Wastewater D License Exam (2026/2027) Questions
and Verified Answers, 100% Guarantee Pass
How many PPB equals one PPM? - CORRECT ANSWER -One thousand parts per billion equals
one part per million
If the bubbler system air supply line at the wet well is clogged, what will this cause the pump to
do? - CORRECT ANSWER -Pressure build up in the supply line would signal more water
column then there really was, causing the pump to run longer than necessary, possibly not kick
off and run continually
If the bubbler system air supply line at the wet well has a hole in it above the water level, what
will this cause the pump to do? - CORRECT ANSWER -It would cause a low pressure reading
showing a lower water level then there really is, or possible not even kicking on the pump
What is the best way to keep within the operating budget? - CORRECT ANSWER -keep list of
purchases and expenses to date during fiscal year
comparisons should be made with budget allocations to avoid excess purchases
review purchases monthly and compare to budget
If a diaphragm pump has 2 check valves open, what will the pump do? - CORRECT ANSWER -
It would not pump properly because 1 check valve should be shut while the other is open
A suction lift pump on the inlet side normally reads 2in of mercury on the psi vacuum gauge but
not reads 3in of mercury. What is the problem with the pump? - CORRECT ANSWER -A higher
vacuum than normal may indicate a partially plugged or restricted suction line.
A lower vacuum may indicate a higher wet well level or a worn pump impeller or wearing rings.
,One mg per L equals how many pounds per 1 MG? - CORRECT ANSWER -8.34
What is the proper way to put packing in a pump? - CORRECT ANSWER -cut the packing rope
about 45 degree angle, place around shaft, be sure to offset/stagger the next joint from the
previous
How many drips of water should you have coming out of a packing seal? - CORRECT
ANSWER -no drip on a mechanical seal
How many drips of water should you have coming out of a packing seal? 2 - CORRECT
ANSWER -what the operation and maintenance manual recommends
A one horsepower motor that runs on 110 volts using 10 amps has what efficiency? - CORRECT
ANSWER -most motors run from 80-95% efficiency
A motor that has 440 volt supply is usually what phase of power? - CORRECT ANSWER -3
phase
NPDES - CORRECT ANSWER -National Pollutant Discharge Elimination System
the regulatory agency document issued by either a federal or state agency which is designed to
control all discharges of pollutants from point sources into US waterways - CORRECT
ANSWER -NPDES permit
What is the name of our operating permit? - CORRECT ANSWER -NPDES
What is the best way to promote safety in the workplace? - CORRECT ANSWER -the
supervisor needs to be safe and promote safety in such a manner to get the employees involved
,What is normally used to raise the pH in sludge? - CORRECT ANSWER -lime
What is the common device used to measure the effluent of a lagoon? - CORRECT ANSWER -v
notch weir
What concentration of H2S is unsafe to humans? - CORRECT ANSWER -death in a few
minutes at 0.2%. Paralyzes respiratory center
What is the minimum O2 concentration that is safe for workers to enter a manhole? - CORRECT
ANSWER -If O2 is less than 19.5%, do not enter space without respiratory protection. Normal
air contains 20.93% of O2.
Normal air contains ______% of O2 - CORRECT ANSWER -19.5%
What knob is turned to control the usage of chlorine applied? - CORRECT ANSWER -rotameter
Can you store BOD at 4C for 48 hours? - CORRECT ANSWER -yes
What is the minimum velocity of the water flow for a grit chamber and the maximum flow? -
CORRECT ANSWER -1.0 feet per second minimum
1.5 feet per second optimum
2.0 feet per second maximum
How many mg/L equals one grain per gallon? - CORRECT ANSWER -17.1 mg/L
Dissolved oxygen increases when the temperature __________ - CORRECT ANSWER -
decreases
, You can tell if a clarifier scraper arm is working by what means? - CORRECT ANSWER -the
simplest is to visual check to see if the scum scraper arm is moving properly
check into foam
If the sludge is thick or thin, then what does this tell you about the sludge scraper? - CORRECT
ANSWER -possible answer is the flights are damaged or the speed of the scrapers(flights) need
to be increased if sludge is too thick
or slowed down if the sludge is too thin
aging and maturing of a body of water - CORRECT ANSWER -eutrophication
eutrophication - CORRECT ANSWER -aging and maturing of a body of water
If the effluent from a treatment facility contained 5mg/L of BOD, what effect would this have on
the receiving stream? - CORRECT ANSWER -little effect
If you are doing a test and add one drop of chemical at a time, what is this method called? -
CORRECT ANSWER -titration
If doing a winkler or azide method after adding the first 2 chemicals and the contents of the
bottle turn white, what does this mean? - CORRECT ANSWER -no oxygen left in bottle, it has
all been consumed
How far from a well should a sewer main be? - CORRECT ANSWER -300 feet
a connection between a potable water system and a nonpotable water supply - CORRECT
ANSWER -cross connection
and Verified Answers, 100% Guarantee Pass
How many PPB equals one PPM? - CORRECT ANSWER -One thousand parts per billion equals
one part per million
If the bubbler system air supply line at the wet well is clogged, what will this cause the pump to
do? - CORRECT ANSWER -Pressure build up in the supply line would signal more water
column then there really was, causing the pump to run longer than necessary, possibly not kick
off and run continually
If the bubbler system air supply line at the wet well has a hole in it above the water level, what
will this cause the pump to do? - CORRECT ANSWER -It would cause a low pressure reading
showing a lower water level then there really is, or possible not even kicking on the pump
What is the best way to keep within the operating budget? - CORRECT ANSWER -keep list of
purchases and expenses to date during fiscal year
comparisons should be made with budget allocations to avoid excess purchases
review purchases monthly and compare to budget
If a diaphragm pump has 2 check valves open, what will the pump do? - CORRECT ANSWER -
It would not pump properly because 1 check valve should be shut while the other is open
A suction lift pump on the inlet side normally reads 2in of mercury on the psi vacuum gauge but
not reads 3in of mercury. What is the problem with the pump? - CORRECT ANSWER -A higher
vacuum than normal may indicate a partially plugged or restricted suction line.
A lower vacuum may indicate a higher wet well level or a worn pump impeller or wearing rings.
,One mg per L equals how many pounds per 1 MG? - CORRECT ANSWER -8.34
What is the proper way to put packing in a pump? - CORRECT ANSWER -cut the packing rope
about 45 degree angle, place around shaft, be sure to offset/stagger the next joint from the
previous
How many drips of water should you have coming out of a packing seal? - CORRECT
ANSWER -no drip on a mechanical seal
How many drips of water should you have coming out of a packing seal? 2 - CORRECT
ANSWER -what the operation and maintenance manual recommends
A one horsepower motor that runs on 110 volts using 10 amps has what efficiency? - CORRECT
ANSWER -most motors run from 80-95% efficiency
A motor that has 440 volt supply is usually what phase of power? - CORRECT ANSWER -3
phase
NPDES - CORRECT ANSWER -National Pollutant Discharge Elimination System
the regulatory agency document issued by either a federal or state agency which is designed to
control all discharges of pollutants from point sources into US waterways - CORRECT
ANSWER -NPDES permit
What is the name of our operating permit? - CORRECT ANSWER -NPDES
What is the best way to promote safety in the workplace? - CORRECT ANSWER -the
supervisor needs to be safe and promote safety in such a manner to get the employees involved
,What is normally used to raise the pH in sludge? - CORRECT ANSWER -lime
What is the common device used to measure the effluent of a lagoon? - CORRECT ANSWER -v
notch weir
What concentration of H2S is unsafe to humans? - CORRECT ANSWER -death in a few
minutes at 0.2%. Paralyzes respiratory center
What is the minimum O2 concentration that is safe for workers to enter a manhole? - CORRECT
ANSWER -If O2 is less than 19.5%, do not enter space without respiratory protection. Normal
air contains 20.93% of O2.
Normal air contains ______% of O2 - CORRECT ANSWER -19.5%
What knob is turned to control the usage of chlorine applied? - CORRECT ANSWER -rotameter
Can you store BOD at 4C for 48 hours? - CORRECT ANSWER -yes
What is the minimum velocity of the water flow for a grit chamber and the maximum flow? -
CORRECT ANSWER -1.0 feet per second minimum
1.5 feet per second optimum
2.0 feet per second maximum
How many mg/L equals one grain per gallon? - CORRECT ANSWER -17.1 mg/L
Dissolved oxygen increases when the temperature __________ - CORRECT ANSWER -
decreases
, You can tell if a clarifier scraper arm is working by what means? - CORRECT ANSWER -the
simplest is to visual check to see if the scum scraper arm is moving properly
check into foam
If the sludge is thick or thin, then what does this tell you about the sludge scraper? - CORRECT
ANSWER -possible answer is the flights are damaged or the speed of the scrapers(flights) need
to be increased if sludge is too thick
or slowed down if the sludge is too thin
aging and maturing of a body of water - CORRECT ANSWER -eutrophication
eutrophication - CORRECT ANSWER -aging and maturing of a body of water
If the effluent from a treatment facility contained 5mg/L of BOD, what effect would this have on
the receiving stream? - CORRECT ANSWER -little effect
If you are doing a test and add one drop of chemical at a time, what is this method called? -
CORRECT ANSWER -titration
If doing a winkler or azide method after adding the first 2 chemicals and the contents of the
bottle turn white, what does this mean? - CORRECT ANSWER -no oxygen left in bottle, it has
all been consumed
How far from a well should a sewer main be? - CORRECT ANSWER -300 feet
a connection between a potable water system and a nonpotable water supply - CORRECT
ANSWER -cross connection
