FLORIDA BOARD OF PROFESSIONAL
ENGINEERS FUNDAMENTALS OF
ENGINEERING ENVIRONMENTAL EXAM
WITH ACTUAL QUESTIONS AND VERIFIED
ANSWERS, PLUS EXPLAINED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED 100% PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
1. Environmental Mass Balance — Steady-State Reactor
A completely mixed wastewater treatment reactor receives a flow of 2.0
MGD containing a conservative contaminant at a concentration of 80
mg/L. The reactor has a volume of 1.0 million gallons. The treated
effluent leaves at the same flow rate and is assumed to be completely
mixed. There is no decay, generation, or removal other than discharge.
What is the steady-state contaminant concentration in the reactor?
A. 20 mg/L
B. 40 mg/L
C. 80 mg/L
D. 160 mg/L
Answer: C. 80 mg/L
Rationale: At steady state for a conservative constituent, accumulation
is zero and there is no reaction or removal. Therefore, mass entering
must equal mass leaving: QCin=QCout. Since the flow entering equals
the flow leaving, Cout=Cin=80 mg/L. The reactor volume affects the
hydraulic residence time but does not change the steady-state
concentration when there is no reaction.
1
,2. Hydraulic Retention Time
A wastewater treatment basin has a volume of 1.5 million gallons and
receives an average flow of 0.50 MGD. What is the hydraulic retention
time?
A. 0.33 day
B. 1.0 day
C. 3.0 days
D. 7.5 days
Answer: C. 3.0 days
Rationale: Hydraulic retention time is t=V/Q. Thus,
t=(1.5 million gal)/(0.50 million gal/day)=3.0 days. The units of million
gallons cancel, leaving days.
3. BOD Removal
A wastewater treatment plant receives 10,000 m³/day with an influent
BOD concentration of 250 mg/L. The plant produces an effluent BOD
concentration of 25 mg/L. What is the percentage BOD removal?
A. 80%
B. 85%
C. 90%
D. 95%
Answer: C. 90%
Rationale: Percent removal is CiCi−Ce×100. Therefore, 250250−25
×100=90%. Flow is unnecessary because the same flow is assumed for
influent and effluent; the percentage concentration reduction equals
the percentage mass removal under these conditions.
2
,4. Ultimate Carbonaceous BOD
A wastewater has an ultimate carbonaceous BOD of 300 mg/L. If the
first-order BOD reaction constant is 0.23 day⁻¹, what is the approximate
BOD exerted after 5 days?
Use:
BODt=L0(1−e−kt)
A. 150 mg/L
B. 203 mg/L
C. 265 mg/L
D. 300 mg/L
Answer: B. 203 mg/L
Rationale: Substituting the values gives BOD5=300[1−e−(0.23)(5)].
The exponent is −1.15, and e−1.15≈0.316. Therefore, BOD5
≈300(1−0.316)=205 mg/L, approximately 203–205 mg/L depending on
rounding.
5. Dissolved Oxygen Sag
A river receives an organic waste discharge that substantially increases
the biochemical oxygen demand. Which process is primarily responsible
for lowering dissolved oxygen downstream?
A. Photosynthetic oxygen production
B. Microbial oxidation of biodegradable organic matter
C. Atmospheric nitrogen fixation
D. Sedimentation of inorganic solids
Answer: B. Microbial oxidation of biodegradable organic matter
3
, Rationale: Heterotrophic microorganisms consume dissolved oxygen
while oxidizing biodegradable organic material. This deoxygenation
can create a dissolved-oxygen sag downstream from a discharge.
Reaeration from the atmosphere and photosynthesis can subsequently
replenish oxygen, while sedimentation alone does not directly cause
the principal oxygen depletion mechanism.
6. Water Chlorination
A water treatment facility applies chlorine to water to achieve
disinfection. Which factor generally has the greatest direct influence on
chlorine disinfection effectiveness?
A. Water color only
B. Contact time and disinfectant concentration
C. Pipe diameter only
D. Total alkalinity only
Answer: B. Contact time and disinfectant concentration
Rationale: Chlorine disinfection effectiveness is strongly related to the
disinfectant concentration and the time available for contact. The
product CT, concentration multiplied by contact time, is commonly
used when evaluating disinfection performance. Temperature, pH,
organism type, and water quality also influence effectiveness.
7. Chlorine Demand
A treatment plant adds 5.0 mg/L of chlorine to raw water. After the
required contact period, the measured chlorine residual is 1.5 mg/L.
What is the chlorine demand?
A. 1.5 mg/L
B. 2.5 mg/L
4
ENGINEERS FUNDAMENTALS OF
ENGINEERING ENVIRONMENTAL EXAM
WITH ACTUAL QUESTIONS AND VERIFIED
ANSWERS, PLUS EXPLAINED
RATIONALES/EXPERT VERIFIED FOR
GUARANTEED 100% PASS 2026/LATEST
UPDATE/INSTANT DOWNLOAD PDF
1. Environmental Mass Balance — Steady-State Reactor
A completely mixed wastewater treatment reactor receives a flow of 2.0
MGD containing a conservative contaminant at a concentration of 80
mg/L. The reactor has a volume of 1.0 million gallons. The treated
effluent leaves at the same flow rate and is assumed to be completely
mixed. There is no decay, generation, or removal other than discharge.
What is the steady-state contaminant concentration in the reactor?
A. 20 mg/L
B. 40 mg/L
C. 80 mg/L
D. 160 mg/L
Answer: C. 80 mg/L
Rationale: At steady state for a conservative constituent, accumulation
is zero and there is no reaction or removal. Therefore, mass entering
must equal mass leaving: QCin=QCout. Since the flow entering equals
the flow leaving, Cout=Cin=80 mg/L. The reactor volume affects the
hydraulic residence time but does not change the steady-state
concentration when there is no reaction.
1
,2. Hydraulic Retention Time
A wastewater treatment basin has a volume of 1.5 million gallons and
receives an average flow of 0.50 MGD. What is the hydraulic retention
time?
A. 0.33 day
B. 1.0 day
C. 3.0 days
D. 7.5 days
Answer: C. 3.0 days
Rationale: Hydraulic retention time is t=V/Q. Thus,
t=(1.5 million gal)/(0.50 million gal/day)=3.0 days. The units of million
gallons cancel, leaving days.
3. BOD Removal
A wastewater treatment plant receives 10,000 m³/day with an influent
BOD concentration of 250 mg/L. The plant produces an effluent BOD
concentration of 25 mg/L. What is the percentage BOD removal?
A. 80%
B. 85%
C. 90%
D. 95%
Answer: C. 90%
Rationale: Percent removal is CiCi−Ce×100. Therefore, 250250−25
×100=90%. Flow is unnecessary because the same flow is assumed for
influent and effluent; the percentage concentration reduction equals
the percentage mass removal under these conditions.
2
,4. Ultimate Carbonaceous BOD
A wastewater has an ultimate carbonaceous BOD of 300 mg/L. If the
first-order BOD reaction constant is 0.23 day⁻¹, what is the approximate
BOD exerted after 5 days?
Use:
BODt=L0(1−e−kt)
A. 150 mg/L
B. 203 mg/L
C. 265 mg/L
D. 300 mg/L
Answer: B. 203 mg/L
Rationale: Substituting the values gives BOD5=300[1−e−(0.23)(5)].
The exponent is −1.15, and e−1.15≈0.316. Therefore, BOD5
≈300(1−0.316)=205 mg/L, approximately 203–205 mg/L depending on
rounding.
5. Dissolved Oxygen Sag
A river receives an organic waste discharge that substantially increases
the biochemical oxygen demand. Which process is primarily responsible
for lowering dissolved oxygen downstream?
A. Photosynthetic oxygen production
B. Microbial oxidation of biodegradable organic matter
C. Atmospheric nitrogen fixation
D. Sedimentation of inorganic solids
Answer: B. Microbial oxidation of biodegradable organic matter
3
, Rationale: Heterotrophic microorganisms consume dissolved oxygen
while oxidizing biodegradable organic material. This deoxygenation
can create a dissolved-oxygen sag downstream from a discharge.
Reaeration from the atmosphere and photosynthesis can subsequently
replenish oxygen, while sedimentation alone does not directly cause
the principal oxygen depletion mechanism.
6. Water Chlorination
A water treatment facility applies chlorine to water to achieve
disinfection. Which factor generally has the greatest direct influence on
chlorine disinfection effectiveness?
A. Water color only
B. Contact time and disinfectant concentration
C. Pipe diameter only
D. Total alkalinity only
Answer: B. Contact time and disinfectant concentration
Rationale: Chlorine disinfection effectiveness is strongly related to the
disinfectant concentration and the time available for contact. The
product CT, concentration multiplied by contact time, is commonly
used when evaluating disinfection performance. Temperature, pH,
organism type, and water quality also influence effectiveness.
7. Chlorine Demand
A treatment plant adds 5.0 mg/L of chlorine to raw water. After the
required contact period, the measured chlorine residual is 1.5 mg/L.
What is the chlorine demand?
A. 1.5 mg/L
B. 2.5 mg/L
4
