Kansas Wastewater Operator Class IV Practice Exam
Questions And 100% Correct Answers (Verified
Answers) Plus Rationales | Latest Update 2026/2027 |
Graded A+.
1. What is the primary purpose of preliminary treatment in a wastewater
treatment plant?
A. To remove dissolved nutrients
B. To reduce biological oxygen demand (BOD)
C. To remove large solids and debris
D. To disinfect wastewater
Rationale: Preliminary treatment removes large solids and debris to protect
downstream equipment and processes.
2. Which process is used to remove suspended solids from wastewater
after preliminary treatment?
A. Chlorination
B. Trickling filter
C. Aeration
D. Primary sedimentation
Rationale: Primary sedimentation allows suspended solids to settle out by
gravity, reducing solids load on secondary treatment.
3. Biological treatment in an activated sludge process primarily removes:
,A. Heavy metals
B. Organic matter (BOD)
C. Phosphates
D. Pathogens
Rationale: Activated sludge uses microorganisms to consume organic
matter, effectively reducing BOD.
5. What is the typical purpose of chlorination in wastewater treatment?
A. Remove nutrients
B. Remove solids
C. Disinfect wastewater
D. Reduce pH
Rationale: Chlorination kills pathogenic microorganisms, ensuring
wastewater is safe before discharge.
6. Nitrification is the biological oxidation of:
A. Ammonia to nitrate
B. Nitrate to ammonia
C. Nitrite to ammonia
D. Ammonia to nitrite and then nitrate
Rationale: Nitrification occurs in two steps: ammonia is first oxidized to
nitrite, then to nitrate by nitrifying bacteria.
7. Denitrification converts nitrate into:
A. Ammonia
B. Nitrogen gas (N₂)
C. Nitrite
,D. Nitrous oxide
Rationale: Denitrifying bacteria convert nitrate to nitrogen gas under
anoxic conditions, removing nitrogen from wastewater.
8. Which microorganism is primarily responsible for nitrification?
A. Escherichia coli
B. Saccharomyces
C. Nitrosomonas
D. Clostridium
Rationale: Nitrosomonas bacteria oxidize ammonia to nitrite, a key step in
nitrification.
9. Which of the following methods is used to remove phosphorus from
wastewater?
A. Aeration
B. Chemical precipitation with alum or ferric chloride
C. Chlorination
D. Filtration
Rationale: Chemical precipitation binds phosphate into insoluble forms,
which can then settle out in primary or secondary treatment.
10. In trickling filter systems, microorganisms grow on:
A. Suspended flocs
B. Media surfaces (biofilm)
C. Sand beds
D. Activated sludge
, Rationale: Trickling filters rely on a biofilm on media surfaces to degrade
organic matter as wastewater flows over them.
4. In wastewater treatment, the term “BOD” stands for:
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Basic Oxygen Difference
D. Biological Organic Deposition
Rationale: BOD measures the amount of oxygen microorganisms consume
while decomposing organic matter in wastewater.
11. The main advantage of extended aeration over conventional activated
sludge is:
A. Lower oxygen requirement
B. Reduced sludge production
C. Higher nutrient removal
D. Faster treatment
Rationale: Extended aeration stabilizes organic matter for longer,
producing less sludge than conventional activated sludge systems.
12. What is the primary purpose of sludge thickening?
A. Disinfect sludge
B. Reduce water content before digestion or dewatering
C. Increase BOD removal
D. Aerate the sludge
Questions And 100% Correct Answers (Verified
Answers) Plus Rationales | Latest Update 2026/2027 |
Graded A+.
1. What is the primary purpose of preliminary treatment in a wastewater
treatment plant?
A. To remove dissolved nutrients
B. To reduce biological oxygen demand (BOD)
C. To remove large solids and debris
D. To disinfect wastewater
Rationale: Preliminary treatment removes large solids and debris to protect
downstream equipment and processes.
2. Which process is used to remove suspended solids from wastewater
after preliminary treatment?
A. Chlorination
B. Trickling filter
C. Aeration
D. Primary sedimentation
Rationale: Primary sedimentation allows suspended solids to settle out by
gravity, reducing solids load on secondary treatment.
3. Biological treatment in an activated sludge process primarily removes:
,A. Heavy metals
B. Organic matter (BOD)
C. Phosphates
D. Pathogens
Rationale: Activated sludge uses microorganisms to consume organic
matter, effectively reducing BOD.
5. What is the typical purpose of chlorination in wastewater treatment?
A. Remove nutrients
B. Remove solids
C. Disinfect wastewater
D. Reduce pH
Rationale: Chlorination kills pathogenic microorganisms, ensuring
wastewater is safe before discharge.
6. Nitrification is the biological oxidation of:
A. Ammonia to nitrate
B. Nitrate to ammonia
C. Nitrite to ammonia
D. Ammonia to nitrite and then nitrate
Rationale: Nitrification occurs in two steps: ammonia is first oxidized to
nitrite, then to nitrate by nitrifying bacteria.
7. Denitrification converts nitrate into:
A. Ammonia
B. Nitrogen gas (N₂)
C. Nitrite
,D. Nitrous oxide
Rationale: Denitrifying bacteria convert nitrate to nitrogen gas under
anoxic conditions, removing nitrogen from wastewater.
8. Which microorganism is primarily responsible for nitrification?
A. Escherichia coli
B. Saccharomyces
C. Nitrosomonas
D. Clostridium
Rationale: Nitrosomonas bacteria oxidize ammonia to nitrite, a key step in
nitrification.
9. Which of the following methods is used to remove phosphorus from
wastewater?
A. Aeration
B. Chemical precipitation with alum or ferric chloride
C. Chlorination
D. Filtration
Rationale: Chemical precipitation binds phosphate into insoluble forms,
which can then settle out in primary or secondary treatment.
10. In trickling filter systems, microorganisms grow on:
A. Suspended flocs
B. Media surfaces (biofilm)
C. Sand beds
D. Activated sludge
, Rationale: Trickling filters rely on a biofilm on media surfaces to degrade
organic matter as wastewater flows over them.
4. In wastewater treatment, the term “BOD” stands for:
A. Biological Oxidation Demand
B. Biochemical Oxygen Demand
C. Basic Oxygen Difference
D. Biological Organic Deposition
Rationale: BOD measures the amount of oxygen microorganisms consume
while decomposing organic matter in wastewater.
11. The main advantage of extended aeration over conventional activated
sludge is:
A. Lower oxygen requirement
B. Reduced sludge production
C. Higher nutrient removal
D. Faster treatment
Rationale: Extended aeration stabilizes organic matter for longer,
producing less sludge than conventional activated sludge systems.
12. What is the primary purpose of sludge thickening?
A. Disinfect sludge
B. Reduce water content before digestion or dewatering
C. Increase BOD removal
D. Aerate the sludge
