COLORADO WASTEWATER OPERATOR CLASS
D EXAM | 230 Practice Questions | Certification
Preparation
SECTION 1: REGULATIONS & LICENSING
1. In Colorado, wastewater treatment plant operators must be certified under which regulatory
authority?
A) Colorado Department of Public Health and Environment (CDPHE), Water Quality
Control Division (correct answer)
B) Colorado Department of Natural Resources
C) U.S. Environmental Protection Agency Region 8
D) Colorado Oil and Gas Conservation Commission
Rationale: The Colorado Water Quality Control Division (WQCD) under CDPHE administers
the operator certification program per Colorado Revised Statutes and Regulation 100. All
wastewater operators in Colorado must be certified by this agency.
2. The Colorado Class D wastewater operator certification is designed for operators of:
A) Large municipal treatment plants treating over 1 million gallons per day
B) Small wastewater treatment facilities, typically serving small communities or facilities
with limited treatment complexity (correct answer)
C) Industrial pretreatment facilities only
D) Biosolids land application sites exclusively
Rationale: The Class D certification is the entry-level wastewater operator certification in
Colorado, intended for operators of small, less complex facilities. It covers basic treatment
processes, safety, and regulatory requirements appropriate for smaller systems.
3. Under Colorado Regulation 100, a certified wastewater operator must notify the WQCD
within how many days if they change their mailing address?
A) 7 days
B) 15 days
C) 30 days (correct answer)
D) 60 days
,Rationale: Colorado Regulation 100 requires certified operators to notify the WQCD of address
changes within 30 days. Failure to maintain current contact information can result in missed
renewal notices and potential certification lapse.
4. Colorado Regulation 61 (CDPS Permits) requires that a wastewater treatment facility's CDPS
permit be:
A) Posted at the main entrance of the facility where it is visible to the public
B) Available for inspection at the facility and followed by the operator at all times
(correct answer)
C) Submitted to the EPA annually for federal review
D) Renewed every year regardless of permit conditions
Rationale: The Colorado Discharge Permit System (CDPS) permit must be kept at the facility
and all permit conditions must be followed by the operator. The permit is the legal authorization
for the discharge and constitutes the operating requirements for the plant.
5. The "responsible charge" operator at a wastewater facility in Colorado is defined as:
A) Any certified operator present at the facility during business hours
B) The certified operator who holds overall responsibility for the day-to-day operation of
the facility (correct answer)
C) The facility owner who signs the Discharge Monitoring Reports
D) The highest-level certified operator in the state regardless of employment
Rationale: The operator in responsible charge (ORC) is the certified operator who has overall
authority and responsibility for the daily operation of the treatment facility. This person must
hold the appropriate level of certification for the facility classification.
6. Discharge Monitoring Reports (DMRs) for Colorado CDPS permit holders must be submitted:
A) Annually on December 31st
B) Only when a permit violation occurs
C) According to the schedule specified in the CDPS permit, typically monthly (correct
answer)
D) Quarterly regardless of permit conditions
Rationale: DMRs must be submitted on the schedule specified in the individual CDPS permit,
which is most commonly monthly. DMRs document effluent quality measurements and are
required even if no violations occurred during the reporting period.
,7. Under Colorado Regulation 100, wastewater operator certifications must be renewed every:
A) Year
B) Two years
C) Three years (correct answer)
D) Five years
Rationale: Colorado wastewater operator certifications are renewed on a three-year cycle.
Renewal requires documentation of continuing education credits and payment of the renewal fee
to the WQCD.
8. The minimum continuing education requirement for renewing a Colorado Class D wastewater
operator certification is:
A) 12 contact hours per renewal period
B) 18 contact hours per renewal period (correct answer)
C) 24 contact hours per renewal period
D) 30 contact hours per renewal period
Rationale: Colorado Regulation 100 requires Class D wastewater operators to complete a
minimum of 18 contact hours of approved continuing education during each three-year renewal
period to maintain their certification.
9. A significant noncompliance (SNC) event at a Colorado CDPS permitted facility must be
reported to CDPHE:
A) Only in the annual DMR summary
B) Within 24 hours verbally, followed by a written report within 5 days (correct answer)
C) Within 30 days in the next monthly DMR
D) Only if the violation exceeds 100% of the permit limit
Rationale: Colorado's CDPS permit conditions require notification of significant noncompliance
within 24 hours of becoming aware of the violation, followed by a written report within five
days. This ensures regulatory oversight of serious permit violations.
10. Which Colorado statute provides the primary authority for the WQCD to regulate water
quality and operator certification?
, A) Colorado Revised Statutes 25-8 (Water Quality Control Act) (correct answer)
B) Colorado Revised Statutes 37-92 (Water Rights)
C) Colorado Revised Statutes 29-20 (Local Government Land Use)
D) Colorado Revised Statutes 24-4 (Administrative Procedure Act)
Rationale: CRS 25-8, the Colorado Water Quality Control Act, establishes the Water Quality
Control Commission's authority to adopt regulations protecting water quality, including the
operator certification program administered by the WQCD.
SECTION 2: WASTEWATER CHARACTERISTICS
11. "Biochemical Oxygen Demand" (BOD) measures:
A) The total amount of oxygen dissolved in wastewater at any given time
B) The amount of oxygen required by microorganisms to decompose organic matter in
wastewater over a defined period (correct answer)
C) The chemical oxygen demand from inorganic compounds only
D) The amount of oxygen produced by algae in receiving water bodies
Rationale: BOD is a measure of the oxygen-consuming potential of wastewater — specifically
the oxygen that bacteria and other microorganisms use to oxidize organic compounds. The
standard BOD₅ test measures oxygen consumption over 5 days at 20°C.
12. The standard BOD test is conducted at what temperature for how many days?
A) 25°C for 7 days
B) 20°C for 5 days (correct answer)
C) 37°C for 3 days
D) 15°C for 10 days
Rationale: The standard BOD₅ test is incubated at 20°C for 5 days. This temperature was
selected because it approximates typical stream temperatures and allows standardized
comparison of results between laboratories and facilities.
13. "Total Suspended Solids" (TSS) in wastewater refers to:
A) All solids dissolved in the wastewater including salts and minerals
B) Solids that can be removed from wastewater by filtration through a standard glass
fiber filter (correct answer)
C) Only organic solids present in raw wastewater
D EXAM | 230 Practice Questions | Certification
Preparation
SECTION 1: REGULATIONS & LICENSING
1. In Colorado, wastewater treatment plant operators must be certified under which regulatory
authority?
A) Colorado Department of Public Health and Environment (CDPHE), Water Quality
Control Division (correct answer)
B) Colorado Department of Natural Resources
C) U.S. Environmental Protection Agency Region 8
D) Colorado Oil and Gas Conservation Commission
Rationale: The Colorado Water Quality Control Division (WQCD) under CDPHE administers
the operator certification program per Colorado Revised Statutes and Regulation 100. All
wastewater operators in Colorado must be certified by this agency.
2. The Colorado Class D wastewater operator certification is designed for operators of:
A) Large municipal treatment plants treating over 1 million gallons per day
B) Small wastewater treatment facilities, typically serving small communities or facilities
with limited treatment complexity (correct answer)
C) Industrial pretreatment facilities only
D) Biosolids land application sites exclusively
Rationale: The Class D certification is the entry-level wastewater operator certification in
Colorado, intended for operators of small, less complex facilities. It covers basic treatment
processes, safety, and regulatory requirements appropriate for smaller systems.
3. Under Colorado Regulation 100, a certified wastewater operator must notify the WQCD
within how many days if they change their mailing address?
A) 7 days
B) 15 days
C) 30 days (correct answer)
D) 60 days
,Rationale: Colorado Regulation 100 requires certified operators to notify the WQCD of address
changes within 30 days. Failure to maintain current contact information can result in missed
renewal notices and potential certification lapse.
4. Colorado Regulation 61 (CDPS Permits) requires that a wastewater treatment facility's CDPS
permit be:
A) Posted at the main entrance of the facility where it is visible to the public
B) Available for inspection at the facility and followed by the operator at all times
(correct answer)
C) Submitted to the EPA annually for federal review
D) Renewed every year regardless of permit conditions
Rationale: The Colorado Discharge Permit System (CDPS) permit must be kept at the facility
and all permit conditions must be followed by the operator. The permit is the legal authorization
for the discharge and constitutes the operating requirements for the plant.
5. The "responsible charge" operator at a wastewater facility in Colorado is defined as:
A) Any certified operator present at the facility during business hours
B) The certified operator who holds overall responsibility for the day-to-day operation of
the facility (correct answer)
C) The facility owner who signs the Discharge Monitoring Reports
D) The highest-level certified operator in the state regardless of employment
Rationale: The operator in responsible charge (ORC) is the certified operator who has overall
authority and responsibility for the daily operation of the treatment facility. This person must
hold the appropriate level of certification for the facility classification.
6. Discharge Monitoring Reports (DMRs) for Colorado CDPS permit holders must be submitted:
A) Annually on December 31st
B) Only when a permit violation occurs
C) According to the schedule specified in the CDPS permit, typically monthly (correct
answer)
D) Quarterly regardless of permit conditions
Rationale: DMRs must be submitted on the schedule specified in the individual CDPS permit,
which is most commonly monthly. DMRs document effluent quality measurements and are
required even if no violations occurred during the reporting period.
,7. Under Colorado Regulation 100, wastewater operator certifications must be renewed every:
A) Year
B) Two years
C) Three years (correct answer)
D) Five years
Rationale: Colorado wastewater operator certifications are renewed on a three-year cycle.
Renewal requires documentation of continuing education credits and payment of the renewal fee
to the WQCD.
8. The minimum continuing education requirement for renewing a Colorado Class D wastewater
operator certification is:
A) 12 contact hours per renewal period
B) 18 contact hours per renewal period (correct answer)
C) 24 contact hours per renewal period
D) 30 contact hours per renewal period
Rationale: Colorado Regulation 100 requires Class D wastewater operators to complete a
minimum of 18 contact hours of approved continuing education during each three-year renewal
period to maintain their certification.
9. A significant noncompliance (SNC) event at a Colorado CDPS permitted facility must be
reported to CDPHE:
A) Only in the annual DMR summary
B) Within 24 hours verbally, followed by a written report within 5 days (correct answer)
C) Within 30 days in the next monthly DMR
D) Only if the violation exceeds 100% of the permit limit
Rationale: Colorado's CDPS permit conditions require notification of significant noncompliance
within 24 hours of becoming aware of the violation, followed by a written report within five
days. This ensures regulatory oversight of serious permit violations.
10. Which Colorado statute provides the primary authority for the WQCD to regulate water
quality and operator certification?
, A) Colorado Revised Statutes 25-8 (Water Quality Control Act) (correct answer)
B) Colorado Revised Statutes 37-92 (Water Rights)
C) Colorado Revised Statutes 29-20 (Local Government Land Use)
D) Colorado Revised Statutes 24-4 (Administrative Procedure Act)
Rationale: CRS 25-8, the Colorado Water Quality Control Act, establishes the Water Quality
Control Commission's authority to adopt regulations protecting water quality, including the
operator certification program administered by the WQCD.
SECTION 2: WASTEWATER CHARACTERISTICS
11. "Biochemical Oxygen Demand" (BOD) measures:
A) The total amount of oxygen dissolved in wastewater at any given time
B) The amount of oxygen required by microorganisms to decompose organic matter in
wastewater over a defined period (correct answer)
C) The chemical oxygen demand from inorganic compounds only
D) The amount of oxygen produced by algae in receiving water bodies
Rationale: BOD is a measure of the oxygen-consuming potential of wastewater — specifically
the oxygen that bacteria and other microorganisms use to oxidize organic compounds. The
standard BOD₅ test measures oxygen consumption over 5 days at 20°C.
12. The standard BOD test is conducted at what temperature for how many days?
A) 25°C for 7 days
B) 20°C for 5 days (correct answer)
C) 37°C for 3 days
D) 15°C for 10 days
Rationale: The standard BOD₅ test is incubated at 20°C for 5 days. This temperature was
selected because it approximates typical stream temperatures and allows standardized
comparison of results between laboratories and facilities.
13. "Total Suspended Solids" (TSS) in wastewater refers to:
A) All solids dissolved in the wastewater including salts and minerals
B) Solids that can be removed from wastewater by filtration through a standard glass
fiber filter (correct answer)
C) Only organic solids present in raw wastewater
