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Colorado Wastewater Treatment Operator Class B
Exam Questions and Correct Answers with
EXPLANATIONS LATEST THIS YEAR
Summarized Exam Coverage — Colorado Wastewater Treatment Operator Class B
The Colorado Class B exam certifies operators for domestic or industrial wastewater treatment facilities
at the mid-to-large scale. Candidates must hold a Class C certification and have 3 years of experience .
Topics include: primary/secondary/tertiary treatment (activated sludge, trickling filters, RBCs), solids
handling, disinfection, nutrient removal, process control, laboratory testing, safety (confined space, PPE,
chemical handling), Colorado Regulation No. 100 (5 CCR 1003-2), effluent limits (C.R.S. 300-6-102), ORC
responsibilities, discharge monitoring reports (DMRs), maintenance, recordkeeping, and 40 training
units (TUs) required for renewal over 5 years .
1. A Class B plant experiences an upset. The Operator in Responsible Charge (ORC) must immediately:
A) Shut down the entire plant
B) Bypass all units to protect equipment
C) Notify the permit holder and document the upset in the DMR
D) Increase aeration to mask the problem
Answer: C
Rationale: ORC must notify permit holder and record upset in Discharge Monitoring Report (DMR) per
Colorado Regulation 100 .
2. A final effluent sample shows high chlorine residual. Which laboratory test should confirm proper
dechlorination?
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A) pH meter calibration
B) Turbidity analysis
C) Titration for chlorine residual
D) BOD incubation
Answer: C
Rationale: Titration is the standard method to measure chlorine residual, ensuring disinfection without
excess chlorine .
3. A roto-biological contactor (RBC) shaft fails to rotate. The most likely cause is:
A) Excessive biofilm loading
B) Low organic loading
C) Bearing seizure or drive belt failure
D) High dissolved oxygen
Answer: C
Rationale: RBC failure to rotate typically indicates mechanical issues such as bearing seizure or drive belt
breakage .
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4. Which Colorado regulation establishes minimum effluent limits for Class B industrial wastewater
discharges?
A) C.R.S. 330-2-502
B) C.R.S. 300-10-101
C) C.R.S. 300-6-102
D) C.R.S. 300-5-101
Answer: C
Rationale: Colorado Regulation 300-6-102 contains specific effluent limitation requirements for Class B
industrial wastewater plants .
5. An operator notices rising turbidity in secondary effluent. The first troubleshooting step is to:
A) Increase chlorine dose
B) Check the activated sludge settling characteristics
C) Bypass the clarifier
D) Shut off aeration
Answer: B
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Rationale: Turbidity increase often indicates poor sludge settling; check sludge volume index (SVI) and
floc condition .
6. A lift station pump cycles on and off rapidly. This condition is called:
A) Deadheading
B) Short-cycling
C) Water hammer
D) Cavitation
Answer: B
Rationale: Rapid cycling, or short-cycling, is caused by improper float settings or a worn check valve .
7. What is the primary purpose of the grit removal system?
A) Remove fine organic solids
B) Eliminate inorganic particles such as sand and gravel
C) Disinfect the wastewater
D) Equalize flow
Answer: B
Colorado Wastewater Treatment Operator Class B
Exam Questions and Correct Answers with
EXPLANATIONS LATEST THIS YEAR
Summarized Exam Coverage — Colorado Wastewater Treatment Operator Class B
The Colorado Class B exam certifies operators for domestic or industrial wastewater treatment facilities
at the mid-to-large scale. Candidates must hold a Class C certification and have 3 years of experience .
Topics include: primary/secondary/tertiary treatment (activated sludge, trickling filters, RBCs), solids
handling, disinfection, nutrient removal, process control, laboratory testing, safety (confined space, PPE,
chemical handling), Colorado Regulation No. 100 (5 CCR 1003-2), effluent limits (C.R.S. 300-6-102), ORC
responsibilities, discharge monitoring reports (DMRs), maintenance, recordkeeping, and 40 training
units (TUs) required for renewal over 5 years .
1. A Class B plant experiences an upset. The Operator in Responsible Charge (ORC) must immediately:
A) Shut down the entire plant
B) Bypass all units to protect equipment
C) Notify the permit holder and document the upset in the DMR
D) Increase aeration to mask the problem
Answer: C
Rationale: ORC must notify permit holder and record upset in Discharge Monitoring Report (DMR) per
Colorado Regulation 100 .
2. A final effluent sample shows high chlorine residual. Which laboratory test should confirm proper
dechlorination?
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A) pH meter calibration
B) Turbidity analysis
C) Titration for chlorine residual
D) BOD incubation
Answer: C
Rationale: Titration is the standard method to measure chlorine residual, ensuring disinfection without
excess chlorine .
3. A roto-biological contactor (RBC) shaft fails to rotate. The most likely cause is:
A) Excessive biofilm loading
B) Low organic loading
C) Bearing seizure or drive belt failure
D) High dissolved oxygen
Answer: C
Rationale: RBC failure to rotate typically indicates mechanical issues such as bearing seizure or drive belt
breakage .
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4. Which Colorado regulation establishes minimum effluent limits for Class B industrial wastewater
discharges?
A) C.R.S. 330-2-502
B) C.R.S. 300-10-101
C) C.R.S. 300-6-102
D) C.R.S. 300-5-101
Answer: C
Rationale: Colorado Regulation 300-6-102 contains specific effluent limitation requirements for Class B
industrial wastewater plants .
5. An operator notices rising turbidity in secondary effluent. The first troubleshooting step is to:
A) Increase chlorine dose
B) Check the activated sludge settling characteristics
C) Bypass the clarifier
D) Shut off aeration
Answer: B
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Rationale: Turbidity increase often indicates poor sludge settling; check sludge volume index (SVI) and
floc condition .
6. A lift station pump cycles on and off rapidly. This condition is called:
A) Deadheading
B) Short-cycling
C) Water hammer
D) Cavitation
Answer: B
Rationale: Rapid cycling, or short-cycling, is caused by improper float settings or a worn check valve .
7. What is the primary purpose of the grit removal system?
A) Remove fine organic solids
B) Eliminate inorganic particles such as sand and gravel
C) Disinfect the wastewater
D) Equalize flow
Answer: B
