CLASS D WATER OPERATOR COMPLETE EXAM STUDY
GUIDE WITH PRACTICE QUESTIONS AND VERIFIED
ANSWERS 2025–2026
What are some physical characteristics of water? - correct answer -Temperature, turbidity,
color, taste, odor
What are some chemical characteristics of water? - correct answer -Hardness, pH, solids, and
gases
What is turbidity? - correct 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. - correct answer -True
Is turbidity more of a problem in groundwater or surface water? - correct 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. -
correct answer -0.3
1
T/F True color is dissolved in water (in solution) and cannot be removed by filtering. - correct
answer -True. Tea in water is an example of true color.
Suspended color is called _______ color. - correct answer -apparent
,Color above ______ units is objectionable in a public water supply. - correct answer -15 units
A scale called the ________ measures odor. - correct answer -Threshold Odor Number (TON)
Odor greater than a scale of _______ is undesirable. - correct 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. - correct
answer -algae
Chemical characteristics of water generally cannot be detected by sight, smell, or taste and
must be determined by __________. - correct answer -laboratory analysis
Chemical laboratory analysis must be sampled _______ per year for surface water and normally
_______ for groundwater. - correct answer -once/year for surface water
once every three years for groundwater
Water weighs ______ lbs/gal. - correct answer -8.34 lbs/gal
T/F
For water, 1 mg/L is equal to 1 part per million (ppm) by weight. - correct answer -True
Which two minerals mainly cause hardness in water? - correct answer -Calcium and magnesium
Is hardness more of a problem in groundwater or surface water? - correct answer -
Groundwater
, Water is considered hard when it exceeds _______. - correct answer -100 mg/L of calcium
carbonate
The pH scale ranges from _____ to _____. - correct answer -0 to 14
On the pH scale:
0 to <7 is ______.
7 is _______.
>7 to 14 is ______. - correct 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. - correct answer -Lower
Raise
Suspended solids can be removed by ________. - correct answer -Filtration
Can dissolved solids be removed by filtration? - correct answer -No
Total dissolved solids should not exceed________. - correct answer -1000 mg/L
What are three common gasses found in water? - correct answer -Hydrogen sulfide, carbon
dioxide, and methane
Excess ________ can cause blue baby syndrome. - correct answer -Nitrogen or Nitrates
GUIDE WITH PRACTICE QUESTIONS AND VERIFIED
ANSWERS 2025–2026
What are some physical characteristics of water? - correct answer -Temperature, turbidity,
color, taste, odor
What are some chemical characteristics of water? - correct answer -Hardness, pH, solids, and
gases
What is turbidity? - correct 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. - correct answer -True
Is turbidity more of a problem in groundwater or surface water? - correct 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. -
correct answer -0.3
1
T/F True color is dissolved in water (in solution) and cannot be removed by filtering. - correct
answer -True. Tea in water is an example of true color.
Suspended color is called _______ color. - correct answer -apparent
,Color above ______ units is objectionable in a public water supply. - correct answer -15 units
A scale called the ________ measures odor. - correct answer -Threshold Odor Number (TON)
Odor greater than a scale of _______ is undesirable. - correct 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. - correct
answer -algae
Chemical characteristics of water generally cannot be detected by sight, smell, or taste and
must be determined by __________. - correct answer -laboratory analysis
Chemical laboratory analysis must be sampled _______ per year for surface water and normally
_______ for groundwater. - correct answer -once/year for surface water
once every three years for groundwater
Water weighs ______ lbs/gal. - correct answer -8.34 lbs/gal
T/F
For water, 1 mg/L is equal to 1 part per million (ppm) by weight. - correct answer -True
Which two minerals mainly cause hardness in water? - correct answer -Calcium and magnesium
Is hardness more of a problem in groundwater or surface water? - correct answer -
Groundwater
, Water is considered hard when it exceeds _______. - correct answer -100 mg/L of calcium
carbonate
The pH scale ranges from _____ to _____. - correct answer -0 to 14
On the pH scale:
0 to <7 is ______.
7 is _______.
>7 to 14 is ______. - correct 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. - correct answer -Lower
Raise
Suspended solids can be removed by ________. - correct answer -Filtration
Can dissolved solids be removed by filtration? - correct answer -No
Total dissolved solids should not exceed________. - correct answer -1000 mg/L
What are three common gasses found in water? - correct answer -Hydrogen sulfide, carbon
dioxide, and methane
Excess ________ can cause blue baby syndrome. - correct answer -Nitrogen or Nitrates
