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California Wastewater Treatment Operator Grade
V exam COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR-JUST
RELEASED
Summarized Exam Coverage – CA Wastewater Treatment Operator Grade V
The California Grade V Wastewater Treatment Operator exam is the advanced certification for plant
managers and senior operators. It covers advanced process control (activated sludge variations, MBBR,
MBR, advanced nutrient removal, process optimization), complex troubleshooting (bulking, foaming,
toxicity upsets, process microbiology), process modeling and energy management, advanced
laboratory procedures (GC/MS, BOD/COD correlation, metals analysis), advanced disinfection (UV
intensity monitoring, ozone generation, chlorination/dechlorination optimization), advanced solids
handling (anaerobic digestion optimization, co-digestion, thermal hydrolysis, advanced dewatering,
biosolids regulations), advanced instrumentation (SCADA, PLC programming, data analytics, online
analyzers), project management (capital improvement planning, construction supervision,
budgeting), advanced safety (H2S monitoring, confined space rescue, hazardous materials, process
safety management), regulatory compliance (Title 22 reuse standards, NPDES permitting, basin plan
requirements, enforcement actions), and advanced plant management (staff training, asset
management, emergency response planning). Eligibility: 7 years of experience (6 years with degree) and
passing the Grade V exam beyond Grade IV.
1. An activated sludge plant is experiencing severe foaming that is not controlled by increasing wasting
or reducing MCRT. Microscopic examination reveals Nocardia filaments. What is the most effective
targeted control strategy for Nocardia foam?
A) Chlorination of the return activated sludge (RAS) at a low dose for a short duration
B) Addition of polymer to the aeration basin
C) Increasing the aeration basin DO to 4.0 mg/L
D) Reducing the influent BOD by bypassing primary clarifiers
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Answer: A — Low-dose RAS chlorination (or peroxidation) selectively knocks back Nocardia without
destroying floc-forming bacteria.
2. A plant with a trickling filter/solids contact (TF/SC) process is experiencing high effluent TSS. The
operator notices that the contact basin has a very short detention time (20 minutes) and the mixed
liquor is highly dispersed. What is the most likely cause of the high TSS?
A) Overload of the trickling filter, leading to excessive sloughing and inadequate flocculation in the
contact basin
B) Low dissolved oxygen in the contact basin
C) Excessive wasting of the solids contact basin sludge
D) High recycle rate causing short-circuiting
*Answer: A — In TF/SC, the contact basin requires sufficient time (30-60 minutes) to allow
bioflocculation of the sloughed filter solids; lack of flocculation leads to high effluent TSS.*
3. A membrane bioreactor (MBR) plant is experiencing a rapid increase in transmembrane pressure
(TMP). The operator checks the mixed liquor and finds it has a high viscosity and a dark, septic
appearance. What is the most probable cause of the TMP increase?
A) Biological foaming in the membrane tank
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B) High MLSS concentration causing sludge de-flocculation and polymer slime release, fouling the
membranes
C) Low DO leading to nitrification inhibition
D) Excessive air scour flow rate
Answer: B — High MLSS or septic conditions can cause release of extracellular polymeric substances
(EPS) and increased viscosity, which rapidly foul membranes.
4. A plant uses an aerobic digester to stabilize waste activated sludge. The operator notes that the
volatile solids reduction (VSR) has dropped below 30% and the sludge is difficult to dewater. What is the
most likely cause, and what should the operator do?
A) The digester is overloaded; reduce the feed rate or add a thickener to increase feed solids
concentration
B) The temperature is too high; aerate less
C) The digester pH is too low; add lime
D) The operator is wasting too much sludge; increase the wasting rate
Answer: A — Aerobic digesters require adequate detention time; overloading reduces VSR and increases
dewatering difficulty.
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5. A plant is upgrading to meet stringent effluent total nitrogen (TN) limits (<3 mg/L). The existing
activated sludge plant has an anoxic zone for denitrification but cannot achieve the required TN. What is
the most common advanced process addition to enhance TN removal?
A) Adding a post-anoxic zone with internal recirculation and a supplemental carbon source
B) Increasing the aeration basin DO to 4 mg/L to promote nitrification
C) Converting the aeration basin to anoxic operation
D) Adding primary clarifiers to remove BOD before the anoxic zone
Answer: A — Post-anoxic denitrification with carbon addition (methanol, glycerol, or acetate) is often
required for very low TN limits.
6. A Grade V operator is reviewing the plant's energy consumption. The largest energy user is the
aeration system. What is the most effective energy-saving measure for a conventional activated sludge
plant?
A) Installing high-speed turbo blowers with VFDs and DO control loops
B) Running the aeration system at full capacity 24/7
C) Switching from fine bubble to coarse bubble diffusers
D) Adding more surface aerators
California Wastewater Treatment Operator Grade
V exam COMPLETE QUESTIONS AND DETAILED
SOLUTIONS LATEST UPDATE THIS YEAR-JUST
RELEASED
Summarized Exam Coverage – CA Wastewater Treatment Operator Grade V
The California Grade V Wastewater Treatment Operator exam is the advanced certification for plant
managers and senior operators. It covers advanced process control (activated sludge variations, MBBR,
MBR, advanced nutrient removal, process optimization), complex troubleshooting (bulking, foaming,
toxicity upsets, process microbiology), process modeling and energy management, advanced
laboratory procedures (GC/MS, BOD/COD correlation, metals analysis), advanced disinfection (UV
intensity monitoring, ozone generation, chlorination/dechlorination optimization), advanced solids
handling (anaerobic digestion optimization, co-digestion, thermal hydrolysis, advanced dewatering,
biosolids regulations), advanced instrumentation (SCADA, PLC programming, data analytics, online
analyzers), project management (capital improvement planning, construction supervision,
budgeting), advanced safety (H2S monitoring, confined space rescue, hazardous materials, process
safety management), regulatory compliance (Title 22 reuse standards, NPDES permitting, basin plan
requirements, enforcement actions), and advanced plant management (staff training, asset
management, emergency response planning). Eligibility: 7 years of experience (6 years with degree) and
passing the Grade V exam beyond Grade IV.
1. An activated sludge plant is experiencing severe foaming that is not controlled by increasing wasting
or reducing MCRT. Microscopic examination reveals Nocardia filaments. What is the most effective
targeted control strategy for Nocardia foam?
A) Chlorination of the return activated sludge (RAS) at a low dose for a short duration
B) Addition of polymer to the aeration basin
C) Increasing the aeration basin DO to 4.0 mg/L
D) Reducing the influent BOD by bypassing primary clarifiers
, Page 2 of 106
Answer: A — Low-dose RAS chlorination (or peroxidation) selectively knocks back Nocardia without
destroying floc-forming bacteria.
2. A plant with a trickling filter/solids contact (TF/SC) process is experiencing high effluent TSS. The
operator notices that the contact basin has a very short detention time (20 minutes) and the mixed
liquor is highly dispersed. What is the most likely cause of the high TSS?
A) Overload of the trickling filter, leading to excessive sloughing and inadequate flocculation in the
contact basin
B) Low dissolved oxygen in the contact basin
C) Excessive wasting of the solids contact basin sludge
D) High recycle rate causing short-circuiting
*Answer: A — In TF/SC, the contact basin requires sufficient time (30-60 minutes) to allow
bioflocculation of the sloughed filter solids; lack of flocculation leads to high effluent TSS.*
3. A membrane bioreactor (MBR) plant is experiencing a rapid increase in transmembrane pressure
(TMP). The operator checks the mixed liquor and finds it has a high viscosity and a dark, septic
appearance. What is the most probable cause of the TMP increase?
A) Biological foaming in the membrane tank
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B) High MLSS concentration causing sludge de-flocculation and polymer slime release, fouling the
membranes
C) Low DO leading to nitrification inhibition
D) Excessive air scour flow rate
Answer: B — High MLSS or septic conditions can cause release of extracellular polymeric substances
(EPS) and increased viscosity, which rapidly foul membranes.
4. A plant uses an aerobic digester to stabilize waste activated sludge. The operator notes that the
volatile solids reduction (VSR) has dropped below 30% and the sludge is difficult to dewater. What is the
most likely cause, and what should the operator do?
A) The digester is overloaded; reduce the feed rate or add a thickener to increase feed solids
concentration
B) The temperature is too high; aerate less
C) The digester pH is too low; add lime
D) The operator is wasting too much sludge; increase the wasting rate
Answer: A — Aerobic digesters require adequate detention time; overloading reduces VSR and increases
dewatering difficulty.
, Page 4 of 106
5. A plant is upgrading to meet stringent effluent total nitrogen (TN) limits (<3 mg/L). The existing
activated sludge plant has an anoxic zone for denitrification but cannot achieve the required TN. What is
the most common advanced process addition to enhance TN removal?
A) Adding a post-anoxic zone with internal recirculation and a supplemental carbon source
B) Increasing the aeration basin DO to 4 mg/L to promote nitrification
C) Converting the aeration basin to anoxic operation
D) Adding primary clarifiers to remove BOD before the anoxic zone
Answer: A — Post-anoxic denitrification with carbon addition (methanol, glycerol, or acetate) is often
required for very low TN limits.
6. A Grade V operator is reviewing the plant's energy consumption. The largest energy user is the
aeration system. What is the most effective energy-saving measure for a conventional activated sludge
plant?
A) Installing high-speed turbo blowers with VFDs and DO control loops
B) Running the aeration system at full capacity 24/7
C) Switching from fine bubble to coarse bubble diffusers
D) Adding more surface aerators
