Wastewater D License Exam 2026
Questions and Answers
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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, 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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
Questions and Answers
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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
,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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
, 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
©COPYRIGHT 2025, ALL RIGHTS RESERVED 4
