California Wastewater Treatment Operator Grade V
COMPLETE QUESTIONS AND DETAILED SOLUTIONS
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. SUMMARIZED EXAM COVERAGE
The Grade V exam focuses on advanced biological and chemical wastewater treatment control,
regulatory compliance (California NPDES rules), process optimization (activated sludge, nutrient
removal, solids handling), laboratory interpretation, hydraulics, and plant-wide troubleshooting
including safety and automation systems.
Q1
A wastewater plant shows rising effluent ammonia levels despite stable influent loading; what is the
most likely biological cause?
A. Excess chlorine in influent
B. Inhibited nitrification due to low dissolved oxygen
C. High sludge dewatering efficiency
D. Excess polymer dosing
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Answer: B
Rationale: Nitrifiers require adequate DO; low oxygen disrupts ammonia conversion.
Q2
A clarifier shows sludge rising and floating on the surface; what is the most likely operational issue?
A. Excess sludge wasting
B. Denitrification occurring in clarifier sludge blanket
C. High pump efficiency
D. Low influent flow
Answer: B
Rationale: Gas formation from denitrification causes sludge to float.
Q3
A plant experiences sludge bulking with poor settling; which organism is most commonly responsible?
A. Nocardia only
B. Filamentous bacteria overgrowth
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C. Protozoa dominance
D. Algae bloom
Answer: B
Rationale: Filamentous organisms cause poor settleability.
Q4
Mixed liquor suspended solids (MLSS) suddenly increases without change in influent load; what is the
most likely cause?
A. Reduced sludge wasting rate
B. Increased disinfection efficiency
C. Lower influent temperature
D. Increased UV exposure
Answer: A
Rationale: Less wasting increases solids accumulation.
Q5
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A plant experiences low dissolved oxygen in aeration tanks despite full blower operation; what is likely
issue?
A. Excess return sludge
B. Diffuser fouling or reduced aeration efficiency
C. High effluent quality
D. Low influent COD
Answer: B
Rationale: Fouled diffusers reduce oxygen transfer efficiency.
Q6
Which parameter best indicates sludge settling performance in activated sludge systems?
A. pH
B. Sludge Volume Index (SVI)
C. Chlorine residual
D. Turbidity only
Answer: B
Rationale: SVI measures sludge settleability.