TEXAS PROFESSIONAL ENGINEER
ENVIRONMENTAL ENGINEERING
LICENSING EXAM ACTUAL 2026 VERIFIED
QUESTIONS WITH ANSWERS
COMPREHENSIVE & RATIONALE|INSTANT
DOWNLOAD
1. Which federal law primarily regulates the discharge of pollutants
into waters of the United States through the National Pollutant
Discharge Elimination System (NPDES)?
A. Safe Drinking Water Act (SDWA)
B. Clean Water Act (CWA)
C. Resource Conservation and Recovery Act (RCRA)
D. Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA)
Answer: B. Clean Water Act (CWA)
Rationale: The Clean Water Act establishes the basic structure for
regulating pollutant discharges into surface waters. The NPDES
program requires permits for point-source discharges and sets effluent
limitations to protect water quality.
2. A wastewater treatment plant receives a flow of 2.5 MGD with a
BOD concentration of 220 mg/L. What is the approximate daily
BOD loading?
A. 2,500 lb/day
B. 4,590 lb/day
C. 6,200 lb/day
D. 9,800 lb/day
1
,Answer: B. 4,590 lb/day
Rationale: BOD loading is calculated as Q(MGD) ×
concentration(mg/L) × 8.34. Therefore: 2.5 × 220 × 8.34 =
approximately 4,587 lb/day. This conversion factor is used extensively
in environmental engineering calculations.
3. The primary purpose of a grit chamber in a wastewater treatment
facility is to remove:
A. Dissolved organic matter
B. Pathogenic organisms
C. Heavy inorganic particles
D. Nitrogen compounds
Answer: C. Heavy inorganic particles
Rationale: Grit chambers remove dense inorganic materials such as
sand, gravel, and small stones. These materials can damage pumps
and accumulate in downstream treatment units.
4. Which wastewater treatment process is responsible for the
majority of suspended solids removal?
A. Primary sedimentation
B. Chlorination
C. Aeration
D. Disinfection
Answer: A. Primary sedimentation
Rationale: Primary clarifiers remove settleable solids and floating
materials through gravity settling and typically remove approximately
50–70% of suspended solids before biological treatment.
2
,5. In an activated sludge process, the microorganisms responsible
for organic matter degradation are primarily located in:
A. The primary clarifier
B. The aeration basin
C. The chlorine contact tank
D. The sludge digester
Answer: B. The aeration basin
Rationale: The aeration basin provides oxygen and mixing conditions
necessary for microorganisms to consume biodegradable organic
matter and form biological flocs.
6. The main purpose of return activated sludge (RAS) is to:
A. Increase chlorine dosage
B. Maintain adequate microorganism concentration
C. Remove dissolved metals
D. Reduce influent flow
Answer: B. Maintain adequate microorganism concentration
Rationale: RAS returns settled biomass from the secondary clarifier
back to the aeration basin, maintaining the microorganism population
required for effective treatment.
7. A wastewater treatment plant has an MLSS concentration of
3,000 mg/L and an MLVSS concentration of 2,400 mg/L. What
percentage of MLSS is biologically active?
A. 20%
B. 40%
3
, C. 60%
D. 80%
Answer: D. 80%
Rationale: MLVSS/MLSS × 100 = 2,400/3,000 × 100 = 80%. MLVSS
represents the volatile organic fraction associated with active
microorganisms.
8. The sludge age in an activated sludge system is also known as:
A. Hydraulic retention time
B. Mean cell residence time
C. Detention period
D. Solids concentration ratio
Answer: B. Mean cell residence time
Rationale: Mean cell residence time (MCRT) represents the average
time microorganisms remain in the treatment system and controls
biological process stability.
9. A high food-to-microorganism (F/M) ratio generally indicates:
A. Excess microorganisms compared with available food
B. Insufficient organic loading
C. High organic loading relative to biomass
D. Complete nitrification
Answer: C. High organic loading relative to biomass
Rationale: The F/M ratio compares organic substrate available to
microorganisms. High values indicate more food is available per unit
of biomass, often causing rapid growth and possible poor settling.
4
ENVIRONMENTAL ENGINEERING
LICENSING EXAM ACTUAL 2026 VERIFIED
QUESTIONS WITH ANSWERS
COMPREHENSIVE & RATIONALE|INSTANT
DOWNLOAD
1. Which federal law primarily regulates the discharge of pollutants
into waters of the United States through the National Pollutant
Discharge Elimination System (NPDES)?
A. Safe Drinking Water Act (SDWA)
B. Clean Water Act (CWA)
C. Resource Conservation and Recovery Act (RCRA)
D. Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA)
Answer: B. Clean Water Act (CWA)
Rationale: The Clean Water Act establishes the basic structure for
regulating pollutant discharges into surface waters. The NPDES
program requires permits for point-source discharges and sets effluent
limitations to protect water quality.
2. A wastewater treatment plant receives a flow of 2.5 MGD with a
BOD concentration of 220 mg/L. What is the approximate daily
BOD loading?
A. 2,500 lb/day
B. 4,590 lb/day
C. 6,200 lb/day
D. 9,800 lb/day
1
,Answer: B. 4,590 lb/day
Rationale: BOD loading is calculated as Q(MGD) ×
concentration(mg/L) × 8.34. Therefore: 2.5 × 220 × 8.34 =
approximately 4,587 lb/day. This conversion factor is used extensively
in environmental engineering calculations.
3. The primary purpose of a grit chamber in a wastewater treatment
facility is to remove:
A. Dissolved organic matter
B. Pathogenic organisms
C. Heavy inorganic particles
D. Nitrogen compounds
Answer: C. Heavy inorganic particles
Rationale: Grit chambers remove dense inorganic materials such as
sand, gravel, and small stones. These materials can damage pumps
and accumulate in downstream treatment units.
4. Which wastewater treatment process is responsible for the
majority of suspended solids removal?
A. Primary sedimentation
B. Chlorination
C. Aeration
D. Disinfection
Answer: A. Primary sedimentation
Rationale: Primary clarifiers remove settleable solids and floating
materials through gravity settling and typically remove approximately
50–70% of suspended solids before biological treatment.
2
,5. In an activated sludge process, the microorganisms responsible
for organic matter degradation are primarily located in:
A. The primary clarifier
B. The aeration basin
C. The chlorine contact tank
D. The sludge digester
Answer: B. The aeration basin
Rationale: The aeration basin provides oxygen and mixing conditions
necessary for microorganisms to consume biodegradable organic
matter and form biological flocs.
6. The main purpose of return activated sludge (RAS) is to:
A. Increase chlorine dosage
B. Maintain adequate microorganism concentration
C. Remove dissolved metals
D. Reduce influent flow
Answer: B. Maintain adequate microorganism concentration
Rationale: RAS returns settled biomass from the secondary clarifier
back to the aeration basin, maintaining the microorganism population
required for effective treatment.
7. A wastewater treatment plant has an MLSS concentration of
3,000 mg/L and an MLVSS concentration of 2,400 mg/L. What
percentage of MLSS is biologically active?
A. 20%
B. 40%
3
, C. 60%
D. 80%
Answer: D. 80%
Rationale: MLVSS/MLSS × 100 = 2,400/3,000 × 100 = 80%. MLVSS
represents the volatile organic fraction associated with active
microorganisms.
8. The sludge age in an activated sludge system is also known as:
A. Hydraulic retention time
B. Mean cell residence time
C. Detention period
D. Solids concentration ratio
Answer: B. Mean cell residence time
Rationale: Mean cell residence time (MCRT) represents the average
time microorganisms remain in the treatment system and controls
biological process stability.
9. A high food-to-microorganism (F/M) ratio generally indicates:
A. Excess microorganisms compared with available food
B. Insufficient organic loading
C. High organic loading relative to biomass
D. Complete nitrification
Answer: C. High organic loading relative to biomass
Rationale: The F/M ratio compares organic substrate available to
microorganisms. High values indicate more food is available per unit
of biomass, often causing rapid growth and possible poor settling.
4
