1|Page
Nevada Wastewater Treatment Plant Operator – Grade II NEWEST
2026 ACTUAL EXAM TEST- COMPLETE REAL EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS (VERIFIED ANSWERS) ALREADY GRADED
A+ (MOST RECENT!!)
Practice Questions with Answers & Rationales
1. What is the primary purpose of primary clarification?
A. Remove dissolved organic matter
B. Remove settleable and floatable solids
C. Remove nutrients
D. Kill pathogens
Answer: B
Rationale:
Primary clarifiers are designed to remove settleable solids (sludge) and floatable materials
(scum) through gravity settling—not dissolved organics or pathogens.
2. What happens if sludge is allowed to accumulate too long in a primary clarifier?
A. Increased effluent quality
B. Reduced BOD removal
C. Septic conditions and odor problems
D. Improved settling
Answer: C
Rationale:
Excess sludge retention leads to anaerobic conditions, causing septic sludge, gas formation,
odors, and solids carryover.
2026 2027 GRADED A+
,2|Page
3. Which process primarily removes dissolved organic matter?
A. Screening
B. Grit removal
C. Secondary treatment
D. Disinfection
Answer: C
Rationale:
Secondary treatment (biological processes) removes dissolved and colloidal organic
material, measured as BOD.
4. What does BOD measure?
A. Total solids
B. Oxygen required to stabilize organic matter
C. Nitrogen concentration
D. Bacterial population
Answer: B
Rationale:
Biochemical Oxygen Demand (BOD) measures the amount of oxygen microorganisms need
to break down organic matter.
5. Low dissolved oxygen in an aeration basin will most likely cause:
A. Improved nitrification
B. Filament control
C. Poor BOD removal
D. Increased sludge settling
Answer: C
Rationale:
Low DO limits aerobic bacteria activity, resulting in poor organic removal and process upset.
2026 2027 GRADED A+
,3|Page
6. Typical dissolved oxygen level in an aeration basin should be:
A. 0.1 mg/L
B. 0.5 mg/L
C. 2.0 mg/L
D. 6.0 mg/L
Answer: C
Rationale:
Most activated sludge systems operate best at ~2.0 mg/L DO, providing adequate oxygen
without wasting energy.
7. What does MLSS represent?
A. Influent solids
B. Microorganisms in aeration basin
C. Settled sludge volume
D. Clarifier blanket depth
Answer: B
Rationale:
Mixed Liquor Suspended Solids (MLSS) represents the concentration of microorganisms in
the aeration tank.
8. High sludge blanket levels in secondary clarifiers can cause:
A. Improved effluent
B. Sludge washout
C. Increased disinfection
D. Lower turbidity
Answer: B
Rationale:
If the sludge blanket rises too high, solids can be carried over into the effluent, degrading water
quality.
2026 2027 GRADED A+
, 4|Page
9. What is the main function of Return Activated Sludge (RAS)?
A. Waste excess sludge
B. Maintain microorganism population
C. Increase flow rate
D. Remove grit
Answer: B
Rationale:
RAS returns settled biomass to the aeration basin to maintain adequate bacteria
concentration.
10. Waste Activated Sludge (WAS) is used to:
A. Increase MLSS
B. Remove excess microorganisms
C. Improve aeration
D. Increase settling time
Answer: B
Rationale:
WAS removes excess biomass to control sludge age and prevent overgrowth.
11. Which condition promotes filamentous bulking?
A. Adequate DO
B. Low F/M ratio
C. Low DO and nutrient imbalance
D. Proper sludge age
Answer: C
Rationale:
Low DO, low nutrients, and poor process control favor filamentous organisms that cause
bulking.
2026 2027 GRADED A+
Nevada Wastewater Treatment Plant Operator – Grade II NEWEST
2026 ACTUAL EXAM TEST- COMPLETE REAL EXAM QUESTIONS AND
CORRECT DETAILED ANSWERS (VERIFIED ANSWERS) ALREADY GRADED
A+ (MOST RECENT!!)
Practice Questions with Answers & Rationales
1. What is the primary purpose of primary clarification?
A. Remove dissolved organic matter
B. Remove settleable and floatable solids
C. Remove nutrients
D. Kill pathogens
Answer: B
Rationale:
Primary clarifiers are designed to remove settleable solids (sludge) and floatable materials
(scum) through gravity settling—not dissolved organics or pathogens.
2. What happens if sludge is allowed to accumulate too long in a primary clarifier?
A. Increased effluent quality
B. Reduced BOD removal
C. Septic conditions and odor problems
D. Improved settling
Answer: C
Rationale:
Excess sludge retention leads to anaerobic conditions, causing septic sludge, gas formation,
odors, and solids carryover.
2026 2027 GRADED A+
,2|Page
3. Which process primarily removes dissolved organic matter?
A. Screening
B. Grit removal
C. Secondary treatment
D. Disinfection
Answer: C
Rationale:
Secondary treatment (biological processes) removes dissolved and colloidal organic
material, measured as BOD.
4. What does BOD measure?
A. Total solids
B. Oxygen required to stabilize organic matter
C. Nitrogen concentration
D. Bacterial population
Answer: B
Rationale:
Biochemical Oxygen Demand (BOD) measures the amount of oxygen microorganisms need
to break down organic matter.
5. Low dissolved oxygen in an aeration basin will most likely cause:
A. Improved nitrification
B. Filament control
C. Poor BOD removal
D. Increased sludge settling
Answer: C
Rationale:
Low DO limits aerobic bacteria activity, resulting in poor organic removal and process upset.
2026 2027 GRADED A+
,3|Page
6. Typical dissolved oxygen level in an aeration basin should be:
A. 0.1 mg/L
B. 0.5 mg/L
C. 2.0 mg/L
D. 6.0 mg/L
Answer: C
Rationale:
Most activated sludge systems operate best at ~2.0 mg/L DO, providing adequate oxygen
without wasting energy.
7. What does MLSS represent?
A. Influent solids
B. Microorganisms in aeration basin
C. Settled sludge volume
D. Clarifier blanket depth
Answer: B
Rationale:
Mixed Liquor Suspended Solids (MLSS) represents the concentration of microorganisms in
the aeration tank.
8. High sludge blanket levels in secondary clarifiers can cause:
A. Improved effluent
B. Sludge washout
C. Increased disinfection
D. Lower turbidity
Answer: B
Rationale:
If the sludge blanket rises too high, solids can be carried over into the effluent, degrading water
quality.
2026 2027 GRADED A+
, 4|Page
9. What is the main function of Return Activated Sludge (RAS)?
A. Waste excess sludge
B. Maintain microorganism population
C. Increase flow rate
D. Remove grit
Answer: B
Rationale:
RAS returns settled biomass to the aeration basin to maintain adequate bacteria
concentration.
10. Waste Activated Sludge (WAS) is used to:
A. Increase MLSS
B. Remove excess microorganisms
C. Improve aeration
D. Increase settling time
Answer: B
Rationale:
WAS removes excess biomass to control sludge age and prevent overgrowth.
11. Which condition promotes filamentous bulking?
A. Adequate DO
B. Low F/M ratio
C. Low DO and nutrient imbalance
D. Proper sludge age
Answer: C
Rationale:
Low DO, low nutrients, and poor process control favor filamentous organisms that cause
bulking.
2026 2027 GRADED A+
