AWWA WAter OperAtOr CertifiCAtiOn exAm prep ACtuAl exAm
neWest 2026 With COmplete QuestiOns And COrreCt detAiled
AnsWers| BrAnd neW VersiOn!
What is the most common disinfection by product when adding chlorine to water containing natural and
inorganic matter? - COrreCt AnsWer-Chloroform
What will most probably cause taste and odors, slime, and filter clogging? - COrreCt AnsWer-Blue-
green Algae
Why can rapid sand filters handle higher filtration rates compared to slow sand filters? - COrreCt
AnsWer-Coarser sand
Iron bacteria can interfere with ___________ because the bacteria produce _____________that prevents
the stabilization chemicals from reaching the pipe surface. - COrreCt AnsWer-stabilization, a slime
layer
Hypochlorous acid is favored over hypochlorite ion when the pH is _____________and the temperature is
___________. - COrreCt AnsWer-low, low
What filter has an unstratified media distribution? - COrreCt AnsWer-slow sand filters
What is (are) the combine chlorine residual(s) at pH values ranging from 6.5 to 8.5? - COrreCt
AnsWer-Monochloramine and dichloramine
When iron alone is treated using manganese greensand filters, the chlorine feed rate should be about
_________________. - COrreCt AnsWer-1.0 to 1.2 times the iron concentration
chlorination of water that has high concentrations of natural organic matter will produce - COrreCt
AnsWer-THMs
,When disinfecting with chloramines, when can the ammonia be added to the process? - COrreCt
AnsWer-Before, same time as, or after the chlorine
What will settle out of the water in a short period of time? - COrreCt AnsWer-Very fine silt
Point-of-use activated carbon filters are most effective for removing _________________. - COrreCt
AnsWer-Chlorine
Potassium permanganate is used as an oxidant for control of ____________________. - COrreCt
AnsWer-Iron and manganese, organic precursors, and taste and odors
What must an operator periodically check regarding the cyclone separator system? - COrreCt
AnsWer-Storage bin or hopper to empty of sand and grit
These types of chemicals chemically tie up scale-forming ions and are eventually ingested by consumers.
- COrreCt AnsWer-Sequestering agents
An operator should record filter ______________ measurements, condition, and depth of media on a
________ basis. - COrreCt AnsWer-bed expansion, quarterly
Lime will precipitate noncarbonate hardness from the water, but it also orms noncarbonate salts that
cause noncarbonate hardness. What are these salts? - COrreCt AnsWer-CaSO4 and CaCl2
What are absolute ratings based on with regard to membranes? - COrreCt AnsWer-Largest pore
opening
How ar manganese greensand beds regenerated? - COrreCt AnsWer-Backwashed with
permanganate solution
The most effective process for removing radon gas, when considering cost and footprint, would be
____________. - COrreCt AnsWer-packed tower aeration
,What is the primary advantage of placing a properly sized anthracite coal layer over manganese
greensand? - COrreCt AnsWer-Longer filter run times
What factor will cause problems for chlorination? - COrreCt AnsWer-Foreign substances
In the lime-soda ash softening process, smaller plants find that ________ is less expensive to purchase;
regardless of the size of the plant, ___________ needs to be mixed long enough because it dissolves
rather slowly. - COrreCt AnsWer-calcium hydroxide, lime
What does the optimal pH establish when applied to iron and manganese oxidation? - COrreCt
AnsWer-Detention time
A water plant using chloramines as a disinfectant has allowed sizable amounts of turbidity to enter the
distribution system. If this occurs over a period of years, what will occur at the far end of the distribution
system? - COrreCt AnsWer-Taste and odor will develop, Bacterial growth will be supported, and
Nitrification
The reduction of color would most likely occur after - COrreCt AnsWer-coagulation, flocculation, and
sedimentation
To eliminate hydrogen sulfide (H2S), the pH of the water should be lowered to ____________ or less
before beginning aeration. - COrreCt AnsWer-6.0
Permanganate reactions are largely dependent on ___________. - COrreCt AnsWer-pH
What are the primary reasons that more small water stems are installing pressure filters? - COrreCt
AnsWer-Because installation and operating costs are low
Because lime slurries have a _________ and a ___________ in water, calcium carbonate will
____________ on anything the slurry touches. - COrreCt AnsWer-high pH, low solubility, preciptate
It is recommended that the free chlorine residual at a customer's tap should be at least ________. -
COrreCt AnsWer-0.2 mg/L
, Microfiltration is considered to be intermediate between ___________ based on pore size. - COrreCt
AnsWer-ultrafiltration and multimedia granular filtration
After microscreening, there should be a significant reduction in ______________. - COrreCt AnsWer-
Turbidity
How can the problem of poorly formed floc be solved? - COrreCt AnsWer-Use of coagulant aid
What chemical used in corrosion control gives off large quantities of CO2 when it comes in contact with
an acid? - COrreCt AnsWer-Soda ash
Alum requires _____________ to be present naturally or added fro proper coagulation, and about
_____________ is required for each milligram of alum added per liter. - COrreCt AnsWer-alkalinity,
0.5 mg/L
A cloudy appearance in the last flocculation chamber is usually caused by ____________. - COrreCt
AnsWer-inadequate coagulant dosage
What type of meter is most commonly use for customer metering? - COrreCt AnsWer-Positive-
displacement meters
In general, the size of floc that has been found to be optimal for settling efficiency is
____________________. - COrreCt AnsWer-pinhead-size floc
In a pulsator clarifier, what is the purpose of the pulses and how often are pulses generated? - COrreCt
AnsWer-To maintain a uniform sludge layer; 40-50 sec
UV application will - COrreCt AnsWer-inhibit bacterial growth and replication
Calcium hypochlorite used in water treatment disinfection ranges in percentage strength of available
chlorine from _______________. - COrreCt AnsWer-65% to 70%
neWest 2026 With COmplete QuestiOns And COrreCt detAiled
AnsWers| BrAnd neW VersiOn!
What is the most common disinfection by product when adding chlorine to water containing natural and
inorganic matter? - COrreCt AnsWer-Chloroform
What will most probably cause taste and odors, slime, and filter clogging? - COrreCt AnsWer-Blue-
green Algae
Why can rapid sand filters handle higher filtration rates compared to slow sand filters? - COrreCt
AnsWer-Coarser sand
Iron bacteria can interfere with ___________ because the bacteria produce _____________that prevents
the stabilization chemicals from reaching the pipe surface. - COrreCt AnsWer-stabilization, a slime
layer
Hypochlorous acid is favored over hypochlorite ion when the pH is _____________and the temperature is
___________. - COrreCt AnsWer-low, low
What filter has an unstratified media distribution? - COrreCt AnsWer-slow sand filters
What is (are) the combine chlorine residual(s) at pH values ranging from 6.5 to 8.5? - COrreCt
AnsWer-Monochloramine and dichloramine
When iron alone is treated using manganese greensand filters, the chlorine feed rate should be about
_________________. - COrreCt AnsWer-1.0 to 1.2 times the iron concentration
chlorination of water that has high concentrations of natural organic matter will produce - COrreCt
AnsWer-THMs
,When disinfecting with chloramines, when can the ammonia be added to the process? - COrreCt
AnsWer-Before, same time as, or after the chlorine
What will settle out of the water in a short period of time? - COrreCt AnsWer-Very fine silt
Point-of-use activated carbon filters are most effective for removing _________________. - COrreCt
AnsWer-Chlorine
Potassium permanganate is used as an oxidant for control of ____________________. - COrreCt
AnsWer-Iron and manganese, organic precursors, and taste and odors
What must an operator periodically check regarding the cyclone separator system? - COrreCt
AnsWer-Storage bin or hopper to empty of sand and grit
These types of chemicals chemically tie up scale-forming ions and are eventually ingested by consumers.
- COrreCt AnsWer-Sequestering agents
An operator should record filter ______________ measurements, condition, and depth of media on a
________ basis. - COrreCt AnsWer-bed expansion, quarterly
Lime will precipitate noncarbonate hardness from the water, but it also orms noncarbonate salts that
cause noncarbonate hardness. What are these salts? - COrreCt AnsWer-CaSO4 and CaCl2
What are absolute ratings based on with regard to membranes? - COrreCt AnsWer-Largest pore
opening
How ar manganese greensand beds regenerated? - COrreCt AnsWer-Backwashed with
permanganate solution
The most effective process for removing radon gas, when considering cost and footprint, would be
____________. - COrreCt AnsWer-packed tower aeration
,What is the primary advantage of placing a properly sized anthracite coal layer over manganese
greensand? - COrreCt AnsWer-Longer filter run times
What factor will cause problems for chlorination? - COrreCt AnsWer-Foreign substances
In the lime-soda ash softening process, smaller plants find that ________ is less expensive to purchase;
regardless of the size of the plant, ___________ needs to be mixed long enough because it dissolves
rather slowly. - COrreCt AnsWer-calcium hydroxide, lime
What does the optimal pH establish when applied to iron and manganese oxidation? - COrreCt
AnsWer-Detention time
A water plant using chloramines as a disinfectant has allowed sizable amounts of turbidity to enter the
distribution system. If this occurs over a period of years, what will occur at the far end of the distribution
system? - COrreCt AnsWer-Taste and odor will develop, Bacterial growth will be supported, and
Nitrification
The reduction of color would most likely occur after - COrreCt AnsWer-coagulation, flocculation, and
sedimentation
To eliminate hydrogen sulfide (H2S), the pH of the water should be lowered to ____________ or less
before beginning aeration. - COrreCt AnsWer-6.0
Permanganate reactions are largely dependent on ___________. - COrreCt AnsWer-pH
What are the primary reasons that more small water stems are installing pressure filters? - COrreCt
AnsWer-Because installation and operating costs are low
Because lime slurries have a _________ and a ___________ in water, calcium carbonate will
____________ on anything the slurry touches. - COrreCt AnsWer-high pH, low solubility, preciptate
It is recommended that the free chlorine residual at a customer's tap should be at least ________. -
COrreCt AnsWer-0.2 mg/L
, Microfiltration is considered to be intermediate between ___________ based on pore size. - COrreCt
AnsWer-ultrafiltration and multimedia granular filtration
After microscreening, there should be a significant reduction in ______________. - COrreCt AnsWer-
Turbidity
How can the problem of poorly formed floc be solved? - COrreCt AnsWer-Use of coagulant aid
What chemical used in corrosion control gives off large quantities of CO2 when it comes in contact with
an acid? - COrreCt AnsWer-Soda ash
Alum requires _____________ to be present naturally or added fro proper coagulation, and about
_____________ is required for each milligram of alum added per liter. - COrreCt AnsWer-alkalinity,
0.5 mg/L
A cloudy appearance in the last flocculation chamber is usually caused by ____________. - COrreCt
AnsWer-inadequate coagulant dosage
What type of meter is most commonly use for customer metering? - COrreCt AnsWer-Positive-
displacement meters
In general, the size of floc that has been found to be optimal for settling efficiency is
____________________. - COrreCt AnsWer-pinhead-size floc
In a pulsator clarifier, what is the purpose of the pulses and how often are pulses generated? - COrreCt
AnsWer-To maintain a uniform sludge layer; 40-50 sec
UV application will - COrreCt AnsWer-inhibit bacterial growth and replication
Calcium hypochlorite used in water treatment disinfection ranges in percentage strength of available
chlorine from _______________. - COrreCt AnsWer-65% to 70%
