WASTEWATER OPERATOR LICENSING EXAMINER EXAM QUESTIONS
AND ANSWERS (VERIFIED ANSWERS) PLUS RATIONALE 2025/2026 Q&A/
INSTANDOWNLOAD PDF
1. What is the primary goal of wastewater treatment?
A. To remove pathogens only
B. To make water drinkable
C. To protect public health and the environment
D. To reduce temperature of water
The primary goal of wastewater treatment is to protect public health and the environment by
removing contaminants before discharge.
2. Which process removes settleable solids from wastewater?
A. Primary treatment
B. Secondary treatment
C. Tertiary treatment
D. Disinfection
Primary treatment uses sedimentation to remove large and settleable solids from raw
wastewater.
3. What is the main purpose of secondary treatment?
A. Remove floating materials
B. Remove suspended and dissolved organic matter
C. Neutralize acids
D. Remove heavy metals
Secondary treatment uses biological processes to remove organic matter not removed in primary
treatment.
,4. The activated sludge process depends primarily on which organisms?
A. Viruses
B. Bacteria
C. Protozoa
D. Algae
Bacteria are the main microorganisms that decompose organic matter in the activated sludge
process.
5. What is the typical detention time in a primary clarifier?
A. 5–10 minutes
B. 30 minutes
C. 1–2 hours
D. 4–6 hours
A detention time of 1–2 hours allows sufficient settling of solids.
6. The BOD test measures:
A. Suspended solids
B. Dissolved oxygen consumed by microorganisms
C. Chlorine demand
D. pH change
Biochemical Oxygen Demand (BOD) measures the oxygen used by bacteria to decompose
organic matter.
7. Which of the following best describes “sludge”?
A. Floating scum layer
B. Settleable solids collected at the bottom
C. Clear supernatant liquid
D. Disinfected effluent
Sludge is the solid material that settles at the bottom during sedimentation.
, 8. What is the main purpose of aeration in wastewater treatment?
A. To heat wastewater
B. To provide oxygen for biological activity
C. To remove oil and grease
D. To sterilize wastewater
Aeration supplies oxygen to support aerobic bacteria that break down organic matter.
9. Which test measures the strength of wastewater in terms of solids?
A. BOD
B. COD
C. Total Suspended Solids (TSS)
D. DO
TSS quantifies the amount of solid particles suspended in wastewater.
10. What is the typical pH range for biological treatment?
A. 2–4
B. 5–9
C. 10–12
D. 12–14
Most microorganisms thrive in a neutral to slightly basic range of 6.5–8.5.
11. Which process converts ammonia to nitrate?
A. Denitrification
B. Nitrification
C. Anaerobic digestion
D. Fermentation
Nitrification is the aerobic biological oxidation of ammonia to nitrate.
AND ANSWERS (VERIFIED ANSWERS) PLUS RATIONALE 2025/2026 Q&A/
INSTANDOWNLOAD PDF
1. What is the primary goal of wastewater treatment?
A. To remove pathogens only
B. To make water drinkable
C. To protect public health and the environment
D. To reduce temperature of water
The primary goal of wastewater treatment is to protect public health and the environment by
removing contaminants before discharge.
2. Which process removes settleable solids from wastewater?
A. Primary treatment
B. Secondary treatment
C. Tertiary treatment
D. Disinfection
Primary treatment uses sedimentation to remove large and settleable solids from raw
wastewater.
3. What is the main purpose of secondary treatment?
A. Remove floating materials
B. Remove suspended and dissolved organic matter
C. Neutralize acids
D. Remove heavy metals
Secondary treatment uses biological processes to remove organic matter not removed in primary
treatment.
,4. The activated sludge process depends primarily on which organisms?
A. Viruses
B. Bacteria
C. Protozoa
D. Algae
Bacteria are the main microorganisms that decompose organic matter in the activated sludge
process.
5. What is the typical detention time in a primary clarifier?
A. 5–10 minutes
B. 30 minutes
C. 1–2 hours
D. 4–6 hours
A detention time of 1–2 hours allows sufficient settling of solids.
6. The BOD test measures:
A. Suspended solids
B. Dissolved oxygen consumed by microorganisms
C. Chlorine demand
D. pH change
Biochemical Oxygen Demand (BOD) measures the oxygen used by bacteria to decompose
organic matter.
7. Which of the following best describes “sludge”?
A. Floating scum layer
B. Settleable solids collected at the bottom
C. Clear supernatant liquid
D. Disinfected effluent
Sludge is the solid material that settles at the bottom during sedimentation.
, 8. What is the main purpose of aeration in wastewater treatment?
A. To heat wastewater
B. To provide oxygen for biological activity
C. To remove oil and grease
D. To sterilize wastewater
Aeration supplies oxygen to support aerobic bacteria that break down organic matter.
9. Which test measures the strength of wastewater in terms of solids?
A. BOD
B. COD
C. Total Suspended Solids (TSS)
D. DO
TSS quantifies the amount of solid particles suspended in wastewater.
10. What is the typical pH range for biological treatment?
A. 2–4
B. 5–9
C. 10–12
D. 12–14
Most microorganisms thrive in a neutral to slightly basic range of 6.5–8.5.
11. Which process converts ammonia to nitrate?
A. Denitrification
B. Nitrification
C. Anaerobic digestion
D. Fermentation
Nitrification is the aerobic biological oxidation of ammonia to nitrate.
