Texas Wastewater Class A
(Updated for 2026) Exam Prep Pack | A+ Questions
190+
& Verified Answers
VERIFIED ANSWERS
Question 1
Seeding of BOD samples is necessary when samples
Correct Answer
(All of the above) have a chlorine residual, have a previously been chlorinated, have been subjected to high
temperatures, contain high or low pH industrial wastes
Rationale:
Seeding of BOD (Biochemical Oxygen Demand) samples is necessary when samples contain substances that inhibit microbial growth, such as
chlorine, which can harm or kill microorganisms. The high or low pH, high temperatures, and previously chlorinated conditions in industrial
wastes can also hinder microbial growth, making seeding essential for accurate BOD results.
Question 2
When is blue-green algae the most dominant on a pond treatment system?
Correct Answer
Summer
Rationale:
The peak growth of blue-green algae is often linked to warm water temperatures, typically above 65°F (18°C), which is most commonly
observed during the summer months. Additionally, increased sunlight and nutrient availability during this time also contribute to the dominance
of blue-green algae in pond treatment systems.
Question 3
A 30-inch diameter wastewater interceptor is observed to be flowing half-full at about two fps. The approximate volume of
wastewater flowing through the pipe is 3.14x1.25 x 1.25 x 2 = 4.9 cfs x 449 = 2,200 gpm
Correct Answer
c. 2,200 gallons per minute
Rationale:
The key concept here is the formula used to calculate the volume of wastewater flowing through the pipe, which involves multiplying the cross-
sectional area of the pipe by the flow rate. The correct application of the formula, specifically using the diameter of the pipe (1.25 feet in this
case) and the flow rate (2 fps), allows for an accurate calculation of the volume in gallons per minute (gpm).
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,Question 4
A one-cylinder reciprocating sludge pump with a 10-inch bore and a 5-inch stroke pumps at a rate of 50 cycles per minute.
How many minutes must the pump be operated to pump 5,000 gallons of sludge? 3.14x0.416 x 0.416 x0.416 x 50 x7.48 =
84.5 gpm 5000 gal = 59,2min 84.5 gpm b. 29
Correct Answer
60 minutes
Rationale:
The key to solving this problem lies in understanding that the pump's rate of operation, 50 cycles per minute, directly corresponds to the
number of minutes it needs to run to pump a certain volume of sludge, as each cycle produces a fixed volume of output. The actual calculation
of gallons per minute (84.5 gpm) is used to find the time it takes to pump 5,000 gallons, but the question's framing, which mentions "50 cycles
per minute," suggests that the answer should be based on the number of minutes it takes to complete those cycles, rather than the calculated
rate.
Question 5
If an existing centrifugal pump motor is replaced with a motor with 25 percent more speed, the motor horsepower required
will increase by 1.25 x 1.25 x 1.25 = 1.95
Correct Answer
95 percent
Rationale:
The motor horsepower required is directly proportional to the cube of its speed, and since the new motor is 25 percent faster, we can calculate
the increase in speed as 1.25 (100% + 25%). This means the horsepower increase is based on the cube of the speed increase, which is
1.25^3, resulting in the required horsepower increase.
Question 6
When must TCEQ be notified about expansions of a treatment facility?
Correct Answer
Before construction
Rationale:
The correct answer is "Before construction" because TCEQ (Texas Commission on Environmental Quality) regulations require that notifications
and permits be obtained prior to commencing any construction or expansion of a treatment facility to ensure compliance with environmental
standards and regulations. This allows TCEQ to evaluate the proposed expansion, assess potential environmental impacts, and issue necessary
permits to protect public health and the environment.
Question 7
In an anaerobic digester, the percentage of methane and carbon dioxide gas content should be
Correct Answer
70% methane, 30% carbon dioxide
Rationale:
Anaerobic digestion is a process where microorganisms break down organic matter in the absence of oxygen, producing biogas, a mixture of
methane and carbon dioxide. The ideal ratio of 70% methane and 30% carbon dioxide is achieved when the digestion process is optimized,
allowing the microorganisms to produce methane as the primary gas product and carbon dioxide as a byproduct.
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,Question 8
The temperature of an anaerobic digester should be maintained at a minimum of
Correct Answer
95° F
Rationale:
Anaerobic digesters rely on thermophilic bacteria to break down organic matter efficiently, which thrive in temperatures between 130°F and
140°F, but temperatures around 95°F would be too low for optimal digestion and potentially allow pathogenic bacteria to survive. A
temperature of around 95°F would allow psychrotrophic and mesophilic bacteria to dominate, slowing down the digestion process and
potentially producing lower quality biogas.
Question 9
What type of wastewater treatment operates in the endogenous bacteria growth phase?
Correct Answer
Extended air
Rationale:
In the endogenous bacteria growth phase of wastewater treatment, the bacteria are primarily utilizing the internal storage products of the
microorganisms themselves, rather than external organic matter, which is characteristic of extended aeration processes. Extended aeration
systems are designed to provide a long aeration time, allowing for the degradation of internal storage products and operation in the
endogenous bacteria growth phase.
Question 10
Why is recirculation needed in a trickling filter?
Correct Answer
Keep the media wet Further reduce BOD All of the above (a, b, and c)
Rationale:
Recirculation in a trickling filter helps maintain a consistent flow of wastewater through the medium, ensuring that the media remains wet and
active in breaking down organic matter, which is essential for efficient biological treatment. By recirculating wastewater, the trickling filter also
reduces the biochemical oxygen demand (BOD) of the effluent by allowing more time for microorganisms to decompose organic pollutants.
Question 11
What type of fire extinguisher would be used on an electrical control panel that has been de-energized?
Correct Answer
Class A Class C (a and d)
Rationale:
A Class A, Class C fire extinguisher combination is suitable for an electrical control panel that has been de-energized because Class A
extinguishers can handle the combustible materials, such as wood or fabric, that may be involved in the initial fire, while Class C extinguishers
can address the electrical component. However, since the electrical panel has been de-energized, the primary risk is no longer the electrical
component itself, making Class C less important, but still necessary for overall protection against electrical fires.
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, Question 12
Disinfection with chlorine is the most effective at a pH of
Correct Answer
6.0
Rationale:
Chlorine is a strong disinfectant, but its effectiveness decreases in alkaline environments, reaching its peak effectiveness at a pH of around 6.0
due to the optimal balance between hydrogen ion activity and the formation of hypochlorous acid, the primary disinfecting agent. At this pH,
the high concentration of hydrogen ions allows for the efficient conversion of free chlorine into hypochlorous acid, which is highly lethal to
microorganisms.
Question 13
The biomass on a normal functioning RBC has what appearance?
Correct Answer
Grey to brown and 0.05 to 0.1 inch thick
Rationale:
The description "Grey to brown and 0.05 to 0.1 inch thick" refers to the physical appearance and thickness of the RBC (Root Cap) biomass,
specifically the root cap of a plant. This characteristic is a result of the root cap's unique composition and function, which protects the root
from physical damage and facilitates its growth into the soil.
Question 14
The sludge from a primary clarifier should percent solids?
Correct Answer
4% to 6%
Rationale:
The sludge from a primary clarifier is typically expected to have a percent solids range of 4% to 6% because this concentration allows for
efficient thickening and settling in the subsequent secondary treatment processes, such as digestion or dewatering. Maintaining a solids
concentration within this range enables optimal treatment efficiency and minimizes the risk of solids accumulation or clogging in downstream
equipment.
Question 15
What is eutrophication in a pond system?
Correct Answer
Enrichment with nitrogen and phosphorous Causes algae blooms (b and c)
Rationale:
Eutrophication in a pond system occurs when excessive amounts of nitrogen and phosphorus, often from fertilizers, sewage, or agricultural
runoff, enter the water, causing an overabundance of algae to grow, which in turn depletes the oxygen in the water. This imbalance in the
ecosystem ultimately affects the pond's biodiversity, leading to the degradation of water quality.
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(Updated for 2026) Exam Prep Pack | A+ Questions
190+
& Verified Answers
VERIFIED ANSWERS
Question 1
Seeding of BOD samples is necessary when samples
Correct Answer
(All of the above) have a chlorine residual, have a previously been chlorinated, have been subjected to high
temperatures, contain high or low pH industrial wastes
Rationale:
Seeding of BOD (Biochemical Oxygen Demand) samples is necessary when samples contain substances that inhibit microbial growth, such as
chlorine, which can harm or kill microorganisms. The high or low pH, high temperatures, and previously chlorinated conditions in industrial
wastes can also hinder microbial growth, making seeding essential for accurate BOD results.
Question 2
When is blue-green algae the most dominant on a pond treatment system?
Correct Answer
Summer
Rationale:
The peak growth of blue-green algae is often linked to warm water temperatures, typically above 65°F (18°C), which is most commonly
observed during the summer months. Additionally, increased sunlight and nutrient availability during this time also contribute to the dominance
of blue-green algae in pond treatment systems.
Question 3
A 30-inch diameter wastewater interceptor is observed to be flowing half-full at about two fps. The approximate volume of
wastewater flowing through the pipe is 3.14x1.25 x 1.25 x 2 = 4.9 cfs x 449 = 2,200 gpm
Correct Answer
c. 2,200 gallons per minute
Rationale:
The key concept here is the formula used to calculate the volume of wastewater flowing through the pipe, which involves multiplying the cross-
sectional area of the pipe by the flow rate. The correct application of the formula, specifically using the diameter of the pipe (1.25 feet in this
case) and the flow rate (2 fps), allows for an accurate calculation of the volume in gallons per minute (gpm).
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,Question 4
A one-cylinder reciprocating sludge pump with a 10-inch bore and a 5-inch stroke pumps at a rate of 50 cycles per minute.
How many minutes must the pump be operated to pump 5,000 gallons of sludge? 3.14x0.416 x 0.416 x0.416 x 50 x7.48 =
84.5 gpm 5000 gal = 59,2min 84.5 gpm b. 29
Correct Answer
60 minutes
Rationale:
The key to solving this problem lies in understanding that the pump's rate of operation, 50 cycles per minute, directly corresponds to the
number of minutes it needs to run to pump a certain volume of sludge, as each cycle produces a fixed volume of output. The actual calculation
of gallons per minute (84.5 gpm) is used to find the time it takes to pump 5,000 gallons, but the question's framing, which mentions "50 cycles
per minute," suggests that the answer should be based on the number of minutes it takes to complete those cycles, rather than the calculated
rate.
Question 5
If an existing centrifugal pump motor is replaced with a motor with 25 percent more speed, the motor horsepower required
will increase by 1.25 x 1.25 x 1.25 = 1.95
Correct Answer
95 percent
Rationale:
The motor horsepower required is directly proportional to the cube of its speed, and since the new motor is 25 percent faster, we can calculate
the increase in speed as 1.25 (100% + 25%). This means the horsepower increase is based on the cube of the speed increase, which is
1.25^3, resulting in the required horsepower increase.
Question 6
When must TCEQ be notified about expansions of a treatment facility?
Correct Answer
Before construction
Rationale:
The correct answer is "Before construction" because TCEQ (Texas Commission on Environmental Quality) regulations require that notifications
and permits be obtained prior to commencing any construction or expansion of a treatment facility to ensure compliance with environmental
standards and regulations. This allows TCEQ to evaluate the proposed expansion, assess potential environmental impacts, and issue necessary
permits to protect public health and the environment.
Question 7
In an anaerobic digester, the percentage of methane and carbon dioxide gas content should be
Correct Answer
70% methane, 30% carbon dioxide
Rationale:
Anaerobic digestion is a process where microorganisms break down organic matter in the absence of oxygen, producing biogas, a mixture of
methane and carbon dioxide. The ideal ratio of 70% methane and 30% carbon dioxide is achieved when the digestion process is optimized,
allowing the microorganisms to produce methane as the primary gas product and carbon dioxide as a byproduct.
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,Question 8
The temperature of an anaerobic digester should be maintained at a minimum of
Correct Answer
95° F
Rationale:
Anaerobic digesters rely on thermophilic bacteria to break down organic matter efficiently, which thrive in temperatures between 130°F and
140°F, but temperatures around 95°F would be too low for optimal digestion and potentially allow pathogenic bacteria to survive. A
temperature of around 95°F would allow psychrotrophic and mesophilic bacteria to dominate, slowing down the digestion process and
potentially producing lower quality biogas.
Question 9
What type of wastewater treatment operates in the endogenous bacteria growth phase?
Correct Answer
Extended air
Rationale:
In the endogenous bacteria growth phase of wastewater treatment, the bacteria are primarily utilizing the internal storage products of the
microorganisms themselves, rather than external organic matter, which is characteristic of extended aeration processes. Extended aeration
systems are designed to provide a long aeration time, allowing for the degradation of internal storage products and operation in the
endogenous bacteria growth phase.
Question 10
Why is recirculation needed in a trickling filter?
Correct Answer
Keep the media wet Further reduce BOD All of the above (a, b, and c)
Rationale:
Recirculation in a trickling filter helps maintain a consistent flow of wastewater through the medium, ensuring that the media remains wet and
active in breaking down organic matter, which is essential for efficient biological treatment. By recirculating wastewater, the trickling filter also
reduces the biochemical oxygen demand (BOD) of the effluent by allowing more time for microorganisms to decompose organic pollutants.
Question 11
What type of fire extinguisher would be used on an electrical control panel that has been de-energized?
Correct Answer
Class A Class C (a and d)
Rationale:
A Class A, Class C fire extinguisher combination is suitable for an electrical control panel that has been de-energized because Class A
extinguishers can handle the combustible materials, such as wood or fabric, that may be involved in the initial fire, while Class C extinguishers
can address the electrical component. However, since the electrical panel has been de-energized, the primary risk is no longer the electrical
component itself, making Class C less important, but still necessary for overall protection against electrical fires.
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, Question 12
Disinfection with chlorine is the most effective at a pH of
Correct Answer
6.0
Rationale:
Chlorine is a strong disinfectant, but its effectiveness decreases in alkaline environments, reaching its peak effectiveness at a pH of around 6.0
due to the optimal balance between hydrogen ion activity and the formation of hypochlorous acid, the primary disinfecting agent. At this pH,
the high concentration of hydrogen ions allows for the efficient conversion of free chlorine into hypochlorous acid, which is highly lethal to
microorganisms.
Question 13
The biomass on a normal functioning RBC has what appearance?
Correct Answer
Grey to brown and 0.05 to 0.1 inch thick
Rationale:
The description "Grey to brown and 0.05 to 0.1 inch thick" refers to the physical appearance and thickness of the RBC (Root Cap) biomass,
specifically the root cap of a plant. This characteristic is a result of the root cap's unique composition and function, which protects the root
from physical damage and facilitates its growth into the soil.
Question 14
The sludge from a primary clarifier should percent solids?
Correct Answer
4% to 6%
Rationale:
The sludge from a primary clarifier is typically expected to have a percent solids range of 4% to 6% because this concentration allows for
efficient thickening and settling in the subsequent secondary treatment processes, such as digestion or dewatering. Maintaining a solids
concentration within this range enables optimal treatment efficiency and minimizes the risk of solids accumulation or clogging in downstream
equipment.
Question 15
What is eutrophication in a pond system?
Correct Answer
Enrichment with nitrogen and phosphorous Causes algae blooms (b and c)
Rationale:
Eutrophication in a pond system occurs when excessive amounts of nitrogen and phosphorus, often from fertilizers, sewage, or agricultural
runoff, enter the water, causing an overabundance of algae to grow, which in turn depletes the oxygen in the water. This imbalance in the
ecosystem ultimately affects the pond's biodiversity, leading to the degradation of water quality.
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