Wastewater Treatment Operator Certification
Comprehensive Resource To Help You Ace 2026-2027
Includes Frequently Tested Questions With ELABORATED
100% Correct COMPLETE SOLUTIONS
Guaranteed Pass First Attempt!!
Current Update!!
1. 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
2. What is used to control filamentous organisms?
A) Polymer
B) Sulfur Dioxide
C) Coagulant
D) Chlorine - Correct Answer: D) Chlorine (v.1 pg 399)
3. 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)
4. 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)
5. What is commonly used to control the odor of hydrogen sulfide?
A) Carbon Dioxide
B) Methane
C) Chlorine
D) Hydrogen - Correct Answer: C) Chlorine (v.1 pg 398)
6. 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)
7. 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)
8. 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)
9. 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)
10. 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
D) CH_4 - Correct Answer: A) Hydrogen, Nitrogen, Hydrogen sulfide, and other
gases (v.2 pg 158)
11. What is true during the colder winter months?
A) Modify operations to decrease solids under aeration to provide less
microorganisms to treat the BOD
B) Modify operations to increase solids under aeration to provide more
microorganisms to treat the BOD
C) Biological activity will increase, which results in more overall sludge production
D) Microorganisms become more active - Correct Answer: B) Modify operations
to increase solids under aeration to provide more microorganisms to treat the
BOD (v.2 pg 71)
12. What type of sludge would you expect in an aeration tank if the content is dark and has
low DO?
A) Sludge that is heavy
B) Chlorinated Sludge
C) Septic Sludge
D) Healthy Sludge - Correct Answer: C) Septic Sludge (v.2 pg 75)
Comprehensive Resource To Help You Ace 2026-2027
Includes Frequently Tested Questions With ELABORATED
100% Correct COMPLETE SOLUTIONS
Guaranteed Pass First Attempt!!
Current Update!!
1. 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
2. What is used to control filamentous organisms?
A) Polymer
B) Sulfur Dioxide
C) Coagulant
D) Chlorine - Correct Answer: D) Chlorine (v.1 pg 399)
3. 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)
4. 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)
5. What is commonly used to control the odor of hydrogen sulfide?
A) Carbon Dioxide
B) Methane
C) Chlorine
D) Hydrogen - Correct Answer: C) Chlorine (v.1 pg 398)
6. 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)
7. 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)
8. 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)
9. 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)
10. 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
D) CH_4 - Correct Answer: A) Hydrogen, Nitrogen, Hydrogen sulfide, and other
gases (v.2 pg 158)
11. What is true during the colder winter months?
A) Modify operations to decrease solids under aeration to provide less
microorganisms to treat the BOD
B) Modify operations to increase solids under aeration to provide more
microorganisms to treat the BOD
C) Biological activity will increase, which results in more overall sludge production
D) Microorganisms become more active - Correct Answer: B) Modify operations
to increase solids under aeration to provide more microorganisms to treat the
BOD (v.2 pg 71)
12. What type of sludge would you expect in an aeration tank if the content is dark and has
low DO?
A) Sludge that is heavy
B) Chlorinated Sludge
C) Septic Sludge
D) Healthy Sludge - Correct Answer: C) Septic Sludge (v.2 pg 75)
