Wastewater Treatment Operator
Certification Test #1 | Latest Update
2022/2023
Section 1: Wastewater Treatment Fundamentals (Questions 1–10)
Question 1: What is the primary purpose of secondary wastewater treatment? A) Removal
of large debris B) Biological reduction of organic matter C) Disinfection of pathogens D)
Chemical removal of metals
Correct Answer: B Rationale: Secondary treatment uses biological processes (e.g.,
activated sludge, trickling filters) to remove dissolved and colloidal organic matter. Primary
treatment (A) removes debris; disinfection (C) is tertiary; metal removal (D) requires advanced
treatment.
Question 2: Which of the following is a primary treatment process? A) Activated sludge B)
Trickling filter C) Sedimentation in a primary clarifier D) UV disinfection
Correct Answer: C Rationale: Primary clarifiers use sedimentation to remove settleable
solids. Activated sludge (A) and trickling filters (B) are secondary; UV (D) is disinfection.
Question 3: The activated sludge process relies on: A) Chemical precipitation B)
Microorganisms to consume organic waste C) Physical filtration D) UV radiation
Correct Answer: B Rationale: Activated sludge uses aerobic microorganisms to break down
organic matter. Chemical precipitation (A) is for phosphorus removal; filtration (C) is tertiary; UV
(D) is disinfection.
Question 4: Which of the following is NOT a component of a trickling filter system? A)
Distribution arms B) Media (e.g., rock or plastic) C) Chlorine contact tank D) Under-drain
system
, Correct Answer: C Rationale: A chlorine contact tank is used for disinfection, not trickling
filters. Distribution arms (A), media (B), and under-drains (D) are trickling filter components.
Question 5: The sludge volume index (SVI) measures: A) The pH of the sludge B) The
settleability of activated sludge C) The chemical oxygen demand (COD) of the sludge D) The
temperature of the sludge
Correct Answer: B Rationale: SVI indicates how well activated sludge settles in the clarifier.
pH (A), COD (C), and temperature (D) are unrelated to settleability.
Question 6: Which of the following is a common sludge treatment method? A) Anaerobic
digestion B) UV irradiation C) Reverse osmosis D) Ion exchange
Correct Answer: A Rationale: Anaerobic digestion stabilizes sludge by breaking down
organics. UV (B) is disinfection; reverse osmosis (C) and ion exchange (D) are advanced water
treatment, not sludge treatment.
Question 7: The primary function of a grit chamber is to remove: A) Dissolved organic matter
B) Heavy inorganic solids (e.g., sand, gravel) C) Colloidal particles D) Pathogenic bacteria
Correct Answer: B Rationale: Grit chambers remove heavy inorganic solids to protect
downstream equipment. Dissolved organics (A) are removed biologically; colloids (C) require
coagulation; pathogens (D) are addressed in disinfection.
Question 8: Which of the following is a secondary clarifier’s primary role? A) Removing grit B)
Separating biomass from treated effluent C) Adding chlorine D) Neutralizing pH
Correct Answer: B Rationale: Secondary clarifiers separate biomass (activated sludge)
from treated water. Grit removal (A) is primary; chlorination (C) is disinfection; pH adjustment (D)
is chemical treatment.
Question 9: The return activated sludge (RAS) pump sends sludge from the: A) Primary
clarifier to the aeration tank B) Secondary clarifier to the aeration tank C) Aeration tank to the
primary clarifier D) Digester to the secondary clarifier
Correct Answer: B Rationale: RAS recycles settled sludge from the secondary clarifier back
to the aeration tank to maintain biomass. Other routes (A, C, D) are incorrect process flows.
Certification Test #1 | Latest Update
2022/2023
Section 1: Wastewater Treatment Fundamentals (Questions 1–10)
Question 1: What is the primary purpose of secondary wastewater treatment? A) Removal
of large debris B) Biological reduction of organic matter C) Disinfection of pathogens D)
Chemical removal of metals
Correct Answer: B Rationale: Secondary treatment uses biological processes (e.g.,
activated sludge, trickling filters) to remove dissolved and colloidal organic matter. Primary
treatment (A) removes debris; disinfection (C) is tertiary; metal removal (D) requires advanced
treatment.
Question 2: Which of the following is a primary treatment process? A) Activated sludge B)
Trickling filter C) Sedimentation in a primary clarifier D) UV disinfection
Correct Answer: C Rationale: Primary clarifiers use sedimentation to remove settleable
solids. Activated sludge (A) and trickling filters (B) are secondary; UV (D) is disinfection.
Question 3: The activated sludge process relies on: A) Chemical precipitation B)
Microorganisms to consume organic waste C) Physical filtration D) UV radiation
Correct Answer: B Rationale: Activated sludge uses aerobic microorganisms to break down
organic matter. Chemical precipitation (A) is for phosphorus removal; filtration (C) is tertiary; UV
(D) is disinfection.
Question 4: Which of the following is NOT a component of a trickling filter system? A)
Distribution arms B) Media (e.g., rock or plastic) C) Chlorine contact tank D) Under-drain
system
, Correct Answer: C Rationale: A chlorine contact tank is used for disinfection, not trickling
filters. Distribution arms (A), media (B), and under-drains (D) are trickling filter components.
Question 5: The sludge volume index (SVI) measures: A) The pH of the sludge B) The
settleability of activated sludge C) The chemical oxygen demand (COD) of the sludge D) The
temperature of the sludge
Correct Answer: B Rationale: SVI indicates how well activated sludge settles in the clarifier.
pH (A), COD (C), and temperature (D) are unrelated to settleability.
Question 6: Which of the following is a common sludge treatment method? A) Anaerobic
digestion B) UV irradiation C) Reverse osmosis D) Ion exchange
Correct Answer: A Rationale: Anaerobic digestion stabilizes sludge by breaking down
organics. UV (B) is disinfection; reverse osmosis (C) and ion exchange (D) are advanced water
treatment, not sludge treatment.
Question 7: The primary function of a grit chamber is to remove: A) Dissolved organic matter
B) Heavy inorganic solids (e.g., sand, gravel) C) Colloidal particles D) Pathogenic bacteria
Correct Answer: B Rationale: Grit chambers remove heavy inorganic solids to protect
downstream equipment. Dissolved organics (A) are removed biologically; colloids (C) require
coagulation; pathogens (D) are addressed in disinfection.
Question 8: Which of the following is a secondary clarifier’s primary role? A) Removing grit B)
Separating biomass from treated effluent C) Adding chlorine D) Neutralizing pH
Correct Answer: B Rationale: Secondary clarifiers separate biomass (activated sludge)
from treated water. Grit removal (A) is primary; chlorination (C) is disinfection; pH adjustment (D)
is chemical treatment.
Question 9: The return activated sludge (RAS) pump sends sludge from the: A) Primary
clarifier to the aeration tank B) Secondary clarifier to the aeration tank C) Aeration tank to the
primary clarifier D) Digester to the secondary clarifier
Correct Answer: B Rationale: RAS recycles settled sludge from the secondary clarifier back
to the aeration tank to maintain biomass. Other routes (A, C, D) are incorrect process flows.
