SWRCB – WASTE WATER TREATMENT PLANT OPERATOR CERTIFICATION EXAM GRADE II– QUESTIONS AND
ANSWERS | VERIFIED AND WELL DETAILED ANSWERS | PLUS RATIONALES | DOWNLOAD AND PASS | LATEST
EXAM UPDATE 2026/2027
Core Domains:
Safety Practices and Hazard Awareness
Preliminary and Primary Treatment Operations
Secondary Treatment (Activated Sludge, Trickling Filters, Ponds)
Sludge Digestion, Handling, and Disposal
Disinfection and Effluent Quality
Process Calculations and Math
Regulations, Ethics, and Supervision
Introduction:
The Grade II Wastewater Treatment Plant Operator Certification Examination assesses the knowledge and skills
required to operate and maintain wastewater treatment facilities independently. This examination evaluates
competence in process control, regulatory compliance, safety procedures, and troubleshooting of treatment unit
processes. Questions include multiple-choice and scenario-based formats designed to test real-world decision-making
,and applied professional judgment. Candidates must demonstrate mastery of foundational theory, mathematical
calculations, and operational best practices essential for protecting public health and the environment.
SECTION ONE: QUESTIONS 1–50
Question 1
The F in the F/M ratio for activated sludge represents which of the following?
A. The pounds of mixed liquor volatile suspended solids under aeration
B. The pounds of BOD or COD applied to the aeration tank per day
C. The flow rate entering the secondary clarifier
D. The food waste discharged from the primary clarifier
🟢 Correct Answer: B. The pounds of BOD or COD applied to the aeration tank per day
🔴 Explanation: In the Food-to-Microorganism ratio, "F" stands for the food (organic loading, measured as BOD or
COD) applied to the biological system, while "M" represents the mass of microorganisms (MLVSS) available to
consume that food .
,Question 2
Digester gas containing approximately 60% methane by volume can become explosive when mixed with air in which
concentration range?
A. 1 to 5 percent methane in air
B. 5 to 15 percent methane in air
C. 20 to 40 percent methane in air
D. 50 to 70 percent methane in air
🟢 Correct Answer: B. 5 to 15 percent methane in air
🔴 Explanation: Methane gas becomes explosive when present in air at concentrations between approximately 5%
and 15% by volume. The lower explosive limit (LEL) is about 5%, and the upper explosive limit (UEL) is approximately
15% .
Question 3
In standard wastewater treatment calculations, the units ppm and mg/L are considered:
, A. Equivalent for practical purposes
B. Different by a factor of 1,000
C. Applicable only to gases
D. Interchangeable only for sludge measurements
🟢 Correct Answer: A. Equivalent for practical purposes
🔴 Explanation: For dilute aqueous solutions typical in wastewater treatment, 1 ppm (part per million) is
approximately equal to 1 mg/L because the density of water is approximately 1 kg/L .
Question 4
The velocity of wastewater flowing through a long channel-type grit chamber is typically controlled by:
A. A proportional weir
B. A butterfly valve
C. A centrifugal pump
D. Manual adjustment of the gate
🟢 Correct Answer: A. A proportional weir
ANSWERS | VERIFIED AND WELL DETAILED ANSWERS | PLUS RATIONALES | DOWNLOAD AND PASS | LATEST
EXAM UPDATE 2026/2027
Core Domains:
Safety Practices and Hazard Awareness
Preliminary and Primary Treatment Operations
Secondary Treatment (Activated Sludge, Trickling Filters, Ponds)
Sludge Digestion, Handling, and Disposal
Disinfection and Effluent Quality
Process Calculations and Math
Regulations, Ethics, and Supervision
Introduction:
The Grade II Wastewater Treatment Plant Operator Certification Examination assesses the knowledge and skills
required to operate and maintain wastewater treatment facilities independently. This examination evaluates
competence in process control, regulatory compliance, safety procedures, and troubleshooting of treatment unit
processes. Questions include multiple-choice and scenario-based formats designed to test real-world decision-making
,and applied professional judgment. Candidates must demonstrate mastery of foundational theory, mathematical
calculations, and operational best practices essential for protecting public health and the environment.
SECTION ONE: QUESTIONS 1–50
Question 1
The F in the F/M ratio for activated sludge represents which of the following?
A. The pounds of mixed liquor volatile suspended solids under aeration
B. The pounds of BOD or COD applied to the aeration tank per day
C. The flow rate entering the secondary clarifier
D. The food waste discharged from the primary clarifier
🟢 Correct Answer: B. The pounds of BOD or COD applied to the aeration tank per day
🔴 Explanation: In the Food-to-Microorganism ratio, "F" stands for the food (organic loading, measured as BOD or
COD) applied to the biological system, while "M" represents the mass of microorganisms (MLVSS) available to
consume that food .
,Question 2
Digester gas containing approximately 60% methane by volume can become explosive when mixed with air in which
concentration range?
A. 1 to 5 percent methane in air
B. 5 to 15 percent methane in air
C. 20 to 40 percent methane in air
D. 50 to 70 percent methane in air
🟢 Correct Answer: B. 5 to 15 percent methane in air
🔴 Explanation: Methane gas becomes explosive when present in air at concentrations between approximately 5%
and 15% by volume. The lower explosive limit (LEL) is about 5%, and the upper explosive limit (UEL) is approximately
15% .
Question 3
In standard wastewater treatment calculations, the units ppm and mg/L are considered:
, A. Equivalent for practical purposes
B. Different by a factor of 1,000
C. Applicable only to gases
D. Interchangeable only for sludge measurements
🟢 Correct Answer: A. Equivalent for practical purposes
🔴 Explanation: For dilute aqueous solutions typical in wastewater treatment, 1 ppm (part per million) is
approximately equal to 1 mg/L because the density of water is approximately 1 kg/L .
Question 4
The velocity of wastewater flowing through a long channel-type grit chamber is typically controlled by:
A. A proportional weir
B. A butterfly valve
C. A centrifugal pump
D. Manual adjustment of the gate
🟢 Correct Answer: A. A proportional weir
