ABC Wastewater Level 3 – General questions
and answers 2025\2026
Turbidity in wastewater is caused by
A. color
B. dissolved calcium
C. hardness
D. finely divided suspended material correct answer D. finely divided suspended
material
The gas most commonly associated with septic wastewater is
A. carbon dioxide
B. carbon monoxide
C. hydrogen sulfide
D. methane correct answer C. hydrogen sulfide
How many cubic meters per second in 10 MGD?
A. 0.44
B. 1.44
C. 4.73
D. 24.62 correct answer A. 0.44
Mechanical ventilation of a lift station is required to
A. lower temperatures to reduce proportion of hydrogen sulfide
B. reduce chlorine demand
C. reduce corrosion
,D. increase DO in raw wastewater correct answer C. reduce corrosion
A wet well probe is usually used for ________ determination(s) of level.
A. approximate
B. dual point
C. continuous
D. single point correct answer D. single point
A pump is delivering at less than the expected rate of discharge. Which of the
causes listed below is incorrect?
A. speed of motor too low
B. pump not primed
C. impeller clogged
D. discharge head too low correct answer D. discharge head too low
Metal pipes often fail because of
A. back siphonage
B. browning movement
C. galvanic action
D. reverse osmosis correct answer C. galvanic action
When a fire hydrant is operated, it should be
A. just opened enough to have a flow
B. opened fully
C. opened halfway
,D. regulated to flow required correct answer B. opened fully
If the pump bearings on horizontal centrifugal pumps are over lubricated, the
most important effect is that the extra lubricant
A. will result in smoother and more efficient operation of the pump
B. will not make any difference in the operation of the pump
C. will be wasted
D. shaft or shaft sleeve will be damaged correct answer D. shaft or shaft sleeve
will be damaged
If packing is not maintained properly,
A. cavitation damage will result
B. impeller will corrode
C. loss of suction due to air being allowed to enter pump
D. shaft or shaft sleeve will be damaged correct answer C. loss of suction due to
air being allowed to enter pump
Air flow through a trickling filter when the influent is warmer than the air
temperature is
A. upward through the filter
B. downward through the filter
C. inadequate and may require forced air ventilation
D. improved by decreasing the recirculation correct answer A. upward through
the filter
, An active sludge in the aeration tank with an abundant available food supply will
have a relatively
A. high oxygen uptake and fast settling rate
B. high oxygen uptake and slow settling rate
C. low oxygen uptake and fast settling rate
D. low oxygen uptake and slow settling rate correct answer B. high oxygen uptake
and slow settling rate
The reaction of chlorine and ammonia produces a compound which is called
A. ammonium chloride
B. chloral hydrate
C. chloramine
D. hydrazine correct answer C. chloramine
A malfunctioning gas chlorination system has normal gas pressure, no feed rate
indicated on rotometer, and no injector vacuum. What is the most likely cause of
the
problem?
A. air leak upstream of rotameter
B. gas line plugged
C. injector clogged
D. pressure reducing valve diaphragm ruptured correct answer C. injector
clogged
What is the impact of increased viscosity on the effectiveness of mixed media
filters?
and answers 2025\2026
Turbidity in wastewater is caused by
A. color
B. dissolved calcium
C. hardness
D. finely divided suspended material correct answer D. finely divided suspended
material
The gas most commonly associated with septic wastewater is
A. carbon dioxide
B. carbon monoxide
C. hydrogen sulfide
D. methane correct answer C. hydrogen sulfide
How many cubic meters per second in 10 MGD?
A. 0.44
B. 1.44
C. 4.73
D. 24.62 correct answer A. 0.44
Mechanical ventilation of a lift station is required to
A. lower temperatures to reduce proportion of hydrogen sulfide
B. reduce chlorine demand
C. reduce corrosion
,D. increase DO in raw wastewater correct answer C. reduce corrosion
A wet well probe is usually used for ________ determination(s) of level.
A. approximate
B. dual point
C. continuous
D. single point correct answer D. single point
A pump is delivering at less than the expected rate of discharge. Which of the
causes listed below is incorrect?
A. speed of motor too low
B. pump not primed
C. impeller clogged
D. discharge head too low correct answer D. discharge head too low
Metal pipes often fail because of
A. back siphonage
B. browning movement
C. galvanic action
D. reverse osmosis correct answer C. galvanic action
When a fire hydrant is operated, it should be
A. just opened enough to have a flow
B. opened fully
C. opened halfway
,D. regulated to flow required correct answer B. opened fully
If the pump bearings on horizontal centrifugal pumps are over lubricated, the
most important effect is that the extra lubricant
A. will result in smoother and more efficient operation of the pump
B. will not make any difference in the operation of the pump
C. will be wasted
D. shaft or shaft sleeve will be damaged correct answer D. shaft or shaft sleeve
will be damaged
If packing is not maintained properly,
A. cavitation damage will result
B. impeller will corrode
C. loss of suction due to air being allowed to enter pump
D. shaft or shaft sleeve will be damaged correct answer C. loss of suction due to
air being allowed to enter pump
Air flow through a trickling filter when the influent is warmer than the air
temperature is
A. upward through the filter
B. downward through the filter
C. inadequate and may require forced air ventilation
D. improved by decreasing the recirculation correct answer A. upward through
the filter
, An active sludge in the aeration tank with an abundant available food supply will
have a relatively
A. high oxygen uptake and fast settling rate
B. high oxygen uptake and slow settling rate
C. low oxygen uptake and fast settling rate
D. low oxygen uptake and slow settling rate correct answer B. high oxygen uptake
and slow settling rate
The reaction of chlorine and ammonia produces a compound which is called
A. ammonium chloride
B. chloral hydrate
C. chloramine
D. hydrazine correct answer C. chloramine
A malfunctioning gas chlorination system has normal gas pressure, no feed rate
indicated on rotometer, and no injector vacuum. What is the most likely cause of
the
problem?
A. air leak upstream of rotameter
B. gas line plugged
C. injector clogged
D. pressure reducing valve diaphragm ruptured correct answer C. injector
clogged
What is the impact of increased viscosity on the effectiveness of mixed media
filters?
