Minnesota Drinking Water Operator
Class D Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. What is the primary responsibility of a drinking water operator?
A. Designing new residential plumbing systems
B. Ensuring safe and reliable production of drinking water
C. Selling bottled water products
D. Installing household water filters
Answer: B. Ensuring safe and reliable production of drinking water
The drinking water operator’s main duty is to operate and monitor water
treatment and distribution systems so that public health is protected and
drinking water standards are maintained.
2. Which agency regulates public drinking water systems in Minnesota?
,A. Minnesota Department of Agriculture
B. Minnesota Department of Transportation
C. Minnesota Department of Health
D. Minnesota Pollution Control Agency only
Answer: C. Minnesota Department of Health
The Minnesota Department of Health oversees public drinking water
systems and enforces requirements related to drinking water safety.
3. The main purpose of water treatment is to:
A. Increase water color
B. Remove contaminants and protect public health
C. Make water more acidic
D. Add unnecessary minerals
Answer: B. Remove contaminants and protect public health
Water treatment processes are designed to remove harmful substances
and ensure water meets health-based standards.
4. A public water system is generally defined as a system that:
A. Serves only one private home
B. Provides water for human consumption to the public
,C. Stores rainwater only
D. Provides irrigation water exclusively
Answer: B. Provides water for human consumption to the public
Public water systems supply drinking water to people and must meet
regulatory requirements for safety and operation.
5. The first step in many water treatment plants is:
A. Disinfection
B. Filtration
C. Screening or removal of large debris
D. Fluoridation
Answer: C. Screening or removal of large debris
Initial treatment removes large materials that could interfere with later
treatment processes.
6. Turbidity in drinking water refers to:
A. Water temperature
B. Cloudiness caused by suspended particles
C. Chlorine concentration
D. Water pressure
Answer: B. Cloudiness caused by suspended particles
, Turbidity measures the presence of suspended particles that can affect
water appearance and treatment effectiveness.
7. A nephelometric turbidity unit is abbreviated as:
A. ppm
B. NTU
C. psi
D. mg/L
Answer: B. NTU
NTU is the standard unit used to measure turbidity based on light
scattering.
8. Chlorine is commonly used in water treatment because it:
A. Adds hardness
B. Removes all minerals
C. Disinfects water
D. Raises turbidity
Answer: C. Disinfects water
Chlorine kills or inactivates many disease-causing microorganisms in
drinking water.
9. The term “residual chlorine” means:
Class D Exam Practice Questions And
Correct Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
Download Pdf
1. What is the primary responsibility of a drinking water operator?
A. Designing new residential plumbing systems
B. Ensuring safe and reliable production of drinking water
C. Selling bottled water products
D. Installing household water filters
Answer: B. Ensuring safe and reliable production of drinking water
The drinking water operator’s main duty is to operate and monitor water
treatment and distribution systems so that public health is protected and
drinking water standards are maintained.
2. Which agency regulates public drinking water systems in Minnesota?
,A. Minnesota Department of Agriculture
B. Minnesota Department of Transportation
C. Minnesota Department of Health
D. Minnesota Pollution Control Agency only
Answer: C. Minnesota Department of Health
The Minnesota Department of Health oversees public drinking water
systems and enforces requirements related to drinking water safety.
3. The main purpose of water treatment is to:
A. Increase water color
B. Remove contaminants and protect public health
C. Make water more acidic
D. Add unnecessary minerals
Answer: B. Remove contaminants and protect public health
Water treatment processes are designed to remove harmful substances
and ensure water meets health-based standards.
4. A public water system is generally defined as a system that:
A. Serves only one private home
B. Provides water for human consumption to the public
,C. Stores rainwater only
D. Provides irrigation water exclusively
Answer: B. Provides water for human consumption to the public
Public water systems supply drinking water to people and must meet
regulatory requirements for safety and operation.
5. The first step in many water treatment plants is:
A. Disinfection
B. Filtration
C. Screening or removal of large debris
D. Fluoridation
Answer: C. Screening or removal of large debris
Initial treatment removes large materials that could interfere with later
treatment processes.
6. Turbidity in drinking water refers to:
A. Water temperature
B. Cloudiness caused by suspended particles
C. Chlorine concentration
D. Water pressure
Answer: B. Cloudiness caused by suspended particles
, Turbidity measures the presence of suspended particles that can affect
water appearance and treatment effectiveness.
7. A nephelometric turbidity unit is abbreviated as:
A. ppm
B. NTU
C. psi
D. mg/L
Answer: B. NTU
NTU is the standard unit used to measure turbidity based on light
scattering.
8. Chlorine is commonly used in water treatment because it:
A. Adds hardness
B. Removes all minerals
C. Disinfects water
D. Raises turbidity
Answer: C. Disinfects water
Chlorine kills or inactivates many disease-causing microorganisms in
drinking water.
9. The term “residual chlorine” means:
