CALIFORNIA WASTEWATER TREATMENT
OPERATOR GRADE V COMPLETE
QUESTIONS AND DETAILED SOLUTIONS
LATEST UPDATE THIS YEAR-JUST
RELEASED
Exam coverage
Control biological systems using MCRT, F/M, DO
Troubleshoot using microscopy + lab data trends
Maintain regulatory compliance (NPDES)
Optimize solids handling and digestion
Apply advanced math + process control logic
Respond to shock loads and system upsets
Understand nutrient removal deeply
Integrate SCADA + real-time monitoring
1.
,A plant maintains stable MLSS and DO (~2.5 mg/L), yet
effluent ammonia rises gradually over 5 days.
Temperature dropped from 20°C to 12°C. SRT remained
constant. What is the MOST appropriate operator
response?
A. Increase wasting to improve sludge activity
B. Increase SRT by reducing wasting
C. Increase DO to 5 mg/L
D. Add chlorine to control ammonia
Answer: B
Rationale: Trap: DO and SRT seem “adequate,” but
colder temperatures reduce nitrifier growth rates—
requiring higher SRT, not just stable SRT.
2.
An operator increases RAS to correct rising sludge
blanket, but effluent TSS worsens. MLSS increases
significantly. What is the MOST likely underlying issue?
A. Underloading of clarifier
B. Hydraulic overloading from excessive RAS
C. Low F/M ratio causing pin floc
D. Excess DO in aeration basin
Answer: B
Rationale: Trap: Increasing RAS helps blanket—but too
,much recycles solids + increases clarifier flow, worsening
washout.
3.
A plant shows good BOD removal but persistent high
nitrate in effluent. DO in aeration = 3 mg/L. Anoxic zone
exists but ORP remains positive. What is the MOST likely
cause?
A. Excess nitrification
B. Insufficient carbon source for denitrification
C. Low DO in aeration basin
D. High alkalinity
Answer: B
Rationale: Trap: Anoxic zone exists, but no carbon = no
denitrification, despite correct structure.
4.
After a storm event, influent flow triples. Effluent TSS
increases despite normal SVI and MLSS. What is the
PRIMARY cause?
A. Biological failure
B. Toxic shock
, C. Hydraulic overloading of clarifier
D. Low DO
Answer: C
Rationale: Trap: Biology looks fine—problem is hydraulic
capacity exceeded.
5.
An MBR system experiences rising transmembrane
pressure (TMP) with stable influent quality. What is the
BEST first operational response?
A. Increase aeration immediately
B. Perform membrane cleaning/backwash
C. Reduce MLSS drastically
D. Increase sludge age
Answer: B
Rationale: Trap: Operators may over-adjust biology, but
TMP rise = physical fouling first.
6.
A plant shows low SVI (~60 mL/g) but effluent TSS
remains high. What is the MOST likely explanation?
A. Bulking sludge
B. Pin floc causing poor capture
OPERATOR GRADE V COMPLETE
QUESTIONS AND DETAILED SOLUTIONS
LATEST UPDATE THIS YEAR-JUST
RELEASED
Exam coverage
Control biological systems using MCRT, F/M, DO
Troubleshoot using microscopy + lab data trends
Maintain regulatory compliance (NPDES)
Optimize solids handling and digestion
Apply advanced math + process control logic
Respond to shock loads and system upsets
Understand nutrient removal deeply
Integrate SCADA + real-time monitoring
1.
,A plant maintains stable MLSS and DO (~2.5 mg/L), yet
effluent ammonia rises gradually over 5 days.
Temperature dropped from 20°C to 12°C. SRT remained
constant. What is the MOST appropriate operator
response?
A. Increase wasting to improve sludge activity
B. Increase SRT by reducing wasting
C. Increase DO to 5 mg/L
D. Add chlorine to control ammonia
Answer: B
Rationale: Trap: DO and SRT seem “adequate,” but
colder temperatures reduce nitrifier growth rates—
requiring higher SRT, not just stable SRT.
2.
An operator increases RAS to correct rising sludge
blanket, but effluent TSS worsens. MLSS increases
significantly. What is the MOST likely underlying issue?
A. Underloading of clarifier
B. Hydraulic overloading from excessive RAS
C. Low F/M ratio causing pin floc
D. Excess DO in aeration basin
Answer: B
Rationale: Trap: Increasing RAS helps blanket—but too
,much recycles solids + increases clarifier flow, worsening
washout.
3.
A plant shows good BOD removal but persistent high
nitrate in effluent. DO in aeration = 3 mg/L. Anoxic zone
exists but ORP remains positive. What is the MOST likely
cause?
A. Excess nitrification
B. Insufficient carbon source for denitrification
C. Low DO in aeration basin
D. High alkalinity
Answer: B
Rationale: Trap: Anoxic zone exists, but no carbon = no
denitrification, despite correct structure.
4.
After a storm event, influent flow triples. Effluent TSS
increases despite normal SVI and MLSS. What is the
PRIMARY cause?
A. Biological failure
B. Toxic shock
, C. Hydraulic overloading of clarifier
D. Low DO
Answer: C
Rationale: Trap: Biology looks fine—problem is hydraulic
capacity exceeded.
5.
An MBR system experiences rising transmembrane
pressure (TMP) with stable influent quality. What is the
BEST first operational response?
A. Increase aeration immediately
B. Perform membrane cleaning/backwash
C. Reduce MLSS drastically
D. Increase sludge age
Answer: B
Rationale: Trap: Operators may over-adjust biology, but
TMP rise = physical fouling first.
6.
A plant shows low SVI (~60 mL/g) but effluent TSS
remains high. What is the MOST likely explanation?
A. Bulking sludge
B. Pin floc causing poor capture
