Environmental Engineer Licensing Exam
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. An environmental engineer is designing a municipal drinking water
treatment facility. The raw water source has high turbidity caused
primarily by suspended clay particles. Which treatment process is
most appropriate as the initial major step to remove these particles?
A. Activated carbon adsorption
B. Coagulation and flocculation followed by sedimentation
C. Chlorination followed by aeration
D. Reverse osmosis membrane filtration
Correct Answer: B
,Coagulation and flocculation followed by sedimentation are used to
destabilize and aggregate suspended particles into larger flocs that can
settle out of water. This process is the conventional approach for removing
turbidity-causing materials such as clay and organic particles.
2. A wastewater treatment plant uses microorganisms to remove
biodegradable organic matter from sewage. The primary purpose of
measuring biochemical oxygen demand (BOD) is to determine:
A. The concentration of dissolved salts in wastewater
B. The amount of oxygen required by microorganisms to degrade organic
matter
C. The total amount of chlorine needed for disinfection
D. The concentration of toxic heavy metals in wastewater
Correct Answer: B
Biochemical oxygen demand measures the amount of dissolved oxygen
consumed by microorganisms during the decomposition of biodegradable
organic material. It is a key indicator of wastewater organic pollution
strength.
3. Which parameter is most commonly used to evaluate the oxygen-
demanding capacity of wastewater?
,A. BOD and chemical oxygen demand (COD)
B. pH and alkalinity only
C. Total dissolved solids only
D. Temperature and conductivity only
Correct Answer: A
BOD and COD quantify the amount of oxygen required to oxidize organic
contaminants in wastewater. COD measures chemically oxidizable
compounds, while BOD measures biologically degradable organic matter.
4. In activated sludge treatment, the mixed liquor suspended solids
(MLSS) concentration represents:
A. The concentration of microorganisms and suspended solids in the
aeration tank
B. The amount of chlorine residual in treated water
C. The concentration of dissolved oxygen entering the plant
D. The amount of nitrogen gas released during treatment
Correct Answer: A
MLSS represents the total suspended solids concentration in the aeration
basin, including microbial biomass responsible for degrading organic
pollutants.
, 5. A wastewater treatment plant experiences poor nitrification
performance. Which operational change would most likely improve
ammonia removal?
A. Decreasing aeration time
B. Increasing dissolved oxygen concentration and solids retention time
C. Eliminating biological treatment
D. Reducing microbial population
Correct Answer: B
Nitrifying bacteria require adequate oxygen and sufficient time to grow.
Increasing dissolved oxygen and solids retention time improves conditions
for ammonia-oxidizing microorganisms.
6. The main purpose of secondary wastewater treatment is to remove:
A. Large debris and grit
B. Dissolved and suspended biodegradable organic matter
C. Radioactive contaminants
D. Excess chlorine residual
Correct Answer: B
Secondary treatment uses biological processes to remove biodegradable
organic pollutants that remain after preliminary and primary treatment.
Practice Questions And Correct Answers
(Verified Answers) Plus Rationale 2026
Q&A| Instant Download Pdf
1. An environmental engineer is designing a municipal drinking water
treatment facility. The raw water source has high turbidity caused
primarily by suspended clay particles. Which treatment process is
most appropriate as the initial major step to remove these particles?
A. Activated carbon adsorption
B. Coagulation and flocculation followed by sedimentation
C. Chlorination followed by aeration
D. Reverse osmosis membrane filtration
Correct Answer: B
,Coagulation and flocculation followed by sedimentation are used to
destabilize and aggregate suspended particles into larger flocs that can
settle out of water. This process is the conventional approach for removing
turbidity-causing materials such as clay and organic particles.
2. A wastewater treatment plant uses microorganisms to remove
biodegradable organic matter from sewage. The primary purpose of
measuring biochemical oxygen demand (BOD) is to determine:
A. The concentration of dissolved salts in wastewater
B. The amount of oxygen required by microorganisms to degrade organic
matter
C. The total amount of chlorine needed for disinfection
D. The concentration of toxic heavy metals in wastewater
Correct Answer: B
Biochemical oxygen demand measures the amount of dissolved oxygen
consumed by microorganisms during the decomposition of biodegradable
organic material. It is a key indicator of wastewater organic pollution
strength.
3. Which parameter is most commonly used to evaluate the oxygen-
demanding capacity of wastewater?
,A. BOD and chemical oxygen demand (COD)
B. pH and alkalinity only
C. Total dissolved solids only
D. Temperature and conductivity only
Correct Answer: A
BOD and COD quantify the amount of oxygen required to oxidize organic
contaminants in wastewater. COD measures chemically oxidizable
compounds, while BOD measures biologically degradable organic matter.
4. In activated sludge treatment, the mixed liquor suspended solids
(MLSS) concentration represents:
A. The concentration of microorganisms and suspended solids in the
aeration tank
B. The amount of chlorine residual in treated water
C. The concentration of dissolved oxygen entering the plant
D. The amount of nitrogen gas released during treatment
Correct Answer: A
MLSS represents the total suspended solids concentration in the aeration
basin, including microbial biomass responsible for degrading organic
pollutants.
, 5. A wastewater treatment plant experiences poor nitrification
performance. Which operational change would most likely improve
ammonia removal?
A. Decreasing aeration time
B. Increasing dissolved oxygen concentration and solids retention time
C. Eliminating biological treatment
D. Reducing microbial population
Correct Answer: B
Nitrifying bacteria require adequate oxygen and sufficient time to grow.
Increasing dissolved oxygen and solids retention time improves conditions
for ammonia-oxidizing microorganisms.
6. The main purpose of secondary wastewater treatment is to remove:
A. Large debris and grit
B. Dissolved and suspended biodegradable organic matter
C. Radioactive contaminants
D. Excess chlorine residual
Correct Answer: B
Secondary treatment uses biological processes to remove biodegradable
organic pollutants that remain after preliminary and primary treatment.
