QUESTION: What is used to control filamentous organisms?
A) Polymer
B) Sulfur Dioxide
C) Coagulant
,Page 2 of 96
D) Chlorine - 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 - 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 - ANSWER-A) Hydrogen Sulfide (v.2 pg 299)
,Page 3 of 96
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 - ANSWER-B) 0.5 ppm (v.2 pg 268)
Q; 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% - ANSWER-C) 20 to 50% (v.1 pg 129)
QUESTION: What does the "F" in F/M ratio represent?
, Page 4 of 96
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 - ANSWER-D) The
food for the microorganisms flowing into the aeration tank, in lbs/day (v.2 pg 58)
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 - 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)
Wastewater Treatment Operator Certification Test 2
2026-2027 COMPLETE 250 QUESTIONS AND VERIFIED
SOLUTIONS LATEST UPDATE THIS YEAR
Wastewater Treatment Operator Certification TEST 2
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 - ANSWER-B) Brown with a moderate amount of crisp, white foam
QUESTION: What is used to control filamentous organisms?
A) Polymer
B) Sulfur Dioxide
C) Coagulant
,Page 2 of 96
D) Chlorine - 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 - 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 - ANSWER-A) Hydrogen Sulfide (v.2 pg 299)
,Page 3 of 96
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 - ANSWER-B) 0.5 ppm (v.2 pg 268)
Q; 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% - ANSWER-C) 20 to 50% (v.1 pg 129)
QUESTION: What does the "F" in F/M ratio represent?
, Page 4 of 96
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 - ANSWER-D) The
food for the microorganisms flowing into the aeration tank, in lbs/day (v.2 pg 58)
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 - 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)
