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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 =
175/200 × 100 = 87.5% (C). Option A (75%) would be 50 mg/L effluent. Option B (80%) would
be 40 mg/L effluent. Option D (90%) would be 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
SDWA, NPDES specifically targets water pollution from identifiable sources.
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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 don't 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.
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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 lbs/gal =
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).
Q7 (Version A): What is the primary biological health concern associated with untreated
wastewater containing pathogenic organisms?
A. Nutrient enrichment of receiving waters
B. Transmission of waterborne diseases to humans [CORRECT]
C. Oxygen depletion in the atmosphere
D. Formation of disinfection byproducts
Rationale: Pathogenic bacteria, viruses, protozoa, and helminths in wastewater pose direct
public health risks through waterborne disease transmission (B). While nutrients (A) and oxygen
depletion are environmental concerns, pathogen control primarily protects human health. DBPs
(D) result from disinfection, not raw wastewater.
Q8 (Version A): A plant's influent contains 45 mg/L total nitrogen and 8 mg/L total phosphorus.
According to typical municipal wastewater characteristics, what nutrient ratio concern exists?
A. The nitrogen-to-phosphorus ratio is optimal for biological treatment
B. Phosphorus may be limiting for biological treatment [CORRECT]
C. Nitrogen may be limiting for biological treatment
D. The ratio indicates industrial contamination
Rationale: The N:P ratio is 45:8 or approximately 5.6:1. Biological treatment typically requires
BOD:N:P of 100:5:1 or N:P around 5:1 to 10:1. However, with BOD typically 200 mg/L, the
ratio would be 200:45:8 or roughly 25:5.6:1, suggesting phosphorus may be slightly limiting (B).
Industrial contamination (D) would show different patterns.
Q9 (Version A): Under TCEQ regulations, which class of wastewater operator certification
allows an operator to make process control decisions at a Class B activated sludge facility?
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A. Class D
B. Class C
C. Class B [CORRECT]
D. Class A
Rationale: Class B certification is required to operate Class B facilities and make independent
process control decisions at that level (C). Class D (A) is entry-level requiring supervision, Class
C (B) operates Class C facilities, and Class A (D) is for the most complex facilities and
supervisory roles.
Q10 (Version A): A wastewater sample shows the following: settleable solids 8 mL/L, total
solids 850 mg/L, suspended solids 320 mg/L. What is the approximate dissolved solids
concentration?
A. 320 mg/L
B. 530 mg/L [CORRECT]
C. 850 mg/L
D. 1,170 mg/L
Rationale: Total Solids = Dissolved Solids + Suspended Solids. Therefore, Dissolved Solids =
850 - 320 = 530 mg/L (B). Option A is suspended solids, C is total solids, and D incorrectly adds
instead of subtracts.
Q11 (Version A): What is the primary purpose of secondary treatment as defined by EPA
standards?
A. Removal of grit and debris
B. Removal of settleable solids
C. Removal of 85% of BOD and TSS or achieve 30/30 effluent quality [CORRECT]
D. Removal of nutrients
Rationale: Secondary treatment standards require plants to achieve 85% removal of BOD and
TSS OR meet 30 mg/L BOD and 30 mg/L TSS monthly averages (C). Primary treatment (A, B)
removes larger solids and settleable material, while nutrient removal (D) constitutes
advanced/tertiary treatment.
Q12 (Version A): An operator measures the following in raw wastewater: COD 450 mg/L, BOD
220 mg/L. What does the COD/BOD ratio indicate?
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 =
175/200 × 100 = 87.5% (C). Option A (75%) would be 50 mg/L effluent. Option B (80%) would
be 40 mg/L effluent. Option D (90%) would be 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
SDWA, NPDES specifically targets water pollution from identifiable sources.
,2
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 don't 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.
,3
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 lbs/gal =
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).
Q7 (Version A): What is the primary biological health concern associated with untreated
wastewater containing pathogenic organisms?
A. Nutrient enrichment of receiving waters
B. Transmission of waterborne diseases to humans [CORRECT]
C. Oxygen depletion in the atmosphere
D. Formation of disinfection byproducts
Rationale: Pathogenic bacteria, viruses, protozoa, and helminths in wastewater pose direct
public health risks through waterborne disease transmission (B). While nutrients (A) and oxygen
depletion are environmental concerns, pathogen control primarily protects human health. DBPs
(D) result from disinfection, not raw wastewater.
Q8 (Version A): A plant's influent contains 45 mg/L total nitrogen and 8 mg/L total phosphorus.
According to typical municipal wastewater characteristics, what nutrient ratio concern exists?
A. The nitrogen-to-phosphorus ratio is optimal for biological treatment
B. Phosphorus may be limiting for biological treatment [CORRECT]
C. Nitrogen may be limiting for biological treatment
D. The ratio indicates industrial contamination
Rationale: The N:P ratio is 45:8 or approximately 5.6:1. Biological treatment typically requires
BOD:N:P of 100:5:1 or N:P around 5:1 to 10:1. However, with BOD typically 200 mg/L, the
ratio would be 200:45:8 or roughly 25:5.6:1, suggesting phosphorus may be slightly limiting (B).
Industrial contamination (D) would show different patterns.
Q9 (Version A): Under TCEQ regulations, which class of wastewater operator certification
allows an operator to make process control decisions at a Class B activated sludge facility?
, 4
A. Class D
B. Class C
C. Class B [CORRECT]
D. Class A
Rationale: Class B certification is required to operate Class B facilities and make independent
process control decisions at that level (C). Class D (A) is entry-level requiring supervision, Class
C (B) operates Class C facilities, and Class A (D) is for the most complex facilities and
supervisory roles.
Q10 (Version A): A wastewater sample shows the following: settleable solids 8 mL/L, total
solids 850 mg/L, suspended solids 320 mg/L. What is the approximate dissolved solids
concentration?
A. 320 mg/L
B. 530 mg/L [CORRECT]
C. 850 mg/L
D. 1,170 mg/L
Rationale: Total Solids = Dissolved Solids + Suspended Solids. Therefore, Dissolved Solids =
850 - 320 = 530 mg/L (B). Option A is suspended solids, C is total solids, and D incorrectly adds
instead of subtracts.
Q11 (Version A): What is the primary purpose of secondary treatment as defined by EPA
standards?
A. Removal of grit and debris
B. Removal of settleable solids
C. Removal of 85% of BOD and TSS or achieve 30/30 effluent quality [CORRECT]
D. Removal of nutrients
Rationale: Secondary treatment standards require plants to achieve 85% removal of BOD and
TSS OR meet 30 mg/L BOD and 30 mg/L TSS monthly averages (C). Primary treatment (A, B)
removes larger solids and settleable material, while nutrient removal (D) constitutes
advanced/tertiary treatment.
Q12 (Version A): An operator measures the following in raw wastewater: COD 450 mg/L, BOD
220 mg/L. What does the COD/BOD ratio indicate?
