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California Water System/Treatment Operator Grade 2
(T2) Exam QUESTIONS AND CORRECT ANSWERS LATEST
UPDATE THIS YEAR
California Water System/Treatment Operator Grade 2 (T2) Exam
EXAM COVERAGE (Point Form)
• Fundamental Water Treatment Operations, Process Monitoring, Water Quality & Regulatory
Compliance (Core Exam Area)
• Drinking Water Regulations, Public Health & Regulatory Compliance
• Water Treatment Fundamentals
• Disinfection & Water Quality Control
• Plant Operations, Equipment & Process Monitoring
• Water Chemistry, Laboratory Analysis & Treatment Mathematics
• Distribution System Fundamentals
• Safety, Emergency Response & Risk Management
• Professional Responsibilities & Documentation
QUESTIONS 1-100
1. A water treatment plant operator notices that the turbidity of the finished water is increasing
despite the filters operating normally. Which of the following is the MOST likely cause of this increase
in turbidity, and what is the appropriate action to take?
A. The coagulant dosage is too high, causing floc carryover; the operator should decrease the coagulant
feed rate.
B. The filter media is becoming fouled; the operator should backwash the filters immediately.
C. A change in source water quality is affecting coagulation; the operator should perform jar tests to
determine the optimal coagulant dosage.
D. The pH of the water is too low; the operator should add lime to raise the pH.
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Correct Answer: C
Rationale: A change in source water quality, such as increased turbidity or altered pH and alkalinity, can
affect coagulation efficiency and lead to increased turbidity in the finished water . The operator should
perform jar tests to determine the new optimal coagulant dosage for the current water quality
conditions.
2. Under California Title 22 drinking water regulations, which of the following is the primary purpose
of the Maximum Contaminant Level (MCL) for total coliform bacteria, and what does a positive total
coliform test indicate?
A. To ensure the water is free from all bacteria; a positive test indicates the water is unsafe to drink.
B. To serve as an indicator of potential fecal contamination and the possible presence of disease-causing
organisms; a positive test indicates a potential health risk that requires investigation.
C. To measure the effectiveness of the disinfection process; a positive test indicates the chlorine residual
is too low.
D. To monitor the turbidity of the water; a positive test indicates the filters are not working properly.
Correct Answer: B
Rationale: Total coliform bacteria are used as indicator organisms to signal the potential presence of
pathogenic organisms in drinking water . A positive total coliform test suggests possible fecal
contamination and requires immediate investigation and corrective action.
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3. A water treatment operator is calculating the chlorine demand of a water sample. The chlorine
dose is 3.0 mg/L, and the chlorine residual after 30 minutes of contact time is 1.2 mg/L. What is the
chlorine demand of this water sample?
A. 1.2 mg/L
B. 1.8 mg/L
C. 3.0 mg/L
D. 4.2 mg/L
Correct Answer: B
Rationale: Chlorine demand is calculated as the chlorine dose minus the chlorine residual . In this case,
3.0 mg/L - 1.2 mg/L = 1.8 mg/L. This represents the amount of chlorine consumed by organic matter,
ammonia, and other reducing substances in the water.
4. Which of the following is the MOST important factor in determining the effectiveness of chlorine
disinfection in a water treatment plant?
A. The temperature of the water, as warmer water increases the reaction rate.
B. The pH of the water, which affects the speciation of chlorine and the formation of hypochlorous acid.
C. The turbidity of the water, which can shield microorganisms from chlorine.
D. The contact time and the concentration of free chlorine, as the CT value must be sufficient for the
target pathogen.
Correct Answer: D
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Rationale: The CT value (concentration × contact time) is the primary factor determining disinfection
effectiveness . Both the free chlorine concentration and the contact time must be sufficient to achieve
the required log reduction of pathogens.
5. In the coagulation and flocculation process, what is the primary purpose of adding a coagulant such
as alum (aluminum sulfate) to raw water, and what is the mechanism of action?
A. To increase the pH of the water; alum reacts with water to form hydroxide ions.
B. To neutralize the negative charge of suspended particles; alum forms positively charged aluminum
hydroxide flocs that attract and enmesh particles.
C. To disinfect the water; alum releases chlorine that kills bacteria.
D. To soften the water; alum reacts with calcium and magnesium ions to form precipitates.
Correct Answer: B
Rationale: The primary purpose of coagulation is to neutralize the negative surface charges of
suspended particles, allowing them to aggregate . Alum forms positively charged aluminum hydroxide
flocs that attract and enmesh negatively charged particles, which are then removed through
sedimentation and filtration.
6. A water treatment plant is required to maintain a chlorine residual of at least 0.5 mg/L throughout
the distribution system. What is the primary reason for this requirement, and what does a low
chlorine residual indicate?
California Water System/Treatment Operator Grade 2
(T2) Exam QUESTIONS AND CORRECT ANSWERS LATEST
UPDATE THIS YEAR
California Water System/Treatment Operator Grade 2 (T2) Exam
EXAM COVERAGE (Point Form)
• Fundamental Water Treatment Operations, Process Monitoring, Water Quality & Regulatory
Compliance (Core Exam Area)
• Drinking Water Regulations, Public Health & Regulatory Compliance
• Water Treatment Fundamentals
• Disinfection & Water Quality Control
• Plant Operations, Equipment & Process Monitoring
• Water Chemistry, Laboratory Analysis & Treatment Mathematics
• Distribution System Fundamentals
• Safety, Emergency Response & Risk Management
• Professional Responsibilities & Documentation
QUESTIONS 1-100
1. A water treatment plant operator notices that the turbidity of the finished water is increasing
despite the filters operating normally. Which of the following is the MOST likely cause of this increase
in turbidity, and what is the appropriate action to take?
A. The coagulant dosage is too high, causing floc carryover; the operator should decrease the coagulant
feed rate.
B. The filter media is becoming fouled; the operator should backwash the filters immediately.
C. A change in source water quality is affecting coagulation; the operator should perform jar tests to
determine the optimal coagulant dosage.
D. The pH of the water is too low; the operator should add lime to raise the pH.
, Page 2 of 157
Correct Answer: C
Rationale: A change in source water quality, such as increased turbidity or altered pH and alkalinity, can
affect coagulation efficiency and lead to increased turbidity in the finished water . The operator should
perform jar tests to determine the new optimal coagulant dosage for the current water quality
conditions.
2. Under California Title 22 drinking water regulations, which of the following is the primary purpose
of the Maximum Contaminant Level (MCL) for total coliform bacteria, and what does a positive total
coliform test indicate?
A. To ensure the water is free from all bacteria; a positive test indicates the water is unsafe to drink.
B. To serve as an indicator of potential fecal contamination and the possible presence of disease-causing
organisms; a positive test indicates a potential health risk that requires investigation.
C. To measure the effectiveness of the disinfection process; a positive test indicates the chlorine residual
is too low.
D. To monitor the turbidity of the water; a positive test indicates the filters are not working properly.
Correct Answer: B
Rationale: Total coliform bacteria are used as indicator organisms to signal the potential presence of
pathogenic organisms in drinking water . A positive total coliform test suggests possible fecal
contamination and requires immediate investigation and corrective action.
, Page 3 of 157
3. A water treatment operator is calculating the chlorine demand of a water sample. The chlorine
dose is 3.0 mg/L, and the chlorine residual after 30 minutes of contact time is 1.2 mg/L. What is the
chlorine demand of this water sample?
A. 1.2 mg/L
B. 1.8 mg/L
C. 3.0 mg/L
D. 4.2 mg/L
Correct Answer: B
Rationale: Chlorine demand is calculated as the chlorine dose minus the chlorine residual . In this case,
3.0 mg/L - 1.2 mg/L = 1.8 mg/L. This represents the amount of chlorine consumed by organic matter,
ammonia, and other reducing substances in the water.
4. Which of the following is the MOST important factor in determining the effectiveness of chlorine
disinfection in a water treatment plant?
A. The temperature of the water, as warmer water increases the reaction rate.
B. The pH of the water, which affects the speciation of chlorine and the formation of hypochlorous acid.
C. The turbidity of the water, which can shield microorganisms from chlorine.
D. The contact time and the concentration of free chlorine, as the CT value must be sufficient for the
target pathogen.
Correct Answer: D
, Page 4 of 157
Rationale: The CT value (concentration × contact time) is the primary factor determining disinfection
effectiveness . Both the free chlorine concentration and the contact time must be sufficient to achieve
the required log reduction of pathogens.
5. In the coagulation and flocculation process, what is the primary purpose of adding a coagulant such
as alum (aluminum sulfate) to raw water, and what is the mechanism of action?
A. To increase the pH of the water; alum reacts with water to form hydroxide ions.
B. To neutralize the negative charge of suspended particles; alum forms positively charged aluminum
hydroxide flocs that attract and enmesh particles.
C. To disinfect the water; alum releases chlorine that kills bacteria.
D. To soften the water; alum reacts with calcium and magnesium ions to form precipitates.
Correct Answer: B
Rationale: The primary purpose of coagulation is to neutralize the negative surface charges of
suspended particles, allowing them to aggregate . Alum forms positively charged aluminum hydroxide
flocs that attract and enmesh negatively charged particles, which are then removed through
sedimentation and filtration.
6. A water treatment plant is required to maintain a chlorine residual of at least 0.5 mg/L throughout
the distribution system. What is the primary reason for this requirement, and what does a low
chlorine residual indicate?
