Wastewater Class B License Exam 2026 Prep with a Review
of 300 Textbook Questions and Correct Answers/ Class B
Wastewater Operator Exam 2026-2027 A Review of
Correctly Answered Exam Questions
What can an operator expect of an activated sludge that has excessive filamentous
organisms? - ANSWER-poor settling
What is an advantage of pure oxygen activated sludge systems over air activated
sludge systems? - ANSWER-they use smaller aeration (reactor) tanks
What is the function of the activated sludge process? - ANSWER-to remove
suspended and dissolved solids
What is the main cause of most odors in wastewater systems? - ANSWER-
Hydrogen sulfide
Hydrogen sulfide gas combines with moisture to form sulfuric acid, which is very
corrosive.
T or F - ANSWER-True
Which factor causes increased odor and corrosion problems in wastewater
treatment plants? - ANSWER-Increased travel times for wastewater to reach
treatment plants
1
,What is the principle source of odor generation in wastewater collection systems
and treatment processes? - ANSWER-Production of inorganic and organic gases
by microorganisms
Under what conditions should the reactor vent gas purity valve be "fine tuned"? -
ANSWER-when there is a drastic change in either the quantity or strength of the
wastewater entering the plant
When establishing an industrial waste monitoring program, what is one of the first
tasks? - ANSWER-an examination of the wastewater characteristics of each
industry that discharges to the collection system.
What is the purpose of the Respiration Rate for activated sludge test? To give some
insight into the - ANSWER-health of the microorganisms in the activated sludge
what does the BOD test measure? - ANSWER-the rate of oxygen uptake from the
wastewater by microorganisms in biochemical reactions
what are the major nutrients of concern in the activated sludge process? -
ANSWER-nitrogen and phosphorus
how can more nitrogen be added to industrial wastewater? more nitrogen can be
added in the form of - ANSWER-ammonia
how can more phosphorus be added to industrial wastewater? more phosphorus can
be added in the form of - ANSWER-phosphoric acid
liquid-solids separation is essential for successful biological process control
T or F - ANSWER-true
2
,enhanced biological treatment system flexibility is achieved by installing a large
number of treatment processes
T or F - ANSWER-false
If wastewater contains dissolved oxygen, the biological breakdown will reduce
sulfate to sulfide.
T or F - ANSWER-False
At a pH below 5, all sulfide is present in the gaseous h2s form and most of it can
be released from wastewater.
T or F - ANSWER-True
In order to control odors effectively, the operator should know where odors
originate and the cause.
T or F - ANSWER-True
Chlorination is one of the oldest and least effective methods of controlling odors.
T or F - ANSWER-False- it is one of the oldest & most effective
The reaction of chlorine with certain chemicals can cause a more odorous gas.
T or F - ANSWER-True
Decreasing the pH of wastewater is an effective odor control method for hydrogen
sulfide.
T or F - ANSWER-False- Increasing is an effective method
3
, Odor control towers must have a biomass established on the filter media in order to
remove odors.
T or F - ANSWER-True
The hazard classification of the spent carbon from odor control must be established
when considering disposal.
T or F - ANSWER-True
Regeneration of activated carbon temporarily eliminates any concerns about
hazardous waste disposal.
T or F - ANSWER-True
What is the most common source of sulfide in wastewater? - ANSWER-
Biological activity in the collection sewer or treatment plant
Why is the temperature of the wastewater system an important factor in the
production of hydrogen sulfide gas? - ANSWER-The rate of bacterial metabolism
is related to temperature
Why does ozone have limited use in controlling odors? - ANSWER-Because an
effective concentration may be too costly to use at large treatment plants
What is the problem with using combustion to remove odors from wastewater
treatment plant gases? - ANSWER-The combustibility of the gases is so low that
fuel costs are high
How can cathode scale be removed from an electrolytic chemical scrubber unit? -
ANSWER-Flush the system with dilute nitric acid
4
of 300 Textbook Questions and Correct Answers/ Class B
Wastewater Operator Exam 2026-2027 A Review of
Correctly Answered Exam Questions
What can an operator expect of an activated sludge that has excessive filamentous
organisms? - ANSWER-poor settling
What is an advantage of pure oxygen activated sludge systems over air activated
sludge systems? - ANSWER-they use smaller aeration (reactor) tanks
What is the function of the activated sludge process? - ANSWER-to remove
suspended and dissolved solids
What is the main cause of most odors in wastewater systems? - ANSWER-
Hydrogen sulfide
Hydrogen sulfide gas combines with moisture to form sulfuric acid, which is very
corrosive.
T or F - ANSWER-True
Which factor causes increased odor and corrosion problems in wastewater
treatment plants? - ANSWER-Increased travel times for wastewater to reach
treatment plants
1
,What is the principle source of odor generation in wastewater collection systems
and treatment processes? - ANSWER-Production of inorganic and organic gases
by microorganisms
Under what conditions should the reactor vent gas purity valve be "fine tuned"? -
ANSWER-when there is a drastic change in either the quantity or strength of the
wastewater entering the plant
When establishing an industrial waste monitoring program, what is one of the first
tasks? - ANSWER-an examination of the wastewater characteristics of each
industry that discharges to the collection system.
What is the purpose of the Respiration Rate for activated sludge test? To give some
insight into the - ANSWER-health of the microorganisms in the activated sludge
what does the BOD test measure? - ANSWER-the rate of oxygen uptake from the
wastewater by microorganisms in biochemical reactions
what are the major nutrients of concern in the activated sludge process? -
ANSWER-nitrogen and phosphorus
how can more nitrogen be added to industrial wastewater? more nitrogen can be
added in the form of - ANSWER-ammonia
how can more phosphorus be added to industrial wastewater? more phosphorus can
be added in the form of - ANSWER-phosphoric acid
liquid-solids separation is essential for successful biological process control
T or F - ANSWER-true
2
,enhanced biological treatment system flexibility is achieved by installing a large
number of treatment processes
T or F - ANSWER-false
If wastewater contains dissolved oxygen, the biological breakdown will reduce
sulfate to sulfide.
T or F - ANSWER-False
At a pH below 5, all sulfide is present in the gaseous h2s form and most of it can
be released from wastewater.
T or F - ANSWER-True
In order to control odors effectively, the operator should know where odors
originate and the cause.
T or F - ANSWER-True
Chlorination is one of the oldest and least effective methods of controlling odors.
T or F - ANSWER-False- it is one of the oldest & most effective
The reaction of chlorine with certain chemicals can cause a more odorous gas.
T or F - ANSWER-True
Decreasing the pH of wastewater is an effective odor control method for hydrogen
sulfide.
T or F - ANSWER-False- Increasing is an effective method
3
, Odor control towers must have a biomass established on the filter media in order to
remove odors.
T or F - ANSWER-True
The hazard classification of the spent carbon from odor control must be established
when considering disposal.
T or F - ANSWER-True
Regeneration of activated carbon temporarily eliminates any concerns about
hazardous waste disposal.
T or F - ANSWER-True
What is the most common source of sulfide in wastewater? - ANSWER-
Biological activity in the collection sewer or treatment plant
Why is the temperature of the wastewater system an important factor in the
production of hydrogen sulfide gas? - ANSWER-The rate of bacterial metabolism
is related to temperature
Why does ozone have limited use in controlling odors? - ANSWER-Because an
effective concentration may be too costly to use at large treatment plants
What is the problem with using combustion to remove odors from wastewater
treatment plant gases? - ANSWER-The combustibility of the gases is so low that
fuel costs are high
How can cathode scale be removed from an electrolytic chemical scrubber unit? -
ANSWER-Flush the system with dilute nitric acid
4
