Wastewater Treatment Operator
Certification Test #2 | 2022/2023 Quiz
Section 1: Wastewater Processes (10 Questions)
1. Primary Treatment Purpose
The primary purpose of primary treatment in wastewater is to: A) Remove dissolved organic
matter B) Remove settleable solids and floating materials C) Disinfect the wastewater D)
Reduce nitrogen levels
Correct Answer: B) Remove settleable solids and floating materials Rationale:
● Primary treatment uses sedimentation and screening to remove solids and scum.
● A) Incorrect: Dissolved organics are removed in secondary treatment.
● C) Incorrect: Disinfection occurs in tertiary treatment.
● D) Incorrect: Nitrogen reduction happens in secondary/tertiary processes.
2. Activated Sludge Process
In the activated sludge process, microorganisms consume organic matter in the: A) Primary
clarifier B) Aeration tank C) Secondary clarifier D) Digester
Correct Answer: B) Aeration tank Rationale:
● Aeration tanks provide oxygen and mixing for microbial growth.
● A, C, D) Incorrect: These units do not aerate or support microbial growth.
3. Trickling Filter Media
The primary purpose of media in a trickling filter is to: A) Filter out large solids B) Provide
surface area for biofilm growth C) Disinfect the wastewater D) Store sludge
Correct Answer: B) Provide surface area for biofilm growth Rationale:
, ● Biofilm on media breaks down organics as wastewater trickles through.
● A, C, D) Incorrect: These are not the primary functions of trickling filter media.
4. Rotating Biological Contactors (RBCs)
RBCs are most effective for treating wastewater with: A) High heavy metal concentrations B)
Moderate organic loading C) High pH levels D) Low dissolved oxygen
Correct Answer: B) Moderate organic loading Rationale:
● RBCs thrive with moderate BOD and require oxygen for biofilm activity.
● A, C, D) Incorrect: Heavy metals, extreme pH, or low DO inhibit microbial activity.
5. Secondary Clarifier Function
The secondary clarifier in an activated sludge system is designed to: A) Aerate the wastewater
B) Separate biomass from treated effluent C) Add chemicals for coagulation D) Digest
sludge
Correct Answer: B) Separate biomass from treated effluent Rationale:
● Settling separates activated sludge (biomass) from clarified effluent.
● A, C, D) Incorrect: These are not functions of a secondary clarifier.
6. Aeration System DO
The optimal dissolved oxygen (DO) range in an aeration tank is typically: A) 0.5–1.0 mg/L B)
1.5–2.5 mg/L C) 3.0–4.0 mg/L D) 5.0–6.0 mg/L
Correct Answer: B) 1.5–2.5 mg/L Rationale:
● DO below 1.5 mg/L limits microbial activity; above 2.5 mg/L wastes energy.
● A, C, D) Incorrect: Too low or high for efficient treatment.
7. Tertiary Treatment Goal
The primary goal of tertiary treatment is to: A) Remove grit B) Further polish effluent for
reuse or discharge C) Thicken sludge D) Increase BOD
Certification Test #2 | 2022/2023 Quiz
Section 1: Wastewater Processes (10 Questions)
1. Primary Treatment Purpose
The primary purpose of primary treatment in wastewater is to: A) Remove dissolved organic
matter B) Remove settleable solids and floating materials C) Disinfect the wastewater D)
Reduce nitrogen levels
Correct Answer: B) Remove settleable solids and floating materials Rationale:
● Primary treatment uses sedimentation and screening to remove solids and scum.
● A) Incorrect: Dissolved organics are removed in secondary treatment.
● C) Incorrect: Disinfection occurs in tertiary treatment.
● D) Incorrect: Nitrogen reduction happens in secondary/tertiary processes.
2. Activated Sludge Process
In the activated sludge process, microorganisms consume organic matter in the: A) Primary
clarifier B) Aeration tank C) Secondary clarifier D) Digester
Correct Answer: B) Aeration tank Rationale:
● Aeration tanks provide oxygen and mixing for microbial growth.
● A, C, D) Incorrect: These units do not aerate or support microbial growth.
3. Trickling Filter Media
The primary purpose of media in a trickling filter is to: A) Filter out large solids B) Provide
surface area for biofilm growth C) Disinfect the wastewater D) Store sludge
Correct Answer: B) Provide surface area for biofilm growth Rationale:
, ● Biofilm on media breaks down organics as wastewater trickles through.
● A, C, D) Incorrect: These are not the primary functions of trickling filter media.
4. Rotating Biological Contactors (RBCs)
RBCs are most effective for treating wastewater with: A) High heavy metal concentrations B)
Moderate organic loading C) High pH levels D) Low dissolved oxygen
Correct Answer: B) Moderate organic loading Rationale:
● RBCs thrive with moderate BOD and require oxygen for biofilm activity.
● A, C, D) Incorrect: Heavy metals, extreme pH, or low DO inhibit microbial activity.
5. Secondary Clarifier Function
The secondary clarifier in an activated sludge system is designed to: A) Aerate the wastewater
B) Separate biomass from treated effluent C) Add chemicals for coagulation D) Digest
sludge
Correct Answer: B) Separate biomass from treated effluent Rationale:
● Settling separates activated sludge (biomass) from clarified effluent.
● A, C, D) Incorrect: These are not functions of a secondary clarifier.
6. Aeration System DO
The optimal dissolved oxygen (DO) range in an aeration tank is typically: A) 0.5–1.0 mg/L B)
1.5–2.5 mg/L C) 3.0–4.0 mg/L D) 5.0–6.0 mg/L
Correct Answer: B) 1.5–2.5 mg/L Rationale:
● DO below 1.5 mg/L limits microbial activity; above 2.5 mg/L wastes energy.
● A, C, D) Incorrect: Too low or high for efficient treatment.
7. Tertiary Treatment Goal
The primary goal of tertiary treatment is to: A) Remove grit B) Further polish effluent for
reuse or discharge C) Thicken sludge D) Increase BOD
