MAINE (ME) PLANT OPERATOR AUTHORITY | VERIFIED
EXAM QUESTIONS AND ANSWERS - LATEST VERSION
2026/2027
Maine (ME) Plant Operator Authority
1. Q: What is the primary purpose of a water treatment plant?
ANSWER To produce water that is safe to drink (potable) and
aesthetically pleasing.
2. Q: What is the primary purpose of a wastewater treatment plant?
ANSWER To remove pollutants from wastewater before it is
discharged into the environment.
3. Q: What does OSHA stand for? ANSWER Occupational Safety and
Health Administration.
4. Q: What does MSDS stand for? ANSWER Material Safety Data Sheet
(now SDS - Safety Data Sheet).
5. Q: What is the IDLH atmosphere regarding chlorine? ANSWER
Immediately Dangerous to Life or Health.
6. Q: What is the first step in a Confined Space Entry? ANSWER Isolate
the space (Lockout/Tagout) and test the atmosphere.
7. Q: What does LOTO stand for? ANSWER Lockout/Tagout.
8. Q: What is the minimum oxygen level required for entry into a
confined space? ANSWER 19.5%.
9. Q: What is the maximum safe oxygen level in a confined space?
ANSWER 23.5%.
,10. Q: What type of fire extinguisher is used for electrical fires?
ANSWER Class C.
11. Q: What is the specific gravity of water? ANSWER 1.0.
12. Q: What is pH? ANSWER A measure of the acidity or
alkalinity of water (0-14 scale).
13. Q: What is a neutral pH? ANSWER 7.0.
14. Q: What is an NPDES permit? ANSWER National Pollutant
Discharge Elimination System permit.
15. Q: What agency oversees drinking water regulations in Maine?
ANSWER Maine Drinking Water Program (MEDEP).
16. Q: What is the "Right-to-Know" law? ANSWER A law granting
workers access to information about hazardous chemicals in their
workplace.
17. Q: What is a turbidity nephelometric unit (NTU)? ANSWER A
unit of measurement for water cloudiness.
18. Q: What is the purpose of a flash mixer? ANSWER To rapidly
mix coagulants with water.
19. Q: What is flocculation? ANSWER The gentle mixing of water
to allow particles to clump together (floc).
20. Q: What is sedimentation? ANSWER The process of settling
out suspended solids by gravity.
21. Q: What is the difference between screening and grit removal?
ANSWER Screening removes large debris (rags, sticks); grit removal
removes heavy inorganic solids (sand, gravel).
22. Q: What is BOD? ANSWER Biochemical Oxygen Demand (the
amount of oxygen used by bacteria).
23. Q: What is COD? ANSWER Chemical Oxygen Demand.
24. Q: What is TSS? ANSWER Total Suspended Solids.
25. Q: What is the most common disinfectant used in water
treatment? ANSWER Chlorine.
26. Q: What is a backflow preventer? ANSWER A device that
prevents water from flowing backward into the distribution system.
, 27. Q: What is a cross-connection? ANSWER A link between a
potable water system and a non-potable source.
28. Q: What is SCADA? ANSWER Supervisory Control and Data
Acquisition.
29. Q: What is the purpose of a clear well? ANSWER To store
finished water and provide contact time for disinfection.
30. Q: What is head loss? ANSWER The loss of pressure as water
flows through a pipe or filter due to friction.
31. Q: What is hydraulic head? ANSWER The height of a fluid
column; the energy possessed by a fluid due to its elevation.
32. Q: What is potable water? ANSWER Water safe for human
consumption.
33. Q: What is an influent? ANSWER Water/wastewater entering
a plant or tank.
34. Q: What is an effluent? ANSWER Water/wastewater leaving a
plant or tank.
35. Q: What is a weir? ANSWER A notch or overflow structure
used to measure flow.
36. Q: What is a Parshall Flume? ANSWER a device used to
measure flow in an open channel.
37. Q: What is the purpose of a bar screen? ANSWER To remove
large floating objects from wastewater.
38. Q: What is grit composed of? ANSWER Sand, gravel, cinders,
and other heavy inorganic material.
39. Q: What is activated sludge? ANSWER A biological process
using aerated sewage containing microorganisms to treat
wastewater.
40. Q: What is Return Activated Sludge (RAS)? ANSWER Settled
sludge returned from the secondary clarifier to the aeration tank to
maintain biomass.
41. Q: What is Waste Activated Sludge (WAS)? ANSWER Excess
sludge removed from the system to control the population of
microorganisms.
EXAM QUESTIONS AND ANSWERS - LATEST VERSION
2026/2027
Maine (ME) Plant Operator Authority
1. Q: What is the primary purpose of a water treatment plant?
ANSWER To produce water that is safe to drink (potable) and
aesthetically pleasing.
2. Q: What is the primary purpose of a wastewater treatment plant?
ANSWER To remove pollutants from wastewater before it is
discharged into the environment.
3. Q: What does OSHA stand for? ANSWER Occupational Safety and
Health Administration.
4. Q: What does MSDS stand for? ANSWER Material Safety Data Sheet
(now SDS - Safety Data Sheet).
5. Q: What is the IDLH atmosphere regarding chlorine? ANSWER
Immediately Dangerous to Life or Health.
6. Q: What is the first step in a Confined Space Entry? ANSWER Isolate
the space (Lockout/Tagout) and test the atmosphere.
7. Q: What does LOTO stand for? ANSWER Lockout/Tagout.
8. Q: What is the minimum oxygen level required for entry into a
confined space? ANSWER 19.5%.
9. Q: What is the maximum safe oxygen level in a confined space?
ANSWER 23.5%.
,10. Q: What type of fire extinguisher is used for electrical fires?
ANSWER Class C.
11. Q: What is the specific gravity of water? ANSWER 1.0.
12. Q: What is pH? ANSWER A measure of the acidity or
alkalinity of water (0-14 scale).
13. Q: What is a neutral pH? ANSWER 7.0.
14. Q: What is an NPDES permit? ANSWER National Pollutant
Discharge Elimination System permit.
15. Q: What agency oversees drinking water regulations in Maine?
ANSWER Maine Drinking Water Program (MEDEP).
16. Q: What is the "Right-to-Know" law? ANSWER A law granting
workers access to information about hazardous chemicals in their
workplace.
17. Q: What is a turbidity nephelometric unit (NTU)? ANSWER A
unit of measurement for water cloudiness.
18. Q: What is the purpose of a flash mixer? ANSWER To rapidly
mix coagulants with water.
19. Q: What is flocculation? ANSWER The gentle mixing of water
to allow particles to clump together (floc).
20. Q: What is sedimentation? ANSWER The process of settling
out suspended solids by gravity.
21. Q: What is the difference between screening and grit removal?
ANSWER Screening removes large debris (rags, sticks); grit removal
removes heavy inorganic solids (sand, gravel).
22. Q: What is BOD? ANSWER Biochemical Oxygen Demand (the
amount of oxygen used by bacteria).
23. Q: What is COD? ANSWER Chemical Oxygen Demand.
24. Q: What is TSS? ANSWER Total Suspended Solids.
25. Q: What is the most common disinfectant used in water
treatment? ANSWER Chlorine.
26. Q: What is a backflow preventer? ANSWER A device that
prevents water from flowing backward into the distribution system.
, 27. Q: What is a cross-connection? ANSWER A link between a
potable water system and a non-potable source.
28. Q: What is SCADA? ANSWER Supervisory Control and Data
Acquisition.
29. Q: What is the purpose of a clear well? ANSWER To store
finished water and provide contact time for disinfection.
30. Q: What is head loss? ANSWER The loss of pressure as water
flows through a pipe or filter due to friction.
31. Q: What is hydraulic head? ANSWER The height of a fluid
column; the energy possessed by a fluid due to its elevation.
32. Q: What is potable water? ANSWER Water safe for human
consumption.
33. Q: What is an influent? ANSWER Water/wastewater entering
a plant or tank.
34. Q: What is an effluent? ANSWER Water/wastewater leaving a
plant or tank.
35. Q: What is a weir? ANSWER A notch or overflow structure
used to measure flow.
36. Q: What is a Parshall Flume? ANSWER a device used to
measure flow in an open channel.
37. Q: What is the purpose of a bar screen? ANSWER To remove
large floating objects from wastewater.
38. Q: What is grit composed of? ANSWER Sand, gravel, cinders,
and other heavy inorganic material.
39. Q: What is activated sludge? ANSWER A biological process
using aerated sewage containing microorganisms to treat
wastewater.
40. Q: What is Return Activated Sludge (RAS)? ANSWER Settled
sludge returned from the secondary clarifier to the aeration tank to
maintain biomass.
41. Q: What is Waste Activated Sludge (WAS)? ANSWER Excess
sludge removed from the system to control the population of
microorganisms.
