Wastewater Class B License Exam Questions
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Rationales 2025/2026 Q&A | Instant
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1. Which of the following is the primary goal of a wastewater
treatment plant?
A. Generate electricity
B. Remove pollutants from wastewater
C. Produce drinking water
D. Control stormwater
Wastewater treatment plants are designed to remove physical,
chemical, and biological contaminants before discharge.
2. BOD stands for:
A. Biological Oxygen Demand
B. Basic Oxidation Determination
C. Biochemical Oxygen Demand
D. Bacterial Oxidation Dose
BOD measures the amount of oxygen required by
microorganisms to decompose organic matter in water.
3. Which process removes large solids from wastewater?
A. Filtration
B. Disinfection
C. Screening
D. Chlorination
Screening physically removes rags, sticks, and large debris that
could damage equipment.
4. The function of a grit chamber is to:
A. Remove bacteria
B. Settle sand and heavy particles
, C. Clarify effluent
D. Aerate wastewater
Grit chambers slow flow, allowing sand and heavy inorganic
solids to settle.
5. Which microorganism is primarily responsible for BOD removal
in secondary treatment?
A. Viruses
B. Protozoa
C. Bacteria
D. Fungi
Bacteria consume organic matter, reducing BOD in secondary
treatment.
6. In activated sludge systems, what is returned to maintain
biological activity?
A. Chlorine
B. Return activated sludge (RAS)
C. Effluent
D. Grit
RAS recycles microorganisms to maintain a healthy population
for wastewater treatment.
7. Which type of wastewater treatment is primarily physical?
A. Trickling filter
B. Activated sludge
C. Primary treatment
D. Anaerobic digestion
Primary treatment focuses on settling and screening without
biological processes.
8. What is the purpose of chlorination?
A. Settle solids
B. Disinfect effluent
C. Remove nitrogen
, D. Increase BOD
Chlorination kills or inactivates pathogens before discharge.
9. A common cause of sludge bulking is:
A. High chlorine residual
B. Filamentous bacteria overgrowth
C. Excess aeration
D. High pH
Filamentous bacteria prevent sludge from settling properly,
causing bulking.
10. Which unit process reduces nitrogen via biological
nitrification?
A. Primary clarifier
B. Aeration basin
C. Grit chamber
D. Chlorination tank
Nitrifying bacteria in aeration basins convert ammonia to
nitrate.
11. What does TSS stand for in wastewater analysis?
A. Total Suspended Solids
B. Total Sediment Sample
C. Total Suspended Solids
D. Total Soluble Substances
TSS measures the amount of suspended solids in the water.
12. What is the minimum pH range typically maintained in
activated sludge systems?
A. 2–4
B. 4–5
C. 6.5–8.5
D. 9–10
Bacteria in activated sludge are most effective within a neutral
pH range.
And Correct Answers (Verified Answers) Plus
Rationales 2025/2026 Q&A | Instant
Download Pdf
1. Which of the following is the primary goal of a wastewater
treatment plant?
A. Generate electricity
B. Remove pollutants from wastewater
C. Produce drinking water
D. Control stormwater
Wastewater treatment plants are designed to remove physical,
chemical, and biological contaminants before discharge.
2. BOD stands for:
A. Biological Oxygen Demand
B. Basic Oxidation Determination
C. Biochemical Oxygen Demand
D. Bacterial Oxidation Dose
BOD measures the amount of oxygen required by
microorganisms to decompose organic matter in water.
3. Which process removes large solids from wastewater?
A. Filtration
B. Disinfection
C. Screening
D. Chlorination
Screening physically removes rags, sticks, and large debris that
could damage equipment.
4. The function of a grit chamber is to:
A. Remove bacteria
B. Settle sand and heavy particles
, C. Clarify effluent
D. Aerate wastewater
Grit chambers slow flow, allowing sand and heavy inorganic
solids to settle.
5. Which microorganism is primarily responsible for BOD removal
in secondary treatment?
A. Viruses
B. Protozoa
C. Bacteria
D. Fungi
Bacteria consume organic matter, reducing BOD in secondary
treatment.
6. In activated sludge systems, what is returned to maintain
biological activity?
A. Chlorine
B. Return activated sludge (RAS)
C. Effluent
D. Grit
RAS recycles microorganisms to maintain a healthy population
for wastewater treatment.
7. Which type of wastewater treatment is primarily physical?
A. Trickling filter
B. Activated sludge
C. Primary treatment
D. Anaerobic digestion
Primary treatment focuses on settling and screening without
biological processes.
8. What is the purpose of chlorination?
A. Settle solids
B. Disinfect effluent
C. Remove nitrogen
, D. Increase BOD
Chlorination kills or inactivates pathogens before discharge.
9. A common cause of sludge bulking is:
A. High chlorine residual
B. Filamentous bacteria overgrowth
C. Excess aeration
D. High pH
Filamentous bacteria prevent sludge from settling properly,
causing bulking.
10. Which unit process reduces nitrogen via biological
nitrification?
A. Primary clarifier
B. Aeration basin
C. Grit chamber
D. Chlorination tank
Nitrifying bacteria in aeration basins convert ammonia to
nitrate.
11. What does TSS stand for in wastewater analysis?
A. Total Suspended Solids
B. Total Sediment Sample
C. Total Suspended Solids
D. Total Soluble Substances
TSS measures the amount of suspended solids in the water.
12. What is the minimum pH range typically maintained in
activated sludge systems?
A. 2–4
B. 4–5
C. 6.5–8.5
D. 9–10
Bacteria in activated sludge are most effective within a neutral
pH range.
