Texas Wastewater Class D – Practice Exam
Questions with Complete Solutions.
DOMAIN 1: TREATMENT OBJECTIVES & FUNDAMENTALS (15 Questions)
1. Which of the following best defines groundwater under the direct influence of surface
water (GWUDI)?
A. Water from an aquifer that has never been exposed to the surface.
B. Groundwater that flows directly into a wastewater treatment plant collection system.
C. Water from a spring or well that is significantly recharged by surface water and requires
filtration.
D. Surface water collected in a subsurface reservoir.
[CORRECT] C. Water from a spring or well that is significantly recharged by surface water and
requires filtration.
Rationale: Under TCEQ and EPA definitions, GWUDI refers to sources that are not
underground rivers but are influenced by surface water, carrying risks of pathogens (like
Giardia or Cryptosporidium) typically only found in surface water, thus requiring more
stringent treatment similar to surface water systems.
2. In the context of wastewater sources, what distinguishes "sewage" from "septage"?
A. Sewage is industrial waste only; septage is domestic waste.
B. Sewage is domestic wastewater from a community system; septage is the liquid and
pumped material from septic tanks or portable toilets.
C. Septage is treated effluent; sewage is raw influent.
D. There is no difference; the terms are interchangeable.
[CORRECT] B. Sewage is domestic wastewater from a community system; septage is the liquid
and pumped material from septic tanks or portable toilets.
Rationale: TCEQ defines sewage as the water-carried human wastes from residences,
buildings, etc. Septage is specifically the specific mixture of scum, sludge, liquid, and human
waste that is pumped out of septic tanks, cesspools, or similar holding tanks, often requiring
different handling due to higher strength.
,3. What is the primary purpose of bar screens in the preliminary treatment process?
A. To settle out inorganic solids like sand and gravel.
B. To remove large floating debris (rags, sticks, plastics) that could damage pumps.
C. To dissolve organic matter before aeration.
D. To disinfect the influent flow.
[CORRECT] B. To remove large floating debris (rags, sticks, plastics) that could damage pumps.
Rationale: Bar screens are the first line of defense. They protect downstream equipment
(pumps, valves, comminutors) from clogging or damage by removing large, coarse solids.
4. Why is grit removal critical in wastewater treatment plants?
A. Grit is a major source of BOD that must be removed to save money on aeration.
B. Grit accumulates in tanks and pipelines, causing excessive wear on mechanical equipment
and taking up volume in digesters.
C. Grit neutralizes the pH of the wastewater.
D. Grit facilitates the growth of nitrifying bacteria.
[CORRECT] B. Grit accumulates in tanks and pipelines, causing excessive wear on mechanical
equipment and taking up volume in digesters.
Rationale: Grit (sand, gravel, cinders) is heavy and abrasive. If not removed in the grit
channel, it will settle in aeration basins and digestors, taking up valuable volume and causing
abrasion on pumps and aerators.
5. Which chemical is commonly added in the primary treatment stage to aid in phosphorus
removal or odor control?
A. Chlorine
B. Ferric chloride or Alum
C. Fluoride
D. Oxygen gas
,[CORRECT] B. Ferric chloride or Alum
Rationale: While primary treatment is physical, chemicals like ferric chloride or alum are often
added to precipitate phosphorus or control hydrogen sulfide odors before the water moves to
secondary treatment.
6. What does the acronym NPDES stand for?
A. National Pollution Discharge Elimination System
B. National Permitting of Drinking Effluent Standards
C. New Protocol for Disinfection of Effluent Streams
D. National Primary Drinking Water Enforcement System
[CORRECT] A. National Pollution Discharge Elimination System
Rationale: The NPDES is the permitting program under the Clean Water Act that controls
water pollution by regulating point sources that discharge pollutants into waters of the United
States. In Texas, this is administered by the TCEQ.
7. Who is ultimately responsible for the operation of a wastewater treatment plant and
ensuring compliance with the NPDES permit?
A. The shift supervisor
B. The Designated Responsible Operator (DRO)
C. The maintenance contractor
D. The local mayor
[CORRECT] B. The Designated Responsible Operator (DRO)
Rationale: TCEQ regulations require that every permitted facility have a Designated
Responsible Operator whose license is of the same or higher class than the facility. The DRO is
legally accountable for compliance.
8. How often must a Texas wastewater operator renew their license?
A. Every year
, B. Every 2 years
C. Every 3 years
D. Every 5 years
[CORRECT] C. Every 3 years
Rationale: TCEQ operator licenses expire on the anniversary of issuance, typically every 3
years. Operators must complete the required Continuing Education Units (CEUs) and pay a
renewal fee to maintain licensure.
9. How many Continuing Education Units (CEUs) are required to renew a Class D wastewater
license in Texas?
A. 8 hours
B. 12 hours
C. 24 hours
D. 30 hours
[CORRECT] C. 24 hours
Rationale: Class D operators must complete 24 hours of TCEQ-approved CEUs during the 3-
year licensing period to renew their license.
10. Under 30 TAC Chapter 317, what is the minimum record retention period for daily
operating data for a wastewater treatment plant?
A. 3 years
B. 5 years
C. 10 years
D. 15 years
[CORRECT] B. 5 years
Rationale: TCEQ regulations generally require that operating records, including disinfection
residual and flow data, be kept for a minimum of 5 years.
Questions with Complete Solutions.
DOMAIN 1: TREATMENT OBJECTIVES & FUNDAMENTALS (15 Questions)
1. Which of the following best defines groundwater under the direct influence of surface
water (GWUDI)?
A. Water from an aquifer that has never been exposed to the surface.
B. Groundwater that flows directly into a wastewater treatment plant collection system.
C. Water from a spring or well that is significantly recharged by surface water and requires
filtration.
D. Surface water collected in a subsurface reservoir.
[CORRECT] C. Water from a spring or well that is significantly recharged by surface water and
requires filtration.
Rationale: Under TCEQ and EPA definitions, GWUDI refers to sources that are not
underground rivers but are influenced by surface water, carrying risks of pathogens (like
Giardia or Cryptosporidium) typically only found in surface water, thus requiring more
stringent treatment similar to surface water systems.
2. In the context of wastewater sources, what distinguishes "sewage" from "septage"?
A. Sewage is industrial waste only; septage is domestic waste.
B. Sewage is domestic wastewater from a community system; septage is the liquid and
pumped material from septic tanks or portable toilets.
C. Septage is treated effluent; sewage is raw influent.
D. There is no difference; the terms are interchangeable.
[CORRECT] B. Sewage is domestic wastewater from a community system; septage is the liquid
and pumped material from septic tanks or portable toilets.
Rationale: TCEQ defines sewage as the water-carried human wastes from residences,
buildings, etc. Septage is specifically the specific mixture of scum, sludge, liquid, and human
waste that is pumped out of septic tanks, cesspools, or similar holding tanks, often requiring
different handling due to higher strength.
,3. What is the primary purpose of bar screens in the preliminary treatment process?
A. To settle out inorganic solids like sand and gravel.
B. To remove large floating debris (rags, sticks, plastics) that could damage pumps.
C. To dissolve organic matter before aeration.
D. To disinfect the influent flow.
[CORRECT] B. To remove large floating debris (rags, sticks, plastics) that could damage pumps.
Rationale: Bar screens are the first line of defense. They protect downstream equipment
(pumps, valves, comminutors) from clogging or damage by removing large, coarse solids.
4. Why is grit removal critical in wastewater treatment plants?
A. Grit is a major source of BOD that must be removed to save money on aeration.
B. Grit accumulates in tanks and pipelines, causing excessive wear on mechanical equipment
and taking up volume in digesters.
C. Grit neutralizes the pH of the wastewater.
D. Grit facilitates the growth of nitrifying bacteria.
[CORRECT] B. Grit accumulates in tanks and pipelines, causing excessive wear on mechanical
equipment and taking up volume in digesters.
Rationale: Grit (sand, gravel, cinders) is heavy and abrasive. If not removed in the grit
channel, it will settle in aeration basins and digestors, taking up valuable volume and causing
abrasion on pumps and aerators.
5. Which chemical is commonly added in the primary treatment stage to aid in phosphorus
removal or odor control?
A. Chlorine
B. Ferric chloride or Alum
C. Fluoride
D. Oxygen gas
,[CORRECT] B. Ferric chloride or Alum
Rationale: While primary treatment is physical, chemicals like ferric chloride or alum are often
added to precipitate phosphorus or control hydrogen sulfide odors before the water moves to
secondary treatment.
6. What does the acronym NPDES stand for?
A. National Pollution Discharge Elimination System
B. National Permitting of Drinking Effluent Standards
C. New Protocol for Disinfection of Effluent Streams
D. National Primary Drinking Water Enforcement System
[CORRECT] A. National Pollution Discharge Elimination System
Rationale: The NPDES is the permitting program under the Clean Water Act that controls
water pollution by regulating point sources that discharge pollutants into waters of the United
States. In Texas, this is administered by the TCEQ.
7. Who is ultimately responsible for the operation of a wastewater treatment plant and
ensuring compliance with the NPDES permit?
A. The shift supervisor
B. The Designated Responsible Operator (DRO)
C. The maintenance contractor
D. The local mayor
[CORRECT] B. The Designated Responsible Operator (DRO)
Rationale: TCEQ regulations require that every permitted facility have a Designated
Responsible Operator whose license is of the same or higher class than the facility. The DRO is
legally accountable for compliance.
8. How often must a Texas wastewater operator renew their license?
A. Every year
, B. Every 2 years
C. Every 3 years
D. Every 5 years
[CORRECT] C. Every 3 years
Rationale: TCEQ operator licenses expire on the anniversary of issuance, typically every 3
years. Operators must complete the required Continuing Education Units (CEUs) and pay a
renewal fee to maintain licensure.
9. How many Continuing Education Units (CEUs) are required to renew a Class D wastewater
license in Texas?
A. 8 hours
B. 12 hours
C. 24 hours
D. 30 hours
[CORRECT] C. 24 hours
Rationale: Class D operators must complete 24 hours of TCEQ-approved CEUs during the 3-
year licensing period to renew their license.
10. Under 30 TAC Chapter 317, what is the minimum record retention period for daily
operating data for a wastewater treatment plant?
A. 3 years
B. 5 years
C. 10 years
D. 15 years
[CORRECT] B. 5 years
Rationale: TCEQ regulations generally require that operating records, including disinfection
residual and flow data, be kept for a minimum of 5 years.
