Class D Water Operator Exam 2026
Questions and Answers
What are some physical characteristics of water? - Answer -Temperature, turbidity,
color, taste, odor
What are some chemical characteristics of water? - Answer -Hardness, pH, solids,
and gases
What is turbidity? - Answer -the amount of suspended matter, such as clay, silt,
organic matter, and microorganisms in water
T/F Water is never found pure in nature. - Answer -True
Is turbidity more of a problem in groundwater or surface water? - Answer -Surface
water
A system's filtered water must be _______ Nephelometric Turbidity Units (NTU)
or less in at least 95% of the measurements taken each month, and no sample can
exceed _____ NTU. - Answer -0.3
1
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,T/F True color is dissolved in water (in solution) and cannot be removed by
filtering. - Answer -True. Tea in water is an example of true color.
Suspended color is called _______ color. - Answer -apparent
Color above ______ units is objectionable in a public water supply. - Answer -15
units
A scale called the ________ measures odor. - Answer -Threshold Odor Number
(TON)
Odor greater than a scale of _______ is undesirable. - Answer -3
Taste and odors in water result from _______, bacteria, decaying organic matter,
gases, and chemicals such as manganese, zinc, copper, iron, magnesium, sodium,
and potassium. - Answer -algae
Chemical characteristics of water generally cannot be detected by sight, smell, or
taste and must be determined by __________. - Answer -laboratory analysis
Chemical laboratory analysis must be sampled _______ per year for surface water
and normally _______ for groundwater. - Answer -once/year for surface water
once every three years for groundwater
Water weighs ______ lbs/gal. - Answer -8.34 lbs/gal
T/F
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, For water, 1 mg/L is equal to 1 part per million (ppm) by weight. - Answer -True
Which two minerals mainly cause hardness in water? - Answer -Calcium and
magnesium
Is hardness more of a problem in groundwater or surface water? - Answer -
Groundwater
Water is considered hard when it exceeds _______. - Answer -100 mg/L of calcium
carbonate
The pH scale ranges from _____ to _____. - Answer -0 to 14
On the pH scale:
0 to <7 is ______.
7 is _______.
>7 to 14 is ______. - Answer -Acidic
Neutral
Basic or alkaline
Sulfuric, hydrochloric, and nitric acids can be used to ______ pH.
Caustic, lime, or soda ash can be used to ______ pH. - Answer -Lower
Raise
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Questions and Answers
What are some physical characteristics of water? - Answer -Temperature, turbidity,
color, taste, odor
What are some chemical characteristics of water? - Answer -Hardness, pH, solids,
and gases
What is turbidity? - Answer -the amount of suspended matter, such as clay, silt,
organic matter, and microorganisms in water
T/F Water is never found pure in nature. - Answer -True
Is turbidity more of a problem in groundwater or surface water? - Answer -Surface
water
A system's filtered water must be _______ Nephelometric Turbidity Units (NTU)
or less in at least 95% of the measurements taken each month, and no sample can
exceed _____ NTU. - Answer -0.3
1
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,T/F True color is dissolved in water (in solution) and cannot be removed by
filtering. - Answer -True. Tea in water is an example of true color.
Suspended color is called _______ color. - Answer -apparent
Color above ______ units is objectionable in a public water supply. - Answer -15
units
A scale called the ________ measures odor. - Answer -Threshold Odor Number
(TON)
Odor greater than a scale of _______ is undesirable. - Answer -3
Taste and odors in water result from _______, bacteria, decaying organic matter,
gases, and chemicals such as manganese, zinc, copper, iron, magnesium, sodium,
and potassium. - Answer -algae
Chemical characteristics of water generally cannot be detected by sight, smell, or
taste and must be determined by __________. - Answer -laboratory analysis
Chemical laboratory analysis must be sampled _______ per year for surface water
and normally _______ for groundwater. - Answer -once/year for surface water
once every three years for groundwater
Water weighs ______ lbs/gal. - Answer -8.34 lbs/gal
T/F
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, For water, 1 mg/L is equal to 1 part per million (ppm) by weight. - Answer -True
Which two minerals mainly cause hardness in water? - Answer -Calcium and
magnesium
Is hardness more of a problem in groundwater or surface water? - Answer -
Groundwater
Water is considered hard when it exceeds _______. - Answer -100 mg/L of calcium
carbonate
The pH scale ranges from _____ to _____. - Answer -0 to 14
On the pH scale:
0 to <7 is ______.
7 is _______.
>7 to 14 is ______. - Answer -Acidic
Neutral
Basic or alkaline
Sulfuric, hydrochloric, and nitric acids can be used to ______ pH.
Caustic, lime, or soda ash can be used to ______ pH. - Answer -Lower
Raise
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