MA Municipal Wastewater Treatment
Plant Operators Exam. Latest 2026-
2027. Questions & Correct Verified
Answers. Graded A
____________________________ can provide
a high-quality effuent that is acceptable for
discharge into many receiving waters. - ANSLagoons in series with each
other
______________, ______________, and
________________ are three pieces of personal
protective equipment. - ANSHard hats, safety shoes, chemical-resistant
clothing, gloves, toe guards, safety glasses or goggles
A 2 percent sodium hypochlorite solution is
stored in a 4-foot-diameter plastic tank. During
a 1-week period, the water meter indicated that
3,489,000 gallons of water were treated and the
level of hypochlorite in the tank dropped 2 feet
8 inches (2.67 feet). What is the estimated chlorine dose in milligrams per
liter? - ANS1.44mg/L
A chlorinator is set to feed 48 pounds of chlorine
1
,per 24 hours; the wastewater flow is at a rate
of 1.2 million gallons per day; and the chlorine
as measured by the chlorine residual test after
30 minutes of contact time is 0.5 milligrams per
liter (mg/L). Find the chlorine demand in mg/L. - ANSCl dose = 0.12 x
(48/1.2) = 4.8 mg/L
Cl demand = 4.8 - 0.5
= 4.3 mg/L
A circular clarifier with a diameter of 50 feet and
a depth of 10 feet treats a flow of 2 MGD. What
is the detention time in hours? - ANSDetention time = Volume / Flow
Volume = (0.785)(50^2)(10) = 19,625ft^3
Volume (gal) = 19,625 x 7.48 = 146,795gal
Detention time (hours) = 146,795gal / (2,000,000gpd/24hrs)
= 1.8 hrs
A plant with a flow of 4 million gallons per day
has an effluent chlorine residual of 3.2 milli-grams per liter. Sulfur dioxide is
being applied
at 1.0 mg/L more than the chlorine residual.
Determine the sulfonator feed rate in pounds of
sulfur dioxide per day. - ANS140 lb/d
A propeller-type velocity meter is turned by
water flowing past propeller vanes that move
_______. - ANSgear trains
2
,A tapered aeration ASP has the advantages of
_____________________, ____________________,
and can be used to _________________ inside the
aeration tank by reducing the oxygen level in
the tail end of the tank. - ANSreducing power costs, providing operational
flexibility, avoid nitrification
A waste treatment pond treats a flow of 0.1 MGD
with a BOD of 180 mg/L. The area of the pond
is 3 acres. What is the organic (BOD) loading on
the pond in pounds of BOD per acre per day? - ANSOLR = Flow rate x
BOD Concentration / Surface Area of Lagoon
OLR = 0.1 x 180 x 8.34 L*lb/Mgal*mg / 3
OLR = 50 lb/ac /d
Abnormal operation of the fne bubble diffusers
is usually the result of the ______________ due
to dirt and biological growths. Abnormal operation of the coarse bubble
diffusers is usually
the result of clogging due to __________ or
__________. - ANSporous surfaces clogging, biological growth, broken
diffusers
An _________________ is a suspended growth
system, and a ________________ provides a
structure to which the microorganisms attach (or
3
, become fxed) that then comes in contact with
the wastewater and oxygen. - ANSActivate sludge process, fixed film
process
An ideal media will have a large ____________,
a high ____________, and a ____________ in
addition to being ___________ and relatively
______________. - ANSsurface area, void ratio, light weight, durable,
inexpensive
An operator must maintain a higher level
of biomass (MLSS) in _______ weather than in
_______ weather to treat the same amount of
BOD. - ANSColder, warmer
Any operational problem leading to poor performance with the ASP is
typically the result of
__________, water quality, equipment malfunctions, ___________,
___________, environmental
changes, and _____________. - ANShydraulics, plant changes, process
controls, design deficiencies
Approximately how many pounds (1b) are in
2 kilograms (kg)? - ANS5lb
1lb = 0.454kg
As water temperature increases, the settling rate
4
Plant Operators Exam. Latest 2026-
2027. Questions & Correct Verified
Answers. Graded A
____________________________ can provide
a high-quality effuent that is acceptable for
discharge into many receiving waters. - ANSLagoons in series with each
other
______________, ______________, and
________________ are three pieces of personal
protective equipment. - ANSHard hats, safety shoes, chemical-resistant
clothing, gloves, toe guards, safety glasses or goggles
A 2 percent sodium hypochlorite solution is
stored in a 4-foot-diameter plastic tank. During
a 1-week period, the water meter indicated that
3,489,000 gallons of water were treated and the
level of hypochlorite in the tank dropped 2 feet
8 inches (2.67 feet). What is the estimated chlorine dose in milligrams per
liter? - ANS1.44mg/L
A chlorinator is set to feed 48 pounds of chlorine
1
,per 24 hours; the wastewater flow is at a rate
of 1.2 million gallons per day; and the chlorine
as measured by the chlorine residual test after
30 minutes of contact time is 0.5 milligrams per
liter (mg/L). Find the chlorine demand in mg/L. - ANSCl dose = 0.12 x
(48/1.2) = 4.8 mg/L
Cl demand = 4.8 - 0.5
= 4.3 mg/L
A circular clarifier with a diameter of 50 feet and
a depth of 10 feet treats a flow of 2 MGD. What
is the detention time in hours? - ANSDetention time = Volume / Flow
Volume = (0.785)(50^2)(10) = 19,625ft^3
Volume (gal) = 19,625 x 7.48 = 146,795gal
Detention time (hours) = 146,795gal / (2,000,000gpd/24hrs)
= 1.8 hrs
A plant with a flow of 4 million gallons per day
has an effluent chlorine residual of 3.2 milli-grams per liter. Sulfur dioxide is
being applied
at 1.0 mg/L more than the chlorine residual.
Determine the sulfonator feed rate in pounds of
sulfur dioxide per day. - ANS140 lb/d
A propeller-type velocity meter is turned by
water flowing past propeller vanes that move
_______. - ANSgear trains
2
,A tapered aeration ASP has the advantages of
_____________________, ____________________,
and can be used to _________________ inside the
aeration tank by reducing the oxygen level in
the tail end of the tank. - ANSreducing power costs, providing operational
flexibility, avoid nitrification
A waste treatment pond treats a flow of 0.1 MGD
with a BOD of 180 mg/L. The area of the pond
is 3 acres. What is the organic (BOD) loading on
the pond in pounds of BOD per acre per day? - ANSOLR = Flow rate x
BOD Concentration / Surface Area of Lagoon
OLR = 0.1 x 180 x 8.34 L*lb/Mgal*mg / 3
OLR = 50 lb/ac /d
Abnormal operation of the fne bubble diffusers
is usually the result of the ______________ due
to dirt and biological growths. Abnormal operation of the coarse bubble
diffusers is usually
the result of clogging due to __________ or
__________. - ANSporous surfaces clogging, biological growth, broken
diffusers
An _________________ is a suspended growth
system, and a ________________ provides a
structure to which the microorganisms attach (or
3
, become fxed) that then comes in contact with
the wastewater and oxygen. - ANSActivate sludge process, fixed film
process
An ideal media will have a large ____________,
a high ____________, and a ____________ in
addition to being ___________ and relatively
______________. - ANSsurface area, void ratio, light weight, durable,
inexpensive
An operator must maintain a higher level
of biomass (MLSS) in _______ weather than in
_______ weather to treat the same amount of
BOD. - ANSColder, warmer
Any operational problem leading to poor performance with the ASP is
typically the result of
__________, water quality, equipment malfunctions, ___________,
___________, environmental
changes, and _____________. - ANShydraulics, plant changes, process
controls, design deficiencies
Approximately how many pounds (1b) are in
2 kilograms (kg)? - ANS5lb
1lb = 0.454kg
As water temperature increases, the settling rate
4
