TEXAS WASTEWATER EXAMINATION
VERSIONS A AND B Actual Exam 2026/2027
Complete Questions and Verified Answers
Graded A Pass Guaranteed – A+ Graded
VERSION A
SECTION 1: WASTEWATER TREATMENT FUNDAMENTALS
(Questions 1–15)
Q1 (Version A)
A wastewater treatment plant must meet an NPDES permit limit of 30
mg/L BOD and 30 mg/L TSS. The plant's secondary treatment process
produces effluent with 25 mg/L BOD and 20 mg/L TSS. What is the
percent removal for BOD if the influent BOD is 200 mg/L?
A. 75%
B. 80%
C. 87.5% [CORRECT]
D. 90%
Rationale:
Percent removal = (Influent − Effluent) / Influent × 100
= (200 − 25) / 200 × 100
= × 100
= 87.5% (C).
Option A (75%) would correspond to a 50 mg/L effluent. Option B
(80%) would correspond to a 40 mg/L effluent. Option D (90%) would
correspond to a 20 mg/L effluent.
,Q2 (Version A)
Under the Clean Water Act, what is the primary purpose of the NPDES
permit program?
A. To fund wastewater treatment plant construction
B. To regulate point source discharges into waters of the United States
[CORRECT]
C. To establish drinking water standards
D. To control air emissions from treatment facilities
Rationale:
The National Pollutant Discharge Elimination System (NPDES) is the
primary mechanism under the Clean Water Act for regulating point
source discharges of pollutants into U.S. waters (B). While funding (A)
relates to SRF programs and drinking water (C) falls under the SDWA,
NPDES specifically targets water pollution from identifiable sources.
Q3 (Version A)
A treatment plant receives wastewater with the following characteristics:
temperature 25°C, color gray, odor musty, pH 7.2, BOD 220 mg/L,
TSS 240 mg/L. Which parameter indicates the organic strength of this
wastewater?
A. Temperature
B. pH
C. BOD [CORRECT]
D. TSS
Rationale:
Biochemical Oxygen Demand (BOD) measures the amount of oxygen
required by microorganisms to decompose organic matter, making it the
primary indicator of organic strength (C). While TSS (D) measures
,solids, not all solids are organic. Temperature (A) and pH (B) are
physical/chemical parameters but do not indicate organic content.
Q4 (Version A)
A municipality experiences significant flow variations between dry
weather (2.0 MGD) and wet weather (8.0 MGD) due to infiltration and
inflow (I/I). What is the primary concern with these extreme flow
variations?
A. Increased chlorine demand
B. Hydraulic overloading and reduced treatment efficiency
[CORRECT]
C. Improved settling in primary clarifiers
D. Enhanced biological treatment
Rationale:
Extreme flow variations cause hydraulic overloading, reducing detention
times in treatment units and potentially washing out biomass, leading to
treatment efficiency decline (B). While chlorine demand (A) may
increase, the primary concern is hydraulic impact. Flow variations
worsen (C), not improve, settling and stress (D), not enhance, biological
treatment.
Q5 (Version A)
An industrial facility discharges heavy metals into the sewer system.
Under TCEQ rules (30 TAC Chapter 319), what is this type of discharge
classified as?
A. Domestic wastewater
B. Industrial wastewater subject to pretreatment standards [CORRECT]
, C. Storm water runoff
D. Agricultural return flow
Rationale:
Industrial discharges containing heavy metals are subject to categorical
pretreatment standards under 30 TAC Chapter 319 to prevent
interference with treatment processes and pass-through of pollutants (B).
Domestic wastewater (A) excludes industrial pollutants, while storm
water (C) and agricultural flows (D) are separate categories.
Q6 (Version A)
Calculate the pounds of BOD entering a plant daily if the flow is 3.5
MGD and the influent BOD is 185 mg/L.
A. 4,398 lbs/day
B. 5,395 lbs/day [CORRECT]
C. 6,420 lbs/day
D. 7,215 lbs/day
Rationale:
Using the formula:
lbs/day = Flow (MGD) × Concentration (mg/L) × 8.34
= 3.5 × 185 × 8.34
= 5,395 lbs/day (B)
Common errors include omitting 8.34 (A: 647.5), using 8.0 instead of
8.34 (C: 5,180), or calculation errors (D).
VERSIONS A AND B Actual Exam 2026/2027
Complete Questions and Verified Answers
Graded A Pass Guaranteed – A+ Graded
VERSION A
SECTION 1: WASTEWATER TREATMENT FUNDAMENTALS
(Questions 1–15)
Q1 (Version A)
A wastewater treatment plant must meet an NPDES permit limit of 30
mg/L BOD and 30 mg/L TSS. The plant's secondary treatment process
produces effluent with 25 mg/L BOD and 20 mg/L TSS. What is the
percent removal for BOD if the influent BOD is 200 mg/L?
A. 75%
B. 80%
C. 87.5% [CORRECT]
D. 90%
Rationale:
Percent removal = (Influent − Effluent) / Influent × 100
= (200 − 25) / 200 × 100
= × 100
= 87.5% (C).
Option A (75%) would correspond to a 50 mg/L effluent. Option B
(80%) would correspond to a 40 mg/L effluent. Option D (90%) would
correspond to a 20 mg/L effluent.
,Q2 (Version A)
Under the Clean Water Act, what is the primary purpose of the NPDES
permit program?
A. To fund wastewater treatment plant construction
B. To regulate point source discharges into waters of the United States
[CORRECT]
C. To establish drinking water standards
D. To control air emissions from treatment facilities
Rationale:
The National Pollutant Discharge Elimination System (NPDES) is the
primary mechanism under the Clean Water Act for regulating point
source discharges of pollutants into U.S. waters (B). While funding (A)
relates to SRF programs and drinking water (C) falls under the SDWA,
NPDES specifically targets water pollution from identifiable sources.
Q3 (Version A)
A treatment plant receives wastewater with the following characteristics:
temperature 25°C, color gray, odor musty, pH 7.2, BOD 220 mg/L,
TSS 240 mg/L. Which parameter indicates the organic strength of this
wastewater?
A. Temperature
B. pH
C. BOD [CORRECT]
D. TSS
Rationale:
Biochemical Oxygen Demand (BOD) measures the amount of oxygen
required by microorganisms to decompose organic matter, making it the
primary indicator of organic strength (C). While TSS (D) measures
,solids, not all solids are organic. Temperature (A) and pH (B) are
physical/chemical parameters but do not indicate organic content.
Q4 (Version A)
A municipality experiences significant flow variations between dry
weather (2.0 MGD) and wet weather (8.0 MGD) due to infiltration and
inflow (I/I). What is the primary concern with these extreme flow
variations?
A. Increased chlorine demand
B. Hydraulic overloading and reduced treatment efficiency
[CORRECT]
C. Improved settling in primary clarifiers
D. Enhanced biological treatment
Rationale:
Extreme flow variations cause hydraulic overloading, reducing detention
times in treatment units and potentially washing out biomass, leading to
treatment efficiency decline (B). While chlorine demand (A) may
increase, the primary concern is hydraulic impact. Flow variations
worsen (C), not improve, settling and stress (D), not enhance, biological
treatment.
Q5 (Version A)
An industrial facility discharges heavy metals into the sewer system.
Under TCEQ rules (30 TAC Chapter 319), what is this type of discharge
classified as?
A. Domestic wastewater
B. Industrial wastewater subject to pretreatment standards [CORRECT]
, C. Storm water runoff
D. Agricultural return flow
Rationale:
Industrial discharges containing heavy metals are subject to categorical
pretreatment standards under 30 TAC Chapter 319 to prevent
interference with treatment processes and pass-through of pollutants (B).
Domestic wastewater (A) excludes industrial pollutants, while storm
water (C) and agricultural flows (D) are separate categories.
Q6 (Version A)
Calculate the pounds of BOD entering a plant daily if the flow is 3.5
MGD and the influent BOD is 185 mg/L.
A. 4,398 lbs/day
B. 5,395 lbs/day [CORRECT]
C. 6,420 lbs/day
D. 7,215 lbs/day
Rationale:
Using the formula:
lbs/day = Flow (MGD) × Concentration (mg/L) × 8.34
= 3.5 × 185 × 8.34
= 5,395 lbs/day (B)
Common errors include omitting 8.34 (A: 647.5), using 8.0 instead of
8.34 (C: 5,180), or calculation errors (D).
