Class D Water Operator Exam
Questions and Answers 100% Pass
What are some physical characteristics of water? - ✔✔Temperature, turbidity, color, taste, odor
What are some chemical characteristics of water? - ✔✔Hardness, pH, solids, and gases
What is turbidity? - ✔✔the amount of suspended matter, such as clay, silt, organic matter, and
microorganisms in water
T/F Water is never found pure in nature. - ✔✔True
Is turbidity more of a problem in groundwater or surface water? - ✔✔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. - ✔✔0.3
1
T/F True color is dissolved in water (in solution) and cannot be removed by filtering. - ✔✔True. Tea in
water is an example of true color.
Suspended color is called _______ color. - ✔✔apparent
Color above ______ units is objectionable in a public water supply. - ✔✔15 units
A scale called the ________ measures odor. - ✔✔Threshold Odor Number (TON)
Odor greater than a scale of _______ is undesirable. - ✔✔3
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,Taste and odors in water result from _______, bacteria, decaying organic matter, gases, and chemicals
such as manganese, zinc, copper, iron, magnesium, sodium, and potassium. - ✔✔algae
Chemical characteristics of water generally cannot be detected by sight, smell, or taste and must be
determined by __________. - ✔✔laboratory analysis
Chemical laboratory analysis must be sampled _______ per year for surface water and normally _______
for groundwater. - ✔✔once/year for surface water
once every three years for groundwater
Water weighs ______ lbs/gal. - ✔✔8.34 lbs/gal
T/F
For water, 1 mg/L is equal to 1 part per million (ppm) by weight. - ✔✔True
Which two minerals mainly cause hardness in water? - ✔✔Calcium and magnesium
Is hardness more of a problem in groundwater or surface water? - ✔✔Groundwater
Water is considered hard when it exceeds _______. - ✔✔100 mg/L of calcium carbonate
The pH scale ranges from _____ to _____. - ✔✔0 to 14
On the pH scale:
0 to <7 is ______.
7 is _______.
>7 to 14 is ______. - ✔✔Acidic
Neutral
Basic or alkaline
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, Sulfuric, hydrochloric, and nitric acids can be used to ______ pH.
Caustic, lime, or soda ash can be used to ______ pH. - ✔✔Lower
Raise
Suspended solids can be removed by ________. - ✔✔Filtration
Can dissolved solids be removed by filtration? - ✔✔No
Total dissolved solids should not exceed________. - ✔✔1000 mg/L
What are three common gasses found in water? - ✔✔Hydrogen sulfide, carbon dioxide, and methane
Excess ________ can cause blue baby syndrome. - ✔✔Nitrogen or Nitrates
What is the major source of nitrogen into drinking water? - ✔✔Fertilizer and animal waste carried by
rainwater runoff
What is the EPA primary MCL (maximum contaminant level) for fluoride? - ✔✔4.0 mg/L
At what level will fluoride cause mottling of teeth, a condition known as fluorosis? - ✔✔4.0 mg/L
What is the state of Texas secondary standard for fluoride? - ✔✔2.0 mg/L
Trihalomethanes (THM) and Haloacetic Acids (HAA) are byproducts of drinking water ________. -
✔✔chlorination
THM's and HAA's are byproducts formed when chlorine reacts with dissolved _________. - ✔✔natural
organic matter, mostly plant life
Combining chlorine with _______ greatly reduces THM and HAA formation. - ✔✔ammonia
Is surface water or groundwater more likely to contain natural organic matter? - ✔✔surface water
What is chloramine? - ✔✔Chlorine combined with ammonia
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Questions and Answers 100% Pass
What are some physical characteristics of water? - ✔✔Temperature, turbidity, color, taste, odor
What are some chemical characteristics of water? - ✔✔Hardness, pH, solids, and gases
What is turbidity? - ✔✔the amount of suspended matter, such as clay, silt, organic matter, and
microorganisms in water
T/F Water is never found pure in nature. - ✔✔True
Is turbidity more of a problem in groundwater or surface water? - ✔✔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. - ✔✔0.3
1
T/F True color is dissolved in water (in solution) and cannot be removed by filtering. - ✔✔True. Tea in
water is an example of true color.
Suspended color is called _______ color. - ✔✔apparent
Color above ______ units is objectionable in a public water supply. - ✔✔15 units
A scale called the ________ measures odor. - ✔✔Threshold Odor Number (TON)
Odor greater than a scale of _______ is undesirable. - ✔✔3
EMILY CHARLENE © 2025, ALL RIGHTS RESERVED 1
,Taste and odors in water result from _______, bacteria, decaying organic matter, gases, and chemicals
such as manganese, zinc, copper, iron, magnesium, sodium, and potassium. - ✔✔algae
Chemical characteristics of water generally cannot be detected by sight, smell, or taste and must be
determined by __________. - ✔✔laboratory analysis
Chemical laboratory analysis must be sampled _______ per year for surface water and normally _______
for groundwater. - ✔✔once/year for surface water
once every three years for groundwater
Water weighs ______ lbs/gal. - ✔✔8.34 lbs/gal
T/F
For water, 1 mg/L is equal to 1 part per million (ppm) by weight. - ✔✔True
Which two minerals mainly cause hardness in water? - ✔✔Calcium and magnesium
Is hardness more of a problem in groundwater or surface water? - ✔✔Groundwater
Water is considered hard when it exceeds _______. - ✔✔100 mg/L of calcium carbonate
The pH scale ranges from _____ to _____. - ✔✔0 to 14
On the pH scale:
0 to <7 is ______.
7 is _______.
>7 to 14 is ______. - ✔✔Acidic
Neutral
Basic or alkaline
EMILY CHARLENE © 2025, ALL RIGHTS RESERVED 2
, Sulfuric, hydrochloric, and nitric acids can be used to ______ pH.
Caustic, lime, or soda ash can be used to ______ pH. - ✔✔Lower
Raise
Suspended solids can be removed by ________. - ✔✔Filtration
Can dissolved solids be removed by filtration? - ✔✔No
Total dissolved solids should not exceed________. - ✔✔1000 mg/L
What are three common gasses found in water? - ✔✔Hydrogen sulfide, carbon dioxide, and methane
Excess ________ can cause blue baby syndrome. - ✔✔Nitrogen or Nitrates
What is the major source of nitrogen into drinking water? - ✔✔Fertilizer and animal waste carried by
rainwater runoff
What is the EPA primary MCL (maximum contaminant level) for fluoride? - ✔✔4.0 mg/L
At what level will fluoride cause mottling of teeth, a condition known as fluorosis? - ✔✔4.0 mg/L
What is the state of Texas secondary standard for fluoride? - ✔✔2.0 mg/L
Trihalomethanes (THM) and Haloacetic Acids (HAA) are byproducts of drinking water ________. -
✔✔chlorination
THM's and HAA's are byproducts formed when chlorine reacts with dissolved _________. - ✔✔natural
organic matter, mostly plant life
Combining chlorine with _______ greatly reduces THM and HAA formation. - ✔✔ammonia
Is surface water or groundwater more likely to contain natural organic matter? - ✔✔surface water
What is chloramine? - ✔✔Chlorine combined with ammonia
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