TCEQ WASTEWATER CLASS D LICENSE PREP ACTUAL EXAM
2026/2027 | QUESTIONS WITH CORRECT ANSWERS |
COMPREHENSIVE PRACTICE TEST ALIGNED WITH TCEQ CLASS
D WASTEWATER OPERATOR CERTIFICATION BLUEPRINT |
PASS GUARANTEED - A+ GRADED
TCEQ WASTEWATER CLASS D LICENSE PREP
SECTION 1: BASIC WASTEWATER TREATMENT CONCEPTS (35 Questions)
Q1: BOD (Biochemical Oxygen Demand) measures which characteristic of
wastewater?
A. The amount of oxygen required to stabilize organic matter
B. The total suspended solids concentration
C. The pH level of the wastewater
D. The chlorine residual
Correct Answer: A. Rationale: BOD measures the amount of oxygen
microorganisms require to decompose organic matter in wastewater over a
specified time (typically 5 days at 20°C), indicating organic strength.
Q2: Which wastewater source typically has the highest strength in terms of BOD
and solids?
A. Residential households
B. Restaurants and food processing
C. Stormwater runoff
D. Cooling water discharge
Correct Answer: B. Rationale: Commercial and industrial sources such as
restaurants and food processing facilities generate wastewater with significantly
higher organic loading (BOD) and solids concentrations compared to typical
domestic wastewater.
Q3: What is the typical BOD concentration range for domestic wastewater?
A. 10-50 mg/L
1
,B. 100-300 mg/L
C. 500-800 mg/L
D. 1000-2000 mg/L
Correct Answer: B. Rationale: Domestic wastewater typically contains BOD
concentrations ranging from 100-300 mg/L, with 200 mg/L being a common
average value.
Q4: COD (Chemical Oxygen Demand) differs from BOD primarily because:
A. COD measures only inorganic compounds
B. COD measures both biodegradable and non-biodegradable organic matter
C. COD is always lower than BOD
D. COD measures oxygen demand over 30 days
Correct Answer: B. Rationale: COD measures the total oxygen equivalent of all
organic matter that can be chemically oxidized, including both biodegradable and
non-biodegradable substances, while BOD only measures biodegradable organic
matter.
Q5: The ratio of BOD to COD in domestic wastewater is typically:
A. 0.1-0.2
B. 0.3-0.5
C. 0.5-0.8
D. 0.9-1.0
Correct Answer: C. Rationale: The BOD/COD ratio for domestic wastewater
typically ranges from 0.5 to 0.8, indicating that a significant portion of the organic
matter is biodegradable.
Q6: TSS (Total Suspended Solids) in wastewater refers to:
A. Dissolved organic matter
B. Particles that can be filtered out of the water
C. Settleable solids only
D. Floating debris
2
,Correct Answer: B. Rationale: Total Suspended Solids (TSS) are solid particles that
remain suspended in water and can be removed by filtration. They do not include
dissolved solids.
Q7: What is the typical TSS concentration in domestic wastewater?
A. 10-50 mg/L
B. 100-350 mg/L
C. 500-800 mg/L
D. 1000-2000 mg/L
Correct Answer: B. Rationale: Domestic wastewater typically contains TSS
concentrations ranging from 100-350 mg/L, with 250 mg/L being a common
average value.
Q8: Which of the following best describes the primary treatment process?
A. Biological oxidation of organic matter
B. Physical separation of suspended solids through sedimentation
C. Chemical disinfection of wastewater
D. Nutrient removal through biological processes
Correct Answer: B. Rationale: Primary treatment is primarily a physical process
that uses sedimentation to remove suspended solids and floating material from
wastewater.
Q9: Secondary treatment in wastewater is primarily designed to:
A. Remove large debris and grit
B. Remove dissolved and colloidal organic matter through biological processes
C. Disinfect the effluent
D. Remove heavy metals
Correct Answer: B. Rationale: Secondary treatment uses biological processes
(such as activated sludge or trickling filters) to remove dissolved and colloidal
organic matter that remains after primary treatment.
Q10: The activated sludge process is classified as which type of treatment?
A. Physical treatment
3
, B. Chemical treatment
C. Biological treatment
D. Advanced treatment
Correct Answer: C. Rationale: The activated sludge process is a biological
treatment method that uses microorganisms to break down organic matter in
wastewater.
Q11: Which of the following is NOT a typical component of a wastewater
treatment plant?
A. Bar screens
B. Grit chambers
C. Primary clarifiers
D. Reverse osmosis units
Correct Answer: D. Rationale: Reverse osmosis units are typically used in
advanced treatment or water reclamation facilities, not in conventional
wastewater treatment plants.
Q12: The primary purpose of bar screens in wastewater treatment is:
A. To remove dissolved solids
B. To remove large debris and rags
C. To neutralize pH
D. To add oxygen to the wastewater
Correct Answer: B. Rationale: Bar screens are used to remove large debris such as
sticks, rags, and other coarse materials that could damage downstream
equipment.
Q13: Grit removal in wastewater treatment is important because:
A. Grit adds nutrients to the wastewater
B. Grit can cause excessive wear on pumps and equipment
C. Grit improves the settling characteristics of solids
D. Grit increases BOD levels
4
2026/2027 | QUESTIONS WITH CORRECT ANSWERS |
COMPREHENSIVE PRACTICE TEST ALIGNED WITH TCEQ CLASS
D WASTEWATER OPERATOR CERTIFICATION BLUEPRINT |
PASS GUARANTEED - A+ GRADED
TCEQ WASTEWATER CLASS D LICENSE PREP
SECTION 1: BASIC WASTEWATER TREATMENT CONCEPTS (35 Questions)
Q1: BOD (Biochemical Oxygen Demand) measures which characteristic of
wastewater?
A. The amount of oxygen required to stabilize organic matter
B. The total suspended solids concentration
C. The pH level of the wastewater
D. The chlorine residual
Correct Answer: A. Rationale: BOD measures the amount of oxygen
microorganisms require to decompose organic matter in wastewater over a
specified time (typically 5 days at 20°C), indicating organic strength.
Q2: Which wastewater source typically has the highest strength in terms of BOD
and solids?
A. Residential households
B. Restaurants and food processing
C. Stormwater runoff
D. Cooling water discharge
Correct Answer: B. Rationale: Commercial and industrial sources such as
restaurants and food processing facilities generate wastewater with significantly
higher organic loading (BOD) and solids concentrations compared to typical
domestic wastewater.
Q3: What is the typical BOD concentration range for domestic wastewater?
A. 10-50 mg/L
1
,B. 100-300 mg/L
C. 500-800 mg/L
D. 1000-2000 mg/L
Correct Answer: B. Rationale: Domestic wastewater typically contains BOD
concentrations ranging from 100-300 mg/L, with 200 mg/L being a common
average value.
Q4: COD (Chemical Oxygen Demand) differs from BOD primarily because:
A. COD measures only inorganic compounds
B. COD measures both biodegradable and non-biodegradable organic matter
C. COD is always lower than BOD
D. COD measures oxygen demand over 30 days
Correct Answer: B. Rationale: COD measures the total oxygen equivalent of all
organic matter that can be chemically oxidized, including both biodegradable and
non-biodegradable substances, while BOD only measures biodegradable organic
matter.
Q5: The ratio of BOD to COD in domestic wastewater is typically:
A. 0.1-0.2
B. 0.3-0.5
C. 0.5-0.8
D. 0.9-1.0
Correct Answer: C. Rationale: The BOD/COD ratio for domestic wastewater
typically ranges from 0.5 to 0.8, indicating that a significant portion of the organic
matter is biodegradable.
Q6: TSS (Total Suspended Solids) in wastewater refers to:
A. Dissolved organic matter
B. Particles that can be filtered out of the water
C. Settleable solids only
D. Floating debris
2
,Correct Answer: B. Rationale: Total Suspended Solids (TSS) are solid particles that
remain suspended in water and can be removed by filtration. They do not include
dissolved solids.
Q7: What is the typical TSS concentration in domestic wastewater?
A. 10-50 mg/L
B. 100-350 mg/L
C. 500-800 mg/L
D. 1000-2000 mg/L
Correct Answer: B. Rationale: Domestic wastewater typically contains TSS
concentrations ranging from 100-350 mg/L, with 250 mg/L being a common
average value.
Q8: Which of the following best describes the primary treatment process?
A. Biological oxidation of organic matter
B. Physical separation of suspended solids through sedimentation
C. Chemical disinfection of wastewater
D. Nutrient removal through biological processes
Correct Answer: B. Rationale: Primary treatment is primarily a physical process
that uses sedimentation to remove suspended solids and floating material from
wastewater.
Q9: Secondary treatment in wastewater is primarily designed to:
A. Remove large debris and grit
B. Remove dissolved and colloidal organic matter through biological processes
C. Disinfect the effluent
D. Remove heavy metals
Correct Answer: B. Rationale: Secondary treatment uses biological processes
(such as activated sludge or trickling filters) to remove dissolved and colloidal
organic matter that remains after primary treatment.
Q10: The activated sludge process is classified as which type of treatment?
A. Physical treatment
3
, B. Chemical treatment
C. Biological treatment
D. Advanced treatment
Correct Answer: C. Rationale: The activated sludge process is a biological
treatment method that uses microorganisms to break down organic matter in
wastewater.
Q11: Which of the following is NOT a typical component of a wastewater
treatment plant?
A. Bar screens
B. Grit chambers
C. Primary clarifiers
D. Reverse osmosis units
Correct Answer: D. Rationale: Reverse osmosis units are typically used in
advanced treatment or water reclamation facilities, not in conventional
wastewater treatment plants.
Q12: The primary purpose of bar screens in wastewater treatment is:
A. To remove dissolved solids
B. To remove large debris and rags
C. To neutralize pH
D. To add oxygen to the wastewater
Correct Answer: B. Rationale: Bar screens are used to remove large debris such as
sticks, rags, and other coarse materials that could damage downstream
equipment.
Q13: Grit removal in wastewater treatment is important because:
A. Grit adds nutrients to the wastewater
B. Grit can cause excessive wear on pumps and equipment
C. Grit improves the settling characteristics of solids
D. Grit increases BOD levels
4
