TEXAS WASTEWATER OPERATOR LICENSE VERSION B LATEST EXAM QUESTIONS
AND SOLUTIONS - VERIFIED ANSWERS 2026/2027
TCEQ Wastewater Operator Certification
1. What is the primary purpose of wastewater treatment?
Answer: To remove pollutants from wastewater before it is discharged into
the environment, protecting public health and water quality.
2. What does BOD stand for in wastewater treatment?
Answer: Biochemical Oxygen Demand – a measure of the amount of oxygen
required by microorganisms to decompose organic matter in water.
3. What does COD stand for?
Answer: Chemical Oxygen Demand – the amount of oxygen needed to
chemically oxidize organic and inorganic compounds in water.
4. What is the difference between BOD5 and ultimate BOD?
Answer: BOD5 is the oxygen demand measured over 5 days at 20°C;
ultimate BOD is the total oxygen demand if all biodegradable material were
completely oxidized.
5. What are the three main stages of conventional wastewater treatment?
Answer: Primary (physical settling), secondary (biological treatment), and
tertiary (advanced treatment/polishing).
6. What is meant by 'effluent' in wastewater treatment?
Answer: Effluent is the treated wastewater that exits a treatment plant and is
discharged into a receiving water body or reused.
7. Define 'influent' in the context of wastewater treatment.
Answer: Influent is the raw, untreated wastewater entering a treatment plant.
8. What is the purpose of preliminary treatment in wastewater plants?
Answer: To remove large solids, grit, and debris that could damage
equipment or impair downstream processes.
9. What is a bar screen used for in wastewater treatment?
, Answer: To remove large floating and suspended solids (rags, sticks,
plastics) from incoming wastewater before further treatment.
10. What is the purpose of a grit chamber?
Answer: To remove sand, gravel, and heavy inorganic particles that could
damage pumps and equipment or accumulate in tanks.
11. What is TSS in wastewater?
Answer: Total Suspended Solids – particles that can be removed by filtration;
a key measure of wastewater and effluent quality.
12. What is TDS in wastewater?
Answer: Total Dissolved Solids – the total concentration of dissolved
substances in water that pass through a filter.
13. What does 'mg/L' represent in water quality measurements?
Answer: Milligrams per liter – equivalent to parts per million (ppm) for dilute
aqueous solutions.
14. What is the purpose of a primary clarifier?
Answer: To allow settleable solids to settle to the bottom (as sludge) and
floatable materials to rise to the surface, reducing BOD and TSS.
15. What percentage of BOD removal is typical for primary treatment?
Answer: Primary treatment typically removes 25–40% of BOD and 50–70% of
TSS.
16. What is activated sludge?
Answer: A biological treatment process using a mass of microorganisms
(floc) to biologically oxidize organic matter in aerated tanks.
17. What is the MLSS in an activated sludge system?
Answer: Mixed Liquor Suspended Solids – the concentration of suspended
solids (biomass) in the aeration tank, typically 1,500–4,000 mg/L.
18. What is MLVSS?
Answer: Mixed Liquor Volatile Suspended Solids – the organic fraction of
MLSS that represents active biomass; typically 70–80% of MLSS.
19. What is the F/M ratio?
Answer: Food-to-Microorganism ratio – the amount of food (BOD) supplied to
the biomass; used to control the activated sludge process.
20. What is SRT (Sludge Retention Time)?
, Answer: The average time that activated sludge (microorganisms) remain in
the treatment system; also called mean cell residence time (MCRT).
21. What is the purpose of the return activated sludge (RAS)?
Answer: To return settled sludge from the secondary clarifier back to the
aeration tank to maintain adequate biomass concentration.
22. What is waste activated sludge (WAS)?
Answer: Excess activated sludge removed from the system to maintain the
desired SRT and MLSS levels.
23. What is the sludge volume index (SVI)?
Answer: A measure of the settleability of activated sludge; calculated as the
volume occupied by 1 gram of sludge after 30 minutes of settling (mL/g).
24. What SVI value indicates good settling sludge?
Answer: An SVI of 80–150 mL/g indicates well-settling sludge; values above
200 suggest bulking problems.
25. What is secondary clarification?
Answer: The settling process after biological treatment that separates treated
water from the biological sludge (biomass).
26. What is a trickling filter?
Answer: A fixed-film biological treatment process where wastewater is
distributed over a media (rock, plastic) on which a microbial biofilm grows.
27. What is hydraulic loading rate?
Answer: The volume of flow applied to a treatment unit per unit area or
volume per unit time (e.g., gallons/day/ft²).
28. What is organic loading rate?
Answer: The mass of BOD or COD applied to a treatment unit per unit
volume or area per unit time (e.g., lbs BOD/day/1,000 ft³).
29. What are nitrification and denitrification?
Answer: Nitrification converts ammonia to nitrate (aerobic); denitrification
converts nitrate to nitrogen gas (anoxic), together removing nitrogen from
wastewater.
30. What organisms are responsible for nitrification?
Answer: Autotrophic bacteria, primarily Nitrosomonas (ammonia→nitrite) and
Nitrobacter (nitrite→nitrate).
, Section 2: Texas TCEQ Regulations
31. What state agency regulates wastewater treatment in Texas?
Answer: The Texas Commission on Environmental Quality (TCEQ).
32. What is a TPDES permit?
Answer: Texas Pollutant Discharge Elimination System permit – required for
facilities that discharge wastewater to surface waters in Texas.
33. How many classes of wastewater operator licenses are there in Texas?
Answer: There are four classes: Class I (lowest), Class II, Class III, and Class
IV (highest).
34. What is a Class A wastewater license in Texas?
Answer: Texas does not use Class A; it uses Classes I–IV, with Class IV
being the highest for wastewater treatment operators.
35. What is the minimum treatment flow for a Class IV wastewater license?
Answer: A Class IV facility treats flows greater than 1 MGD (million gallons
per day) and uses complex treatment processes.
36. How long must an operator have experience before applying for a Class
IV wastewater license?
Answer: Generally four years of progressively responsible experience in
wastewater treatment operations is required for Class IV.
37. What is a OSSF in Texas?
Answer: On-Site Sewage Facility – a system that treats and disposes of
wastewater on the property where it is generated (e.g., septic systems).
38. What is the Texas Water Code primary authority for wastewater
regulation?
Answer: Chapter 26 of the Texas Water Code governs the prevention and
abatement of water pollution in Texas.
39. What is an NOV in the context of TCEQ enforcement?
Answer: Notice of Violation – a formal notification from TCEQ that a regulated
entity has violated a permit, rule, or law.
40. What is the purpose of a Discharge Monitoring Report (DMR)?
Answer: To report effluent quality data required by a TPDES permit to the
TCEQ, documenting compliance with permit limits.
41. How often must DMRs typically be submitted to TCEQ?
AND SOLUTIONS - VERIFIED ANSWERS 2026/2027
TCEQ Wastewater Operator Certification
1. What is the primary purpose of wastewater treatment?
Answer: To remove pollutants from wastewater before it is discharged into
the environment, protecting public health and water quality.
2. What does BOD stand for in wastewater treatment?
Answer: Biochemical Oxygen Demand – a measure of the amount of oxygen
required by microorganisms to decompose organic matter in water.
3. What does COD stand for?
Answer: Chemical Oxygen Demand – the amount of oxygen needed to
chemically oxidize organic and inorganic compounds in water.
4. What is the difference between BOD5 and ultimate BOD?
Answer: BOD5 is the oxygen demand measured over 5 days at 20°C;
ultimate BOD is the total oxygen demand if all biodegradable material were
completely oxidized.
5. What are the three main stages of conventional wastewater treatment?
Answer: Primary (physical settling), secondary (biological treatment), and
tertiary (advanced treatment/polishing).
6. What is meant by 'effluent' in wastewater treatment?
Answer: Effluent is the treated wastewater that exits a treatment plant and is
discharged into a receiving water body or reused.
7. Define 'influent' in the context of wastewater treatment.
Answer: Influent is the raw, untreated wastewater entering a treatment plant.
8. What is the purpose of preliminary treatment in wastewater plants?
Answer: To remove large solids, grit, and debris that could damage
equipment or impair downstream processes.
9. What is a bar screen used for in wastewater treatment?
, Answer: To remove large floating and suspended solids (rags, sticks,
plastics) from incoming wastewater before further treatment.
10. What is the purpose of a grit chamber?
Answer: To remove sand, gravel, and heavy inorganic particles that could
damage pumps and equipment or accumulate in tanks.
11. What is TSS in wastewater?
Answer: Total Suspended Solids – particles that can be removed by filtration;
a key measure of wastewater and effluent quality.
12. What is TDS in wastewater?
Answer: Total Dissolved Solids – the total concentration of dissolved
substances in water that pass through a filter.
13. What does 'mg/L' represent in water quality measurements?
Answer: Milligrams per liter – equivalent to parts per million (ppm) for dilute
aqueous solutions.
14. What is the purpose of a primary clarifier?
Answer: To allow settleable solids to settle to the bottom (as sludge) and
floatable materials to rise to the surface, reducing BOD and TSS.
15. What percentage of BOD removal is typical for primary treatment?
Answer: Primary treatment typically removes 25–40% of BOD and 50–70% of
TSS.
16. What is activated sludge?
Answer: A biological treatment process using a mass of microorganisms
(floc) to biologically oxidize organic matter in aerated tanks.
17. What is the MLSS in an activated sludge system?
Answer: Mixed Liquor Suspended Solids – the concentration of suspended
solids (biomass) in the aeration tank, typically 1,500–4,000 mg/L.
18. What is MLVSS?
Answer: Mixed Liquor Volatile Suspended Solids – the organic fraction of
MLSS that represents active biomass; typically 70–80% of MLSS.
19. What is the F/M ratio?
Answer: Food-to-Microorganism ratio – the amount of food (BOD) supplied to
the biomass; used to control the activated sludge process.
20. What is SRT (Sludge Retention Time)?
, Answer: The average time that activated sludge (microorganisms) remain in
the treatment system; also called mean cell residence time (MCRT).
21. What is the purpose of the return activated sludge (RAS)?
Answer: To return settled sludge from the secondary clarifier back to the
aeration tank to maintain adequate biomass concentration.
22. What is waste activated sludge (WAS)?
Answer: Excess activated sludge removed from the system to maintain the
desired SRT and MLSS levels.
23. What is the sludge volume index (SVI)?
Answer: A measure of the settleability of activated sludge; calculated as the
volume occupied by 1 gram of sludge after 30 minutes of settling (mL/g).
24. What SVI value indicates good settling sludge?
Answer: An SVI of 80–150 mL/g indicates well-settling sludge; values above
200 suggest bulking problems.
25. What is secondary clarification?
Answer: The settling process after biological treatment that separates treated
water from the biological sludge (biomass).
26. What is a trickling filter?
Answer: A fixed-film biological treatment process where wastewater is
distributed over a media (rock, plastic) on which a microbial biofilm grows.
27. What is hydraulic loading rate?
Answer: The volume of flow applied to a treatment unit per unit area or
volume per unit time (e.g., gallons/day/ft²).
28. What is organic loading rate?
Answer: The mass of BOD or COD applied to a treatment unit per unit
volume or area per unit time (e.g., lbs BOD/day/1,000 ft³).
29. What are nitrification and denitrification?
Answer: Nitrification converts ammonia to nitrate (aerobic); denitrification
converts nitrate to nitrogen gas (anoxic), together removing nitrogen from
wastewater.
30. What organisms are responsible for nitrification?
Answer: Autotrophic bacteria, primarily Nitrosomonas (ammonia→nitrite) and
Nitrobacter (nitrite→nitrate).
, Section 2: Texas TCEQ Regulations
31. What state agency regulates wastewater treatment in Texas?
Answer: The Texas Commission on Environmental Quality (TCEQ).
32. What is a TPDES permit?
Answer: Texas Pollutant Discharge Elimination System permit – required for
facilities that discharge wastewater to surface waters in Texas.
33. How many classes of wastewater operator licenses are there in Texas?
Answer: There are four classes: Class I (lowest), Class II, Class III, and Class
IV (highest).
34. What is a Class A wastewater license in Texas?
Answer: Texas does not use Class A; it uses Classes I–IV, with Class IV
being the highest for wastewater treatment operators.
35. What is the minimum treatment flow for a Class IV wastewater license?
Answer: A Class IV facility treats flows greater than 1 MGD (million gallons
per day) and uses complex treatment processes.
36. How long must an operator have experience before applying for a Class
IV wastewater license?
Answer: Generally four years of progressively responsible experience in
wastewater treatment operations is required for Class IV.
37. What is a OSSF in Texas?
Answer: On-Site Sewage Facility – a system that treats and disposes of
wastewater on the property where it is generated (e.g., septic systems).
38. What is the Texas Water Code primary authority for wastewater
regulation?
Answer: Chapter 26 of the Texas Water Code governs the prevention and
abatement of water pollution in Texas.
39. What is an NOV in the context of TCEQ enforcement?
Answer: Notice of Violation – a formal notification from TCEQ that a regulated
entity has violated a permit, rule, or law.
40. What is the purpose of a Discharge Monitoring Report (DMR)?
Answer: To report effluent quality data required by a TPDES permit to the
TCEQ, documenting compliance with permit limits.
41. How often must DMRs typically be submitted to TCEQ?
