MISSOURI CLASS D WASTEWATER EXAM 150
QUESTIONS & CORRECT ANSWERS LATEST
2026/2027
Septic sewage contains considerable free oxygen but is being digested by
anaerobic bacteria. - True/False - ANSWER-FALSE
All settleable solids in sewage may be also considered as suspended solids but all
suspended solids are not necessarily settleable solids. -True/False - ANSWER-
TRUE
Bacteria which requires free oxygen are called anaerobic. -True/False - ANSWER-
FALSE
It is a good operating practice to discharge wet sludge from the digester onto
already dried sludge so it can all be removed together. - True/False - ANSWER-
FALSE
The purpose of primary clarification of sewage is to remove the settleable solids by
settling. - True/False - ANSWER-TRUE
Sodium or ammonium nitrate may be used to control septic conditions in a lagoon.
- True/False - ANSWER-TRUE
,One mg/l is for all intent and purposes equal to one ppm. -True/False - ANSWER-
TRUE
A parshall flume is a device made by Parshall for measuring the flow of liquid in
an open conduit. - True/False - ANSWER-TRUE
If properly designed and operated, a waste stabilization lagoon is considered a
complete sewage treatment plant. - True/False - ANSWER-TRUE
The amount of oxygen that can be dissolved in water decreases as the temperature
of the water increases. -True/False - ANSWER-TRUE
The three lab control tests normally used to operate a lagoon are PH, Alkalinity,
and D.O. -True/False - ANSWER-TRUE
The water depth in a sewage lagoon is kept as shallow as possible to allow the
sun's energy to reach the algae. -True/False - ANSWER-FALSE
The purpose of sludge beds is to remove the moisture from the sludge so that it
may be easily handled for removal. -True/False - ANSWER-TRUE
Raw sludge should be added slowly at regular intervals to digesters. -True/False -
ANSWER-TRUE
Chlorine gas is heavier than air. -True/False - ANSWER-TRUE
The fertilizer value of digested sludge is high when compared to commercial
fertilizer. -True/False - ANSWER-FALSE
, Trickling filters depend on the principle of straining out the organic matter. -
True/False - ANSWER-FALSE
Both aerobic and anaerobic bacterial reactions may occur in a sewage lagoon. -
True/False - ANSWER-TRUE
Activated sludge is one of the most efficient types of sewage treatment and is non-
sensitive to loading or type of sewage being treated. -True/False - ANSWER-
TRUE
A centrifugal pump works equally well at both low and high heads. -True/False -
ANSWER-FALSE
A three-phase induction motor will have its direction or rotation reversed if any
two line leads are interchanged. -True/False - ANSWER-TRUE
Squirrel-cage motors have a high starting torque. -True/False - ANSWER-TRUE
Pneumatic ejectors are designed to lift liquids and solids in suspension by means of
compressed air. -True/False - ANSWER-TRUE
Any stream will purify itself in three miles. -True/False - ANSWER-FALSE
Backfill material on sewer lines should be selected material. -True/False -
ANSWER-TRUE
QUESTIONS & CORRECT ANSWERS LATEST
2026/2027
Septic sewage contains considerable free oxygen but is being digested by
anaerobic bacteria. - True/False - ANSWER-FALSE
All settleable solids in sewage may be also considered as suspended solids but all
suspended solids are not necessarily settleable solids. -True/False - ANSWER-
TRUE
Bacteria which requires free oxygen are called anaerobic. -True/False - ANSWER-
FALSE
It is a good operating practice to discharge wet sludge from the digester onto
already dried sludge so it can all be removed together. - True/False - ANSWER-
FALSE
The purpose of primary clarification of sewage is to remove the settleable solids by
settling. - True/False - ANSWER-TRUE
Sodium or ammonium nitrate may be used to control septic conditions in a lagoon.
- True/False - ANSWER-TRUE
,One mg/l is for all intent and purposes equal to one ppm. -True/False - ANSWER-
TRUE
A parshall flume is a device made by Parshall for measuring the flow of liquid in
an open conduit. - True/False - ANSWER-TRUE
If properly designed and operated, a waste stabilization lagoon is considered a
complete sewage treatment plant. - True/False - ANSWER-TRUE
The amount of oxygen that can be dissolved in water decreases as the temperature
of the water increases. -True/False - ANSWER-TRUE
The three lab control tests normally used to operate a lagoon are PH, Alkalinity,
and D.O. -True/False - ANSWER-TRUE
The water depth in a sewage lagoon is kept as shallow as possible to allow the
sun's energy to reach the algae. -True/False - ANSWER-FALSE
The purpose of sludge beds is to remove the moisture from the sludge so that it
may be easily handled for removal. -True/False - ANSWER-TRUE
Raw sludge should be added slowly at regular intervals to digesters. -True/False -
ANSWER-TRUE
Chlorine gas is heavier than air. -True/False - ANSWER-TRUE
The fertilizer value of digested sludge is high when compared to commercial
fertilizer. -True/False - ANSWER-FALSE
, Trickling filters depend on the principle of straining out the organic matter. -
True/False - ANSWER-FALSE
Both aerobic and anaerobic bacterial reactions may occur in a sewage lagoon. -
True/False - ANSWER-TRUE
Activated sludge is one of the most efficient types of sewage treatment and is non-
sensitive to loading or type of sewage being treated. -True/False - ANSWER-
TRUE
A centrifugal pump works equally well at both low and high heads. -True/False -
ANSWER-FALSE
A three-phase induction motor will have its direction or rotation reversed if any
two line leads are interchanged. -True/False - ANSWER-TRUE
Squirrel-cage motors have a high starting torque. -True/False - ANSWER-TRUE
Pneumatic ejectors are designed to lift liquids and solids in suspension by means of
compressed air. -True/False - ANSWER-TRUE
Any stream will purify itself in three miles. -True/False - ANSWER-FALSE
Backfill material on sewer lines should be selected material. -True/False -
ANSWER-TRUE
