California Wastewater Treatment Operator Grade V
COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR-JUST
RELEASED.pdf
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
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
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
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.
,Q7
A facility must meet a monthly average effluent ammonia limit of 2 mg/L as N.
Which process control is most critical?
A. Maintaining aerobic conditions with sufficient SRT
B. Increasing primary clarifier weir loading
C. Adding more ferric chloride
D. Reducing return activated sludge flow
Answer: A
Rationale:-Nitrification requires adequate DO and SRT for nitrifier growth.
Q8
During a plant inspection, you observe dark brown foam in the aeration basin.
What does this indicate?
A. Old sludge
B. Young sludge with high F/M
C. Denitrification
D. High DO
Answer: B
Rationale:-Dark brown foam often indicates a young, active sludge with high
food-to-microorganism ratio.
Q9
Which NPDES reporting requirement applies to a California POTW with a major
discharge permit?
A. Annual report only
B. Monthly Discharge Monitoring Reports (DMRs)
C. Quarterly self-certification only
D. No reporting if compliant
Answer: B
Rationale:-Major facilities submit monthly DMRs to the Regional Water Board.
Q10
A plant uses biological phosphorus removal. Which zone is essential?
A. Anaerobic zone prior to aeration
, B. Post-aeration chlorine contact tank
C. Effluent polishing pond
D. Gravity thickener
Answer: A
Rationale:-Anaerobic zone selects for PAOs that uptake phosphorus under aerobic
conditions.
Q11
Sludge Volume Index (SVI) is calculated as:
A. (MLSS / SV30) × 1000
B. (SV30 / MLSS) × 1000
C. (MLVSS / MLSS) × 100
D. (TSS / VSS) × 100
Answer: B
Rationale:-SVI = (Settled sludge volume in mL/L after 30 min) / (MLSS in mg/L)
× 1000.
Q12
A pumping system operates at 1800 rpm delivering 1000 gpm. If speed increases
to 2000 rpm, what is new flow?
A. 900 gpm
B. 1111 gpm
C. 1200 gpm
D. 1000 gpm
Answer: B
Rationale:-Flow is proportional to speed: (2000/1800) × 1000 = 1111 gpm.
Q13
Which organism indicates good, stable activated sludge with long SRT?
A. Amoebae
B. Stalked ciliates (e.g., Opercularia)
C. Free-swimming ciliates
D. Flagellates
COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR-JUST
RELEASED.pdf
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
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
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
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.
,Q7
A facility must meet a monthly average effluent ammonia limit of 2 mg/L as N.
Which process control is most critical?
A. Maintaining aerobic conditions with sufficient SRT
B. Increasing primary clarifier weir loading
C. Adding more ferric chloride
D. Reducing return activated sludge flow
Answer: A
Rationale:-Nitrification requires adequate DO and SRT for nitrifier growth.
Q8
During a plant inspection, you observe dark brown foam in the aeration basin.
What does this indicate?
A. Old sludge
B. Young sludge with high F/M
C. Denitrification
D. High DO
Answer: B
Rationale:-Dark brown foam often indicates a young, active sludge with high
food-to-microorganism ratio.
Q9
Which NPDES reporting requirement applies to a California POTW with a major
discharge permit?
A. Annual report only
B. Monthly Discharge Monitoring Reports (DMRs)
C. Quarterly self-certification only
D. No reporting if compliant
Answer: B
Rationale:-Major facilities submit monthly DMRs to the Regional Water Board.
Q10
A plant uses biological phosphorus removal. Which zone is essential?
A. Anaerobic zone prior to aeration
, B. Post-aeration chlorine contact tank
C. Effluent polishing pond
D. Gravity thickener
Answer: A
Rationale:-Anaerobic zone selects for PAOs that uptake phosphorus under aerobic
conditions.
Q11
Sludge Volume Index (SVI) is calculated as:
A. (MLSS / SV30) × 1000
B. (SV30 / MLSS) × 1000
C. (MLVSS / MLSS) × 100
D. (TSS / VSS) × 100
Answer: B
Rationale:-SVI = (Settled sludge volume in mL/L after 30 min) / (MLSS in mg/L)
× 1000.
Q12
A pumping system operates at 1800 rpm delivering 1000 gpm. If speed increases
to 2000 rpm, what is new flow?
A. 900 gpm
B. 1111 gpm
C. 1200 gpm
D. 1000 gpm
Answer: B
Rationale:-Flow is proportional to speed: (2000/1800) × 1000 = 1111 gpm.
Q13
Which organism indicates good, stable activated sludge with long SRT?
A. Amoebae
B. Stalked ciliates (e.g., Opercularia)
C. Free-swimming ciliates
D. Flagellates
